Waste baijiu distillers’ grains-derived biochar for efficient removal of organophosphate esters from water through adsorption

Waste baijiu distillers’ grains (BDGs) are one kind of low-value-added biomass originated from Chinese baijiu industry. Considering the large quantity and abundance in carbon element, conversion of waste BDGs to biochar as functional material is of great potential for the sustainable development of baijiu industry. In this study, with the assistance of potassium acetate as activation agent, waste BDGs were converted to highly porous biochar materials through a pyrolysis procedure. Taking the advantages of large specific surface area, well-developed micro- and mesopores, partially graphitized carbon with thin layer structure and abundant surface functional groups, the waste BDGs-derived biochar performed well for the removal of typical organophosphate esters (OPEs) in water, e.g., a maximum adsorption capacity for triphenyl phosphate (TPhP) reached 752.95 mg g −1 over biochar sample of BC 1:3–900 . Although the adsorption equilibrium needed up to 10 h to reach, over 50 % effective adsorption was completed in the first 30 min. The adsorption behavior of TPhP on biochar was identified as an exothermic and mono-layer adsorption process, including both fast surface adsorption and relatively slow intra-particle diffusion steps. Solution pH did not affect TPhP adsorption much, but environmental temperature showed great influence on TPhP adsorption capacity. The developed biochar of BC 1:3–900 was still effective for TPhP removal from natural water bodies. Further studies indicated that π-π electron-donor-acceptor (EDA) interaction, hydrogen bonding, σ bonding as well as pore filling effect were the main adsorption mechanisms, contributing to the good adsorption performance of biochar. Besides of aromatic OPEs of TPhP and tricresyl phosphate (TCP), the optimized biochar material was also efficient in removing alkyl and halogenated OPEs, i.e., tributyl phosphate (TBP) and tris(2-chloroethyl) phosphate (TCEP). The facile preparation procedure of biochar material and their good adsorption performance bring a possible alternative for the treatment of OPEs-containing water/wastewater.