Preparation of SiO₂/Attapulgite Composite Materials and Investigation of Its Adsorption Performance on Toluene in Humid Environment

The composites (SiO₂/HATP) were prepared by condensation reflux and high-temperature calcination using natural attapulgite and silica particles, and it was utilized for the adsorption of toluene. The physicochemical properties of the composite adsorbents were characterized using XRD, FT-IR, SEM, and BET techniques. The SiO₂/HATP composite material was successfully prepared, with silica particles uniformly loaded onto the surface of ATP. The adsorption performance of the composite materials for toluene was investigated using different feed ratios. The results showed that the composite materials with the mass ratio SiO₂/ATP equal to 4 exhibited the highest static adsorption capacity for toluene, reaching 236 mg/g. Additionally, dynamic adsorption performance of toluene was evaluated under conditions of 0 and 80% relative humidity, with corresponding breakthrough times of 90 and 36 min, respectively. The adsorption capacity of the composite materials for toluene was 6–8 times higher than that of pure attapulgite clay. Furthermore, the adsorption mechanisms of the composite materials were investigated through adsorption kinetics, adsorption isotherms, and adsorption thermodynamics. The results indicated that the adsorption of toluene by the composite materials followed a pseudo-first-order kinetic model and Langmuir adsorption isotherm, suggesting a spontaneous exothermic physical adsorption process at a monolayer level. Moreover, regeneration experiments were conducted, and after 5 cycles of adsorption-desorption tests, the composite materials maintained a penetration time of 85 and 30 min for toluene under conditions of 0 and 80% relative humidity, respectively, demonstrating good recyclability.