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.     

Ozonation of Cyanide Catalyzed by Activated Carbon

In this work, the removal of cyanide from aqueous solutions was accomplished by using the synergetic effect of activated carbon and an oxidizing agent. A basic-character coconut shell activated carbon (CAC) was used; experiments were conducted in a semi-batch reactor, at 25 °C, initial pH of 11.5, and using cyanide solutions with initial concentration up to 1200 mg/mL. In particular, the beneficial effect of an oxidizing agent such as air, oxygen or ozone on the removal of cyanide by CAC was evaluated. At the optimum operating conditions found in this study, 1200 mg/mL of cyanide were totally decomposed in about 3 h, by using 1 g of CAC and about 2 mgO₃/min. The experimental results were rationalized based on different mechanisms reported in the literature. The findings provide the basis to optimize the removal of cyanide from aqueous solutions in mining or metallurgical effluents by using the synergetic effect of CAC and ozone.     

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.     

活性炭纤维在吸附领域的应用

活性炭纤维是一种新型高效吸附材料。本文阐述了活性炭纤维的结构与吸附性能间的关系，并介绍了它在吸附领域的应用。     

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.     

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.     

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.     

Adsorption of Bromate From Aqueous Solutions by Modified Granular Activated Carbon: Batch and Column Tests

Bromate by-product formation during ozonation of bromide-containing potable water has aroused widespread concern. In this study, cetylpyridinium chloride was selected to modify two different kinds of granular activated carbon (GAC) to improve their bromate adsorption capacity. The adsorption characteristics of modified GAC were studied by batch and column tests, with results suggesting greatly improved bromate adsorption ability: the saturation capacities for bromate were >7 times for modified GAC than for GAC under the experimental conditions used. This enhancement in adsorptive capacity is likely due to an increase in basic functional groups, because the saturated adsorption capacity of bromate on the GAC is positively correlated with the basic functional groups. The increase of the basic functional groups accelerates OH- dissociation from the GAC surface and protonation of the GAC surface, thus resulting in the enhancement in adsorptive capacity. The modified GAC was relatively immune to the impact of pH change over a broad range. Both the Yoon-Nelson model and the Thomas model fit well the breakthrough curves of bromate adsorbed by modified and unmodified GAC under different conditions. Our results provide insight into the sorption process of bromate onto modified GAC.     

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.     

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。     

Effect of Zeolite Chemical Surface Properties on Catalytic Ozonation of Methylene Blue Contaminated Waters

Heterogeneous catalytic ozonation using natural zeolite has been recently reported. However, there is a lack in the information related to the influence of zeolite active surface sites in this combined system. This work presents experimental results on the effect of zeolite chemical surface properties on catalytic ozonation. Zeolite samples with different chemical surface compositions were prepared from natural zeolite. The effect of pH, and the presence of radical scavengers were assessed at laboratory scale. Results obtained here indicate that hydrous oxide sites present on zeolite surface (S–OH₂ ⁺, S–OH, S–O^?) play a key role on the catalytic ozonation mechanism.     

Decomposition of Dissolved Ozone in the Presence of Activated Carbon: An Experimental Study

In aqueous solutions molecular ozone (O₃) decomposes rapidly into secondary radical or ionic species such as (OH^o,, , …). This decomposition is enhanced by many factors, essentially the pH, the temperature, and the organic or inorganic compounds in the solution. The aim of this work is to study the effect of the addition of granular activated carbon on the rate of ozone decomposition in aqueous solutions containing promoter (P) and inhibitor (Q) mixtures. The activated carbon used is laboratory produced from olive stones. We found that the rate of decomposition of ozone in these conditions is described by a pseudo-first-order kinetic: . Experimental results show that adding 15 mg/L of the olive stones activated carbon (OSAC) enhances the rate constant of the P and Q controlled chain depletion by about a factor of two. We found that the decomposition increases linearly with the solid concentration (W): and that the kinetics are enhanced when the activated carbon specific area increases. We also conclude that the preozonation of the OSAC has no effect on its activity. We note that the temperature has a significant effect on the ozone decomposition rate even in the presence of OSAC. The value of the activation energy in the presence of the OSAC is lower than that obtained in homogeneous decomposition.     

Ozone and Activated Carbon for Tertiary Wastewater Treatment

Preozonation of biologically or physically–chemically treated wastewater effluents, followed by passage through granular activated carbon (GAC) for tertiary wastewater treatment was studied at the Duck Creek Wastewater Treatment in Garland, Texas. Whereas the average period of operation for the GAC before exhaustion without ozone pretreatment was 70 days, pretreatment with ozone or with oxygen alone extended GAC operation to at least 480 days, withoutexhaus–tion. Effluent streams consistently metapplicable discharge standards during this period of time, without the necessity of regenerating the GAC.     

