Chlorinated Hydrocarbons In Water Research Articles

Biochar, microbes, and biochar-microbe synergistic treatment of chlorinated hydrocarbons in groundwater: a review.

Dehalogenating bacteria are still deficient when targeted to deal with chlorinated hydrocarbons (CHCs) contamination: e.g., slow metabolic rates, limited substrate range, formation of toxic intermediates. To enhance its dechlorination capacity, biochar and its composites with appropriate surface activity and biocompatibility are selected for coupled dechlorination. Because of its special surface physical and chemical properties, it promotes biofilm formation by dehalogenating bacteria on its surface and improves the living environment for dehalogenating bacteria. Next, biochar and its composites provide active sites for the removal of CHCs through adsorption, activation and catalysis. These sites can be specific metal centers, functional groups or structural defects. Under microbial mediation, these sites can undergo activation and catalytic cycles, thereby increasing dechlorination efficiency. However, there is a lack of systematic understanding of the mechanisms of dechlorination in biogenic and abiogenic systems based on biochar. Therefore, this article comprehensively summarizes the recent research progress of biochar and its composites as a "Taiwan balm" for the degradation of CHCs in terms of adsorption, catalysis, improvement of microbial community structure and promotion of degradation and metabolism of CHCs. The removal efficiency, influencing factors and reaction mechanism of the degraded CHCs were also discussed. The following conclusions were drawn, in the pure biochar system, the CHCs are fixed to its surface by adsorption through chemical bonds on its surface; the biochar composite material relies on persistent free radicals and electron shuttle mechanisms to react with CHCs, disrupting their molecular structure and reducing them; biochar-coupled microorganisms reduce CHCs primarily by forming an "electron shuttle bridge" between biological and non-biological organisms. Finally, the experimental directions to be carried out in the future are suggested to explore the optimal solution to improve the treatment efficiency of CHCs in water.

Analytical method development using functionalized polysulfone membranes for the determination of chlorinated hydrocarbons in water

In this study, functionalized polysulfone membrane has been utilized as a sorbent for the extraction of chlorinated hydrocarbons (CHCs) in water samples. Two different functionalized polysulfones (i) phosphonic acid functionalized polysulfone (PPSU-A) with different forms (cross-linked and non cross-linked) membranes and (ii) phosphonic ester functionalized polysulfone (PPSU-E) with different forms (cross-linked and non cross-linked) were evaluated for the extraction of CHCs in water. A 10ml of spiked water sample was extracted with 50mg piece of the functionalized membrane. After extraction, the membrane was desorbed by organic solvent and the extract was analyzed by gas chromatography–mass spectrometry. Eight CHCs, 1,3,5-trichlorobenzene (1,3,5-TCB), 1,2,3-trichlorobenzene (1,2,3-TCB), 1,1,2,3,4,4-hexachloro-1,3-butadiene (HCBD), 1,2,4-trichloro-3-methylbenzene (TCMB), 1,2,3,4-tetrachlorobenzene (1,2,3,4-TeCB), 1,2,4,5-tetrachlorobenzene (1,2,4,5-TeCB), pentachlorobenzene (PeCB) and hexachlorobenzene (HCB) were used as model compounds. Experimental parameters such as extraction time, desorption time, types of polymer membrane as well the nature of desorption solvent were optimized. Using optimum extraction conditions calibration curves were linear with coefficients of determination between 0.9954 and 0.9999 over wide range of concentrations (0.05–100μgl−1). The method detection limits (at a signal-to-noise ratio of 3) were in the range of 0.4–3.9ngl−1. The proposed method was evaluated for the determination of CHCs in drinking water samples.

Electrochemical Continuous Decomposition of Chloroform and Other Volatile Chlorinated Hydrocarbons in Water Using a Column Type Metal Impregnated Carbon Fiber Electrode

Trihalomethane and other chlorinated hydrocarbons are known to be toxic to human health. However, removal of these compounds from water is not easy. We attempted continuous electrochemical decomposition of chloroform that is the main compound of trihalomethanes and some toxic chlorinated hydrocarbons in water using a metal-impregnated carbon fiber electrode (CFE). At Ag- and Zn-impregnated CFE, concentration of chloroform in 0.5 M K2SO4 (the supporting electrolyte) solution was decreased from 0.25 m mol/L to below the limit of detection of our analysis system (1 ppm) at a flow rate of 1 mL/min. The main product of electrolysis was methane. This high efficiency, determined by the chemical yield, hardly changed at a flow rate of 20 mL/min at a Ag-impregnated CFE. At a flow rate of 1 mL/min, chloroform was degraded with a decomposition efficiency of almost 100% even in the solution without the supporting electrolyte, whereas at a higher flow rate, the efficiency for the decomposition of chloroform decreased with a decrease in the concentration of the supporting electrolyte. Tetrachloroethylene, 1,1,1-trichloroethane, and 1,1,2-trichloroethane were also decomposed at a Ag-impregnated CFE with an efficiency of almost 100%.

Solid-phase microextraction as a source of data for the design of stripping aeration towers

Solid-phase microextraction was used for the analysis of volatile chlorinated hydrocarbons in water. The data were used for the verification of the penetration theory.

