Next Article in Journal
Ultrafiltration of Car Wash Wastewater: Pilot-Scale Studies
Next Article in Special Issue
Optimizing UV Photodegradation of Chlorothalonil with Reflective Materials (Silver-White Aluminium Foil)
Previous Article in Journal
Groundwater Recharge Evaluation Using Stable Isotopes and the NETPATH Model in Al-Madinah Al-Munawarah Province, Saudi Arabia
Previous Article in Special Issue
Modelling the Fate of Linear Alkylbenzene Sulfonate in Agricultural Soil Columns during Inflow of Surfactant Pulses from Domestic Wastewaters
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Water
Volume 17
Issue 2
10.3390/w17020212
water-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Advanced Oxidation Processes and Adsorption Technologies for the Removal of Organic Azo Compounds: UV, H2O2, and GAC

by
M. Ferre
1,*,
M. J. Moya-Llamas
2,
E. Dominguez
1,
Nuria Ortuño
3 and
D. Prats
3
1
University Institute of Water and Environmental Sciences, University of Alicante, 03690 Alicante, Spain
2
Department of Civil Engineering, Member of the University Institute of Water and Environmental Sciences, University of Alicante, 03690 Alicante, Spain
3
Department of Chemical Engineering, Member of the University Institute of Water and Environmental Sciences, University of Alicante, 03690 Alicante, Spain
*
Author to whom correspondence should be addressed.
Water 2025, 17(2), 212; https://doi.org/10.3390/w17020212
Submission received: 19 November 2024 / Revised: 23 December 2024 / Accepted: 8 January 2025 / Published: 14 January 2025
(This article belongs to the Special Issue Physical–Chemical Wastewater Treatment Technologies)
Browse Figures
Versions Notes

Abstract

:
This research focuses on the removal of emerging contaminants (CEC) present in synthetic aqueous matrices. Azole compounds were selected as CEC of interest due to their persistence and toxicity, particularly the triazole and oxazole groups. These compounds are also trace contaminants listed in the proposed revision of Directive 91/271/EEC on urban wastewater treatment and the 3rd European Union Observation List (Implementing Decision EU 2020/116), highlighting their regulatory importance. The draft Directive includes the implementation of quaternary treatments to achieve the highest possible removal rates of micropollutants. Among the technologies used on a large scale are some advanced oxidation processes (AOP), often combined with adsorption on activated carbon (AC). Laboratory-scale pilot plants have been designed and operated in this research, including UV photolysis and oxidation with H2O2 and adsorption with GAC. The results demonstrate that UV photolysis is able to remove all the selected CECs except fluconazole, reaching eliminations higher than 86% at high doses of 31.000 J/m2. Treatment by H2O2 achieved removals of 4 to 55%, proving to be ineffective in the degradation of persistent compounds when acting as a single technology. Adsorption by AC is improved with longer contact times, reaching removals above 80% for benzotriazole and methyl benzotriazole at short contact times, followed by sulfamethoxazole and tebuconazole. Fluconazole had a mean adsorption capacity at low contact times, while metconazole and penconazole showed low adsorption capacities.

1. Introduction

The use of chemical compounds is continuously increasing due to the high demand for products for industries, personal care, disease treatment, or pest control. Approximately 350.000 chemical products and mixtures are available on the global market [1,2]. After their use, many of these compounds, or their degradation products, end up being released into the environment, leading to health issues and damage to ecosystems [3,4]. Generally, compounds whose presence in the environment raises growing concern due to their potential negative impacts are referred to as contaminants of emerging concern (CEC). Despite their presence in water bodies being at concentrations of µg/L or ng/L, they can bioaccumulate and cause toxicity and ecotoxicity problems, affecting flora, fauna, and humans. Contaminants of emerging concern enter different water bodies and masses of water due to their discharge through domestic, agricultural, and industrial wastewater, being present in groundwater, surface water, urban wastewater, drinking water, and sludge from water treatment. This is reflected in the Proposal for a Directive of the European Parliament and of the Council concerning urban wastewater treatment, which establishes a quaternary treatment to remove more than 80% of a selected set of CEC [5].
Figure 1 shows the different routes of entry of CEC into water bodies and how they can contaminate drinking water.
Urban wastewater is a significant source of CEC due to its origin from household, hospital, and service discharges, as illustrated in the diagram in Figure 1. Contaminants such as pharmaceuticals, personal care products, biocides, plasticizers, and flame retardants are frequently detected in these waters [7,8,9]. As a consequence of their great diversity, the chemical structure of CEC present in urban wastewater is highly variable.
Azole compounds are antifungal compounds that share the characteristic of having a free imidazole or triazole ring, depending on the number of nitrogens in it, linked by a carbon–nitrogen bond to other aromatic rings. This characteristic gives rise to structures with high persistence in the environment and resistant to conventional biological treatments, remaining in wastewater treatment plant effluents [10,11]. Environmental exposure to azoles can cause multiple negative effects, such as promoting the evolution of fungal resistant species [12], toxic effects on plants [13], and endocrine disruption resulting from their use in the composition of pesticides and antifouling agents [14,15].
This study focuses on seven azole compounds: fluconazole (FCZ) and sulfamethoxazole (SFZ) as pharmaceuticals; metconazole (MTZ), penconazole (PNZ), and tebuconazole (TBZ) as pesticides; and benzotriazole (BZ) and methyl benzotriazole (MBZ) as industrial antifouling agents. The compounds FCZ, SFZ, MTZ, PNZ, and TBZ were included in the third EU surface water monitoring list [16], while the contaminants BZ and MBZ are among the twelve micropollutants selected to measure the effectiveness of quaternary treatments to be implemented in EU wastewater treatment plants [17].
There are many technologies capable of removing CEC [18,19,20]. Among the most widely used full-scale technologies are some advanced oxidation processes (AOP) and activated carbon (AC) adsorption processes, which can be applied individually or in combination.
The present research focuses on the removal efficiency of azo compounds by means of ultraviolet photolysis, hydrogen peroxide oxidation, and adsorption with granular activated carbon.

