Kinetic and equilibrium characterization of uranium(VI) adsorption onto carboxylate-functionalized poly(hydroxyethylmethacrylate)-grafted lignocellulosics.
Kinetic and equilibrium characterization of uranium(VI) adsorption onto carboxylate-functionalized poly(hydroxyethylmethacrylate)-grafted lignocellulosics.
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DOI：
10.1016/j.jenvman.2007.12.010
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发表时间：
2009
影响因子：
8.7
通讯作者：
T. Anirudhan;L. Divya;P. Suchithra
中科院分区：
文献类型：
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作者：
T. Anirudhan;L. Divya;P. Suchithra
研究了一种以椰子核为原料制备的新型吸附剂CP(椰子工业木质纤维素渣)去除水溶液中铀[U(VI)]的可行性。以过二硫酸钾-硫代硫酸钠为氧化还原引发剂，N，N‘-亚甲基双丙烯酰胺为交联剂，将聚甲基丙烯酸羟乙酯接枝到聚氯乙烯上，合成了链端带有羧酸基的聚甲基丙烯酸羟乙酯(PGCP-COOH)。红外光谱结果证实了接枝共聚物的形成和羧酸盐的官能化。X射线衍射研究证实，与CP相比，PGCP-COOH的结晶度降低，有利于官能团向水介质中伸出。用热重分析法(TG)研究了样品的热稳定性。用电位滴定法测定了样品的表面电荷密度随pH的变化。用间歇吸附技术评价了PGCP-COOH去除水溶液中铀(VI)的能力。PH值在4.0~6.0时吸附容量最大。初始浓度为25 mg/L，pH为6.0，吸附剂量为2g/L时，废水的脱色率最高可达99.2%，3h左右即可达到平衡。实验动力学数据采用一级动力学模型进行分析。温度依赖关系表明是一个吸热过程。随着离子强度的增加，在PGCP-COOH表面形成了外球表面络合物，U(VI)的吸附能力降低。平衡数据可用朗缪尔等温线进行最佳模拟。求出了ΔG0、ΔH0和ΔS0等热力学参数来预测吸附的性质。吸附实验也使用商业阳离子交换剂Ceralite IRC-50进行，并与羧酸盐官能度进行比较。通过对模拟核工业废水中铀(VI)的去除试验，验证了该吸附剂的有效性。0.1M HCl对吸附的U(VI)离子有较高的解吸率(96.2±3.3%)。该吸附剂适合重复使用(超过4个循环)，没有明显的容量损失。
This study investigated the feasibility of using a new adsorbent prepared from coconut coir pith, CP (a coir industry-based lignocellulosic residue), for the removal of uranium [U(VI)] from aqueous solutions. The adsorbent (PGCP-COOH) having a carboxylate functional group at the chain end was synthesized by grafting poly(hydroxyethylmethacrylate) onto CP using potassium peroxydisulphate–sodium thiosulphite as a redox initiator and in the presence of N,N′-methylenebisacrylamide as a crosslinking agent. IR spectroscopy results confirm the graft copolymer formation and carboxylate functionalization. XRD studies confirm the decrease of crystallinity in PGCP-COOH compared to CP, and it favors the protrusion of the functional group into the aqueous medium. The thermal stability of the samples was studied using thermogravimetry (TG). Surface charge density of the samples as a function of pH was determined using potentiometric titration. The ability of PGCP-COOH to remove U(VI) from aqueous solutions was assessed using a batch adsorption technique. The maximum adsorption capacity was observed at the pH range 4.0–6.0. Maximum removal of 99.2% was observed for an initial concentration of 25mg/L at pH 6.0 and an adsorbent dose of 2g/L. Equilibrium was achieved in approximately 3h. The experimental kinetic data were analyzed using a first-order kinetic model. The temperature dependence indicates an endothermic process. U(VI) adsorption was found to decrease with an increase in ionic strength due to the formation of outer-sphere surface complexes on PGCP-COOH. Equilibrium data were best modeled by the Langmuir isotherm. The thermodynamic parameters such as ΔG0, ΔH0and ΔS0were derived to predict the nature of adsorption. Adsorption experiments were also conducted using a commercial cation exchanger, Ceralite IRC-50, with carboxylate functionality for comparison. Utility of the adsorbent was tested by removing U(VI) from simulated nuclear industry wastewater. Adsorbed U(VI) ions were desorbed effectively (about 96.2±3.3%) by 0.1M HCl. The adsorbent was suitable for repeated use (more than four cycles) without any noticeable loss of capacity.