Simultaneous organic/inorganic removal from water using a new nanocomposite adsorbent: A case study of p-nitrophenol and phosphate

A new nanocomposite adsorbent, HFO-802, was fabricated by incorporating nanosized hydrated ferric oxides (HFOs) inside the hyper-cross-linked polymeric adsorbent NDA802. The co-removal of inorganic and organic pollutants was examined using p-nitrophenol (PNP) and phosphate as the model compounds. Three widely used adsorbents, including powdered activated carbon, macroporous polystyrene adsorbent (XAD-4) and the host adsorbent (NDA802), were tested for comparison. HFO-802 exhibited superior properties when compared to the other adsorbents during the simultaneous removal of phosphate and PNP. These better properties were attributed to the unique structure of HFO-802; i.e., the encapsulated HFO nanoparticles exhibit preferable removal of phosphate through inner-sphere complexation, whereas the host NDA802 captures PNP through micropore filling, pi-pi interactions, and acid-base interactions. More attractively, the exhausted HFO-802 was amenable to effective regeneration by using an alkaline solution, allowing for repeated use with a constant co-removal efficiency over 10 continuous cycles of operation. The effect of solution pH, contact time and ionic strength on HFO-802 co-removal was determined. The results highlighted a new method to fabricate bifunctional adsorbents for the co-removal of inorganic and organic pollutants by encapsulating metal oxide nanoparticles inside a microporous solid host. (C) 2015 Elsevier B.V. All rights reserved.