离子交换纤维吸附Cr（VI）的热力学研究

采用离子交换纤维对Cr（VI）的吸附性能进行了研究,在温度298～318K和研究的浓度范围内,离子交换纤维对Cr（vi）的吸附平衡数据符合Freundlich吸附等温方程。Freundlich等量吸附焓表明,离子交换纤维对Cr（VI）的吸附是吸热过程,并对吸附焓、自由能、吸附熵进行了计算,并对吸附行为进行了合理解释。     

离子交换纤维吸附偏二甲肼的热力学研究

对自制强酸性离子交换纤维吸附偏二甲肼的特性进行了研究,在温度为287~318 K和40~190 mg.L-1的浓度范围内,离子交换纤维对偏二甲肼的吸附符合Langmuir和Freundlich等温吸附方程。不同温度下等温吸附曲线的测定和等量吸附焓的计算表明:离子交换纤维对偏二甲肼的吸附是吸热过程。对偏二甲肼在离子交换纤维上的吸附焓、吉布斯自由能、吸附熵的计算表明,该离子交换纤维对偏二甲肼的吸附没有化学键生成,并对吸附行为作了合理的解释。     

离子交换纤维对低浓度二甲胺水溶液吸附性能研究

对离子交换纤维(IEF)吸附二甲胺(DMA)的特性进行了研究。等温吸附线研究表明,离子交换纤维对二甲胺的吸附符合Freundlich和Langmuir等温吸附方程。热力学研究表明,Freundlich模型可以很好地模拟二甲胺在离子交换纤维上的交换行为,交换反应的ΔG0,ΔH0,ΔS0,交换过程为自发的吸热过程。动力学研究表明,离子交换纤维对二甲胺的吸附以液膜扩散为主,其交换行为可采用Boyd液膜扩散方程描述。     

离子交换纤维对偏二甲肼的吸附性能

以火箭推进剂主要成分偏二甲肼为研究对象,通过配制模拟水样,采用强酸阳离子交换纤维对其中的偏二甲肼进行吸附,研究了偏二甲肼在离子交换纤维上的等温吸附线、吸附动力学和动态吸附,并将其动态吸附效果与732强酸阳离子交换树脂进行了对比. 结果表明,强酸阳离子交换纤维对偏二甲肼的吸附以液膜扩散为主,符合Boyd液膜扩散方程. 在291 K和研究的浓度范围内,离子交换纤维对偏二甲肼的吸附符合Freundlich等温吸附方程. 动态吸附结果表明,离子交换纤维对偏二甲肼的交换吸附速率大于离子交换树脂. 离子交换纤维柱的利用率高,相同条件下的处理量是树脂的3.86倍.     

纤维对苯酚的吸附性能研究

研究了自制的纤维对苯酚的吸附热力学特性,测定了不同温度下的吸附等温线,结果显示,纤维对水溶液中的苯酚有较高的吸附能力,吸附过程符合Langmuir和Freundlich方程,吸附焓变为正值,表现为吸热的吸附过程。     

儿茶素在离子交换纤维上的扩散机理研究

研究了静态下儿茶素在自制的聚丙烯基阴离子交换纤维上的扩散机理。结果表明，离子交换纤维对儿茶素的吸附主要以扩散而不是以交换为主控步骤．在反应的初期．以液膜扩散为主，反应3min后．以孔隙扩散控制为主。     

亚甲基蓝在污泥微波热解半焦上的吸附

采用活性污泥微波热解残余半焦作为吸附剂,研究了其对水中亚甲基蓝吸附的动力学、等温线及其热力学行为.结果表明,亚甲基蓝在污泥半焦表面的吸附符合准2级动力学模型,吸附速率常数随着初始质量浓度升高而降低,随着吸附温度的升高增长.分别用Langmuir和Freundlich等温方程对数据进行拟合,等温吸附过程能较好地用Freundlich吸附等温线描述,表明亚甲基蓝在污泥半焦表面的吸附受多种机制影响.不同温度下的吸附热力学的吉布斯自由能以及熵变和焓变显示该吸附过程为吸热反应.     

