核桃青皮生物炭对Cd^(2+)的吸附效应分析

Adsorption Effect of Cd2+by Biochar Derived from Walnut Green Husk

以核桃青皮为原料,分别在300、500、700℃条件下限氧热解制备核桃青皮生物炭,标记为WP300、WP500和WP700,并应用于溶液中Cd^(2+)的吸附,筛选出吸附效果最佳的生物炭材料;研究生物炭投加量、溶液pH、Cd^(2+)初始浓度对生物炭吸附效应的影响;并结合吸附动力学和等温吸附模型探讨核桃青皮生物炭对Cd^(2+)的吸附过程和作用机制。结果表明,500℃下制备的核桃青皮生物炭(WP500)比表面积最大,对Cd^(2+)的吸附效果最佳;当Cd^(2+)的初始质量浓度为100 mg/L,WP500的最佳投加量为1.9 g/L;在pH为1~8,pH的升高使得WP500对Cd^(2+)的去除率提高;温度为303.15 K时,WP500对Cd^(2+)的吸附效果最好,对Cd^(2+)的理论吸附量为99.994 mg/g;WP500对Cd^(2+)的吸附符合Langmuir模型,对Cd^(2+)的吸附动力学更符合准二级动力学模型。

Biochars were produced from walnut green husk pyrolysed under limited oxygen conditions at 300℃,500℃,and 700℃respectively,which were marked as WP300,WP500 and WP700.The biochars were subsequently applied to the adsorption of Cd^(2+) in the aqueous solutions and the biochar material with best adsorption effect was selected.The influencing parameters related to the adsorption process were investigated,including the dosage of biochar,pH and the initial concentration of Cd^(2+).In addition,the adsorption process was described using adsorption kinetics and adsorption isotherm models.The results showed that the walnut green husk biochar prepared at 500℃(WP500)had the largest specific surface area and the best adsorption effects on Cd^(2+);When the initial concentration of Cd^(2+) was 100 mg/L,the optimum dosage of WP500 was 1.9 g/L.When the pH value was 1~8,the increase of pH made the removal rate of Cd^(2+) by WP500 increase.When the temperature was 303.15 K,the adsorption effect of WP500 on Cd^(2+) was the best,and the theoretical adsorption capacity for Cd^(2+) was 99.994 mg/g.The adsorption process of Cd^(2+) by WP500 was properly fitted by pseudo-second-order model and the Langmuir model.