Clean Technologies

2024

Jump to: 2023, 2022

28 pages, 6565 KiB

Open AccessArticle

Hybrid Electrocoagulation–Adsorption Process for Montelukast Sodium Removal from Water

by Sayedali Mirkhalafi, Khalid S. Hashim, Osamah Al-Hashimi and Ali Majdi

Clean Technol. 2024, 6(4), 1537-1564; https://doi.org/10.3390/cleantechnol6040074 - 20 Nov 2024

Viewed by 755

Abstract

This study addresses the significant environmental challenge of pharmaceutical pollutants by demonstrating the effectiveness of a hybrid electrocoagulation–adsorption (EC-A) technique for removing Montelukast Sodium (MS) from contaminated water. The research was conducted in three stages—adsorption, electrocoagulation, and adsorption using the residual water from [...] Read more.

This study addresses the significant environmental challenge of pharmaceutical pollutants by demonstrating the effectiveness of a hybrid electrocoagulation–adsorption (EC-A) technique for removing Montelukast Sodium (MS) from contaminated water. The research was conducted in three stages—adsorption, electrocoagulation, and adsorption using the residual water from the electrocoagulation process. The adsorbent materials were characterised using various analytical techniques: X-ray Diffraction (XRD) for determining the crystalline structure, Energy-Dispersive X-ray Spectroscopy (EDX) for elemental composition, Scanning Electron Microscopy (SEM) for surface morphology, and Fourier Transform Infrared Spectroscopy (FTIR) for identifying functional groups before and after interaction with the pollutants. The adsorption phase achieved optimal results at a pH of 3 and a contact time of 120 min, with a maximum removal efficiency of 99.5% for a starting MS concentration of 50 mg/L using Calcium Ferric Oxide–Silica Sand (CFO-SS) adsorbent. The electrocoagulation phase showed a 97% removal efficiency with a pH of 11, a current density of 20 mA, and a 5 mm electrode distance, achieved in just 20 min. Finally, the combined EC-A process, with the pH of residual water adjusted to 3, further enhanced the removal efficiency to 74%, highlighting the method’s potential for pharmaceutical contaminant removal. These findings underscore the potential of the EC-A technique as a highly effective and adaptable solution for mitigating pharmaceutical contaminants in water. Full article

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26 pages, 10706 KiB

Open AccessArticle

Ammonium Removal in Wastewater Treatments by Adsorbent Geopolymer Material with Granite Wastes: Full-Scale Validation

by M. Otero, L. Freire, S. Gómez-Cuervo and C. Ávila

Clean Technol. 2024, 6(1), 339-364; https://doi.org/10.3390/cleantechnol6010017 - 7 Mar 2024

Viewed by 2498

Abstract

Elevated ammonium (NH₄⁺) concentrations in untreated waterways contribute to eutrophication and dissolved oxygen depletion. Geopolymer (GP) materials are introduced as sustainable, straightforward operation and low-cost option for pollutant adsorption through ion exchange mechanism. In the present study, a porous metakaolin-based [...] Read more.

Elevated ammonium (NH₄⁺) concentrations in untreated waterways contribute to eutrophication and dissolved oxygen depletion. Geopolymer (GP) materials are introduced as sustainable, straightforward operation and low-cost option for pollutant adsorption through ion exchange mechanism. In the present study, a porous metakaolin-based geopolymer with granite waste additions was synthetized, characterised and validated as adsorbent material for NH₄⁺ pollution in water. At this point, treatments to reduce GP alkalis leaching were also considered to comply with the water discharge regulations. The adsorption mechanism was analysed by Redlich-Peterson isotherm model concluding that NH₄⁺ was disposed on the GP surface as a monolayer with strong physical-chemical attraction between molecules. Kinetics of the process followed the Weber-Morris rate equation being the intraparticle diffusion the limiting process. Continuous experiments at lab-scale suggested a maximum removal of 97% during the first hours and an adsorption capacity (q) of 25.24 mg/g. Additionally, as a main novelty of the work, the GP was validated in a full-scale pilot plant monitoring pH, electrical conductivity and NH₄⁺ concentration. The obtained data revealed that the GP is high selective in a real wastewater stream and removed 81% of NH₄⁺, higher adsorption values than those reported for natural and some synthetic zeolites. Full article

