Adsorption of natural organic matter oxidized with ClO2 on granular activated carbon

The paper describes the influence of the oxidation of natural organic matter (NOM) molecules with chlorine dioxide (ClO2) on granulated activated carbon (GAC) adsorption. In order to determinate the influence of ClO2 dosage on the NOM adsorption on GAC two parallel pilot scale experiments were performed. The raw water was treated respectively with 0.2 and 0.4 mg ClO2 L(-1) followed by the adsorption on GAC filters. Experiments were total organic carbon (TOC) measurements and size exclusion chromatography (SEC) controlled. The molecular weight distribution of NOM in the filtration bed outlet demonstrates that the low molecular weight molecules are less retained than the higher molecular weight components of NOM. It is shown that low molecular weight NOM causes less ClO2 demand. The oxidation of NOM molecules and very high capacity of GAC filter bed for NOM components can be used to control high ClO2 demand.     

Adsorption of Sevin and Baygon on granular activated carbon

Adsorption of Sevin and Baygon on granular activated carbon was investigated. Adsorption parameters of Freundlich and Langmuir isotherms are useful indications of the adsorption capacity of carbon and the anticipated sharpness of breakthrough front. Adsorption of tested carbamates depends on their chemical structure and branching of the side chains. Contact time tends to be the most important factor controlling the efficiency of the adsorption process and a linear relationship was obtained between the logarithm of contact time and volume of effluent passing the column before breakthrough of Sevin.     

Adsorption of soluble aromatic hydrocarbons on granular activated carbon

Adsorption of benzene, toluene, o-oxylene and ethylbenzene on granular activated carbon proceeds in accordance with the Freundlich model. Adsorption parameters, k and 1/n, reflect the effects of chemical structure, solubility and competitive interactions on the adsorption process. Results obtained add to the validity of the carbon column technique in the removal of soluble aromatic hydrocarbons that affect water quality.     

Characterization of natural organic matter adsorption in granular activated carbon adsorbers

The removal of natural organic matter (NOM) from lake water was studied in two pilot-scale adsorbers containing granular activated carbon (GAC) with different physical properties. To study the adsorption behavior of individual NOM fractions as a function of time and adsorber depth, NOM was fractionated by size exclusion chromatography (SEC) into biopolymers, humics, building blocks, and low molecular weight (LMW) organics, and NOM fractions were quantified by both ultraviolet and organic carbon detectors. High molecular weight biopolymers were not retained in the two adsorbers. In contrast, humic substances, building blocks and LMW organics were initially well and irreversibly removed, and their effluent concentrations increased gradually in the outlet of the adsorbers until a pseudo-steady state concentration was reached. Poor removal of biopolymers was likely a result of their comparatively large size that prevented access to the internal pore structure of the GACs. In both GAC adsorbers, adsorbability of the remaining NOM fractions, compared on the basis of partition coefficients, increased with decreasing molecular size, suggesting that increasingly larger portions of the internal GAC surface area could be accessed as the size of NOM decreased. Overall DOC uptake at pseudo-steady state differed between the two tested GACs (18.9 and 28.6 g-C/kg GAC), and the percent difference in DOC uptake closely matched the percent difference in the volume of pores with widths in the 1-50 nm range that was measured for the two fresh GACs. Despite the differences in NOM uptake capacity, individual NOM fractions were removed in similar proportions by the two GACs.     

Adsorption of p-nitrophenol on activated carbon fixed-bed

Carbon fixed-beds are usually used to remove organic contaminants. Adsorption in a carbon filter is a dynamic, non-steady process which is not yet completely understood. The objective of this paper is to establish a methodology to simplify the study of this process based on the wave theory, rapid small-scale column test and experimental design/surface response analysis. The constant pattern wave hypothesis was confirmed by the experimental data. The influence of the inlet concentration of p-nitrophenol and the flow rate on dynamic adsorption was studied at 20 degrees C following a central composite design using a second-order model. Both parameters have an important influence on the response variables studied. The methodology used is a useful tool for studying the dynamic process and shows interactions that are difficult to verify by the classical step-by-step method.     

