Understanding and improving the reusability of phosphate adsorbents for wastewater effluent polishing

Abstract
Phosphate is a vital nutrient for life but its discharge from wastewater effluents can lead to eutrophication. Adsorption can be used as effluent polishing step to reduce phosphate to very low concentrations. Adsorbent reusability is an important parameter to make the adsorption process economically feasible. This implies that the adsorbent can be regenerated and used over several cycles without appreciable performance decline. In the current study, we have studied the phosphate adsorption and reusability of commercial iron oxide based adsorbents for wastewater effluent. Effects of adsorbent properties like particle size, surface area, type of iron oxide, and effects of some competing ions were determined. Moreover the effects of regeneration methods, which include an alkaline desorption step and an acid wash step, were studied. It was found that reducing the adsorbent particle size increased the phosphate adsorption of porous adsorbents significantly. Amongst all the other parameters, calcium had the greatest influence on phosphate adsorption and adsorbent reusability. Phosphate adsorption was enhanced by co-adsorption of calcium, but calcium formed surface precipitates such as calcium carbonate. These surface precipitates affected the adsorbent reusability and needed to be removed by implementing an acid wash step. The insights from this study are useful in designing optimal regeneration procedures and improving the lifetime of phosphate adsorbents used for wastewater effluent polishing.

Citation
Suresh Kumar P, Ejerssa WW, Wegener CC, Korving L, Dugulan AI, et al. (2018) Understanding and improving the reusability of phosphate adsorbents for wastewater effluent polishing. Water Research 145: 365–374. Available: http://dx.doi.org/10.1016/j.watres.2018.08.040.

Acknowledgements
This work was performed in the TTIW-cooperation framework of Wetsus, European Centre Of Excellence For Sustainable Water Technology (www.wetsus.nl). Wetsus is funded by the Dutch Ministry of Economic Affairs, the European Union Regional Development Fund, the Province of Fryslân, the City of Leeuwarden and the EZ/Kompas program of the “Samenwerkingsverband Noord-Nederland”. We thank the participants of the research theme “Phosphate Recovery” for their financial support and helpful discussions.

Publisher
Elsevier BV

Journal
Water Research

DOI
10.1016/j.watres.2018.08.040

Additional Links
https://www.sciencedirect.com/science/article/pii/S0043135418306717

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