活性炭催化剂臭氧催化氧化处理废水的研究进展

介绍了近年来国内外活性炭催化剂臭氧催化氧化的研究结果,对活性炭及金属负载型活性炭催化剂的反应机理进行了总结。讨论了非均相臭氧催化氧化过程中活性炭的主要作用,活性炭催化剂的表面物化性质、pH值、温度在臭氧催化氧化过程中的影响规律。并提出活性炭催化剂的降解机理以及催化剂性质与有机污染物的化学结构之间的关系还需要进一步的研究。     

Degradation of Refractory Organic Pollutants by Catalytic Ozonation—Activated Carbon and Mn-Loaded Activated Carbon as Catalysts

A novel catalyst for the ozonation process was prepared by loading manganese on the granular activated carbon (GAC). Nitrobenzene was used as a model refractory organic micropollutant in this study. The catalytic activity of GAC and the Mn-loaded GAC were studied respectively. The removal efficiency of nitrobenzene by Mn-loaded GAC catalyzed ozonation could reach 34.2–49.9%, with the oxidation efficiency being about 1.5–2.0 times higher than that achieved in GAC catalyzed ozonation and 2.0–3.0 times higher than that achieved by ozonation alone. The effect of pH and the t -butanol on the GAC/ozone process was discussed. The optimum condition for preparing the catalyst was studied.     

Systematic Approach to Quantify Adsorption and Biodegradation Capacities on Biological Activated Carbon Following Ozonation

The goal of this research was to develop a systematic approach to quantify adsorption and biodegradation capacities on biological activated carbon (BAC). The role of absorption and biodegradation on BAC was studied using a continuous column. Several media, i.e., granular activated carbon (GAC), seeded glass bead and seeded GAC, and a target compound (p-hydroxybenzoic acid) were selected. Before breakthrough, the effluent of the GAC column contained a small amount of p-hydroxybenzoic acid that contributed the greatest amount of organic carbon to the effluent of the glass bead column, which suggests that adsorption should be the prevailing mechanism for removal the p-hydroxybenzoic acid, and biodegradation should be responsible for reducing the ozonation intermediates. Also, the bioactivity approach (biomass respiration potential, BRP) of BAC can not only reveal the importance of biodegradation mechanisms for the intermediates of ozonation, but also quantify the extent of the adsorption or biodegradation reaction occurring on BAC.     

Pyruvic Acid Removal from Water by the Simultaneous Action of Ozone and Activated Carbon

Activated carbon (AC) has been used to catalyze the ozonation of pyruvic acid in water. Pyruvic acid conversions were found to be 9 and 37% after 90 min of single ozonation and single adsorption with 40 gL^?1 AC, respectively, while 82% was reached at the same conditions during the AC catalytic ozonation. Also, for similar conditions, mineralization reached values of 67% in the AC catalytic ozonation against hardly 5% in the non-catalytic experiment. The process likely develops through both adsorption of ozone and pyruvic acid on the AC surface and generation of hydroxyl radicals that eventually is the responsible oxidizing species. Rate constants for both non-catalytic ozonation and AC-Ozone catalytic surface reaction, at 20°C and pH 7.5, were found to be 0.025 min^?1 and 87.9 Lg^?1s^?1, respectively. For AC concentrations higher than 2.5 gL^?1 gas-liquid mass transfer of ozone constituted the limiting step. At lower concentrations, internal diffusion plus surface reaction controlled the process rate.     

Kinetics of Heterogeneous Catalytic Ozone Decomposition in Water on an Activated Carbon

Ozone decomposition in water in the presence of an activated carbon has been studied. Variables investigated were agitation speed, carbon particle size, temperature and pH. In all cases, the presence of activated carbon improved the ozone decomposition rate. Between pH 2 and 7 the ozone decomposition rate due to both the homogeneous and heterogeneous mechanisms hardly varied while a significant increase was noticed with increasing pH. A kinetic study based on a Langmuir-Hinselwood type mechanism for the heterogeneous surface reaction was undertaken. According to this mechanism the heterogeneous ozone decomposition kinetics can be simplified to follow a first order process. Fit of experimental results to the kinetic equations derived from the mechanism allowed for the determination of the apparent first order rate constants of the ozone surface heterogeneous reaction and adsorption equilibrium constants.     

Adsorption and Microbiological Mechanisms for Removal of Natural Organics in Granular Activated Carbon Columns

Performance data for GAC columns treating surface water are analyzed to determine the relative importance of physical adsorption and biological activity, with and without pre-ozonation. Kinetic and equilibrium adsorption parameters for the source water are used in the Homogeneous Surface Diffusion model to predict GAC performance over 83 weeks. The model underestimates removal of TOC for ozonated and unozonated streams by 46% and 28%, respectively, which is attributed to omission of biological removal in the model.     

