Facile one-step preparation of Co and Ce doped TiO2 in visible light PMS activation for PAHs degradation

Efficient Photocatalytic Activation of Peroxymonosulfate by Cobalt-Doped Oxygen-Vacancies-Rich BiVO4 for Rapid Tetracycline Degradation

In this work, cobalt-doped oxygen-vacancies-rich BiVO4 (Co/BiVO4-Vo) was successfully synthesized for the degradation of tetracycline (TC) by activated peroxymonosulfate (PMS) under visible light. The morphologies, microstructures, and optical properties of the photocatalysts were analyzed in detail. Co/BiVO4-Vo exhibited significantly enhanced degradation, removing 92.3% of TC within 10 min, which was greater than those of pure BiVO4 (62.2%) and oxygen-vacancies-rich BiVO4 (BiVO4-Vo) (72.0%), respectively. The photogenerated charge separation and transport properties were explored through surface photovoltage (SPV), photoluminescence spectrum (PL), and UV-vis diffuse reflectance spectroscopy (UV-vis DRS) measurements. Additionally, an in-depth investigation was conducted on the photocatalytically assisted advanced oxidation processes based on SO4•- (SR-AOPs) for the degradation of organic pollutants. The experimental results showed that the introduction of oxygen vacancies and Co doping achieved an effective separation of photogenerated carriers, which could accelerate the cycling between Co3+ and Co2+ and further activate PMS. The results of free radical capture experiments and electron spin resonance (ESR) experiments showed that reactive oxygen species (ROSs) such as 1O2, •O2-, and SO4•- played a dominant role in the removal of pollutants. This work provides a novel insight into the further development of efficient and rapid PMS photoactivators for environmental remediation of water bodies.

Enhanced Degradation of Levofloxacin through Visible-Light-Driven Peroxymonosulfate Activation over CuInS2/g-C3N4 Heterojunctions

In this work, the heterojunctions of CuInS2 embedded in the g-C3N4 materials (xCuInS2/g-C3N4, abbreviated as xCIS/GCN) was successfully prepared for peroxymonosulfate (PMS) activation under visible light. The catalysts are characterized by different techniques, such as XRD, FTIR, SEM, TEM, and UV-vis. The unique heterojunction composites can suppress the recombination of photogenerated pairs. The catalytic results showed that the 3CIS/GCN exhibited excellent catalytic levofloxacin (LVF) degradation efficiency, while more than 98.9% of LVF was removed in 60 min over a wide pH range. SO4•-, O2•-, OH•, and 1O2 were verified as the main reactive species for LVF degradation via the quenching experiments and electron paramagnetic resonance technology (EPR). The synergetic effect of xCIS/GCN, PMS, and visible light irradiation was discussed. The possible LVF degradation pathway was proposed through byproducts analysis (LC-MS). Moreover, the 3CIS/GCN/vis-PMS system has very low metal leaching. Owing to xCIS/GCN having good properties for PMS activation, it has potential applications for LVF or other hazardous pollutants degradation.

Targeted degradation of naphthalene by peroxymonosulfate activation using molecularly imprinted biochar

Polycyclic aromatic hydrocarbons (PAHs) in aquatic environments are threatening ecosystems and human health. In this work, an effective and environmentally friendly catalyst based on biochar and molecular imprinting technology (MIT) was developed for the targeted degradation of PAHs by activating peroxymonosulfate. The results show that the adsorption amount of naphthalene (NAP) by molecularly imprinted biochar (MIP@BC) can reach 82% of the equilibrium adsorption capacity within 5 min, and it had well targeted adsorption for NAP in the solution mixture of NAP, QL and SMX. According to the comparison between the removal rates of NAP and QL by MIP@BC/PMS or BC/PMS system in respective pure solutions or mixed solutions, the MIP@BC/PMS system can better resist the interference of competing pollutants (i.e., QL) compared to the BC/PMS system; that is, MIP@BC had a good ability to selectively degrade NAP. Besides, the removal rate of NAP by MIP@BC/PMS gradually decreased as pH increased. The addition of Cl- greatly promoted the targeted removal of NAP in the MIP@BC/PMS system, while HCO3- and CO32- both had an inhibitory effect. Furthermore, SO4•-, O2•- and 1O2 produced by BC activating PMS dominated the NAP degradation, and it was inferred that the vacated imprinted cavities after NAP degradation can continue to selectively adsorb NAP and this could facilitate the reusability of the material. This study can promote the research on the targeted degradation of PAHs through the synergism of biochar/PMS advanced oxidation processes and MIT.

