Chlorobenzene Removal Efficiency Research Articles

Deep Oxidation of Chlorinated VOCs by Efficient Catalytic Peroxide Activation over Nanoconfined Co@NCNT Catalysts.

The catalytic removal of chlorinated VOCs (CVOCs) in gas-solid reactions usually suffers from chlorine-containing byproduct formation and catalyst deactivation. AOP wet scrubber has recently attracted ever-increasing interest in VOC treatment due to its advantages of high efficiency and no gaseous byproduct emission. Herein, the low-valence Co nanoparticles (NPs) confined in a N-doped carbon nanotube (Co@NCNT) were studied to activate peroxymonosulfate (PMS) for efficient CVOC removal in a wet scrubber. Co@NCNT exhibited unprecedented catalytic activity, recyclability, and low Co ion leakage (0.19 mg L-1) for chlorobenzene degradation in a very wide pH range (3-11). The chlorobenzene removal efficiency was kept stable above 90% over Co@NCNT, much higher than that of nonconfined Co@NCNS (45%). The low-valence Co NPs achieved a continuous electron redox cycling (Co0/Co2+ → Co3+ → Co0/Co2+) and greatly promoted the O-O bond dissociation of PMS with the least energy (0.83 eV) inside the channel of Co@NCNT to form abundant HO• and SO4•-. Thus, the deep oxidation of chlorobenzene was achieved without any biphenyl byproducts from the coupling reaction. This study provided a new avenue for designing novel nanoconfined catalysts with outstanding activity, paving the way for the deep oxidation of CVOC waste gas via AOP wet scrubber.

Nonthermal plasma coupled with liquid-phase UV/Fe–C for chlorobenzene removal

Catalyst poisoning problems limit the application of gas-solid non-thermal plasma (NTP) catalyzed decomposition of chlorinated volatile organic compounds (Cl–VOCs). To mitigate the catalyst deactivation, catalyst iron-loaded activated carbon (Fe–C) was added to the UV-activated liquid phase downstream of the NTP reactor (NTP + UV/Fe–C(L)) for the degradation of chlorobenzene (CB) in this study. The CB removal efficiency and mineralization efficiency (MR) of NTP + UV/Fe–C(L) were up to 94% and 68%, respectively, which were increased by 39% and 30% compared with the single NTP system. Compared with the conventional gas-solid NTP + UV/Fe–C(S) system, the stability of the NTP + UV/Fe–C(L) system was significantly improved due to the dissolved organic intermediates and low residuals on the catalyst surface. Reactive oxygen species ·OH and ·O2− dominated the decomposition of CB in the liquid phase, and with the help of UV, much more ·OH and ·O2− were produced by Fe–C catalytic O3. In addition, Fe–C improved the removal of CB by increasing its absorption mass transfer coefficient from 0.0016 to 0.0157 s−1. The degradation pathway of CB in the NTP + UV/Fe–C(L) system was proposed based on the detected organic intermediates. Overall, this study provides a new tactic to solve the catalyst poisoning problem in the NTP catalytic oxidation of Cl–VOCs.

Synergistic degradation of chlorobenzene using intimate coupling of visible-light responsive TiO2/oxygenous groups decorated g-C3N4 composites and Ralstonia sp. XZW-1

The effective and economic treatment of chlorobenzenes has become one of the most intractable issues in the field of air pollution control. Herein, a visible-light photocatalysis coupled with biodegradation (VPCB) system was developed by integrating an innovative visible-light responsive TiO2/oxygenous groups decorated g-C3N4 (TiO2/OCN) with polyurethane carriers immobilized with Ralstonia sp. XZW-1 for chlorobenzene removal. Performance tests showed that light intensity, preparation of the MICs, catalyst dosage and composition of the TiO2/OCN cast significant influence on chlorobenzene removal efficiency, with the degradation efficiency, mineralization and dechlorination ratios of VPCB achieving 100%, 35.5%, and 99.4% under the optimal conditions, respectively, outcompeting the sum of visible-light photocatalytic system and biodegradation protocols. Cycling tests further demonstrated the excellent stability of VPCB. Mechanism analysis found that increased reactive sites, improved visible-light harvesting, accelerated charge transfer and separation, and the resulting abundant active species jointly contributed to the enhanced photocatalytic activity of TiO2/OCN. Photogenerated holes were most significant active species for chlorobenzene removal, followed by OH and O2− radicals. The carriers could effectively protect microorganisms from light illumination and strong oxidizing species, allowing the further microbial metabolism of chlorobenzene photocatalytic oxidation intermediates with good biodegradability, not only greatly promoting the microbial growth and activity, but further enhancing chlorobenzene photocatalytic degradation. Plausible synergistic mechanism for chlorobenzene degradation between photocatalysis and biodegradation was also revealed. Furthermore, the VPCB system constructed presented wide applicability towards various pollutants, and its performance was found closely related with the hydrophobicity of pollutants. This work provided insight into the design and application of the VPCB system for the efficient and economic treatment of refractory pollutants.

