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Article

Impact of Photolysis and TiO2 on Pesticides Degradation in Wastewater

by
Mohamed H. EL-Saeid
1,*,
Modhi. O. Alotaibi
2,*,
Mashael Alshabanat
3,*,
Murefah Mana AL-Anazy
3,
Khadijah R. Alharbi
2 and
Abeer S. Altowyan
4
1
Chromatographic Analysis Unit, Soil Science Department, College of Food & Agricultural Sciences, King Saud University, P.O. Box 2460, Riyadh 11451, Saudi Arabia
2
Department of Biology, College of Science, Princess Nourah Bint Abdulrahman University, Riyadh 11564, Saudi Arabia
3
Department of Chemistry, College of Science, Princess Nourah Bint Abdulrahman University, Riyadh 11564, Saudi Arabia
4
Department of Physics, College of Science, Princess Nourah Bint Abdulrahman University, Riyadh 11564, Saudi Arabia
*
Authors to whom correspondence should be addressed.
Water 2021, 13(5), 655; https://doi.org/10.3390/w13050655
Received: 14 January 2021 / Revised: 19 February 2021 / Accepted: 21 February 2021 / Published: 28 February 2021
(This article belongs to the Section Wastewater Treatment and Reuse)
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Versions Notes

Abstract

:
Pesticide residues are harmful to the environment and human and animal health even at low levels because of long-term bioaccumulation. In this study, photolysis was applied to treat three representative water samples: aqueous atrazine and dimethoate solutions as target pesticides, as well as wastewater and agriculture wastewater containing pesticide residue. It was performed using ultraviolet (UV) irradiation at two wavelengths (254 and 306 nm) with exposure times ranging from 2 to 12 h in the presence and absence of a photocatalyst to identify the optimal degradation conditions. Extraction and analyzation process were performed by the Quick Easy Cheap Effective Rugged Safe (QuEChERS) methods and gas chromatography–tandem mass spectrometry with triple quadrupole detector (GC–MSMS/TQD), respectively. Photodegradation increased with an increase in exposure time and the TiO2 catalyst was beneficial for degradation. Both selected irradiation wavelengths were effective, although the wavelength of λ = 306 nm was the most efficient.

1. Introduction

Pesticides are used to improve crop plant quality and reduce losses because of insects. They are applied at various stages of cultivation and during post-harvest storage of various crops [1]. The wide-ranging use of pesticides has significant advantages in agriculture, but the inappropriate selection of pesticides, their over-use, and harvesting crops before washing off the residues can result in negative effects and undesirable pesticide levels in the produce that reaches consumers [2,3]. Exposure to pesticides can be direct, e.g., oral, inhalation, and dermal or indirect, e.g., through food, drinking water, residential, and occupational exposure. The consumption of pesticide-laden food crops is a major concern [4]. The persistent nature of pesticides can cause damage to the environment via transportation in water, soil, and air, leading to widespread environmental contamination [5,6,7,8,9,10].
Furthermore, the use of pesticides has been linked to human health risks, including acute effects such as nausea and headaches and chronic effects such as reproductive harm, endocrine system disruption, and cancer [11]. The potential damage of pesticides has been outlined in detail by Walker et al. [12].
Currently, many kinds of commodity pesticides are commercially available and are commonly used in agricultural practices. A commonly used pesticide worldwide is dimethoate (O, O-dimethyl-S-(N-methylcarbamoylmethyl) phosphorodithioate), an organophosphorus insecticide first registered in 1962 [13]. It can be applied to control a wide range of insects including flies, aphids, mites, and plant hoppers [13] in crops including grains, vegetables, fruits, and ornamentals.
Atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) is another commonly used chemical and a member of the s-triazine group of herbicides [14,15,16]. Serious negative effects and irritation to the eyes, nose, and throat can be caused by exposure to atrazine [17]. Atrazine had been found in rivers, high mountain lakes, ground water, drinking water supplies, rainwater, and even in fog [18].
Although several techniques have been reported to treat residual pesticides in the environment including electrochemical degradation [19,20] and membrane technology [21], photolysis and photocatalytic degradation of pesticides are widely used techniques to remove pesticides such as atrazine and dimethoate from the environment [22,23,24,25,26,27,28]. The photolysis process and photochemical approaches used to treat a wide range of pesticides were reviewed by Burrows et al. [29], Petala et al. [30], Pirsaheb and Moradi [31] Kanan et al. [32] and Reddy and Kim [33]. Titanium dioxide (TiO2) is the most suitable catalyst for industrial use, it has more photocatalytic efficacy and stronger stability with low cost [34]. Most importantly, it is safe for the environment and humans [35,36,37].
The importance of this work is in studying the photodegradation of very risky polluting chemicals such as pesticides in very needy sources of life, which is water, and to the best of knowledge, this is the first Saudi Arabian report of UV use in remediation of real samples of the pesticide atrazine and dimethoate-polluted water taken from the local environment, including treated wastewater and agriculture wastewater. It is strongly believed that the findings of this study will provide new data to environmental pollution and water remediation scientists, especially Saudi ones.
This study was performed to evaluate the presence of atrazine and dimethoate residues in local water sources in Riyadh city, the Kingdom of Saudi Arabia via extraction by the Quick Easy Cheap Effective Rugged Safe (QuEChERS) methods and analysis by gas chromatography/tandem mass spectrometry with triple quadrupole detector (GCMSMS/TQD). UV irradiation at various wavelengths and exposure times with and without catalyst was conducted to identify the optimal duration, wavelength for maximum degree of pesticide decomposition in the tested samples, and effect of catalyst addition on the photodegradation.
Chromatographic analysis was selected in this study because it is the only method which includes analyzing the pesticide residues and composition at the same time, ensuring no similarity or overlap with other compounds.

