Equilibrium and Kinetic Studies for Fluoride Adsorption from Water on Zirconium Impregnated Coconut Shell Carbon

Abstract

The batch adsorptive fluoride removal from water by Zirconium ion impregnated coconut shell carbon (ZICSC) was investigated. ZICSC was found to have fluoride adsorption capacity, 25 to 30 times that of plain activated carbon. The effect of various parameters such as pH, agitation time, and adsorbent dosage on fluoride removal were studied. The fluoride adsorption by ZICSC was above 90% for the entire pH range of 2–9 and the adsorption rate was extremely rapid, with 91% of the adsorption being achieved within 10 min of ZICSC contact for an initial fluoride concentration of 10 mg/L. The experimental data have been analyzed by Langmuir, Freundlich, Redlich‐Peterson, and Temkin sorption isotherm models and the adsorption data for fluoride onto ZICSC were better correlated to the Langmuir isotherm. The batch adsorption kinetics have been tested by first order, pseudo‐first order, and pseudo‐second order kinetic models with the subsequent determination of the rate constants of adsorption. The comparison of ZICSC with other adsorbents suggests that ZICSC provides a cost‐effective working solution to the defluoridation problem in the developing countries by its great potential application in fluoride removal from water.     

饮用水沸石除氟的实验研究

本文通过静态搅拌实验和恒温震荡实验研究了接触时间、pH值、温度对沸石除氟效果的影响 ;测定了在 2 5℃时沸石除氟的吸附等温线 ,并对吸附等温线进行拟合 ,证明其符合Langmuir吸附等温式qe=0 .0 68Ce/(1 0 .0 868Ce) ;对吸附速度进行了数学处理 ,证明其符合斑厄姆吸附速度公式dq/dt=0 .0 0 1 8(qe-q) /t0 .2 2 。     

Kinetic and Equilibrium Studies on the Adsorption of Crystal Violet Dye using Kaolin as an Adsorbent

Abstract

Experimental investigations are carried out to adsorb toxic crystal violet dye from aqueous medium using kaolin as an adsorbent. Characterization of kaolin is done by measuring

1. particle size distribution using particle size analyzer,

2. BET surface area using BET surface analyzer,

3. structural analysis using X ray diffractometer, and

4. microscopic analysis using scanning electron microscope.

The effects of initial dye concentration, contact time, kaolin dose, stirring speed, pH, and temperature are studied for the adsorption of crystal violet in batch mode. Adsorption experiments indicate that the extent of adsorption is strongly dependent on the pH of the solution. Free energy of adsorption (ΔG ^o ), enthalpy (ΔH ^o ), and entropy (ΔS ^o ) changes are calculated to know the nature of adsorption. The calculated values of ΔG ^o are ?4.11 and ?4.48 kJ/mol at 295 K and 323 K, respectively, for 20 mg/L of dye concentration, which indicates that the adsorption process is spontaneous. The estimated values of ΔH ^o and ΔS ^o show the negative and positive sign, respectively, which indicate that the adsorption process is exothermic and the dye molecules are organized on the kaolin surface in more random fashion than in solution. The adsorption kinetic has been described by pseudo first order, pseudo second order and intra‐particle diffusion models. It is observed that the rate of dye adsorption follows pseudo second order model for the dye concentration range studied in the present case. Standard adsorption isotherms are used to fit the experimental equilibrium data. It is found that the adsorption of crystal violet on kaolin follows the Langmuir adsorption isotherm.     

Adsorption Thermodynamic and Kinetic Studies of Fluoride Aqueous Solution Treated with Waste Iron Oxide

This study uses a waste iron oxide material (BT3), which is a by-product of the fluidized-bed Fenton reaction (FBR–Fenton), for the treatment of a fluoride (F^?) solution. The purpose of this study is to investigate a low-cost sorbent as a replacement for the current costly methods of removing fluoride from wastewater. X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) are used to characterize the BT3. Contact time, F^? concentration (from 0.75 to 6 mmol L^?1), and temperature (from 303 to 323 K) are used as operation parameters to treat the fluoride. The highest F^? adsorption capacity of the BT3 adsorbent was determined to be 1.17 mmol g^?1 (22.2 mg g^?1) for a 6 mmol L^?1 initial F^? concentration at pH 3.9 ± 0.2 and 303 ± 1 K. Adsorption data were well described by the Langmuir model, and the thermodynamic constants of the adsorption process, ΔG°, ΔH°, and ΔS°, were evaluated as ?1.63 kJ mol^?1 (at 303 K), ?1.75 kJ mol^?1, and ?52.4 J mol^?1 K^?1, respectively. Additionally, a pseudo-second-order rate model was adopted to describe the kinetics of adsorption. BT3 could be regenerated with NaOH, and the regeneration efficiency reached 95.1% when the concentration of NaOH was 0.05 mol L^?1.     

