Molecules

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13 pages, 4006 KiB

Open AccessArticle

Response Surface Methodology: Photocatalytic Degradation Kinetics of Basic Blue 41 Dye Using Activated Carbon with TiO₂

by Emmanuel Kweinor Tetteh, Elorm Obotey Ezugbe, Dennis Asante-Sackey, Edward Kwaku Armah and Sudesh Rathilal

Molecules 2021, 26(4), 1068; https://doi.org/10.3390/molecules26041068 - 18 Feb 2021

Cited by 34 | Viewed by 3458

Abstract

Water decontamination still remains a major challenge to some developing countries not having centralized wastewater systems. Therefore, this study presents the optimization of photocatalytic degradation of Basic Blue 41 dye in an aqueous medium by an activated carbon (AC)-TiO₂ photocatalyst under UV [...] Read more.

Water decontamination still remains a major challenge to some developing countries not having centralized wastewater systems. Therefore, this study presents the optimization of photocatalytic degradation of Basic Blue 41 dye in an aqueous medium by an activated carbon (AC)-TiO₂ photocatalyst under UV irradiation. The mesoporous AC-TiO₂ synthesized by a sonication method was characterized by X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy for crystal phase identification and molecular bond structures, respectively. The efficiency of the AC-TiO₂ was evaluated as a function of three input variables viz. catalyst load (2–4 g), reaction time (15–45 min) and pH (6–9) by using Box-Behnken design (BBD) adapted from response surface methodology. Using color and turbidity removal as responses, a 17 run experiment matrix was generated by the BBD to investigate the interaction effects of the three aforementioned input factors. From the results, a reduced quadratic model was generated, which showed good predictability of results agreeable to the experimental data. The analysis of variance (ANOVA), signposted the selected models for color and turbidity, was highly significant (p < 0.05) with coefficients of determination (R²) values of 0.972 and 0.988, respectively. The catalyst load was found as the most significant factor with a high antagonistic impact on the process, whereas the interactive effect of reaction time and pH affected the process positively. At optimal conditions of catalyst load (2.6 g), reaction time (45 min), and pH (6); the desirability of 96% was obtained by a numerical optimization approach representing turbidity removal of 93% and color of 96%. Full article

(This article belongs to the Special Issue Advanced Materials and Technologies for Wastewater Treatment)

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18 pages, 1484 KiB

Open AccessArticle

Batch Studies of Phosphonate and Phosphate Adsorption on Granular Ferric Hydroxide (GFH) with Membrane Concentrate and Its Synthetic Replicas

by Tobias Reinhardt, Adriana Noelia Veizaga Campero, Ralf Minke, Harald Schönberger and Eduard Rott

Molecules 2020, 25(21), 5202; https://doi.org/10.3390/molecules25215202 - 9 Nov 2020

Cited by 6 | Viewed by 3279

Abstract

Phosphonates are widely used as antiscalants for softening processes in drinking water treatment. To prevent eutrophication and accumulation in the sediment, it is desirable to remove them from the membrane concentrate before they are discharged into receiving water bodies. This study describes batch [...] Read more.

Phosphonates are widely used as antiscalants for softening processes in drinking water treatment. To prevent eutrophication and accumulation in the sediment, it is desirable to remove them from the membrane concentrate before they are discharged into receiving water bodies. This study describes batch experiments with synthetic solutions and real membrane concentrate, both in the presence of and absence of granular ferric hydroxide (GFH), to better understand the influence of ions on phosphonate and phosphate adsorption. To this end, experiments were conducted with six different phosphonates, using different molar Ca:phosphonate ratios. The calcium already contained in the GFH plays an essential role in the elimination process, as it can be re-dissolved, and, therefore, increase the molar Ca:phosphonate ratio. (Hydrogen-)carbonate ions had a competitive effect on the adsorption of phosphonates and phosphate, whereas the influence of sulfate and nitrate ions was negligible. Up to pH 8, the presence of Ca^II had a positive effect on adsorption, probably due to the formation of ternary complexes. At pH > 8, increased removal was observed, with either direct precipitation of Ca:phosphonate complexes or the presence of inorganic precipitates of calcium, magnesium, and phosphate serving as adsorbents for the phosphorus compounds. In addition, the presence of (hydrogen-)carbonate ions resulted in precipitation of CaCO₃ and/or dolomite, which also acted as adsorbents for the phosphorus compounds. Full article