Structural Characteristics and Functional Genes of Biofilms in Microbial Electrolysis Cells for Chlorobenzene Abatement

Chlorobenzene (CB) is typically emitted during industry and waste incineration, posing hazards to the safety of humans and the ecosystem. Successful CB elimination has been achieved in microbial electrolysis cells (MECs), whereas little is known about elimination effectiveness in response to the structural and functional characteristics of biofilms. Herein, the bacterial viability and functional gene abundance of biofilms in MECs with carbon cloth (CC), reticulated vitreous carbon (RVC), and nickel foam (NF) as cathodes are emphasized. Experimental results reveal that bacterial viability on RVC is 62 and 92% higher than that of CC and NF, respectively, achieving 30 and 65% superior CB removal efficiency. Notably, the MEC with RVC outperforms that with the highly conductive NF due to low electron loss, causing a twice as much increase in coulombic efficiency. Metagenomic analysis indicates that the CB degrader (i.e., Pandoraea), electrochemically active bacteria (i.e., Chryseobacterium), and genes responsible for CB metabolism (i.e., todD and clcB) in RVC biofilms increase by over 30%, fourfold, and 10%, respectively, compared to CC and NF. Moreover, CB degradation is found to occur via two possible pathways: (1) thorough elimination by dechlorination, hydrolysis, and oxidation after conversion to 3-chlorocatechol, and (2) conversion into phenol and benzoate for complete degradation.

Degradation of chlorobenzene by corona discharge coupled with Ce doped MnOx catalyst

ABSTRACT Ce doped MnO2/γ-Al2O3 catalysts are prepared and analysed by BET, XRD and SEM in this paper. The degradation of chlorobenzene (CB) by a synergistic system of catalyst and DC corona discharge is further investigated to examine the effects of discharge voltage on CB removal efficiency, CO2 selectivity and by-product O3 generation. The results show that the voltage is proportional to the removal efficiency of CB and the selectivity of CO2. At a voltage of 40 kV, the CB removal efficiency and CO2 selectivity are 88% and 75%, respectively. O3 is more likely to decompose into active oxygen atoms with Ce doped MnO2/γ-Al2O3 type catalyst, and its O3 emission is about 50–250 ppm lower than that of NTP alone. In addition to studying the effect of CB treatment, the decomposition mechanism of CB is also discussed by examining the exhaust gas by GC-MS.

Redox mediator-regulated microbial electrolysis cell to boost coulombic efficiency and degradation activity during gaseous chlorobenzene abatement

Microbial electrolysis cell (MEC), a promising technology, is being developed for volatile organic compounds (VOCs) abatement. One of the critical issues to limit its industrial application is the poor electron transfer. In this work, anthraquinone-2,6-disulfonate (AQDS) and flavin mononucleotide (FMN) are dosed to MECs for the chlorobenzene (CB) removal, which are denoted as MEC-AQDS and MEC-FMN, respectively. The MEC performance is significantly promoted due to that RMs lower down the internal resistance. The CB removal efficiency in MEC-AQDS and MEC-FMN are increased by 40% and 20%, respectively, compared with neat MEC. Moreover, ECmax and Ks of MEC-AQDS are 26% and 75% higher than that of neat MEC, respectively. AQDS is a more suitable RM with 66% and 50% higher in dechlorination efficiency and coulombic efficiency, respectively, compared with FMN. The enhancement of dechlorination process in MEC-AQDS is ascribed to two reasons. The lower resistance accelerates the electron transfer rate during dechlorination; and the enhancing growth of dechlorinating bacterium leads to an abundant excretion of dechlorination enzymes. Additionally, electrochemical analysis and intermediate detection imply that RMs affect the electron transfer pathways but not the degradation mechanism, that is, CB converts into 2-chlorophenol and 3-chlorocatechol successively, then ring-opens and dechlorinates for mineralization.

