Chlorophenols In Wastewater Research Articles

Ionic Liquid-Based Magnetic Needle Headspace Single-Drop Microextraction Combined with HPLC/UV for the Determination of Chlorophenols in Wastewater.

A magnetic needle headspace single-drop microextraction (MN-HS-SDME) method coupled to HPLC/UV has been developed. Trihexyl(tetradecyl)phosphonium chloride was employed as an ionic liquid (IL) solvent for the headspace extraction of some chlorophenol (CP) compounds from wastewater samples. Despite of the nonmagnetic character of the IL, a significant improvement in the extraction efficiency was obtained by the magnetization of the single-drop microextraction needle using a pair of permanent disk magnets. A simplex method for the fast optimization of the experimental conditions (e.g., stirring speed, ionic strength, pH, extraction time and temperature) was used. The coefficients of determination (R2) varied between 0.9932 and 0.9989, the limits of detection were from 0.004 to 0.007μgmL-1 and the relative recoveries were in the range of 88-120% for the studied analytes. The developed MN-HS-SDME HPLC/UV method was successfully applied to the determination of CPs in industrial wastewater.

Efficient Fenton-like treatment of high-concentration chlorophenol wastewater catalysed by Cu-Doped SBA-15 mesoporous silica

Effective treatment for industrial wastewater that contains high concentration of chlorophenols is urgent and indispensable for environmental governance and human health due to their nonbiodegradable, carcinogenic and cytotoxic properties. Four kinds of Cu-containing mesoporous silica materials were utilized to catalyse Fenton-like treatment of high-concentration chlorophenols wastewater (1.0 g L−1). All of chlorophenols in various water matrices could be oxidatively decomposed in 35 min with the catalysis of Cu-doped SBA-15. Cu-doped SBA-15 with a Cu/Si molar ratio of 0.133 had the best catalytic activity in the oxidative degradation of 4-chlorophenol with an apparent reaction rate constant of 0.170 min−1 which was 1.3–3.6 times higher than those with other Cu-containing catalysts. After 300 min reaction, total organic carbon content of 4-chlorophenol solution declined continuously to 23.8% with an advisable utilization efficiency of H2O2 of 26.5%–68.4%. Electron spin resonance tests and quenching experiments demonstrated that Cu-doped SBA-15 had a selective catalytic activity in the decomposition of H2O2 into hydroxyl radicals which dominated the degradation of chlorophenols in wastewater. The redox of Cu(II)/Cu(I) in Cu-doped SBA-15 occurred efficiently, which could be attributed to chemical adsorption and electron transformation of organic molecular fragments onto Lewis acidic sites formed by the incorporation of Cu2+ ions in SBA-15. The biological toxicity of the treated 4-CP wastewater declined significantly in comparison with that of the original wastewater. Our work provided an effective way of the heterogeneous treatment of high-concentration chlorophenol wastewater.

Preconcentration and Determination of Chlorophenols in Wastewater with Dispersive Liquid–Liquid Microextraction Using Hydrophobic Deep Eutectic Solvents

Hydrophobic deep eutectic solvents (DESs) were synthesized and developed for the preconcentration of three chlorophenols from wastewater by dispersive liquid–liquid microextraction (DLLME). The analyte concentrations were determined by high-performance liquid chromatography (HPLC). The hydrophobic DESs were prepared with the combination of hydrogen bond donors of decanoic acid or octanoic acid with different hydrogen bond acceptors of quaternary ammonium salts of tetrabutylammonium chloride, tetraoctylammonium chloride, methyltrioctylammonium chloride, and tetraheptylammonium chloride). Following the study of the stability and characterization by Fourier transform infrared spectroscopy, the hydrophobic DESs were developed as extractants and employed for the removal of 4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP), and 2,4,6-trichlorophenol (2,4,6-TCP) from wastewater. Using hydrophobic DESs as the microextraction solvents, several key parameters were optimized, including the type and volume of the hydrophobic DES, pH, and time of the extraction procedure. Under the optimized conditions, good recoveries from 90.8% to 93.0% were obtained for the three chlorophenols. The limits of detection were less than 0.05 µg/mL with relative standard deviations between 1.8% and 3.1%. The method was applied for the isolation and determination of synthetic chlorophenols in wastewater.

