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

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2023-06, Vol.11 (25), p.13552-13563
• Main Authors: Okaikue-Woodi, Fanny E. K, Ray, Jessica R
• Format: Article
• Language: English
• Subjects: Buffers; Coatings; Decay; Decomposition; Environmental impact; Gels; Intermediates; Iron; Organic compounds; Oxidants; Oxidation; Oxidizing agents; Phenols; Potassium; Potassium ferrate; Sand; Silicon dioxide; Tetraethoxysilane; Tetraethyl orthosilicate; Wastewater; Water treatment
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d3ta01950k

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 SiO 2 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 SiO 2 gels is impractical and requires post-treatment disposal. This study leverages SiO 2 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 μg per L phenol-a representative wastewater organic compound-was achieved at a faster rate by the composite than by application of aqueous K 2 FeO 4 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 K 2 FeO 4 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. Degradation of phenol and formation of an oxidation byproduct by synthesized Fe( vi )-coated sand.