Degradation and mineralization of sulcotrione and mesotrione in aqueous medium by the electro-Fenton process: a kinetic study

Introduction

The degradation and mineralization of two triketone (TRK) herbicides, including sulcotrione and mesotrione, by the electro-Fenton process (electro-Fenton using Pt anode (EF-Pt), electro-Fenton with BDD anode (EF-BDD) and anodic oxidation with BDD anode) were investigated in acidic aqueous medium.

Methods

The reactivity of both herbicides toward hydroxyl radicals was found to depend on the electron-withdrawing effect of the aromatic chlorine or nitro substituents. The degradation of sulcotrione and mesotrione obeyed apparent first-order reaction kinetics, and their absolute rate constants with hydroxyl radicals at pH?3.0 were determined by the competitive kinetics method.

Results and discussion

The hydroxylation absolute rate constant (k _abs) values of both TRK herbicides ranged from 8.20?×?10⁸ (sulcotrione) to 1.01?×?10⁹ (mesotrione) L?mol^?1?s^?1, whereas those of the TRK main cyclic or aromatic by-products, namely cyclohexane 1,3-dione , (2-chloro-4-methylsulphonyl) benzoic acid and 4-(methylsulphonyl)-2-nitrobenzoic acid, comprised between 5.90?×?10⁸ and 3.29?×?10⁹?L?mol^?1?s^?1. The efficiency of mineralization of aqueous solutions of both TRK herbicides was evaluated in terms of total organic carbon removal. Mineralization yields of about 97?C98% were reached in optimal conditions for a 6-h electro-Fenton treatment time.

Conclusions

The mineralization process steps involved the oxidative opening of the aromatic or cyclic TRK by-products, leading to the formation of short-chain carboxylic acids, and, then, of carbon dioxide and inorganic ions.     

Evaluation of the individuality of white rot macro fungus for the decolorization of synthetic dye

Introduction

A biosorbent was developed by simple dried Agaricus bisporus (SDAB) and effectively used for the biosorption of cationic dyes, Crystal Violet and Brilliant Green.

Materials and methods

For the evaluation of the biosorbent system, all the batch equilibrium parameters like pH, biomass dose, contact time, and temperature were optimized to determine the decolorization efficiency of the biosorbent. The maximum yields of dye removal were achieved at pH 4.0 for Crystal Violet (CV) and pH 5.0 for Brilliant Green (BG), which are closer to their natural pH also.

Result and discussion

Equilibrium was established at 60 and 40 min for CV and BG, respectively. Pseudo first-order, pseudo second-order, and intraparticle-diffusion kinetic models were studied at different temperatures. Isotherm models such as Freundlich, Langmuir, and Dubinin–Radushkevich were also studied. Biosorption processes were successfully described by Langmuir isotherm model and the pseudo second-order kinetic model.

Conclusions

The biosorption capacity of A. bisporus over CV and BG were found as 21.74 and 12.16 mg gm^?1. Thermodynamic parameters indicated that the CV and BG dye adsorption onto A. bisporus is spontaneous and exothermic in the single and ternary systems. Scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy were used for the surface morphology, crystalline structure of biosorbent, and dye–biosorbent interaction, respectively. This analysis of the biosorption data confirmed that these biosorption processes are ecofriendly and economical. Thus, this biomass system may be useful for the removal of contaminating cationic dyes.     

Highly efficient decolorization of Malachite Green by a novel Micrococcus sp. strain BD15

Purpose

Malachite Green (MG) is used for a variety of applications but is also known to be carcinogenic and mutagenic. In this study, a novel Micrococcus sp. (strain BD15) was observed to efficiently decolorize MG. The purposes of this study were to explore the optimal conditions for decolorization and to evaluate the potential use of this strain for MG decolorization.

Methods

Optical microscope and UV?Cvisible analyses were carried out to determine whether the decolorization was due to biosorption or biodegradation. A Plackett?CBurman design was employed to investigate the effect of various parameters on decolorization, and response surface methodology was then used to explore the optimal decolorization conditions. Kinetics analysis and antimicrobial activity tests were also performed.

