改性棕榈树纤维生物质炭的制备及其对溶液中Pb^(2+)的吸附性能分析

Preparation of modified palm fiber biochars and their adsorption of Pb^(2+) in solution

为提高生物质炭对重金属的吸附性能,以棕榈树纤维为原材料制备了棕榈树纤维生物质炭(NPB)、KOH活化正交优化生物质炭(PB)及负载改性纳米二氧化硅生物质炭(PBS)。分别采用红外光谱、扫描电镜等对制备的生物质炭进行表征,比较了其碘吸附值大小及对水中Pb^(2+)的吸附效果,并分析了吸附动力学和等温吸附特性。结果表明:PB、PBS较NPB增加了表面吸附位点,比表面积、总孔体积及最大吸附容量显著增加,PB吸附Pb^(2+)的过程符合准二级动力学模型,PBS吸附Pb^(2+)的过程符合准一级动力学模型,PB、PBS对Pb^(2+)的最大吸附容量分别为110.89、151.63 mg·g^(-1);通过比较Langmuir和Freundlich模型拟合方程相关参数可知,PB、PBS对Pb^(2+)的吸附过程为匀质、单双层同时进行,更加符合Langmuir方程。研究表明,PBS对Pb^(2+)的吸附性能最好(较PB吸附性能提升了1.37倍),负载改性效果显著,具有良好的应用潜力。

In order to improve the heavy metal adsorption performance of biochars,we prepared palm fiber biochar(NPB),KOH-activated orthogonal optimized biochar(PB),and loaded modified nano silica biochar(PBS)from palm fiber as a raw material.The prepared biochars were characterized by infrared spectroscopy and scanning electron microscopy,and iodine adsorption values and Pb^(2+)adsorption properties in water were compared.We also analyzed adsorption kinetics and isothermal adsorption characteristics.The results showed that compared with NPB,PB and PBS had a significantly larger number of surface adsorption sites and significantly higher specific surface area,total pore volume,and maximum adsorption capacity.The Pb^(2+)adsorption process of PB corresponded to a quasi-second-order kinetic model,whereas that of PBS was in line with a quasi-first-order kinetic model.The maximum Pb^(2+)adsorption capacities of PB and PBS were 110.89 mg·g^(-1) and 151.63 mg·g^(-1),respectively.Furthermore,a comparison of the parameters of Langmuir and Freundlich model fitting equations indicated that the adsorption process of Pb and PBS on Pb^(2+)is homogeneous,with single and double layers simultaneously,which is more consistent with the Langmuir equation.The findings of this study indicate that PBS has the best Pb^(2+)adsorption performance among the assessed biochars,which is 1.37 times higher than that PB,and has a significant load modification effect.Accordingly,the PBS biochar would have good application potential.