Recovery of Mn-Zn ferrite from waste batteries and development of rGO/Mn-Zn ferrite nanocomposite for water purification

Photocatalytic Materials Obtained from E-Waste Recycling: Review, Techniques, Critique, and Update

Waste-derived materials obtained from the recovery and recycling of electronic waste (e-waste) such as batteries and printed circuit boards have attracted enormous attention from academia and industry in recent years, especially due to their eco-friendly nature and the massive increment in e-waste due to technological development. Several investigations in the literature have covered the advances achieved so far. Meanwhile, photocatalytic applications are especially of interest since they maintain mutual benefits and can be used for H2 production from solar water splitting based on semiconductor processing as a proper environmentally friendly technique for solar energy conversion. In addition, they can be utilized to degrade a variety of organic and non-organic contaminations. Nonetheless, to the best of the authors’ knowledge, there has not been any comprehensive review that has specifically been focused on e-waste-derived photocatalytic materials. In this regard, the present work is dedicated to thoroughly discussing the related mechanisms, strategies, and methods, as well as the various possible photocatalysts synthesized from e-wastes with some critiques in this field. This brief overview can introduce modern technologies and promising possibilities for e-waste valorization, photocatalytic processes, and new photocatalytic degradation methods of eco-friendly nature. This paper discusses various e-waste-obtained photocatalytic materials, synthesis procedures, and applications, as well as several types of e-waste, derived materials such as TiO2, ZnO, indium tin oxide, and a variety of sulfide- and ferrite-based photocatalytic materials.

Synthesis, Structure, and Antimicrobial Performance of NixZn1−xFe2O4 (x = 0, 0.3, 0.7, 1.0) Magnetic Powders toward E. coli, B. cereus, S. citreus, and C. tropicalis

The active development of water purification functional materials based on multicomponent spinel ferrites makes it necessary to search for new efficient methods of obtaining initial nanostructured powders. In this study, a two-stage method for the synthesis of perspective pollutant absorption agents based on NixZn1−xFe2O4 (x = 0, 0.3, 0.7, 1.0) spinel ferrites are proposed and implemented. The approach is based on the synthesis of the initial powder using the solution combustion method and its subsequent thermal treatment in the air. It was found that synthesized samples are single-phase Ni-Zn ferrites with an average crystallite size of 41.4 to 35.7 nm and a degree of crystallinity of ~95–96%. The analysis of antimicrobial activity against four diverse test-cultures: Escherichia coli ATCC 11229 (non-spore-forming gram-negative), Bacillus cereus ATCC 10702 (spore-forming gram-positive), Staphylococcus citreus NCTC 9379 (non-spore-forming gram-positive), and Candida tropicalis ATCC 750 (yeast) showed that almost all of the synthesized powders exhibit an advanced ability to inhibit the growth of the microorganisms mentioned above. The compositions obtained can be a perspective basis for both natural and wastewater purificators with magnetic separation ability and can find biotechnological and biomedical applications as promising antimicrobial materials.

Green synthesis of magnetically recyclable Mn0.6Zn0.4Fe2O4@Zn1-xMnxS composites from spent batteries for visible light photocatalytic degradation of phenol

Magnetic binary heterojunctions are a kind of promising photocatalysts due to their high catalytic activity and easy magnetic separation; however, their synthesis may involve high costs or secondary environmental impacts. In this work, the magnetically recyclable Mn_0.6Zn_0.4Fe₂O₄@Zn_1-xMn_xS (MZFO@Zn_1-xMn_xS, x = 0.00-0.07) photocatalysts are synthesized from spent batteries via a green biocheaching and egg white-assisted hydrothermal method. The as-synthesized photocatalysts have been comprehensively characterized in phase, morphology, texture, optics, photoelectrochemistry and photocatalytic activity. Characterization results indicate that the desired core-shell structure MZFO@Zn_1-xMn_xS composites are successfully synthesized, theirs absorption intensity in the visible light region is greatly enhanced compared to Zn_1-xMn_xS. In addition, doped Mn²⁺ in ZnS host lattice and the staggered bandgap alignment of MZFO and Zn_1-xMn_xS greatly enhances electron transfer and charge separation in the binary heterojunction system. The optimized MZFO@Zn_0.95Mn_0.05S shows the highest photodegradation performance toward phenol under the visible light irradiation, with a complete degradation of 25 mg L^-1 of phenol within 120 min, and its reactive kinetic constants is about 5.2 and 13.3 times higher than that of pure Zn_0.95Mn_0.05S and MZFO, respectively. Furthermore, the mechanism and pathways for the degradation of phenol are proposed. In addition, MZFO@Zn_0.95Mn_0.05S also exhibits a good reusability and high magnetic separation properties after 5 successive cycles. This new material has the advantages of low costs, simple reuse and great potential in application.