羧酸型离子交换纤维对卡那霉素的吸附

测定了羧酸型离子交换纤维吸附卡那霉素的动力学曲线和吸附等温线,并研究了温度、pH值、盐浓度对吸附卡那霉素的影响. 研究结果表明,羧酸型离子交换纤维吸附卡那霉素在10 min达到平衡,其吸附平衡行为可用Langmuir方程描述;在pH 7时,羧酸型离子交换纤维吸附卡那霉素的静态交换容量为最大,可达5.6′104 U/g;羧酸型离子交换纤维吸附卡那霉素随温度变化很小;NaCl的存在使羧酸型离子交换纤维对卡那霉素的交换容量减小;对发酵液中卡那霉素的动态交换容量为5.16′104 U/g,洗脱率为88.1%.     

多配位基螯合纤维对Ag~+的吸附性能研究

以聚(N-乙烯基甲酰胺/丙烯腈)纤维为原料,依次与二乙烯三胺交联反应、盐酸羟胺水溶液偕胺肟化反应和氢氧化钾水溶液水解反应,制备了多配位螯合纤维,研究了纤维对Ag+的吸附性能。用红外光谱法探讨了纤维对Ag+的吸附机理。结果表明:多配位鳌合纤维具有较好的吸附动力学特性,吸附速率常数和表观吸附活化能分别为3.337×10-4s-1和3.99kJ/mol;等温吸附曲线服从Langmuir和Freundlich经验式;测得吸附热力学参数焓变、熵变、自由能变分别为0.25kJ/mol,18.39J/mol.K,-5.24kJ/mol。     

海藻酸钙-亚铁氰化钴的制备及其对锶的吸附

采用水热合成法制备了无机离子交换剂亚铁氰化钴,针对该种离子交换剂粒径小,难装柱的缺点,制备出直径约1-2mm的球形复合离子交换剂(海藻酸钙-亚铁氰化钴),研究了复合离子交换剂对锶的吸附性能。研究结果显示:在25℃下,复合离子交换剂对锶离子进行静态吸附,当初始锶浓度为10mmol/L、复合离子交换剂中亚铁氰化钴加入量为3g/L、吸附4h时,吸附剂的对锶的吸附率为1.8mmol/g;通过对复合离子交换剂的吸附动力学和热力学研究,表明其对锶离子的吸附较好的符合动力学二级反应模型,以及Langmuir、Freundlich吸附等温吸附模型。     

Thermodynamics aspect of tannin sorption on polymeric adsorbents

Hypercrosslinked polydivinylbenzene and gel type poly(styrene-co-divinylbenzene) post-crosslinked with isocyanuric acid and macroporous crosslinked poly (N-vinyl acetamide) adsorbent were prepared for adsorbing tannin from aqueous. The sorption isotherms were measured and the isosteric enthalpy was quantitatively correlated with the fractional loading for the tannin sorption onto the three polymeric adsorbents. Surface energetic heterogeneity was observed for the three adsorbents and described with the functions of isosteric enthalpy. The causative factors of the surface heterogeneity of the adsorbents and the mechanism of tannin sorption onto the adsorbents from aqueous were discussed. It was suggested that multiply hydrogen bonding, π-π interaction and hydrophobic interaction were involved in tannin adsorption onto the polymeric adsorbents.     

Adsorption studies on the treatment of textile dyeing effluent by activated carbon prepared from olive stone by ZnCl2 activation

This study aimed to investigate the removal of a reactive dye from aqueous solution by adsorption. Activated carbon prepared from olive stone, an agricultural solid by-product, was used as adsorbent. Different amounts of activating agent (ZnCl₂) and adsorbent particle size were studied to optimise adsorbent surface area. The adsorption experiments were conducted at different process parameters such as adsorbent dose, temperature, equilibrium time and pH. The experimental results showed that at equilibrium time 120 min, optimum pH ranged between 3 and 4, and adsorbent dosage was 2.0 g 200 ml⁻¹. While the kinetic data support pseudo-second order, a pseudo-first order model shows very poor fit. Adsorption isotherms were obtained at three different temperatures (288, 298 and 308 K). The fitness of adsorption data to the Langmuir and Freundlich isotherms was investigated. In addition, the thermodynamic parameters such as isosteric enthalpy of adsorption (Δ H _ads) _y , isosteric entropy of adsorption (Δ S _ads) _y and free energy of adsorption Δ G ⁰_ads were calculated. BET surface area measurements were made to reveal the adsorptive characteristics of the produced active carbon. The surface area of the activated carbon produced with 20% w/w ZnCl₂ solution was 790.25 m² g⁻¹.     