Ozonation of p-Nitrophenol Adsorbed on Activated Carbon Fiber (ACF) and the Change of Textural and Chemical Characteristics of ACF

Ozonation of p-nitrophenol adsorbed on activated carbon fiber (ACF) was conducted in a semiwet atmosphere, and its effect on the textural and chemical characteristics of ACF was examined. The decomposition kinetics of p-nitrophenol followed a pseudo–first-order reaction, and an increase in O₃ input enhanced the removal of p-nitrophenol. Ozone slightly etched ACF and resulted in a decrease in the pore volume of ACF, but slightly different changes in pore diameter also occurred on virgin and spent ACF. An increase in the surface oxygen-containing groups (C=O, COOH, etc.) after ozonation might have influence on the adsorption capacity of ACF.     

Catalytic Ozonation of Oxalic Acid in the Presence of Fe2O3-Loaded Activated Carbon

ABSTRACT

The activity and optimum condition of metal-loaded activated carbon catalyst (Me/AC) for oxalic acid (OA) ozonation were evaluated. Results showed that Fe-loaded activated carbon (Fe/AC) showed better activity in five kinds of Me/AC catalysts prepared by a dipping method. Fe catalyst, crystallizing as γ-Fe₂O₃, dispersed well on AC surface. Fe₂O₃/AC, with 1.12% Fe weight ratio and 450°C calcination temperature and showed better activity for OA ozonation. 89.2% of OA was removed in the Fe₂O₃/AC/O₃ process, which was higher than those in AC/O₃ (79.6%) and O₃ (3.2%) processes. The calcination process helped to promote adsorption capability and catalytic activity of AC. In addition, Surface hydroxyl groups played a key role in Fe₂O₃/AC’s catalytic activity. Acidic condition was more favorable for OA removal in the Fe₂O₃/AC/O₃ process. A hydroxyl radical (?OH) oxidation mechanism was proven in Fe₂O₃/AC/O₃. The catalytic activity of Fe₂O₃/AC remained satisfactory after several cycles, indicating that Fe₂O₃/AC had a good reusability property.     

改性粉煤灰对有机废水的吸附试验研究

本文将粉煤灰改性后对印染废水进行了吸附研究,找到较好的工艺条件与吸附效果。结果表明：对于COD 20～150mg／l的印染废水溶液,粉煤灰用量以40g／l为宜,pH为4．0,脱色率在32％以上。用0．1mol／l硫酸改性粉煤灰吸附印染废水的pH为4．0,投加量为24g／l,脱色率在47％以上,吸附处理后染料废水COD为76mg／l,COD去除率为21％。     

Investigation into Ozonation of Coal Coking Processing Wastewater for Cyanide,Thiocyanate and Organic Removal

A laboratory investigation was carried out to establish whether ozonation could be used to oxidize cyanides, thiocyanates and color in wastewater from a coal coking plant to supplement biological and activated carbon treatment (GAC). Ozonation was found to be capable of oxidizing cyanide and cyanate to sufficiently low levels at relatively high stoichiometric ratios as a result of competitive ozone consumption by organic substances in the wastewater. While good color removal was also achieved with ozonation, organic removal could not match GAC in overall organic removal. Ozonation was not found to be economical for the remaining nine years of a build, own, operate and transfer (BOOT) contract period. Ozonation would be competitive over longer operational periods and more environmentally friendly than presently used technology.     

Removal of Color and Organic Matter in Industrial Phosphoric Acid by Ozone: Effect on Activated Carbon Treatment

Industrial phosphoric acid at 42-45% P₂O₅ and containing organic matter (OM) in the range of 220 mg/L to 300 mg/L is treated by combined ozonation and activated carbon. Ozonation alone removes the initial dark color of the acid and eliminates the organic content. Adsorption on activated carbon alone can reduce OM levels by 80% for more than 25 g/kg P₂O₅. We find that a preozonation noticeably enhances activated carbon efficiency and reduces its specific consumption. Isoconversion curves are plotted in specific ozone and activated carbon ratio space.     

Influence of Ozonation of Humic and Fulvic Acids on Diuron Adsorption on Activated Carbon

The effect of ozonation on the competitor effect of humic and fulvic acids against diuron in adsorption on activated carbon in drinking water process has been studied. Ozonation treatment allows the removal of herbicides from drinking waters by modification of humic and fulvic acids structures. These latest are responsible for their adsorption variation on activated carbon. An ozone dose similar to that used in industrial pre-ozonation (1.3?mg ozone/l) does not cause significant transformations of humic and fulvic acids which could decrease their competitor effect and increase significantly the adsorption capacity of the activated carbon for a well-adsorbed pesticide like diuron.     

