狭叶香蒲活性炭对Cd^(2+)与Pb^(2+)的吸附及机理分析

Adsorption of Cd^(2+) and Pb^(2+) by narrow-leaf cattail activated carbon and mechanism analysis

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、Cd^(2+)和Pb^(2+)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Cd^(2+)和Pb^(2+)的影响。狭叶香蒲活性炭对Cd^(2+)和Pb^(2+)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Cd^(2+)的吸附,Pb^(2+)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Cd^(2+)和Pb^(2+)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 m L/g、平均孔径3.14 nm;活性炭含有羟基、磷酸基、CC键等,等电点为3.3。结果表明,狭叶香蒲活性炭是Cd^(2+)和Pb^(2+)吸附的有效吸附剂,吸附过程包括静电吸附、离子交换等。

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 Cd^2＋and Pb^2＋,adsorption time,temperature,and dose of activated carbon on the adsorption of Cd^2＋and Pb^2＋from aqueous solution were investigated. The adsorption capacity of Cd^2＋and Pb^2＋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 Cd^2＋and Pb^2＋fitted reasonably well with the Langmuir and Freundlich isotherm,respectively. The maximum sorption capacity of Cd^2＋and Pb^2＋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 m L / g,and 3. 14 nm,respectively. The narrow-leaf cattail activated carbon contained hydroxyl groups,phosphate groups,C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 Cd^2＋and Pb^2＋adsorption,the adsorption process is mainly composed of ion exchange and electrostatic adsorption.