Impact of mineral components in cow manure biochars on the adsorption and competitive adsorption of oxytetracycline and carbaryl

Abstract

In recent years, biochar has been well-documented in the literature as a promising soil amendment for the sorption and immobilization of organic contaminants in contaminated soils via its organic functional groups. In this study, original and demineralized cow manure biochars were applied with the aim to evaluate the impact of their mineral component on adsorption and competitive adsorption of oxytetracycline and carbaryl. Adsorption increased greatly for oxytetracycline but decreased slightly for carbaryl after demineralization. Mineral components significantly enhanced overall adsorption of carbaryl but slightly inhibited that of oxytetracycline to biochars, because the dominant sorption mechanisms of oxytetracycline and carbaryl on demineralized biochars were established as pore-filling effects and specific-site sorption, respectively. Competitive adsorption was observed in the binary-solute sorption system, where oxytetracycline outcompeted carbaryl on original biochars, however, carbaryl showed a greater competitive adsorption to oxytetracycline on demineralized biochars. Furthermore, demineralization treatment weakened the competition strength of oxytetracycline to carbaryl but enhanced that of carbaryl to oxytetracycline. This work demonstrated that the demineralization treatment altered the physicochemical properties of biochars and the dominant sorption mechanisms of oxytetracycline and carbaryl, leading to their different changes on competition strength. The results are useful for the application of biochars in the remediation of combined pollution in agricultural soils.