(This article belongs to the Special Issue Advanced Materials and Technologies for Wastewater Treatment)

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17 pages, 2594 KiB

Open AccessArticle

Removal of Zinc from Aqueous Solutions Using Lamellar Double Hydroxide Materials Impregnated with Cyanex 272: Characterization and Sorption Studies

by Nacera Boudaoud, Hafida Miloudi, Djamila Bouazza, Mehdi Adjdir, Abdelkader Tayeb, Agustin Fortuny, Hary Demey and Ana Maria Sastre

Molecules 2020, 25(6), 1263; https://doi.org/10.3390/molecules25061263 - 11 Mar 2020

Cited by 8 | Viewed by 3096

Abstract

Removal of heavy metals from wastewater is mandatory in order to avoid water pollution of natural reservoirs. In the present study, layered double hydroxide (LDH) materials were evaluated for removal of zinc from aqueous solutions. Materials thus prepared were impregnated with cyanex 272 [...] Read more.

Removal of heavy metals from wastewater is mandatory in order to avoid water pollution of natural reservoirs. In the present study, layered double hydroxide (LDH) materials were evaluated for removal of zinc from aqueous solutions. Materials thus prepared were impregnated with cyanex 272 using the dry method. These materials were characterized through X-ray diffraction (XRD), Fourier transform infrared (FTIR), and thermal analysis. Batch shaking adsorption experiments were performed in order to examine contact time and extraction capacity in the removal process. Results showed that the equilibrium time of Zn (II) extraction is about 4 h for Mg₂Al-CO₃ and Mg₂Al-CO₃-cyanex 272, 6 h for Zn₂Al-CO₃, and 24 h for Zn₂Al-CO₃-cyanex 272. The experimental equilibrium data were tested for Langmuir, and Freundlich isotherm models. Correlation coefficients indicate that experimental results are in a good agreement with Langmuir’s model for zinc ions. Pseudo-first, second-order, Elovich, and intraparticular kinetic models were used to describe kinetic data. It was determined that removal of Zn²⁺ was well-fitted by a second-order reaction kinetic. A maximum capacity of 280 mg/g was obtained by Zn₂Al-CO₃-cyanex 272. Full article

(This article belongs to the Special Issue Advanced Materials and Technologies for Wastewater Treatment)

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16 pages, 1581 KiB

Open AccessArticle

The Influence of COD Fraction Forms and Molecules Size on Hydrolysis Process Developed by Comparative OUR Studies in Activated Sludge Modelling

by Jakub Drewnowski, Bartosz Szeląg, Li Xie, Xi Lu, Mahesh Ganesapillai, Chinmoy Kanti Deb, Joanna Szulżyk-Cieplak and Grzegorz Łagód

Molecules 2020, 25(4), 929; https://doi.org/10.3390/molecules25040929 - 19 Feb 2020

Cited by 13 | Viewed by 3999

Abstract

The activated sludge models (ASMs) commonly used by the International Water Association (IWA) task group are based on chemical oxygen demand (COD) fractionations. However, the proper evaluation of COD fractions, which is crucial for modelling and especially oxygen uptake rate (OUR) predictions, is [...] Read more.

