Sorption of Triton X-100 on soil organic matter fractions:Kinetics and isotherms

Kinetics and isotherms of Triton X-100 sorption on soil,base-extracted soil（BE）,humic acid（HA） and humin（HM） were investigated respectively to get better understanding on characteristics of the surfactant sorption onto different soil organic matters（SOMs）.It was demonstrated that the kinetics results could be satisfactorily described by the pseudo-second order model.The half of the time to reach equilibrium（t1/2） for different sorbents followed the sequence of soil 〉 HA 〉 BE 〉 HM.Furthermore,the calculated equilibrium sorption capacity（Ceq） was found in the sequence of HA 〉 BE 〉 HM 〉 soil,which agreed well with the experimental results.The isotherms of Triton X-100 sorption on soil and HA could be well described by the S-type isotherm,but BE and HM by the L-type.The isotherms of all the four sorbents were found reasonably fitted to the Langmuir equation.The Kd value,defined as the ratio of Triton X-100 in sorbent and in the equilibrium solution for given concentrations,generally followed the order of HM 〉 HA 〉 soil 〉 BE.Separated HM and HA showed high affnity for Triton X-100,but the HA and HM in soil and BE were tightly bounded by the minerals.Thus,the HA on the soil surface might dominate the sorption,whereas the bounded HM would play a key role upon the surfactants being penetrated inside the soil.

Equilibrium Sorption of Lead and Nickel from Solutions by Flame of the Forest (<i>Delonix regia</i>) Pods: Kinetics and Isothermic Study

Batch adsorption techniques were used to study the biosorption of Lead and Nickel from aqueous solutions by Flame of the forest pods. The effects of optimum pH, contact time, metal ion concentration, biosorbent dose, biosorbent particle size and the presence of sodium, calcium and magnesium interfering ions on the sorption were investigated. Experimental results showed that Delonix regia biomass was effective in removing these metals from aqueous solutions as the equilibrium biosorption of both metals was attained within 60 minutes of interaction with 98% of the metals removed within this period. Sorption of these metals was dependent on pH as maximum removal was attained at pH 4 and pH 5 for Lead and Nickel ions respectively. Adsorption experiments showed that the process followed the pseudo second order kinetic model with high r2 (0.9999) and the equilibrium data fitted well with Langmuir and Freundlich isotherm models. The presence of competing ions impacted negatively on the sorption process irrespective of the type used. 27% and 36% of lead (II) were recovered from the spent biosorbents with 1 MHCl and disodium salt of EDTA solutions respectively.

龙眼果粉的水分吸附特性研究

以龙眼果粉为对象,利用静态测量法测定其在不同温度下的吸湿等温线,探究在不同含水率下龙眼果粉的X射线衍射图谱及玻璃化转变温度,并通过数学方程计算其热力学特性参数,以揭示龙眼果粉的水分吸附特性。结果表明,龙眼果粉的吸湿等温线为Ⅲ型等温线,Peleg模型是龙眼果粉吸湿等温线的最佳拟合模型。在水分活度(water activity,A_(w))>0.69时,龙眼果粉水分吸附量显著增加,导致糖类晶体结构消失。龙眼果粉的吸附过程符合熵焓互补理论,其吉布斯自由能为1586.6 J/mol>0,表明可通过控制环境条件来控制龙眼果粉的吸附过程。干基含水率从0.054 g/g上升到0.350 g/g时,龙眼果粉的玻璃化转变温度起始点从14.6℃降低至-26.5℃,其终点从39.1℃下降至-5.8℃。25℃下龙眼果粉的理论最佳贮藏A_(w)为0.086,对应的干基含水率为0.0495 g/g。该研究结果可为龙眼果粉贮藏条件的选择提供参考。

