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. 31 Phosphorus NMR analysis confirmed the solubilized phosphorus to be mostly in the form of HPO 4 2− . 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.

Sustainable Green Chemistry: Water-Soluble Ozonized Biochar Molecules To Unlock Phosphorus from Insoluble Phosphate Materials

“…The protonic effect is likely a major driving force in solubilizing HA. 10,24 The RBC 90D-F (Figure S4) is slightly less acidic than the P400 90W-F (Figure S5) at any given DOC concentration.…”

“…The ozone treatment may cause the breaking of those molecular fragments into smaller acidic compounds that are more water-soluble; this may explain the larger amount of DOC released from the ozonized biochar. While some of the DOC from the ozonized biochar filtrate may belong to the humic-like groups, 10 the majority may be in the form of smaller organic acids. The ozone treatment time used here was 90 min.…”

“…Our recent study 10 showed that the ozonized biochar contained some substances that were shown to be resembling humic-like materials. 10 In the literature, several technologies were developed to generate humic-like substances. A group of scientists showed the generation of humic-like materials from coal following oxidation.…”

“…Preparation of Pine 400 Biochar. Pinewood-derived biochar was made using a similar approach to that we previously reported 10 with a slight change. Here, the pine biomass was chopped into 5 mm diameter pieces.…”

“…A fraction of the water-soluble materials extracted from the biochar showed the presence of some biochar molecular fragments previously identified as humic-like molecules. 10 Therefore, a similar protocol used to measure carboxyl groups in humic acid was used in this study. The CEC of the soluble biochar molecular fragments in the filtrates was quantified by measuring the carboxyl groups contained in the 10 mL filtrate, using a modified approach as performed by Khil'ko et al (2011) 16 with a potentiometric titration of the filtrates.…”