Results

The results indicated that the decolorization by the strain was mainly due to biodegradation. Concentrations of MG, urea, and yeast extract and inoculum size had significantly positive effects on MG decolorization, while concentrations of CuCl₂ and MgCl₂, and temperature had significantly negative effects. The interaction between different parameters could significantly affect decolorization, and the optimal conditions for decolorization were 1.0 g/L urea, 0.9 g/L yeast extract, 100 mg/L MG, 0.1 g/L inoculums (dry weight), and incubation at 25.2°C. Under the optimal conditions, 96.9% of MG was removed by the strain within 1 h, which represents highly efficient microbial decolorization. Moreover, the kinetic data for decolorization fit a second-order model well, and the strain showed a good MG detoxification capability.

Conclusion

Based on the results of this study, we propose Micrococcus sp. strain BD15 as an excellent candidate strain for MG removal from wastewater.     

Equilibrium, kinetic and thermodynamic studies on the biosorption of reactive acid dye on Enteromorpha flexuosa and Gracilaria corticata

Purpose

Biosorption is an emerging, eco-friendly and economical method for treating the wastewater effluents. Compared to many other biological materials, algae biomass proved to be the better biosorbent due to the presence of cell wall polymers in them.

Methods

Algal biomasses namely Enteromorpha flexuosa and Gracilaria corticata were dried, crushed and used as biosorbents. Ponceau S, a diazo dye was used as a model adsorbate for the biosorption studies. The biosorbents were characterized by Scanning Electron Microscopy, FT-IR and zero point charge. Batch studies were performed by varying pH, biosorbent dosage and initial dye concentrations. Adsorption isotherms, kinetic and thermodynamic analyses were carried out. The effect of electrolytes was also studied. Batch desorption studies were also carried out using various reagents.

Results

Isotherm data were tested with Langmuir and Freundlich isotherm models and the results suggested that the Freundlich isotherm fitted the data well. Kinetic studies were performed with varying initial dye concentrations and the data were incorporated with pseudo first-order and pseudo second-order kinetic equations and was found that the studied biosorption processes followed pseudo second-order kinetic equation. Thermodynamic parameters were evaluated at three different temperatures 293?K, 300?K and 313?K. About 95% of the dye could be desorbed from both the biosorbents.

Conclusion

Both the algal biomasses had heterogeneous surfaces and followed pseudo second-order chemical kinetics. Thermodynamic parameters proved that the biosorption by both the biomasses were spontaneous, feasible and endothermic processes. Desorption studies proved the worth of the algal biomasses as biosorbents in industrial level.     

Evaluation of substrate removal kinetics for UASB reactors treating chlorinated ethanes

Purpose

Lack of focus on the treatment of wastewaters bearing potentially hazardous pollutants like 1,1,2 trichloroethane and 1,1,2,2 tetrachloroethane in anaerobic reactors has provided an impetus to undertake this study. The objective of this exercise was to quantify the behavior of upflow anaerobic sludge blanket reactors and predict their performance based on the overall organic substrate removal.

Methods

The reactors (wastewater-bearing TCA (R2), and wastewater-bearing TeCA (R3)) were operated at different hydraulic retention times (HRTs), i.e., 36, 30, 24, 18, and 12?h corresponding to food-to-mass ratios varying in the range of 0.2?C0.7?mg chemical oxygen demand (COD) mg^?1 volatile suspended solids day^?1. The process kinetics of substrate utilization was evaluated on the basis of experimental results, by applying three mathematical models namely first order, Grau second order, and Michaelis-Menten type kinetics.

Results

The results showed that the lowering of HRT below 24?h resulted in reduced COD removal efficiencies and higher effluent pollutant concentrations in the reactors. The Grau second-order model was successfully applied to obtain the substrate utilization kinetics with high value of R ² (>0.95). The Grau second-order substrate removal constant (K ₂) was calculated as 1.12 and 7.53?day^?1 for reactors R2 and R3, respectively.

