Chlorobenzene Removal Research Articles

Performance of Biotrickling Filter Inoculated with Activated Sludge for Chlorobenzene Removal

Activated carbon fibers and multi-surface hollow balls were used to establish biotrickling filter (BTF), and the acclimated sludge was inoculated on surface of packing to purify waste gas containing chlorobenzene. The BTF performance was examined under different conditions in steady state. Results showed that the maximum removal efficiency (RE) could be reached under the condition of chlorobenzene initial concentration of 878.53–1522.48 mg· m-3 and the empty bed retention time (EBRT) of 56 s, while the average removal efficiency was 91.34%. EBRT of 45 s was determined appropriately, and the maximum chlorobenzene removal rate of 102.79 g·m-3·h had been achieved under the condition of chlorobenzene initial concentration of 920.36–2019.85 mg· m-3 and EBRT of 28 s. In the experiment, the BTF system ran stably and had no problem of reactor clogging.

Microwave-induced Degradation of Chlorobenzene Using Fe0 and TiO2 Coated on Cordierites as Catalyst

In this research, MW is used to irradiate and induce Fe0/cordierite (Fe0 coated cordierite particles) and TiO2/cordierite (TiO2 coated cordierite particles) for improving the catalytic decomposition rate to remove chlorobenzene (CB) dissolved in aqueous solution. Laboratory results show that when 30 W of microwave energy is applied for 300 sec the irradiation of microwave than without microwave irradiation improves the CB removal efficiency by 3.2 times (57.4% vs. 18.2%) for Fe0/cordierite and 2.7 times (43.3% vs. 15.8%) for TiO2/cordierite. Hence, applying the microwave induced cordierite coated Fe0 or TiO2 particles is a new application that has been proved effective to remove chlorine-containing organic pollutants.

Effects of design parameters on performance and cost analysis of combined ultraviolet-biofilter systems treating gaseous chlorobenzene based on mathematical modeling

A conceptual mathematical model was used to evaluate the design parameters of a combined ultraviolet (UV)-biofilter system, and perform a cost analysis. Results showed that the UV light source strength and the gas residence times in the UV system (UVRT) and biofilter (EBRT) had positive effects on the overall chlorobenzene removal efficiency of the system. High ratio of UVRT to EBRT improved the removal efficiency, suggesting that the UV system has a greater effect on the overall performance of the system compared with the biofilter. Analysis of the capital and operating costs showed that the capital costs of the standalone biofilter system were much higher than those of the standalone UV system. However, the biofilter operating costs were lower than those of the UV system. The operating costs of the combined UV-biofilter system increased with increasing UVRT/EBRT ratio, whereas its capital costs decreased.

Integrating Fluidized Copper/Iron Bimetal Nanoparticles and Microwave Irradiation for Treating Chlorobenzene in Aqueous Solution

In this research, MW irradiation is combined with copper/iron bimetal (Cu/Fe) nano-scale particles suspended in aqueous chlorobenzene (CB) solution to reduce the CB activation energy for enhancing its decomposition. When the metal particles are fluidized in solution, their surface area to absorb the MW energy will increase so that the heat converted from the absorbed MW energy will be distributed evenly in the solution to enhance CB decomposition. Laboratory results show that when MW energy is applied at 250 W for 300 sec to irradiate 100 mg L-1 of CB solution containing 1 g of fluidized Cu/Fe bimetallic particles, the CB removal rate is improved by 1.3 times (95.0% vs. 76.2%), and the activation energy is lowered by 3.6%. The integrated fluidized copper/iron bimetal nanoparticle and Microwave Irradiation system is effective in treating toxic organic substances as demonstrated in this study.

Degradation of Chlorobenzene with Microwave-Aided Zerovalent Iron Particles

Abstract Microwave (MW) was applied to enhance chlorobenzene (CB) removal using commercial micron iron (μ-Fe) particles, nanoscale iron particles (nC-Fe0), and nanoscale iron particles freshly prepared in our laboratory (nP-Fe0) as the dielectric media. CB solution irradiated with 250 W MW for 150 s achieved better CB removal than without MW irradiation, because MW radiation increased the iron oxidization rate, surface activity, and hence, the CB removal rate. MW-induced iron particles were capable of removing 13.6 times (61.2% vs. 4.5% for μ-Fe), 2.8 times (76.5% vs. 27.5% for nP-Fe0), and 3.6 times (65.4% vs. 18.1% for nC-Fe0) more CB, and the CB activation energy decreased to 16.8 kJ/mol (μ-Fe), 3.3 kJ/mol (nP-Fe0), or 3.5 kJ/mol (nC-Fe0). MW-induced iron particles can potentially decompose toxic organic substances as demonstrated in this laboratory study.

