Fabrication of agricultural waste supported UiO-66 nanoparticles with high utilization in phosphate removal from water

Efficient removal of phosphate by agricultural waste derived materials from wastewater is an effective and economic way to prevent eutrophication and water bloom. In this work, we proposed a novel method to immobilize a water stable metal organic framework UiO-66 nanoparticle within modified wheat straw through in-situ hydrothermal synthesis and obtained the new UiO-66 nanocomposites. As indicated by SEM and BET analyses, UiO-66 is uniformly dispersed on the surface and the inner pores of modified wheat straws. The utilization rate of active sites is significantly promoted after UiO-66 impregnation within positively charged wheat straw (St + @UiO-66) which is more beneficial for UiO-66 dispersion. The saturated adsorption capacity of hybrid St + @UiO-66 is shown to be more than 2 times greater than bulky one under high ionic strength. Compared to commercial anion exchanger D201, St + @UiO-66 exhibits excellent selectivity and preference toward phosphate. The adsorption process is highly pH-dependent and adsorption kinetics data fitted well with the pseudo-second-order model. FTIR and XPS study indicated that hydroxyl groups on the surface of UiO-66 were replaced by phosphate ions and the inner-sphere complexation was formed via establishing Zr–O–P coordination bonds. In addition, St + @UiO-66 could be sustainably employed for phosphate removal through the combination of periodic regeneration and complete regeneration. It is demonstrated that St + @UiO-66 has preferable adsorption of phosphate with improved utilization of active sites, implying great potential as a promising phosphate adsorbent.