In this work, a tomato biochar composite modified with cetyltrimethylammonium bromide (CTAB@TBC) was successfully synthesized using an ethanol solution method. It was comprehensively characterized to evaluate its morphology (SEM), crystal structure (XRD), chemical bonding (FT-IR and Raman spectroscopy), surface area (BET analysis), and thermal stability (TGA). The adsorption performance of the composite for xylenol orange (XO) was subsequently evaluated in detail. The findings revealed that CTAB@TBC exhibited a maximum adsorption capacity of 150.59 mg/g for XO. Kinetic analysis indicated that the adsorption process conformed to a pseudo-second-order model, implying that chemisorption was the step limiting the rate. The Langmuir model accurately described the adsorption isotherm data, suggesting monolayer adsorption on a uniform surface. Thermodynamic evaluation further revealed a negative Gibbs free energy (ΔG) change, confirming the spontaneity of the adsorption process. In summary, the results suggest that CTAB@TBC is a highly effective adsorbent for eliminating dyes from wastewater and offers considerable promise for treating industrial effluents.

In this study, a MIL-100(Fe)@KTBC composite was successfully fabricated via an in situ hydrothermal method using KOH-activated tomato-biochar-derived carbon (KTBC) as the support, and was applied for the efficient adsorptive removal of xylenol orange (XO) from water. Characterization by SEM, XRD, FTIR, XPS, and BET confirmed that MIL-100(Fe) was successfully loaded onto the KTBC surface, and the resulting composite exhibited a well-developed porous structure, abundant functional groups, and good thermal stability. Adsorption experiments showed that MIL-100(Fe)_0.5@KTBC delivered the optimal performance, with a maximum adsorption capacity of 246.12 mg/g; high removal efficiency was achieved at pH 4.0 and an adsorbent dosage of 0.4 g/L. The adsorption process followed pseudo-second-order kinetics and the Langmuir isotherm model, indicating spontaneous, endothermic, monolayer adsorption dominated by chemisorption. The composite also demonstrated strong resistance to interfering ions and favorable reusability. This work provides a scientific basis for the development of efficient and stable biochar-based MOF composites for the treatment of printing and dyeing wastewater.