1.1. Advance Oxidation Processes

Advanced oxidation processes (AOP) are based on the generation by different mechanisms of species with a high oxidizing power, fundamentally hydroxyl radicals (∙OH), with a high oxidation potential (E° ∙OH = 2.80 V). The hydroxyl radical has low selectivity, high reactivity, a short life, electrophilic character, easy generation, ubiquity in the natural environment, and good control of the kinetic reaction [21]. Thus, AOP are able to degrade and mineralize compounds refractory to biological treatments [22,23,24], mainly attacking double bonds, amine groups, and activated aromatic rings [25].
A salient feature of these technologies is their capacity to chemically modify persistent organic pollutants, thereby obviating the need for phase transfer processes. Consequently, the generation of waste products, such as sludge, is significantly reduced. In addition, these technologies can completely mineralize the pollutant. The negative aspects include long reaction times and the generation of reaction by-products whose toxicity can be higher than that of the initial compound [26,27,28].
Authors such as [26,29,30] have studied the removal of CEC with advanced oxidation technologies. However, since these studies cover a broad spectrum of compounds of emerging interest, it can be concluded that research on the removal of azole compounds by AOP has received limited attention because authors such as [31] study these oxidation technologies to remove COD and toxicity caused by Escherichia coli or coliforms. The author [32] is a researcher who studies the removal of CEC such as fluconazole by photo-Fenton, concluding that 80% is removed but generating 38 transformation products; therefore, it is interesting to study other removal methodologies that do not generate by-products such as AC.

1.1.1. Ultraviolet Photolysis

One of the technologies investigated for CEC reduction is ultraviolet photolysis, which is an advanced oxidation process based on the breakdown of molecules due to the input of energy that excites them [10,33]. Mainly the molecule breakdown is generated by double bonds, activated aromatic rings, and functional groups such as amine and amide [25].
Ultraviolet photolysis is an effective treatment for decomposing organic compounds by oxidation of the molecule, which can occur either directly or indirectly. In direct photolysis, the compound directly absorbs the photons, leading to the degradation of the contaminant, while in indirect photolysis, the chemical bond is broken, which requires photosensitizers such as hydrogen peroxide [34].
Emerging contaminants will be removed by this technology if their molecular structure is able to absorb radiation or light. If this occurs, the energy of the molecule will increase until it reaches an excited state where the chemical bond will be broken, and as a consequence, there will be a degradation of the micropollutant [27,28].

1.1.2. Hydrogen Peroxide

Hydrogen peroxide is an oxidant generally used to remove organic matter, dyes, or surfactants, among others. This reagent is selective and has a high oxidizing power. Hydrogen peroxide has an oxidation potential of (1.77 V) and also has a high capacity to produce hydroxyl radicals, whether or not radiation is present. It is therefore a versatile oxidant for degrading recalcitrant compounds such as contaminants of emerging concern [33]. A disadvantage of this compound is that its concentration has to be adjusted to each aqueous matrix, as excess addition causes high concentrations of ∙OH radicals, which can generate competitive reactions and cause an inhibitory effect on the degradation of organic compounds [26].

1.2. Adsorption by Activated Carbon

Adsorption by activated carbon is based on an interaction between adsorbent and adsorbate related to two variables: the amount of activated carbon and the carbon-water contact time [32]. In addition, the physicochemical properties of the carbon and its surface structure determine the retention of different types of contaminants of emerging concern [35].
Activated carbon is a carbonaceous material that incorporates a large number of pores. The pores can be of different shapes and sizes (micropores, mesopores, and macropores), with most of the adsorption occurring in the micropores. This varied pore structure gives carbon its main physical property; it has a large adsorption surface area and is therefore very efficient for the removal of micropollutants from water. Activated carbon is generated from raw materials such as coconut shells, bituminous minerals, etc., by subjecting them to thermal treatments to generate pores and increase their surface area and therefore their adsorption capacity. The specific capacity to adsorb organic compounds is related to the adsorbate and the adsorbent. The adsorbate will be influenced by its physicochemical characteristics, such as the octanol–water partition coefficient (Kow), molecular size, aromaticity, and presence of specific functional groups, while the adsorbent is affected by the area, size, pore, and surface chemistry, as carbon has abundant chemical groups on the surface that aid adsorption through Van der Waals forces, capillary force, dipole–dipole interaction, hydrogen bonding, hydrophobic, and electrostatic interaction. In waters with the presence of organic matter, the efficiency of the carbon may decrease, as it would compete for pore voids with the micropollutants, which could clog them [29,36,37,38].
The advantages of activated carbon are that it is relatively inexpensive to purchase and its application has low energy consumption; it is easy to operate both continuously and discontinuously; once saturated, it can be reused after regeneration, so it has low waste generation; and it can be applied in low concentrations [39]. It has a high capacity to adsorb organic compounds such as emerging contaminants and by-products of oxidation reactions (formaldehyde, glycoxal, pyruvic, formic, and oxalic acids, among others), making it a very effective treatment, both individually and in combination with other technologies. Authors such as [29,39,40,41] demonstrate its high removal rates of substances in both drinking and wastewater.
According to [42], the removal of azole compounds by activated carbon has been scarcely addressed, with precedents being the research of [43] and [44], where a strong adsorption of benzotriazole (>80%) on activated carbon was observed.
The combination of an oxidation treatment, such as ultraviolet photolysis, with activated carbon could be a good solution to retain degradation by-products and complete the removal of compounds that have not been removed in adequate percentages in the previous technology.

2. Materials and Methods

2.1. Selected Micropollutants

The seven emerging contaminants studied are benzotriazole (BZ), fluconazole (FCZ), metconazole (MTZ), methyl benzotriazole (MBZ), penconazole (PNZ), sulfamethoxazole (SFZ), and tebuconazole (TBZ), purity 95–98%, which were supplied by CymitQuímica and Sigma-Aldrich (St. Louis, MA, USA). Table 1 shows the molecular structure and some relevant physicochemical properties. The properties were obtained from the PumChem database.

2.2. Analytical Methodology

The analytical technique used for the analysis of the CEC was high-performance liquid chromatography coupled to a mass spectrometer of triple quadrupole masses (UHPLC-MS/MS). An Agilent Model 1290 Infinity HPLC-MS analyzer (Santa Clara, CA, USA), consisting of online UHPLC with a triple quadruple spectrometer with JetStream and iFunnel technology (UHPLC-1290/QQQ-6490), was used.
A capillary column with stationary phase C18 (a monolayer of dimethyl-n-octadecylsilane), model Zorbax Eclipse Plus C18 2.1 × 100 × 1.8 micron, was used. This column is particularly useful for the separation of acidic, basic, and other highly polar compounds by reversed-phase liquid chromatography. The analysis was performed by direct injection and the multiresidue method. The conditions for the analysis were as follows:
  • Volume injected (µL): 1
  • Injection mode: Injection with needle flushing
  • Mobile phase: Water (A)/acetonitrile (B)
  • Mobile phase flow rate (mL∙min⁻1): 0.4
  • Initial oven temperature (°C): 25
  • Ramp: 10 min 15% A 85% B, 10.50 min 2% A 98% B, 11.00 min 2% A 98% B, 12.00 min 85% A 15% B
  • Time (min): 12
For sample preparation, the solid compounds were dissolved with HPLC-grade methanol (supplied by PanReac Applichem, Castellarr del Valles, Spain) to concentrations of 20.000 mg/L. From the individual compound solutions, a stock solution was prepared with all compounds at a concentration of 50 mg/L, which was stored at −20 °C in topaz-colored glass bottles to avoid photodegradation. From this solution, standards of 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 5, 10, and 25 µg/L were prepared.
Prior to analysis, all samples are filtered through a 0.45-micron polyvinylidene fluoride (PVDF) filter.
Limits of quantification were between 0.05 and 2.5 ng/mL.

