Trihalomethanes Adsorption on Activated Carbon Fiber and Granular Activated Carbon

Isotherms and the effects on activated carbon fiber (ACF), compared with granular activated carbon (GAC), adsorption of trihalomethans (THMs) in water were studied. It was found that the isotherms for ACF or GAC were not agree to Langmuir equation well, but successfully correlated by Freundlich equation, and the coefficients of Freundlich isotherm were given and compared to isotherms reported in the literatures for THMs. ACF and GAC adsorbing THMs was exothermic, isotheric heats of adsorption were calculated and increased with increasing bromine substitution in CHCl₃. The adsorptive capacity of ACF was about two-fold greater than that of GAC, and increased with THMs more hydrophobic or bromine substitution. pH value and temperature had no significant effect on the adsorptive capacity of ACF. The adsorptive capacity of GAC was decreased with temperature slightly. The adsorptive capacities of ACF or GAC was increased with the THMs initial concentration rising. Fixed-bed reactor studies were measured, the amount of THMs adsorbed on ACF column at saturation was much greater than that of GAC at the same operating conditions, and the running time of ACF column was two-fold longer than that of GAC column. The mass transfer zones of ACF column were less than those of GAC column and decreased as the chlorine atoms in CHCl₃ substituted by bromine atoms, while the mass transfer zones of GAC column were quite uniform.     

Adsorption of Nonylphenol onto Granular Activated Carbon

The applicability of granular activated carbon (GAC)filtration for the removal of the xeno-estrogenicmicropollutant nonylphenol (NP) is evaluated using batchadsorption data. From the obtained adsorption data, it wasapparent that with contact times of 4 d and 24 hr and GACdosages of 1 and 0.1 g L^-1 no saturationof the GAC could be obtained with NP total contaminantloadings up to 10 000 μg L^-1.Higher NP concentrations could not be applied due to its lowwater solubility (～5 mg L^-1). The influence of temperature(4 or 28 °C) on NP sorption onto GAC was negligible.The results showed that the sorption capacity of GAC for NPwas at least 100 mg g^-1 GAC. According to thesedata it can be concluded that a full-scale GACfilter unit will be sufficient to remove environmentallyrelevant NP concentrations of 10 μg L^-1.Consequently, the existing GAC treatment technology indrinking water treatment should protect the consumer from theintake of the xeno-estrogenic micropollutant NP via drinkingwater. The sorption capacity of dissolved humic acids (DHA)for NP is considerable at liquid NP concentrations of 10 μgL^-1 and the affinity of DHA for GAC is not significant.These observations suggest that interference on removal of NP onGAC, due to the presence of DHA, can be expected at microgramper liter concentrations of NP. They may warrant the removalof humic substances in treatment steps preceding GAC-filtration.     

Enhanced Adsorption of Metal Ions Onto Polyethyleneimine-Impregnated Palm Shell Activated Carbon: Equilibrium Studies

In this study, palm shell activated carbon was impregnated with polyethyleneimine (PEI) and the effect of impregnation on batch adsorption of Ni²⁺, Cd²⁺or Pb²⁺ as well as the equilibrium behavior of adsorption of metal ions on PEI-impregnated AC were investigated. PEI impregnation evidently increased the single metal adsorption capacities of Ni²⁺ or Cd²⁺except for Pb²⁺, where its adsorption capacities were reduced by 16.67% and 19.55% for initial solution pH of 3 and 5 respectively. This suggested that PEI-impregnated AC could be used for selective separation of Pb²⁺ ions from other metal ions. The adsorption data of all the metal ions on both virgin and PEI-impregnated AC for both initial solution pH of 3 and 5 generally fitted the Langmuir and Redlich-Peterson isotherms considerably better than the Freundlich isotherm.     

Kinetic and Equilibrium Sorption Studies of Ceftriaxone and Paracetamol by Surfactant-Modified Zeolite

An organo-zeolite was prepared by loading hexadecyltrimethylammonium (HDTMA) onto clinoptilolite and was used to remove ceftriaxone sodium and paracetamol in aqueous solutions. Batch experiments were conducted to perform kinetics and sorption isotherms at 25 °C and 100 rpm. The results indicate that the equilibration times were 24 h for ceftriaxone sodium and 9 h for paracetamol. Furthermore, sorption capacities were 0.7288 and 0.0058 mg/g, respectively. The data were treatment with different models including pseudo first order, second order, and Elovich, the results suggested a chemical adsorption mechanism, and the adsorption equilibrium data for the two drugs show that they follow a linear trend, indicating a partitioning mechanism. Physicochemical properties such as solubility, log Kow, and pka play an important role in the adsorption process. Finally, the values obtained for zero charge point (ZPC) for zeolitic materials were 6.90, 6.94, and 6.90 for natural zeolite (ZN), sodium zeolite (ZNa), and zeolite modified surface at 30 mM HDTMA (ZMS-30), respectively.     