Adsorption of Furfural from Aqueous Solution onto Activated Carbon: Kinetic,Equilibrium and Thermodynamic Study

Abstract

The present study aims to evaluate the influence of various experimental parameters viz. initial pH (pH ₀), adsorbent dose, contact time, initial concentration and temperature on the adsorptive removal of furfural from aqueous solution by commercial grade activated carbon (ACC). Optimum conditions for furfural removal were found to be pH ₀ ≈ 5.9, adsorbent dose ≈ 10 g/l of solution and equilibrium time ≈ 6.0 h. The adsorption followed pseudo‐second‐order kinetics. The effective diffusion coefficient of furfural was of the order of 10^?13 m²/s. Furfural adsorption onto ACC was found to be best represented by the Redlich‐Peterson isotherm. A decrease in the temperature of the operation favorably influenced the adsorption of furfural onto ACC. The positive values of the change in entropy (ΔS ⁰); and the negatived value of heat of adsorption (ΔH ⁰) and change in Gibbs free energy (ΔG ⁰) indicated feasible, exothermic, and spontaneous nature of furfural adsorption onto ACC.     

地下水氟污染的壳聚糖吸附处理工艺

饮用水中的氟离子过量会对人体健康产生危害,造成氟斑牙、氟骨病等[1]。我国氟污染主要集中在东北、华北和西北的地下水,部分地区最高含量可达5 mg/L,远超过我国生活饮用水卫生标准(GB 5749—2006)规定的最大允许浓度1.0 mg/L。该文针对近几年采用壳聚糖处理地下水中氟污染的相关研究进行总结,综述了壳聚糖除氟的吸附机理、改性方法以及影响因素的研究进展,并针对壳聚糖处理地下水中氟污染的未来发展方向提出了建议。     

Adsorption of bark derived polyphenols onto functionalized nanocellulose: Equilibrium modeling and kinetics

This article describes the kinetics and capacity of adsorbing condensed conifer tannins onto cationic cellulose nanocrystals (CCNCs). Batch adsorption experiments were carried as a function of pH, contact time, and initial tannin concentration with constant cationic cellulose nanocrystal concentration (0.01%). The adsorption process was highly pH dependent as adsorption capacities ranged from 13.2 mg/g to 112.7 mg/g at pH of 3–10. The amount of tannin adsorbed per unit mass of the cationic cellulose nanocrystals increased with increasing of tannin concentration until equilibrium was attained. The experimental data followed the Langmuir adsorption model, and the maximum experimental and theoretical adsorption capacities for the cationic nanocrystals reached 1,008 mg/g and 1,111 mg/g, respectively. The kinetics of adsorption was described best by the pseudo-second-order kinetics indicating a chemisorption process. The inherent adsorption has interesting applications for CCNC-complexes with natural polyphenolics in green chemical applications for adhesives, adsorbents, preservatives, and packaging materials.     

叶蜡石及其改性粉体对亚甲基兰吸附行为的研究

本实验将叶蜡石原矿粉进行改性处理,制备了酸洗粉、球磨粉、酸洗-球磨粉三种改性粉体,从动力学、热力学两个方面系统研究并比较了叶蜡石原矿粉及其改性粉体对水溶液中亚甲基兰(MB)的吸附行为。动力学结果表明,叶蜡石对MB的吸附动力学曲线符合伪二阶反应模型;酸洗-球磨粉快速阶段的吸附反应速率明显大于原矿粉,酸洗-球磨粉的吸附量在反应开始5min时达4.24mg·g-1,而原矿粉为3.71mg·g-1。热力学结果表明,酸洗-球磨粉的平衡吸附容量也较原矿粉明显增大,在MB溶液浓度10~60mg·L-1范围内,酸洗-球磨粉的平衡吸附容量为4.82~10.54mg·g-1,而原矿粉为4.55~9.59mg·g-1;吸附方式均符合Langmuir吸附模型。     

Mn-Al双氢氧化物对氟离子的吸附热力学和动力学研究

采用共沉淀法制备Mn-Al双氢氧化物吸附剂,并利用扫描电子显微镜(Scanning Electron Microscope,SEM)、红外光谱(Fourier transform infrared spectroscopy,FTIR)和比表面积分析仪(Brunauer-Emmett-Teller surface area,BET)等对吸附材料进行了分析.并考察了其对氟离子吸附过程的热力学和动力学,并计算不同温度下该吸附过程的热力学参数.实验结果表明:pH值对Mn-Al吸附剂除氟效能有一定的影响,pH值为6时吸附容量最佳达到了44.15 mg·g-1;实验数据遵循拟二级反应动力学模型;Mn-Al吸附剂对氟离子的吸附符合Langmuir-Freundlich吸附等温模型;热力学参数吉布斯自由能(△G0)小于零,焓变(△H0)＞0,熵变(△S0)＞0,说明Mn-Al双氢氧化物吸附剂对氟离子的吸附反应是自发吸热熵增过程.     

