Application and functionalization of toxic waste sludge-derived biochar for efficient phosphate separation from aqueous media: Toxicity diminution, robust adsorption, and inner mechanism

Abstract

Phosphorus control and the disposal of municipal solid waste have drawn increasing concerns. Herein, we reported the reutilization and functionalization of highly toxic waste sludge derived from landfill leachate treatment process for biochar preparation and therefore phosphate elimination from aqueous media. Toxicity analysis confirmed largely declined heavy metal leaching and diminished ecological risks during biochar pyrolysis, providing a feasible option for the disposal and reutilization of toxic waste. Pre-loading of lanthanum rendered fabricated biochar with robust phosphate adsorption capacity, with optimized composite achieving maximum capacity of ∼94.4 mg P/g at pH 6. Effects of environmental factors, especially co-existing species (anions, cations and dissolved organic matters), were systematically evaluated combining experimental results and characterization analysis. Thereafter, adsorption behaviors of synthesized samples including kinetic, isotherm and thermodynamics were comprehensively explored. In virtue of characterization analysis, physicochemical properties of different composites and phosphate separation mechanism that involved electrostatic attraction and inner-sphere complexation were fully probed. Overall work investigated the feasibility of toxicity reduction via pyrolysis, phosphate uptake performance and inner mechanism, therefore highlighting the potential of waste reutilization for environmental remediation.