Design and characterization of a biomass template/SnO₂ nanocomposite for enhanced adsorption of 2,4-dichlorophenol

2,4-Dichlorophenol (2,4-DCP) is a hazardous chlorinated organic chemical derived from phenol that exerts serious effects on living organisms. In the present study, SnO₂ templated with grapefruit peel carbon as a nanocomposite (SnO₂@GPC) was designed via ball-milling, and its mechanism of 2,4-DCP adsorption in aqueous solution was determined. Batch adsorption experiments revealed that the maximum adsorption efficiency of SnO₂@GPC occurred at 6.0 pH, 3 mg L⁻¹ initial adsorbate concentration, 2 h contact time, and 293 K temperature. The SnO₂@GPC nanocomposite and its non-tin-bearing counterpart, grapefruit derived char (@GPC), showed maximum adsorption capacities (Q_L) of 45.95 and 22.09 mg g⁻¹ and partition coefficients of 41.77 and 10.83 mg g⁻¹ μM⁻¹, respectively. The adsorption of 2,4-DCP was best described by the Redlich−Peterson model followed by the Langmuir model with high correlation coefficients (R² ≥ 0.96), and the adsorption kinetic data best fitted the pseudo-second-order model (R² ≥ 0.98). The thermodynamic parameters indicated that the reaction was spontaneous, exothermic, and involved high affinity between SnO₂@GPC and 2,4-DCP. The high desorption efficiency obtained (>80%) demonstrated the recyclability of the adsorbent. The enhanced Q_L of SnO₂@GPC was due to the effective combination of GPC and SnO₂. A thin porous layer of GPC on SnO₂ nanoparticles provided effective channels, a large surface area, and an abundance of active sites for 2,4-DCP adsorption. Thus, the SnO₂@GPC nanocomposite could potentially be used as a low-cost adsorbent to remove 2,4-DCP from water.