Degradation of chlorobenzene by strain Ralstonia pickettii L2 isolated from a biotrickling filter treating a chlorobenzene-contaminated gas stream

A Ralstonia pickettii species able to degrade chlorobenzene (CB) as the sole source of carbon and energy was isolated from a biotrickling filter used for the removal of CB from waste gases. This organism, strain L2, could degrade CB as high as 220 mg/L completely. Following CB consumption, stoichiometric amounts of chloride were released, and CO₂ production rate up to 80.2% proved that the loss of CB was mainly via mineralization and incorporation into cell material. The Haldane modification of the Monod equation adequately described the relationship between the specific growth rate and substrate concentration. The maximum specific growth rate and yield coefficient were 0.26 h⁻¹ and 0.26 mg of biomass produced/mg of CB consumed, respectively. The pathways for CB degradation were proposed by the identification of metabolites and assay of ring cleavage enzymes in cell extracts. CB was degraded predominantly via 2-chlorophenol to 3-chlorocatechol and also partially via phenol to catechol with subsequent ortho ring cleavage, suggesting partially new pathways for CB-utilizing bacteria.

Chlorobenzene removal efficiencies and removal processes in a pilot-scale constructed wetland treating contaminated groundwater

Low-chlorinated benzenes (CBs) are widespread groundwater contaminants and often threaten to contaminate surface waters. Constructed wetlands (CWs) in river floodplains are a promising technology for protecting sensitive surface water bodies from the impact of CBs. The efficiency and seasonal variability of monochlorobenzene (MCB), 1,4-dichlorobenzene (1,4-DCB) and 1,2-dichlorobenzene (1,2-DCB) removal, the impact of planting, and gaseous MCB emissions from the filter surface were investigated over the course of 1 year in both a vegetated pilot-scale CW and an unplanted reference plot (UR). Annual mean concentration decreases of MCB and 1,4-DCB were observed; however, annual mean 1,2-DCB removal was seen only in the upper filter layer. Planting ( Phragmites australis) had a statistically significant beneficial effect on removal. The CB removal efficiency in the CW generally decreased with depth, and seasonal variations of removal were evident, with less concentration decrease during summer. Load removal efficiencies of 59–65% (262–358 mg m −2 d −1) for MCB, 59–69% (4.0–5.1 mg m −2 d −1) for 1,4-DCB and 29–42% (0.6–2.1 mg m −2 d −1) for 1,2-DCB were observed in June and July. Volatilization of MCB from the filter surface accounted for 2–4% of the total amount removed. Simple cover layers of organic materials on the filter surface were suitable for MCB emission reduction. Model calculations were carried out to estimate the MCB removal potential attributable to microbial degradation, volatilisation, and plant uptake in the CW and UR. Microbial degradation was the dominating process. The observed positive impact of plants on MCB removal was caused by improved oxygen supply (due to root oxygen release into the rhizosphere and enhanced water table fluctuations), and direct plant uptake.

Modeling of a Combined Ultraviolet-Biofilter System to Treat Gaseous Chlorobenzene I: Model Development and Parametric Sensitivity

ABSTRACT A new type of a combined ultraviolet (UV)-biofilter system for air pollution control is developed. In this paper, two conceptual mathematical submodels of the UV reactor and standalone biofilter are developed. All model parameters have been determined by independent experiments or have been taken from literature. Results from UV and the standalone biofilter submodels are in a good agreement with experimental data. However, the performance of the combined system has significantly deviated from those of the UV or standalone submodels because of the stimulating effects of UV irradiation products on the subsequent biofilter performance. A modified model that considers the stimulating effects has agreed well with experimental data over a wide range of operating conditions. Further analysis of the primary parametric sensitivity of the model has shown that inlet chlorobenzene concentrations, gas empty-bed residence time in the UV reactor, and light intensity are important operating conditions. IMPLICATIONS This study focuses on the model development of a combined UV-biofilter system to treat gaseous chlorobenzene. The results of this study are useful in understanding the effects of UV pretreatment on the performance of the subsequent biofilter. It can also help predict chlorobenzene removal performance in combined UV-biofilter systems.