Adsorption of anionic and cationic dyes on activated carbons with different surface chemistries

The influence of the surface chemical groups of an activated carbon on the removal of different classes of dyes is evaluated. Starting from the same material (NORIT GAC 1240 PLUS), the following treatments were carried out in order to produce a series of samples with different surface chemical properties but with no major differences in their textural properties: oxidation in the liquid phase with 6M HNO(3) and 10 M H(2)O(2) (acid materials) and heat treatment at 700 degrees C in H(2) or N(2) flow (basic materials). The specific micropores volume and mesopores surface area of the materials were obtained from N(2) adsorption equilibrium isotherms at 77K. The surface chemistry was characterised by temperature programmed desorption, by the determination of the point of zero charge (pH(pzc)) and by the evaluation of the acidity/basicity of the samples. Elemental and proximate analyses were also carried out. Equilibrium isotherms of selected dyes (an acid, a basic and a reactive dye) on the mentioned samples were obtained and the results discussed in relation to their surface chemistry. In general, the Langmuir model provided the best fit for the adsorption data. It is shown that the surface chemistry of the activated carbon plays a key role in dye adsorption performance. The basic sample obtained by thermal treatment under H(2) flow at 700 degrees C is the best material for the adsorption of all the tested dyes.     

Adsorption of non-ionic surfactants on activated carbon and mineral clay

A series of non-ionic surfactants of nonyl-phenol ethoxylates, with n = 4?23;0 ethylene oxide groups and dinonyl-phenol ethoxylate were studied in dilute aqueous solution. Their removal efficiencies and mechanisms by adsorption on powdered and granular activated carbon and on Na-montmorillonite clay were investigated. The powdered activated carbon proved to be the most efficient with 94–100% non-ionic surfactants removal by addition of 40–80 mg activated carbon.Various models of adsorption isotherms such as Langmuir, BET and S-type were used to determine Q⁴, the limiting adsorption capacity. The relationships between Q^o and parameters affecting the adsorption of non-ionic surfactants such as n, HLB and CMC were determined. The cross-sectional area σ₀ occupied by surfactant molecules on the adsorbent was calculated. Adsorption has been proven to be a potential advanced physicochemical treatment method for the effective removal of non-ionic surfactants present in effluents intended for reuse.     

Adsorption of organic compounds onto activated carbon

Adsorption isotherms of acetone, propionaldehyde, methylisobutylketone and sucrose from aqueous solutions onto granular activated carbon have been determined.Multi-solute data have been compared with the theoretical prediction obtained from ideal adsorbed solution model.The agreement between calculated and observed results is satisfactory. Only the system sucrosemethylisobutylketone shows significant deviation between experimental and predicted values. Therefore the model can be successfully utilized in design of activated carbon units.     

粉末活性炭对马拉硫磷的吸附性能研究

以马拉硫磷作为突发性污染物,考察了粉末活性炭对其的吸附效果。试验结果表明,粉末活性炭对纯水和滤后水中的马拉硫磷均具有较好的去除效果,对前者的去除效果更为明显,去除率随活性炭投加量的增加而升高。当马拉硫磷浓度为1.25 mg/L,纯水、滤后水中的活性炭投加量分别为12.0和20 mg/L时,反应120 min后马拉硫磷剩余浓度均低于0.25 mg/L。对滤后水而言,药剂费用约为0.06～0.08元/m3。     

Adsorption and desorption of trace organic contaminants from granular activated carbon adsorbers after intermittent loading and throughout backwash cycles

A granular activated carbon (GAC) adsorption simulation methodology using the observed trace organic contaminant mid-point breakthrough and the pore diffusion model is presented, validated, and used to model adsorption and concentration gradient driven desorption. Trace organic contaminant adsorption was well-simulated by this approach; however, desorption from GAC adsorbers was found to occur at lower concentrations than predicted by either pore or surface diffusion model calculations. The observed concentration profiles during desorption yielded a lower peak concentration and more elongated attenuation of contaminants after intermittent loading conditions than predicted by the models. Hindered back diffusion caused by irreversibly adsorbed dissolved organic matter on the GAC surface is hypothesized to be responsible for slowing the desorption kinetics. In addition, laboratory test results indicate a negligible impact of simulated backwashing the GAC media on trace organic contaminant breakthrough.     