Enhanced biodegradation of chlorobenzene via combined Fe3+ and Zn2+ based on rhamnolipid solubilisation

Biotrickling filters (BTFs) for hydrophobic chlorobenzene (CB) purification are limited by mass transfer and biodegradation. The CB mass transfer rate could be improved by 150 mg/L rhamnolipids. This study evaluated the combined use of Fe3+ and Zn2+ to enhance biodegradation in a BTF over 35 day. The effects of these trace elements were analysed under different inlet concentrations (250, 600, 900, and 1200 mg/L) and empty bed residence times (EBRTs; 60, 45, and 32 sec). Batch experiments showed that the promoting effects of Fe3+/Zn2+ on microbial growth and metabolism were highest for 3 mg/L Fe3+ and 2 mg/L Zn2+, followed by 2 mg/L Zn2+, and lowest at 3 mg/L Fe3+. Compared to BTF in the absence of Fe3+ and Zn2+, the average CB elimination capacity and removal efficiency in the presence of Fe3+ and Zn2+ increased from 61.54 to 65.79 g/(m3⋅hr) and from 80.93% to 89.37%, respectively, at an EBRT of 60 sec. The average removal efficiency at EBRTs of 60, 45, and 32 sec increased by 2.89%, 5.63%, and 11.61%, respectively. The chemical composition (proteins (PN), polysaccharides (PS)) and functional groups of the biofilm were analysed at 60, 81, and 95 day. Fe3+ and Zn2+ significantly enhanced PN and PS secretion, which may have promoted CB adsorption and biodegradation. High-throughput sequencing revealed the promoting effect of Fe3+ and Zn2+ on bacterial populations. The combination of Fe3+ and Zn2+ with rhamnolipids was an efficient method for improving CB biodegradation in BTFs.

Synergetic catalytic removal of chlorobenzene and NOx from waste incineration exhaust over MnNb0.4Ce0.2Ox catalysts: Performance and mechanism study

Nb doped MnCe0.2Ox complex oxides catalysts prepared via a homogeneous precipitation method were investigated for synergistic catalytic removal of NOx and chlorobenzene (CB) at low temperatures. The MnNb0.4Ce0.2Ox catalyst with a molar ratio of Nb/Mn = 0.4 exhibits excellent activity and the NOx and CB removal efficiency reaches 94.5% and 96% at 220 °C, respectively. Furthermore, the NOx and CB removal efficiency of MnNb0.4Ce0.2Ox still remains above 80% after injecting 300 ppm SO2 and 7 vol% H2O for 36 h. In addition, the presence of CB and NOx + NH3 can improve the NOx and CB removal efficiency of MnNb0.4Ce0.2Ox, respectively. The analysis results from N2-BET, Py-IR, H2-TPR and NH3-TPD reveal that the introduction of Nb increases the average pore size, pore volume and surface area, promoted the growth of Lewis acid amount obviously, and enhances redox ability of MnCe0.2Ox at 100–250 °C. Moreover, the molecular migration process of NOx, NH3, CB and SO2 in NH3-SCR and CB oxidation reaction over MnNb0.4Ce0.2Ox catalysts were systematically studied. In situ DRIFTS, FT-IR and XPS also confirm that the adsorption of sulfate species and SO2 on the surface of MnNb0.4Ce0.2Ox is inhibited effectively by the introduction of Nb in the presence of SO2 and H2O. Moreover, Nb additives also enhance the structural stability of MnNb0.4Ce0.2Ox, due to the interactions among Mn, Nb and Ce. The NH3-TPD, H2-TPR and in situ DRIFTS results also confirm that the MnNb0.4Ce0.2Ox still retains abundant acid sites and high redox ability in the presence of SO2 and H2O. In summary, MnNb0.4Ce0.2Ox catalysts represent a promising and effective candidate for controlling NOx and CB at low temperatures.

Non-thermal plasma catalysis for chlorobenzene removal over CoMn/TiO2 and CeMn/TiO2: Synergistic effect of chemical catalysis and dielectric constant

The decomposition of chlorobenzene (CB) in a non-thermal plasma (NTP) catalysis combined reactor was investigated. CoMn/TiO2 and CeMn/TiO2 were prepared using a deposition–precipitation method. CB decomposition, carbon balance, selectivity of CO2, and the byproducts of NOx and O3 were investigated. NTP catalysis provided significantly better CB removal efficiency and CO2 selectivity than did the plasma alone. CoMn/TiO2 exhibited better removal efficiency than CeMn/TiO2 in the NTP-catalysis reactor, but the performance of the catalysts during the thermal catalytic oxidation was reversed without the NTP. To reveal the activity difference with CB decomposition in the NTP-catalysis hybrid system, the dielectric constant and the physicochemical properties of CoMn/TiO2 and CeMn/TiO2 were analyzed. The plasma, which was affected by the dielectric constant, played a dominant role in this hybrid system. The reducibility of the catalysts promoted the CO2 selectivity and O3 decomposition. The CoMn/TiO2 was remarkably stable in the NTP-catalysis hybrid system during extended testing.

