Preparation of ZrLDH-based 3D microspheres for phosphate recovery

Phosphorus is one of key nutrients for plant growth and the main ingredient in phosphate fertilizer, while it is abundant in wastewater as contaminant. Here, in order to recycle discarded phosphate with a kind of eco-friendly inorganic functional materials, a novel Zr-doped layered double hydroxides (ZrLDHs)- based 3D microspheres (ZrLDHMs) was prepared by hydrothermal method, and its structure and micromorphology were characterized by scanning electron microscopy, Fourier Transform infrared spectra, X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer-Emmet-Teller and thermogravimetric analysis. Moreover, the influences of main factors in the phosphate adsorption and reusability of ZrLDHMs were investigated, and its adsorption mechanism was discussed. It was found that the removal rate of phosphate got to 97.3%, and the efficiencies of ZrLDHMs for phosphate adsorption still reached 86.8% after 5 cycles of adsorption–desorption, indicating its reusability. The kinetic data showed that ZrLDHMs adsorption could be well described by pseudo-second-order kinetic models. Furthermore, the phosphorus-adsorbed ZrLDHMs (ZrLDHMs-P) could be used as a slow-release fertilizer, and promote plant growth. In summary, ZrLDHMs could be used for reclaiming phosphate from wastewater treatment, and the obtained ZrLDHMs-P was an eco-friendly slow-release fertilizer. It realized the efficient utilization of the adsorbent and the recycling of phosphorus in the ecosystem. This provided a new way for reducing eutrophication, enriching soil, developing new sustainable and ecologically friendly development.