Synthesis of hydrothermal carbonation carbon with tunable photocatalytic performance for trimethoprim degradation using an ethanol-water co-solvent strategy: Influence of ethanol concentration

Hydrothermal carbonation carbon (HTCC) is increasingly acknowledged as a promising photocatalytic material for degrading antibiotics in water due to its green and cost-effective properties. While ethanol and water are prevalent solvents in the preparation of HTCC, research examining the influence of solvent combinations on the photocatalytic efficacy of HTCC is lacking. The influence of various ethanol-water co-solvent preparation ratios (0, 20, 40, 60, 80, and 100 wt% ethanol concentration in the co-solvent) on the photocatalytic degradation activity of trimethoprim (TMP) by HTCC was examined in this study. The results indicated that altering ethanol solvent preparation concentrations modulates the morphological characteristics, surface functional groups, and photochemical attributes of co-solvent HTCC materials. HTCC prepared using an 80 wt% ethanol solvent concentration demonstrated the most efficient TMP photocatalytic degradation (>90%). The TMP degradation kinetic constants of 80 wt% ethanol concentration co-solvent HTCC were 3.29 and 1.51 times greater compared to those of HTCC prepared using only water or ethanol as solvents, respectively. center dot O-2(-) predominantly served as the key reactive oxygen species in TMP photocatalytic decomposition by 80 wt% ethanol concentration co-solvent HTCC, with its generation mechanism linked to the intrinsic furan donor-acceptor (D-A) conjugated structure of HTCC. An increase in ethanol solvent preparation concentration promotes the formation of more furan units, increased coupling of donor-acceptor (D-A) conjugation, a lower D-A ratio, and enhanced generation of shortchain aliphatics in HTCC, which then directly impacts its electron transfer capability, bandgap structure, light absorption capacity, and photocatalytic degradation efficiency. This work provides fresh strategies for the preparation and photocatalytic performance modulation of water treatment photocatalysts based on HTCC.