Poly 2-chloroaniline/TiO2 quantum dots for solar and photocatalytic processes of Congo Red dye and industrial wastewater

This study investigates the synthesis and characterization of a poly 2-chloroaniline (PCl-AN)/TiO2 quantum dots (TQD) composite for photocatalytic degradation of Congo Red dye and industrial wastewater treatment. PCl-AN was synthesized via chemical oxidative polymerization of 2-chloroaniline (80 mmol) using ammonium persulfate (80 mmol) as an oxidant. TQD was prepared by a hydrothermal method using 18 mL of titanium tetrachloride and 45 mL of methanol at 80 °C for 24 h. The (PCl-AN)/TQD composite with 8 wt% TQD was fabricated by in-situ polymerization. Characterization techniques including XRD, FTIR, UV–vis, TGA, EDX, and TEM were employed. XRD revealed PCl-AN particle size of 29–40 nm and TQD sizes of 3.1–4.8 nm. TEM showed core-shell (PCl-AN)/TQD structures of 26–30 nm. The band gaps were 3.33 eV (PCl-AN), 2.17 eV (TQD), and 2.30 eV ((PCl-AN)/TQD). Photocatalytic tests using a 150 W xenon lamp (100 mW/cm2, 200–1100 nm) showed (PCl-AN)/TQD achieved 93.56 % Congo Red degradation in 120 mins, outperforming PCl-AN (51.69 %) and TQD (80.96 %). After 5 recycles, degradation rates decreased by 34.32 % (PCl-AN), 18.57 % (TQD), and 26.75 % ((PCl-AN)/TQD). For industrial wastewater with initial COD 5230–7150 ppm, (PCl-AN)/TQD reduced COD to 745–1230 ppm, meeting the <1000 ppm limit. The (PCl-AN)/TQD composite demonstrates promising photocatalytic performance for environmental remediation.