Enhanced photocatalytic degradation of organic pollutants using a TiO2–clay nanocomposite in a rotary photoreactor with experimental and theoretical insights

Water pollution from synthetic dyes poses a serious environmental challenge due to their persistence, toxicity, and resistance to conventional treatment methods. To address this issue, we designed a novel rotary photoreactor employing a titanium dioxide-clay (TiO₂-clay) nanocomposite immobilized with silicone adhesive for efficient photocatalytic degradation. The optimized TiO₂-clay composite (TiO₂/clay = 70:30) exhibited an enhanced BET surface area of 65.35 m²/g compared to 52.12 m²/g for pure TiO₂. The point of zero charge (PZC) was determined to be pH 5.8, favoring adsorption of the cationic BR46 dye under near-neutral pH conditions. Under optimal operating parameters-20 mg/L initial dye concentration, 5.5 rpm rotation speed, and 90 min of UV exposure-the system achieved 98% dye removal and 92% total organic carbon (TOC) reduction. Kinetic analysis confirmed a pseudo-first-order model (R² > 0.97) with an apparent rate constant of 0.0158 min^-1. Radical scavenger experiments identified hydroxyl radicals (OH^·) as the primary oxidative species, consistent with Density Functional Theory (DFT) predictions. GC-MS analysis further verified the degradation of BR46 into non-toxic intermediates. The TiO₂-clay nanocomposite demonstrated excellent stability and reusability, maintaining > 90% efficiency after six cycles. These findings underline the potential of the TiO₂-clay rotary photoreactor as a robust and sustainable technology for advanced wastewater treatment.