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.     

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.     

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。     

Biodergradability and GAC Adsorbability of Micropollutants by Preozonation

In order to evaluate the effect of preozonation on GAC adsorbability and biodegradability and to discuss the performance of BAC, three kinds of batch experiments have been conducted, using humic acid as the test substance. Conclusively, it is recognized that preozonation evidently improves the biodegradability of humic acid, but the equilibrium adsorption constant k, is not changed. However, the adsorption rate is greatly improved. Based on these results and continuous experiments, the characteristics of the removal mechanism of organics by a BAC filter and a GAC filter are compared.     

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.     

Characterization procedure for adsorption of DOC (Dissolved Organic Carbon) from synthetic wastewater

A characterization method to evaluate the composition of background organic matters in terms of adsorbability was presented and applied to synthetic and domestic wastewater. The binomial distribution of DOC (Dissolved Organic Carbon) fraction in relation of a characterizing variable, the Freundlich coefficient, k, was proposed to describe the initial composition of wastewater by a finite number of pseudospecies. This method was tested for removal of DOC by using granular and powdered activated carbons. These experiments enable us to get information on the distribution function of species in the solution. From the results obtained in this work, kinetic experimental data were predicted on the assumption that the diffusion coefficients were unchanged during the experiments. It was confirmed to be effective in determining the initial composition and describing the equilibria of the DOC. From the experiments, it was found that this synthetic solution has a sigmoid type isotherm on activated carbons. This implies that there are two different adsorption regions in a system, favourable and unfavourable cases, depending on the solution concentration. This unfamiliar problem can be solved by using a characterization method based on IAST-Freundlich model.     

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.     

中孔活性碳纤维及其吸附特性

活性碳纤维具有丰富的有效吸附孔,孔径分布窄,吸脱行程短,吸脱速度快,吸附容量大。是,一般活性碳纤维的孔径较小,限制了对大分子的吸附,使其应用受到一定限制,近年来,科学工作者进行了中孔型活性炭纤维的研制,以拓宽其应用领域,本文着重阐述了中孔活性碳纤维的制造方法及其吸附特性。     

The Adsorption and Desorption Characteristics of EDTA-Chelated Copper Ion by Activated Carbon

Abstract

This paper addresses the effect of EDTA, a strong agent, on the removal of copper ion from solutions using activated carbon adsorption. Experimental studies indicate the presence of EDTA significantly altered the adsorption behavior of copper on the activated carbon due to the formation of copper chelate species in the solution. The adsorption isotherms and kinetics were found to be strong functions of solution pH and the ratio of copper ion and EDTA concentrations. Adsorption of EDTA-Cu chelates was found to be more favorable than those of free copper ion and unbound EDTA species in the solution. Experimental results indicated that the desorption of chelated copper ion from activated carbon by NaOH and HClO⁴ solutions was influenced by the initial adsorption conditions. A significantly higher quantity of copper ion was recovered with HClO⁴ than with NaOH. Combining the adsorption and desorption data of copper and EDTA, and an understanding of the species distribution of copper in the presence of EDTA, the behavior of the adsorption of EDTA-chelated copper on the activated carbon was described. The predominant adsorbed copper species was the chelated form, CuEDTA^2-, which can be adsorbed on activated carbon surfaces with either the Cu end or the EDTA end bonding directly to the surface.     

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.     

Impact of Drinking Water Preozonation on Granular Activated Carbon Quality and Performance

A bench-scale laboratory system was set up to study the impact of residual ozone on the properties and performance of granular activated carbon (GAC). Simulating a carbon service life of two years, the study demonstrated that the effect of residual ozone was minimal and was the same as aerated or nitrogen-purged waters. Dissolved oxygen did modify the surface properties of GAC, with some impact on the adsorptive properties of exposed carbon. However, after thermal reactivation, the physical and adsorptive properties were comparable to reactivated virgin carbon.     

Effect of Catalytic Ozonation Coupling with Activated Carbon Adsorption on Organic Compounds Removal Treating RO Concentrate from Coal Gasification Wastewater

This paper reports a novel system of catalytic ozonation coupling with activated carbon adsorption for removing the organic compounds treating in the RO concentrate from coal gasification wastewater. The effect of ozone dosage, catalyst dosage, reaction time, influence pH, and temperature on organic compounds removal were examined for the processes. In the catalytic ozonation process, increasing solution pH, dosages ozone, and catalyst were statistically significant for improving the performance. In addition, the high salinity with chloride concentration of 15 g/L could reduce the catalyst specific surface area by 18%. Thus, high salinity showed negative influence on the catalytic effect in TOC removal. Regarding activated carbon adsorption process, modified activated carbon by NaOH revealed advantages in adsorbing organic compounds treating catalytic ozonation effluent. With the ozone dosage of 120 mg/L, catalyst dosage of 2.0 g/L, catalytic ozonation reaction time of 1 h, and modified activated carbon adsorption time of 1 h, the average TOC removal efficiencies were maintained at the stable level of 58% with the TOC concentration of 26 mg/L.     