2. Materials and Methods

2.1. Sampling and Standards

Three water samples were used as targets in the study; deionized water from the Millipore deionized water system, Faculty of Food and Agriculture King Saud University. Also treated wastewater samples from the Almansuriyah treatment plant in Riyadh city in Saudi Arabia (pH = 7.33, EC = 1.77 µS/cm, TDS = 1133 mg/L, turbidity = 1.89 NTU) where treatment process is performed by activated sludge method using tertiary treatment. Agriculture wastewater taken from the Alkharj agriculture region (pH = 8.42, EC = 2.48 μS/cm, TDS = 1579 mg/L, turbidity = 3.24 NTU). The crops produced by the farms are date palm, grains and corn, some vegetables such as eggplant, pepper, zucchini and leafy crops such as mint, lettuce, parsley and watercress.
As for analytical parameters of gas chromatography, internal, calibration, and injection standards with declared 99.9% purities were purchased from AccuStandard, 153 Inc., New Haven, CT, USA, as individual or mixed standards at a concentration of 10 μg/mL. All internal standards were 13C 12-labelled, as the use of 13C-labelled compound is preferable because quantification can be performed without clean-up (Maestroni et al., 2000; Maestroni 2002).
Methanol, dichloromethane, and acetonitrile obtained from Fisher Scientific (Fair Lawn, NJ, USA) were used as solvents for the extraction and analysis of the pesticides and were of residue-analysis grade (99.9% purity). Quick Easy Cheap Effective Rugged Safe (QuEChERS) kits were purchased from Phenomenex, Madrid Avenue, Torrance, CA, USA. Titanium dioxide (TiO2) as a photocatalyst was purchased from Sigma-Aldrich Chemie GmbH, Germany (molecular weight: 79.87, CAS Number: 13463-67-7, 718467nanopowder, 21 nm primary particle size (TEM), ≥99.5% trace metals basis).

2.2. Remediation by Ultraviolet (UV) Photolysis

Photolysis of atrazine and dimethoate using UV irradiation at 254 and 306 nm for different durations was performed to investigate their effects on the pesticide photolysis process. Two devices of Boekel UV Crosslinker (BUV) model: 234100-2: 230 VAC, 175 W, 0.8 A, Boekel Scientific, 855 Pennsylvania Blvd. Feasterville, PA, USA. The first one was held with four 254 nm lamps and the second with four 306-nm lamps. The distance between lamps and water samples was 15 cm, and the UV irradiation intensity was 1071 μWcm−2.

2.3. Sample Treatments

Natural water samples (10 mL) and those spiked with 2000 PPb of pesticides (2 ppm) were incubated for 12 h under UV light and aliquots (10 mL) were removed at intervals of 2 h to determine the remaining quantity of pesticides. The same procedure was applied after adding 0.001 g of TiO2 as a photocatalyst to each 10 mL of water samples before UV remediation for 2 to 12 h.