Removal of Remazol Brilliant Blue Dye from Dye-Contaminated Water by Adsorption Using Red Mud: Equilibrium, Kinetic, and Thermodynamic Studies

Utilization of industrial solid wastes for the treatment of wastewater from another industry could help environmental pollution abatement, in solving both solid waste disposal as well as liquid waste problems. Red mud (RM) is a waste product in the production of alumina and it poses serious pollution hazard. The present paper focuses on the possibility of utilization of RM as an adsorbent for removal of Remazol Brilliant Blue dye (RBB), a reactive dye from dye-contaminated water. Adsorption of RBB, from dye-contaminated water was studied by adsorption on powdered sulfuric acid-treated RM. The effect of initial dye concentration, contact time, initial pH, and adsorbent dosage were studied. Langmuir isotherm model has been found to represent the equilibrium data for RBB?CRM adsorption system better than Freundlich model. The adsorption capacity of RM was found to be 27.8?mg dye/g of adsorbent at 40?°C. Thermodynamic analysis showed that adsorption of RBB on acid-treated RM is an endothermic reaction with ?H ⁰ of 28.38?kJ/mol. The adsorption kinetics is represented by second-order kinetic model and the kinetic constant was estimated to be 0.0105?±?0.005?g/mg?min. Validity of intra-particle diffusion kinetic model suggested that among the mass transfer processes during the dye adsorption process, pore diffusion is the controlling step and not the film diffusion. The process can serve dual purposes of utilization of an industrial solid waste and the treatment of liquid waste.     

Performance of L-493 Macroprous Resin for Adsorption of Trihalomethanes from Water

Water, Air, & Soil Pollution - Microbial fuel cells (MFCs) have gained increasing attention as an effective pathway for wastewater treatment and electrical energy recovery. In this study, the...     

Equilibrium and Kinetic Characteristic of Adsorption of Cu2+, Pb2+ on a Novel Anionic Starch Microspheres

Neutral starch microspheres (NSMs) were synthesized with epichlorohydrin as the cross-linking agent from soluble starch by inverse microemulsion method. Anionic starch microspheres (ASMs) were prepared from NSMs by the secondary polymerization with chloroacetic acid as the anionic etherifying agent. Scanning electron microscopy (SEM) revealed that microspheres had good sphericity and fine dispersibility, and the average particle size was about 75 ??m. The adsorption procedure of Cu²⁺, Pb²⁺ on ASMs was carried out by batch experiments, Langmuir and Freundlich adsorption models were applied to describe the experimental isotherms, the adsorption equilibrium data were found to fit the Langmuir and Freundlich isotherm model, the Freundlich isotherm was more adequate than the Langmuir isotherm in simulating the adsorption isotherm of Cu²⁺,the adsorption of Cu²⁺, Pb²⁺ on ASMs was a spontaneous, the isosteric heat of adsorption at different adsorption levels was always negative and indicative of an exothermic process. The pseudo first- and second-order kinetic models were used to describe the kinetic data, and the rate constants were evaluated. The experimental data fitted well to the second-order kinetic model, which indicated that the chemical sorption was the rate-limiting step, instead of mass transfer.     

Kinetic,Thermodynamic, and Adsorption Behavior of Cationic and Anionic Dyes onto Corn Stigmata: Nonlinear and Stochastic Analyses

The potential to remove methylene blue (MB) basic dye and indigo carmine (IC) acidic dye, from wastewater treatment systems using corn stigmata through biosorption was investigated in batch experiments. The effects of contact time, solution pH, biosorbent dosage, initial dye concentration, salts, and temperature were sought. Results showed that the maximal uptakes of MB were 106.3 mg g^?1 at pH?=?7 and 63.7 mg g^?1 for IC at pH?=?2. In order to determine the properties and surface structure of the biomass physicochemical properties (pH_pzc, elemental analysis, Boehm’s titration, and chemical composition), spectral (FTIR analysis) and morphological characteristics (SEM) were investigated. Random distribution of the active sites was described by the new biosorption fractal model of Brouers–Sotolongo. The thermodynamic study demonstrated the favorable character of the biosorption of MB and of IC, which was inhibited by the presence of salts. The elucidation of the biosorption mechanism showed that the biosorption of MB onto corn stigmata was mainly controlled by chemisorption and the biosorption of IC was described by physisorption.     