2.3. Aqueous Matrix

The experiments were performed using a synthetic aqueous matrix in which the target compounds were introduced at an inlet concentration of 10 µg/L. This concentration, similar to those monitored in WWTP influents, was also sufficient for the non-eliminated fraction to be above the detection limits of the analyzer equipment. The organic load of the influent was equivalent to a COD of about 50 mgO2/L, similar to the order of magnitude of urban wastewater treatment plant effluents. For this purpose, the methodology DIN 38 412-L24 described by [21] was followed. The characterization of COD in the aqueous matrix was carried out using cuvette tests [45] supplied by Sigma-Aldrich.

2.4. Calculation of the Removal Rate

The effectiveness of the applied treatment was determined by the difference between the concentrations of the compounds in the influent and effluent of the treatment, divided by the feed concentration expressed as a percentage.
E = C i − C e C i ∗ 100
where:
  • E: treatment efficiency (%)
  • Ci: concentration of the compound in the influent
  • Ce: concentration of the compound in the effluent

2.5. Ultraviolet Photolysis Tests

In accordance with other investigations to remove micropollutants from treated wastewater by UV photolysis [29,46,47,48,49], in this work we applied intensities ranging from 7.000 to 31.000 J/m2. An NIQ 60/35 XL lamp (UV-Consulting Peschl, Castellon, Spain) connected in a closed circuit with the water to be treated was used for the experimentation (Figure 2).
The lamp, calibrated following the methodology described by author [49], supplied an intensity of 1069 J/m2.
The operational parameters are shown in Table 2.
Samples were filtered through 0.45 µm filters and placed in opaque 2 mL vials and stored at −20 °C for further analysis.

2.6. Hydrogen Peroxide Oxidation

Hydrogen peroxide, H2O2, is commonly used to promote hydroxyl radical precursors in ozone-based processes [26,50], UV-based processes [46], or electrochemical processes [51]. There are very few literature references of its use as a single technology for CEC removal [26]. In this research, we tested its efficacy as a single treatment, applying concentrations of 10, 50, 500, and 1000 mg H2O2/L.
The investigations were carried out in a jar test (JT60E from OVAN) with stirring speed regulation (Figure 3).
The reactors were covered with aluminum foil to protect them from light (Figure 3). The reaction time was 30 min, which is adequate for a future scale-up to a pilot plant without oversizing. At the end of each test, the residual unreacted peroxide was determined by iodometric titration. Peroxide analysis is performed by titration with 0.1 N sodium thiosulphate (Na2S2O₃ * 5 H2O), 1% starch as an indicator, potassium iodide (KI), 1 N sulphuric acid (H2SO₄), and 2% amino molybdate solution as reagents, together with the aqueous sample to be analyzed. The operational parameters are shown in Table 3.
Table 4 shows the monitoring of hydrogen peroxide concentrations throughout the experiment by obtaining the inlet and residual H2O2 concentrations. The percentage of peroxide consumed per treatment is also calculated.
Samples were collected with 5 mL syringes, then filtered through PVDF filters with a pore size of 0.45 µm and placed in opaque 2 mL vials and stored at −20 °C for further analysis.

2.7. Activated Carbon Adsorption

A medium-activity commercial granular activated carbon, GAC (AquaSorb™ CS, Jacobi Group, Penang, Malaysia), manufactured by steam activation of coconut shell charcoal, was used for the tests. This carbon is used to remove low molecular weight or trace organic compounds and is effective for the removal of oxidizing agents such as chlorine and ozone. The main characteristics of commercial GAC are shown in Table 5.
The data in Table 5 reflect that the porous structure of the AC has a large surface area that provides numerous adsorption sites for retaining organic compounds. This property, together with the specific preparation of the carbon surface, ensures high treatment efficiency.
The tests were performed in the jar test device described above (Figure 3), applying the methodology proposed in D 3860-98 [52]. Synthetic wastewater doped with 10 µg/L of each CEC was introduced into each reactor. Five different concentrations of GAC, 100, 500, 1000, 2000, and 4000 mg/L, and one blank without CEC were applied in parallel for a maximum contact time of 24 h. Samples were taken at 3, 6, and 24 h [39,41,53]. The conditions are summarized in Table 6.
Samples of 5 mL were collected with graduated syringes, filtered with PVDF filters with a pore size of 0.45 µm, placed in opaque 2 mL vials, and stored at −20 °C for further analysis.

3. Results and Discussion

3.1. Ultraviolet Photolysis

The synthetic wastewater was treated by photolysis with UV radiation at intensities of 7.500, 16.000, 26.000, and 31.000 J/m2. High radiation intensities were necessary because compounds with a large number of aromatic rings, such as azo compounds, are more persistent [11] and cannot be removed at low intensities [30]. The intensities used in this study are higher than those commonly used to disinfect water [54]. In fact, the mechanism of reduction of emerging contaminants by ultraviolet photolysis is based on an energy input that leads to the excitation of molecules and, consequently, to molecular breakdown, so the energy input must be high for this to occur [10,33].
Figure 4 shows the removal rates of the azoles for each applied radiation intensity. It can be seen that the compounds BTZ, MBZ, and SFZ are almost completely removed even with the lowest radiation intensity applied, 7.500 J/m2. This is due to the fact that in addition to containing the azole group, they contain double bonds between carbons in the case of BTZ and MBZ and amine groups in the case of SFZ. These functional groups promote the oxidation of the compound, which explains its rapid elimination [25,55]. For the rest of the compounds, it is observed that the higher the intensity applied, the higher the percentage of removal. The compounds that require 31.000 J/m2 to achieve an elimination percentage of more than 80% contain, in their molecular structure, in addition to the triazole functional group, functional groups such as hydroxyl or halogens, which require higher intensities. The FCZ compound is the most resistant to UV photolysis treatment, which can be explained considering that the dominant degradation pathway for this treatment is dehalogenation, and FCZ contains the C–F bond which is significantly stronger than the C–Cl bond present in other azo compounds [10]. Overall, the UV photolysis efficiency for the compounds studied is BTZ ≈ MTB ≈ SMZ > MTZ ≈ PCZ ≈ TBZ > FCZ.