Iron amendment and Fenton oxidation of MTBE-spent granular activated carbon

Fenton-driven regeneration of methyl tert-butyl ether (MTBE)-spent granular activated carbon (GAC) involves an Fe amendment step to increase the Fe content and to enhance the extent of MTBE oxidation and GAC regeneration. Four forms of iron (ferric sulfate, ferric chloride, ferric nitrate, ferrous sulfate) were amended separately to GAC. Following Fe amendment, MTBE was adsorbed to the GAC followed by multiple applications of H₂O₂. Fe retention in GAC was high (83.8-99.9%) and decreased in the following order, FeSO₄·7H₂O > Fe₂(SO₄)₃·9H₂O > Fe(NO₃)₃·9H₂O > FeCl₃. A correlation was established between the post-sorption aqueous MTBE concentrations and Fe on the GAC for all forms of Fe investigated indicating that Fe amendment interfered with MTBE adsorption. However, the mass of MTBE adsorbed to the GAC was minimally affected by Fe loading. Relative to ferric iron amendments to GAC, ferrous iron amendment resulted in lower residual iron in solution, greater Fe immobilization in the GAC, and less interference with MTBE adsorption. MTBE oxidation was Fe limited and no clear trend was established between the counter-ion (SO₄²⁻, Cl⁻, NO₃⁻) of the ferric Fe amended to GAC and H₂O₂ reaction, MTBE adsorption, or MTBE oxidation, suggesting these processes are anion independent.     

Adsorption of Bacillus subtilis on single-walled carbon nanotube aggregates, activated carbon and NanoCeram

Adsorption equilibrium and kinetics of Bacillus subtilis spores on single-walled carbon nanotube aggregates were investigated to explore the possibility of using single-walled carbon nanotubes for concentration, detection and removal of pathogens from contaminated water sources. Batch adsorption experiments were conducted to determine adsorption kinetics and adsorption equilibrium of B. subtilis spores on single-walled carbon nanotube aggregates, activated carbon and NanoCeram™. The adsorption kinetics data were analyzed with both the Lagergren pseudo first order and a pseudo second order models. The adsorption equilibrium data on three porous media were quantified by the Henry's law constant. It was observed that both the Lagergren first order rate model and the pseudo second order model correlate the adsorption kinetic data well although the calculated adsorption rate constants vary with adsorbate concentrations. The Henry's law adsorption equilibrium constant of B. subtilis spores on single-walled carbon nanotube aggregates is about 27-37 times higher than those on activated carbon and NanoCeram™. The high adsorption affinity of carbon nanotubes towards the B. subtilis spores is due to the mesoporous structure and unique surface properties of carbon nanotubes. These results suggest that single-walled carbon nanotube aggregates are good candidates as biosensors and adsorbent media for concentrating, detecting and removal of pathogens from contaminated water resources.     

Adsorption of chlorinated organic compounds on activated carbon from water

The adsorption capacities and rates of seven principal chlorinated organic compounds for six commercial GACs were investigated. All the adsorption isotherms were expressed by the Freundlich equation, and the isotherms for the chloroethylenes such as trans - 1,2-dichloroethylene, trichloroethylene and tetrachloroethylene could be shown by the modified Freundlich equation Q′ = k′ (C/C_s)^l/n for each GAC. The magnitude of adsorption of the chlorinated organic compounds was in the order of: tetrachloroethylene > trichloroethylene > trans - 1,2-dichloroethylene > 1,1-dichloroethane > carbontetrachloride > 1.1,1-trichloroethane > chloroform. The value of k for a certain GAC could be predicted from the quantity of pores smaller than 2 nm in diameter. The adsorbed amounts were decreased by 10–20% when humic substances coexisted. The working periods of a fixed bed adsorber before regeneration were predicted by calculating breakthrough curves for various influent concentrations of trichloroethylene and tetrachloroethylene at the space velocities of 5 or 10 h⁻¹, and it was certified that the adsorption method by GAC was feasible for removing these compounds from water.     

