Since
the turn of the 21st century, water pollution has been a
major issue, and most of the pollution is generated by dyes. Adsorption
is one of the most commonly used dye-removal methods from aqueous
solution. Magnetic-particle integration in the water-treatment industry
is gaining considerable attention because of its outstanding physical
and chemical properties. Magnetic-particle adsorption technology shows
promising and effective outcomes for wastewater treatment owing to
the presence of magnetic material in the adsorbents that can facilitate
separation through the application of an external magnetic field.
Meanwhile, the introduction of activated carbon (AC) derived from
various materials into a magnetic material can lead to efficient organic-dye
removal. Therefore, this combination can provide an economical, efficient,
and environmentally friendly water-purification process. Although
activated carbon from low-cost and abundant materials has considerable
potential in the water-treatment industry, the widespread applications
of adsorption technology are limited by adsorbent recovery and separation
after treatment. This work specifically and comprehensively describes
the use of a combination of a magnetic material and an activated carbon
material for dye adsorption in wastewater treatment. The literature
survey in this mini-review provides evidence of the potential use
of these magnetic adsorbents, as well as their magnetic separation
and recovery. Future directions and challenges of magnetic activated
carbon in wastewater treatment are also discussed in this paper.
In this research, a facile co-precipitation method was used to synthesize pure and Mg-doped ZnO nanoparticles (NPs). The structure, morphology, chemical composition, and optical and antibacterial activity of the synthesized nanoparticles (NPs) were studied with respect to pure and Mg-doped ZnO concentrations (0–7.5 molar (M) %). X-ray diffraction pattern confirmed the presence of crystalline, hexagonal wurtzite phase of ZnO. Scanning electron microscope (SEM) images revealed that pure and Mg-doped ZnO NPs were in the nanoscale regime with hexagonal crystalline morphology around 30–110 nm. Optical characterization of the sample revealed that the band gap energy (Eg) decreased from 3.36 to 3.04 eV with an increase in Mg2+ doping concentration. Optical absorption spectrum of ZnO redshifted as the Mg concentration varied from 2.5 to 7.5 M. Photoluminescence (PL) spectra showed UV emission peak around 400 nm. Enhanced visible emission between 430 and 600 nm with Mg2+ doping indicated the defect density in ZnO by occupying Zn2+ vacancies with Mg2+ ions. Photocatalytic studies revealed that 7.5% Mg-doped ZnO NPs exhibited maximum degradation (78%) for Rhodamine B (RhB) dye under UV-Vis irradiation. Antibacterial studies were conducted using Gram-positive and Gram-negative bacteria. The results demonstrated that doping with Mg ions inside the ZnO matrix had enhanced the antibacterial activity against all types of bacteria and its performance was improved with successive increment in Mg ion concentration inside ZnO NPs.
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