Adsorption of Cu（Ⅱ） on rice straw char from acidic aqueous solutions

研究了稻草炭对Cu（Ⅱ）的吸附特征,探讨了Cu（Ⅱ）的吸附机制.结果表明,稻草炭对Cu（Ⅱ）有很高的吸附容量,Langmuir方程能很好地拟合Cu（Ⅱ）吸附等温线,因此可以描述稻草炭对Cu（Ⅱ）的吸附,其预测的Cu（Ⅱ）在pH 4.5和pH 5.0时的最大吸附量分别为0.628 mol.kg-1和0.763 mol.kg-1.稻草炭对Cu（Ⅱ）的吸附量随体系pH升高而增加,但吸附Cu（Ⅱ）的解吸率呈相反的变化趋势.当吸附体系pH≤4.5时,Cu（Ⅱ）解吸率大于55%,说明此时以静电吸附为主;在较高pH条件下Cu（Ⅱ）以非静电吸附机制为主.红外光谱的分析结果表明,稻草炭表面有丰富的—COOH和—OH等含氧官能团,Cu2＋与含氧官能团形成有机络合物导致—COOH吸附峰位移.Cu（Ⅱ）吸附使稻草炭颗粒的Zeta电位向正值方向位移.结果说明Cu（Ⅱ）在稻草炭表面发生了专性吸附.

Adsorption of Cu(Ⅱ) on rice straw char from acidic aqueous solutions

Cu(Ⅱ) adsorption by biochars derived from rice straw at 400 ℃ was investigated under acidic conditions.The results indicated that rice straw char has high adsorption capacity for Cu(Ⅱ).Langumir equation can be used to describe the adsorption of Cu(Ⅱ) on the biochar.The maximum adsorption capacity for Cu(Ⅱ) predicted by Langumir equation was 0.628 mol · kg-1 and 0.763 mol · kg-1 at pH 4.5 and pH 5.0,respectively.The adsorption of Cu(Ⅱ) by rice straw char increased with pH,while the desorption rate of pre-adsorbed Cu(Ⅱ) decreased with pH.When pH was less than 4.5,Cu(Ⅱ) desorption rate was greater than 55%,which suggested that Cu(Ⅱ) adsorbed on the biochar mainly through electrostatic attraction under the pH condition.Cu(Ⅱ)adsorbed mainly through non-electrostatic mechanisms by the biochar at higher pH,because the desorption rate under this pH condition was much lower than 50%.FTIR-PAS indicated that there were ample amount of oxygen-containing functional groups(e.g.carboxylate,—COOH;and hydroxyl,—OH) on the biochar.Adsorption of Cu(Ⅱ) caused an apparent shift of the vibrational bands assigned to the carboxyl group.The adsorption of Cu(Ⅱ) also made Zeta potential of the biochar less negative.These results suggest that Cu(Ⅱ) adsorbed on the biochar through the formation of surface complexes.