粉末活性炭对邻苯二甲酸二乙酯的吸附性能研究

考察了投加粉末活性炭吸附去除水中邻苯二甲酸二乙酯的可行性,并采用Freundlich公式拟合纯水和原水条件下的等温吸附方程。试验结果表明,采用粉末活性炭可有效去除水中邻苯二甲酸二乙酯,活性炭投加量为30mg／L,吸附120min后,纯水和原水条件下邻苯二甲酸二乙酯去除率分别为93．3％和89．3％。根据吸附等温方程计算得出,以邻苯二甲酸二乙酯的标准限值（0．3mg／L）为平衡浓度,纯水、原水条件下最大投炭量（80mg／L）可应对的邻苯二甲酸二乙酯最高质量浓度分别为7．575和5．731mg／L。     

粒状活性炭在饮用水深度处理中的应用及再生

介绍了粒状活性炭在饮用水处理中的应用、所起的作用以及活性炭工艺对原水的处理效果,同时也对活性炭的再生进行了论述.实践证明,活性炭工艺在饮用水的深度处理过程中起了重要的作用.     

Adsorption of tri- and tetra-chloroethylene from aqueous solutions on activated carbon fibers

Recently the contamination of groundwater by trichloroethylene and related compounds have become a new environmental problem. As the first step to clarify the feasibility of applying newly developed adsorbent, activated carbon fiber (ACF), to adsorption treatments of water taken from such a contaminated groundwater source, the adsorption equilibrium and the adsorption rate of trichloroethylene and tetrachloroethylene from aqueous solutions on four ACFs with different pore-size distribution were investigated. The adsorption capacities of ACFs having larger volume of micropores are larger than those of granular activated carbons (GACs) usually used at present. Also, the adsorption rate on ACFs is far more rapid in comparison with GAC adsorption because of smaller diffusion path.     

Adsorption of copper, lead and cobalt by activated carbon

The phenomena of lead, copper and cobalt adsorption by activated carbon from aqueous solution was studied in detail. Laboratory studies were conducted to evaluate and optimize the various process variables (i.e. carbon type, solution pH, equilibrium time and carbon dose). A quantitative determination of the adsorptive capacity of activated carbon to remove these metals was also determined.Significant differences were found in the ability of different types of activated carbons to adsorb lead, copper and cobalt from aqueous solution. Solution pH was found to be the most important parameter affecting the adsorption. It was found that there was practically no adsorption of lead, copper and cobalt by activated carbon below a well defined solution pH value for each metal. This critical solution pH value was found to be lower than the pH value associated with the formation of hydrolysis products. Of the ten commercially available activated carbons evaluated in these experiments, Barney Cheney NL 1266 was found to adsorb the largest percentage of lead, copper and cobalt. The adsorption of any single metal (lead, copper and cobalt) was hindered by the presence of the other metals; the metals apparently competed for adsorption sites.     

粉末活性炭对水中呋喃丹的吸附性能研究

考察了粉末活性炭吸附去除水中呋喃丹的可行性,并采用Freundlich公式拟合去离子水和自来水条件下的吸附等温方程.结果表明,采用粉末活性炭可有效去除水中的呋喃丹,在去离子水条件下,呋喃丹初始质量浓度为0.035 mg/L,投炭量为20 mg/L,吸附时间为120 min时,呋喃丹的去除率大于98％.根据吸附等温方程计...     

粉末活性炭对内吸磷的吸附性能研究

研究了粉末活性炭对內吸磷的吸附去除效果以及吸附时间、活性炭投加量和水质条件对吸附效果的影响.结果表明,当內吸磷质量浓度为0.30 mg/L,活性炭投加量为20 mg/L时,在去离子水中吸附60 min后,出水內吸磷为0.02 mg/L;在去离子水中的吸附效果优于原水,在实际应用中需根据原水水质适当调整活性炭投加量或吸附...