Performance and prospects of different adsorbents for phosphorus uptake and recovery from water

The need to control eutrophication in water bodies and the risk of supply shortage of phosphate rock have motivated the search for treatment techniques able to sequester and recover P from wastewaters. Current techniques can recover phosphate from highly loaded aqueous media, but it is increasingly important to develop economically attractive solutions for low concentration effluents. Adsorption can be highly selective and efficient for phosphate uptake and recovery from water and wastewater, which can act as secondary sources of phosphorus. This review gathers the data reported in the literature about phosphate removal from water through adsorption and subsequent recovery through desorption or direct use of the phosphorus-loaded adsorbent as a fertilizer. Metal (e.g. Al, Ca, Ce, Fe, La, Mg, Mn, Zn, Zr) hydroxides/oxides provide excellent adsorption capacities of phosphate, in addition to other advantages such as fast kinetics and good selectivity. These compounds have been incorporated into zeolites, mesoporous silica, activated carbon, biochar, and bio-derived materials, to enhance their adsorption capacities. Significant advances have been made in engineered materials, including magnetic and granular adsorbents. Literature reports other valuable attempts to upscale the process including pilot-scale experiments, application in fixed-bed columns and to real wastewaters. Further studies are necessary to overcome some limitations still observed. Future work should give more attention to phosphorus recovery from the eluates and to the direct use of P-loaded adsorbents.