[Preparation of Narrow Pore Diameter Phosphorus Containing Cotton Stalk Carbon and Its Adsorption Mechanism for Tetracycline].

Using cotton stalk as biomass raw material and phosphoric acid as a modifier, narrow pore distribution phosphorus-containing cotton stalk biochar (CSP) with a high surface area (1916 m·g) and pore volume (1.3982 mL·g) was prepared through one-step carbonization, and the adsorption characteristics and mechanisms for tetracycline (TC) were investigated. The results showed that the TC adsorption capacity of CSP was up to 669 mg·g, which was 43.6 times that of unmodified cotton stalk carbon. FTIR, XPS, and isothermal adsorption studies showed that the high adsorption capacity of CSP for TC resulted from the joint action of complexation, hydrogen bonding, pore filling, and π-π dispersion forces, and the highly active phosphate ester group (P-O-C) endowed by phosphoric acid modification greatly enhanced the chemical interaction with TC molecules, which was the key factor for the significant increase in adsorption capacity. Isotherm and thermodynamic study further confirmed that chemical adsorption played a major role in the adsorption process, the adsorption process was spontaneous and endothermic, and the material had good regeneration performance. This study provides theoretical guidance for the preparation of modified biomass carbon with high adsorption performance to remove tetracycline antibiotic pollution.