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2023

Jump to: 2024, 2022

13 pages, 746 KiB

Open AccessArticle

Mathematical Modeling of Particle Terminal Velocity for Improved Design of Clarifiers, Thickeners and Flotation Devices for Wastewater Treatment

by Dario Friso

Clean Technol. 2023, 5(3), 921-933; https://doi.org/10.3390/cleantechnol5030046 - 17 Jul 2023

Cited by 1 | Viewed by 2214

Abstract

The prediction of the terminal velocity of a single spherical particle is essential to realize mathematical modeling useful for the design and adjustment of separators used in wastewater treatment. For non-spherical and non-single particles, terminal velocity can be traced back to that of [...] Read more.

The prediction of the terminal velocity of a single spherical particle is essential to realize mathematical modeling useful for the design and adjustment of separators used in wastewater treatment. For non-spherical and non-single particles, terminal velocity can be traced back to that of single spheres using coefficients and Kynch’s theory, respectively. Because separation processes can involve small or large particles and can be carried out using gravity, as with clarifiers/thickeners, or by centrifugation in centrifuges where the acceleration can exceed 10,000× g, the Reynolds number of the particle can be highly variable, ranging from 0.1 to 200,000. The terminal velocity depends on the drag coefficient, which depends, in turn, on the Reynolds number containing the terminal velocity. Because of this, to find the terminal velocity formula, it is preferable to look first for a relationship between the drag coefficient and the Archimedes number which does not contain the terminal velocity. Formulas already exist expressing the relationship between the drag coefficient and the Archimedes number, from which the relationship between the terminal velocity and the Archimedes number may be derived. To improve the accuracy obtained by these formulas, a new relationship was developed in this study, using dimensional analysis, which is valid for Reynolds number values between 0.1 and 200,000. The resulting mean relative difference, compared to the experimental standard drag curve, was only 1.44%. This formula was developed using the logarithms of dimensionless numbers, and the unprecedented accuracy obtained with this method suggested that an equally accurate formula for the drag coefficient could also be obtained with respect to the Reynolds number. Again, the resulting level of accuracy was unprecedentedly high, with a mean relative difference of 1.77% for Reynolds number values between 0.1 and 200,000. Full article

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13 pages, 3270 KiB

Open AccessArticle

Mercury Removal from Mining Wastewater by Phytoaccumulation in Autochthonous Aquatic Plant Species

by Franco Hernan Gomez, Maria Cristina Collivignarelli, Ahmed Mohammad Nafea Masoud, Marco Carnevale Miino, Kelly Cristina Torres, Jesus Antonio Quintero, Sabrina Sorlini and Mentore Vaccari

Clean Technol. 2023, 5(3), 839-851; https://doi.org/10.3390/cleantechnol5030041 - 27 Jun 2023

Cited by 3 | Viewed by 2700

Abstract

Mining wastewater (MWW) can contain mercury in high concentrations. In this study, four autochthonous aquatic plant species (Eichhornia Crassipes—EC, Marsilea Quadrifolia—MQ, Ludwigia Helminthorrhiza—LH, and Lemna Minor—LM) were identified and tested for phytoaccumulation of total mercury (THg). To better [...] Read more.