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 Behavior of Basic Dyes on Activated Clay

Abstract

Activated clay was used to study the adsorption behavior of dyestuffs in synthetic wastewater containing dyestuffs. Three basic dyes were used: C.I. Basic Red 18 (or BR18), C.I. Basic Red 46 (BR46), and C.I. Basic Yellow 28 (BY28). Adsorption occurred almost instantaneously upon contact. The mechanism of adsorption was explained by a charge to the electrostatic attractive force described in the Langmuir adsorption isotherm. The mass transfer coefficient was also calculated by the external mass transfer model in an adsorbent according to Mckay et al. Parameters including species of basic dyes, initial concentration, temperature, size of adsorbent, and NaCl were extensively investigated.     

Application of characterization procedure in water and wastewater treatment by Adsorption

The background organics in water and wastewater are necessary to fractionate into groups or components according to the difference in adsorbability. In this study, the background organics were fractionated in terms of the adsorptive strength described by the Freundlich isotherm constants k and n with the assumption that the fractionated components differ in the value of k but have the same value of n based on the IAST (Ideal Adsorption Solution Theory) using binomial concentration distribution. A simple characterization for water and wastewater with a certain amount of DOC in terms of adsorbability was applied to three types of organic mixtures contained in different water sources. The composition of each organic mixture was successfully evaluated to describe the IAE (Integral adsorption experiments) data of the total organic carbon by using this characterization procedure. Batch experiments as well as the membrane-PAC hybrid system experiments were conducted with three different types of PACs.     

活性炭纤维对水中酸性大红的吸附脱色研究

研究了活性炭纤维(ACF)对水中酸性大红的吸附脱色试验。温度为15℃~20℃,滤速为6mL/min时,浓度为12mg/L的酸性大红脱色率达98％以上。活性炭纤维经20次吸附与解吸实验,吸附脱色性能没有明显降低。与颗粒状活性炭(GAC)相比,活性炭纤维吸附脱色酸性大红的吸附量大,可望作为对吸附脱色酸性大红废水的方法。     

Adsorption of SO2 on Activated Carbon for Low Gas Concentrations

Adsorption experiments of SO₂ on activated carbon has been carried out for low concentrations (about 100 ppm) at room temperature (15 to 33 °C) with varying humidity in the air. The breakthrough curves show that at high relative humidity or relative higher SO₂ concentration, the load capacity increases with respect to temperature. The humidity of the air is also of benefit to the load capacity of SO₂. When an adsorption process is interrupted and the activated carbon is kept closed for a while, the SO₂ concentration at the exit of a fixed‐bed adsorber is similar to that of the fresh activated carbon and begins at a very low value. It appears that the sorption potential has been refreshed after the storage period. Analysis of desorption experiments by simultaneous thermal analysis combined with mass spectrometry (MS) after loading, shows that the physisorbed SO₂ and H₂O are desorbed at low temperatures. At higher temperatures, the MS peak of SO₂ and H₂O occur at the same time. Compared with desorption immediately after loading, after one day, the desorption peak due to the physisorbed SO₂ disappears. From this, it can be concluded that the refreshment of the loading capacity of the activated carbon after storage is mainly due to a change in the nature of the SO₂ from a physisorbed state to a chemisorbed form. The same mechanism leads to a continuous refreshment of the sorption potential by means of a chemical reaction during the adsorption process.     

Adsorption Characteristics of Atrazine on Granulated Activated Carbon and Carbon Nanotubes

Adsorption of atrazine (ATZ) from aqueous solutions by granular activated carbon (GAC) and carbon nanotubes (CNT) was studied in a batch‐mode adsorption system at different initial concentrations of ATZ (1.0–30.0 mg L^–1) and at three temperatures of 288, 296 and 304 K. The adsorption isotherms of Langmuir, Freundlich, Polanyi–Manes, and Brunauer–Emmett–Teller (modified) were used to model the process. The adsorption kinetics followed a pseudo‐second‐order kinetic model. The thermodynamic parameters ΔH⁰, ΔS⁰, and ΔG⁰ of the adsorption were estimated. The thermodynamic parameters indicate that the adsorption process is spontaneous and exothermic.     

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。