以Hailwood-Horrobin平衡水分模型分析聚葡萄糖吸潮机理

为解释聚葡萄糖的吸潮性能,改进包装材料,在20~35℃和平衡相对湿度(ERH)10%~90%范围内,测定了初始含水率(IMC)1.01%~4.89%的5个国产样品(a1~a5)的水分吸附与解吸等温线。吸附和解吸等温线均是S型曲线,在ERH小于80%时,解吸等温线与吸附等温线之间存在滞后现象,样品初始含水率越低,滞后现象越显著。由于聚葡萄糖是无定形相态的粉末,我们假定聚葡萄糖水分吸附过程是蒸汽相态、液体相态(多分子层吸附)及固体溶液(单分子层吸附)之间存在的平衡,按照Hailwood-Horrobin(HH)模型把S型吸附等温线去卷积为单分子层(Mh)和多分子层成分(Md),吸附和解吸多分子层水含量随ERH增加呈现S型曲线增加,解吸单分子层含水率随ERH增加保持不变,而吸附单分子层含水率随ERH增加对a1~a4样品(IMC4.87%~2.35%)缓慢增加,对a5样品(IMC 1.01%)几乎线性减少。随着样品初始含水率降低,吸附位点聚合物分子量对a1样品最大,对a5样品最小。尽管红外光谱扫描显示a5样品羟基(3416cm^(–1))和无定形结构官能团(1027cm^(–1))的强度最小,但是a5样品的吸潮率最大。说明不同工艺加工的聚葡萄糖样品含水率越低,吸附单分子层水含量随ERH增加几乎线性减少,但是吸附多分子层含水量随ERH增加是S型增加,吸潮率和吸湿量增大。

Equilibrium and kinetics of copper(Ⅱ) biosorption by Myriophyllum spicatum L.

The potential use of Myriophyllum spicatum L. biomass as a biosorbent for the removal of copper（ Ⅱ ） from aqueous solution was investigated in laboratory condition. The sorption experiments were undertaken to obtain copper（ Ⅱ ） biosorption properties of M. spicatum L., i.e. equilibrium time, the maximum capacity, and rate constants. Copper（ Ⅱ ） biosorption was fast and equilibrium was attained within 35 min at initial copper（ Ⅱ ） concentration of 6 mg/L. Different isotherm models including the Langmuir, Freundlich, Temkin and Redlich-Peterson model, were used to investigate the sorption capacity and isotherm. These models showed an excellent match with the experimental data except for the Freundlich model. According to the Langmuir coefficients, the maximum sorption capacity of copper onto M. spicatum L. was 10.80 mg/g. The kinetics of copper（ Ⅱ ） sorption was also analysed and rate constants were derived. It was found that the overall sorption process was best described by the pseudo second-order equation, and that intraparticle diffusion was not the rate determining step. The results of this study showed that M. spicatum L. can be considered as useful vehicles for the removal and recovery of copper（ Ⅱ ） from aqueous solutions.

Effect of Initial Concentration on Adsorption-Desorption Characteristics and Desorption Hysteresis of Hexachlorobenzene in Soils

Adsorption and desorption are important processes that influence the transport, transformation, and bioavailability of hexachlorobenzene (HCB) in soils. To examine the adsorption-desorption characteristics of HCB, equilibrium batch experiments were carried out using two soils (red soil and paddy soil) with different initial HCB concentrations (0.25, 0.50, 0.75, 1.00, 1.50, 2.50, 3.50, and 5.00 mg L-1 ) by using 0.01 mol L-1 calcium chloride as the background solution. The successive desorption experiments (48, 96, 144, 192, and 240 h) were conducted after each adsorption equilibrium experiment. The results revealed that adsorption and desorption isotherms of HCB on two soils were nonlinear, which can be best described by the Freundlich equation with the square of the correlation coefficient (r 2 ) ranging from 0.97 to 0.99. Desorption of HCB from the two soils exhibited hysteresis at all HCB concentrations because the Freundlich desorption coefficients were always higher than the Freundlich adsorption coefficients. The hysteretic effect was enhanced with increasing initial HCB concentration, and positive hysteresis was observed at different concentrations.