2.4. Samples Preparation and Extraction and Cleanup by Quick Easy Cheap Effective Rugged Safe (QuEChERS)

First, 10 mL of the water sample was transferred into a 50 mL centrifuge tube, and vortexed briefly. Then, 10 mL of acetonitrile was added to each sample. Samples were shaken (manually or mechanically) or vortexed for 5 min to extract pesticides. (In this study a Spex SamplePrep Geno/Grinder 2010 operated at 1500 rpm was used). After that, the contents of an ECQUEU750CT-MP (citrate salts) Mylar pouch were added to each centrifuge tube. Immediately samples were shaken for at least 2 min and centrifuge for 5 min at ≥3500 rcf. We transferred a 1 mL aliquot of supernatant to a 2 mL CUMPSC18CT (MgSO4, PSA, C18) dSPE tube. Samples were vortexed for 0.5–1 min. They were centrifuged for 2 min at high rcf (e.g., ≥5000). Purified supernatant was filtered through a 0.2 μm syringe filter directly into a GC sample vial. Finally, the samples were analyzed by GC-MS/MSTSQ 8000/SRM.

2.5. Analysis by Gas Chromatography–Tandem Mass Spectrometry with Triple Quadrupole Detector (GC–MSMS/TSQ) 8000/SRM

All measurements were carried out using the latest Thermo Scientific™ TSQ 8000™ triple quadrupole GC-MS/MS system equipped with the Thermo Scientific™ TRACE™ 1310 GC with SSL Instant Connect™ SSL module and Thermo Scientific™ TriPlus™ RSH auto sampler. Injection mode was spiltless, Splitless Time 1.0 min GC column TR™ 5 MS, 30 m × 0.25 mm × 0.25 μm, carrier gas He (99.999%, flow rate 1.2 mL/min, constant flow, temperature program 100 °C, 1 min; 10 °C/min to 160 °C, 4 min and 10 °C/min to 250 °C, 2 min, transfer line temperature 280 °C, total analysis time 22.4 min, TriPlus RSH Autosampler Injection volume 1 µL. Ionization mode EI, 70 eV, Ion source temperature 250 °C, scan mode SRM using timed SRM SRM transition setup automatically built-up by AutoSRM software. Transition conditions are shown in (Table 1).

2.6. QAQC Strategies and Method Performance

Quality control samples were prepared and analyzed in triplicate samples, blank and spiked, and certified reference material (CRM) was prepared for this purpose and processed with each batch (5–10 samples). QuEChERS and the GC–MSMS/TSQ 8000 method limit of detection (LOD) and limit of quantification (LQD), repeatability, reproducibility, accuracy and precession also were determined for each compound of the pesticides (Table 2).

