烟草秸秆及其生物炭对Cd²⁺的吸附特性

Adsorption Characteristics of Cd²⁺ by Tobacco Stalk and Its Biochar

摘要: 为了研究烟草秸秆材料对重金属Cd²⁺的吸附效果及其吸附机制，以烟草秸秆粉末及它的生物炭为材料，在不同材料用量、吸附时间、吸附温度、Cd²⁺浓度、pH值的条件下，研究了两种材料对Cd²⁺吸附效果。结果表明，在100 mg·g^-1的Cd²⁺浓度下，烟秆粉末大约在50 min左右达到吸附平衡，最佳用量为0.2 g；烟秆生物炭大约在8 h左右时达到吸附平衡，最佳用量为0.05 g；两者的适宜吸附温度都在30℃左右；两者的最佳吸附pH值都在7左右。在此条件下，两者的吸附率分别达到了70%、80%。两者吸附都可用准一级动力学方程与准二级动力学方程拟合。烟秆粉末的吸附等温线符合Langmuir方程，而烟秆生物炭在低Cd²⁺浓度时符合Langmuir方程，在高Cd²⁺浓度时符合Freundlich方程。总体上烟秆粉末以物理吸附为主，而烟秆生物炭是一个物理吸附与化学吸附兼具的过程。所以，两个Cd²⁺吸附材料均具有应用潜力。

Abstract: In order to study the adsorption characteristics and mechanism of Cd²⁺ by tobacco stalk powder and its biochar, the effect of different material dosage, adsorption time, adsorption temperature, Cd²⁺ concentration, and pH were investigated. The results showed that at a Cd²⁺ concentration of 100 mg·g⁻¹, the tobacco stalk powder has reached adsorption equilibrium in about 50 minutes, the optimal dosage is 0.2 g; the tobacco stalk biochar has reached adsorption equilibrium in about 8 hours, and the optimal dosage is 0.05 g; the suitable adsorption temperature of both materials are around 30˚C; the best adsorption pH are around 7. Under these conditions, the adsorption rates of the two materials have reached 70% and 80%, respectively. The adsorption of both materials can better fit the pseudo-first-order and the pseudo-second-order kinetic equation. The adsorption equilibrium of tobacco stalk powder fits Langmuir equation, while that of tobacco stalk biochar fits Langmuir equation at low Cd²⁺ concentration and Freundlich equation at high Cd²⁺ concentration. The adsorption of tobacco stalk powder could be considered as mainly physical adsorption, with that of tobacco stalk biochar a process of both physical adsorption and chemical adsorption. Therefore, both materials could be considered novel bioadsorbents for Cd²⁺ removal from aqueous solution.