巯基改性稻壳炭对水中Cd2+的吸附特性

Characteristics of Cd2+ Adsorption From Water by Sulfhydryl Group Modified Rice Hull Biochar

利用(3-巯丙基)三甲氧基硅烷改性稻壳炭,并对改性前后的稻壳炭进行Zeta电位、扫描电镜元素分析(SEM-EDS)、比表面积及孔径分析(BET)和傅里叶变换红外光谱(FTIR)表征;探讨溶液pH值、反应温度、反应时间和固液比等影响因素对改性前后稻壳炭吸附Cd^2+的影响及解吸情况;分析改性前后稻壳炭对水中Cd^2+的吸附动力学和热力学试验。结果表明,改性后稻壳炭表面孔隙、负电荷增多,结构更清晰;不同影响因素下巯基改性后的稻壳炭对Cd^2+的吸附效果均明显优于改性前。在最佳条件下,改性后稻壳炭最大吸附量(14.95 mg·g^-1)比未改性稻壳炭(8.50 mg·g^-1)提高76%,解吸率下降23%~53%,整个吸附过程符合准二级动力学(R2>0.99)及Langmuir等温方程模型(R2>0.99),吸附是以单分子层吸附为主的自发吸热过程。

The rice hull biochar(RHB) was modified by(3-mercaptopropyl) trimethoxysilane, and analyzed for the Zeta potential, SEM-EDS, BET and FTIR before and after the modification. Effects of solution pH, reaction temperature and time, solid-liquid ratio and other factors on the adsorption of Cd^2+ on the rice hull biochar before and after modification and the desorption were investigated. The adsorption kinetics and thermodynamics of modified rice hull biochar(MRHB) on Cd^2+ in water were studied. Results show that both the MRHB surface pores and the negative charge increased, the structure was clearer, and the sulfhydryl group was successfully introduced. Under different influencing factors, the adsorption effect of sulphide-modified RHB on Cd^2+ was excellent. Under the best condition, the maximum MRHB(14.95 mg·g^-1) was 76% higher than non-modified RHB(8.50 mg·g^-1) and the desorption rate reduced by 23%-53%. The whole adsorption process was more in line with the quasi-secondary kinetics(R2>0.99) and the Langmuir isotherm equation model(R2>0.99). The adsorption was a spontaneous endothermic process dominated by mono-layer adsorption.