3.2. Hydrogen Peroxide

The experiments to treat the azole-doped synthetic wastewater with hydrogen peroxide (H2O2) were carried out in batch mode, applying concentrations of 10, 50, 500, and 1000 mg H2O2/L. The reaction time was 30 min. Taking into account the remaining H2O2 concentrations in each reactor (Table 4), the effective concentrations that reacted with the synthetic water were 10, 50, 330, and 830 mg H2O2/L. Figure 5 shows the percentage removal of each CEC for each effective concentration.
It can be observed that the treatment of azo compounds by hydrogen peroxide is not an effective single technology since, except for SMZ, removal efficiencies above 80% are not achieved. The behavior is similar for all compounds for concentrations of 10, 50, and 330 mg/L, with progressively increasing removal rates, but between concentrations of 330 and 830 mg H2O2/L, the removal rate increases slightly or even decreases. This is because H2O2 in excess can act as a scavenger of hydroxyl radicals and compete for them, inhibiting the oxidation of the target organic compound [56,57,58]. Therefore, hydrogen peroxide is not effective for the removal of the studied azoles applied as a unique technology.

3.3. Activated Carbon Adsorption

Figure 6, Figure 7 and Figure 8 show the removal percentages obtained for each compound with the different GAC concentrations used at 3, 6, and 24 h of contact time. The compounds BZ and MBZ have shown a very high adsorption capacity and speed of adsorption, since in 3 h they have been totally adsorbed with a GAC concentration of 1.000 mg/L. SMZ is also totally adsorbed in 3 h, although it requires a concentration of 4.000 mg GAC/L. FCZ is also totally adsorbed, although it requires a time of 24 h and high GAC concentrations. Of the remaining azoles, TBZ achieves 80% elimination at doses above 1.000 mg/L, while MTZ and PCZ show the lowest adsorption capacity. A qualitative classification from the highest to the lowest adsorption capacity in the tested GAC would be BZ ≈ MBZ > SMZ > FCZ > TBZ > MTZ ≈ PCZ.
The adsorption capacity of each of the compounds is related to the characteristics of the adsorbent material (specific surface area, volume, pore size and distribution, elemental composition of the material, among others), properties of the adsorbates (molecular weight, polarity, number of aromatic rings, interactions with the adsorbent, electrostatic, covalent, and π–π interactions), and the characteristics of the aqueous matrix (pH, temperature, composition), which can affect and compete with the active centers of adsorption [32,37,39,59]. Consequently, it can be very risky to predict the behavior of trace compounds in adsorption processes. In general, it can be indicated that CEC adsorption will be promoted by higher molecular weight, a higher number of functional groups, lower solubility, higher hydrophobicity, and lower polarity [59]. Naturally, the greater or lesser incidence of these properties will be conditioned by the properties of the adsorbent and the aqueous matrix.
The azoles that adsorb faster, MZ and MBZ, have as favorable factors the presence of aromatic rings and low polarity; on the other hand, SMZ has a high polarity, but as favorable factors low solubility and high molecular weight, and FCZ has very low solubility and also high molecular weight. On the other hand, of the compounds that adsorb the least, MTZ has a very high solubility, while TBZ and PCZ have all favorable properties for good adsorption, despite the behavior observed in this test, so that for these compounds, the conditions of the aqueous matrix and the specific interactions with the surface properties of the GAC must influence.

4. Conclusions

The compounds benzotriazole, methylbenzotriazole, and sulfamethoxazole are almost completely eliminated at the lowest radiation intensity of 7.500 J/m2. Fluconazole is the most resistant compound to UV treatment, for which 80% removal is not achieved at the highest applied dose of 31.000 J/m2. Advanced oxidation of azole compounds using hydrogen peroxide is not an effective technology for achieving 80% removal if used as a single treatment, and in this work approximately 50% removal was achieved for an effective dose of 330 mg/L. Granular activated carbon can be an effective technology for adsorbing the azo compounds studied. A sequence from highest to lowest adsorption capacity was found in the GAC tested: benzotriazole ≈ methylbenzotriazole > sulfamethoxazole > fluconazole > tebuconazole > metconazole ≈ penconazole. One of the most important synergies of these treatments is the capacity of the AC to retain oxidation by-products; therefore, with this treatment we retain the compounds that oxidation fails to eliminate together with the by-products. Within the same family of compounds, such as the azoles studied, not all behave in the same way due to their different physicochemical properties, which means that for each compound a particular treatment may be preferable. Therefore, it is foreseeable that the synergies derived from the combination of two technologies will result in a higher removal efficiency. These technologies need to be further explored along with emerging pollutants to improve the research pipeline and optimize large-scale sustainable applications.

Author Contributions

This manuscript was written through contributions of all authors named and all of them have given their approval to the final version of the manuscript. M.F. conceptualization, validation, formal analysis, investigation, resources, data curation, writing original draft preparation, writing review and editing, supervision; M.J.M.-L. conceptualization, validation, formal analysis, investigation, review and editing, supervision; E.D. and N.O. review; D.P. investigation, review and editing, supervision and project administration. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Centre for Technological Development and Innovation -CDTI, an agency under the Ministry of Science and Innovation through the project Sustainability, Water and Agriculture in the 21st century SOS-AGUA-XXI (MIG-20211026), which is coordinated by the company Sacyr Agua, with the participation of companies such as Valoriza Servicios Medioambientales, Bosonit, Tepro, Regnera, Aeromedia, Föra and Aqua Advise.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.

Acknowledgments

The research is part of the research, development and innovation project called Sustainability, Water and Agriculture in the 21st century SOS-AGUA-XXI (MIG-20211026), awarded by the Centre for Technological Development and Innovation -CDTI, an agency under the Ministry of Science and Innovation, which is coordinated by the company Sacyr Agua, with the participation of companies such as Valoriza Servicios Medioambientales, Bosonit, Tepro, Regnera, Aeromedia, Föra and Aqua Advise. The development of this project has been carried out at the University Institute of Water and Environmental Sciences of the University of Alicante.