The activated sludge models (ASMs) commonly used by the International Water Association (IWA) task group are based on chemical oxygen demand (COD) fractionations. However, the proper evaluation of COD fractions, which is crucial for modelling and especially oxygen uptake rate (OUR) predictions, is still under debate. The biodegradation of particulate COD is initiated by the hydrolysis process, which is an integral part of an ASM. This concept has remained in use for over 30 years. The aim of this study was to verify an alternative, more complex, modified (Activated Sludge Model No 2d) ASM2d for modelling the OUR variations and novel procedure for the estimation of a particulate COD fraction through the implementation of the GPS-X software (Hydromantis Environmental Software Solutions, Inc., Hamilton, ON, Canada) in advanced computer simulations. In comparison to the original ASM2d, the modified model more accurately predicted the OUR behavior of real settled wastewater (SWW) samples and SWW after coagulation–flocculation (C–F). The mean absolute relative deviations (MARDs) in OUR were 11.3–29.5% and 18.9–45.8% (original ASM2d) vs. 9.7–15.8% and 11.8–30.3% (modified ASM2d) for the SWW and the C–F samples, respectively. Moreover, the impact of the COD fraction forms and molecules size on the hydrolysis process rate was developed by integrated OUR batch tests in activated sludge modelling. Full article

(This article belongs to the Special Issue Advanced Materials and Technologies for Wastewater Treatment)

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13 pages, 3547 KiB

Open AccessArticle

Nanocellulose and Polycaprolactone Nanospun Composite Membranes and Their Potential for the Removal of Pollutants from Water

by Hasbleidy Palacios Hinestroza, Hilary Urena-Saborio, Florentina Zurita, Aida Alejandra Guerrero de León, Gunasekaran Sundaram and Belkis Sulbarán-Rangel

Molecules 2020, 25(3), 683; https://doi.org/10.3390/molecules25030683 - 6 Feb 2020

Cited by 42 | Viewed by 5514

Abstract

A composite membrane based on polycaprolactone (PCL) and cellulose nanofibers (CNF) with different compositions was prepared using the electro-spinning method, with the objective of developing organic membranes with good mechanical properties to remove contaminants from water. Water is a resource of primary importance [...] Read more.

A composite membrane based on polycaprolactone (PCL) and cellulose nanofibers (CNF) with different compositions was prepared using the electro-spinning method, with the objective of developing organic membranes with good mechanical properties to remove contaminants from water. Water is a resource of primary importance for life and human activities. In this sense, cellulose obtained from agave bagasse and polycaprolactone nanofibers was used to prepare membranes that were tested by filtering tap water. The membranes obtained presented a porosity and structure on a nanometric scale. The water quality variables evaluated after filtration with the PCL/CNF membranes showed 100% turbidity removal, 100% conductivity, and heavy metal removal of the order of 75% to 99% for iron and chromium. CNF comprises biowaste derived from tequila production, and it has added value. Electro-spun CNF and PCL membranes can be applied as a “green” and eco-friendly filtration system for water purification. Full article

(This article belongs to the Special Issue Advanced Materials and Technologies for Wastewater Treatment)

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17 pages, 3155 KiB

Open AccessArticle

Characterization and Dimethyl Phthalate Flocculation Performance of the Cationic Polyacrylamide Flocculant P(AM-DMDAAC) Produced by Microwave-Assisted Synthesis

by Peng Zhang and Dong Qin Zhao

Molecules 2020, 25(3), 624; https://doi.org/10.3390/molecules25030624 - 31 Jan 2020

Cited by 15 | Viewed by 3741

Abstract

A composite flocculant P(AM–DMDAAC) was synthesized by the copolymerization of acrylamide (AM) and dimethyl diallyl ammonium chloride (DMDAAC). By using microwave (MV) assistance with ammonium persulfate as initiator, the synthesis had a short reaction time and yielded a product with good solubility. Fourier-transform [...] Read more.