Reduced Degradation of Chlorobenzene in Cosolvent Solution Using Nanoscale Zerovalent Iron with Microwave Irradiation

Abstract Chlorobenzene (CB) in aqueous solution is effectively degraded using nanoscale zerovalent iron (ZVI) particles suspended in the solution as the dielectric media with microwave irradiation. When nonaqueous CB is flushed out of groundwater from the contaminated soil, a cosolvent (e.g., methanol or ethanol) is usually added to aid the process. However, the cosolvent in the aqueous solution may interfere with the decomposition of dechlorination using ZVI. Results of this study confirm that if the CB aqueous solution is treated with nanoscale ZVI particles irradiated with microwave, the cosolvent will lower the contact between ZVI particles and water molecules, thus reducing the CB degradation rate. When 250-W microwave (MW) energy was applied to the CB aqueous solution containing methanol (a cosolvent) for 150 s, increasing methanol fraction in the CB solutions impaired the CB degradation rate. CB removal efficiencies are 65.4% for 0% MeOH, 53.7% for 40% MeOH, 32.2% for 60% MeOH, and 2.7% for 100% Me...

Study on Mechanisms and Effect of Surfactant‐Enhanced Air Sparging

In an attempt to enhance the effectiveness of air sparging, two sets of experiments were designed to investigate the mechanisms and effect of surfactant-enhanced air sparging (SEAS). The first set was performed at different surface tensions and with different kinds of surfactants (sodium dodecyl benzene sulfonate and Tween-80 [Uniqema Americas LLC, Wilmington, Delaware]), which were added into the contaminated aquifer of different media (particle distribution size = 0.25 to 0.5 mm and 5 to 10 mm). The results indicated that the air saturation in the aquifer increased rapidly at an early stage, then the increase of air saturation slowed down with the increase of airflow rate. The air saturation of medium sand increased with the decrease in water surface tension, and maximum air saturation was achieved at a surface tension of approximately 5 x 10(-2) N/m (50 dyn/cm), which was considered to be the optimum surface tension for air sparging enhancement in the medium sand aquifer. The increase of air saturation in gravel was the result of the increase of foamability and foam stability. The second group of experiments is about the removal of chlorobenzene from the medium sand aquifer. The experiments indicated that chlorobenzene removal by SEAS was more complete and efficient than that of conventional air sparging technology. However, the increase of removal rate and the decrease of lingering concentration by SEAS was not significant, with a further decrease in the surface tension when the surface tension dropped to 5.04 X 10(-2) N/m (50.4 dyn/cm).

Application of microwave energy to treat granular activated carbon contaminated with chlorobenzene

AbstractGranular activated carbon (GAC) is an excellent dielectric material to absorb and convert microwave (MW) energy into thermal energy. The MW heat is effective in decomposing organic substances adsorbed on the carbon. One gram of GAC loaded with chlorobenzene (CB) was subject to the MW output power varying from 400 to 800 W for 60 s, the carbon temperature rises to 325 to 470°C; 81.9% to 100% of the adsorbed CB is decomposed with the GAC dielectric loss factor between 16.2 and 24.8 F/m. Additionally, for the same dielectric material, larger surface area will absorb more MW energy. With more GAC (e.g., 2 g), the heat generated within GAC will cause sparks to occur if the MW irradiation time exceeds 80 s. The occurrence of sparks causes the GAC surface to graphitize thus destroying the surface micropore structure that leads to more smooth surface with less adsorption capacity. After five repetitive uses, dielectric loss of the recovered GAC decreases from 29.8 to 19.4 and the CB removal rate declines from 100 to 91%. © 2009 American Institute of Chemical Engineers Environ Prog, 2010

Enhanced Degradation of Chlorobenzene in Aqueous Solution Using Microwave‐Induced Zero‐Valent Iron and Copper Particles

Microwaves were applied to reduce the activation energy of chlorobenzene in aqueous solution and enhance its removal using nanoscale zero-valent iron (Fe0) or zero-valent copper (Cu0) particles as dielectric media. When Fe0 and Cu0 particles absorb microwave energy, the electrical potential difference causes the metal electrons to rotate faster, thus producing more heat. The microwave-irradiated metal particles reduced the chlorobenzene activation energy by 6.1 kJ/mol (13.3 kJ/mol versus 19.4 kJ/mol) for Fe0 and 5.4 kJ/mol (15.8 kJ/mol versus 21.4 kJ/mol) for Cu0 and enhanced the chlorobenzene removal 4.1 times (82.8% versus 20.4%) for Fe0 and 3.7 times (72.1% versus 19.5%) for Cu0. The Fe0 has a higher standard reduction potential than Cu0; it is capable of removing more chlorobenzene than Cu0 (82.8% versus 72.1%). Using the microwave-induced nano-scale iron or copper particle is effective in treating toxic organic substances, as demonstrated in this study.

