Basic magnesium sulfate@TiO2 composite for efficient adsorption and photocatalytic degradation of 4-dodecylmorpholine in brine

More than 70% of the potash fertilizer globally is produced by the froth flotation process, in which 4-dodecylmorpholine (DMP) serves as a reverse flotation agent. As the potash fertilizer production rapidly rises, the increased DMP levels in discharged brine pose a threat to the production of high-value chemicals. In this paper, composite particles of basic magnesium sulfate@TiO₂ (BMS@TiO₂) were prepared using a simple and mild loading method. These particles were utilized for the adsorption and photocatalytic degradation of DMP in brine. Compared with normal powdered materials, the granular BMS@TiO₂ in this study can be easily separated from liquid, and the degradation intermediates will not enter the brine without causing secondary pollution. BMS@TiO₂ consists of 5·1·7 phase (5Mg(OH)₂·MgSO₄·7H₂O) whisker clusters embedding 2.3% TiO₂. The adsorption equilibrium of DMP on BMS@TiO₂ particles was achieved through hydrogen bonding and pore interception with the adsorption capacity of approximately 5 mg g⁻¹ after 6 h. The photodegradation efficiency of DMP adsorbed on BMS@TiO₂ reached about 92% within 16 h, which is compared with that of pure TiO₂ nanoparticles. Additionally, excellent stability and recyclability of BMS@TiO₂ were also observed in five cycle tests of adsorption and photocatalytic degradation of DMP, and the possible photocatalytic degradation pathways and mechanism of DMP are proposed following molecular electrostatic potential analysis. This work provides a sustainable and environmentally friendly approach for eliminating organic micropollutants from water environments.