Pd–Ag/Graphene Electrochemical Sensor for Chlorophenol Contaminant Determination

A graphene-supported Pd–Ag bimetallic alloy catalyst for rapid detection of low concentrations of chlorophenols (CPs) in environmental monitoring was prepared by wet chemical reduction. The catalyst was used to construct an electrochemical CP sensor. Catalyst-modified glassy carbon electrodes were evaluated for the determination of aqueous CP contaminants, i.e., 4-chlorophenol (4-CP), 3-chlorophenol (3-CP), 2-chlorophenol (2-CP), and 2,4-dichlorophenol (2,4-DCP), at low concentrations. Synergies between the Pd–Ag bimetallic alloy component and the graphene component of the electrochemical catalyst significantly affected the electrochemical reactions of the CPs, by enhancing the electron transfer rate and the electrochemical oxidation–reduction reaction efficiency. The optimal experimental conditions for a Pd0.5Ag0.5/reduced graphene oxide-modified electrode sensor were 0.1 mol/L phosphate-buffered saline, a scan rate of 100 mV/s, and pH 7. The detection ranges for the monochlorophenols (4-CP, 3-CP, and 2-CP) were wide, namely 0.1–80, 0.1–100, and 0.1–80 μmol/L, respectively. The dichlorophenol (2,4-DCP) detection range was broader, i.e., 0.002–100 μmol/L. The detection limits were low, namely 0.0075, 0.0077, 0.0047, and 0.00036 μmol/L (S/N = 3), respectively. These electrode sensors give good accuracy and reproducibility, and high recovery rates (almost 100%). They have anti-interference properties and long-term stability. The results indicate that such sensors could be used for detection of low concentrations of CPs in wastewater, and have good potential for use in practical applications.

Efficient biodegradation of chlorophenols in aqueous phase by magnetically immobilized aniline-degrading Rhodococcus rhodochrous strain.

BackgroundChlorophenols are environmental contaminants, which are highly toxic to living beings due to their carcinogenic, mutagenic and cytotoxic properties. Bacterial degradation has been considered a cost-effective and eco-friendly method of removing chlorophenols, compared to the traditional physical–chemical processes.ResultsIn this study, we first developed an efficient process for the biodegradation of chlorophenols by magnetically immobilized Rhodococcus rhodochrous cells. R. rhodochrous DSM6263 degrades chlorophenols following the first step of hydroxylation at the ortho-positions of chlorophenolic rings. The cells immobilized by k-carrageenan with 9 g/L Fe3O4 nanoparticles could efficiently degrade 2-chlorophenol, 4-chlorophenol, 2,3-dichlorophenol and their mixture, which were even higher than those by free cells. The magnetically nanoparticle-immobilized cells could be used at least for six cycles.ConclusionGiven the much easier separation by an external magnetic field and high degradation efficiency, this study provides a promising technique for improving biocatalysts used in the bioremediation process for chlorophenols in wastewater.

Determination of Chlorophenols in Wastewater with Methyl Chloroformate Derivatization, Solid Phase Extraction, and Gas Chromatography–Mass Spectrometry

The determination of chlorophenols in wastewater with methyl chloroformate derivatization, solid phase extraction, and gas chromatography–mass spectrometry is reported. In order to employ this combined solid phase derivative extraction method, quantitative extraction was performed by the introduction of 100 mL of sample in 1.0 mol L−1 sodium hydroxide into a column containing 500 mg of packed resin at a flow rate of 1.0 mL/min. The chlorophenols were retained and derivatized quantitatively in the column by the introduction of 0.25 mL of methyl chloroformate. The derivatized analytes were eluted with 5.0 mL of hexane before the effluent was dried under a stream of nitrogen. The dried solution was diluted to a volume of 50 µL with hexane followed by analysis by gas chromatography–mass spectrometry. The preconcentration parameters were optimized and under these conditions: limits of detection from 0.010 to 0.423 µg L−1, a preconcentration factor of 2500, and precision values from 4.8 to 7.7% as the relative standard deviation were obtained. The method was employed for the analysis of water samples and the recoveries of the analytes were between 76 and 103%.

