Adsorption of Bisphenol A and 2,6-Dichlorophenol in Water Using Magnetic Phosphogypsum Composite Materials

Phenolic pollutants in water bodies pose a huge threat to human health and environmental safety. In this paper, a hydrophobicity-enhanced magnetic C-SiO2/MPG composite was prepared by a two-step method to remove bisphenol A (BPA)and 2,6-dichlorophenol (2,6-DCP), typical phenolic trace pollutants in livestock wastewater and natural water bodies. The results of pH gradient experiments showed that C-SiO2/MPG showed a stable removal effect on BPA in the pH range of 2–11. The adsorption of 2,6-DCP by C-SiO2/MPG peaked at pH = 2, while the adsorption of 2,6-DCP by C-SiO2/MPG was severely inhibited under alkaline conditions. The PSO kinetic model and the Langmuir isotherm model can better describe the adsorption process of BPA and 2,6-DCP on C-SiO2/MPG, indicating that the monolayer chemical adsorption has a rate-controlling step. With the Langmuir equation fitting, the maximum adsorption capacity of C-SiO2/MPG for BPA and 2,6-DCP at 298 K was calculated to be 561.79 mg/g and 531.91 mg/g, respectively. The results of adsorption thermodynamics indicated that the adsorption of BPA and 2,6-DCP on C-SiO2/MPG was spontaneous, accompanied by a process of entropy decrease. C-SiO2/MPG showed good environmental resistance and repeated use stability for BPA and 2,6-DCP in electrolyte ion interference, actual water samples and cycle experiments. Mechanism analysis showed that the adsorption of BPA and 2,6-DCP on C-SiO2/MPG was mainly controlled by hydrogen bonding and hydrophobic interactions. This study designed an efficient adsorbent for phenolic pollutants that can be used in actual wastewater and broadened the resource utilization of industrial waste phosphogypsm.