Conclusion

This study demonstrated the suitability of Grau second-order kinetic model over other models, for predicting the performance of reactors R2 and R3, in treating wastewaters containing chlorinated ethanes under different organic and hydraulic loading conditions.     

An investigation of anthraquinone dye biodegradation by immobilized Aspergillus flavus in fluidized bed bioreactor

Purpose

Biodegradation and biodecolorization of Drimarene blue K₂RL (anthraquinone) dye by a fungal isolate Aspergillus flavus SA2 was studied in lab-scale immobilized fluidized bed bioreactor (FBR) system.

Method

Fungus was immobilized on 0.2-mm sand particles. The reactor operation was carried out at room temperature and pH?5.0 in continuous flow mode with increasing concentrations (50, 100, 150, 200, 300, 500?mg?l^?1) of dye in simulated textile effluent on the 1st, 2nd, 5th, 8th, 11th, and 14th days. The reactors were run on fill, react, settle, and draw mode, with hydraulic retention time (HRT) of 24?C72?h. Total run time for reactor operation was 17?days.

Results

The average overall biological oxygen demand (BOD), chemical oxygen demand (COD), and color removal in the FBR system were up to 85.57%, 84.70%, and 71.3%, respectively, with 50-mg?l^?1 initial dye concentration and HRT of 24?h. Reductions in BOD and COD levels along with color removal proved that the mechanism of biodecolorization and biodegradation occurred simultaneously. HPLC and LC?CMS analysis identified phthalic acid, benzoic acid, 1, 4-dihydroxyanthraquinone, 2,3-dihydro-9,10-dihydroxy-1,4-anthracenedione, and catechol as degradation products of Drimarene blue K₂RL dye. Phytotoxicity analysis of bioreactor treatments provided evidence for the production of less toxic metabolites in comparison to the parent dye.

Conclusion

The present fluidized bed bioreactor setup with indigenously isolated fungal strain in its immobilized form is efficiently able to convert the parent toxic dye into less toxic by-products.     

Photocatalytic degradation of Orange G dye under solar light using nanocrystalline semiconductor metal oxide

Introduction

The photocatalytic degradation of Orange G (OG) dye has been investigated using synthesised nanocrystalline ZnO as a photocatalyst and sunlight as the irradiation source. The formation of ZnO prepared from its precursor was confirmed through FT-IR and powder X-ray diffraction analyses.

Materials and methods

Surface morphology was characterised by scanning electron microscope and transmission electron microscope analysis. Band gap energy of synthesised nanocrystalline ZnO was calculated using diffuse reflectance spectroscopy (DRS). Different experimental parameters such as effects of pH, dye concentrations and mass of catalyst were standardised in order to achieve complete degradation of the dye molecules under solar light irradiation.

Results

The kinetics of oxidation of OG was also studied. The complete degradation of OG was evident after 90 min of irradiation at an initial pH of 6.86. The degradation of OG was confirmed by UV?CVisible spectrophotometer, high-pressure liquid chromatography, ESI-Mass and chemical oxygen demand analyses.

Conclusion

The adsorption of dye onto catalytic surface was analysed employing model equations such as Langmuir and Freundlich isotherms, and it was found that the Langmuir isotherm model best fitted the adsorption data. The solar photodegradation of OG followed pseudo-first-order kinetics. HPLC and ESI-Mass analyses of the degraded samples suggested that the dye molecules were readily degraded under solar irradiation with nanocrystalline ZnO.     

In situ photoelectrochemical/photocatalytic study of a dye discoloration in a microreactor system using TiO2 thin films

Introduction

In this work, we report in situ studies of UV photoelectrocatalytic discoloration of a dye (indigo carmine) by a TiO₂ thin film in a microreactor to demonstrate the driving force of the applied electrode potential and the dye flow rate toward dye discoloration kinetics.