Competitive Adsorption of Some Hazardous Organic Pollutants from their Binary and Ternary Solutions onto Granular Activated Carbon Columns

Water, Air, & Soil Pollution - Competitive adsorption of some priority pollutants, namely phenol, o-cresol, p-nitrophenol, m-methoxyphenol, benzoic acid and salicylic acid from their aqueous...     

Competitive Adsorption of Some Hazardous Organic Pollutants from their Binary and Ternary Solutions onto Granular Activated Carbon Columns

Competitive adsorption of some priority pollutants, namely phenol, o-cresol, p-nitrophenol, m-methoxyphenol, benzoic acid and salicylic acid from their aqueous solutions onto granular activated carbon (GAC) column was studied. Experiments were carried out to determine the breakthrough curves for adsorbates when present in aqueous solutions as single-, bi- and tri-solute system to evaluate the competitive adsorption phenomenon. Results indicate that in single-solute-GAC systems, p-nitrophenol is most strongly adsorbed as compared to other phenol derivatives studied. The substituted phenols were found to adsorb to a greater extent than phenol itself. The GAC-bisolute and GAC-trisolute systems clearly show the competitive or preferential adsorption of one solute over the other, as the solutes are competing for the available GAC surface for adsorption. Initially, all the adsorbates are taken up by the GAC surface, but near the breakthrough point the more adsorbable solute is able to desorb the less adsorbable one.     

Equilibrium, Kinetics and Mechanism of Removal of Methylene Blue from Aqueous Solution by Adsorption onto Pine Cone Biomass of Pinus radiata

The kinetics and mechanism of methylene blue adsorption onto raw pine cone biomass (Pinus radiata) was investigated under various physicochemical parameters. The extent of the methylene blue dye adsorption increased with increases in initial dye concentration, contact time and solution pH but decreases with the amount of adsorbent, salt concentration and temperature of the system. Overall the kinetic studies showed that the methylene blue adsorption process followed pseudo-second-order kinetics among various kinetic models tested. The different kinetic parameters including rate constant, half-adsorption time and diffusion coefficient are determined at different physicochemical conditions. Equilibrium data were best represented by Langmuir isotherm among Langmuir and Freundlich adsorption isotherm. The maximum monolayer adsorption capacity of pine cone biomass was 109.89 mg/g at 30°C. The value of separation factor, R _L, from Langmuir equation and Freundlich constant, n, both give an indication of favourable adsorption. Thermodynamic parameters such as standard Gibbs free energy (?G ⁰), standard enthalpy (?H ⁰), standard entropy (?S ⁰) and the activation energy (A) were calculated. A single-stage batch absorber design for the methylene blue adsorption onto pine cone biomass has been presented based on the Langmuir isotherm model equation.     

Adsorption behavior of the catechins and caffeine onto polyvinylpolypyrrolidone

Adsorbent is one of the most important factors for separation efficiency in fixed-bed purification techniques. The adsorption behavior of catechins and caffeine onto polyvinylpolypyrrolidone (PVPP) was investigated by static adsorption tests. The results showed that catechins rather than caffeine were preferred to adsorb onto PVPP since the adsorption selectivity coefficient of total catechins vs caffeine was around 22.5, and that adsorption of catechins could be described by the pseudo-second-order model. Adsorption amount of caffeine onto PVPP in green tea extracts solution was much higher than that in purified caffeine solution although the initial concentration of caffeine was similar in the two solutions, indicating the caffeine might be attached with catechins which were adsorbed by PVPP instead of being adsorbed by PVPP directly. The results also showed that the adsorption capacity of catechins and caffeine decreased with an increase in temperature, and that Freundlich and Langmuir models were both suitable for describing the isothermal adsorption of catechins, but not suitable for caffeine. The predicted maximum monolayer adsorption capacity of total catechins by PVPP was 671.77 mg g(-1) at 20 °C, which was significantly higher than that by other reported adsorbents. The thermodynamics analyses indicated that the adsorption of catechins onto PVPP was a spontaneous and exothermic physisorption process, revealing lower temperature was favorable for the adsorption of catechins. Elution tests showed that the desorption rates of catechins and caffeine were higher than 91% and 99% after two elution stages; in detail, almost all of the caffeine could be washed down at the water eluting stage, while catechins could be recovered at the dimethyl sulfoxide/ethanol solution eluting stage. Thus, the PVPP could be used as an excellent alternative adsorbent candidate for separating catechins from crude tea extracts, although some investigations, such as exploring the new eluants with low boiling point and high desorption efficiency, should be conducted furthermore.     

