High porosity biochar and its treatment of phosphate in wastewater

Biochar is a product of pyrolysis of biomass under anoxic conditions, but the common biochar has a small specific surface area, underdeveloped pore structure, few surface active groups and poor removal effect. In this paper, biochar was prepared from sorghum (GC) and grapefruit peel (YC) by surface treatment using four substances to obtain biochar, where the prepared sorghum/KOH (GC-KH) and grapefruit peel/KOH (YC-K) powders had obvious surface porosity, confirming the feasibility of the process. With a specific surface area of 2,096.05 m²/g and an average pore size of 4.12 nm, GC-KH is rich in oxygen-containing functional groups on its surface, providing a good structural space and active sites for adsorption. The effect of dosing volume, initial pH, contact time and initial concentration on phosphate adsorption was investigated in batch experiments to assess the ionic strength. The isotherm results show that the Langmuir model can describe the equilibrium data well, and the maximum adsorption capacity of GC-KH for phosphate at pH 7 is 74.73 mg/g, which has significant advantages such as rapid response and provides an innovative pathway for efficient removal of phosphate from wastewater.