Removal Of Residual Organics From Drinking Water By Ozonation And Activated Carbon Filtration: A Pilot Plant Study

The effects of ozonation, granular (GAC) and biological activated carbon (BAC) in the removal of natural organic matter and precursors of disinfection byproducts from drinking water were studied on pilot scale. Ozonation was determined to be the best method to reduce concentrations of the precursors of AOX, chloroform and mutagenicity, whereas BAC removed organic matter the most effectively. Reductions in TA100 mutagenicity were an average 40%, 4%, 26% in ozonated, GAC and BAC filtered water, respectively. Average reductions of AOX levels were similar at 48%, 7% and 35%, respectively. The chloroform formation potential always increased after GAC filtration.     

Behavior Of Glyoxal During Granular Activated Carbon Treatment

Glyoxal, which was the strong mutagen formed by ozonation of humic substances, was treated with granular activated carbon (GAC) and the behavior of glyoxal was investigated. Glyoxal itself was adsorbed well on GAC at pH 5–7. But, glyoxal increased by GAC treatment of ozonated humic substances when the ozone dose was insufficient to decolorize the humic substances. The precursors of glyoxal may be among other ozonated products which may be changed to glyoxal on GAC.     

Oxone Enhanced Biological Activated Carbon in Denver,Colorado: A Pilot Plant Study

Five parallel ozone and activated carbon systems were compared for their effectiveness in treating unchlorinated effluent from the Denver Metropolitan Sewage Disposal District No. 1 wastewater facility. Data were gathered over four months of continuous operation. The objective of the study was to assess the potential for enhanced carbon column performance through the use of ozone.     

Adsorption Equilibrium of DOC by Activated Carbon and the Influence of Preozonation

A linear isotherm model, modified to account for a non-adsorbable fraction, was found to fit adequately the adsorption equilibrium of organic matter from a tertiary treated wastewater. The isotherm slope varied significantly among sample days, but the range of variability did not exceed a factor of two. A moderate ozone dose (0.5 g O₃/g DOC) enhanced adsorbability in both laboratory and full-scale systems, whereas higher doses appeared to decrease adsorption. Preozonation had little effect on the nonadsorbable portion of DOC.     

Effect of pH on adsorption of 2,4-dinitrophenol onto an activated carbon

The adsorption characteristics of 2,4-dinitrophenol from water onto a granular activated carbon, F-400, were studied at pH 4.3, 7 and 10. Adsorption equilibria of 2,4-dinitrophenol on GAC could be represented by Sips equation. Equilibrium capacity increased with decreasing pH. The differences in the rates of adsorption are primarily attributable to the differences in the equilibrium at the various pHs. Intraparticle diffusion was explained by surface diffusion mechanism. An adsorption model based on the linear driving force approximation (LDFA) was used for simulating the adsorption behavior of 2,4-dinitrophenol in a fixed bed adsorber. Presented at the Int’l Symp. on Chem. Eng. (Cheju, Feb. 8-10, 2001), dedicated to Prof. H. S. Chun on the occasion of his retirement from Korea University.     

硅沸石—1制备方法改进及性能研究

本文阐述了一种制备憎水性分子筛—硅沸石-1的新工艺。测定了这种分子筛气相吸附正己烷、乙醇和水的平衡量,以及液相吸附乙醇和水的平衡量,表明这种分子筛具有良好的亲有机和憎水的吸附性能。通过液相吸附透过曲线实验,表明液相吸附乙醇过程为固膜扩散控制。经Cu~(2+)浸渍的这种分子筛,可使甲醇脱氢制甲醛的转化率的选择性大为提高。     

The Influence of Ozone,Oxygen and Chlorine on Biolocical Activity on Biological Activated Carbon

A laboratory study was conducted into the effects of the treatment of activated sludge effluent with different oxidants on the biodegradability of the organic substances. It was found that, under the experimental conditions described, ozone increased the biodegradability, whereas chlorine had no apparent significant effect. The effect of continuous oxidative pretreataent of activated sludge effluent on microbial populations and the biological activated carbon used subsequently in the process also was studied. It was found that ozone, particularly at a dosage of about 5 mg/L promoted biological activity, while chlorine and oxygen (in addition to the dissolved oxygen already in the effluent) had no significant effect on the biological population size.