磷酸盐在水铁矿及水铁矿-胡敏酸复合体表面的吸附

The adsorption of phosphate onto ferrihydrite (FH) and two FH-humic acid (HA) complexes, obtained by co-precipitating FH with low (FH-HA1) and relatively high amounts of humic acid (FH-HA2), was studied through kinetics and isotherm experiments to determine the differences in phosphate adsorption between FH-HA complexes and FH and to reveal the mechanism of phosphate adsorption onto two soil compositions. The isoelectric point (IEP) and the specific surface area (SSA) of the mineral decreased as the particle porosity of the mineral increased, which corresponded to an increase in the amount of organic carbon. The adsorption capacity of phosphate was higher on FH than on FH-HA1 and FH-HA2 at the scale of micromoles per kilogram. The initial adsorption rate and adsorption affinity of phosphate decreased with an increase in the amount of HA in the mineral. The sensitivity of phosphate adsorption to the change in the pH was greater for FH than for FH-HA complexes. Ionic strength did not affect the adsorption of phosphate onto FH and FH-HA1 at a lower pH, and the increase in the ionic strength promoted phosphate adsorption at a higher pH. However, for the FH-HA2 complex, the increase in the ionic strength inhibited the adsorption of phosphate onto FH-HA2 at a lower pH and increased the adsorption at a higher pH.     

几种吸附剂对阿特拉津的吸附及其 Zeta 电位特性研究

通过振荡吸附平衡试验,研究了蒙脱石、凹凸棒石、竹炭、木炭对阿特拉津的吸附行为,讨论了pH值、离子强度对吸附的影响,并考察了吸附剂表面的Zeta电位变化。结果表明,几种吸附剂对阿特拉津的吸附均符合Freundlich方程;竹炭、木炭的吸附能力明显高于蒙脱石和凹凸棒石。吸附剂对阿特拉津的吸附量随着悬液离子强度的增加而增加,在悬液pH一定(pH=6),离子强度为10-3mol/L NaNO3时,蒙脱石、凹凸棒石对阿特拉津的吸附量分别为538.30、609.68 mg/kg,当离子强度增加为10-2mol/L时,吸附量分别增至611.26、731.63 mg/kg;当离子强度由10-3增至10-1mol/L NaNO3时,竹炭、木炭对阿特拉津的吸附量有较多增加。当悬液pH在3~8范围时,几种吸附剂表面均带负电荷,其Zeta电位值随着pH的增加而增加,随离子强度的增加而减小。悬液离子强度一定时,随着pH的增加,吸附阿特拉津后吸附剂表面Zeta电位变化不显著。研究结果有助于从机理上解析吸附剂对有机污染物的吸附行为。     

Equilibrium and Kinetic Studies on Biosorption of Heavy Metals by Leaf Powder of Paper Mulberry (Broussonetia papyrifera)

Paper mulberry (Broussonetia papyrifera) leaf powder was used to remove heavy metal ions from aqueous solutions. The specific uptakes of Cu (II), Pb (II), and Cd (II) by the leaf powder were 43.40?±?0.2, 43.9?±?0.5, and 30.65?±?0.9 mg g^?1, respectively, when 500 mg L^?1 of the metal solutions were used. The data fitted well to the Langmuir isotherm. The process followed the pseudo-second-order kinetic equation and intraparticle diffusion played an important role in the adsorption process. On the basis of the calculated thermodynamic parameters such as standard enthalpy (??H°), entropy (??S°) and free energy change (??G°), it was inferred that the sorption process was endothermic and spontaneous in nature. The surface properties of the leaf powder (revealed by scanning electron microscopic observations) were suitable for the metal adsorption process. Energy dispersive X-ray fluorescence analysis confirmed the sequestration of the metal ions by the leaf powder. Fourier transform infrared spectroscopy implicated that different functional groups on the leaf powder were involved in the metal adsorption process. The results obtained from this study implicated that the B. papyrifera leaf powder was a good choice as a metal adsorbent. This abundantly available natural and eco-friendly biosorbent could be effectively used to develop a technology in the future.     