Mining wastewater (MWW) can contain mercury in high concentrations. In this study, four autochthonous aquatic plant species (Eichhornia Crassipes—EC, Marsilea Quadrifolia—MQ, Ludwigia Helminthorrhiza—LH, and Lemna Minor—LM) were identified and tested for phytoaccumulation of total mercury (THg). To better study the accumulation phenomenon and macrophyte responses, this work has been divided into three phases, and pilot-scale reactors have been used to simulate real conditions. The results highlighted that, in case of 15 µg_THg,fed, the bioconcentration factor (BCF) was significantly higher in EC (19.04) and LH (18.41) with respect to MQ and LM (almost six times and two times higher, respectively). EC granted the best results in terms of THg accumulation (50.90%) and lower evapotranspiration of THg phenomenon with respect to LH. A significant decrease of the BCF (from 23.45 to 21.98) and an increase of the TF (from 0.23 up to 0.73) after 42 d highlighted that a breaking-time in terms of THg accumulation was reached due to the deterioration of the roots. In terms of the kinetics of THg removal by bioaccumulation, an HLT of 69.31 d was found, which is more than the breaking-time of the EC system, proving that a periodic replacement of exhausted macrophytes is required to obtain a higher percentage of THg removal. Full article

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18 pages, 6026 KiB

Open AccessArticle

Efficient Adsorption and Catalytic Reduction of Phenol Red Dye by Glutaraldehyde Cross-Linked Chitosan and Its Ag-Loaded Catalysts: Materials Synthesis, Characterization and Application

by Chiara Concetta Siciliano, Van Minh Dinh, Paolo Canu, Jyri-Pekka Mikkola and Santosh Govind Khokarale

Clean Technol. 2023, 5(2), 466-483; https://doi.org/10.3390/cleantechnol5020024 - 6 Apr 2023

Cited by 1 | Viewed by 3069

Abstract

In this study, glutaraldehyde cross-linked chitosan support, as well as the catalysts obtained after loading Ag metal (Ag/Chitosan), were synthesised and applied for adsorption and reduction of phenol red dye in an aqueous solution. The Ag/chitosan catalysts were characterised by X-ray diffraction (XRD), [...] Read more.

In this study, glutaraldehyde cross-linked chitosan support, as well as the catalysts obtained after loading Ag metal (Ag/Chitosan), were synthesised and applied for adsorption and reduction of phenol red dye in an aqueous solution. The Ag/chitosan catalysts were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and inductively coupled plasma-optical emission spectrometry (ICP-OES) analysis techniques. The catalytic reduction and adsorption performance of phenol red dye with Ag/chitosan and cross-linked chitosan, respectively, was performed at ambient reaction conditions. The reduction of dye was carried out using sodium borohydride (NaBH₄) as the reducing agent, while the progress of adsorption and reduction study was monitored with ultraviolet-visible (UV-vis) spectrophotometry technique. The reduction of the phenol red dye varied with the amount of catalyst, the concentration of NaBH₄, Ag metal loading, reaction temperature, phenol red dye concentration and initial pH of the dye solution. The dye solution with a nearly-neutral pH (6.4) allowed efficient adsorption of the dye, while acidic (pH = 4) and alkaline (pH = 8, 11, 13.8) solutions showed incomplete or no adsorption of dye. The reusability of the Ag/chitosan catalyst was applied for the complete reduction of the dye, where no significant loss of catalytic activity was observed. Hence, the applicability of cross-linked chitosan and Ag/catalyst was thus proven for both adsorption and reduction of phenol red dye in an aqueous solution and can be applied for industrial wastewater treatment. Full article

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2022

Jump to: 2024, 2023

34 pages, 2075 KiB

Open AccessReview

The Combined Implementation of Electrocoagulation and Adsorption Processes for the Treatment of Wastewaters

by Nuno S. Graça and Alírio E. Rodrigues

Clean Technol. 2022, 4(4), 1020-1053; https://doi.org/10.3390/cleantechnol4040063 - 14 Oct 2022

Cited by 16 | Viewed by 5702

Abstract

Effluent treatment and reuse are essential in order to address the global problem of water scarcity. Additionally, improving the quality of treated wastewater is necessary to reduce its adverse effects on natural water resources and, consequently, on human health. Electrocoagulation and adsorption have [...] Read more.