Enhanced dechlorination of chlorobenzene by microwave-induced zero-valent iron: particle effects and activation energy

Organic compounds such as chlorobenzene cannot be effectively decomposed with currently available biological and chemical treatment methods. Preliminary studies show that nano-scale zero-valent iron particles irradiated by microwave is effective in decomposing chemically refractive organic compounds such as chlorobenzene. In this study, microwave is applied to enhance chlorobenzene removal using micron-scale iron particles and nano-scale zero-valent iron particles suspended in the chlorobenzene solution as the dielectric media. The results show that better chlorobenzene removal can be achieved when the chlorobenzene solution is irradiated with 250 W microwave for 150 s than without microwave irradiation. The microwave radiation increases iron reaction rate and surface activity, thus enhancing the chlorobenzene removal. The microwave-induced iron particles cause the chlorobenzene activation energy to drop 34.0% for micron-scale iron and 16.1% for nano-scale zero-valent iron. They can remove 13.6 times more chlorobenzene for micro iron, and 3.6 times more chlorobenzene for nano iron. We have demonstrated that the microwave-induced nano-scale iron particles are effective in treating toxic organic substances as demonstrated in this laboratory study.

Combining zero-valent iron nanoparticles with microwave energy to treat chlorobenzene

In this research, MW energy is combined with nanoscale zero-valent iron (ZVI or Fe 0) particles suspended in aqueous chlorobenzene (CB) solution for enhancing the CB decomposition. When MW energy is applied at 250 W for 300 s to irradiate 100 mg/L of CB solution containing 1 g ZVI particles, the CB activation energy is decreased by 8.6 kJ/mol (21.9–13.3 kJ/mol) so that the CB removal efficiency is enhanced 4.6 times (82.8% vs. 18.1%). The reductive dechlorination reaction occurs at the surface of zero-valent iron particles; the organic substance in the bulk of the solution diffuses to the iron particle surface to contact the iron particle for the reductive dechlorination reaction to occur. When MW radiation penetrates the solution to reach the surface of suspended Fe 0 particles, the radiation accelerates the iron oxidization, and increases the surface activity site thus enhancing the CB decomposition rate. Hence the MW-induced zero-valent iron can reduce the CB activation energy that contributes to the enhanced rate of CB removal.

Preparation of MnO x/TiO 2 composites and their properties for catalytic oxidation of chlorobenzene

MnO x /TiO 2 composites with different atomic ratio of Mn/Ti were prepared by sol–gel, solvothermal and coprecipitation method, respectively. The catalytic tests on chlorobenzene (CB) removal ability of all 15 catalysts were performed in a fixed-bed flow reactor and compared to each other. Experimental results showed that when the atomic ratio of Mn/Ti reached 1:4, the activity of the catalysts prepared by three methods reached their highest value, particularly the catalyst with the Mn/Ti atomic ratio of 1:4 prepared by sol–gel method showed higher catalytic activity than the catalysts with the same atomic ratio prepared by other methods at temperature between 100 and 300 °C. From the microstructure characterization by XRD, SEM, EDS, BET, and TPR, it could be known that the combined TiO 2 phases of anatase and rutile and a good dispersion of manganese oxides contributed to a good catalytic performance in the catalyst prepared by the sol–gel method.

Study on influencing factors on removal of chlorobenzene from unsaturated zone by soil vapor extraction

This paper deals with the influencing factors on removal of chlorobenzene from unsaturated soils by soil vapor extraction (SVE) method. A series of one-dimensional column experiments were conducted to study the influencing factors for SVE method, the factors included extracted vapor flow rate, soil grain size, extraction mode, soil organic matter content and water content. The results indicated that: (1) the increase of vapor flow rate led to higher contaminant removal efficiency, but the increment of removal was not significant at higher flow rate levels; (2) soil grain sizes had a great impact on chlorobenzene removal efficiency, the coarser the sand, the higher the removal rate; (3) pulsed vapor extraction and continuous vapor extraction almost had the same contaminant removal effects in the sand column; (4) the higher organic content in the soil could decrease the removal efficiency; (5) water content in the soil had different impact on the contaminant removal efficiency which related with the organic content in the soil.

