壳聚糖/羟基镧复合改性膨润土对Pb(Ⅱ)的吸附特性

Adsorption property on Pb(Ⅱ) of bentonite modified by chitosan/hydroxy-lanthanum

为改善钠基膨润土对Pb(Ⅱ)的吸附效果,以羟基镧和壳聚糖作为柱化剂,采用水热法对钠基膨润土进行柱撑改性,制得壳聚糖/羟基镧复合柱撑膨润土(GZ-P)。利用XRD、FTIR、SEM等手段对GZ-P进行表征分析,研究了GZ-P对Pb(Ⅱ)的吸附行为。研究结果表明:壳聚糖和羟基镧离子插入到膨润土层间,起到了"柱撑"的作用,颗粒变得更加饱满密实,表面空隙和粗糙程度有所增加;在25℃,吸附时间为120min时,GZ-P对Pb(Ⅱ)的去除率和吸附量随pH值的增加呈现先增后减再增的态势,在pH=4时去除率最高,达到98.93%,最大吸附量为33.67mg·g-1,在pH=6时的吸附量最少,但去除率也超过85%;GZ-P对Pb(Ⅱ)的吸附等温线与Langmuir方程拟合较好,为近单分子层吸附;吸附动力学过程可用准二级动力学模型描述,主要受化学吸附的控制。

To improve adsorption effect of Na-bentonite on Pb（Ⅱ）,chitosan/hydroxy-lanthanum complex pillared bentonite（GZ-P）is prepared by hydrothermal synthesis method using Na-Bentonite modified with the mixture of chitosan and hydroxy-lanthanum cation as pillared agent.The properties of GZ-P are characterized by X-ray diffraction（XRD）,Fourier transform infrared spectrum（FTIR）,scanning electron microscopy（SEM）and other analytical methods.And the adsorption property of Pb（Ⅱ）by GZ-P is discussed.The results show that the mixture of chitosan and hyroxy-lanthanum cation intercalates into bentonite and plays the role of pillar.The particles become fuller and denser.Surface voids and roughnessincreases.Removal rate and adsorption capacity of Pb（Ⅱ）by GZ-P increase first and then decrease,and increase again with the increase of PH value when the temperature is 25 ℃ and reaction time is 120 min.The highest removal rate reached to 98.93%and the maximum Pb2＋adsorption capacity is 33.67 mg/g when initial pH is 4.The least adsorption capacity is found when pH is 6.However,the removal rate is more than 85%even under that condition.Langmuir equation could better imitate the adsorption isothermal process of GZ-P to Pb（Ⅱ）,and the adsorption process could be fitted by the pseudo-second order model,which indicates that Pb（Ⅱ）ions are adsorbed onto GZ-P by chemical interactions via monolayer.