Adsorptive Removal of Azo Dye New Coccine Using High-Performance Adsorbent-Based Polycation-Modified Nano-Alpha Alumina Particles

The azo dyes new coccine (NCC) were successfully removed through the adsorption onto PVBTAC-modified α-Al₂O₃ particles. The optimal conditions of both the surface modification by PVBTAC adsorption and the NCC adsorption were thoroughly investigated. Formerly, polycations PVBTAC were adsorbed onto the nanosized α-Al₂O₃ particles at pH 8, NaCl 100 mM, with a contact time of 2 h, and initial concentration of 1000 ppm to modify the α-Al₂O₃ surface. Latterly, the NCC adsorptive removal was conducted at pH 8, NaCl 10 mM, α-Al₂O₃ adsorbent dosage of 3 mg mL^-1, and a contact time of 45 min. Interestingly, the optimal pH of 8 potentially applies to treat real wastewater as the environmental pH range is often about 7-8. High removal efficiency and adsorption capacity of the NCC azo dyes were, respectively, found to be approximately 95% and 3.17 mg g^-1 with an initial NCC concentration of 10 ppm. The NCC adsorption on the modified α-Al₂O₃ particles was well fitted with a Freundlich model isotherm. A pseudo-second kinetic was more suitable for the NCC adsorption on the PVBTAC-modified α-Al₂O₃ surface than a pseudo-first kinetic. The NCC adsorptive removal kinetic was also affirmed by the FT-IR spectra, based especially on the changes of functional group stretch vibrations of -SO₃ ^- group in the NCC molecules and -N⁺(CH₃)₃ group in the PVBTAC molecules. The high reusability of the α-Al₂O₃ particles was proved to be higher than 50% after four generation times.