Electrochemical Dechlorination of 2-Chlorophenol on Ti-Ni, Ti-Pd and Ti-Ni-Pd Electrodes

Chlorophenols are involved in the manufacture of different compounds as antiseptics, herbicides among others. Unfortunately, the presence of chlorophenols in wastewater of these industries has been detected. Chlorophenols have been listed as priority pollutants by The United State Envionmental Protection Agency (USEPA). Nowadays, the accumulation of chlorinated aromatic compounds in the environment represents an urgent problem to be solved [1].The chlorophenols are resistant physical, chemical or biological treatments and have hazardous impact on living organisms including human beings. Electrochemical dechlorination can be explored as pretreatment of chlorophenol degradation, because it is a promising method for its various advantages: low equipment cost, mild reaction conditions, and produces no pollutants [2]. In this work, nickel-titanium, palladium-titanium and nickel-palladium-titanium alloy cathodes were used for electrochemical dechloration of 2-chlorophenol. The cathodes were prepared by electrodeposition where the experimental conditions were determined from both a thermodynamic study using Predominance Existence and distribution species diagrams, and voltammetric study. The electrodes were characterized by SEM, XRD and XPS. The efficient dechloration of 2-chorophenol was achieved in the electrochemical conditions where the atomic hydrogen adsorption produced for water reduction takes place. The dechloration was performed in a filter press electrochemical reactor FM01-LC. The effluents from electrochemical treatment will be treated in a biological reactor containing denitrifying sludge. Acknowledgements: Miguel Arellano acknowledges the National Council of Science and Technology (CONACYT) by PhD grant. References Sun Z., Ge H., Hu X., Peng Y. Chem. Eng. Technol. 32, 134. (2009)Chen, G., Wang, Z. Y., Xia, D. G. Electrochem. Commun. 6, 268. (2004)

A sensitive electrochemical chlorophenols sensor based on nanocomposite of ZnSe quantum dots and cetyltrimethylammonium bromide

In this work, a very sensitive and simple electrochemical sensor for chlorophenols (CPs) based on a nanocomposite of cetyltrimethylammonium bromide (CTAB) and ZnSe quantum dots (ZnSe–CTAB) through electrostatic self-assembly technology was built for the first time. The composite of ZnSe–CTAB introduced a favorable access for the electron transfer and gave superior electrocatalytic activity for the oxidation of CPs than ZnSe QDs and CTAB alone. Differential pulse voltammetry (DPV) was used for the quantitative determination of the CPs including 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP) and pentachlorophenol (PCP). Under the optimum conditions, the peak currents of the CPs were proportional to their concentrations in the range from 0.02 to 10.0μM for 2-CP, 0.006 to 9.0μM for 2,4-DCP, and 0.06 to 8.0 for PCP. The detection limits were 0.008μM for 2-CP, 0.002μM for 2,4-DCP, and 0.01μM for PCP, respectively. The method was successfully applied for the determination of CPs in waste water with satisfactory recoveries. This ZnSe–CTAB electrode system provides operational access to design environment-friendly CPs sensors.

Single-drop coacervative microextraction of organic compounds prior to liquid chromatography: Theoretical and practical considerations

Coacervates made of surfactant aggregates, namely aqueous and reverse micelles and vesicles, were firstly used as solvents in single-drop microextraction (SDME) and proposed for the extraction and concentration of chlorophenols prior to liquid chromatography. The formation of coacervate drops in the needle tip of conventional microsyringes depended on the type of intermolecular forces established between the surfactant headgroups making up the supramolecular aggregates; hydrogen bond interactions were strong enough to permit the formation of spherical drops. Stability of 1–50 μL coacervate drops was achieved by introducing the microsyringe needle tip in a PTFE rod, the end of which had been machined out with a heated flanging-tool to get circular flanges (diameters in the range 3.5–6 mm). The parameters affecting the efficiency of single-drop coacervative microextraction (SDCME) were investigated using vesicular coacervates as a solvent and 2-chlorophenol (CP), 2,4-dichlorophenol (DCP), 2,4,6-trichlorophenol (TCP) and pentachlorophenol (PCP) as model analytes. Coacervative microextraction dynamics fit to the general rate equation of liquid–liquid extraction. The effect of variables such as extraction time, drop volume, stirring rate, pH and temperature, on the extraction of chlorophenols was similar to that described for organic solvent drops. Electrolyte concentrations above 0.1 M caused drop instability. Under the optimum conditions, detection limits were in the range 0.1–0.3 μg L −1. The relative standard deviation was between 4.3 and 5.6 at 20 μg L −1 spiked level. The method was applied to the determination of the four chlorophenols in wastewater, superficial water from a reservoir and groundwater and the recoveries were in the range 79 and 106% at 5–20 μg L −1 spiked level.

