Adsorption performance of red mud magnetic composite material modified by Spirit-based distillers' grains for low-concentration phosphorus in water

Background Research on phosphate removal has focused on high-phosphorus wastewater, which has difficulty meeting the discharge standard through one-step processing. Herein, the rich carbon source of spirit-based distillers' grains was used to reduce and roast red mud (RM) to prepare magnetic adsorption material (MRM), aiming to improve the adsorption performance of RM on low-concentration phosphorus in water and to facilitate the separation and recovery of the adsorbent. Results The characterization results of MRM indicated that the high-temperature decomposition of macromolecular minerals in RM exposed more active sites of metal ions. Compared with unmodified samples, the specific surface area and saturation magnetization of MRM increased by 3.64 and 9.21 times, respectively;this provided more active sites for phosphorus adsorption by MRM and gave the material magnetic separation ability. The results of adsorption experiments showed that MRM had a wide applicable pH range and good selectivity for phosphorus adsorption, and the phosphorus removal rate was 4.97 times that of RM. The adsorption process of phosphorus by MRM was more in line with the Langmuir isotherm adsorption model and the quasi-second-order kinetic equation, as it was a process of spontaneous endothermic entropy increase. The phosphorus removal mechanism included chemical precipitation, coordination exchange, physical adsorption, and electrostatic attraction. Conclusion MRM has good adsorption performance for low concentrations of phosphorus in water and provides an effective method for the resource utilization of red mud and spirit-based distillers' grains. (c) 2022 Society of Chemical Industry (SCI).