狭叶香蒲活性炭对Cd2+与Pb2+的吸附及机理分析

为了解狭叶香蒲(Typha angustifolia L.)活性炭的吸附性能及其机理,采用磷酸一步活化法制备了狭叶香蒲活性炭,并对其理化性质进行了表征;通过静态实验,研究了溶液起始pH、Cd2+和Pb2+浓度、吸附时间、温度、活性炭剂量对狭叶香蒲活性炭吸附水溶液中Cd2+和Pb2+的影响。狭叶香蒲活性炭对Cd2+和Pb2+的吸附量随溶液起始pH与温度的增加而增加,吸附平衡时间约为10 min;热力学分析表明,吸附过程自发而且吸热,吸附动力学实验结果符合拟二级动力学模型, Langmuir吸附等温模型能更好地拟合狭叶香蒲活性炭对Cd2+的吸附, Pb2+的平衡吸附量与Freundlich模型的拟合性更好。25℃条件下,由Langmuir线性模型拟合得到的Cd2+和Pb2+最大吸附量Qm分别为83.33和116.28 mg/g。狭叶香蒲活性炭的理化性质分析表明,活性炭表面凹凸不平、多孔,比表面积为780.42 m2/g、孔容23.29 mL/g、平均孔径3.14 nm;活性炭含有羟基、磷酸基、C[FY=, 1]C键等,等电点为3.3。结果表明,狭叶香蒲活性炭是Cd2+和Pb2+吸附的有效吸附剂,吸附过程包括静电吸附、离子交换等。

Adsorption of Cd2+ and Pb2+ by narrow-leaf cattail activated carbon and mechanism analysis

To understand the adsorption characteristics and mechanism of narrow-leaf cattail activated carbon, activated carbon were prepared using Typha angustifolia L by phosphoric acid activation, and its physicochemical properties were characterized.The effects of initial pH value, concentration of Cd2+ and Pb2+, adsorption time, temperature, and dose of activated carbon on the adsorption of Cd2+ and Pb2+ from aqueous solution were investigated.The adsorption capacity of Cd2+ and Pb2+ on narrow-leaf cattail activated increased with the increase of initial pH value and temperature of solution.It needed about 10 min to reach adsorption equilibrium;adsorption process was spontaneous and endothermic, the pseudo second-order sorption model depicted the adsorption process well, and the equilibrium adsorption data of Cd2+ and Pb2+ fitted reasonably well with the Langmuir and Freundlich isotherm, respectively.The maximum sorption capacity of Cd2+ and Pb2+ obtained from the Langmuir adsorption isotherm reached 83.33 mg/g and 116.28 mg/g, respectively, at 25℃.The physicochemical properties analysis of activated carbon indicated that the surface of activated carbon was rough and porous, the specific surface area, total pore volume, and average pore diameter were 780.42 m2/g, 23.29 mL/g, and 3.14 nm, respectively.The narrow-leaf cattail activated carbon contained hydroxyl groups, phosphate groups, C[FY=, 1]C, and so on and the isoelectric point was 3.3.The results suggest that narrow-leaf cattail activated carbon is an effective adsorbent for Cd2+ and Pb2+ adsorption, the adsorption process is mainly composed of ion exchange and electrostatic adsorption.