Insight into the effect of surfactant modification on the versatile adsorption of titanate-based materials for cationic and anionic contaminants

The new challenges to adsorption are imposed for the diversity of contaminants in wastewater in recent years. Herein, titanate-based materials (peroxide sodium titanate, PST) were modified by three different kinds of surface charged surfactant: dodecyl dimethyl betaine (BS-PST), sodium dodecyl sulphate (SDS-PST) and dodecyltrimethyl ammonium chloride (DTAC-PST) to enhance the versatile adsorption performance for four typical contaminants including ammonia nitrogen (NH₄⁺, inorganic and cationic), phosphate (H₂PO₄⁻, inorganic and anionic), methylene blue (MB, organic and cationic) and Acid Red G (ARG, organic and anionic). The batch adsorption experiments showed that the DTAC-PST exhibited better in the removal of MB, ARG and H₂PO₄⁻ than that of other adsorbents. The theoretical maximum adsorption capacity of DTAC-PST is 49.28 mg g⁻¹ for NH₄⁺, 34.74 mg g⁻¹ for TP, 81.87 mg g⁻¹ for MB and 545.81 mg g⁻¹ for ARG. The simultaneous adsorption results showed that the concentration (10 mg L⁻¹ of NH₄⁺, 3 mg L⁻¹ of TP, 50 mg L⁻¹ of MB and 50 mg L⁻¹ of ARG) of all the four chemicals in simulated wastewater could be controlled to be below the discharge levels in China (GB, 18918–2002) by DTAC-PST at the pH of 3.0. The FT-IR spectra demonstrated that ion exchange was the main way for NH₄⁺ removal, however, electrostatic attraction and ligand exchange were the reason for MB adsorption. In addition, C–N⁺ from DTAC modification made main contribution to the excellent adsorption performance for ARG and H₂PO₄⁻. The saturated DTAC-PST could be conveniently regenerated by 0.5 mol L⁻¹ NaOH solution and maintained about 80% of adsorption capacity after five cycles.