板栗内皮对水溶液中镉的吸附研究

The adsorption of aquatic cadmium(Ⅱ) by chestnut inner shell

采用生物吸附法去除水体重金属污染具有重要的现实意义.本文以板栗内皮为吸附剂,研究了溶液pH值、反应时间、吸附剂投加量对水溶液中镉的吸附量与去除率的影响;通过模型拟合、离子交换实验、电镜扫描(SEM)和红外光谱(FTIR)分析,对吸附机理进行了探讨.结果表明:板栗内皮是一种理想的镉吸附剂,适应pH值范围宽(3～6),达到吸附平衡时间短(15min),吸附容量大(最大值约14.706mg.g-1),去除效率高(在初始Cd2+浓度为250mg.L-1,板栗内皮投加量为10g.L-1的条件下,对溶液中Cd2+的去除率达95%);吸附过程符合伪二级动力学模型表明吸附速率受化学吸附控制;等温吸附模型拟合表明吸附过程主要是表层吸附;SEM照片显示板栗内皮在吸附镉以后,表面聚集了众多的颗状物、粉状物;Dubinin-Radushkevich等温吸附模型和离子交换实验表明离子交换是主要吸附机理,主要的交换离子为K+和Ca2+;FTIR图谱分析表明络合反应也是板栗内皮吸附镉的机理之一,参与络合反应的官能基团主要有—OH、—NH、—COO-、—PO.

Removal of aquatic heavy metals by biosorption is practically important.In this paper,the effect of pH,reaction time and adsorbent dosage on adsorption capacity and removal rates of cadmium in aqueous solution were studied,with chestnut inner shell as adsorbent.The adsorption mechanism was investigated by model simulation,ion exchange experiment,scanning electron microscope and infrared spectroscopy.It was revealed that chestnut inner shell was an ideal absorbent for aquatic cadmium removal characterized by wide adaption range of pH（from 3 to 6）,short sorption equilibrium time（15 min）,high adsorption capacity（maximum of 14.706 mg·g-1） and high removal efficiency of aquatic cadmium（under the condition with an initial Cd2＋ concentration of 250 mg·L-1 and chestnut inner shell dosage of 10 g·L-1,the removal rate of aquatic Cd2 ＋ was up to 95%）.The adsorption process could be fitted with the pseudo-second-order kinetic model and adsorption isotherm models implying that the adsorption rate was controlled by chemical adsorption and mainly surface adsorption occurred.SEM photos showed that after adsorption of cadmium,a lot of particle or ash substance were deposited on the surface of chestnut inner shell.Dubinin-Radushkevich model simulation and ion exchange experiments verified that ion exchange was the main adsorption mechanism with K＋ and Ca2＋ as main exchange ions.FTIR spectra showed complexation was also one of the adsorption mechanisms with —OH,—NH,—COO-,—PO as the major functional groups involved.