Adsorption characteristics and molecular mechanisms of ionic organic pollutants on bone char

Adsorption is considered to be one of the most promising methods for treating organic wastewater. This paper focuses on the adsorption characteristics and molecular mechanisms of ionic organic pollutants (IOPs) on bone char (BC). It was found that BC had excellent adsorption performances for cationic organic pollutants with large molecular, especially malachite green (MG, triphenylmethane): the maximum adsorption capacity is 10.3–1.5 and 50.6–6.9 times higher than that of straw biochar (SBC) and activated carbon (AC), respectively, and 30 and 60 times higher than that of anionic and amphoteric organic pollutants. The adsorption mechanism of IOPs on BC was analyzed at the macroscopic level by comparing the differences in the physicochemical properties of the adsorbents and the changes before and after adsorption. Then, statistical physical modeling was used to investigate the mechanism of interaction between BC and IOPs at the molecular scale (mesoscopic level). The results showed that the rich mesoporous structure and ionic polarity sites of BC play an essential role in the adsorption of MG. PO43-, CO32–, and OH– are the effective sites for adsorption of BC, with the density of sites significantly higher than that of SBC and AC. It can be surmised that BC adsorbs the IOPs through pore filling and electrostatic interactions. Techno-economic analysis showed that the adsorption cost of BC could be reduced by 370.89% to 810.72% compared with modified biochar and commercial AC, indicating that BC has wide application prospects and market competitiveness. The results of this study can provide vital theoretical support for the practical application of BC.