塿土胶体对氮磷钾吸附性能的尺寸效应

Size effects of Lou soil colloids on the adsorption properties of ammonium,phosphate,and potassium

为明确尺寸效应对塿土胶体吸附氮、磷、钾行为的影响过程及机理,采用高速离心法提取直径<2000、<1000、<500、<200 nm和<100 nm的塿土胶体组分,测定其粒径分布、元素含量和zeta电位,进而通过批量吸附试验研究其对铵根离子(NH_(4)^(+))、磷酸根离子(PO_(4)^(3-))和钾离子(K^(+))的吸附行为。结果表明:直径<2000 nm和<1000 nm的塿土粗胶体颗粒呈双峰分布模式,直径<500、<200 nm和<100 nm的细胶体组分呈单峰分布。随着平均直径减小,塿土胶体的全碳和有机碳含量增加。不同直径塿土胶体在高pH下的zeta电位绝对值增大,电荷密度和电荷可变性也随颗粒直径增大而增加。各直径塿土胶体对NH_(4)^(+)、PO_(4)^(3-)、K^(+)的吸附过程符合准一级动力学和Freundlich模型,吸附过程以物理扩散为主,且表现为多分子层吸附特征。不同直径塿土胶体对NH_(4)^(+)、PO_(4)^(3-)、K^(+)的的吸附性能受胶体直径大小的影响,塿土粗胶粒(<2000 nm)吸附能力最大,表明塿土胶体对养分元素的吸附差异主要受电荷密度调控。

This study was conducted to investigate the size effects of Lou soil colloids on the adsorption behaviors and mechanisms of nitrogen,phosphorus,and potassium.The colloidal fractions of Lou soil with diameters of<2000,<1000,<500,<200 nm,and<100 nm were extracted using high-speed centrifugation,and their particle size distribution,element contents,and zeta potentials were determined.The adsorption behaviors of ammonium(NH_(4)^(+)),phosphate(PO_(4)^(3-)),and potassium(K^(+))were assessed through batch adsorption experiments.The results showed that the particle size distributions of coarse soil colloids with diameters of<2000 nm and<1000 nm exhibited a bimodal distribution,whereas the fine soil colloids with diameters of<500,<200 nm,and<100 nm had a unimodal distribution.As the mean particle diameter decreased,increases in the total carbon and organic carbon contents for all soil colloidal fractions were observed.Furthermore,the absolute values of zeta potential increased at higher pH levels,accompanied by increases in charge density and charge variability with increasing particle diameter.The adsorption processes of NH_(4)^(+),PO_(4)^(3-),and K^(+)by Lou soil colloids of different diameters conformed to pseudo-first-order dynamics and the Freundlich model.This suggests that the adsorption process is characterized by physical diffusion and multi-molecular layer adsorption.Furthermore,the size of the colloids significantly influenced the adsorption behaviors of NH_(4)^(+),PO_(4)^(3-),and K^(+).Notably,the highest adsorption capacity was observed in the coarse soil colloidal particles(<2000 nm),indicating that differences in nutrient adsorption among Lou soil colloids are primarily regulated by variations in charge density.