3. Results and Discussion

Photoremediation of the pesticide residues for atrazine and dimethoate in different water media was studied: aqueous solutions (AS), wastewater (WW) and agriculture wastewater (Ag.W). The samples were irradiated at two different wavelengths (λ = 254 and 306 nm) in the presence and absence of a catalyst. The results are shown in Figure 1 and Figure 2 and listed in Table 3.
Figure 1 and Figure 2a show the effect of exposure time of irradiation on the degradation of pesticides in aqueous solutions at two different wavelengths (λ = 254 and 306 nm) in the presence and absence of a catalyst. It is clear that the amounts of pesticides decreased with increased UV exposure time, indicating the degradation increases with increasing time, irrespective of the presence of the catalyst.
A similar trend is observed for the photoremediation of the pesticide residues in real water samples such as wastewater and agriculture wastewater (Figure 1 and Figure 2b,c, respectively). To explain the obtained results, the mechanism of the process must be understood, and it can be described as follows:
For a non-catalytic process, the light energy from the radiation is absorbed by the pesticide molecules, which subsequently become activated and attain the excited state. These undergo homolysis, heterolysis, or photoionization, as illustrated in Figure 3a [38].
Khan et al. observed that atrazine could be degraded by direct photolysis at 254 nm by absorbing the photons from UV light and transforming into the excited state, which subsequently decomposes [22]. The mechanism for the direct photolysis of atrazine involves photoinduced solvolysis via the heterolytic cleavage of the C–Cl bond [39,40].
In a photocatalytic process, a semiconductor catalyst is photoexcited by absorbing electromagnetic UV radiation. Upon light absorption, the electrons in the valence band are excited to the conduction band, leaving a positive hole in the valance band [33]. The empty hole in the valence band and the electron in the conduction band can induce reduction or oxidation of the pesticide adsorbate [41], as illustrated in Figure 3b [31].
Thus, the increase in the photodegradation of pesticides with increasing the contact time could be attributed to the higher opportunities of electron transforming into the excited state, and in the case of the catalytic process, leads to generation of more free radicles which are powerful for degradation.
Previous studies reported the importance of the contact time as an effective factor in the photodegradation process. A previous study showed a result in agreement with our results, demonstrating that this phenomenon occurs because of more process of oxidation, and the chance of atrazine photodegradation is higher with increasing exposure time to radiation [42]. The study pointed to the importance of determination of the required time to reach to equilibrium stage wherein the reaction rate reached a plateau at this stage [42].
Furthermore, it is observed that the addition of a catalyst enhances the photoremediation over the irradiation time. After 12 h of irradiation, Pesticides were not detected at either tested wavelengths, but only atrazine was detected at 254 nm. These results agree with the findings reported in the literature. The potential of common pollutants like dimethoate, chlorpyrifos, and malathion in the complete mineralization by photodegradation was investigated by direct and indirect sunlight exposure [23], and it was found that the degradation efficiencies of the various methods of photolysis follow the order, benzophenone sensitized > β-carotene sensitized > direct exposure. Evgenidou et al. observed that the degradation of dimethoate occurred at a very low rate in the absence of the catalyst, while it was positively influenced by the presence of semiconducting oxides (TiO2 and ZnO) as catalysts [43]. It was reported in another study [24] that the efficiency of atrazine degradation by a combination of UV and chlorine was better than that by UV or chlorine alone. Pesticides such as atrazine, thiobencarb, dimethoate, lindane, dipterex, malathion, and bentazone were photodegraded effectively in the presence TiO2 ceramics as catalysts [44]. Atrazine also underwent an effective photocatalytic degradation via microwave-assisted photocatalysis in the presence of nanocatalyst of titania-coated multiwall carbon nanotube [45].
The role is played by the photocatalyst is to facilitate degradation, as suggested by Yola et al. [46]. According to them, the separation of electrons (e–) and holes (h+) is enhanced by the catalyst molecules (TiO2), which help in producing •O2− and •OH radicals. The •OH radical attacks the pesticides, causing their degradation in a stepwise manner that ends up in the generation of small molecules such as Cl−, NO3−, CO2, and H2O [45].
The effect of the wavelength of irradiation (254 and 306 nm) on the degradation of pesticides in the different water media is presented in Figure 4 and Table 3. Although both of them were effective, it was observed that the photoremediation at λ = 306 nm was better than that at λ = 254 nm, in the presence and absence of a catalyst, in agreement with previous studies [47]. This indicates that the increase in wavelength increases the photodegradation because of the destructive effect of UV radiation on molecular bonds, and the enhancement of the electron transmission between the valence and conduction bands, which makes the degradation process easier and faster.
In addition, the results reveal that the tendency of degradation in dimethoate upon irradiation is greater than that in atrazine in both the presence and absence of the photocatalyst. This can be an attribute of the pesticide structure. The difference in the structure of the two pesticides is distinct: atrazine is an aromatic compound, while dimethoate is an aliphatic compound (Figure 5), which can be degraded more easily than the aromatic ring.
Furthermore, and although the effect of dissolved constituents in water samples on photodegradation of pesticides in the water samples was out of the scope of our study, it is worth indicating the role which is played by this kind of matter. In general, UV radiation has a destructive effect on molecular bonds. Therefore, it is expected that the organic matter in water samples can be affected the radiation by absorbing the UV light to be excited and entering in series of reactions [48,49,50,51]. Despite the fact that this matter might be good for our experiment because most of pesticide residues is adsorbed or absorbed in the organic part in the targeted wastewater samples, an inhibitory effect of them on the photodegradation process is also possible [52,53]. A study reported that the dissolved organic matter in the excitation state act as a photosensitizer, enhancing phototransformation of pesticides in addition; it may act as an antioxidant decreasing phototransformation rates through various mechanisms [52]. Inhibition mechanisms by natural organic matter were also reported in another study [53].
The differences in the response of the different water media towards photodegradation could be explained by this factor although it needs to be confirmed by further experiments (Figure 6). However, previous published works highlighted the effect of different organic species on the photodegradation process of pesticides in some aquatic systems and discussed this factor in detail [48,54]. In a recently published review [55], challenges in a photocatalytic process of natural water were compiled by analyzing the cyanotoxins’ remediation, and the critical influence of natural organic matter was discussed.

