Search

• CuFe 2 O 4 was uniformly anchored on kaolinite to activate peroxymonosulfate (PMS). • Sulfate radicals are the primary radical species in CuFe 2 O 4 /kaolinite/PMS system. • CuFe 2 O 4 /kaolinite exhibited high catalytic activity and low leaching of metal ions. • More hydroxyl groups and accessible reactive sites enhanced its catalytic activity. • Low leaching of metal is ascribed to Fe O Al bond between CuFe 2 O 4 and kaolinite. In this study, CuFe 2 O 4 /kaolinite catalysts were fabricated through a facile citrate combustion method and were evaluated for their efficiency to activate peroxymonosulfate (PMS) towards the destruction of bisphenol A (BPA). The prepared catalysts were systematically characterized to explore the relationship between their characteristics and catalytic activities. In general, higher specific surface area, larger pore volume, more hydroxyl groups, and more accessible reactive sites of 40%-CuFe 2 O 4 /kaolinite contributed to the greater catalytic activity in peroxymonosulfate activation for BPA degradation compared to bare CuFe 2 O 4. Monodispersed CuFe 2 O 4 nanoparticles were uniformly anchored on the surface of kaolinite with Fe O Al bond, which prevented leaching of metal ions and contributed to the excellent reusability. The sulfate radicals produced in the CuFe 2 O 4 /kaolinite/PMS system were proved as the predominant radical species through electron spin resonance (ESR) and radical quenching experiments. Based on the results of X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance – Fourier transform infrared spectra (ATR-FTIR), two main possible pathways of sulfate radicals generation were proposed: the generation and decomposition of Cu(II)-(HO)OSO 3 − (Cu(II)/Cu(III) and Cu(III)/Cu(II) redox reaction) and the oxidation of Fe(II). Moreover, the BPA degradation pathway was proposed through the identification of transformation products. This work provides an interesting insight for PMS activation by the high-efficient natural mineral-based catalysts for wastewater reclamation. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Natural kaolinite was used to activate peroxymonosulfate for the first time. • Surface-bonded and structural hydroxyl groups are responsible for PMS activation. • Kaolinite can be continuously reused to activate PMS without recovery. • OH and SO 4 − were identified as the primary reactive species. • The H 2 PO 4 − enhanced PMS decomposition and increased atrazine degradation. Abstract In this study, natural kaolinite, an abundant, low cost, thermally and chemically stable, and easily recyclable material was evaluated for the performance to activate peroxymonosulfate (PMS) by the degradation of atrazine. Based on radical quenching experiments and electron spinning resonance (ESR) spectra, hydroxyl radical (OH) and sulfate radical (SO 4 −) were identified to be the primary reactive species. The effects of catalyst loading, initial reaction pH, PMS dosage, initial atrazine concentration, and the presence of inorganic ions (Cl−, NO 3 −, HCO 3 − and H 2 PO 4 −) were also investigated in this work. Interestingly, the presence of H 2 PO 4 − enhanced the degradation efficiency of atrazine via promoting the decomposition of PMS. The transformation products were detected on a quadrupole time-of-flight liquid chromatography/mass spectrometer (Q-TOF-LC-MS) and the possible degradation pathway of atrazine was proposed. Based on comprehensive characterizations of crystal phase and crystallinity, porosity and pore structure, surface morphology, functional groups, and valence state of specific elements, the catalytic ability of natural kaolinite towards PMS is attributed to the abundant surface-bonded and structural hydroxyl groups. This study provides new insights of PMS activation by natural minerals for the degradation of refractory and deleterious contaminants in wastewater treatment. [ABSTRACT FROM AUTHOR]

Developing low-cost, high-efficiency catalysts for advanced oxidation processes remain a key issue for the degradation of organic pollutants. In this study, a novel FeCo 2 O 4 /rectorite composite was synthesized via a facile combustion process and employed to activate peroxymonosulfate (PMS) for dealing with atrazine (ATZ). The addition of rectorite could result in higher specific surface area, smaller pore size and more hydroxyl groups, which were beneficial to enrich pollutants to the adsorption sites and provide sufficient reactive sites. After meticulous evaluation, the degradation efficiency of FeCo 2 O 4 /rectorite composite towards ATZ exhibited improved PMS activation efficiency which was about 2.6 times than that of pure FeCo 2 O 4. Based on the characterization results, the sulfate radicals and hydroxyl radicals were considered to be the main free radicals which were involved into the circulation of Co(II)–Co(III)–Co(II) as well as the oxidation of ≡Fe(II), which was responsible for the remarkable catalytic efficiency. In addition, the chemical stability and superior catalytic performance of FeCo 2 O 4 /rectorite should also be attributed to the chemical combination between metal ions and the surface hydroxyl groups of rectorite. Overall, these findings are beneficial for understanding the mechanism of PMS activation by natural mineral-based catalysts and contributing to the practical application of sulfate-based technology for organic wastewater treatment. Image 1 • In situ growth of FeCo 2 O 4 on natural rectorite for PMS activation was achieved. • FeCo 2 O 4 /rectorite composite exhibited higher PMS activation efficiency than pure FeCo 2 O 4. • Hydroxyl groups of rectorite accelerated PMS activation significantly via combining with metal oxide. • Both OH• and SO 4 •− were identified as main reactive species. [ABSTRACT FROM AUTHOR]