[Fabrication of a Biomass-Based Hydrous Zirconium Oxide Nanocomposite for Advanced Phosphate Removal]

Wheat straws were modified by 3-chloro-2-hydroxypropyl trimethylammonium chloride (CTA) to obtain aminated wheat straw St-N'. The optimum synthetic conditions were determined to be NaOH with 30% mass fraction, CTA of 100 mL, reaction temperature of 80℃, and reaction time of 3 h, which was verified by orthogonal experiments. Nano-sized hydrous zirconium oxides (HZO) were immobilized into St-N' by an in situ precipitation method to obtain the nanocomposite St-N'-Zr. The SEM, TEM, XRD, and BET results indicated that the nano-sized HZO with 50-100 nm sizes were uniformly loaded onto the inner surface of the biomass-based carrier St-N' that was amorphous in nature. A Langmuir adsorption isotherm fitted the adsorption process well, and the maximum adsorption amount was calculated to be 33.90 mg·g^-1. The optimal pH range was 1.8-6.0, displaying good removal capacity of phosphate in acidic waters. In the presence of high levels of competing anions, the phosphate adsorption still retained more than 70% of the original amount, showing the higher preference of St-N'-Zr towards phosphate than towards the commercial anion exchanger D-201. After 10 cycles of adsorption-desorption, the removal efficiency remained stable, confirming the good regeneration ability and potential application of St-N'-Zr.