Effluent treatment and reuse are essential in order to address the global problem of water scarcity. Additionally, improving the quality of treated wastewater is necessary to reduce its adverse effects on natural water resources and, consequently, on human health. Electrocoagulation and adsorption have been successfully applied separately to treat different wastewaters. Each method has unique benefits, drawbacks, and parameters that affect the effectiveness of treatment. A review of both processes, including their theoretical principles, the effect of operating conditions, and practical applications, is presented to provide an overview of their capabilities. The combination of electrocoagulation and adsorption in a combined process can be used to amplify the advantages of each process while mitigating their limitations. In the present work, the combined process is analyzed in terms of its principles, applications, and integration in a circular economy model. Full article

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28 pages, 1313 KiB

Open AccessArticle

Circular Water Economy in the EU: Findings from Demonstrator Projects

by Yahya Qtaishat, Jan Hofman and Kemi Adeyeye

Clean Technol. 2022, 4(3), 865-892; https://doi.org/10.3390/cleantechnol4030054 - 7 Sep 2022

Cited by 13 | Viewed by 6042

Abstract

Circular economy (CE) for water aims to maximise value derived from water, processes, and practices. As a result, the recovery of wastewater and renewable water resources is used to offset the exploitation and impact of abstracting new water resources. New regulations such as [...] Read more.

Circular economy (CE) for water aims to maximise value derived from water, processes, and practices. As a result, the recovery of wastewater and renewable water resources is used to offset the exploitation and impact of abstracting new water resources. New regulations such as the new circular economy action plan by the European Commission are emerging to promote circularity within the Green Deal agenda. However, there is still a need for research and practical insights into the interaction and integration of CE for water within existing policies and regulations, and its practical application specifically at the project level. This paper presents findings from demonstrator cases used to explore the opportunities and constraints in the policy, process, and procedural frameworks that govern water circularity in important sectors in Europe. Desk reviews are used to examine and compare European legislation against national and regional legislative frameworks within the different member states. Interviews and demonstrator project feedback enabled the exploration of the policy and value constraints at the project level. The findings provide unique insights into the policy and legislative enablers for and barriers to implementing CE for water in key sectors and specifically at the project level. The paper concludes with a five-point route map for new and revised policies and regulations targeting improved uptake of circular water technologies in Europe. Full article

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13 pages, 1946 KiB

Open AccessArticle

Efficient Management of Sewage Sludge from Urban Wastewaters with the Addition of Inorganic Waste: Focus on Rheological Properties

by Andreia F. Santos, Abel G. M. Ferreira and Margarida J. Quina

Clean Technol. 2022, 4(3), 841-853; https://doi.org/10.3390/cleantechnol4030052 - 1 Sep 2022

Cited by 5 | Viewed by 3230

Abstract

Sewage sludge (SS) from urban wastewater treatment is still an environmental, economic, and social problem. Current SS management is not consensual, and more alternatives are required to recover some valuable compounds, such as nutrients and organic matter. This study investigates the use of [...] Read more.

Sewage sludge (SS) from urban wastewater treatment is still an environmental, economic, and social problem. Current SS management is not consensual, and more alternatives are required to recover some valuable compounds, such as nutrients and organic matter. This study investigates the use of green liquor dregs from the pulp and paper industry—GLDs—as an adjuvant of drying, to develop a product for agronomic applications, focusing on the rheological behavior. The rheological properties were assessed for anaerobically digested sludge (ADS). The limit viscosity of raw ADS was about 0.005 Pa·s in the case of 5% TSs (total solids) increasing to 0.51 Pa·s for 20% TSs. From the oscillatory tests, the ideal viscous flow below 10% TSs was observed, whereas a viscoelastic–solid behavior was detected for a higher concentration of TSs. The addition of GLDs to the ADS reduced the consistency index, reducing the shear resistance of the material. Rheological assays showed that GLDs may facilitate sludge handling (e.g., extrusion) from the dewatering unit to the dryer. Overall, the addition of GLDs to ADS showed to be a viable option for drying and subsequent soil application. Reusing both residues promote the transition from a linear to a circular economy in the wastewater treatment sector. Full article

