Li Kun-quan, Zheng Zheng, Jiang Jian-chun, Zhang Ji-biao
College of Engineering, Nanjing Agricultural University, Nanjing 210031, China.
Huan Jing Ke Xue. 2010 May;31(5):1402-8.
Low-cost high surface area microporous carbons were prepared from cotton stalk and cotton stalk fiber by H3PO4 activation. The adsorption of lead ions on the carbons was investigated by conducting a series of batch adsorption experiments. The influence of solution pH value, contact time and temperature was investigated. The adsorption kinetics, thermodynamic behavior and mechanism were also discussed. The surface area and pore structure of the activated carbons were analyzed by BET equation, BJH method and H-K method according to the data from nitrogen adsorption at 77K. Boehm titration, Fourier transform infrared spectroscopy (FTIR), the point of zero charge (pH(PZC)) measurement and elemental analysis were used to characterize the surface properties. The results show that the carbons from cotton stalk and cotton stalk fiber have high surface area of 1570 and 1731 m2 x g(-1), and high content of oxygen-containing functional groups of 1.43 and 0.83 mmol x g(-1). The adsorption experiments show that the carbons have high adsorption capacity for lead, and the maximum adsorption equilibrium amount was found to be 120 mg x g(-1). The adsorption amount increased with contact time, and almost 80% of the adsorption occurred in the first 5 min. The pseudo-second-order model describes the adsorption kinetics most effectively. The Freundlich isotherm was found to the best explanation for experimental data. The negative change in free energy (delta G0) and positive change in enthalpy (delta H0) indicate that the adsorption is a spontaneous and endothermic process, and the adsorption of lead ions onto the carbons might be involved in an ion-exchange mechanism.
通过磷酸活化法，以棉秆和棉秆纤维为原料制备了低成本、高比表面积的微孔碳。通过进行一系列批量吸附实验，研究了铅离子在这些碳材料上的吸附情况。考察了溶液pH值、接触时间和温度的影响。还讨论了吸附动力学、热力学行为及机理。根据77K下氮气吸附数据，采用BET方程、BJH方法和H-K方法分析了活性炭的比表面积和孔结构。采用 Boehm 滴定法、傅里叶变换红外光谱（FTIR）、零电荷点（pH(PZC)）测量和元素分析对表面性质进行了表征。结果表明，棉秆和棉秆纤维制备的碳材料比表面积分别高达1570和1731 m2·g-1，含氧官能团含量分别为1.43和0.83 mmol·g-1。吸附实验表明，这些碳材料对铅具有较高的吸附容量，最大吸附平衡量为120 mg·g-1。吸附量随接触时间增加，近80%的吸附在最初5分钟内发生。准二级模型能最有效地描述吸附动力学。发现Freundlich等温线最能解释实验数据。自由能的负变化（ΔG0）和焓的正变化（ΔH0）表明吸附是一个自发的吸热过程，铅离子在碳材料上的吸附可能涉及离子交换机制。