Application of Fe-Cu/Biochar System for Chlorobenzene Remediation of Groundwater in Inhomogeneous Aquifers

Chlorobenzene (CB), as a typical Volatile Organic Contaminants (VOC), is toxic, highly persistent and easily migrates in water, posing a significant risk to human health and subsurface ecosystems. Therefore, exploring effective approaches to remediate groundwater contaminated by CB is essential. As an enhanced micro-electrolysis system for CB-contaminated groundwater remediation, this study attempted to couple the iron-copper bimetal with biochar. Two series of columns using sands with different grain diameters were used, consisting of iron, copper and biochar fillings as the permeable reactive barriers (PRBs), to simulate the remediation of CB-contaminated groundwater in homogeneous and heterogeneous aquifers. Regardless of the presence of homogeneous or heterogeneous porous media, the CB concentrations in the effluent from the PRB columns were significantly lower than the natural sandy columns, suggesting that the iron and copper powders coupled with biochar particles could have a significant removal effect compared to the natural sand porous media in the first columns. CB was transported relatively quickly in the heterogeneous porous media, likely due to the fact that the contaminant residence time is proportional to the infiltration velocities in the different types of porous media. The average effluent CB concentrations from the heterogeneous porous media were lower than those from homogeneous porous media. The heterogeneity retarded the vertical infiltration of CB, leading to its extended lateral distribution. During the treatment process, benzene and phenol were observed as the products of CB degradation. The ultimate CB removal efficiency was 61.4% and 68.1%, demonstrating that the simulated PRB system with the mixture of iron, copper and biochar was effective at removing CB from homogeneous and heterogeneous aquifers.

Application of coupled zero-valent iron/biochar system for degradation of chlorobenzene-contaminated groundwater.

A novel iron-carbon micro-electrolysis system, bamboo-derived biochar coupled with zero-valent iron (ZVI), was investigated for chlorobenzene (CB)-contaminated groundwater removal. Influences of initial pH value, mass ratio of the ZVI/Biochar, initial CB concentration and ionic strength of the ZVI/Biochar micro-electrolysis were studied. The results indicated that the increase of initial pH led to the decrease of the CB removal efficiency. While the optimum mass ratio of ZVI to biochar was 2:1, the improved initial concentration and reaction time were 33.68 mg/L and 4 h, respectively. When pH of 2, mass ratio of 2:1 and reaction time of 4 h were applied, the CB removal efficiency was 99.92%. Enhanced degradation of CB was observed with increased Cl- concentration. When the Cl- concentration of 1,000 mg/L and reaction time of 1 h were applied, the CB removal efficiency arrived at 98.2%. Additionally, considering that biochar is cost-effective and readily produced, the coupled ZVI/Biochar micro-electrolysis could represent an effective approach for the treatment of groundwater containing chlorinated organic compounds in the future.

The operating performance of a biotrickling filter with Lysinibacillus fusiformis for the removal of high-loading gaseous chlorobenzene.

Removal of gaseous chlorobenzene (CB) by a biotrickling filter (BTF) filled with modified ceramics and multi-surface hollow balls during gas–liquid mass transfer at the steady state was by microbial degradation rather than dissolution in the spray liquid or emission into the atmosphere. The BTF was flexible and resistant to the acid environment of the spray liquid, with the caveat that the spray liquid should be replaced once every 6–7 days. The BTF, loaded with Lysinibacillus fusiformis, performed well for purification of high-loading CB gas. The maximum CB gas inlet loading rate, 103 g m−3 h−1, CB elimination capacity, 97 g m−3 h−1, and CB removal efficiency, 97.7 %, were reached at a spray liquid flow rate of 27.6 ml min−1, an initial CB concentration of up to 1,300 mg m−3, and an empty bed retention time of more than 45 s.Electronic supplementary materialThe online version of this article (doi:10.1007/s10529-014-1559-5) contains supplementary material, which is available to authorized users.

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.

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.

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.

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.