Granular ferric hydroxide/PVC composites for phosphate recovery and re-use

Granulated ferric hydroxide (GFH) removes phosphates from impaired water. However structural instability, pore-clogging, high-pressure drop, and mass loss are problematic. Thus, GFH granules were dissolved in polyvinyl chloride (PVC) and added to an anti-solvent bath. Subsequently, GFH/composite beads formed with 75 to 85 wt% GFH with a bead size of ca. 2.6 mm in diameter. Beads exhibited low attrition for the 75 wt% and 80 wt% composites (1 % and 1.8 % mass loss, respectively), while a mass loss for the 85 wt% beads was 7.8 %. Increasing PVC concentration enhanced bead robustness without impacting the phosphate loading process during the 48-h equilibrium trials (31.2 and 29.7 mg P/g for the 75 wt% and 80 wt% GFH beads, respectively, in comparison to the 29.7 mg P/g observed for the GFH granules). In the presence of competing anions (SO 4 2− , NO 3 − , and Cl − anions with a 1:1 M ratio with phosphate anions), the P loading onto 75 wt% beads remained around 29.4 to 30.6 mg P/g after 48 h. Regeneration with 0.1 M NaOH solutions removed most phosphate anions after multiple loading/regeneration cycles. In summary, using GFH/PVC composites to recover phosphate appears to be worthy of further testing in complex wastewater solutions. • GFH-PVC composite beads show greater performance than GFH alone. • Composite beads were more robust than GFH. • The porous composite surface was decorated with pores <1 μm. • Kinetics and equilibria performance similar for GFH material and composites • 0.1 M NaOH was preferred to remove and recover phosphate from water.