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In this study, a natural occurring ilmenite was successfully developed as an efficient catalyst/photocatalyst for bacterial inactivation coupling with persulfate (PS) under visible light (Vis) irradiation. The excellent bacterial inactivation is demonstrated by the result that the bactericidal efficiency in the ilmenite/PS/Vis process reached 6 log 10 cfu/mL within 30 min as compared to that of 1.5 log 10 cfu/mL for the ilmenite/Vis process and 4 log 10 cfu/mL for the ilmenite/PS under same conditions. Integrated with the electron paramagnetic resonance analysis, electrochemical measurements and photoluminescence spectroscopic analysis, the enhanced performance was attributed to the accelerated capture of photo-generated electrons by PS and ≡Fe(II) of ilmenite promoted PS activation vice versa to collectively generate more radicals for E. coli inactivation in the ilmenite/PS/Vis process. For the first time, the generation of singlet oxygen ( 1 O 2 ) was proved to be the primary bactericidal agent other than SO 4 − and O 2 − , which caused leakage and mineralization of E. coli intracellular components. Impressively, the 1 O 2 -mediated ilmenite/PS/Vis system showed good inactivation performance in authentic water body and maintained good reusability in the pilot-scale 25 L reactor. This work highlights the great potential of natural ilmenite as catalyst and elucidated a new opportunity for persulfate remediation of controlling microbial water contaminants. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Visible-light photocatalyst ZnO/ZnFe 2 O 4 is fabricated firstly by calcining natural Fe-bearing sphalerite. • ZnO/ZnFe 2 O 4 exhibits improved photocatalytic performance for azo dye degradation and bacterial disfection. • The formation of matched band alignment between ZnO and ZnFe 2 O 4 improves the separation efficiency of carriers. • The optimization of ZnFe 2 O 4 spinel structure significantly enhances photocatalytic activities. • This method is a creative guidance via utilizing natural minerals to fabricate coupled photocatalysts. Abstract Micrometer-scale ZnO/ZnFe 2 O 4 coupled photocatalyst is synthesized via a simple, one-step thermal treatment performing on natural Fe-bearing sphalerite ((Zn, Fe)S). In situ high-temperature X-ray diffraction (XRD), thermogravimetry, differential thermal analysis (TG/DTA) and scanning electron microscopy (SEM) results indicated that octahedral ZnFe 2 O 4 (∼5 μm) formed on the surface of substrate-like ZnO (tens of microns) derived from the oxidation of sulfides upon heating to 800 °C in air for 1 h, and the two components kept stable phase ratio at 3:7 (wt%) from 900 °C (sample M-900) to 1200 °C (sample M-1200). X-ray absorption spectroscopy (XAS) and Raman spectra revealed that more Zn atoms in ZnFe 2 O 4 of M-1200 occupied tetrahedral sites than M-900, resulting in a sharper A 1g mode (∼647 cm−1), more ordered spinel structure and less antisite defects. Compared with visible-light responsive sphalerite (Zn, Fe)S, M-1200 performed more 200 nm of red-shifted optical absorption, 2.5 times at most higher the incident photon-to-electron conversion efficiency (IPCE) and 2–3-fold photocatalytic efficiency towards degradation of methyl orange and inactivation of Escherichia coli K-12. Besides, the photocatalytic activities of M-1200 preponderate over M-900, typical visible-light catalyst ZnFe 2 O 4 and ZnO/ZnFe 2 O 4 mechanically mixed sample. The optimization of lattice structure and the establishment of special band alignment were suggested to be remarkably beneficial to the separation of photogenerated electrons-holes and promote the photocatalytic performance. This study would enlighten a feasible and efficient strategy to fabricate coupled photocatalyst by utilizing Earth-abundant and low-cost natural minerals for solving environmental problems. [ABSTRACT FROM AUTHOR]

A novel magnetic natural pyrrhotite (NP) mineral photocatalyst was developed and modified by thermal treatment. Their photocatalytic activity were evaluated by photocatalytic inactivation of Escherichia coli K-12 under visible light. As compared to NP, the annealed NP was found to exhibit a remarkable enhanced bactericidal activity. Among them, the NP treated at 600 °C in air (NP600) had the highest activity and the inactivation rate was nearly 3 times higher than that of untreated NP. The X-ray diffraction (XRD) spectra indicated the mineral phase of NP600 transformed to mixed crystallite phases of hematite-pyrite (Fe 2 O 3 –FeS 2 ) composite. Thus, the enhanced photocatalytic performance was mainly attributed to the formation of Z-scheme photocatalysis system composed of hematite and pyrite, which could improve the electron-hole separation efficiency and the bactericidal efficiency. Scavenger study demonstrated that the dominant bactericidal agent changed from superoxide radical ( O 2 − ) for NP to hydroxyl radical ( OH) for NP600. Moreover, vibrating sampling magnetizer (VSM) analysis revealed that the saturated magnetism of NP after thermal anneal was enhanced. The strong magnetic behavior of thermal treated NP enabled the magnetic recovery of photocatalysts after liquid phase reaction. In addition, NP600 was more stable than untreated NP and with lower metal ion leakage even after four reaction cycles. This work supplied a cost-effective natural mineral-based photocatalyst and an efficient modification strategy to extend the application field of natural minerals in water disinfection. [ABSTRACT FROM AUTHOR]

2D/2D Z-scheme heterojunction was successfully prepared based on MgTi 2 O 5 and g-C 3 N 4 for visible light driven photocatalytic inactivation of E. coli. • Z-scheme 2D/2D MgTi 2 O 5 /g-C 3 N 4 hybrid was synthesized by in situ growth method. • The cost-effective composite showed enhanced VL driven E. coli inactivation activity. • The enhanced disinfection performance was ascribed to efficient charge separation. Novel and cost-effective Z-scheme 2D/2D MgTi 2 O 5 /g-C 3 N 4 hybrid was synthesized by in situ growth of MgTi 2 O 5 on the g-C 3 N 4 nanosheets. The photocatalytic activity of as-prepared hybrid was investigated using bacteria disinfection. The results indicated that the composite exhibited enhanced E. coli inactivation under visible light (VL) irradiation, with the complete inactivation of 7 log10 cfu/mL of cells reduction within 3 h, while the pristine g-C 3 N 4 and MgTi 2 O 5 almost showed no cell reduction under the same condition. The destruction of bacterial cell was investigated by fluorescence microscopic images and transmission electron microscopy analysis. The optimum photoactivity could be attributed to 1) the short charge transport distance and large interface contact area of the 2D/2D structure, 2) the efficient charge separation and spatially separated reductive and oxidative active sites originated from Z-scheme system. This work could shed lights on the design and fabrication of 2D/2D Z-scheme system for VL driven water disinfection. [ABSTRACT FROM AUTHOR]