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11.
The adsorption of some heavy metals onto the walls of harvested, washed, and dried non-living biomass cells of different Pseudomonas strains was studied at optimum experimental conditions using a simplified single component system. The Langmuir adsorption model was found to be a suitable approach to describe the system via multi-step processes. Isotherms measured at 30.0°C and pH 5.5 with [M]total?=?10–100 mM for tight, reversible Cr6+(aq), Ni2+(aq), Cu2+(aq) and Cd2+(aq) binding by the cell walls of the investigated biomass fit the Langmuir model and give the pH-independent stoichiometric site capacities ν i and equilibrium constants K i for metal binding at specific biomass sites i?=?A, B, C, and D. Tight binding sites A, B, and D of the non-living biomass are occupied by CrVI, sites A and C by NiII, sites A and D by CdII, and only site B by CuII. It is concluded that ν i is a stoichiometric parameter that is independent of the magnitude of K i for binding site i and that the studied heavy metals selectively and tightly bind at different biomass sites. 相似文献
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Mesoporous carbon adsorbents, having high nitrogen content, were synthesized via nanocasting technique with melamine–formaldehyde resin as precursor and mesoporous silica as template. A series of adsorbents were prepared by varying the carbonization temperature from 400 to 700°C. Adsorbents were characterized thoroughly by nitrogen sorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), elemental (CHN) analysis, Fourier transform infrared (FTIR) spectroscopy and Boehm titration. Carbonization temperature controlled the properties of the synthesized adsorbents ranging from surface area to their nitrogen content, which play major role in their application as adsorbents for CO2 capture. The nanostructure of these materials was confirmed by XRD and TEM. Their nitrogen content decreased with an increase in carbonization temperature while other properties like surface area, pore volume, thermal stability and surface basicity increased with the carbonization temperature. These materials were evaluated for CO2 adsorption by fixed-bed column adsorption experiments. Adsorbent synthesized at 700°C was found to have the highest surface area and surface basicity along with maximum CO2 adsorption capacity among the synthesized adsorbents. Breakthrough time and CO2 equilibrium adsorption capacity were investigated from the breakthrough curves and were found to decrease with increase in adsorption temperature. Adsorption process for carbon adsorbent–CO2 system was found to be reversible with stable adsorption capacity over four consecutive adsorption–desorption cycles. From three isotherm models used to analyze the equilibrium data, Temkin isotherm model presented a nearly perfect fit implying the heterogeneous adsorbent surface. 相似文献
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Sangchul Nam Wan Namkoong Jeong-Hee Kang Jin-Kyu Park Namhoon Lee 《Waste management (New York, N.Y.)》2013,33(10):2091-2098
Due to the increase in energy cost by constantly high oil prices and the obligation to reduce greenhouse effect gases, landfill gas is frequently used as an alternative energy source for producing heat and electricity. Most of landfill gas utility facilities, however, are experiencing problems controlling siloxanes from landfill gas as their catalytic oxidizers are becoming fouled by silicon dioxide dust. To evaluate adsorption characteristics of siloxanes, an adsorption equilibrium test was conducted and parameters in the Freundlich and Langmuir isotherms were analyzed. Coconut activated carbon (CA1), coal activated carbon (CA2), impregnated activated carbon (CA3), silicagel (NCA1), and activated alumina (NCA2) were used for the adsorption of the mixed siloxane which contained hexamethyldisiloxane (L2), octamethylcyclotetrasiloxane (D4), and decamethylcyclopentasiloxane (D5). L2 had higher removal efficiency in noncarbon adsorbents compared to carbon adsorbents. The application of Langmuir and Freundlich adsorption isotherm demonstrated that coconut based CA1 and CA3 provided higher adsorption capacity on L2. And CA2 and NCA1 provided higher adsorption capacity on D4 and D5. Based on the experimental results, L2, D4, and D5 were converted by adsorption and desorption in noncarbon adsorbents. Adsorption affinity of siloxane is considered to be affect by the pore size distribution of the adsorbents and by the molecular size of each siloxane. 相似文献
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The use of a new biosorbent derived from Abelmoschus esculentus (A. esculentus) seed for the removal of Acid Blue 113 (AB113) in aqueous solutions was investigated in batch mode. Biosorption studies were carried out under varying operational parameters including initial pH, biosorbent dosage, contact time, initial dye concentration and temperature. The results indicated that the biosorption properties were strongly dependent on initial pH. Fourier transform infrared spectroscopy analysis revealed that hydroxyl, carboxylic and amide functional groups present on the biosorbent surface were involved in the dye removal process. Equilibrium data were best fitted by the Langmuir model. The maximum biosorption capacity was 169.9 ± 3.1 mg g−1 at 25 °C and initial pH 5.5. The kinetic data were in good agreement with the pseudo-second-order kinetic model. The process was controlled by diffusion through boundary layer at the initial stage followed by intra-particle diffusion at the later stage. Thermodynamic evaluation showed that the process was endothermic and spontaneous. The present study suggests that A. esculentus seed with maximum biosorption capacity which compared well with values reported in the literature can be a potential biosorbent for AB113 dye removal. 相似文献
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Chen Zhou Ermias Gebrekrstos Tesfamariam Youneng Tang Ang Li 《Frontiers of Environmental Science & Engineering》2023,17(9):107
17.
