Three-dimensional graphene/La(OH)-nanorod aerogel adsorbent by self-assembly process for enhanced removal and recovery of phosphate in wastewater.

Removal and recovery of phosphorus (P) from wastewater is beneficial to both environmental protection and resource sustainability. Enriching the low concentration of P in wastewater will greatly facilitate the effective recovery of P. To enhance the adsorption performance and recyclability of adsorbents for low concentration P-containing wastewater, a novel three-dimensional (3D) graphene/La(OH)-nanorod aerogel (GLA) was prepared by a unique self-assembly process in this study. Benefiting from the large specific surface area of graphene aerogel, which provides sufficient loading sites for the favorable dispersion of La(OH) nanorods, the GLA achieves an excellent P adsorption capacity of 76.85 mg/g. It is also highly selective for P, with adsorption capacity reduced by only 14% and 11% under the interference of high concentration of dissolved organic matter or multiple competing anions respectively. Further mechanistic investigation revealed that the whole adsorption process consists of three stages: (1) ion-exchange process; (2) LaP inter-sphere coordination process; and (3) crystal evolution process. In the continuous flow adsorption-desorption cycles, the P concentration was concentrated ~25 times that of the feeding water (2 mg P/L). To our knowledge, this is the first time that La-modified graphene aerogel has been studied for P recovery. This provides a new method for the P removal and recovery of low concentration P-containing wastewater.