Co/SBA-16 coating supported on a 3D-printed ceramic monolith for peroxymonosulfate-activated degradation of Levofloxacin

This study reports a simple method for anchoring dispersed Co nanoparticles on SBA-16 mesoporous molecular sieve coating grown on the 3D-printed ceramic monolith (i.e., Co@SBA-16/ceramic). The monolithic ceramic carriers with a designable versatile geometric channel could improve the fluid flow and mass transfer but exhibited a smaller surface area and porosity. The SBA-16 mesoporous molecular sieve coating was loaded onto the surface of the monolithic carriers using a simple hydrothermal crystallization strategy, which can increase the surface area of the monolithic carriers and facilitate the loading of active metal sites. In contrast to the conventional impregnation loading method (Co-AG@SBA-16/ceramic), dispersed Co₃O₄ nanoparticles were obtained by directly introducing Co salts into the as-made SBA-16 coating (containing a template), accompanied by conversion of the Co precursor and removal of the template after calcination. These promoted catalysts were characterized by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, Brunauer-Emmett-Teller theory, and X-ray photoelectron spectroscopy. The developed Co@SBA-16/ceramic catalysts exhibited excellent catalytic performance for the continuous removal of levofloxacin (LVF) in fixed bed reactors. Co/MC@NC-900 catalyst exhibited a ∼ 78% degradation efficiency in 180 min compared to that of Co-AG@SBA-16/ceramic (17%) and Co/ceramic (0.7%). The improved catalytic activity and reusability of Co@SBA-16/ceramic was because of the better dispersion of the active site within the molecular sieve coating. Co@SBA-16/ceramic-1 exhibits much better catalytic activity, reusability and long-term stability than Co-AG@SBA-16/ceramic. After a 720 min continuous reaction, the LVF removal efficiency of Co@SBA-16/ceramic-1 in a 2 cm fixed-bed reactor was stable at 55%. Using chemical quenching experiments, electron paramagnetic resonance spectroscopy, and liquid chromatography-mass spectrometry, the possible LVF degradation mechanism and degradation pathways were proposed. This study provides novel PMS monolithic catalysts for the continuous and efficient degradation of organic pollutants.

Highly efficient photodegradation of magnetic GO-Fe3O4@SiO2@CdS for phenanthrene and pyrene: Mechanism insight and application assessment

A novel magnetic core-shell Fe₃O₄@SiO₂@CdS embedded graphene oxide (GO) composite was prepared for the visible-light-driven photodegradation of high ring number polycyclic aromatic hydrocarbons (PAHs). The potential application of GO-Fe₃O₄@SiO₂@CdS was evaluated through the photodegradation of phenanthrene and pyrene in deionized water, tap water, and lake water, respectively. It was found that GO-Fe₃O₄@SiO₂@CdS could remove 86.4 % of phenanthrene and 93.4 % of pyrene, suggesting its potential for the degradation of high-ring number PAHs. The density functional theory (DFT) calculations demonstrate that pyrene has more active sites attacked by free radicals. The photoelectrochemical measurement and quenching experiments indicate that GO can transfer photoelectrons efficiently, resulting in the crucial radicals (O₂^-, OH and ¹O₂). More importantly, the photocatalytic activity kept almost constant during five cycles, confirming the significant anti-photocorrosion of GO-Fe₃O₄@SiO₂@CdS. This work provides some new insights into the removal of PAHs with high-ring numbers in the natural water environment.