Colloid‐Enhanced Ultrafiltration of Chlorophenols in Wastewater: Part IV. Effect of Added Salt on the Surfactant Leakage in Surfactant Solutions and Surfactant–Polymer Mixtures

The critical aggregation concentration (cac) in surfactant–polymer mixtures approximates a lower limit to the surfactant concentration in the permeate (surfactant leakage) in polyelectrolyte micellar‐enhanced ultrafiltration. Here, the cac was measured at different salinities by using surface tension measurements. It was found that the cac increases slightly with the addition of simple salt, then the cac value decreases at higher salt concentration. The critical micelle concentration (CMC), which approximates surfactant leakage in micellar systems (no polymer), decreases monotonically with increasing salinity for ionic surfactants. The surfactant leakage in colloid‐enhanced ultrafiltration (CEUF) processes is investigated by using a dialysis method in the presence of three phenolic solutes with various degrees of chlorination: 2‐monochlorophenol (MCP), 2,4‐dichlorophenol (DCP), and 2,4,6‐trichlorophenol (TCP). Cetylpyridinium chloride (CPC) or n‐hexadecylpyridinium chloride is used as a cationic surfactant; and sodium poly(styrenesulfonate) (PSS) is used as an anionic polyelectrolyte. The effect of salinity and type of colloid is focused on here. In the absence of added salt, the cac can be over an order of magnitude less than the CMC, as can be surfactant leakage with added polymer. The added salt reduces the surfactant leakage in the micellar solution due to CMC reduction in the presence of electrolyte. In the surfactant–polymer mixture, the surfactant leakage is dramatically affected by salinity.

A review of catalytic approaches to waste minimization: case study—liquid‐phase catalytic treatment of chlorophenols

AbstractEffective waste management must address waste reduction, reuse, recovery/recycle and, as the least progressive option, waste treatment. Catalysis can serve as an integral green processing tool, ensuring lower operating pressures/temperatures with a reduction in energy requirements while providing alternative cleaner synthesis routes and facilitating waste conversion to reusable material. The case study chosen to illustrate the role that catalysis has to play in waste minimization deals with the conversion of toxic chlorophenols in wastewater. The presence of chloro‐organic emissions is of increasing concern with mounting evidence of adverse ecological and public health impacts. A critical overview of the existing treatment technologies is provided with an analysis of the available literature on catalytic dechlorination. The efficacy of Pd/Al2O3 to promote the hydrogen‐mediated dechlorination of mono‐ and dichlorophenols is demonstrated, taking account of both the physical and chemical contributions in this three‐phase (solid catalyst and liquid/gaseous reactants) system. Hydrodechlorination activity and selectivity trends are discussed in terms of chloro‐isomer structure, the influence of temperature is discussed, the role of base (NaOH) addition is examined and the feasibility of catalyst reuse is addressed. Copyright © 2005 Society of Chemical Industry

Colloid-Enhanced Ultrafiltration of Chlorophenols in Wastewater: Part II. Apparent Acid Dissociation Constants of Chlorophenols in Colloid Solutions at Different Ionic Strengths and Effect of pH on Solubilization of Phenolic Compounds

ABSTRACTThe effects of pH, ionic strength, and type of colloid on the efficiency of removal of an organic solute in colloid-enhanced ultrafiltration, as indicated by the tendency of the solute to solubilize into micelles and surfactant–polymer complexes, are investigated in this paper. The apparent acid dissociation constants (Kaapp) of 2-monochlorophenol (MCP), 2,4-dichlorophenol (DCP), and 2,4,6-trichlorophenol (TCP) are determined in surfactant solutions and surfactant–polymer mixtures at different salinities using a spectrophotometric titration technique. The distribution coefficients of charged species and neutral species of MCP and the solubilization of TCP into micelles and into surfactant–polymer aggregates are measured using dialysis methods. Cetylpyridinium chloride (CPC) is the cationic surfactant and sodium polystyrenesulfonate (PSS) is the anionic polymer used. The apparent values of pKa(pKa,app) of the solutes in micellar solution are less than the corresponding values in aqueous solution (pKa,aq), whereas the values of pKa,app for the solutes in the surfactant–polymer mixtures are slightly higher than those in the aqueous and micellar solutions. The pKa,app values increase as salt concentration increases in the micellar solution while remaining almost unchanged in the surfactant–polymer mixtures. In the micellar solutions, the distribution coefficient into the surfactant aggregate of the anionic species of MCP is greater than that of the neutral species, by factors of approximately 30 to 1.5 when salt concentration increases from zero to 0.10 M. However, in the surfactant–polymer mixtures, the distribution coefficient of the neutral species is higher than that of the charged species by factors of 5 to 8 when salt concentration increases from zero to 0.05 M. In the micellar solutions, the distribution coefficients of the neutral species are less dependent on salinity than those of the charged species. The solubilization and solute rejection are influenced by pH, primarily for solutes with low hydrophobicity.

