Enhanced phosphate removal from water by hydrated neodymium oxide-based nanocomposite: Performance, mechanism, and...

Phosphorus (P) control has been recognized as an imperative task to mitigate water eutrophication and settle the imminent shortage of P resources. Despite intensive effort put into this matter, it is still generally challenging for the current methods to remove and even potentially recover phosphorus (as phosphate) from complicated water matrices. To this end, we proposed a novel nanocomposite via coupling polystyrene anion exchanger (PsAX) with hydrated neodymium oxide (HNdO) nanoparticle for selective removal of phosphate. The developed nanocomposite, i.e., HNdO-PsAX, exhibited quite stable and efficient phosphate adsorption over a wide pH range of 3.0-10.0 with the maximum adsorption capacity as 85.4 mg P/g. It also showed satisfied anti-interference against various competing substances; notably, HNdO-PsAX obviously outperformed Phoslock, a commercial lanthanum-based adsorbent exclusively for phosphate sequestration, particularly under the interference of bicarbonate and humic acid, which were admitted as the paralyzing factors for Phoslock. The superior affinity of HNdO-PsAX towards phosphate, driven by the specific Nd-P inner-sphere complexation as evidenced by XPS, FT-IR, and the lattice evolution of HNdO nanoparticle, renders the nanocomposite eminently suitable for sequestrating trace phosphate. Fixed-bed treatment validated that HNdO-PsAX was capable of treating ∼11,800 bed volume of a simulated wastewater (from 2.0 to below 0.5 mg P/L), approximately 12 times higher than that of the previously reported Fe-based nanocomposite (HFO-PsAX, ∼ 900 BV); also, a satisfactory outcome in treating authentic municipal wastewater by HNdO-PsAX and the feasibility of regenerating the exhausted one by a binary NaOH-NaCl solution were recognized. This work provides a new potion of enhanced phosphorous control for surface water and wastewater.