The Adsorption of Zn(II) By Acidic Soils Following Incorporation of Biochars from Swine Manure and Rice Straw.

This study was to compare the differences and similarities in the mechanisms of swine manure biochar and rape straw biochar incorporation at the rate of 3% on Zn(II) adsorption by four acidic soils (pH from 4.61 to 5.91). The Dual-mode model (DMM) was suitable for the adsorption isotherms of the four soils amended with biochars, compared with the Distributed reactivity model (DRM). Swine manure biochar had the greater effects on the increases in Zn(II) adsorption by soils than rape straw biochar. Both non-electrostatic and electrostatic adsorption mechanisms were quantified in the four acidic soils. The negative surface charge of biochar was responsible for the electrostatic adsorption, and the functional oxygen groups and minerals were responsible for non-electrostatic adsorption. The swine manure biochar made more contribution to non-electrostatic adsorption than rape straw biochar, which was attributed to the higher content of mineral components (PO₄^3- and SiO₄^2-).