Mechanism of targeted adsorption and specific action of bone char on ionic organic pollutants: An analysis based on differences in physicochemical properties

Adsorption is a widely recognized and effective method for treating high-concentration organic industrial wastewater. Bone char (BC) is a promising adsorbent for removing ionic organic pollutants (IOPs) from printing and dyeing wastewater due to its advantageous adsorption properties. To analyze BC's targeted adsorption and specific action mechanism on IOPs, the author first elucidated the physicochemical properties of BC under different preparation conditions. Subsequently, the study compared the targeted adsorption efficacy of BC on various types and molecular structures of IOPs. Through correlation analysis, feature importance analysis, and consideration of the properties of the target substance, the study investigated the targeted adsorption laws of BC for IOPs. Lastly, for substances with specific adsorption characteristics, range analysis, structure–activity relationship analysis, and quantitative analysis of adsorption mechanisms were employed to elucidate the action mechanism of BC. The results indicate that the differences in physicochemical properties (especially CEC and pH) caused by the inorganic mineral components of BC and the number of conjugated double bonds in the molecular structure of IOPs are key factors determining the adsorption effect. Controlling BC's pore structure and electrical conductivity based on the aggregates' conjugated double bonds and particle size can improve adsorption outcomes. The hierarchy of preparation factors influencing the adsorption performance of BC is pyrolysis temperature > particle size > pyrolysis atmosphere. The adsorption of malachite green (MG) by BC primarily involves chemical reactions, including mineral complexation effect (52.38 %), electrostatic interaction (24.76 %), π-π interaction (8.15 %), metal ion exchange (8.12 %), and physical pore filling (6.59 %). It is speculated that the primary interaction mechanism between BC and MG is through cation-π bonds formed between metal cations dissociated from the inorganic mineral components of BC and MG, facilitated by strong electrostatic interaction. The findings offer a theoretical basis for the practical utilization of BC in adsorbing IOPs.