Effect of Calcination Temperature over the Performance of Mn-Ce-O on the Catalytic Ozonation of Olive Mill Wastewater

The effect of calcination temperature on Mn-Ce-O 70/30 characteristics, activity and stability was investigated when this catalyst was applied on the catalytic ozonation of a phenolic mixture. Two crystalline phases (cubic CeO₂ and tetragonal Mn₃O₄) were observed by X-ray diffraction analysis, which also showed an increase of crystallinity with temperature. The material prepared at 300 ºC was the most efficient regarding TPh (100%), TOC (80%) and COD (62%) removal, as well as revealed to be the one leading to the lowest amount of Mn leached. The generalized kinetic model (GKM) was able to describe mineralization during this catalytic process with relative errors of ±10%.     

活性炭吸附法脱除废水中的苯酚及吸附剂再生的研究

对活性炭对废水中苯酚的吸附平衡以及活性炭的再生进行了试验性研究和理论性探讨。结果发现,温度对活性炭的吸附能力有显著的影响,低温地吸附有利,吸附平衡可用Ｌａｒｇｍｕｉｒ方程描述;ＰＨ值对活性炭对苯酚捐附也有较强的影响,酸性的水溶液对吸附有利,强碱性水溶液对再生有利。分别采用乙醇、丙酮、ＮａＯＨ溶液、ＮａＯＨ溶液＋乙醇的混合液对吸附剂活性炭进行再生,再生率均能达到８５％以上,基本满足工业要求。     

活性炭纤维吸附法脱除废水中对氯苯酚及吸附剂的再生

采用活性炭纤维 (ACF)处理对氯苯酚 (PCP)模拟废水 ,通过静态和动态吸附研究 ,测定了吸附等温平衡线、动态突破曲线 ,并研究了ACF对PCP的吸附速率。结果表明 ,ACF对PCP的吸附容量较大 ,吸附平衡关系服从Langmuir型吸附等温线 ;吸附速率快 ;吸附达饱和的ACF用NaOH溶液再生 ,解吸速率很快 ,再生后吸附容量基本不变     

Effect of Media on Biofilter Performance Following Ozonation of Secondary Treated Municipal Wastewater Effluent: Sand vs. GAC

Ozone has been shown to be effective in the transformation of several chemicals of emerging concern that escape the wastewater treatment process, but there is concern whether toxic transformation products are formed. Two parallel biofilter columns with granular activated carbon (GAC) and filter sand following a pilot-scale ozone unit to treat secondary treated municipal wastewater were studied. Results show reduced wastewater genotoxicity following ozonation and further reduction following biofiltration. The BAC biofilter outperformed the sand biofilter in terms of reduction in both organics and genotoxicity. Biofilter performance correlated with biological indicators (dissolved oxygen reduction and effluent E. coli counts) but not with ATP bioactivity measurements. Limited bacterial (E. coli) regrowth was observed in treated effluent from both biofilters.     

The Effect of Ozonation and Filtration on AOC (Assimilable Organic Carbon) Value of Water from Eutrophic Lake

The effects of applying ozone into the source water of Cheng-Ching Lake Water Works (CCLWW) on the analysis of AOC (assimilable organic carbon) were compared in the laboratory and pilot-scale tests. CCLWW takes its raw water from an eutrophic lake. A pilot plant, established in CCLWW in southern Taiwan, was performed to improve the quality of water obtained by the former treatment processes. The direct application of ozone to the source water of CCLWW is called the pre-O₃ process. The post-O₃ process involves the treatment of effluent with ozone through a sand filter, following other treatments, including pre-O₃, coagulation and sedimentation. In a laboratory test, a 0.45 μm membrane filter was used to replace the facility of filtration for a sand filter. AOC_Total comprises AOC_P17 and AOC_NOX, which were determined using the P. fluorescens strain P17 and the Spirillum species strain NOX, respectively. During over 2 years' sampling in eutrophic lake, it revealed that AOC_P17 contributed substantially to AOC_Total. However, the filtrate from the source water obtained by filtering through a 0.45 μm membrane filter had an AOC_Total much lower than that of the source water, especially for the considerable decrease of AOC_P17. Also, the AOC value in source water is increased with algae number but not with NPDOC (non-purgeable dissolved organic carbon). This result indicated that algae numbers existing in the eutrophic lake might affect the analysis of AOC. Following the pre-O₃ process at the pilot-scale plant, the AOC_P17 was markedly lower than that of the source water, and AOC_NOX was slightly higher than that of the source water. However, when post-O₃ was added to the effluent from a sand filter at the pilot-scale plant, AOC_NOX exceeded that before post-O₃, while AOCP17 differed slightly from that before post-O₃. Apparently, this difference may be due to the algae number existing in the water samples. These results were verified by applying ozone to the source water, and to filtrate obtained by filtering through a 0.45 μm membrane filter in a lab-scale test, respectively.