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13 pages, 2232 KiB

Open AccessArticle

Enhanced Sewage Sludge Drying with a Modified Solar Greenhouse

by Alice Sorrenti, Santo Fabio Corsino, Francesco Traina, Gaspare Viviani and Michele Torregrossa

Clean Technol. 2022, 4(2), 407-419; https://doi.org/10.3390/cleantechnol4020025 - 12 May 2022

Cited by 1 | Viewed by 4900

Abstract

This work reports the results obtained with an innovative configuration of a closed-static solar greenhouse for sludge drying. The novelty of the solar greenhouse configuration consisted in using a forced ventilation system to provide hot air for sludge drying and the utilization of [...] Read more.

This work reports the results obtained with an innovative configuration of a closed-static solar greenhouse for sludge drying. The novelty of the solar greenhouse configuration consisted in using a forced ventilation system to provide hot air for sludge drying and the utilization of solar irradiation for energy supply. Wet sewage sludge (97% humidity) was successfully dried up to a residual humidity close to 5% after 25 days during wintertime. The increase of the airflow rate supplied under the sludge bed improved the sludge drying rate. Moreover, the fraction of volatile suspended solids decreased from 70% to 41% after 13 days, indicating that air supply promoted the simultaneous stabilization of the sludge as a side-effect to the drying process. Overall, the specific energy consumption per ton of evaporated water was estimated to approximately 450 kWh/t, resulting in about 55% of energy demand lower than a conventional thermal drying system, while using only free solar energy. The achieved high weight reduction of up to 99% implies a noticeable reduction of the excess sludge handling costs, indicating that solar greenhouse drying is a highly interesting opportunity for sludge drying in medium-small sized WWTPs. Full article

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13 pages, 986 KiB

Open AccessArticle

Sorption of 71 Pharmaceuticals to Powder Activated Carbon for Improved Wastewater Treatment

by Maritha Hörsing, Henrik Rasmus Andersen, Roman Grabic, Jes la Cour Jansen and Anna Ledin

Clean Technol. 2022, 4(2), 296-308; https://doi.org/10.3390/cleantechnol4020017 - 25 Apr 2022

Cited by 1 | Viewed by 2804

Abstract

In this study, sorption distribution coefficients were determined for 71 pharmaceuticals, aiming to describe their sorption behavior to powder activated carbon (PAC). The data are expected to be applied when designing and upgrading wastewater treatment plants (WWTP) for improved removal of pharmaceuticals by [...] Read more.

In this study, sorption distribution coefficients were determined for 71 pharmaceuticals, aiming to describe their sorption behavior to powder activated carbon (PAC). The data are expected to be applied when designing and upgrading wastewater treatment plants (WWTP) for improved removal of pharmaceuticals by applying sorption to PAC as an additional removal technique. Sorption isotherms were determined for the pharmaceuticals over a concentration interval covering a wide range from 0.08 to 10 µg/L using PAC at a concentration of 10 mg/L. The best fitted sorption isotherms were used to calculate the distribution coefficients (K_d) and these were applied to estimate that the PAC doses needed to achieve a target concentration of 10 ng/L in the effluent. A target concentration was used since neither discharge limit values nor environmental quality standards in general have been defined for these compounds. Using a %-removal approach does not guarantee achievement of concentrations low enough to protect the water ecosystems. Some of the pharmaceuticals will be reduced by the addition of small amounts of PAC. Examples are atenolol, carbamazepine, citalopram, codeine, fluoxetine and ibuprofen. For others, e.g., oxazepam, an alternative treatment has to be considered since the requested dose is too high to be realistic for a target concentration of 10 ng/L. Full article

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