Cu^(2+)改性秸秆活性炭的制备及其去除废水中As(Ⅲ)的研究

Preparation of Cu^(2+)-Modified Straw Activated Carbon and Its Use for Removal of As(Ⅲ)from Wastewater

以向日葵秸秆为原料,先经磷酸活化法制得活性炭,然后采用浸渍法制备载铜活性炭,研究Cu2+改性活性炭(Cu-AC)对水溶液中As(Ⅲ)的吸附等温线,并分析了吸附剂的投加量、pH、As(Ⅲ)的初始浓度和温度对Cu-AC去除As(Ⅲ)的影响。结果表明,当吸附剂的投加质量浓度为4 g·L-1、pH为12.0、温度为30℃时Cu-AC对As(Ⅲ)的去除率可达99.95%。Langmuir方程能更好地描述As(Ⅲ)在Cu-AC上的等温吸附特征,静态吸附容量为64.105 mg·g-1;吸附焓变ΔH>0且大于42 kJ·mol-1,说明吸附过程为吸热的化学吸附;吸附自由能ΔG<0,说明吸附为自发的反应;吸附熵变ΔS>0,说明As(Ⅲ)在Cu-AC和水溶液的固-液界面运动的随意性增强。

Sunflower straw is agricultural waste. Here we used it to produce Cu^2＋-modified activated carbon after modification by phosphoric acid and copper employing impregnation method, and then employed the activated carbon to examine adsorption isotherm of As（Ⅲ）in a batch reactor. The effects of reaction time, adsorbent doses, initial concentrations of adsorbent, pH, and temperature on As（Ⅲ）adsorption by the activated carbon were evaluated. The absorbent at 4 g·L^-1 was efficient, and removed As（Ⅲ）up to 99.95% at a pH of 12.0 at 30 ℃.The adsorption data fitted reasonably well to the Langmuir isotherm. The maximum adsorption capacity was 64.105 mg·g^-1. Positive values of adsorption enthalpy ΔH〉 42 kJ·mol^-1 indicated that the adsorption process is endothermic and chemical adsorption in nature. Negative changes in free energy（ΔG）showed that the adsorption is a spontaneous process. Positive values of ΔS suggested increased randomness at the solid-solution interface during the adsorption of As（Ⅲ）from aqueous solution by Cu^2＋-modified activated carbon.