Adsorption Equilibrium and Kinetics of Toxic Dye-Erythrosine B Adsorption onto Montmorillonite

Erythrosine B is extensively used in the textile and food industry. It is reported to be a neurotoxicant and is carcinogenic in nature. It can induce DNA damage in the gastrointestinal organs even at low doses. In this study, adsorption efficiency of montmorillonite (MMT) has been investigated for the removal of erythrosine B (EB) from aqueous solution. The batch adsorption model was developed to predict the equilibrium adsorption capacity with respect to the pH of the dye solution, contact time, initial dye concentration, and adsorbent dosage. A maximum monolayer adsorption capacity of 578.03 mg/g was obtained at the original pH (7.5) of the aqueous dye solution within 5 minutes of contact time. It was found that the Langmuir adsorption isotherm yielded the most favorable representation of the adsorption behavior of EB. The dye was found to be chemisorbed on the adsorbent as confirmed by the FTIR spectral analysis. Although anionic in nature, the dye was found to be intercalated into the clay interlayers as suggested by the X-ray diffraction studies.     

Adsorption of Congo Red Dye over Pendent Chlorobenzylidine Rings Present on Polythioamide Resin: Kinetic and Equilibrium Studies

The removal of Congo Red (CR) from an aqueous solution, using aromatic polythioamide resin (PTA) was studied. The effective pH and equilibrium time for the maximum adsorption of the CR on the PTA is found to be 7 and 45 min, respectively. Among the three kinetic models studied, the pseudo-second order kinetic model describes adsorption of the CR on the PTA efficiently. The maximum adsorption capacity of PTA for CR calculated from the Langmuir isotherm is 452.1 mg/g. The surface morphology of the PTA and dye adsorbed PTA were determined using scanning electron microscopy. The adsorption efficiency of the PTA was retained even after four cycles.     

活性炭对单宁酸的吸附去除性能

三卤甲烷(THMs)是水中天然有机物在氯化消毒过程中产生的对人体有致癌作用的挥发性物质,腐殖酸是生成消毒副产物的主要前驱物。活性炭能够去除水中的多种有机污染物,其中对腐殖酸的去除性能可以通过单宁酸值来表征。通过间歇试验,研究了两种活性炭对单宁酸的吸附行为,探索其对单宁酸的吸附规律。结果表明308 K时,1#炭对单宁酸的饱和吸附量较大,为616.0 mg/g。升高温度有利于两种活性炭对单宁酸的吸附,表明吸附过程为吸热过程。此外,两种活性炭对单宁酸的吸附动力学可以用Largergren伪二级速率方程很好地拟合,吸附过程是双速过程。1#炭对单宁酸的吸附速率更快,比3#炭具有更高的单宁酸吸附性能。1#和3#炭对单宁酸的吸附活化能依次分别为17.5和3.9 kJ/mol,说明1#炭的反应速率随温度的升高增加得较快,符合Arrhenius的经验方程,吸附反应速率随温度升高而加快的规律,活性炭对单宁酸的吸附可认为是化学吸附。     

聚丙烯酸/锂藻土纳米复合水凝胶对亚甲基蓝吸附性能的研究

研究了聚丙烯酸/锂藻土纳米复合水凝胶对染料亚甲基蓝的吸附性能,考察了不同吸附条件,包括凝胶用量、染料浓度、吸附时间及溶液p H条件等对水凝胶吸附效果的影响。实验结果表明,水凝胶对亚甲基蓝的吸附过程在30 min内即能达到平衡,吸附速度快;最大吸附容量高达1 192.9 mg/g,是普通吸附剂吸附容量的几十倍,吸附效果好;凝胶的吸附等温线拟合结果符合Freundlich模型,动力学拟合结果显示,凝胶对亚甲基蓝的吸附过程符合二级动力学模型。     

羟基磷灰石对水溶液中锌离子的吸附动力学研究

以废弃的鸡蛋壳为原料,制备了碳羟基磷灰石,用红外光谱对其结构进行了表征。将得到的碳羟基磷灰石进行水溶液中锌离子的吸附,考察了吸附过程的动力学,结果表明,碳羟基磷灰石对水溶液中锌离子的吸附符合二级反应动力学方程：1/ρR=0.0536t＋1.0992,相关系数R=0.99724,其拟合度比较好。     

The Adsorption of Arsenic Ions Using Beidellite,Zeolite, and Sepiolite Clays: A Study of Kinetic,Equilibrium and Thermodynamics

