Evaluation of performance and stability of a gel-type polymer sorbent for recovery of phosphate from waste streams

Phosphorus (P) fertilizer is an essential component of our food system with the majority of all mined P rock processed to make mineral fertilizers. Globally however P rock stocks are declining─both in quality and quantity─with poor P management creating a linear economic system where P is mined, globally redistributed into products and eventually discharged into the environment leading to eutrophication. To enable establishment of a circular P economy, whereby P can be recovered from waste for its industrial reuse, requires the development of effective P recovery technologies. Adsorption via anion exchange is a promising technology for P recovery from waste streams; however, in many cases, the regeneration of the sorbent used (to allow for its subsequent reuse) has not been extensively investigated. We now describe a gel-type anion exchange polymer composed of vinyl benzyl chloride, hydroxypropyl methacrylate, and ethylene glycol dimethacrylate synthesized via suspension polymerization. The obtained material was modified to introduce a quaternary ammonium functionality, characterized, and tested for phosphate capture, in the presence of competing anions and from wastewater samples. Fixed-bed experiments were conducted using monobasic phosphate as adsorbate to test polymer performance, and its stability upon repeated adsorption/desorption cycles was investigated by solid-state NMR, revealing that no degradation or loss of P binding performance across 50 regeneration cycles. Excellent polymer performance in the recovery of P from wastewater was also demonstrated.