S. S. Baral S. N. Das P. Rath G. Roy Chaudhury Y. V. Swamy 《Chemistry and Ecology》2007,23(2):105-117
Biosorption studies of Cr(VI) were carried out using waste weed, Salvinia cucullata. Various adsorption parameters were studied, such as agitation speed, contact time, pH, particle size, and concentrations of adsorbent and adsorbate. The equilibrium was achieved in 12 h. A lower pH favoured adsorption of Cr(VI). The kinetics followed pseudo-second-order rate equations. The adsorption isotherm obeyed both the Langmuir and Freundlich models. The calculated activation energy (1.1 kJ mol-1) suggested that the adsorption followed a diffusion-controlled mechanism. Various thermodynamic parameters such as Δ G°, Δ H°, and Δ S° were also calculated. The positive values of enthalpy indicated the endothermic nature of the reaction, and Δ S° showed the increasing randomness at the solid liquid interface of Cr(VI) on the adsorbent, which revealed the ease of adsorption reaction. These thermo-dynamic parameters showed the spontaneity of the reaction. The maximum adsorption of uptake (232 mg g-1) compared well with reported values of similar adsorbents. The rate-determining step was observed to follow an intra-particle diffusion model. 相似文献
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利用天然膨润土、羟基铁和羟基铁铝柱撑膨润土进行了吸附有机锡废水中总锡的实验.研究了膨润土投加量、pH、吸附时间和吸附等温线的变化规律.结果表明,达到吸附平衡的时间为1 h;总锡的吸附去除率最佳吸附pH在6.0~9.0;膨润土的投加量大于10 g/L时,总锡吸附去除率可达到最大值;总锡在天然膨润土上的吸附符合Freundlich吸附等温方程,而总锡在柱撑膨润土上的吸附同时符合Freundlich和Langmuir吸附等温方程;柱撑膨润土吸附活性位的数量是决定吸附性能的关键因素.在对总锡的吸附过程中,膨润土吸附容量的大小和吸附作用强弱的顺序为:羟基铁铝柱撑膨润土>羟基铁柱撑膨润土>天然膨润土. 相似文献
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有机改性膨润土吸附锌离子的性能 总被引:1,自引:0,他引:1
研究了有机改性膨润土对锌离子的吸附性能。结果表明:有机改性膨润土对水中锌离子的吸附在60 min达到平衡;在50 mL1、0 mg/L的锌离子溶液中,当其用量为1.0 g时,有机改性膨润土对水中锌离子的吸附去除率达到92.8%;温度对水溶液中锌离子的去除有一定的影响,有机改性膨润土吸附水中锌离子的过程为放热反应。平衡吸附量与平衡质量浓度之间的关系符合Freundlich和Langmuir等温吸附方程所描述的规律。 相似文献
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Shenghui Guo Wei Li Libo Zhang Jinhui Peng Hongying Xia Shiming Zhang 《Process Safety and Environmental Protection》2009,87(5):343-351
Adsorption of Pb(II) ions from aqueous solution onto a low cost adsorbent—the Eupatorium adenophorum spreng has been investigated to evaluate the effects of initial lead ion concentration, contact time, pH and temperature on the removal of Pb(II) systematically. The optimal pH value for Pb(II) adsorption onto the E. adenophorum spreng was found to be 5.0. Thermodynamic parameters such as standard Gibbs free energy (ΔG°), standard enthalpy (ΔH°), and standard entropy (ΔS°) were evaluated by applying the van’t Hoff equation, which describes the dependence of equilibrium constant on temperature. The thermodynamics of Pb(II) adsorption onto the E. adenophorum spreng indicated that the adsorption was spontaneous and endothermic. Langmuir and Freundlich isotherms were used to analyze the equilibrium data at different temperatures and the equilibrium data were found to fit Freundlich isotherm equation better than Langmuir isotherm. The adsorption was analyzed using pseudo-second-order kinetic models. 相似文献