A composite flocculant P(AM–DMDAAC) was synthesized by the copolymerization of acrylamide (AM) and dimethyl diallyl ammonium chloride (DMDAAC). By using microwave (MV) assistance with ammonium persulfate as initiator, the synthesis had a short reaction time and yielded a product with good solubility. Fourier-transform infrared spectroscopy, scanning electron microscopy, and differential thermal analysis–thermogravimetric analysis were employed to determine the structure and morphology of P(AM–DMDAAC). The parameters affecting the intrinsic viscosity of P(AM–DMDAAC), such as MV time, mass ratio of DMDAAC to AM, bath time, reaction temperature, pH value, and the dosages of ammonium persulfate initiator, EDTA, sodium benzoate, and urea were examined. Results showed that the optimum synthesis conditions were MV time of 1.5 min, m(DMDAAC):m(AM) of 4:16, 0.5 wt‰ initiator, 0.4 wt‰ EDTA, 0.3 wt‰ sodium benzoate, 2 wt‰ urea, 4 h bath time, reaction temperature of 40 °C, and pH of 2. The optimal dimethyl phthalate (DMP) removal rate can reach 96.9% by using P(AM–DMDAAC), and the P(AM–DMDAAC) had better flocculation than PAM, PAC, and PFS. Full article

(This article belongs to the Special Issue Advanced Materials and Technologies for Wastewater Treatment)

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18 pages, 13893 KiB

Open AccessArticle

The Impact of Different Powdered Mineral Materials on Selected Properties of Aerobic Granular Sludge

by Joanna Czarnota, Adam Masłoń, Monika Zdeb and Grzegorz Łagód

Molecules 2020, 25(2), 386; https://doi.org/10.3390/molecules25020386 - 17 Jan 2020

Cited by 9 | Viewed by 3508

Abstract

This study aimed to evaluate and compare the physical, chemical and biological properties of aerobic granular sludge from reactors with the addition of different powdered mineral materials. These properties have a significant impact on the efficiency of systems in which the biomass in [...] Read more.

This study aimed to evaluate and compare the physical, chemical and biological properties of aerobic granular sludge from reactors with the addition of different powdered mineral materials. These properties have a significant impact on the efficiency of systems in which the biomass in granular form is used. Four identical granular sequencing batch reactors (GSBRs) were adopted for the research performed on a laboratory scale (R1—control reactor; R2, R3 and R4—with materials, PK, PG and PL respectively). The results indicate that the addition of powdered mineral materials improved the properties of biomass in reactors. The SVI₅/SVI₃₀ ratio values were significantly lower in the reactors with added materials (approx. 1.3 ± 0.3). The mean values of the sludge volume index at 30 min were the lowest in the R2 (39.8 ± 8.6 mL/g) and R4 (32.8 ± 10.7 mL/g) reactors. The settling velocity of biomass was the highest in the R2 reactor (15.4 ± 6.1 m/h). In the early days of the study, the highest extracellular polymeric substances (EPS) content was found in the biomass from the reactors to which the materials with higher Ca and Mg content were added (380.18–598.30 mg/g MLVSS). The rate of specific oxygen uptake (SOUR) by biomass indicated an insufficient biomass content in the R1 reactor—to 7.85 mg O₂/(g MLVSS?h)—while in the reactors with materials, the SOUR values were at the higher levels. Full article

(This article belongs to the Special Issue Advanced Materials and Technologies for Wastewater Treatment)

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13 pages, 4782 KiB

Open AccessArticle

Fe-Loaded MOF-545(Fe): Peroxidase-Like Activity for Dye Degradation Dyes and High Adsorption for the Removal of Dyes from Wastewater

by Chuang Zhang, Haichao Li, Chen Li and Zhengqiang Li

Molecules 2020, 25(1), 168; https://doi.org/10.3390/molecules25010168 - 31 Dec 2019

Cited by 51 | Viewed by 6473

Abstract

Methods to remove dye pollutants with natural enzyme, like horseradish peroxidase (HRP), are still limited due to high costs and low stability levels. The development of such a method with similar enzymatic activity is important and could be helpful in wastewater disposal. A [...] Read more.

