Synthesis of ferrate (Fe(vi))-coated sand for stabilized reactivity and enhanced treatment of phenol

Ferrate (Fe(vi)) is a multifunctional water treatment agent of interest due to its benign environmental impact yet effective disinfecting, coagulating, and oxidizing capabilities. Fe(vi) decomposition in water produces short-lived Fe(v) and Fe(iv) intermediates which are highly effective oxidants. Studies report that the addition of SiO2 gels during Fe(vi) application can facilitate Fe(v) and Fe(iv) generation, and stabilize Fe(vi) reactivity for enhanced treatment. However, the application of SiO2 gels is impractical and requires post-treatment disposal. This study leverages SiO2 stabilization and catalytic effects on Fe(vi) reactivity to develop a Fe(vi)-coated sand water treatment media. The Fe(vi)-coated sand was synthesized by coating potassium ferrate onto sand modified with a tetraethyl orthosilicate precursor. The mass of Fe(vi) leached from the media surface increased with increasing pH (pH 7-9). Furthermore, Fe(vi) decay was faster in a borate buffer (k = 2.22 mg L-1 h(-1)) than in a phosphate buffer (k = 3.39 mg L-1 h(-1)). Removal of 219 +/- 12 mu g per L phenol-a representative wastewater organic compound-was achieved at a faster rate by the composite than by application of aqueous K2FeO4 powder (51% removed after 5 min compared to 37%). Decomposition of Fe(vi) from the composite surface in the presence of methyl phenyl sulfoxide (PMSO) suggests that reactive Fe(v) and Fe(iv) formation occurs at a faster rate than with K2FeO4 powder addition. In the presence of PMSO, phenol treatment was approximately 1.1 times higher, which suggests Fe(v)/Fe(iv) involvement. This novel, cost-effective and eco-friendly media presents a viable alternative for more feasible deployment of Fe(vi) in water treatment systems.

Automated summary

A Fe(vi)-coated sand water treatment media was developed by coating potassium ferrate onto sand. This media showed higher efficiency in removing organic compounds from wastewater compared to traditional SiO2 gels. It provides a cost-effective and eco-friendly alternative for Fe(vi) deployment in water treatment systems.