Size effects of Lou soil colloids on the adsorption properties of ammonium,phosphate,and potassium
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<2 000,<1 000,<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(NH4+),phosphate(PO43-),and potassium(K+)were assessed through batch adsorption experiments.The results showed that the particle size distributions of coarse soil colloids with diameters of<2 000 nm and<1 000 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 NH4+,PO43-,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 NH4+,PO43-,and K+.Notably,the highest adsorption capacity was observed in the coarse soil colloidal particles(<2 000 nm),indicating that differences in nutrient adsorption among Lou soil colloids are primarily regulated by variations in charge density.
soil colloidal fractions from Lou soilnanoparticlesparticle diameternutrientsadsorption
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