4. Conclusions

In this study, the photodegradation of atrazine and dimethoate in aqueous solutions and in real water samples such as wastewater and agricultural wastewater collected from Riyadh, Saudi Arabia, was investigated. UV irradiation at λ = 254 and 306 nm was used to induce the photodegradation in the presence and absence of TiO2 as a photocatalyst. The study of effect of time and selected wavelength on the photodegradation was the aim of this work. The samples were extracted by the QuEChERS method and analyzed using gas chromatography–mass spectrometry. The findings show that photoremediation was successfully achieved; the conclusions are the photodegradation increased with the increase of process time under the selected wavelengths of irradiation, particularly at λ = 306 nm. The catalyzed process with TiO2 was more efficient than the uncatalyzed process, although the applied conditions of photodegradation were effective for both the selected pesticides; dimethoate was more easily degradable than atrazine. The photodegradation process conditions are applicable for pesticides residues in real environments. The effect of the structure of the pesticides on the photodegradation process needs to be confirmed by further studies in future. Studying other factors such as the effect of the dissolved constituents in water on the photodegradation process and the effect of other catalysts with evaluating their recyclability is recommended.

Author Contributions

Conceptualization, M.H.E.-S. and M.A.; methodology, M.H.E.-S.; software, M.H.E.-S.; validation, M.H.E.-S.; M.O.A. and M.O.A.; formal analysis, M.H.E.-S.; investigation, M.A. and M.O.A.; resources, M.A., M.H.E.-S., K.R.A. and A.S.A.; data curation, M.A. and M.M.A.-A.; Writing—Original draft preparation, M.A., M.M.A.-A. K.R.A. and A.S.A.; Writing—Review and editing, M.A. and M.O.A.; visualization, M.A.; supervision, M.H.E.-S. and M.A; project administration, M.H.E.-S. and M.A.; funding acquisition, M.H.E.-S. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by Environmental Pollution Research Chair at Princess Nourah Bint Abdulrahman University. Garant No. EP-2018-04.

Institutional Review Board Statement

Not Applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not Applicable.

Conflicts of Interest

The authors declare no conflict of interest.

