Phosphorus capture from subsurface drainage water using iron-activated alumina (Alcan): Column adsorption,...

This study investigates the column adsorption and regeneration performance of iron-activated alumina (Alcan) for phosphate removal from subsurface drainage water under dynamic flow conditions. Continuous-flow fixed-bed column experiments were conducted at three empty bed contact times (EBCTs) of 5, 10, and 15 min using synthetic subsurface drainage water with 2 mg/L phosphate. Saturated media were regenerated using 0.1 mol/L potassium hydroxide (KOH), and adsorption-desorption cycles were repeated to assess reusability. Results showed that > 90 % phosphate recovery was achieved during 1st desorption cycle at 120 and 40 pore volumes for 5 and 10 min EBCTs, respectively. However, second-cycle adsorption showed reduced performance, notably 72 % phosphate recovery at 5 min EBCT due to residual phosphate and structural degradation. ICP-OES and FE-SEM analysis confirmed elemental leaching and morphological changes post-regeneration. A cost benefit analysis demonstrated a competitive treatment cost of $829/kg P removed. Furthermore, agronomic evaluation of P-saturated media indicated comparable results to conventional diammonium phosphate (DAP), supporting its dual functionality as a slow-release P fertilizer. Despite performance loss, Alcan demonstrated high initial adsorption capacity and partial reusability, suggesting potential as a recyclable adsorbent and a slow-release phosphate source in sustainable nutrient management strategies. This study uniquely integrates dynamic column adsorption, alkaline regeneration, and agronomic reuse evaluation of iron-activated alumina (Alcan) for phosphorus capture from subsurface drainage water, presenting a closed-loop, circular approach that bridges water treatment with nutrient recovery.