Preparation of Fe-filled MOF-Al-based hydrogel for efficient reclaim of phosphate from wastewater and reusing as a slow-release fertilizer.

In this study, a novel Fe-filled MOF-Al-based hydrogel (SA@Fe@MOF-Al) was prepared and characterized by X-ray diffraction, scanning electron microscopy, thermogravimetric analysis. The SA@Fe@MOF-Al hydrogel bead was used as an adsorbent to adsorb $H_2{\mathrm{PO}}_4^{-}$ from wastewater. The effects on adsorption were investigated, including pH and coexist ion. The adsorption reached equilibrium within 30 min. The maximum $H_2{\mathrm{PO}}_4^{-}$ adsorption capacity of SA@Fe@MOF-Al was 103.09 mg g^-1 at 298K with pH 7.0. Meanwhile, thermodynamic results confirmed that adsorption is exothermic and spontaneous. The adsorption kinetics displayed that SA@Fe@MOF-Al adsorption process was suitable to the pseudo-first-order and Langmuir model. Moreover, the feasibility of reusing the P-laden carrier material as a slow-release fertilizer was determined. The study results indicated that the product demonstrated excellent slow-release and water-retention properties. Thus, it has potential applications in improving soil moisture content and reducing soil moisture evaporation rate.