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• 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]

Natural minerals are generally accepted as one of the most suitable carriers to support TiO 2 in photocatalytic and other applications because of their abundance, low cost, large surface area, and easy recyclability. Hence, in this work, a novel 0D/2D TiO 2 /kaolinite composite endowed with presence of oxygen vacancies and surface defect sites was synthesized through a mild sol-gel method combining with nitrogen induction. Ciprofloxacin (CIP) was taken as the main target organic pollutant to study the photocatalytic performance of the synthesized catalyst. The results showed that the nitrogen treated TiO 2 /kaolinite composite exhibited improving degradation performance for adsorption-photocatalytic elimination of CIP within broad radiation spectrum (200–800 nm). The synthesized composite exhibited enhanced reaction rate constant which is nearly 7.00, 2.54 and 3.13 times higher than that of bare TiO 2 treated with air under UV, solar, and visible light, respectively. Moreover, the newly prepared composite also exhibited significant enhancement towards the removal of formaldehyde under both UV and visible light. Radical scavenger experiments and ESR results indicated that holes should be the main oxidizing species within broad spectrum in the degradation system. The enhanced activity of nitrogen treated composite is mainly attributed to the induced oxygen vacancies as well as the intimate interface contact between TiO 2 and kaolinite, resulting in smaller grain size, higher light absorption ability, and faster carrier separation efficiency. It is expected that this high-efficiency composite photocatalyst based on natural minerals will be a promising candidate for the elimination of pharmaceutical and personal care products and volatile organic compounds within broad radiation spectrum. [ABSTRACT FROM AUTHOR]

A novel 3D heterogeneous g-C 3 N 4 /TiO 2 /kaolinite composite with enhanced visible light activity was fabricated via a mild sol-gel method associated with chemical stripping and self-assembly. Compared with bare photocatalysts, the g-C 3 N 4 /TiO 2 /kaolinite 3D structure exhibits enhanced adsorption-photocatalytic degradation ability for the removal of ciprofloxacin (CIP) under visible-light irradiation, and also facilitate the recyclability of the photocatalyst as demonstrated from the reusability test. The apparent rate constant of the composite is up to around 5.35 times, 6.35 times and 4.49 times that of bare TiO 2 , g-C 3 N 4 and P25, respectively, and a possible degradation pathway was also proposed. On the other hand, the as-received composite also exhibited enriched disinfection ability towards S. aureus . It is indicated that the superoxide radical ( O 2 − ) is the main active species in the degradation process, and the superior photocatalytic performance of composite should be mainly attributed to both the improvement of light harvesting as well as the enhanced separation and transfer efficiency. It is expected that this novel ternary visible-light responding composite would be a promising candidate material for the organic pollutants degradation and bacteria inactivation. [ABSTRACT FROM AUTHOR]

A novel CoNi 3 O 4 /diatomite hybrid is constructed through vertically oriented growth of 2D CoNi 3 O 4 nanoribbons with atomic layer-thickness on cost-effective diatomite template. Distinct from stacked CoNi 3 O 4 with a large portion of "dead surface", diatomite derived CoNi 3 O 4 nanoribbons possess abundant exposed edges, sharp corners, and open diffusion channels. These unique characteristics offer CoNi 3 O 4 /diatomite hybrid excellent peroxymonosulfate activation efficiency in real water bodies. • 2D CoNi 3 O 4 nanoribbons were fabricated via vertically oriented growth on diatomite. • CoNi 3 O 4 /diatomite showed rich exposed edges, sharp corners and diffusion channels. • CoNi 3 O 4 /diatomite presented excellent PMS catalytic activity in real water bodies. • S O 4 - • , OH and 1O 2 were generated and functioned in CoNi 3 O 4 /diatomite/PMS system. • O 2 − contributed to reversible redox cycle of Co2+/Co3+ and Ni2+/Ni3+. The reactive oxygen radicals generated by peroxymonosulfate (PMS) activation exhibit great potential to deal with refractory contaminants of emerging concern. However, mass production of efficient and cost-effective catalysts for PMS activation is still a long-term goal for its widespread practical application. Herein, a novel CoNi 3 O 4 /diatomite hybrid is constructed through vertically oriented growth of 2D CoNi 3 O 4 nanoribbons with atomic layer-thickness on cost-effective diatomite template. Distinct from stacked CoNi 3 O 4 , CoNi 3 O 4 /diatomite composite possesses abundant exposed edges, sharp corners, and open diffusion channels. Abundant exposed edges and sharp corners create more open space and active sites for PMS activation. Open diffusion channels accelerate the migration of PMS and contaminants. Such characteristics offer CoNi 3 O 4 /diatomite hybrid excellent PMS activation efficiency. Furthermore, sulfate radical plays the dominant role in atrazine degradation. Superoxide radical contributes to reversible redox cycle of Co2+/Co3+ and Ni2+/Ni3+. This study provides a novel strategy for cost-effective mass production of various Fenton-like 2D catalysts. [ABSTRACT FROM AUTHOR]

• Oxygen-vacancy-rich Co 3 O 4 /illite can activate peroxymonosulfate (PMS) efficiently. • Modulating crystallization of Co 3 O 4 by illite resulted in rich oxygen vacancies. • Theoretical calculations were employed to elucidate catalytic mechanism for PMS. • Rich oxygen vacancies accelerated electron-transfer and reduced adsorption energy. • S O 4 - • , OH and 1O 2 were generated and functioned in Co 3 O 4 /illite/PMS system. Natural illite microsheets were firstly utilized to induce oxygen vacancies into ultrafine cobalt oxide (Co 3 O 4) for highly efficient Fenton-like catalysis via activation of peroxymonosulfate (PMS). The results indicated that presence of illite microsheets regulated multi-directional crystallization of Co 3 O 4 nanospheres and resulted in reduced grain size and crystallinity. The smaller grain size provided more reactive edge sites for PMS catalysis. The numerous indistinct lattice boundaries caused by reduced crystallinity created abundant oxygen vacancies. Density functional theory (DFT) calculations illustrated that presence of oxygen vacancies significantly reduced adsorption energy and accelerated electron transfer, which further faciliated PMS activation. The oxygen vacancy-rich Co 3 O 4 /illite exhibited superior catalytic efficiency in real water matrix. Apart from sulfate and hydroxyl radicals, singlet oxygen generated from oxygen vacancy-based reaction pathway also played a significant role in atrazine degradation. This strategy provided a new insight for future designing of natural mineral-based catalysts for efficient wastewater treatment via Fenton-like process. [ABSTRACT FROM AUTHOR]