壳聚糖对镍吸附作用的研究

Study on Adsorption Characteristics of Chitosan for Nickel

目的研究了壳聚糖对水中Ni^(2+)的吸附性能。方法研究了不同吸附时间(0～360min)、不同温度(25～60℃)、不同初始pH值(4～8)对壳聚糖吸附Ni^(2+)的影响。探讨了壳聚糖对水中Ni^(2+)吸附的动力学和热力学,并对吸附前后壳聚糖的红外光谱进行测定。结果在最佳条件(25℃、pH=7.0、吸附4 h)下,吸附量最高可达42.15 mg/g。动力学研究结果显示,Ni^(2+)在壳聚糖上的吸附过程可以用准二级动力学方程描述(R^2>0.99),经计算,Ni^(2+)的平衡吸附量为45.05 mg/g。热力学研究结果显示,lnk与1/T的线性回归方程为:lnk=-0.827 7/T+3.416 2,其相关系数为0.998 9,焓变(△H^0)为6.88kJ/mol,熵变(△S^0)为28.40 J/(mol·K)。红外光谱表明,壳聚糖分子中的氨基和羟基与Ni^(2+)发生了配位作用。结论壳聚糖可有效地去除水中的Ni^(2+)。壳聚糖对Ni^(2+)的吸附过程是吸热和自发的,并且高温有利于反应的进行,但温度对吸附量的影响并不明显。

Objective To study the adsorption capability of chitosan （CTS） for Ni^2＋ in water. Methods The effects of different adsorption time （0-360 rain）, different temperature （25-60℃） and different initial pH value of the solution （4-8） on the adsorption were investigated： The adsorption kinetics and thermodynamics of CTS for Ni^2＋ in water were also studied and the IR of CTS and CTS-Ni^2＋ were determined. Results The maximal adsorption quantity could reach to 42.15 mg/g in the optimum condition that the temperature is 25 ℃, pH value was 7.0 and the adsorption time was 4 h. The adsorption kinetics showed that the pseudo-second-order equation was suitable for describing the adsorption of CTS for Ni^2＋ and the related correlation coefficients were more than 0.99. The calculated value of equilibrium adsorption quantity of Ni^2＋ was 45.05 mg/g. Study of adsorption thermodynamics showed that the linear regression equation of lnk and 1/T was ink =-0.827 7/T＋3.416 2, and the correlation coefficient was 0.998 9. The enthalpy change （A/C） was 6.88 kJ/moi and the entropy change （△S°） was 28.40 J/（mol. K）. The IR showed that the coordination reaction occurred between -NH2, -OH of CTS and Ni^2＋. Conclusion CTS can effectively remove Ni^2＋ in water. The adsorption of CTS for Ni^2＋ is spontaneous and endothermie. High temperature which is beneficial to the adsorption does not influence the adsorption quantity obviously.