Colloid-Enhanced Ultrafiltration of Chlorophenols in Wastewater: Part III. Effect of Added Salt on Solubilization in Surfactant Solutions and Surfactant–Polymer Mixtures

ABSTRACTThe solubilization of three phenolic solutes in micellar solutions and surfactant–polymer mixtures is studied: 2-monochlorophenol (MCP), 2,4-dichlorophenol (DCP), and 2,4,6-trichlorophenol (TCP). The equilibrium dialysis (ED) technique is used to determine the solubilization equilibrium constant as a function of added NaCl concentration. The added salt enhances the solubilization ability of surfactant micelles, but it only slightly affects the solubilization constant of surfactant–polymer aggregates. The solubilization constant for the surfactant–only systems is greater than that for the surfactant–polymer systems. In the micellar solution, the solute with a low water solubility shows a greater solubilization constant than the solute with a higher water solubility; the solubilization constants increase in the order MCP < DCP < TCP. However, in the surfactant–polymer mixtures, the solubilization constant of DCP can exceed that of TCP due to two opposing effects: ion-dipole interaction, and water solubility or hydrophobicity. Understanding and quantifying this solubilization phenomenon is crucial to optimization of the performance of colloid-enhanced ultrafiltration separation processes.

Qualitative and quantitative determination of halogenated derivatives in wastewater from coking plant

AbstractThis paper describes a modification of the EPA 625 method for determination of chlorobenzenes and chlorophenols in wastewater containing pyridine bases. The method modification consists in introduction of an additional liquid/liquid extraction step for isolation, from the samples under investigation, of pyridine and quinoline bases, and also fractions consisting of benzene, its homologues, and its halogenated derivatives. The modified method has been used to determine the concentrations of chlorobenzenes and chlorophenols present in coking wastewater.

The determination of chlorophenols in waste water by capillary zone electrophoresis with an organic modifier

Acapillary zone electrophoretic method has been optimized to improve selectivity and resolution in the analysis of chlorophenols in waste water. Use of a buffer system containing organic solvent dramatically improved the separation of chlorophenols. It was shown that selectivity was strongly affected by electrolyte pH and the presence of organic modifiers. The results show that the determination of all seventeen chlorinated derivatives of phenol in water can be achieved by use of a single organic modifier. For example, with acetone as organic modifier all 17 chlorophenols could be separated and determined within 20 min. The standard deviation of migration times and peak areas of the chlorophenols were in the ranges 0.48–0.67% and 3.9–5.1% respectively. Detection linear ranges covered two orders of magnitude of concentration with correlation coefficients of 0.998–1.000, except for 4-chlorophenol. Quantitative aspects of capillary zone electrophoresis are also discussed. It was concluded that capillary zone electrophoresis is a potential method for determination of chlorophenol pollutants in waste water.

Photocatalytic decomposition of 4-chlorophenol over oxide catalysts

4-Chlorophenol in the presence of catalysts was decomposed in aqueous solution by a 125 W medium pressure mercury lamp in a thermostated quartz batch photoreactor, and the organic bound chlorine was catalytically converted into the environmentally less harmful inorganic chloride. Differences in the concentration of 4-chlorophenol and of the intermediates, such as hydroquinone and quinone, are followed by HPLC. The best catalyst among a homolog series for the photo-decomposition of 4-chlorophenol was selected as finely dispersed platinum oxide on a TiO 2 semiconductor support, and kinetic parameters of the Langmuir–Hinshelwood type decomposition reaction were reported for the selected catalyst. A simple mechanism of substrate degradation in accord with the chosen kinetic model was postulated. The developed process may serve photooxidative removal of chlorophenols in wastewater without using costly oxidants.

Determination of chlorophenols in waste water using C18 reverse-phase enrichment prior to high resolution gaschromatography-mass spectrometry

The analytical use of absorption chromatography using Sep-pak C18 cartridges for the determination of trace amounts of lower chlorinated chlorophenols and chlorocresols in complex waste water samples is studied. A simple and efficient analysis at ppb (μg/l) level has been developed and is demonstrated on municipal waste water receiving chlorophenols and chlorocresols from a chemical plant producing phenoxy herbicides. For higher halogenated phenols quantitative recovery is demonstrated for a sample volume of 1000 ml making preconcentration by means of C18 absorption chromatography especially useful for trace analysis of these phenols.