In phosphate adsorption, the interaction between MgO
and the carbon
network in Mg-biochar is an overlooked factor that contributes to
active MgO facet generation for enhancing phosphate adsorption. However,
the complex water matrix adsorption mechanism underlying the adaptability
of MgO-biochar and enhanced phosphate adsorption are not fully studied.
Herein, Mg-stirred leaf biochar (Mg-SLBC) was prepared by the Mg-stirring
modification method. Mg-SLBC possessed the highest adsorption capacity
(79.28 mg g–1) to phosphate among the adsorbents.
In addition, Mg-SLBC had a good performance for phosphate adsorption
in a complex water matrix. Phosphate adsorption by Mg-SLBC was not
affected by Cl–, NO3
–, SO4
2–, humic acid, metal ions, and
Ca2+ but was inhibited by Mg2+ and HCO3
–. For long-term adsorption, Mg-SLBC could constantly
adsorb phosphate to avoid phosphate accumulation (<2 mg L–1). Meanwhile, phosphate adsorption by Mg-SLBC was a spontaneous process
(ΔG, −6.884 kJ mol–1), which was dominated by inner-sphere complexation. Owing to high
combination between MgO and the carbon network, there were more active
MgO facets (e.g., (1 1 0) and (2 0 0)) to induce stronger unbalanced
electron distribution in Mg-SLBC. Thereby, Mg-SLBC, with high adsorption
capacity and adaptability, could effectively adsorb phosphate in a
complex water matrix.