Recovery of nitrogen and phosphorus in wastewater by red mud-modified biochar and its potential application

• Published in: The Science of the total environment 2023-02, Vol.860, p.160289, Article 160289
• Main Authors: Zhao, Zhipeng, Wang, Bing, Feng, Qianwei, Chen, Miao, Zhang, Xueyang, Zhao, Ruohan
• Format: Article
• Language: English
• Subjects: Adsorption; Ammonium; Ammonium Compounds; Biochar; Charcoal - chemistry; Kinetics; Nitrogen - chemistry; Phosphate; Phosphates - chemistry; Phosphorus - chemistry; Red mud; Site energy analysis; Wastewater; Water Pollutants, Chemical - analysis
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2022.160289

A large amount of wastewater containing nitrogen, phosphorus, and fluorine produces in the production of phosphate fertilizer. In this study, to simultaneously recover nitrogen and phosphorus from phosphorus-containing wastewater and realize the resource utilization of red mud and rape straw, red mud-modified rape straw biochar (RM/RSBC) was prepared by facile one step, and the physicochemical properties were characterized by Zeta potential, SEM-EDS, BET specific surface area (SSA), FTIR, XRD, and XPS. The adsorption performance and mechanisms of ammonium and phosphate onto RM/RSBC were explored through static, fixed-bed column adsorption, and practical wastewater experiments. The results showed that pH = 3.0 and 8.0 were favorable for the removal of phosphate and ammonium, respectively. The main adsorption mechanisms of ammonium and phosphate were the interaction between ammonium and surface functional groups and surface precipitation, respectively. The removal efficiencies of ammonium and phosphate by fixed-bed column adsorption mainly depended on the addition amount of RM/RSBC, the concentration of ammonium and phosphate, and the flow rate. The results of the germination experiment showed that adding > 0.5 wt% of RM/RSBC loaded with ammonium and phosphate promoted the growth of mung beans. This study shows that RM/RSBC can not only recover ammonium and phosphate in wastewater, but also realize the resource utilization of red mud and rape straw. [Display omitted] •Modified biochar has strong adsorption capacity for ammonium and phosphate.•Adsorption mechanism of ammonium is mainly the interaction of functional groups.•The phosphate adsorption process is mainly controlled by surface precipitation.•Fixed-bed column can effectively remove ammonium and phosphate.•Modified biochar adsorbed ammonium and phosphate promotes the growth of mung beans.