Development and evaluation of polymer sorbents for Phosphorus recovery from waste streams

Abstract

Phosphorus (P) is a crucial element in fertilisers, mainly produced from non-renewable phosphate rocks. Due to the critical availability of this resource, methods for efficient P reuse have been developed and proposed in the past years. Technologies for P recovery can potentially drive the change from P removal to prevent pollution to P recovery. However, most of these rely on precipitation of phosphorus as insoluble salts, after adding chemicals. Adsorption has raised much interest in P recovery, as it is easy to operate and allows P recovery in a directly usable form. However, most sorbents on the market are based on iron and don’t have high capacity, but high selectivity, towards P, being thus used as final polishing materials for P removal or recovery. Polymeric sorbents have been proven to have a higher capacity towards P and mechanical stability but have never been extensively investigated for P recovery.

In this thesis, polymeric materials for P capture and recovery are investigated. Firstly, a polymer library was developed to screen different monomers and cross-linkers, and the best polymer candidate (e.g. polymers with higher capacity) was chosen for scale-up. The synthesis was adapted to suspension polymerisation to produce polymeric beads, more suitable for flow systems. Several suspension syntheses were explored, and the best candidates were chosen for functionalisation with trimethylamine (TMA) and tris(2-aminoethyl)amine (TREN) to obtain amino-enriched materials and for further testing on model solutions. One material was used for sorption/desorption experiments, and it was proven to be stable over 50 cycles of regeneration, using ssNMR. All the materials were compared with commercially available anion exchange resins, regarding capacity towards P. Finally, the polymers were tested on wastewater at different stages of treatment and in several dairy processing waste streams, showing enormous potential for P recovery in wastewater.

Thesis is embargoed until 31 July 2028.

Date of Award	Jul 2025
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	EU Horizon 2020 Marie Sklodowska-Curie ITN Programme
Supervisor	John McGrath (Supervisor) & Panagiotis Manesiotis (Supervisor)