不同制备温度下水生植物生物炭吸附Cd2+研究

Adsorption Characteristics and Mechanism of Cd2+ on Biochar with Different Pyrolysis Temperatures Produced from Hydrophyte

选用水生植物为生物质原料在不同热解温度下(300、500、700℃)制备生物炭,分析3种生物炭理化性质差异,研究吸附影响因子对生物炭吸附Cd^2+的影响以及吸附机理。结果表明,随着热解温度的升高,官能团数量减少,灰分增加,pH增大。3种生物炭的吸附过程可用Langmuir等温线较好的拟合,饱和吸附量B500>B700>B300。吸附动力学过程符合准2级动力学方程,说明以化学吸附为主。pH在2~6时,生物炭的吸附量随pH增加而增大。随着投加量的增加平衡吸附量减小,去除率增大。水生植物生物炭去除Cd^2+的机理可能是阳离子-π作用、离子交换、沉淀、络合反应。水生植物生物炭是一种能有效去除水中Cd^2+的吸附剂。

Three biochars were generated from hydrophyte under different pyrolysis temperatures of 300, 500 and 700 ℃, then the differences of physicochemical properties among the three biochars were analyzed, and studied the effects of influence factor on biochars adsorption for Cd^2+ and the adsorption mechanism. The results showed that as pyrolysis temperature increased, the number of functional groups decreased, while the ash content, pH, increased. The adsorption behavior of Cd^2+ on three biochars could be better fitted by Langmuir isotherm, and the order of saturated adsorption capacity was B500> B700>B300. The adsorption kinetics process conformed to the pseudo-second-order equation, indicating that the chemical adsorption was the main. The biochars adsorption capacity increased with the increase of pH when pH was in the range of 2~6. With the increase of dosage, the equilibrium adsorption capacity decreased, and the removal rate increased. The mechanism of removal of Cd2+ by hydrophyte biochar might be cation-π interaction, ion exchange, precipitation, and complexation. The hydrophyte biochar is an adsorbent which can effectively remove Cd^2+ from water.