ABSTRACT
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.
ABSTRACT
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.
Subject(s)
Molybdenum , Nitrogen , Catalysis , Oxidation-Reduction , PeroxidesABSTRACT
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.