Lanthanum and magnesium co-doping biochar for adsorption of phosphorus from wastewater: Kinetics, isotherms, and mechanism

High concentration of phosphorus is one of the main factors leading to eutrophication of water. Adsorption method is widely used to remove phosphorus from sewage. In this study, lanthanum-magnesium modified sludge and corn stalk biochar were prepared by a one-step hydrothermal method, and the adsorption effect and mechanism of this biochar on phosphorus in wastewater were investigated. The specific surface area of the biochar was obtained to be 8.462 m ² /g, and the pore size was17.260 nm. The kinetic study showed that the adsorption of phosphorus on the modified biochar was in accordance with the pseudo-second-order kinetic model and the Langmuir isotherm model, which indicated that the adsorption process of phosphorus on the biochar was mainly chemical adsorption and monolayer adsorption, and the maximum theoretical adsorption amount was 112.6mg/g. The adsorption mechanisms mainly involved surface precipitation, hydrogen bonding, electrostatic effect, ligand exchange and intraparticle diffusion.