Conflicts of Interest

The authors declare no conflicts of interest. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in the paper. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

References

  1. Wang, Z.; Walker, G.W.; Muir, D.C.G.; Nagatani-Yoshida, K. Toward a Global Understanding of Chemical Pollution: A First Comprehensive Analysis of National and Regional Chemical Inventories. Environ. Sci. Technol. 2020, 54, 2575–2584. [Google Scholar] [CrossRef]
  2. Dulio, V.; van Bavel, B.; Brorström-Lundén, E.; Harmsen, J.; Hollender, J.; Schlabach, M.; Slobodnik, J.; Thomas, K.; Koschorreck, J. Emerging pollutants in the EU: 10 years of NORMAN in support of environmental policies and regulations. Environ. Sci. Eur. 2018, 30, 5. [Google Scholar] [CrossRef] [PubMed]
  3. Verlicchi, P.; Al Aukidy, M.; Zambello, E. Occurrence of pharmaceutical compounds in urban wastewater: Removal, mass load and environmental risk after a secondary treatment-A review. Sci. Total Environ. 2012, 429, 123–155. [Google Scholar] [CrossRef] [PubMed]
  4. von der Ohe, P.C.; Dulio, V.; Slobodnik, J.; De Deckere, E.; Kühne, R.; Ebert, R.U.; Ginebreda, A.; De Cooman, W.; Schüürmann, G.; Brack, W. A new risk assessment approach for the prioritization of 500 classical and emerging organic microcontaminants as potential river basin specific pollutants under the European Water Framework Directive. Sci. Total Environ. 2011, 409, 2064–2077. [Google Scholar] [CrossRef] [PubMed]
  5. Mertová, D. Recast of the Urban Wastewater Treatment Directive brings new challenges not only in the water management sector. Water Manag. Tech. Econ. Inf. J. 2024, 66, 28–31. [Google Scholar]
  6. Prats, D. Emerging pollutants: Problematic, Legislation, Characterisation and Possible Treatment. Item 2: Water Quality. Master’s Thesis, University of Alicante, Alicante, Spain, 2021. [Google Scholar]
  7. Parida, V.K.; Saidulu, D.; Majumder, A.; Srivastava, A.; Gupta, B.; Gupta, A.K. Emerging contaminants in wastewater: A critical review on occurrence, existing legislations, risk assessment, and sustainable treatment alternatives. J. Environ. Chem. Eng. 2021, 9, 105966. [Google Scholar] [CrossRef]
  8. Saidulu, D.; Gupta, B.; Gupta, A.K.; Ghosal, P.S. A review on occurrences, eco-toxic effects, and remediation of emerging contaminants from wastewater: Special emphasis on biological treatment based hybrid systems. J. Environ. Chem. Eng. 2021, 9, 105282. [Google Scholar] [CrossRef]
  9. Tran, N.H.; Reinhard, M.; Gin, K.Y.H. Occurrence and fate of emerging contaminants in municipal wastewater treatment plants from different geographical regions-a review. Water Res. 2018, 133, 182–207. [Google Scholar] [CrossRef] [PubMed]
  10. Ali, I.; Barros de Souza, A.; Cabooter, D.; De Laet, S.; Van Eyck, K.; Dewil, R. Treatment of antimicrobial azole compounds via photolysis, electrochemical and photoelectrochemical oxidation: Degradation kinetics and transformation products. Environ. Pollut. 2023, 334, 122220. [Google Scholar] [CrossRef] [PubMed]
  11. Pacholak, A.; Burlaga, N.; Frankowski, R.; Zgoła-Grześkowiak, A.; Kaczorek, E. Azole fungicides: (Bio)degradation, transformation products and toxicity elucidation. Sci. Total Environment. 2022, 802, 149917. [Google Scholar] [CrossRef]
  12. Hendrickson, J.A.; Hu, C.; Aitken, S.L.; Beyda, N. Antifungal Resistance: A Concerning Trend for the Present and Future. Curr. Infect. Dis. Rep. 2019, 21, 47. [Google Scholar] [CrossRef]
  13. Richter, E.; Roller, E.; Kunkel, U.; Ternes, T.A.; Coors, A. Phytotoxicity of wastewater-born micropollutants—Characterisation of three antimycotics and a cationic surfactant. Environ. Pollut. 2016, 208, 512–522. [Google Scholar] [CrossRef]
  14. Zarn, J.A.; Brüschweiler, B.J.; Schlatter, J.R. Azole fungicides affect mammalian steroidogenesis by inhibiting sterol 14α-demethylase and aromatase. Environ. Health Perspect. 2003, 111, 255–261. [Google Scholar] [CrossRef] [PubMed]
  15. Sakuragi, Y.; Takada, H.; Sato, H.; Kubota, A.; Terasaki, M.; Takeuchi, S.; Ikeda-Araki, A.; Watanabe, Y.; Kitamura, S.; Kojima, H. An analytical survey of benzotriazole UV stabilizers in plastic products and their endocrine-disrupting potential via human estrogen and androgen receptors. Sci. Total Environ. 2021, 800, 149374. [Google Scholar] [CrossRef]
  16. Decision 2020/1161/EU. Commission Implementing Decision (Eu) 2020/1161. Off. J. Eur. Union 2020, 257, 32–35. [Google Scholar]
  17. Council of the European Union. Proposal for a Directive of the European Parliament and of the Council Concerning Urban Wastewater Treatment (Recast); Letter to the Chair of the European Parliament Committee on the Environment, Public Health and Food Safety (ENVI); European Commission: Brussels, Belgium, 2024; pp. 1–148. [Google Scholar]
  18. Rodriguez-Narvaez, O.M.; Peralta-Hernandez, J.M.; Goonetilleke, A.; Bandala, E.R. Treatment technologies for emerging contaminants in water: A review. Chem. Eng. J. 2017, 323, 361–380. [Google Scholar] [CrossRef]
  19. Shahid, M.K.; Kashif, A.; Fuwad, A.; Choi, Y. Current advances in treatment technologies for removal of emerging contaminants from water—A critical review. Coord. Chem. Rev. 2021, 442, 213993. [Google Scholar] [CrossRef]
  20. Kumar, R.; Qureshi, M.; Vishwakarma, D.K.; Al-Ansari, N.; Kuriqi, A.; Elbeltagi, A.; Saraswat, A. A review on emerging water contaminants and the application of sustainable removal technologies. Case Stud. Chem. Environ. Eng. 2022, 6, 100219. [Google Scholar] [CrossRef]
  21. David Vásquez Rodríguez, E. Instituto Universitario Del Agua Y De Las Ciencias Ambientales. 2018, pp. 18–27. Available online: http://hdl.handle.net/10045/80430 (accessed on 26 December 2024).