Strontium Adsorption from Sulfuric Acid Solution by Dowex 50W-X Resins

在这研究，从由不同 Dowex 50W-X 离子交换树脂的硫磺的酸答案的锶吸附被调查。在这些树脂之中， Dowex 50W-X8 树脂从水的答案显示出锶的最大的吸着。pH，接触时间，树脂的团，温度，和锶吸附上的介入的离子的集中的效果被评估决定锶吸着过程的最佳条件。吸着的运动模型用伪 first 和伪秒顺序模型被分析。结果显示伪秒命令运动模型比另一个更适当。而且，在这研究获得的数据被适合进几个吸着等温线模型，兰米尔吸着等温线显示出最好的试穿到试验性的数据，这被发现。

Molecular simulation studies of hydrocarbon and carbon dioxide adsorption on coal

Sorption isotherms of hydrocarbon and carbon dioxide （CO2） provide crucial information for designing processes to sequester CO2 and recover natural gas from unmineable coal beds. Methane （CH4）, ethane （C2H6）, and CO2 adsorption isotherms on dry coal and the temperature effect on their maximum sorption capacity have been studied by performing combined Monte Carlo （MC） and molecular dynamics （MD） simulations at temperatures of 308 and 370 K （35 and 97 ~C） and at pressures up to 10 MPa. Simulation results demonstrate that absolute sorption （expressed as a mass basis） divided by bulk gas density has negligible temperature effect on CH4, C2H6, and CO2 sorption on dry coal when pressure is over 6 MPa. CO2 is more closely packed due to stronger interaction with coal and the stronger interaction between CO2 mole- cules compared, respectively, with the interactions between hydrocarbons and coal and between hydrocarbons. The results of this work suggest that the ＂a＂ constant （pro- portional to TcPc） in the Peng-Robinson equation of state is an important factor affecting the sorption behavior of hydrocarbons. CO2 injection pressures of lower than 8 MPa may be desirable for CH4 recovery and CO2 sequestration. This study provides a quantitative under- standing of the effects of temperature on coal sorptioncapacity for CH4, C2H6, and CO2 from a microscopic perspective.

Batch studies of adsorption of copper and lead on activated carbon from Eucalyptus camaldulensis Dehn. bark

Powdered activated carbon (PAC) prepared from Eucalyptus camaldulensis Dehn. bark was tested for its adsorption capacity for Cu(Ⅱ) and Pb(Ⅱ). The experiment was conducted to investigate the effects of pH, contact time, initial metal concentration, and temperature. The best adsorption of both Cu(Ⅱ) and Pb(Ⅱ) occurred at pH 5, where the adsorption reached equilibrium within 45 min for the whole range of initial heavy metal concentrations (0.1-10 mmol/L). The adsorption kinetics was found to follow the pseudo-...

Sorption equilibrium moisture and isosteric heat of Chinese wheat bran products added to rice to increase its dietary fibre content

More and more people concern about supplementing dietary food with wheat bran to increase fibre content,but there has been little study of the sorption isotherms and isosteric heats of wheat bran fibre products,which are important to the quality and storage durability of such commodities.This study collected equilibrium moisture content(EMC)and equilibrium relative humidity(ERH)data on six Chinese wheat bran products via the static gravimetric method and analysed their sorption isosteric heats.Results showed that all six wheat bran products had sigmoidal isotherms.The data were best fitted by polynomial,modified GAB,modified Oswin,and modified Halsey models.The relative safe moisture contents of the six wheat bran products were 12.20%–13.86%wet basis(w.b.).The heat of vaporization of wheat bran products approached the latent heat of pure water at around a moisture content(MC)of 22.5%and approximately 2450 kJ/kg.A process of extrusion and ultrafine grinding reduced the solid surface area and sorption isosteric heats of the monolayer,multilayer and condensed water regions in the wheat bran products.In the temperature range of 10–37℃,the EMC of sorption in monolayer,multilayer and condensed water regions decreased with increasing temperature.The milled rice to which 1%–3%200-mesh wheat bran product was added maintained its texture when made into cooked rice and its thermomechanical properties when made into rice dough.After processing by extrusion and ultrafine grinding,wheat bran products have a lower solid surface area and lower monolayer water content(Mm)and sorption isosteric heat values.Some 3%200-mesh wheat bran product can be added to cooked rice for increasing its fibre content and making it more nutritious.

