ABSTRACT
Calcium-containing biochar ï¼ES-BCï¼ was prepared by pyrolyzing eggshell and kitchen wastesï¼ and the ES-BC composite was used to remove phosphate ï¼marked as ES-BC/Pï¼. Based on the high affinity of phosphate and carbonate to leadï¼ the ES-BC/P was then used to remove lead from the water. The results showed thatï¼ in the appropriate dosageï¼ ES-BC/P could remove lead efficiently at different initial concentrations ï¼1-100 mg·L-1ï¼ï¼ and the removal efficiency could reach to 99%. Meanwhileï¼ the release of phosphorus could be ignored after the reaction. As ES-BC/P was alkalineï¼ and the lead-containing solution was weakly acidicï¼ the addition of ES-BC/P could adjust the pH of the system automatically. The reaction kinetics and isotherm experiments showed that the lead removal by ES-BC/P was mainly monolayer chemisorption with a maximum adsorption capacity of 493.12 mg·g-1 ï¼318 Kï¼. The characterization results showed that lead was mainly removed through the ion exchanges of Pb2+ in the solution with Ca2+ in ES-BC/P. Thenï¼ the Pb2+ combined with CO32- and PO42- to form many precipitatesï¼ including Pb5ï¼PO4ï¼3OHï¼ Pb10ï¼PO4ï¼6ï¼OHï¼2ï¼ PbCO3ï¼ and Pb3ï¼CO3ï¼2ï¼OHï¼2. In summaryï¼ the ES-BC/P material could achieve the efficient removal of lead from the waterï¼ thereby realizing the resource utilization of the wastes.