Arsenic contamination in drinking water resources is a global problem; therefore, its removal from drinking water has become an important sustainable matter. The adsorption process can be more cost-effective and applicable, especially, if the absorbents used in the process are low-cost natural geo-materials. Beidellite, zeolite, and sepiolite are inexpensive and natural minerals available locally, modified, and used as adsorbents for the removal of arsenic ions from aqueous solutions in batch experiments. The kinetics of the adsorption process was separately tested for the pseudo-first order and pseudo-second order reactions and intra-particle diffusion models. The rate constants of adsorption for all these kinetic models were calculated. The comparison among the models showed that the pseudo second-order model best described the adsorption kinetics. Applied to the experimental equilibrium, at different temperatures were the Langmuir and Freundlich isotherm models. The Langmuir isotherm was used to calculate the adsorption capacities (Q°) of minerals for arsenic ions. The adsorption capacities of these three modified minerals, at different temperatures, ranged from 476 to 841 µg/g. Thermodynamic studies showed that the arsenic uptake reactions by minerals were endothermic and spontaneous in nature. Bottled spring water containing arsenic, sold in markets, was used to conduct the arsenic adsorption study beidellite, zeolite, and sepiolite, minerals which efficiently removed the arsenate ions from the bottled drinking water. The use of modified beidellite, zeolite, and sepiolite as adsorbents in the arsenic ion removal processes is possible, based on the optimum parameters found.     

颗粒化铁-铝-铈纳米吸附剂的除氟性能

采用在流化床中喷雾包覆方法将纳米吸附剂包覆在玻璃珠表面制备颗粒化吸附剂,考察了所制颗粒化纳米铁-铝-铈复合氧化物吸附剂在含氟水中的除氟性能. 结果表明,含氟初始浓度为10 mg/L时,颗粒化吸附剂的吸附速率符合拟一级反应动力学模型,吸附等温线符合Langmuir吸附模型,饱和吸附量达5.9 mg/g. 吸附容量随含氟水初始pH值升高而降低,吸附过程中溶液pH值逐渐趋近于中性;含氟水中其他阴离子对F-的吸附存在不同程度的竞争,竞争离子的影响顺序为NO3-"Cl-相似文献   

新型超高交联树脂对2-甲基-4-氯苯氧乙酸的吸附机理研究

在静态条件下,研究了水溶液中超高交联树脂ZZ和大孔吸附树脂Am berlite XAD-4吸附2-甲基-4-氯苯氧乙酸的热力学特性,测定了283K和323K温度下的吸附等温线。对两个温度下的吸附等温线的比较和热力学数据的计算,结果表明,在稀溶液中两种吸附剂对2-甲基-4-氯苯氧乙酸的吸附同时符合Langm u ir和F reund lich模型,并且两种吸附剂对2-甲基-4-氯苯氧乙酸的吸附都是放热过程。     

氯霉素在活性炭上的吸附平衡与动力学

为去除水体中残留的氯霉素,采用生物相容性佳的活性炭作吸附剂,测定了25,30,35℃下氯霉素在自制活性炭上的吸附平衡与动力学,并与商用竹炭作对比。结果表明高比表面积活性炭是去除水体中残留氯霉素的高效吸附剂,活性炭的吸附容量随着吸附剂比表面积和孔容的增大而增大,但随温度从25,30到35℃升高而减小,自制高比表面积活性炭的吸附容量达到3种市售活性炭样品吸附容量的10倍以上;Freundlich吸附等温线方程可较好地描述氯霉素在活性炭上的吸附平衡,准二级方程是用来描述氯霉素在活性炭上吸附的合适动力学模型,并通过拟合得到了其动力学参数。随着温度的升高吸附容量逐渐减小。本研究为活性炭对水体中残留氯霉素的吸附处理提供了科学依据。     

用改性粉煤灰处理含氟废水的试验

通过实验探讨了改性粉煤灰处理含氟废水的影响因素。实验结果表明:经Ca(OH)2溶液改性的粉煤灰的除氟性能与改性试剂Ca(OH)2溶液的浓度、吸附时间、废水氟离子初始浓度、废水pH值、反应温度等因素有关。将氟离子浓度为267.0mg/L的含氟废水的pH调至3.5后,按每升废水中加入经过5%的Ca(OH)2溶液改性烘干的粉煤灰0.05g,在室温下振荡1h,F-去除率可达98.0%。最后对改性粉煤灰处理含氟废水的机理作了初步分析。     

大孔树脂对甘油的静态吸附及其热力学研究

研究了8种大孔树脂对甘油的静态吸附行为,根据吸附等温线研究了吸附热力学性质,在303~323 K和研究的浓度范围内,树脂HPD500对甘油的吸附平衡数据符合Freundlich吸附等温方程。实验结果表明,较大的比表面积和带有一定极性的树脂有利于吸附,吸附过程为放热的物理吸附,降低温度有利于吸附。并计算了甘油在大孔树脂HPD500上的吸附焓变、吉布斯自由能变、吸附熵变,并对吸附行为做了合理的解释。