  22. De la Cruz, N.; Giménez, J.; Esplugas, S.; Grandjean, D.; De Alencastro, L.F.; Pulgarín, C. Degradation of 32 emergent contaminants by UV and neutral photo-fenton in domestic wastewater effluent previously treated by activated sludge. Water Res. 2012, 46, 1947–1957. [Google Scholar] [CrossRef] [PubMed]
  23. Pérez-González, A.; Urtiaga, A.M.; Ibáñez, R.; Ortiz, I. State of the art and review on the treatment technologies of water reverse osmosis concentrates. Water Res. 2012, 46, 267–283. [Google Scholar] [CrossRef] [PubMed]
  24. Miralles-Cuevas, S.; Audino, F.; Oller, I.; Sánchez-Moreno, R.; Sánchez Pérez, J.A.; Malato, S. Pharmaceuticals removal from natural water by nanofiltration combined with advanced tertiary treatments (solar photo-Fenton, photo-Fenton-like Fe(III)-EDDS complex and ozonation). Sep. Purif. Technol. 2014, 122, 515–522. [Google Scholar] [CrossRef]
  25. Liu, Z.; Demeestere, K.; Van Hulle, S. Comparison and performance assessment of ozone-based AOPs in view of trace organic contaminants abatement in water and wastewater: A review. J. Environ. Chem. Eng. 2021, 9, 105599. [Google Scholar] [CrossRef]
  26. Rodriguez, T.; Botelho, D.; Cleto, E. Tratamiento de Efluentes Industriales de Naturaleza Recalcitrante Usando Ozono, Peróxido de Hidrógeno y Radiación Ultravioleta; Revista Facultad de Ingenieria: 2008. pp. 24–38. Available online: http://www.scielo.org.co/scielo.php?pid=S0120-62302008000400003&script=sci_arttext (accessed on 26 December 2024).
  27. Stasinakis, A.S. Use of selected advanced oxidation processes (AOPs) for wastewater treatment—A mini review. Glob. Nest J. 2008, 10, 376–385. [Google Scholar]
  28. Moya-Llamas, M.J.; Ferre, M.; Dominguez, E.; Trapote, A.; Prats, D. Tecnologías de Oxidación Avanzada Para la Degradación del Fármaco Carbamazepina: La Ozonización; Seguridad Hídrica: 2023. Available online: http://hdl.handle.net/10045/137481 (accessed on 26 December 2024).
  29. Kovalova, L.; Siegrist, H.; Von Gunten, U.; Eugster, J.; Hagenbuch, M.; Wittmer, A.; Moser, R.; McArdell, C.S. Elimination of micropollutants during post-treatment of hospital wastewater with powdered activated carbon, ozone, and UV. Environ. Sci. Technol. 2013, 47, 7899–7908. [Google Scholar] [CrossRef] [PubMed]
  30. de Souza, A.B.; Mielcke, J.; Ali, I.; Dewil, R.; van de Goor, T.; Cabooter, D. Removal of miconazole from water by O3, UV/H2O2 and electrochemical advanced oxidation: Real-time process monitoring and degradation pathway elucidation. J. Environ. Chem. Eng. 2023, 11, 109993. [Google Scholar] [CrossRef]
  31. Antonio da Silva, D.; Pereira Cavalcante, R.; Batista Barbosa, E.; Machulek Junior, A.; César de Oliveira, S.; Falcao Dantas, R. Combined AOP/GAC/AOP systems for secondary effluent polishing: Optimization, toxicity and disinfection. Sep. Purif. Technol. 2021, 263, 118415. [Google Scholar] [CrossRef]
  32. Della-Flora, A.; Wilde, M.L.; Lima, D.; Lima, E.C.; Sirtori, C. Combination of tertiary solar photo-Fenton and adsorption processes in the treatment of hospital wastewater: The removal of pharmaceuticals and their transformation products. J. Environ. Chem. Eng. 2021, 9, 105666. [Google Scholar] [CrossRef]
  33. Cruz, G.; Julcour, C.; Jáuregui, U. El Estado actual y perspectivas de la degradación de pesticidas por procesos avanzados de oxidación State of the art and perspectives of pesticides degradation by advanced oxidation processes Resumen. Rev. Cuba. De Química 2017, 29, 492–516. [Google Scholar]
  34. Ahmed, M.B.; Zhou, J.L.; Ngo, H.H.; Guo, W.; Thomaidis, N.S.; Xu, J. Progress in the biological and chemical treatment technologies for emerging contaminant removal from wastewater: A critical review. J. Hazard. Mater. 2017, 323, 274–298. [Google Scholar] [CrossRef] [PubMed]
  35. Esquerdo, A.A.; Galvañ, P.J.V.; Gadea, I.S.; Rico, D.P. Carbamazepine and diclofenac removal double treatment: Oxidation and adsorption. Int. J. Environ. Res. Public. Health 2021, 18, 7163. [Google Scholar] [CrossRef]
  36. Luo, Y.; Guo, W.; Ngo, H.H.; Nghiem, L.D.; Hai, F.I.; Zhang, J.; Liang, S.; Wang, X.C. A review on the occurrence of micropollutants in the aquatic environment and their fate and removal during wastewater treatment. Sci. Total Environ. 2014, 473–474, 619–641. [Google Scholar] [CrossRef]
  37. Li, W.K.; Shi, Y.P. Recent advances of carbon materials on pesticides removal and extraction based determination from polluted water. TrAC—Trends Anal. Chem. 2024, 171, 117534. [Google Scholar] [CrossRef]
  38. Bogeat, Á.E. Utilización de Carbón Activado y Titania en la Ozonación Fotocatalítica de Contaminantes Emergentes del agua (Doctoral Dissertation, Universidad de Extremadura). 2012. Available online: https://dialnet.unirioja.es/servlet/dctes?codigo=180793 (accessed on 26 December 2024).
  39. Delgado, N.; Capparelli, A.; Navarro, A.; Marino, D. Pharmaceutical emerging pollutants removal from water using powdered activated carbon: Study of kinetics and adsorption equilibrium. J. Environ. Manag. 2019, 236, 301–308. [Google Scholar] [CrossRef]
  40. Ormad, M.P.; Miguel, N.; Claver, A.; Matesanz, J.M.; Ovelleiro, J.L. Pesticides removal in the process of drinking water production. Chemosphere 2008, 71, 97–106. [Google Scholar] [CrossRef]
  41. Díaz Viúdez, A. Estudio de la Eliminación de Fármacos Mediante la Combinación de Carbón Activo y SBR. 75. 2016. Available online: http://hdl.handle.net/10251/67612 (accessed on 26 December 2024).
  42. Wang, W.; Park, S.; Choi B gyu Oh, J.E. Occurrence and removal of benzotriazole and benzothiazole in drinking water treatment plants. Environ. Pollut. 2023, 316, 120563. [Google Scholar] [CrossRef] [PubMed]
