Phosphate adsorption from phosphorus-polluted wastewater by peanut hull-derived biochar functionalized with eggshell-based calcium chloride: preparation, adsorption performance and mechanism

Phosphorus (P) recovery from wastewater, which contain large amounts of P by biochar can not only purify sewage, but promotes the reuse of P resources. The traditional enhancement of biochar's adsorption capacity through metal ion modification, such as with Ca 2+ , has shown promising results but is often hindered by high preparation costs. In this innovative work, we present a novel approach to prepare Ca-laden biochar (label as Ca-PSB) using egg-shells as a sustainable and low-cost calcium source. The biochar was prepared by peanut shell through anaerobic pyrolysis for 2 h at 400 °C under N 2 atmosphere. Three kinds of Ca-PSB were prepared according to the content of modifier (CaCl 2 ). The physiochemical properties of the Ca-PSBs were more conducive to adsorption of P. The economic cost of preparing was evaluated. The pore parameters were changed after the Ca modification. Especially, specific surface area of Ca-PSBs were increased by 4.82 %−12.05 % than raw biochar. The P adsorption capacity of Ca-PSB was 111.34 %−114.34 % higher than that of raw biochar. Ca-laden biochar showed excellent P adsorption, due to the Ca and CaO x on the Ca-PSB surface reacted with PO 4 3- through hydrogen bonds or through stable inorganic precipitation. This work provides an inexpensive strategy for preparing biochar with high efficiency for phosphorus adsorption.