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Water 13 00655 g001 550
Figure 1. Concentration of pesticides (R = ppb) as a function of exposure time of irradiation for photolysis process of pesticides (non-catalytic process); (a) AS, (b) WW, and (c) Ag.W.
Figure 1. Concentration of pesticides (R = ppb) as a function of exposure time of irradiation for photolysis process of pesticides (non-catalytic process); (a) AS, (b) WW, and (c) Ag.W.
Water 13 00655 g001
Water 13 00655 g002 550
Figure 2. Concentration of pesticides (R(ppb)) as a function of exposure time of irradiation for photocatalysis process of pesticides (catalyst is TiO2); (a) AS, (b) WW, and (c) Ag.W.
Figure 2. Concentration of pesticides (R(ppb)) as a function of exposure time of irradiation for photocatalysis process of pesticides (catalyst is TiO2); (a) AS, (b) WW, and (c) Ag.W.
Water 13 00655 g002
Water 13 00655 g003 550
Figure 3. Scheme of photoremediation process; (a) direct photolysis process (the scheme is quoted from [27]) and (b) photocatalysis process (the scheme is quoted from [31]).
Figure 3. Scheme of photoremediation process; (a) direct photolysis process (the scheme is quoted from [27]) and (b) photocatalysis process (the scheme is quoted from [31]).
Water 13 00655 g003
Water 13 00655 g004 550
Figure 4. Concentration of pesticides (R = ppb) as a function exposure time of irradiation at both wavelengths of ultraviolet (UV) for the photo-remediation process, with and without catalyst, of pesticides; (a) AS, (b) WW, and (c) Ag.W.
Figure 4. Concentration of pesticides (R = ppb) as a function exposure time of irradiation at both wavelengths of ultraviolet (UV) for the photo-remediation process, with and without catalyst, of pesticides; (a) AS, (b) WW, and (c) Ag.W.
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Water 13 00655 g005 550
Figure 5. Structures of pesticides; (a) dimethoate and (b) atrazine.
Figure 5. Structures of pesticides; (a) dimethoate and (b) atrazine.
Water 13 00655 g005
Water 13 00655 g006a 550Water 13 00655 g006b 550
Figure 6. Comparison of photodegradation, with and without catalyst, of pesticides in different water media: concentration of pesticides (R(ppb)) as a function exposure time of irradiation at both wavelengths of UV; (a) Dimethoate (noncatalytic process), (b) Dimethoate (Catalytic process), and (c) Atrazin (noncatalytic process). (d) Atrazin (Catalytic process)
Figure 6. Comparison of photodegradation, with and without catalyst, of pesticides in different water media: concentration of pesticides (R(ppb)) as a function exposure time of irradiation at both wavelengths of UV; (a) Dimethoate (noncatalytic process), (b) Dimethoate (Catalytic process), and (c) Atrazin (noncatalytic process). (d) Atrazin (Catalytic process)
Water 13 00655 g006aWater 13 00655 g006b
Table
Table 1. Gas chromatography–tandem mass spectrometry with triple quadrupole detector (GC–MSMS/TSQ) 8000 SRM instrumental conditions.
Table 1. Gas chromatography–tandem mass spectrometry with triple quadrupole detector (GC–MSMS/TSQ) 8000 SRM instrumental conditions.
GC Trace Ultra ConditionsTSQ Quantum MS/MS Conditions
ColumnTR-Pesticide 30 m × 0.25 mm × 0.25 μmOperating modeSelected Reaction Monitoring (SRM)
InjectorSplitlessIonization modeEI
Injected volume1 μLElectron energy70 eV
Injector temperature225 °CEmission current50 μA
Carrier gasHelium, 1.2 mL/minQ1/Q3 resolution0.7 u (FWHM)
Oven program80 °C hold 1 min 15 °C/min to 160 °C hold 1 min 2.2 °C/min to 230 °C hold 1 min 5 °C/min to 290 °C hold 5 min Run Time 57.15 minCollision gasArgon
Transfer line temperature280 °CCollision gas pressure1 mTorr
PolarityPositive
Table
Table 2. Parameters of retention time (RT), limit of detection (LOD) and limit of quantification (LOQ), recovery % and GC–MS/TSQ target mass of SRM scanning mode.
Table 2. Parameters of retention time (RT), limit of detection (LOD) and limit of quantification (LOQ), recovery % and GC–MS/TSQ target mass of SRM scanning mode.
NameRT
min		MassProduct MassCollision Energy
m/z		LOQ
(ng/mL)		Lod
