Core-shell ZIF-67/ZIF-8-derived sea urchin-like cobalt/nitrogen Co-doped carbon nanotube hollow frameworks for ultrahigh adsorption and catalytic activities

The CoO-doped carbon nanotubes enhance electronic performance and effectively activate persulfate for the degradation of sulfafurazole

In recent studies, carbon nanotube (CNTs) materials and their composites have demonstrated remarkable catalytic activity in the activation of persulfate (PS), facilitating the efficient degradation of organic pollutants. In this study, a novel Co loaded carbon nanotubes (CoO@CNT) catalyst was prepared to promote PDS activation for the degradation of sulfafurazole (SIZ). Experimental results, the CNT as a carrier effectively reduces the leaching of cobalt ions and improves the electron transport capacity，whereas the introduced Co effectively activates the PDS, promoting the generation of highly reactive radicals to degrade SIZ. Under optimized conditions (a catalyst dose of 0.2 g/L, a PDS dose of 1 g/L and an initial pH = 9.0), the obtained CoO@CNT demonstrated favorable Fenton-like performance, reaching a degradation efficiency of 95.55% within 30 min. Furthermore, density functional theory (DFT) calculations demonstrate that the introduction of cobalt (Co) accelerates electron transfer, promoting the decomposition of PDS while facilitating the Co2+/Co3+ redox cycling. We further employed the environmental chemistry and risk assessment system (ECOSAR) to evaluate the ecological toxicity of intermediate products, revealing a significant reduction in ecological toxicity associated with this degradation process, thereby confirming its environmental harmlessness. Through batch experiments and studies, we gained a comprehensive understanding of the mechanism and influencing factors of CoO@CNT in the role of SIZ degradation, and provided robust support for evaluating the ecological toxicity of degradation products. This study provides a significant strategy for the development of efficient catalysts incorporating Co for the environmentally friendly degradation of organic pollutants.

An Updated Overview of Magnetic Composites for Water Decontamination

Water contamination by harmful organic and inorganic compounds seriously burdens human health and aquatic life. A series of conventional water purification methods can be employed, yet they come with certain disadvantages, including resulting sludge or solid waste, incomplete treatment process, and high costs. To overcome these limitations, attention has been drawn to nanotechnology for fabricating better-performing adsorbents for contaminant removal. In particular, magnetic nanostructures hold promise for water decontamination applications, benefiting from easy removal from aqueous solutions. In this respect, numerous researchers worldwide have reported incorporating magnetic particles into many composite materials. Therefore, this review aims to present the newest advancements in the field of magnetic composites for water decontamination, describing the appealing properties of a series of base materials and including the results of the most recent studies. In more detail, carbon-, polymer-, hydrogel-, aerogel-, silica-, clay-, biochar-, metal-organic framework-, and covalent organic framework-based magnetic composites are overviewed, which have displayed promising adsorption capacity for industrial pollutants.

Stable magnetic CoZn/N-doped polyhedron with self-generating carbon nanotubes for highly efficient removal of bisphenols from complex wastewaters

Bisphenols have extensively been found in various environmental matrices and caused public concerns due to their endocrine-disrupting potential. Herein, we developed a ZIF-67@ZIF-8-derived CoZn/nitrogen-doped carbon (CoZn/NC) as a robust adsorbent for bisphenols in wastewaters. The self-generating carbon nanotubes and the open metal sites provided sufficient adsorption sites. The Co component endowed the derivative with strong magnetism facilitating its separation from water. CoZn/NC exhibited exceeding water stability in pH 3 - 12 solution and withstood water up to 15 days. The great applicability of CoZn/NC was validated with 16 real wastewaters from different sources (recoveries exceeding 97.9%). Fast adsorption kinetics were observed with removal efficiencies above 96.5% within 1 min. The adsorption isotherms were well fitted with the Langmuir model, with adsorption capacities of 222, 200, 193, and 321 mg g^-1 for bisphenol A, bisphenol F, bisphenol S, and bisphenol AF, respectively. Variations in external conditions, including pH 3 - 9, humic acid (50 mg L^-1), and NaCl (0.1 mol L^-1), had negligible impacts on the adsorption process. The characterizations and density functional theory computation demonstrated that electrostatic, hydrophobic, π - π, and cation- π interactions are the driving forces in this system. The as-prepared CoZn/NC exhibits great promise in real wastewater treatment.

