In-situ synthesized 2D MXene/TiO2/Fe hybrid with (001)-(101) surface heterojunction for degradation of tetracycline under visible light

MXene-based composite photocatalysts for efficient degradation of antibiotics in wastewater

MXene-based (nano)materials have recently emerged as promising solutions for antibiotic photodegradation from aquatic environments, yet they are limited by scalability, stability, and selectivity challenges in practical settings. We formulated Fe2O3-SiO2/MXene ternary nano-photocomposites via coupled wet impregnation and sonochemistry approach for optimised tetracycline (TC) removal (the second most used antibiotic worldwide) from water using response surface methodology-central composite design (RSM-CCD). The photocatalysts containing various loading of Fe2O3/SiO2 (5-45 wt%) on the MXene with a range of calcination temperatures (300-600 °C) via RSM optimisation were synthesised, characterised regarding crystallinity properties, surface morphology, binding energy, and light absorption capability, and analysed for TC degradation efficiency. The 25FeS/MX-450 composite among all samples demonstrated a superior efficiency in TC photocatalytic removal (98%) under optimised conditions (TC degradation: 39.75 mg/L, time: 68.28 min, pH: 5.57, catalyst dosage: 0.75 g/L). The developed surface area, with a reduced band gap due to FeS nanoparticles incorporation with improved light absorption within the visible spectrum, played a crucial role in the 25FeS/MX-450 heterostructure matrix, enhancing photogenerated carriers' separation and transportation capabilities. The tetracycline photoreduction mechanism involved electron transfer from FeS to the surface of MXene, engaging with O2 to produce •O2-, attributed to the high electron mobility of MXene. Our findings for such nano-photocomposites materials can underscore the considerable potential of MXene-based nanomaterials for pharmaceutical removal from waterways.

MXene/ZnS/chitosan-cellulose composite with Schottky heterostructure for efficient removal of anionic dyes by synergistic effect of adsorption and photocatalytic degradation

Nowadays, dye water pollution is becoming increasingly severe. Composite of MXene, ZnS, and chitosan-cellulose material (MX/ZnS/CC) was developed to remove anionic dyes through the synergistic effect of adsorption and photocatalytic degradation. MXene was introduced as the cocatalyst to form Schottky heterostructure with ZnS for improving the separation efficiency of photocarriers and photocatalytic performance. Chitosan-cellulose material mainly served as the dye adsorbent, while also could improve material stability and assist in generation of free radicals for dye degradation. The physics and chemistry properties of MX/ZnS/CC composite were systematically inspected through various characterizations. MX/ZnS/CC composite exhibited good adsorption ability to anionic dyes with adsorption capacity up to 1.29 g/g, and excellent synergistic effects of adsorption and photodegradation with synergistic removal capacity up to 5.63 g/g. MX/ZnS/CC composite performed higher synergistic removal ability and better optical and electrical properties than pure MXene, ZnS, chitosan-cellulose material, and MXene/ZnS. After compounding, the synergistic removal percentage of dyes increased by a maximum of 309 %. MX/ZnS/CC composite mainly adsorbs anionic dyes through electrostatic interactions and catalyzes the generation of •O2-, h+, and •OH to degrade dyes, which has been successfully used to remove anionic dyes from environmental water, achieving a 100 % removal of 50 mg/L dye.

Decoration of Carbon Dots on Oxygen-Vacancy-Enriched S-Scheme TiO2 Quantum Dots/TiO2 Oxygen Vacancies Photocatalysts: Impressive Quantum-Dot-Sized Photocatalysts for Remediation of Antibiotics, Bacteria, and Dyes

Today, cleaning the environment using photocatalytic technology is one of the main research activities. In this study, carbon dots (C-dots) were anchored on oxygen-vacancy-enriched TiO2 quantum dots (QDs)/TiO2 oxygen vacancies (OVs) using a facile procedure. The resultant ternary TiO2 QDs/TiO2 OVs/C-dots photocatalysts with a quantum dot size of almost 4.55 nm were used for detoxification of aqueous solutions containing four antibiotics and three organic dyes as well as inactivation of two pathogenic bacteria, including Escherichia coli and Staphylococcus aureus, upon visible light. The degradation constant of tetracycline over the optimized TiO2 QDs/TiO2 OVs/C-dots nanocomposite reached 714 × 10-4 min-1, which was 17.3, 12.1, and 2.92 times higher than TiO2 QDs, TiO2 OVs, and TQDs/TOVs (1:1) materials, respectively. Effective separation of electron-hole pairs between TiO2 QDs and TiO2 OVs counterparts through decorated C-dots by an established S-scheme system was the main reason for boosted photocatalytic activity. With regard to the facile growth of wheat and lentil seeds in the treated solutions, it is hoped that the TiO2 QDs/TiO2 OVs/C-dots nanocomposite with significant stability could be used to clean up wastewaters.

A self-driven solar coupling system with TiO2@MXene cathode for effectively eliminating uranium and organics from complex wastewater accompanying with electricity generation

The inevitable organic matters in radioactive wastewater and contaminated waters pose great challenge in uranium recycling by traditional techniques. Here, a self-driven solar coupling system (SSCS), which was assembled by a TiO2 @MXene/CF cathode and a monolithic photoanode, was proposed for synergistically recycling uranium and degrading organics from complex radioactive wastewater, combining with electricity production. The TiO2 @MXene/CF was prepared via a simple annealing process with in-situ derived TiO2 nanoparticles decorated Ti3C2 MXene coated on carbon felt (CF). Under sunlight illumination, the photoanode captured electrons of organics, and drove electrons to the TiO2 @MXene/CF, which exhibited an exceptional UO22+ adsorption and reduction capacity because TiO2 nanoparticles provided plenty of surface hydroxyl groups for UO22+ adsorption, and the unique two-dimensional MXene facilitated the charge transfer. The SSCS with TiO2 @MXene/CF removed almost 100% UO22+ and organics with rate constants of ∼21 and ∼6.9 times those of the system with CF, accompanying with excellent power output (∼1000 μW·cm-2). The fixed uranium on TiO2 @MXene/CF was effectively reduced into insoluble UO2 (91.1%), and no obvious decay was observed after 15 repeated uses. This study proposes a multi-functional and easy-operated way for remediating radioactive wastewater and contaminated waters, and gives valuable insights in designing cathode materials for uranium reduction.