Methods

TiO₂ 65-nm-thick thin films were deposited by PVD magnetron sputtering technique on a conducting glass substrate of fluorinated tin oxide. A microreactor to measure the discoloration rate, the electrode potential, and the photocurrent in situ, was developed. The dye solutions, before and after measurements in the microreactor, were analyzed by Raman spectroscopy.

Results

The annealed TiO₂ thin films had anatase structure with preferential orientation (101). The discoloration rate of the dye increased with the applied potential to TiO₂ electrode. Further, acceleration of the photocatalytic reaction was achieved by utilizing dye flow recirculation to the microreactor. In both cases the photoelectrochemical/photocatalytic discoloration kinetics of the dye follows the Langmuir?CHinshelwood model, with first-order kinetics.

Conclusions

The feasibility of dye discoloration on TiO₂ thin film electrodes, prepared by magnetron sputtering using a flow microreactor system, has been clearly demonstrated. The discoloration rate is enhanced by applying a positive potential (E _AP) and/or increasing the flow rate. The fastest discoloration and shortest irradiation time (50?min) produced 80% discoloration with an external anodic potential of 0.931?V and a flow rate of 12.2?mL?min^?1.     

Copper chitosan nanocomposite: synthesis, characterization, and application in removal of organophosphorous pesticide from agricultural runoff

Purpose

Removal of malathion from agricultural runoff was studied using novel copper-coated chitosan nanocomposite (CuCH)??a biopolymeric waste obtained from marine industry.

Methods

Synthesis and characterization of the adsorbent using different spectral techniques like Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, energy-dispersive X-ray spectroscopy, Brunauer, Emmett, and Teller surface analyzer have been carried out. Equilibrium studies have been carried out to optimize the dose rate, pH, and the reaction time. Parathion and methyl parathion removal were also evaluated by CuCH in the batch mode. Using gas chromatography?Cmass spectrometry (GC?CMS) and FTIR studies suitable mechanism for adsorption has been suggested.

Results

The particle size of the adsorbent ranged from 700 to 750?nm. The surface area was found to be 20?m²?g^-1 with a pore volume of 0.11?cc?g^-1. The maximum adsorption capacity of malathion by CuCH was found to be 322.6?±?3.5?mg?g^-1 at an optimum pH of 2.0. Presence of copper ions enhanced the adsorption capacity of the adsorbent. The reaction was found to follow pseudo second-order kinetics with a rate constant of 0.53?g?mg^-1?min^-1. Evidence from FTIR indicated that copper ions form a dithionate complex with malathion during the adsorption stage. The adsorbent was found to remove malathion completely from spiked concentration of 2?mg?l^-1 in the agricultural run-off samples. It was also found that CuCH removed other organophospurous pesticides like methyl parathion and parathion under prevailing conditions.

Conclusions

The results indicated that CuCH could be applied for the removal of organophosphorous pesticides.     

Effect of particle size of titanium dioxide nanoparticle aggregates on the degradation of one azo dye

Introduction

Titanium dioxide (TiO₂) nanoparticle powders have been extensively studied to quickly photodegrade some organic pollutants; however, the effect of the particle size of TiO₂ nanoparticle aggregates on degradation remains unclear because microscale aggregates form once the nanoparticle powders enter into water.

Methods

The degradation of azo dye by different particle sizes of TiO₂ nanoparticle aggregates controlled by NaCl concentrations was investigated to evaluate the particle size effect. Removal reactions of reactive black 5 (RB5) with TiO₂ nanoparticles followed pseudo-first-order kinetics.

Results

The increase of TiO₂ dosage from 40 to 70?mg/L enhanced the degradation. At doses around 100?mg/L TiO₂, degradation rates decreased which could be the result of poor UV light transmittance at high-particle concentrations. At average particle sizes of TiO₂ nanopowders less than around 500?nm, the degradation rates increased with decreasing particle size. As the average particle size exceeded 500?nm, the degradation rates were not significantly changed.

Conclusions

For the complete degradation experiments, the mineralization rates of total organic carbon disappearance are generally following the RB5 decolorization kinetic trend. These findings can facilitate the application of TiO₂ nanoparticles to the design of photodegradation treatments for wastewater.     

