Sustainable Chemistry: Solubilization of Phosphorus from Insoluble Phosphate Material Hydroxyapatite with Ozonized Biochar

Abstract

A large increase in phosphorus (P) solubilization from hydroxyapatite using ozonized biochar has been experimentally demonstrated here for the first time. Briefly, incubation of insoluble phosphate material hydroxyapatite with wet-ozonized biochar, including its filtrate liquid, for 2 days, resulted in a much higher concentration of solubilized phosphate (569.9 mg/L) than that (0.145 mg/L) of the control in which hydroxyapatite was incubated with the nonozonized biochar and its filtrate. The associated calcium solubilization pattern was also observed in the experiment. 31Phosphorus NMR analysis confirmed the solubilized phosphorus to be mostly in the form of HPO42–. Excitation emission matrix spectroscopy showed the prevalence of humic-like substances in ozonized biochar filtrate, which resulted in stronger P solubilization. This study indicated that the P solubilization may be accomplished through at least one of the following molecular mechanisms: (a) protonic effect, (b) cation exchange, and (c) anion exchange. This green chemistry with ozonized biochar may lead to a new approach to unlock P from “insoluble” phosphate mineral phases.