Adsorption Characterization of Strontium on PAN/Zeolite Composite Adsorbent

This work reports the adsorption of strontium from aqueous solutions onto PAN/zeolite composite. The strontium adsorption on the composite adsorbent was studied as a function of initial strontium concentration, pH of the solution, contact time and temperature. Adsorption isotherms like Langmuir, Freundlich,Dubinin–Radushkevich (D–R) and Temkin were used to analyze the equilibrium data at the different concentrations.Adsorption process well fitted to Temkin isotherm model. Thermodynamic parameters such as the changes in enthalpy, entropy and Gibbs’ free energy were determined, showing adsorption to be an exothermic and spontaneous process.

Analogy between adsorption and sorption： An elementary mechanistic approach. I. Monolayer adsorption and sorption without solvent cluster formation

The elementary mechanistic model of adsorption and sorption is based on a simple hypothesis: the adsorption sites are uniformly distributed on the surface of the pore walls in the adsorbent, the sorption sites are uniformly distributed in the volume of the polymer. In this first paper we will analyze the simple case where one solute molecule is only allowed to occupy a single adsorption or sorption site. A common elementary occupation law of the free sites is assumed: the differential increase of the number of the adsorbed/sorbed molecules is proportional to the differential increase of the activity of the solute and the concentration of the free (non-occupied) sites in the solid. The proportionality coefficient is called affinity coefficient depending on the solid/solute couple and on the temperature and independent of the concentration of the solute. In adsorption the concentration of the free sites is a surface concentration on the pore walls and in sorption it is expressed by the molarity. The simple mono- layer adsorption law of Jovanovi? is obtained: n = n_0(1-e^(-KP)) where n is the number of moles adsorbed when the pressure is P. n0is the total number of adsorption sites and K the affinity coefficient for adsorption. The sorption law writes: a=1/k[?/(1-?)] +(1-r)/kln[1+1/r?/(1-?)] where ?, r and k hold respectively for the volume fraction of the solvent in the polymer, for the ratio of the molar volumes of the solvent to the elementary polymer chain containing one single adsorption site and for the sorption affinity coefficient. The confrontation of these equations to experimental isotherms is satisfactory in comparison with the classical Langmuir and Flory–Huggins equations: the best results are obtained for adsorption of vapors on a 5A zeolite and for all analyzed sorption results.

Sorption behavior of o-nitrophenol on marine sediment

Systematic study on sorption behavior of o-nitrophenol on marine sediments was conducted. Isotherms of sorption of o-nitrophenol on marine sediments could be described by Freundlich model; and the isotherm of sorption of o-nitrophenol on HCl-treated sediment could be described by Langmuir model. The sorption behavior was affected by various factors including organic carbon content, aqueous solution salinity, temperature, and acidity. The sorption amount of o-nitrophenol increased when salinity and acidity of the aqueous solution increase, but decreased with increasing temperature. Organic carbon content in sediments had apparent effect on the behavior except for HCl-treated sediments.

Sorption and desorption behavior of lead in four different soils of India

Sorption and desorption mechanisms of lead (Pb) were determined in four different soils collected from different agro-climatic regions of India. The soils were classified as: fine loamy mixed Typic- Dystrudepts, fine sandy loam Typic Ustochrepts, fine loamy Typic Ustochrept, and fine sandy loam Udic Haplustalfs. Seven different Pb solutions [Pb(NO3)2 dissolved in 0.01M Ca(NO3)2] in a range of 400 to 2000μgL-1 were applied to study the sorption amounts at 25(±2)oC and 45(±2)oC temperatures. With the increase in application rate and tempera-ture, sorption amounts of Pb increased;however, percentages of sorption of applied Pb were decreased. Sorptions were positively and significantly (p≤0.01) correlated with Langmuir adsorption isotherm. Thermodynamic parameters of sorption (i.e. Ko, ?Go, ?Ho, and ?So) were also determined at two tempera-tures, 25(±2)oC and 45(±2)oC. Increase in Ko with the increase in temperature indicated positive effect of temperature on Pb sorption. High absolute values of ?Go, and positive values of ?Ho, and ?So suggested that the sorption reaction was spontaneous and en-dothermic. Sorbed Pb were desorbed in Pb free 0.01M Ca(NO3)2 solutions at 25(±2)oC and 45(±2)oC. Desorption amounts increased with increase in the Pb application rate, but not always with the increase in temperature.