Removal of Pb(II) from aqueous solution by adsorption using activated tea waste

A basic investigation on the removal of Pb(II) ions from aqueous solutions by using activated tea waste was conducted in batch conditions. An inexpensive and effective adsorbent was developed from waste tea leaves for the uptake of Pb(II) from aqueous solution. The influence of different experimental parameters—shaking time, particle size, adsorbent dose, initial pH, temperature, etc.—on lead uptake was evaluated. Lead is adsorbed by the developed adsorbent up to maximum of 99.7%. The initial Pb(II) concentrations were 5, 10, 15 and 20 mg/l in the experiment. The adsorption was found to be exothermic in nature. The Langmuir, Freundlich and Tempkin isotherm models were tried to represent the equilibrium data of Pb(II) adsorption. The adsorption data was fitted very well to the Langmuir isotherm model in the studied concentration range of Pb(II) adsorption. Isotherms have been used to determine thermodynamic parameters of the process: free energy change (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°). Column experiments were performed to study the practical applicability of the system. The kinetics and the factors controlling the adsorption process were also discussed. Activated tea waste is a better adsorbent compared to other adsorbents available in literature.     

Batch Removal of Crystal Violet from Aqueous Solution by H2SO4 Modified Sugarcane Bagasse: Equilibrium,Kinetic, and Thermodynamic Profile

Batch adsorption studies were carried out using H₂SO₄ modified sugarcane bagasse (HMSB) for the removal of hazardous Crystal Violet (CV) dye from aqueous solutions. The effects of initial solution pH, adsorbent dose, and temperature on the adsorption process were investigated. The Langmuir isotherm model well described the equilibrium dye uptake while the pseudo-second-order kinetic model showed good agreement with the experimental kinetic data. Gibb's free energy change (ΔG⁰) was spontaneous for all interactions, and the adsorption process exhibited endothermic enthalpy values. Results suggest that HMSB is an effective adsorbent for the removal of CV from wastewater.     

Humic acid-immobilized polymer/bentonite composite as an adsorbent for the removal of copper(II) ions from aqueous solutions and electroplating industry wastewater

In this study, humic acid (HA) was immobilized onto amine-modified polyacrylamide/bentonite composite (Am-PAA-B) which was prepared by direct intercalation polymerization technique and the product (HA-Am-PAA-B) was used as an adsorbent for the removal of copper(II) ions from aqueous solutions. The surface characteristics of bentonite, Am-PAA-B and HA-Am-PAA-B were investigated. The adsorbent behaved like a cation exchanger and more than 99.0% Cu(II) ions’ removal was observed at the pH range 5.0–6.0. Kinetic and isotherm experiments showed that amount of Cu(II) ions adsorbed increases with increase of the initial concentration and temperature. The adsorption kinetic data were interpreted by pseudo-first-order and pseudo-second-order rate equations. The suitability of Langmuir, Freundlich and Dubinin–Radushkevich (D-R) adsorption models to the equilibrium data was investigated. The Langmuir isotherm was found to provide the best theoretical correlation of the experimental equilibrium data. The thermodynamic and kinetic activation parameters were derived to predict the nature of adsorption process and discussed in detail. The isosteric heat of adsorption was constant even after increase in surface loading. The removal efficiency of HA-Am-PAA-B was tested using electroplating industry wastewater. The desorption of adsorbed Cu(II) ions was achieved by 0.1 M HCl and four adsorption/desorption cycles were performed without significant decrease in the adsorption capacity.     

