稻草秸秆生物质炭对重金属Cd2+的吸附性能研究

以稻草秸秆为原料，分别通过水热炭化和热解炭化制备生物质炭（分别记为RS-HC和RS-BC），并采用不同的洗涤剂（蒸馏水、乙醇、四氢呋喃）对水热炭进行洗涤，分别记为RS-HC₁、RS-HC₂和RS-HC₃.探究了吸附时间、Cd²⁺初始浓度和溶液pH值对4种生物质炭吸附性能的影响.结果表明：4种生物质炭对Cd²⁺的吸附均符合准二级动力学方程，表明吸附过程主要受化学吸附速率控制；RS-HC对不同浓度下Cd²⁺的吸附符合Langmuir等温吸附模型，但对于RS-BC，Langmuir方程和Freundlich方程的拟合效果都比较好（R²>0.93），说明水热炭对Cd²⁺的吸附多为单分子层吸附，而Cd²⁺在热解炭上的吸附则是多分子层吸附和单分子层吸附共同作用的结果；4种生物质炭的平衡吸附容量排序为：RS-BC > RS-HC₃ > RS-HC₂ > RS-HC₁，RS-HC₃和RS-HC₂的平衡吸附量分别是RS-HC₁的3.32和1.7倍；随着pH（3~8）的增加，生物质炭对Cd²⁺的吸附量逐渐增加，在pH=4时，RS-BC的吸附量是RS-HC₃的5.57倍.

Study on the adsorption performance of rice straw biomass charcoal to heavy metal Cd2+

In this study, rice straw biochar (RS-BC) and rice straw hydrochar (RS-HC) were derived from rice straw through pyrolysis and hydrothermal carbonization, respectively, the RS-HC were washed with different detergents (distilled water, ethanol and tetrahydrofuran), and labeled as RS-HC₁, RS-HC₂ and RS-HC₃. The effects of adsorption time, initial Cd²⁺ concentration and solution pH in sorption experiments were investigated. The results suggested that the adsorption kinetic results of RS-BC and RS-HC to Cd²⁺ followed the pseudo-second-order kinetics, indicating that the adsorption process is mainly controlled by the chemical adsorption rate. Moreover, The adsorption of Cd²⁺ at different concentrations of RS-HC was suitable to be described by Langmuir isothermal equation, while the adsorption of Cd²⁺ at different concentrations of RS-BC was well simulated by both Langmuir and Freundlich adsorption isothermal equation (R²>0.93), indicating that the adsorption of Cd²⁺ on RS-HC was similar to that of surface monolayer adsorption, but the adsorption process of Cd²⁺ on RS-BC showed monolayer and multi-molecular layer adsorption mechanism. The order of the equilibrium adsorption capacity was: RS-BC > RS-HC₃ > RS-HC₂ > RS-HC₁, and the equilibrium adsorption capacity of RS-HC₃ and RS-HC₂ was 3.32 and 1.7 times of RS-HC₁ respectively. With the increase of pH (3~8), the adsorption capacity of Cd²⁺ to biomass charcoal gradually increased. When pH was equal to 4, the adsorption capacity of RS-BC was 5.57 times of RS-HC₃.