Removal of Chromium (VI) by a Magnetic Nanoscale Zerovalent Iron-Assisted Chicken Manure-Derived Biochar: Adsorption Behavior and Synergetic Mechanism

Using chicken manure as raw material to prepare activated carbon as a dispersant, a novel biochar-loaded nano-zerovalent iron composite (nZVI@CMBC) was developed and applied to remove hexavalent chromium, i.e., Cr(VI), in wastewater. The dispersion of nano-zerovalent iron (nZVI) particles on the surface of chicken manure–derived biochar (CMBC) successfully inhibited the aggregation of magnetic iron particles and effectively reduced the size of nZVI particles. The results demonstrated that under acidic conditions, the removal efficiency of Cr(VI) by the nZVI@CMBC composite could reach 124.12 mg g⁻¹. The pseudosecond-order kinetic model had a good agreement with the adsorption kinetics of the nZVI@CMBC composite, implying that the adsorption of Cr(VI) is based on the multi-layer chemical adsorption. Therefore, this study provides a new clue and strategy for removing Cr(VI) in wastewater.

Enhanced catalytic peroxymonosulfate activation for sulfonamide antibiotics degradation over the supported CoSx-CuSx derived from ZIF-L(Co) immobilized on copper foam

The CoS_x-CuS_x was firmly immobilized on copper foam (CF) substrate to fabricate supported CoS_x-CuS_x/CF using ZIF-L(Co)/CF as a self-sacrificing template, in which CF substrate played an important role in improving the adhesion between CF and target catalyst as well as the interfacial interaction between CoS_x and CuS_x. The CoS_x-CuS_x/CF performed well in catalytic peroxymonosulfate (PMS) activation, which can accomplish 97.0% sulfamethoxazole (SMX) degradation within 10 min due to the special structure and Co²⁺ regeneration promoted by S^2- and Cu⁺. The influences of pH, PMS dosage, catalyst dosage, co-existing anions and natural organic matter (NOM) on SMX removal were studied in detail. CoS_x-CuS_x/CF presented excellent catalytic activity and reusability, which might be fascinating candidate for real wastewater treatment. The possible pathway of SMX degradation was proposed, and the toxicity of the intermediates during the degradation process were evaluated. It is noteworthy that long-term continuous degradation of sulfonamide antibiotics was achieved using a self-developed continuous-flow fixed-bed reactor. This work demonstrated that CF as a substrate to fabricate supported catalysts derived from MOF had great potential in actual wastewater remediation.

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@Fe_xO_y@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@Fe_xO_y@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@Fe_xO_y 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.

Recent advances in cobalt-activated sulfate radical-based advanced oxidation processes for water remediation: A review

Sulfate radical-based advanced oxidation processes (SR-AOPs) have attracted increasing attention for the degradation of organic contaminants in water. The oxidants of SR-AOPs could be activated to generate different kinds of reactive oxygen species (ROS, e.g., hydroxyl radicals (OH), sulfate radicals (SO₄^-), singlet oxygen (¹O₂), and superoxide radicals (O₂^-)) by various catalysts. As one of the promising catalysts, cobalt-based catalysts have been extensively investigated in catalytic activity and stability during water remediation. This article mainly summarizes recent advances in preparation and applications of cobalt-based catalysts on peroxydisulfate (PDS)/peroxymonosulfate (PMS) activation since 2016. The review covers the development of homogeneous cobalt ions, cobalt oxides, supported cobalt composites, and cobalt-based mixed metal oxides for PDS/PMS activation, especially for the latest nanocomposites such as cobalt-based metal-organic frameworks and single-atom catalysts. This article also discussed the activation mechanisms and the influencing factors of different cobalt-based catalysts for activating PDS/PMS. Finally, the future perspectives on the challenges and applications of cobalt-based catalysts are presented at the end of this paper.