Evaluation of adsorption characteristics of an anionic azo dye Brilliant Yellow onto hen feathers in aqueous solutions

Purpose and aim

Removal of an anionic azo dye Brilliant Yellow has been carried out from its aqueous solutions by using hen feathers as potential adsorbent.

Materials and methods

Hen feathers procured from local poultry were cut, washed, and activated. Detailed chemical and physical analysis of hen feathers and its characterization through scanning electron microscopy, X-ray diffraction, and infrared measurements have been made. Procured dye has been adsorbed over under batch measurements and adsorption process is monitored using UV spectrophotometer.

Results

Optimum parameters for the adsorption of Brilliant Yellow over hen feathers have been determined by studying the effect of pH, temperature, concentration of dye, and amount of adsorbent. On the basis of Langmuir adsorption, isotherms feasibility of the ongoing adsorption has been ascertained and thermodynamic parameters have been calculated. Attempts have also been made to verify Freundlich, Tempkin, and Dubinin?CRadushkevich adsorption isotherm models. It is found that during adsorption, uniform distribution of binding energy takes place due to interaction of the dye molecules and the ongoing adsorption process is chemisorptions. The kinetic measurements indicate dominance of pseudo-second-order process during the adsorption. The mathematical treatment on the kinetic data reveals the rate-determining step to be governed through particle diffusion at 8?×?10^?5?M and involvement of film diffusion mechanism at higher concentration at temperatures at all the temperatures.

Conclusions

The developed process is highly efficient and it can be firmly concluded that hen feather exhibits excellent adsorption capacity towards hazardous azo dye Brilliant Yellow.     

Bacterial assisted phytoremediation for enhanced degradation of highly sulfonated diazo reactive dye

Purpose

Phytoremediation is the exploitation of plants and their rhizospheric microorganisms for pollutants treatment like textile dyes, which are toxic, carcinogenic and mutagenic from the effluent. The purpose of this work was to explore a naturally found plant and bacterial synergism to achieve an enhanced degradation of Remazol Black B dye (RBB).

Methods

In vitro cultures of Zinnia angustifolia were obtained by seed culture method. Enzymatic analysis of the plant roots and Exiguobacterium aestuarii strain ZaK cells was performed before and after decolorization of RBB. Metabolites of RBB formed after its degradation were analyzed using UV?CVis spectroscopy, high-performance liquid chromatography (HPLC), Fourier transform infrared (FTIR) and gas chromatography?Cmass spectrometry (GC-MS). Phytotoxicity studies were performed.

Results

The consortium ZE was found to be more efficient than individual plant and bacteria. Z. angustifolia roots showed significant induction in the activities of lignin peroxidase, laccase, DCIP reductase and tyrosinase during dye decolorization. E. aestuarii showed significant induction in the activities of veratryl alcohol oxidase, azo reductase and DCIP reductase. Analysis of metabolites revealed differential metabolism of RBB by plant, bacteria and consortium ZE. E. aestuarii and Z. angustifolia led to the formation of 3,6-diamino-4-hydroxynaphthalene-2-sulfonic acid, (ethylsulfonyl)benzene, and 3,4,6-trihydroxynaphthalene-2-sulfonic acid and propane-1-sulfonic acid, respectively, whereas consortium ZE produced 4-hydroxynaphthalene-2-sulfonic acid, naphthalene-2-sulfonic acid and 4-(methylsulfonyl)phenol. The phytotoxicity study revealed the nontoxic nature of the metabolites formed after dye degradation.

Conclusion

Consortium ZE was found to be more efficient and faster in the degradation of RBB when compared to degradation by Z. angustifoila and E. aestuarii individually.     

Modeling and optimization of reductive degradation of chloramphenicol in aqueous solution by zero-valent bimetallic nanoparticles

Purpose

The present study aims to investigate the individual and combined effects of temperature, pH, zero-valent bimetallic nanoparticles (ZVBMNPs) dose, and chloramphenicol (CP) concentration on the reductive degradation of CP using ZVBMNPs in aqueous medium.

