Enhanced phosphate removal by La(OH)3 embedded sodium alginate aerogel composites: Batch and column studies

The enhanced removal of phosphate (P) from wastewater is a major challenge for eutrophication control in natural water bodies. Adsorption as a cost-efficient technology has been applied for excessive P removal from wastewater, however, the stability and recyclability of the adsorbents are still challenging. In this study, La(OH)₃ was embedded inside the porous sodium alginate aerogel to synthesize a novel millimeter-sized aerogel (LA) for efficient P removal with high stability. Static experiments revealed that the adsorption of P by LA is more consistent with the PSO kinetic model and the Langmuir model; the suitable pH range for P adsorption is wide, and the co-existing substances have little effect on P removal. Specifically, the maximum Langmuir adsorption capacity of LA reached up to 11.6 mg/g at 288 K. The exhausted LA could be effectively regenerated and maintained 81.7 % of its initial adsorption capacity after 5 adsorption-desorption cycles. Regeneration experiments revealed that LA maintained high stability, which could be easily recycled in real operation. The adsorption mechanism of P onto LA was revealed by SEM, BET, XRD, FTIR, and XPS analysis. The predominant pathway for P removal was confirmed to be the inner-sphere complexation between P and La. In addition, the column study exhibited that LA could be used as the column filler to effectively remove P through continuous filtration. Overall, the above results proved LA to be a promising adsorbent for efficient P removal in complex water environments.