Laser-Induced Breakdown Spectroscopy of Liquids: Aqueous Solutions of Nickel and Chlorinated Hydrocarbons

Spectrochemical analyses of aqueous solutions containing nickel or the chlorinated hydrocarbons (CHCs) C2Cl4, CCl4, CHCl3, and C2HCl3 were performed with the use of laser-induced breakdown spectroscopy. A Nd:YAG laser operating at 60 mJ/pulse was focused onto the surface of the liquid. Elemental line intensities were monitored in the laser-produced plume as a function of analyte concentration to determine detection limits. The limits of detection for nickel in water were 36.4 ± 5.4 mgAL and 18.0 ± 3.8 mg/L for laser irradiation at 1.06 μm and 355 nm, respectively. Ablation of pure CHCs at 355 nm produced extremely intense plasma emissions that primarily consisted of spectroscopic features attributed to CN, C3, H, N, and Cl. The spectra were structurally identical for all the CHCs except for differences in the intensities of various emission lines. With the use of emission from neutral atomic chlorine as an identifier for CHC contamination of water, no detectable traces of these elements were observed in saturated aqueous solutions. The detection limits for the CHCs were well above the saturation limits of CHC in water.

Infrared attenuated total reflection spectroscopic investigations of the diffusion behaviour of chlorinated hydrocarbons into polymer membranes

The response behaviour of a sensor for chlorinated hydrocarbons (CHC) in water was evaluated practically and theoretically. The sensor consisted of polymer-coated attenuated total reflection (ATR) elements coated with different polymers such as low-density polyethylene polyisobutylene and ethylene/propylene copolymer and was based on the diffusion behaviour of the CHC in different polymer layers. The purpose of the polymer coating was to enrich chlorinated hydrocarbons and to exclude water from the information depth of the penetrating infrared (IR) radiation. The coated ATR crystals were mounted in a flow-through cell and placed inside the sample chamber of the Fourier transform infrared spectrometer equipped with a mercury-cadmium-telluride detector. Measurements were performed by filling the cell with aqueous solutions of CHC and recording a series of spectra with constant time offset. The aim of this study was to investigate the diffusion behaviour and to determine the diffusion coefficient of three CHC (monochlorobenzene, tetrachloroethylene and chloroform) in polymer matrices in order to optimize the sensor response. For that reason an already existing theoretical model was modified. Using this new model numerical simulations of the diffusion processes occurring in the aqueous and polymer phase with respect to different partition coefficients, different diffusion coefficients and different thicknesses were performed. A classical Fickian response was found to be the dominant diffusion behaviour observed for the diffusion of chlorinated hydrocarbons into the polymers. This work showed the importance to understand the diffusion processes in different polymer materials for optimizing a fiber optic sensing system for CHCs in water.

Sonochemical treatment of hazardous chlorinated hydrocarbons in water and sediments

Reducing CO2 emissions to cope with global warming is one of the most challenging issues for the global energy system in the 21st century. To deal with the tremendous challenge, we should promote long range global efforts keeping in mind the wide scope of technological possibilities.

Performance studies of an IR fiber optic sensor for chlorinated hydrocarbons in water

Chlorinated hydrocarbons (CHCs) were monitored using a recently presented infrared fiber-optic physico-chemical sensor consisting of an MIR transparent, polymer coated, silver halide fiber coupled to a commercial FTIR spectrometer. The aim of this study was to test the performance of this new fiber optic sensing device with respect to temperature dependence, simultaneous detection of several CHCs, sensitivity and dynamic response behavior. In addition the diffusion process of the CHCs into the polymer was analyzed in order to better understand and evaluate the obtained results. During the investigation of the temperature dependence of the sensor response to real trend could be observed in the temperature range of 0 to 22°C. The dynamic response of the sensor is in the minute range when experiencing an increase in concentration of the analyte while with a decrease in concentration, the response is relatively slow. The sensor enabled the detection of 10 environmentally relevant CHCs at concentrations of 1 to 50ppm. The simulation of the experimental diffusion data revealed Fick's 1st law diffusion for CHCs into the polymer layers. Finally the sensing device was validated with head space-gas chromatography (HSGC) analyses and showed good agreement with these already established methods. This work shows the great potential of IR fiber optic sensors as early warning systems for a variety of CHCs in water (“threshold alarm sensor”)

Simultaneous in-situ trace-analysis of several chlorinated hydrocarbons in water with an IR fiber optical system

The principles of coating silver halide fibers with polymers was used to analyze different chlorinated hydrocarbons in water simultaneousely. The sensing system, based on Fiber Evanescent Wave Spectroscopy (FEWS), was composed of a mid infrared (MIR) transparent silver halide fiber coupled to a Fourier Transform Infrared (FTIR) spectrometer and enabled the detection of the most widespread organochlorides in the lower ppm-range due to their specific absorptions in the MIR-range.

Simple device for the determination of volatile chlorinated hydrocarbons in water by gas chromatography

Simple device for the determination of volatile chlorinated hydrocarbons in water by gas chromatography

Direct mass-spectrometric analysis of volatile chlorinated hydrocarbons in water.

Direct mass-spectrometric analysis of volatile chlorinated hydrocarbons in water.