  43. Altmann, J.; Rehfeld, D.; Träder, K.; Sperlich, A.; Jekel, M. Combination of granular activated carbon adsorption and deep-bed filtration as a single advanced wastewater treatment step for organic micropollutant and phosphorus removal. Water Res. 2016, 92, 131–139. [Google Scholar] [CrossRef]
  44. Östman, M.; Björlenius, B.; Fick, J.; Tysklind, M. Effect of full-scale ozonation and pilot-scale granular activated carbon on the removal of biocides, antimycotics and antibiotics in a sewage treatment plant. Sci. Total Environ. 2019, 649, 1117–1123. [Google Scholar] [CrossRef]
  45. ISO 15705:2002; Water Quality—Determination of the Chemical Oxygen Demand Index (ST-COD)—Small-Scale Sealed-Tube Method. International Organization for Standardization: Geneva, Switzerland, 2002.
  46. Shu, Z.; Bolton, J.R.; Belosevic, M.; Gamal El Din, M. Photodegradation of emerging micropollutants using the medium-pressure UV/H2O2 Advanced Oxidation Process. Water Res. 2013, 47, 2881–2889. [Google Scholar] [CrossRef]
  47. Tufail, A.; Alharbi, S.; Alrifai, J.; Ansari, A.; Price, W.E.; Hai, F.I. Combining enzymatic membrane bioreactor and ultraviolet photolysis for enhanced removal of trace organic contaminants: Degradation efficiency and by-products formation. Process Saf. Environ. Prot. 2021, 145, 110–119. [Google Scholar] [CrossRef]
  48. Zhang, Y.; Zhang, J.; Xiao, Y.; Chang, V.W.C.; Lim, T.T. Direct and indirect photodegradation pathways of cytostatic drugs under UV germicidal irradiation: Process kinetics and influences of water matrix species and oxidant dosing. J. Hazard. Mater. 2017, 324, 481–488. [Google Scholar] [CrossRef] [PubMed]
  49. Véliz Flores, R.R.; Aronés Medina, E.G.; Palomino Malpartida, Y.G.; Huincho Rodríguez, R. Desinfección Del Efluente Secundario De La Planta De Agua Residual De Ayacucho Con Radiación Ultravioleta Para Su Reutilización En Riego Agrícola. Rev. De La Soc. Química Del Perú 2018, 84, 41–56. [Google Scholar] [CrossRef]
  50. Wang, H.; Zhan, J.; Yao, W.; Wang, B.; Deng, S.; Huang, J.; Yu, G.; Wang, Y. Comparison of pharmaceutical abatement in various water matrices by conventional ozonation, peroxone (O3/H2O2), and an electro-peroxone process. Water Res. 2018, 130, 127–138. [Google Scholar] [CrossRef]
  51. Wang, Y.; Yu, G.; Deng, S.; Huang, J.; Wang, B. The electro-peroxone process for the abatement of emerging contaminants: Mechanisms, recent advances, and prospects. Chemosphere 2018, 208, 640–654. [Google Scholar] [CrossRef] [PubMed]
  52. ASTM D3860-98(2020); Standard Practice for Determination of Adsorptive Capacity of Activated Carbon by Aqueous Phase Isotherm Technique. ASTM: West Conshohocken, PA, USA, 2008.
  53. Requena Molina, M. Diseño de un Sistema Combinado de Carbón Activo y Reactor Biológico Secuencial para Eliminación de Compuestos Farmacéuticos Presentes en Aguas Residuales Urbanas. 2018. Available online: http://hdl.handle.net/10251/108813 (accessed on 26 December 2024).
  54. Alharbi, S.K.; Kang, J.; Nghiem, L.D.; van de Merwe, J.P.; Leusch, F.D.L.; Price, W.E. Photolysis and UV/H2O2 of diclofenac, sulfamethoxazole, carbamazepine, and trimethoprim: Identification of their major degradation products by ESI–LC–MS and assessment of the toxicity of reaction mixtures. Process Saf. Environ. Prot. 2017, 112, 222–234. [Google Scholar] [CrossRef]
  55. Legrini, O.; Oliveros, E.; Braun, A.M. Photochemical Processes for Water Treatment. Chem. Rev. 1993, 93, 671–698. [Google Scholar] [CrossRef]
  56. Chaves, F.P.; Gomes, G.; Della-Flora, A.; Dallegrave, A.; Sirtori, C.; Saggioro, E.M.; Bila, D.M. Comparative endocrine disrupting compound removal from real wastewater by UV/Cl and UV/H2O2: Effect of pH, estrogenic activity, transformation products and toxicity. Sci. Total Environ. 2020, 746, 141041. [Google Scholar] [CrossRef]
  57. Zhang, A.; Li, Y. Removal of phenolic endocrine disrupting compounds from waste activated sludge using UV, H2O2, and UV/H2O2 oxidation processes: Effects of reaction conditions and sludge matrix. Sci. Total Environ. 2014, 493, 307–323. [Google Scholar] [CrossRef]
  58. Okolie, J.A.; Savage, S.; Ogbaga, C.C.; Gunes, B. Assessing the potential of machine learning methods to study the removal of pharmaceuticals from wastewater using biochar or activated carbon. Total Environ. Res. Themes 2022, 1–2, 100001. [Google Scholar] [CrossRef]
  59. Bernal, M.Á. Reducción de Microcontaminantes Mediante Procesos Biológicos, Tratamiento con Membranas y Carbón Activado. 2020. Available online: http://hdl.handle.net/10045/109781 (accessed on 26 December 2024).
Water 17 00212 g001
Figure 1. Illustration of sources of CEC input to water bodies [6].
Figure 1. Illustration of sources of CEC input to water bodies [6].
Water 17 00212 g001
Water 17 00212 g002
Figure 2. Laboratory-scale experimental set-up of UV photolysis.
Figure 2. Laboratory-scale experimental set-up of UV photolysis.
Water 17 00212 g002
Water 17 00212 g003
Figure 3. Hydrogen peroxide laboratory-scale experimental device.
Figure 3. Hydrogen peroxide laboratory-scale experimental device.
Water 17 00212 g003
Water 17 00212 g004
Figure 4. Removal percentages of azole compounds under varying UV radiation intensities (7.500–31.000 J/m2).
Figure 4. Removal percentages of azole compounds under varying UV radiation intensities (7.500–31.000 J/m2).
Water 17 00212 g004
Water 17 00212 g005
Figure 5. Percentage of removal of each CEC for each effective concentration of H2O2 (10–1000 mg H2O2/L).
Figure 5. Percentage of removal of each CEC for each effective concentration of H2O2 (10–1000 mg H2O2/L).
Water 17 00212 g005
Water 17 00212 g006
Figure 6. Removal of azole compounds using activated carbon with a contact time of 3 h, testing different carbon concentrations (100–4000 mgAC/L).