(ng/mL)		r2Recovery %SD
Dimethoate21.3717612493.551.230.8034102.358.33
Atrazine23.94200122106.843.950.9643108.076.52
Table
Table 3. Mean of concentration of pesticide residues degradation (R(ppb)) at two different wavelengths and irradiation time in the presence and absence of a catalyst (± standard deviation (SD)). (spiked with 2000 PPb) and for catalytic process: 0.001 gm TiO2 /10 mL.
Table 3. Mean of concentration of pesticide residues degradation (R(ppb)) at two different wavelengths and irradiation time in the presence and absence of a catalyst (± standard deviation (SD)). (spiked with 2000 PPb) and for catalytic process: 0.001 gm TiO2 /10 mL.
Aqueous Solution Samples, Non-Catalytic Process
irradiation wavelengthIrradiationtime0 h2 h4 h6 h8 h10 h12 h
λ = 254 nmAtrazine2000 ± 0.02000 ± 0.01776 ± 15.131458.3 ± 7.511130.3 ± 2.08905 ± 4475.33 ± 4.04
Dimethoate2000 ± 0.01927.67 ± 6.511614.67 ± 8.141318.3 ± 6.511066.3 ± 5.51817.67 ± 5.51439.33 ± 9.61
λ = 306 nmAtrazine2000 ± 0.01971.3 ± 6.511666.67 ± 6.031402 ±11042.67 ± 3.79799 ± 5.29413.3 ± 5.13
Dimethoate2000 ± 0.01913 ± 3.611583.67 ± 3.061252.3 ± 3.21990.67 ± 1.53708.3 ± 5.51307.67 ± 5.69
Aqueous solution samples,catalytic process
λ = 254 nmAtrazine2000 ± 0.01959.3 ± 3.791616.3 ± 4.731244.67 ± 4.51994 ± 3.61738.67 ± 2.52ND
Dimethoate2000 ± 0.01843.3 ± 3.211410.3 ± 9.071111 ± 6.24945.67 ± 5.03527 ± 5.29ND
λ = 306 nmAtrazine2000 ± 0.01895 ± 5.291408 ± 4.581112 ± 2883.33 ± 3.21584 ± 17.58ND
Dimethoate2000 ± 0.01716.3 ± 11.021270.67 ± 7.021016.67 ± 5.03805.67 ± 4.73314.67 ± 6.66ND
Wastewater samples,non-catalytic process
λ = 254 nmAtrazine2144 ± 0.02037.3 ± 1.151726 ± 51432.3 ± 5.511150 ± 4.58874 ± 4.58391 ± 11.14
Dimethoate2041 ± 0.01911.67 ± 2.521559.67 ± 1.531150 ± 4.58971 ± 8.89749.33 ± 10.21345.67 ± 4.04
λ = 306 nmAtrazine2144 ± 0.01972 ± 4.581633.3 ± 8.141371.67 ± 9.241007 ± 5.57664 ± 4353.67 ± 4.62
Dimethoate2041 ± 0.01183.67 ± 4.041408 ± 3.611042.67 ± 14.58814.33 ± 2.89454.33 ± 7.02226. 67 ± 6.51
Wastewater samples,catalytic process
λ = 254 nmAtrazine2144 ± 0.01925 ± 7.211623.3 ± 4.041138.67 ± 6.81924 ± 3.46539 ± 7.21ND
Dimethoate2041 ± 0.01811.3 ± 2.891406.67 ± 5.511015.67 ± 3.21855 ± 3.46324.33 ± 4.16ND
λ = 306 nmAtrazine2144 ± 0.01936.3 ± 4.161336.3 ± 4.161064.67 ± 4.16804.67 ± 2.52459 ± 4.46ND
Dimethoate2041 ± 0.01644 ± 31175.3 ± 3.21892 ± 1.73592.33 ± 6.11266 ± 7ND
Agriculture wastewater samples,non-catalytic process
λ = 254 nmAtrazine2144 ± 0.02023.3 ± 2.311939.3 ± 4.161643.67 ± 2.521522.3 ± 5.511307 ± 5.29779.3 ± 351.9
Dimethoate2184 ± 0.02006.3 ± 3.211853.3 ± 3.511613 ± 4.581416 ± 4.581126.3 ± 12.01861.67 ± 6.51
λ = 306 nmAtrazine2144 ± 0.01993 ± 2.651883.3 ± 4.931587.3 ± 4.731403.3 ± 3.511144 ± 3903 ± 2.65
Dimethoate2184 ± 0.01890.67 ± 7.091772 ± 21474 ± 4.581255.67 ± 2.08989 ± 5.89409 ± 3.61
Agriculture wastewater samples,catalytic process
λ = 254 nmAtrazine2144 ± 0.01882 ± 5.201534 ± 3.611062.3 ± 8.08884.3 ± 2.52423 ± 4.5839.33333
Dimethoate2184 ± 0.01778.3 ± 7.371108 ± 6.56838.67 ± 6.51555 ± 3.61NDND
λ = 306 nmAtrazine2144 ± 0.01730.3 ± 3.061304.67 ± 3.51988 ± 4.58773 ± 3339 ± 2ND
Dimethoate2184 ± 0.01626.3 ± 4.51985.3 ± 3.79764.67 ± 2.31416.33 ± 5.96130.33 ± 8.33ND
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EL-Saeid, M.H.; Alotaibi, M.O.; Alshabanat, M.; AL-Anazy, M.M.; Alharbi, K.R.; Altowyan, A.S. Impact of Photolysis and TiO2 on Pesticides Degradation in Wastewater. Water 2021, 13, 655. https://doi.org/10.3390/w13050655

AMA Style

EL-Saeid MH, Alotaibi MO, Alshabanat M, AL-Anazy MM, Alharbi KR, Altowyan AS. Impact of Photolysis and TiO2 on Pesticides Degradation in Wastewater. Water. 2021; 13(5):655. https://doi.org/10.3390/w13050655

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EL-Saeid, Mohamed H., Modhi. O. Alotaibi, Mashael Alshabanat, Murefah Mana AL-Anazy, Khadijah R. Alharbi, and Abeer S. Altowyan. 2021. "Impact of Photolysis and TiO2 on Pesticides Degradation in Wastewater" Water 13, no. 5: 655. https://doi.org/10.3390/w13050655

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