Method

Iron?Csilver ZVBMNPs were synthesized. Batch experimental data were generated using a four-factor statistical experimental design. CP reduction by ZVBMNPs was optimized using the response surface modeling (RSM) and artificial neural network-genetic algorithm (ANN-GA) approaches. The RSM and ANN methodologies were also compared for their predictive and generalization abilities using the same training and validation data set. Reductive by-products of CP were identified using liquid chromatography-mass spectrometry technique.

Results

The optimized process variables (RSM and ANN-GA approaches) yielded CP reduction capacity of 57.37 and 57.10?mg?g^?1, respectively, as compared to the experimental value of 54.0?mg?g^?1 with un-optimized variables. The ANN-GA and RSM methodologies yielded comparable results and helped to achieve a higher reduction (>6%) of CP by the ZVBMNPs as compared to the experimental value. The root mean squared error, relative standard error of prediction and correlation coefficient between the measured and model-predicted values of response variable were 1.34, 3.79, and 0.964 for RSM and 0.03, 0.07, and 0.999 for ANN models for the training and 1.39, 3.47, and 0.996 for RSM and 1.25, 3.11, and 0.990 for ANN models for the validation set.

Conclusion

Predictive and generalization abilities of both the RSM and ANN models were comparable. The synthesized ZVBMNPs may be used for an efficient reductive removal of CP from the water.     

Alteration of in vitro and acute in vivo toxicity of textile dyeing wastewater after chemical and biological remediation

Introduction

Textile industry is one of the most common and essential sectors in Tunisia. However, the treatment of textile effluents becomes a university because of their toxic impacts on waters, soils, flora, and fauna.

Materials and methods

The aim of this work was to evaluate the ability of Pseudomonas putida mt-2 to decolorize a textile wastewater and to compare the biologic decolorization process to the chemical one currently used by the textile industry.

Results

P. putida exhibited a high decolorizing capacity of the studied effluent, compared to the coagulation?Cflocculation method with decolorization percentage of 86% and 34.5%, respectively. Genotoxicity of the studied effluent, before and after decolorization by P. putida mt-2, was evaluated in vitro, using the SOS chromotest, and in vivo, in mouse bone marrow, by assessing the percentage of cells bearing different chromosome aberrations compared to not treated mice. In addition, textile effluent statistically significant influenced acetylcholinesterase and butyrylcholinesterase activities and lipid peroxidation (p?P. putida is a promising and improved alternative to treating industrial scale effluent compared to current chemical decolorization procedures used by the Tunisian textile industry.     

Adsorption of Remazol Red 198 onto magnetic N-lauryl chitosan particles: equilibrium, kinetics, reuse and factorial design

Purpose

The discharge of colored effluents from industries is an important environmental issue and it is indispensable to remove the dyes before the water gets back to the rivers. The magnetic adsorbents present the advantage of being easily separated from the aqueous system after adsorption by positioning an external magnetic field.

Methods

Magnetic N-lauryl chitosan (L-Cht/??-Fe₂O₃) particles were prepared and characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy, and vibrating sample magnetometry. Remazol Red 198 (RR198) was used as a reactive dye model for adsorption on L-Cht/??-Fe₂O₃. The adsorption isotherms were performed at 25°C, 35°C, 45°C, and 55°C and the process was optimized using a 2³ factorial design (analyzed factors: pH, ionic strength, and temperature). The desorption and regeneration studies were performed in a three times cycle.

Results

The characterization of the material indicated that the magnetic particles were introduced into the polymeric matrix. The pseudo-second order was the best model for explaining the kinetics and the Langmuir?CFreundlich was the best-fitted isotherm model. At room temperature, the maximum adsorption capacity was 267?mg?g^?1. The material can be reused, but with a decrease in the amount of adsorbed dye.

Conclusions

L-Cht/??-Fe₂O₃ is a promising material to remove RR198 and probably other similar reactive dyes from aqueous effluents.     