褐煤基材料对Cd~(2+)的吸附机制

为筛选稳定、高效、环境友好的重金属污染修复材料,利用批吸附试验研究了不同温度下褐煤、腐植酸、活性炭对镉(Cd~(2+))的吸附特征,采用非线性χ~2检验辅助决定系数判断等温线模型拟合度,用红外光谱对材料功能团进行了识别。结果表明,Temkin模型能最好拟合3种材料对Cd~(2+)的等温吸附过程,Langmuir和Freundlich模型也能较好拟合但与温度有关。吸附热力学参数表明,3种材料对Cd~(2+)的吸附为优惠发生的物理吸附,并且是自发的吸热过程,3种材料与Cd~(2+)之间均有较强的作用力。在温度294.55~313.15 K时腐植酸、褐煤和活性炭对Cd~(2+)的最大吸附量分别为36.14~44.09、29.63~38.20 mg·g~(-1)和21.04~30.34 mg·g~(-1),吸附量随温度升高而升高,吸附自由能随着温度升高而降低,说明升温吸附更容易发生。准二级动力学拟合数据最好,表明3种材料对Cd~(2+)的吸附存在着化学过程。褐煤基活性炭和褐煤基腐植酸具有丰富的孔隙结构。红外光谱图表明腐植酸和褐煤较大的吸附量与其含氧功能团种类较多以及在波数2 360 cm~(-1)和2 342 cm~(-1)附近吸收峰有关。因此,褐煤基3种材料对Cd~(2+)的吸附是自发的吸热过程,腐植酸对Cd~(2+)的最大吸附量和吸附能力最大,用Temkin等温方程和准二级动力学曲线能最适宜描述褐煤基材料对Cd~(2+)的吸附特征。     

Equilibrium Isotherm Studies for the Sorption of Divalent Metal Ions onto Peat: Copper,Nickel and Lead Single Component Systems

The sorption of three divalent metal ions — copper, nickel and lead — from aqueous solution onto peat in single component systems has been studied and the equilibrium isotherms determined. The experimental data have been analysed using the Langmuir, Freundlich, Redlich-Peterson, Toth, Temkin, Dubinin-Radushkevich and Sips isotherm models. In order to determine the best fit isotherm for each system, six error analysis methods were used to evaluate the data: the coefficient of determination, the sum of the errors squared, a hybrid error function, Marquardt's percent standard deviation, the average relative error and the sum of absolute errors. The error values demonstrated that the Sips equation provided the best model for the three sets of experimental data overall.     

Assessing Molybdenum Adsorption onto an Industrial Soil and Iron Minerals

Spatial accuracy of hydrologic modeling inputs influences the output from hydrologic models. A pertinent question is to know the optimal level of soil sampling or how many soil samples are needed for model input, in order to improve model predictions. In this study, measured soil properties were clustered into five different configurations as inputs to the Soil and Water Assessment Tool (SWAT) simulation of the Castor River watershed (11-km² area) in southern Quebec, Canada. SWAT is a process-based model that predicts the impacts of climate and land use management on water yield, sediment, and nutrient fluxes. SWAT requires geographical information system inputs such as the digital elevation model as well as soil and land use maps. Mean values of soil properties are used in soil polygons (soil series); thus, the spatial variability of these properties is neglected. The primary objective of this study was to quantify the impacts of spatial variability of soil properties on the prediction of runoff, sediment, and total phosphorus using SWAT. The spatial clustering of the measured soil properties was undertaken using the regionalized with dynamically constrained agglomerative clustering and partitioning method. Measured soil data were clustered into 5, 10, 15, 20, and 24 heterogeneous regions. Soil data from the Castor watershed which have been used in previous studies was also set up and termed “Reference”. Overall, there was no significant difference in runoff simulation across the five configurations including the reference. This may be attributable to SWAT's use of the soil conservation service curve number method in flow simulation. Therefore having high spatial resolution inputs for soil data may not necessarily improve predictions when they are used in hydrologic modeling.