Methods to remove dye pollutants with natural enzyme, like horseradish peroxidase (HRP), are still limited due to high costs and low stability levels. The development of such a method with similar enzymatic activity is important and could be helpful in wastewater disposal. A metal organic framework material, Fe-loaded MOF-545 (Fe), was synthesized in our study as a new way to remove dyes due to its peroxidase-like activity. The structural characterizations of Fe-loaded MOF-545(Fe) was investigated using scanning electron microscopy (SEM), UV-Vis absorption spectra, and X-ray diffraction (XRD). The peroxidase-like (POD-like) activity of Fe-loaded MOF-545(Fe) was investigated under different pH and temperature conditions. Because of the Fe added into the MOF-545 structure, the absorption of Fe-loaded MOF-545(Fe) for acid (anionic) dyes (methyl orange (MO)) was better than for basic (cationic) dyes (methylene blue (MB)). The Fe-loaded MOF-545(Fe) could give a significant color fading for MO and MB over a short time (about two hours) with peroxidase-like activity. The remarkable capacity of Fe-loaded MOF-545(Fe) to remove the MO or MB is due to not only physical adsorption, but also degradation of the MO and MB with POD-like activity. Therefore, Fe-loaded MOF-545(Fe) has significant potential regarding dye removal from wastewater. Full article

(This article belongs to the Special Issue Advanced Materials and Technologies for Wastewater Treatment)

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22 pages, 6191 KiB

Open AccessArticle

Enhanced Heavy Metal Removal from Acid Mine Drainage Wastewater Using Double-Oxidized Multiwalled Carbon Nanotubes

by Carolina Rodríguez and Eduardo Leiva

Molecules 2020, 25(1), 111; https://doi.org/10.3390/molecules25010111 - 27 Dec 2019

Cited by 62 | Viewed by 5248

Abstract

Due to the unique properties of carbon nanotubes (CNTs), they have attracted great research attention as an emergent technology in many applications including water and wastewater treatment. However, raw CNTs have few functional groups, which limits their use in heavy metal removal. Nevertheless, [...] Read more.

Due to the unique properties of carbon nanotubes (CNTs), they have attracted great research attention as an emergent technology in many applications including water and wastewater treatment. However, raw CNTs have few functional groups, which limits their use in heavy metal removal. Nevertheless, their removal properties can be improved by oxidation processes that modify its surface. In this study, we assessed the capacity of oxidized and double-oxidized multiwalled carbon nanotubes (MWCNTs) to remove heavy metals ions from acidic solutions. The MWCNTs were tested for copper (Cu), manganese (Mn), and zinc (Zn) removal, which showed an increment of 79%, 78%, and 48%, respectively, with double-oxidized MWCNTs compared to oxidized MWCNTs. Moreover, the increase in pH improved the sorption capacity for all the tested metals, which indicates that the sorption potential is strongly dependent on the pH. The kinetic adsorption process for three metals can be described well with a pseudo-second-order kinetic model. Additionally, in multimetallic waters, the sorption capacity decreases due to the competition between metals, and it was more evident in the removal of Zn, while Cu was less affected. Besides, XPS analysis showed an increase in oxygen-containing groups on the MWCNTs surface after oxidation. Finally, these analyses showed that the chemical interactions between heavy metals and oxygen-containing groups are the main removal mechanism. Overall, these results contribute to a better understanding of the potential use of CNTs for water treatment. Full article

(This article belongs to the Special Issue Advanced Materials and Technologies for Wastewater Treatment)

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11 pages, 4689 KiB

Open AccessArticle

Evaluation of the Photocatalytic Activity of a Cordierite-Honeycomb-Supported TiO₂ Film with a Liquid–Solid Photoreactor

by Francesco Pellegrino, Nicola De Bellis, Fabrizio Ferraris, Marco Prozzi, Marco Zangirolami, Jasmine R. Petriglieri, Ilaria Schiavi, Alessandra Bianco-Prevot and Valter Maurino

Molecules 2019, 24(24), 4499; https://doi.org/10.3390/molecules24244499 - 9 Dec 2019

Cited by 9 | Viewed by 3963

Abstract

Anatase nanoparticles in suspension have demonstrated high photoactivity that can be exploited for pollutant removal in water phases. The main drawback of this system is the difficulty of recovering (and eventually reusing) the nanoparticles after their use, and the possible interference of inorganic [...] Read more.

Anatase nanoparticles in suspension have demonstrated high photoactivity that can be exploited for pollutant removal in water phases. The main drawback of this system is the difficulty of recovering (and eventually reusing) the nanoparticles after their use, and the possible interference of inorganic salts (e.g., sulfates) that can reduce the performance of the photocatalyst. The present work describes the development of a cordierite-honeycomb-supported TiO₂ film to eliminate the problems of catalyst recovery. The catalyst was then tested against phenol in the presence of increasing concentrations of sulfates in a specially developed recirculating modular photoreactor, able to accommodate the supported catalyst and scalable for application at industrial level. The effect of SO₄²⁻ was evaluated at different concentrations, showing a slight deactivation only at very high sulfate concentration (≥3 g L⁻¹). Lastly, in the framework of the EU project Project Ô, the catalyst was tested in the treatment of real wastewater from a textile company containing a relevant concentration of sulfates, highlighting the stability of the photocatalyst. Full article

(This article belongs to the Special Issue Advanced Materials and Technologies for Wastewater Treatment)

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13 pages, 3196 KiB

Open AccessArticle

Improving Water Permeability of Hydrophilic PVDF Membrane Prepared via Blending with Organic and Inorganic Additives for Humic Acid Separation

by Nasrul Arahman, Sri Mulyati, Afrillia Fahrina, Syawaliah Muchtar, Mukramah Yusuf, Ryosuke Takagi, Hideto Matsuyama, Nik Abdul Hadi Nordin and Muhammad Roil Bilad

Molecules 2019, 24(22), 4099; https://doi.org/10.3390/molecules24224099 - 13 Nov 2019

Cited by 33 | Viewed by 4888

Abstract

The removal of impurities from water or wastewater by the membrane filtration process has become more reliable due to good hydraulic performance and high permeate quality. The filterability of the membrane can be improved by having a material with a specific pore structure [...] Read more.

The removal of impurities from water or wastewater by the membrane filtration process has become more reliable due to good hydraulic performance and high permeate quality. The filterability of the membrane can be improved by having a material with a specific pore structure and good hydrophilic properties. This work aims at preparing a polyvinylidene fluoride (PVDF) membrane incorporated with phospholipid in the form of a 2-methacryloyloxyethyl phosphorylcholine, polymeric additive in the form of polyvinylpyrrolidone, and its combination with inorganic nanosilica from a renewable source derived from bagasse. The resulting membrane morphologies were analyzed by using scanning electron microscopy. Furthermore, atomic force microscopy was performed to analyze the membrane surface roughness. The chemical compositions of the resulting membranes were identified using Fourier transform infrared. A lab-scale cross-flow filtration system module was used to evaluate the membrane’s hydraulic and separation performance by the filtration of humic acid (HA) solution as the model contaminant. Results showed that the additives improved the membrane surface hydrophilicity. All modified membranes also showed up to five times higher water permeability than the pristine PVDF, thanks to the improved structure. Additionally, all membrane samples showed HA rejections of 75–90%. Full article

(This article belongs to the Special Issue Advanced Materials and Technologies for Wastewater Treatment)

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13 pages, 1195 KiB

Open AccessArticle

Removal of Ammonia from the Municipal Waste Treatment Effluents using Natural Minerals

by Przemysław Seruga, Małgorzata Krzywonos, Justyna Pyżanowska, Agnieszka Urbanowska, Halina Pawlak-Kruczek and Łukasz Niedźwiecki

Molecules 2019, 24(20), 3633; https://doi.org/10.3390/molecules24203633 - 9 Oct 2019

Cited by 73 | Viewed by 5213

Abstract

Due to various ecological problems, it is required to remove the ammonia nitrogen from wastewater. Industrial wastewater that was not subjected to any purification was used in this study, while most processes described in the literature were carried out using synthetically prepared solutions. [...] Read more.

Due to various ecological problems, it is required to remove the ammonia nitrogen from wastewater. Industrial wastewater that was not subjected to any purification was used in this study, while most processes described in the literature were carried out using synthetically prepared solutions. The study investigated the removal of ammonium ions using ion exchange on various commercial minerals, in 3 h long batch ion-exchange experiments. Furthermore, research on the sodium chloride activation of the selected mineral was conducted. The screening of the mineral with the highest removal potential was conducted taking into account the adsorption capacity (q) and maximal removal efficiency (E), based on the NH₄⁺ ions changes determined using the selective electrode and spectrophotometric cuvette tests. The highest adsorption capacity (q = 4.92 mg/g) of ammonium ions with the maximum removal efficiency (52.3%) was obtained for bentonite, with a 0–0.05 mm particle size. After pretreatment with a 1 mol/L NaCl solution, maximum efficiency increments were observed (55.7%). The Langmuir adsorption isotherm corresponds well with the equilibrium adsorption data (R² from 0.97 to 0.98), while the Freundlich model was found to be mismatched (R² = 0.77). Based on these results it was concluded that natural sorbents may be effectively applied in wastewater treatment. It can be observed that as the size of sorbent particles gets lower, the adsorption capacity, as well as the removal efficiency, gets higher. The bentonite pretreatment with the NaCl solution did not result in the expected efficiency improvement. The 2 mol/L solution affected about 3.5% of the removal efficiency yield. Full article

(This article belongs to the Special Issue Advanced Materials and Technologies for Wastewater Treatment)

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15 pages, 1439 KiB

Open AccessArticle

The High Efficiency of Anionic Dye Removal Using Ce-Al₁₃/Pillared Clay from Darbandikhan Natural Clay

by Bakhtyar K. Aziz, Dler M. Salh, Stephan Kaufhold and Pieter Bertier

Molecules 2019, 24(15), 2720; https://doi.org/10.3390/molecules24152720 - 26 Jul 2019

Cited by 16 | Viewed by 3673

Abstract

Natural clay from Darbandikhan (DC) was evaluated in its natural form, after acid activation (ADC), and after pillaring (PILDC) as a potential adsorbent for the adsorption of methyl orange (MO) as a model anionic dye adsorbate. The effect of different clay treatments was [...] Read more.

Natural clay from Darbandikhan (DC) was evaluated in its natural form, after acid activation (ADC), and after pillaring (PILDC) as a potential adsorbent for the adsorption of methyl orange (MO) as a model anionic dye adsorbate. The effect of different clay treatments was investigated using X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), Scanning Electron Microscope (SEM) and Fourier-Transform Infrared Spectroscopy (FT-IR), and N₂ physisorption analysis. Both acid activation and pillaring resulted in a significant increase in adsorption affinity, respectively. The adsorption favored acidic pH for the anionic dye (MO). The adsorption process was found to follow pseudo-second-order kinetics with activation energies of 5.9 and 40.1 kJ·mol⁻¹ for the adsorption of MO on ADC and PILDC, respectively, which are characteristic of physical adsorption. The adsorption isotherms (Langmuir, Redlich-Peterson and Freundlich) were fitted well to the experimental data. The specific surface area of the natural clay was very low (22.4 m²·g⁻¹) compared to high-class adsorbent materials. This value was increased to 53.2 m²·g⁻¹ by the pillaring process. Nevertheless, because of its local availability, the activated materials may be useful for the cleaning of local industrial wastewaters. Full article

(This article belongs to the Special Issue Advanced Materials and Technologies for Wastewater Treatment)

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8 pages, 1644 KiB

Open AccessArticle

Different Role of Bisulfite/Sulfite in UVC-S(IV)-O₂ System for Arsenite Oxidation in Water

by Tao Luo, Zhenhua Wang, Yi Wang, Zizheng Liu and Ivan P. Pozdnyakov

Molecules 2019, 24(12), 2307; https://doi.org/10.3390/molecules24122307 - 21 Jun 2019

Cited by 14 | Viewed by 3573

Abstract

It is of interest to use UV-sulfite based processes to degrade pollutants in wastewater treatment process. In this work, arsenic (As(III)) has been selected as a target pollutant to verify the efficacy of such a hypothesized process. The results showed that As(III) was [...] Read more.

It is of interest to use UV-sulfite based processes to degrade pollutants in wastewater treatment process. In this work, arsenic (As(III)) has been selected as a target pollutant to verify the efficacy of such a hypothesized process. The results showed that As(III) was quickly oxidized by a UV-sulfite system at neutral or alkaline pH and especially at pH 9.5, which can be mainly attributed to the generated oxysulfur radicals. In laser flash photolysis (LFP) experiments (λ_ex = 266 nm), the signals of SO₃^•− and e_aq⁻ generated by photolysis of sulfite at 266 nm were discerned. Quantum yields for photoionization of HSO₃⁻ (0.01) and SO₃²⁻ (0.06) were also measured. It has been established that e_aq⁻ does not react with SO₃²⁻, but reacts with HSO₃⁻ with a rate constant 8 × 10⁷ M⁻¹s⁻¹. Full article

(This article belongs to the Special Issue Advanced Materials and Technologies for Wastewater Treatment)

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13 pages, 3288 KiB

Open AccessArticle

Interaction of Arsenic Species with Organic Ligands: Competitive Removal from Water by Coagulation-Flocculation-Sedimentation (C/F/S)

by Muhammad Ali Inam, Rizwan Khan, Muhammad Akram, Sarfaraz Khan, Du Ri Park and Ick Tae Yeom

Molecules 2019, 24(8), 1619; https://doi.org/10.3390/molecules24081619 - 24 Apr 2019

Cited by 21 | Viewed by 3966

Abstract

The co-occurrence of arsenic (As) and organic ligands in water bodies has raised environmental concerns due to their toxicity and adverse effects on human health. The present study aims to elucidate the influences of hydrophobic/hydrophilic organic ligands, such as humic acid (HA) and [...] Read more.

The co-occurrence of arsenic (As) and organic ligands in water bodies has raised environmental concerns due to their toxicity and adverse effects on human health. The present study aims to elucidate the influences of hydrophobic/hydrophilic organic ligands, such as humic acid (HA) and salicylic acid (SA), on the interactive behavior of As species in water. Moreover, the competitive removal behaviors of As(III, V) species and total organic carbon (TOC) were systematically investigated by coagulation-flocculation-sedimentation (C/F/S) under various aqueous matrices. The results showed the stronger binding affinity of As(V) than As(III) species, with a higher complexation ability of hydrophobic ligands than hydrophilic. The media containing hydrophilic ligands require smaller ferric chloride (FC) doses to achieve the higher As(III, V) removal, while the optimum FC dose required for As(III) removal was found to be higher than that for As(V). Moreover, hydrophobic ligands showed higher TOC removal than hydrophilic ligands. The pronounced adverse effect of a higher concentration of hydrophobic ligands on the removal efficiencies of As(V) and TOC was observed. The adsorption of As(V) on Fe precipitates was better fitted with the Langmuir model but the Freundlich isotherm was more suitable for As(III) in the presence of hydrophilic SA. Moreover, TOC removal was substantially decreased in the As(V) system as compared to the As(III) system due to the dissolution of Fe precipitates at higher As(V) concentrations. The results of FC composite flocs demonstrated that the combined effect of oxidation, charge neutralization and adsorption played an important role in the removal of both toxicants during the C/F/S process. In summary, the findings of the present study provide insights into the fate, mobility and competitive removal behavior of As(III, V) species and organic ligands in the water treatment process. Full article

(This article belongs to the Special Issue Advanced Materials and Technologies for Wastewater Treatment)

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