Figure 6. Removal of azole compounds using activated carbon with a contact time of 3 h, testing different carbon concentrations (100–4000 mgAC/L).
Water 17 00212 g006
Water 17 00212 g007
Figure 7. Removal of azole compounds using activated carbon with a contact time of 6 h, testing different carbon concentrations (100–4000 mgAC/L).
Figure 7. Removal of azole compounds using activated carbon with a contact time of 6 h, testing different carbon concentrations (100–4000 mgAC/L).
Water 17 00212 g007
Water 17 00212 g008
Figure 8. Removal of azole compounds using activated carbon with a contact time of 24 h, testing different carbon concentrations (100–4000 mgAC/L).
Figure 8. Removal of azole compounds using activated carbon with a contact time of 24 h, testing different carbon concentrations (100–4000 mgAC/L).
Water 17 00212 g008
Table 1. Structure and physicochemical properties of the azole compounds studied: molecular weight, solubility, octanol/water partition coefficient (Log Kow), polarity, and dissociation constant (pka).
Table 1. Structure and physicochemical properties of the azole compounds studied: molecular weight, solubility, octanol/water partition coefficient (Log Kow), polarity, and dissociation constant (pka).
Chemical StructureChemical and Physical Properties
Benzotriazole
Water 17 00212 i001CAS Number:95-14-7
Molecular formula:C6H5N3
Use:Antifouling basic product
Molecular weight (g/mol):119,12
Solubility (g/L):19 (25 °C)
2H-benzotriazoleLog Kow:1.34
pKa:8.37 (20 °C)
Fluconazole
Water 17 00212 i002CAS Number:86386-73-4
Molecular formula:C13H12F2N6O
Use:Animycotic drug
Molecular weight (g/moL):306.27
Solubility (g/L):4,4 × 10−3 (25 °C)
2-(2,4-difluorophenyl)-1,3-bis(1,2,4-triazol-1-yl)propan-2-olLog Kow:0.5
pKa:1.76 (20 °C)
Metconazole
Water 17 00212 i003CAS Number:125116-23-6
Molecular formula:C17H22ClN3O
Use:Pesticide
Molecular weight (g/moL):319.83
Solubility (g/L):30.4 (20 °C)
5-[(4-chlorophenyl)methyl]-2,2-dimethyl-1-(1,2,4-triazol-1-ylmethyl)cyclopentan-1-olLog Kow:3.85
pKa:-
MetilBenzotriazole
Water 17 00212 i004CAS Number:29878-31-7
Molecular formula:C7H7N3
Use:Antifouling basic product
Molecular weight (g/moL):133.15
Solubility (g/L):4.05 (25 °C)
4-methyl-2H-benzotriazole
5-methyl-2H-benzotriazole		Log Kow:1.08
pKa:8.85 (20 °C)
Chemical StructureChemical and Physical Properties
Penconazole
Water 17 00212 i005CAS Number:66246-88-6
Molecular formula:C13H15Cl2N3
Use:Pesticide
Molecular weight (g/moL):284.18
Solubility (g/L):0.073 (20 °C)
1-[2-(2,4-dichlorophenyl)pentyl]-1,2,4-triazoleLog Kow:3.72
pKa:-
Sulfametoxazole
Water 17 00212 i006CAS Number:723-46-6
Molecular formula:C10H11N3O3S
Use:Antibiotic drug
Molecular weight (g/moL):253.28
Solubility (g/L):0.61 (37 °C)
4-amino-N-(5-methyl-1,2-oxazol-3-yl)benzenesulfonamideLog Kow:0.89
pKa:1.6
Tebuconazole
Water 17 00212 i007CAS Number:107534-96-3
Molecular formula:C16H22ClN3O
Use:Pesticide
Molecular weight (g/moL):307.82
Solubility (g/L):0.036 (20 °C)
1-(4-chlorophenyl)-4,4-dimethyl-3-(1,2,4-triazol-1-ylmethyl)pentan-3-olLog Kow:3.7
pKa:2.3
Table 2. Main ultraviolet operational parameters.
Table 2. Main ultraviolet operational parameters.
Operational Parameters
Volume of waterL15
Initial concentration of each CECµg/L10
Water flow rateL/min8
Radiation intensityJ/m21.069
Duration of testmin58
Table 3. Main parameters hydrogen peroxide operations.
Table 3. Main parameters hydrogen peroxide operations.
Operational Parameters
Volume of water in each reactorL0.5
Concentration of CECµg/L10
Initial Concentration of H2O2mg/L10, 50, 500 and 1000
Test timemin30
Stirring raterpm150
Table 4. Hydrogen peroxide balance: inlet and residual concentrations of hydrogen peroxide and percentage of hydrogen peroxide consumed.
Table 4. Hydrogen peroxide balance: inlet and residual concentrations of hydrogen peroxide and percentage of hydrogen peroxide consumed.
H2O2 Entered (mg/L)H2O2 Residual (mg/L)H2O2 Consumed (%)
100100
500100
50017066
100017083
Table 5. Specifications of tested commercial activated carbon.
Table 5. Specifications of tested commercial activated carbon.
SpecificationAquaSorb CS
Iodine numbermin. 1000 mg/g
Moisture content, as packedmax. 5%
Ash contentmax. 4%
Ball-pan hardnessmin. 98%
Surface are (BET)1050 m2/g
Apparent density540 kg/m3
Table 6. Main operational parameters of the experimental set-up with activated carbon.
Table 6. Main operational parameters of the experimental set-up with activated carbon.
Operational Parameters
Volume of water in each reactorL0.5
Concentration of CECµg/L10
Concentration of GACmg/L100, 500, 1000, 2000 and 4000
Stirring raterpm150
Duration of testh24
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Ferre, M.; Moya-Llamas, M.J.; Dominguez, E.; Ortuño, N.; Prats, D. Advanced Oxidation Processes and Adsorption Technologies for the Removal of Organic Azo Compounds: UV, H2O2, and GAC. Water 2025, 17, 212. https://doi.org/10.3390/w17020212

AMA Style

Ferre M, Moya-Llamas MJ, Dominguez E, Ortuño N, Prats D. Advanced Oxidation Processes and Adsorption Technologies for the Removal of Organic Azo Compounds: UV, H2O2, and GAC. Water. 2025; 17(2):212. https://doi.org/10.3390/w17020212

Chicago/Turabian Style

Ferre, M., M. J. Moya-Llamas, E. Dominguez, Nuria Ortuño, and D. Prats. 2025. "Advanced Oxidation Processes and Adsorption Technologies for the Removal of Organic Azo Compounds: UV, H2O2, and GAC" Water 17, no. 2: 212. https://doi.org/10.3390/w17020212

APA Style

Ferre, M., Moya-Llamas, M. J., Dominguez, E., Ortuño, N., & Prats, D. (2025). Advanced Oxidation Processes and Adsorption Technologies for the Removal of Organic Azo Compounds: UV, H2O2, and GAC. Water, 17(2), 212. https://doi.org/10.3390/w17020212

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop