Tremella-like Zn-Al-Zr-Layered Double-Hydroxide/Graphene Oxide Nanocomposites for Enhanced Phosphorus Recovery

By virtue of the hydroxyl and carboxyl groups on the graphene oxide (GO) plane, three-dimensional tremella-like Zn-Al-Zr-layered double-hydroxide/GO (Zn-Al-Zr LDH/GO) nanocomposites have been successfully prepared via the self-assembly process. As compared to Zn-Al-Zr LDH, the Zn-Al-Zr LDH/GO nanocomposite (LDH/GO-4) possesses a hierarchical pore structure; it shows an enlarged pore width which endows it with enhanced phosphorus (P) adsorption capacity, and the fitting of nonlinear Langmuir showed that the maximum adsorption capacity reaches 36.86 +/- 0.76 mg-P/g. The fitting of the kinetic model confirmed that the adsorption process was predominantly chemisorption. Meanwhile, fitting of the thermodynamic model indicated that the adsorption process was endothermic, stochastic, and spontaneous. For LDH/GO-4, the [-C-O-Zn(OH)(x)] and [-COO-ZrO(OH)(x)] groups are its chief active sites to chemically absorb P. In this study, LDH/GO-4 can make the total phosphorus (TP) concentration of the real river water decline from 0.28 mg/L to near zero in 24 h, while the Phoslock commercial product only achieves a TP removal rate of 46.43% under the same conditions. Moreover, LDH/GO-4 also has good reusability in a steady recovery of P, and the removal rate of TP was still over 95% after it experienced the adsorption-desorption of P for five cycles. Thus, LDH/GO-4 shows great potential for application in the sustainable P recovery field.