Enhanced Phosphate Adsorption by Mg-Stirred Leaf Biochar in a Complex Water Matrix via Active MgO Facet Exposure
Haoyu Luo, Yi Wan, Yuhao Cai, Zhi Dang, Hua Yin
Abstract
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–, SO42–, 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.