Stimulative Effects of Ozone on a Biofilter Treating Gaseous Chlorobenzene

Recalcitrant volatile organic compounds with low biodegradabilities pose challenges for biofiltration technologies. In this study, the effects and mechanism of adding ozone on the performance of a biofilter were investigated. A biofilter treating chlorobenzene was set up and operated continuously for 265 days under different inlet ozone concentrations. Results showed that ozone below 120 mg m(-3) could notably enhance the biofilter performance. The average chlorobenzene removal efficiency increased from 40 to 70% and then to 90% while the inlet ozone concentration rose from 0 to 40 mg m(-3) and 120 mg m(-3). Reducing ozone concentration resulted in a decrease in removal efficiency from 90 to 40%. Further analysis indicated that the thickness and extra-cellular polymer substance content of the biofilm were remarkably reduced while inlet ozone concentration was gradually increased. Meanwhile, the specific surface areas of the filter bed were found to increase from 784 to 820 and 880 m(2) m(-3). A respiratory quinone profile showed that the dominant quinone shifted from ubiquinone-8 to menaquinone-9(H(2)) after ozone was added. This indicated that some Gram-positive bacteria with thick cell wall became the dominant species under ozone compression.

Degradation of Chlorobenzene in Water Using Nanoscale Cu Coupled with Microwave Irradiation

In this research, the microwave (MW) energy is used to generate heat directly inside the nanoscale copper particles that are suspended in aqueous chlorobenzene (CB) solution. The heat will reduce CB activation energy so that the CB can be more efficiently decomposed by the heat generated. Because the copper particle surface has pointed protuberances, more MW energy can be absorbed to result in higher solution temperature and lower CB activation energy. Laboratory results indicate that without MW irradiation, the CB solution temperature varies from 25 to 60°C with 19.5 to 41.3% removal of CB that has 21.4 kJ/mol activation energy. In the presence of 250-W MW, the CB activation energy is reduced to 15.8 kJ/mol, and the CB removal efficiency is raised by 1.8 times. Using MW energy to generate heat directly in nanoscale copper particles suspended in aqueous CB solution for reducing the activation energy of CB and enhancing its removal is a novel and efficient method for treating toxic organic substances.

Effects of Operation Conditions on Removal Rate Constant and Quantum Yield of Gaseous Chlorobenzene Degradation in a Photochemical Reactor

A photochemical reactor with a low-pressure mercury ultraviolet (UV) lamp was established to treat waste gas containing chlorobenzene. Operation conditions such as light intensity, gas humidity, and inlet chlorobenzene concentration were varied. Two significant parameters, the removal rate constant and the quantum yield (relating to removal kinetic and light energy utilization), were investigated under each set of conditions. The experimental results indicated that the removal of chlorobenzene by UV irradiation in the gas phase followed a first-order kinetic model at inlet chlorobenzene concentrations ranging from 200 to 2500 mg • m-3. With increasing light intensity from 10 to 37 µW • cm-2, the chlorobenzene removal rate constant rose from 0.004 to 0.011 sec-1, whereas the quantum yield maintained the same value of 0.60. The effects of gas humidity on the parameters indicated that the highest humidity of 80% could achieve the highest removal rate constant (0.046, 0.029, and 0.015 sec-1) and the highest quantum yield (1.91, 1.19, and 0.60) among the tested gas humidities at the inlet concentrations of 400, 1000, and 2500 mg • m-3, respectively. An increase in inlet chlorobenzene concentration from 200 to 2500 mg • m-3 resulted in reduction in both removal rate constant (from 0.060 to 0.014 sec-1) and quantum yield (from 2.50 to 0.56) that may be attributable to competition between the intermediates and chlorobenzene. On the basis of the quantum yield, the total power expended per mass of chlorobenzene was calculated as 483 kWh • kg-1 under the conditions of an inlet concentration of 200 mg • m-3 and an empty-bed residence time of 27 sec.

Effects of nitrogen source, empty bed residence time and inlet concentration on biofilter removal of chlorobenzene

AbstractA new biofilter with bamboo carriers was used to remove gaseous chlorobenzene. Operating parameters such as the nitrogen source, the empty bed residence time (EBRT) and the inlet concentration of chlorobenzene were varied. The ability of the biofilter to remove chlorobenzene was evaluated under each set of conditions. The experimental results indicated that better biofilter performance was achieved using ammonium instead of nitrate nitrogen as the nitrogen source. However, an addition of excess ammonium did not further increase the removal efficiency. The optimal ratio of carbon to nitrogen supply (C/N) was 7:1−14:1. Increasing EBRT increased the biofilter efficiency from 0‐20% (EBRT=24 s) to 30‐50% (EBRT=41 s) and to 50‐70% (EBRT=122 s). The relationship between removal efficiency and EBRT indicated that the removal of chlorobenzene is a pseudo first order kinetic process below the concentration of 400 mg/m3. A substrate inhibition model, the Haldane equation, successfully described the removal rate of the biofilter at various inlet concentrations. With increasing inlet concentration, the removal rate initially rose and then declined. The highest removal rate of 18 g/m3 ×h was achieved at an inlet concentration of 1440 mg/m3.