Solvent-Free Synthesis of MgO-Modified Biochars for Phosphorus Removal from Wastewater

Adsorption is an efficient technology for removing phosphorus from wastewater to control eutrophication. In this work, MgO-modified biochars were synthesized by a solvent-free ball milling method and used to remove phosphorus. The MgO-modified biochars had specific surface areas 20.50-212.65 m² g^-1 and pore volume 0.024-0.567 cm³ g^-1. The as-prepared 2MgO/BC-450-0.5 had phosphorus adsorption capacities of 171.54 mg g^-1 at 25 °C and could remove 100% of phosphorus from livestock wastewater containing 39.51 mg L^-1 phosphorus. The kinetic and isotherms studied show that the pseudo-second-order model (R² = 0.999) and Langmuir models (R² = 0.982) could describe the adoption process well. The thermodynamic analysis indicated that the adsorption of phosphorus on the MgO-modified biochars adsorbent was spontaneous and endothermic. The effect of pH, FTIR spectra and XPS spectra studies indicated that the phosphorus adsorption includes a protonation process, electrostatic attraction and precipitation process. This study provides a new strategy for biochar modification via a facile mechanochemical method.