黄芪废渣生物吸附剂的制备及其对Pb^(2+)的吸附

Fabrication of biological adsorbent from Astragalus membranaceus waste and its adsorption of Pb^(2+)

以黄芪废渣为原料,用均苯四甲酸二酐对其进行化学改性,并将其用于模拟废水中Pb^(2+)的吸附.通过傅里叶红外光谱、扫描电子显微镜等方法对改性黄芪废渣生物吸附剂进行表征.结果表明:改性后黄芪废渣羧基官能团增加,表面粗糙,更有利于对Pb^(2+)的吸附.在pH值为5.0,吸附时间为1h,吸附剂量为10g·L^(-1)的条件下,对浓度为500mg·L^(-1)的Pb^(2+)吸附率为99.53%.改性吸附剂对Pb^(2+)的吸附可以用准二级动力学方程描述,等温吸附符合Langmuir和Freundlich模型,根据Langmuir方程,25℃时最大吸附量为193.1mg·g^(-1),高于黄芪废渣改性前的最大吸附量(58.89mg·g^(-1)).改性后的黄芪废渣生物吸附剂可以再生重复使用5次以上.

Taking Astragalus membranaceus waste as raw material, its chemical modification was conduc- ted with pyromellitic dianhydride and it was used to simulate the adsorption of Pb^2＋ in waste water. The modified Astragalus membranaceus waste as a biologic adsorbent was characterized with Fourier transform infrared spectroscopy and scanning electron microscopy. The result indicated that the number of carboxyl functional groups would increase in the modified waste, the surface of the modified Astragalus membranaceus waste would be coarse, which was beneficial to Pb^2＋ adsorption. Under the condition of 25℃, value of pH of 5.0, adsorption time of I h, and Astragalus membranaceus waste dosage of 10 g·L^-1, the adsorption rate of the modified Astragalus membranaceus waste with initial concentration of Pb^2＋ of 500 mg·L^-1 would be 99. 53%. Pb^2＋ adsorption of modified adsorbent could be described with pseudo-sec- ond-order kinetic equation and the isothermal adsorption would be consistent with Langmuir and Freundlich models. According to the Langmuir equation, the maximum adsorption capacities of modified adsorbent for Pb^2＋ adsorption would be 193. 1 mg·g^-1 at 25℃, being higher than that of adsorbent before modification （58. 89 mg·g^-1）. The biosorption agent could be recycled for more than five times.