Removal of Pb(II) from aqueous solutions by adsorption onto clayey soil of Indian origin: Equilibrium, kinetic and thermodynamic profile

The feasibility of applying natural, untreated clayey soil as low-cost alternative adsorbent for Pb(II) removal from aqueous solutions was investigated with a batch experimental set-up. Experiments were carried out as a function of initial solution pH (1?C8), contact time (10?C360 min), initial Pb(II) concentration (20?C100 mg L^?1), adsorbent dose (0.5?C5 g) and temperature (303?C333 K). Adsorption equilibrium data were well described by the Langmuir isotherm with maximum adsorption capacity of 121.86 mg g^?1 at 303 K. Adsorption of Pb(II) followed pseudo-second-order kinetics. Gibbs free energy (??G⁰) was spontaneous for all interactions, and the adsorption process exhibited exothermic enthalpy values. The adsorbent was easily regenerated by using 0.1M HNO₃ solution and was reused for five sorptiondesorption cycles without any considerable loss in adsorption capacity. It could be concluded that clayey soil may be used as an inexpensive and effective adsorbent without any treatment or any other modification for the removal of Pb(II) ions from aqueous solutions.     

温度-压力-吸附方程在计算煤岩等量吸附焓的应用

用鄂尔多斯盆地的长焰煤、肥煤、瘦煤和贫煤4个煤样的系列等温吸附实验数据来验证一个温度-压力-吸附方程,并探讨等量吸附时吸附平衡压力与温度之间的函数关系。用克劳修斯-克拉佩龙方程求等量吸附焓。提出单位等量吸附焓的概念及计算方法。结果表明：煤样等量吸附焓为负值,证实吸附过程是个放热过程;对于同一煤样,单位等量吸附焓随吸附量的增加而下降是由于吸附介质表面的能量不均匀性所造成。正因为吸附过程是个放热过程,所以吸附先发生在能量较高的位置上,以便放出更多能量;在相等吸附温度和压力条件下,高阶煤有较大的单位等量吸附焓,必有较大的吸附量。同时高阶煤吸附量随着吸附温度的升高而快速衰减,而中低阶煤吸附量衰减却没有那么明显。     

改性碳纳米管对偏二甲肼的吸附热力学研究

对NaOH改性多壁碳纳米管吸附偏二甲肼的特性进行了研究,在温度为296～313K和浓度为44．51～211．41mg／L的范围内,多壁碳纳米管对偏二甲肼的吸附符合弗仑德利希（Freundlich）和兰缪尔（Langmuir）吸附等温式。不同温度下等温吸附曲线的测定和等量吸附焓的计算表明：多壁碳纳米管对偏二甲肼的吸附是吸热的。对偏二甲肼在多壁碳纳米管上的吸附焓、吉布斯自由能、吸附熵的计算表明,该多壁碳纳米管对偏二甲肼的吸附没有化学键生成,并对吸附行为作了机理性解释。     

Adsorption characteristics of benzene on electrospun‐derived porous carbon nanofibers

The adsorption properties of polyacrylonitrile (PAN) carbon nanofibers fabricated by using an electrospinning route were assessed for their applicability as a novel alternative adsorbent. Commercial fiber, A–10, was chosen for comparison. Nitrogen adsorption/desorption isotherms and gravimetric techniques were used to examine the porous structure, adsorption equilibrium, kinetics, and the energetic heterogeneity of the prepared adsorbent. The nitrogen adsorption and desorption isotherms showed that PAN carbon nanofibers are highly microporous with small amounts of mesoporous regions. The equilibrium data of benzene was obtained at three different temperatures (343.15, 383.15, and 423.15) K with pressures up to 4 kPa. The data correlated successfully with the Toth isotherm equation. In addition, by using this isotherm model, the adsorption affinity and isosteric enthalpy of adsorption were determined. The results of the isosteric enthalpy of adsorption and adsorption energy distribution tests/equations revealed that although PAN carbon nanofibers have a heterogeneous surface, they seem to be more homogeneous than commercial carbon fibers. Moreover, the mass transfer and thermal desorption results showed that shallow pores contained within PAN carbon nanofibers may be effective adsorbents for removing toxic compounds. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2454–2462, 2006