Strong coupling of super-hydrophilic and vacancy-rich g-C3N4 and LDH heterostructure for wastewater purification: Adsorption-driven oxidation.

Adsorption and wettability are crucial components of catalytic oxidation. To increase the reactive oxygen species (ROS) generation/utilization efficiency of peroxymonosulfate (PMS) activators, defect engineering and 2D nanosheet characteristics were used to regulate electronic structures and expose more active sites. Two-dimensional (2D) super-hydrophilic heterostructure by connecting cobalt species modified nitrogen vacancy-rich g-C3N4 (Vn-CN) and LDH (Vn-CN/Co/LDH) with high-density active sites and multi-vacancies, as well as high conductivity and adsorbability, to expedite ROS generation. The degradation rate constant of ofloxacin (OFX) was 0.441 min-1 via the Vn-CN/Co/LDH/PMS system, which was 1-2 orders greater than in the previous studies. Confirmation of the contribution ratios of various reactive oxygen species (ROS), SO4·- and 1O2 in bulk solution, O2·- on the catalyst surface was the most abundant ROS. The catalytic membrane was constructed utilizing Vn-CN/Co/LDH as the assembly element. The 2D membrane achieved the continuous effective discharge of OFX in the simulated water after 80 h/4 cycles of continuous flowing-through filtration-catalysis. This study provides fresh insights into designing a PMS activator for environmental remediation activated on demand.

Interfacial engineering of vacancy-rich nitrogen-doped FexOy@MoS2 Co-catalytic carbonaceous beads mediated non-radicals for fast catalytic oxidation.

How to accelerate the Fe3+/Fe2+ conversion and fabricate recyclable iron-based catalysts with high reactivity and stability is highly desired yet challenging. Herein, vacancy-rich N@FexOy@MoS2 carbonaceous beads were firstly developed via employing sodium alginate, molybdenum disulfide (MoS2), and Fe-ZIFs through sol-gel self-assembly, followed by in-situ growth and pyrolysis strategies. As expected, A series of characterizations reflected that N@FexOy@MoS2 had high dispersibility and conductivity for fast mass and electron transport, and MoS2 as co-catalyst accelerated the circulation of Fe3+ to Fe2+ that attained 99.4% (0.345 min-1) norfloxacin degradation via PMS activation in a synergistic ''adsorption-driven-oxidation'' process, which much outperformed those of pure MoS2 (32.4%) and N@FexOy powder catalyst (45.3%). Moreover, confined Fe species, graphitic N, pyrrolic N, pyridinic N, and sulfur/oxygen vacancies were found as highly exposed active sites that contributed to the activation of PMS to dominate non-radicals (1O2 and O2·-) and other radicals following a contribution order 1O2 > O2·- > SO4·- > ·OH. More importantly, a fluidized-bed catalytic unit was evaluated and maintained the continuous zero discharge of NX. Overall, this study offered a generally applicable approach to fabricate removable Fe-based catalysts for contaminants remediation.

2D confinement freestanding graphene oxide composite membranes with enriched oxygen vacancies for enhanced organic contaminants removal via peroxymonosulfate activation.

Introducing membrane filtration into advanced oxidation processes to decrease energy and cost consumption has been considered as a promising direction in environmental remediation. In this work, we firstly developed a kind of novel lawn-like Fe2O3@Co0.08Fe1.92@nitrogen-doped reduced graphene oxide@carbon nanotube composites (FeCo@GCTs) through in-situ pyrolysis of self-assembly of Prussian blue analogues and GO, followed through a vacuum-assisted filtration strategy to fabricate 2D confinement freestanding GO composite membrane. Electrochemical analysis and H2-TPR revealed the superiority of FeCo@GCTs as ideal electron acceptor, and this unique lawn-like structure concentrated active sites with a confined space and enriched oxygen vacancies that realized 98.5% (0.128 min-1) sulfamethoxazole degradation via peroxymonosulfate activation, and accelerated the reduction of Cr(VI). Owing to the increasing interlayer spacing of GO nanosheets, the permeation flux of FeCo@GCTs/GO membrane has not only been attained to 487.3 L·m-2·h-1·bar-1, which was more than 7.5-fold of GO membrane (64.6 L·m-2·h-1·bar-1), but also achieved the synergistic membrane filtration and catalytic degradation of pollutants. Furthermore, scavenger experiments and EPR tests were conducted to confirm the active radicals, of which SO4·- and 1O2 were responsible for SMX degradation. Therefore, these features demonstrated great potential for the fabricated 2D confinement catalytic membrane with enriched oxygen vacancies in wastewater purification.