Optimization of nitrate reduction by EDTA catalyzed zero-valent bimetallic nanoparticles in aqueous medium

The present study aims to investigate the EDTA catalyzed reduction of nitrate (NO ₃ ^? ) by zero-valent bimetallic (Fe?CAg) nanoparticles (ZVBMNPs) in aqueous medium and to enumerate the effect of temperature, solution pH, ZVBMNPs dose and EDTA concentration on NO ₃ ^? reduction. Batch experimental data were generated using a four-factor Box?CBehnken design. Optimization modeling was performed using the response surface method for maximizing the reduction of NO ₃ ^? by ZVBMNPs. Significance of the independent variables and their interactions were tested by the analysis of variance and t test statistics. The model predicted maximum reduction capacity (340.15?mg?g^?1 NO ₃ ^? ) under the optimum conditions of temperature, 60?°C; pH?4; dose, 1.0?g?l^?1; and EDTA concentration, 2.0?mmol?l^?1 was very close to the experimental value (338.62?mg?g^?1) and about 16?% higher than the experimentally determined capacity (291.32?mg?g^?1). Study demonstrated that ZVBMNPs had higher reduction efficiency than Fe⁰ nanoparticles for NO ₃ ^? . EDTA significantly enhanced the NO ₃ ^? reduction by ZVBMNPs. The EDTA catalyzed reduction of NO ₃ ^? by ZVBMNPs can be employed for the effective decontamination of water.     

Equilibrium and kinetics of adsorption of phosphate onto iron-doped activated carbon

Purpose

Two series of activated carbons modified by Fe (II) and Fe (III) (denoted as AC/N-Fe^II and AC/N-Fe^III), respectively, were used as adsorbents for the removal of phosphate in aqueous solutions.

Method

The synthesized adsorbent materials were investigated by different experimental analysis means. The adsorption of phosphate on activated carbons has been studied in kinetic and equilibrium conditions taking into account the adsorbate concentration, temperature, and solution pH as major influential factors.

Results

Maximum removals of phosphate are obtained in the pH range of 3.78?C6.84 for both adsorbents. Langmuir isotherm adsorption equation well describes the experimental adsorption isotherms. Kinetic studies revealed that the adsorption process followed a pseudo-second order kinetic model. Results suggest that the main phase formed in AC/N-Fe^II and AC/N-Fe^III is goethite and akaganeite, respectively; the presence of iron oxides significantly affected the surface area and the pore structure of the activated carbon.

Conclusions

Studies revealed that iron-doped activated carbons were effective in removing phosphate. AC/N-Fe^II has a higher phosphate removal capacity than AC/N-Fe^III, which could be attributed to its better intra-particle diffusion and higher binding energy. The activation energy for adsorption was calculated to be 22.23 and 10.89 kJ mol^?1 for AC/N-Fe^II and AC/N-Fe^III, respectively. The adsorption process was complex; both surface adsorption and intra-particle diffusion were simultaneously occurring during the process and contribute to the adsorption mechanism.     

Removal of arsenate from groundwater by electrocoagulation method

Purpose

Arsenic, a toxic metalloid in drinking water, has become a major threat for human beings and other organisms. In the present work, attempts have been made to remove arsenate from the synthetic as well as natural water of Ballia district, India by electrocoagulation method. Efforts have also been made to optimize the various parameters such as initial arsenate concentration, pH, applied voltage, processing time, and working temperature.

Method

Electrocoagulation is a fast, inexpensive, selective, accurate, reproducible, and eco-friendly method for arsenate removal from groundwater. The present paper describes an electrocoagulation method for arsenate removal from groundwater using iron and zinc as anode and cathode, respectively.

