改性棕榈树纤维生物质炭的制备及其对溶液中Pb2+的吸附性能分析

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。

Preparation of modified palm fiber biochars and their adsorption of Pb2+ in solution

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 Pb²⁺ 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 Pb²⁺ 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 Pb²⁺ 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 Pb²⁺ 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 Pb²⁺ 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.