Short-Range-Order Minerals and Dominant Accessory Properties Controlling P Sorption in Tropical Tephra Soils of the Cameroon Volcanic Line

Knowledge on soil properties likely to influence P sorption in tephra soils is very important for sustainable management of available P. Sorption studies on six tephra soils were conducted to relate P sorption to soil characteristics in order to identify those with potential influence on P sorption. Four equilibrium-based sorption models commonly encountered in soil studies (Langmuir, Freundlich, Temkin, and Van Huay) were used to describe P sorption in the soils. P sorption was determined by measuring the residual P content of a clarified equilibrating solution of 0.02 N KCl containing varying concentrations (0, 5, 10, 15, 30, 40, 50, 60, 80, and 100 mg/L) of P as KH2PO4 after mixing with 1 g of soil in duplicates for 16 hours at 25&deg;C. Maximum amount of P sorbed for the varying P concentrations used ranged from 2080 to 5402 mg/kg with a potential for greater P sorption maxima at higher P solution concentrations. P sorption in these soils was best described by the Langmuir and Freundlich models. Allophane and ferrihydrite are the principal species controlling the high P sorption in these soils. pH-NaF proved to be a potentially reliable test for assessing the presence of allophanic materials and thus for estimating P sorbed. This work would guide both effective and efficient P fertilizer management with economic implications for both the study area and similar environments.

Sorption of Denatonium to Kaolinite Clay from Water

Denatonium benzoate is an aversive agent proposed for use in certain anti-freeze formulations to reduce poisoning events of pets and humans. Unfortunately, the sorption properties of denatonium cations to soil and/or soil components have not been investigated. In this paper, denatonium sorption to reference kaolinite clay under varied pH, ionic strength, and cation identity is described. The data clearly indicate that the nature of the background electrolyte cation modulates denatonium sorption with enhanced sorption occurring the presence of potassium ions versus minimal sorption occurring in a calcium chloride electrolyte at each pH studied as estimated using Dubinin-Raduskevich (D-R) isotherms. The effect of background electrolyte concentration on sorption was consistent with an ion-exchange process wherein the sorption capacity increased with decreased background electrolyte concentration. An interesting and unexpected observation of increased sorption capacity (estimated using the D-R model) with decreasing pH was observed in 10 mM CaCl2 in contrast to an observed and expected increase in denatonium sorption to kaolinite in the presence of either of 10 mM NaCl or 10 mM KCl. Estimates of the mean sorption energy using D-R isotherms ranging from 2.65 kJ/mol in 10 mM CaCl2 at pH 4 to 4.68 kJ/mol at pH 10 suggesting that the sorption process is not exclusively ion-exchange.

Modeling of Adsorption of Bi(III) from Nitrate Medium by Impregnated Resin D2EHPA/XAD-1180

Di(2-ethylhexyl)phosphoric acid (D2EHPA) in acetone was supported on the Amberlite XAD-1180 polystyrene divinylbenzene copolymer resin. The use of XAD-1180 impregnated with D2EHPA for the extraction of bismuth(III) from nitrate medium was carried out using batch technique. Various parameters affecting the uptake of this metal ion were described in the previous paper (Belkhouche and Didi, 2010) and the capacity of the impregnated resin for bismuth(III) was found to be 490.7 mg/g of resin. Effect of temperature on the values of distribution equilibrium was studied to evaluate the changes in standard thermodynamic quantities. A comparison of Langmuir forms I, II and Freundlich sorption isotherms was realized and the kinetic models applied to the adsorption rate data were evaluated for Lagergren first order, the pseudo second order and Morris–Weber models. From the results, the adsorption of Bi(III) onto D2EHPA/XAD-1180 resin shown the exothermic character and followed the Langmuir form II isotherm. Thus, the capacity of monolayer adsorption of Bi(III) was equal to 769.23 mg/g of resin. Both the Lagergren pseudo first order and film-diffusion models were found to best describe the experimental rate data.

Sorption of Gadolinium (III) Ions by a Natural Clinoptilolite-Containing Tuff

The equilibrium and kinetics of sorption of gadolinium (III) ions from sulfate solutions by a natural clinoptilolite containing tuff are studied. It is shown that gadolinium is completely extracted from dilute solutions (0.002 M). The kinetic parameters of the sorption process are determined.