The MnFe2O4/g-C3N4/diatomite composites (Mn/G/D) were prepared via a facile precipitation-calcination method in this study. The Mn/G/D possessed higher specific surface area, lower electron-hole pairs’ recombination rate, as well as wider and stronger visible light absorption capacity. Since the synergistic effect between g-C3N4 and MnFe2O4, the photogenerated electron could transfer from g-C3N4 to MnFe2O4, which could promote the migration of electrons as well as enhance the photocatalytic activity and peroxymonosulfate (PMS) activation efficiency. Mn/G/D-5% composite displayed the excellent degradation performance of bisphenol A (BPA) with the removal efficiency of 99.9% under PMS/Vis system, which was approximately 2.47 and 63.8 times as high as that of the Mn/G/D-5%/PMS and Mn/G/D-5%/Vis system, respectively. Moreover, negative electricity derived from diatomite surface also promoted the photogenerated carriers’ migration, and the degradation rate constant was around 2.4 times higher than that of MnFe2O4/g-C3N4 (Mn/G). In addition, quenching experiments showed that both radical pathway (h+, ·OH, ·O2− and SO4·−) and non-radical pathway (1O2) were responsible for the degradation of BPA.

Decorating inorganic particles with core-shell structure is an attractive approach to broaden their practical application owing to the synergistic effects between inner core and outer shell. In this work, a novel rutile TiO2@AlPO4 core-shell composite has been constructed via a facile one-step wet chemical deposition method. The dense and thick AlPO4 shell can hinder direct contact between TiO2 core and outer environment, decrease light absorption ability, suppress separation of electron-hole pairs, and accelerate electron annihilation. Such unique properties hindered the generation of reactive oxygen species, further contributing to the suppression of photoactivity. The superior dispersion stability in aqueous system of TiO2@AlPO4 core-shell hybrid was attributed to its enhanced surface electronegativity. Thus-produced TiO2@AlPO4 core-shell hybrid with suppressed photoactivity and enhanced dispersion stability could further increase the weather durability and prolong the life span of TiO2-based pigment. Overall, this study provides new insight into the mass production of multi-functional rutile TiO2 pigments.

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 FeCo2O4/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 FeCo2O4/rectorite composite towards ATZ exhibited improved PMS activation efficiency which was about 2.6 times than that of pure FeCo2O4. 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 FeCo2O4/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.

A novel Ag/g-C3N4/kaolinite composite photocatalyst was fabricated for the first time through a two-step assembly strategy by employing in situ calcination and a photodeposition process. The synthesized Ag/g-C3N4/kaolinite composite reached a higher degradation rate of ibuprofen (IBP) with a reaction rate constant of 0.0113 min−1 at an Ag content of 7% under visible-light irradiation, which was approximately 1.87 times that of the Ag/g-C3N4 composite. Based on the physicochemical properties, the enhanced photocatalytic activity was attributed to the stronger adsorption property, wider photoresponse range and more efficient separation and transfer of electron-hole pairs. Furthermore, the incorporation of monodispersed Ag nanoparticles onto the g-C3N4/kaolinite sheets provided more reactive sites for the IBP degradation. In addition, according to the EPR study and trapping experiments, it was demonstrated that holes (h+) should be the key reactive species. A possible pathway of IBP degradation was also proposed based on the detected intermediates. Overall, the results of this work may facilitate the design of a novel visible-light-driven photocatalyst with a high efficiency that is derived from a natural mineral for environmental remediation.

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 CoNi3O4/diatomite hybrid is constructed through vertically oriented growth of 2D CoNi3O4 nanoribbons with atomic layer-thickness on cost-effective diatomite template. Distinct from stacked CoNi3O4, CoNi3O4/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 CoNi3O4/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.