Results

The maximum removal of arsenate was 98.8% at 2.0?mg?L^?1, 7.0, 3.0?V, 10.0?min, and 30°C as arsenate concentration, pH, applied voltage, processing time, and working temperature, respectively. Relative standard deviation, coefficient of determination (r ²), and confidence limits were varied from 1.50% to 1.59%, 0.9996% to 0.9998%, and 96.0% to 99.0%, respectively. The treated water was clear, colorless, and odorless without any secondary contamination. The developed and validated method was applied for arsenate removal of two samples of groundwater of Ballia district, U.P., India, having 0.563 to 0.805?mg?L^?1, arsenate concentrations.

Conclusions

The reported method is capable for the removal of arsenate completely (100% removal) from groundwater of Ballia district. There was no change in the groundwater quality after the removal of arsenate. The treated water was safe for drinking, bathing, and recreation purposes. Therefore, this method may be the choice of arsenate removal from natural groundwater.     

Detection and quantitative analysis of 21 veterinary drugs in river water using high-pressure liquid chromatography coupled to tandem mass spectrometry

Introduction

The use of veterinary drugs in food production focuses on the control and improvement of animal health. The disadvantage of this practice is that pharmaceuticals and their metabolites are released into the environment, finding their way to natural water systems and becoming a potential risk to non-target organism.

Methods

This paper reports the development and validation of a quantitative method, based on high-performance liquid chromatography coupled to tandem mass spectrometry, for the simultaneous analysis of 21 veterinary drugs, antimicrobials, corticosteroids, coccidiostats and antifungal agents, in surface water.

Results

The precision of the method was established by calculating the mean recoveries, which were in the range of 94?C101%. The developed method was employed to conduct the first monitoring study on the presence of veterinary drugs in the Galicia region, Northwest of Spain and was applied to 235 surface water samples. Eleven veterinary drugs were detected at concentrations from below the limit of quantification to 2,978.6?ng?L^?1. Limits of detection and quantification were in the range of 6.2 (betamethasone, cortisone, decoquinate, dexamethasone, maduramycin, monensin, narasin, salinomycin, sulfachloropyridazine, sulfamethoxypyridazine and trimethoprim) to 12.5?ng?L^?1 (for the rest of the selected drugs) and 12.5 (betamethasone, cortisone, decoquinate, dexamethasone, maduramycin, monensin, narasin, salinomycin, sulfachloropyridazine, sulfamethoxypyridazine and trimethoprim) to 25.0?ng?L^?1 (for the remaining pharmaceuticals), respectively.

Conclusion

Sulfonamides were the group most frequently found, which are widely used in veterinary medicine.     

Lead concentration increase in the hepatic and gill soluble fractions of European chub (Squalius cephalus)—an indicator of increased Pb exposure from the river water

Purpose

To examine if chronic exposure of feral fish to elevated Pb concentrations in the river water (up to 1???g?L^?1), which are still lower than European recommendations for dissolved Pb in surface waters (7.2???g?L^?1; EPCEU (Official J L 348:84, 2008)), would result in Pb accumulation in selected fish tissues.

Methods

Lead concentrations were determined by use of HR ICP-MS in the gill and hepatic soluble fractions of European chub (Squalius cephalus) caught in the Sutla River (Croatia?CSlovenia).

Results

At the site with increased dissolved Pb in the river water, soluble gill Pb levels (17.3???g?L^?1) were approximately 20 times higher compared to uncontaminated sites (0.85???g?L^?1), whereas the ratio between contaminated (18.1???g?L^?1) and uncontaminated sites (1.17???g?L^?1) was lower for liver (15.5). Physiological variability of basal Pb concentrations in soluble gill and hepatic fractions associated to fish size, condition, sex, or age was not observed, excluding the possibility that Pb increase in chub tissues at contaminated site could be the consequence of studied biotic parameters. However, in both tissues of Pb-exposed specimens, females accumulated somewhat more Pb than males, making female chubs potentially more susceptible to possible toxic effects.

Conclusions

The fact that Pb increase in gill and hepatic soluble fractions of the European chub was not caused by biotic factors and was spatially restricted to one site with increased dissolved Pb concentration in the river water points to the applicability of this parameter as early indicator of Pb exposure in monitoring of natural waters.