Ammonium removal and recovery from municipal wastewater by ion exchange using a metakaolin K-based geopolymer. (15th October 2022)

• Record Type: Journal Article
• Authors: Medri, Valentina; Papa, Elettra; Landi, Elena; Maggetti, Carla; Pinelli, Davide; Frascari, Dario
• Is Part Of: Water research. Volume 225(2022)
• Publication Date: 2022-10-15
• Subjects: Ion exchange -- Geopolymer -- Natural zeolite -- Ammonium recovery -- Nutrient recovery -- Wastewater treatment; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2022.119203
• Languages: English
• ISSNs: 0043-1354

Abstract

Highlights: Ammonium recovery from real municipal wastewater in a continuous flow plant process. Ammonium adsorption test on saline wastewater characterized by cations competition. Geopolymer granules showed high ammonium selectivity and adsorption capacity Geopolymer granules did not deteriorate after adsorption/regeneration cycles. Geopolymer allows to obtain a Na-free desorbed product potentially good as fertilizer. Abstract: Among the available technologies for ammonium removal from wastewater, ion exchange represents one of the most promising ones in the perspective to recover ammonium and produce a fertilizing product. However, the vast majority of previous studies on ammonium ion exchange did not evaluate the process robustness under real operational conditions nor optimized the desorption step. In this paper, tests of ammonium removal and recovery were conducted on a metakaolin K-based geopolymer, compared with a high-performing Italian natural zeolite in K-form. Real municipal and saline wastewater was treated in a continuous flow pilot plant equipped with a 60-cm adsorption bed (bed volume 203 mL, sorbent mass 145–173 g, empty bed contact time 10 min). Geopolymer granules showed higher performances in terms of selectivity towards ammonium, operating capacity (8.5 mgN g −1 dry adsorbent at an inlet concentration of 40 mgN L − 1 ), bed volumes of wastewater treated at the selected breakpoint (149). Geopolymer resulted to be a cost-effective adsorbent for wastewater treatment capable to adsorb cations by ion exchange, allowing a fractionated desorption procedure that led to recover ammonium in a solution composed mainly by NH4 NO3 (37%wt ) and KNO3 (56%wt ), potentially usable as fertilizer. The geopolymer robustness was assessed after repeated adsorption/regeneration cycles showing that the geopolymer mechanical and morphological properties did not deteriorate. The results make the tested geopolymer a very promising material for the optimization and scale-up of the ammonium recovery process in a circular economy perspective. Graphical abstract: Image, graphical abstract