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In this study, a novel green tea/Mg-functionalized magnetic nano-adsorbent, denoted as GTE-MgO-Fe3O4 NPs, was developed and applied to the extraction of Methylene Blue (MB) from water-based solutions. The GTE-MgO-Fe3O4 NPs were synthesized by incorporating green tea extracts (GTE) and Mg species onto the surface of Fe3O4 nanoparticles using a hydrothermal method. Characterization analyses corroborated the successful functionalization of the Fe3O4 surface with GTE and Mg species, resulting in a superparamagnetic adsorbent equipped with abundant surface functional groups, which promoted MB adsorption and facilitated magnetic separation. Batch experiments revealed that different operating parameters had an impact on the adsorption behavior, such as adsorbent dosage, pH, coexisting ions, contact time, the initial MB concentration, and temperature. The investigations of adsorption kinetics and isotherms emphasized that the MB adsorption onto GTE-MgO-Fe3O4 NPs was an exothermic process dominated by chemisorption. The experimental adsorption capacity of GTE-MgO-Fe3O4 NPs for MB surpassed 174.93 mg g−1, markedly superior to the performance of numerous other adsorbents. Ultimately, the utilized GTE-MgO-Fe3O4 NPs could be effectively regenerated through acid pickling, retaining over 76% of its original adsorption capacity after six adsorption–desorption cycles, which suggested that GTE-MgO-Fe3O4 NPs was a suitable adsorbent for eliminating MB from effluent. [ABSTRACT FROM AUTHOR]

The removal of methylene blue (MB) from wastewater has attracted global concerns. In this study, polymer-functionalized magnetic nanoparticles for MB removal, Fe3O4@SiO2-MPS-g-AA-AMPS (FSMAA), were successfully synthesized by grafting acrylic acid (AA) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) on the surface of vinyl-modified Fe3O4@SiO2. With various characterization techniques, it was confirmed that the obtained FSMAA had a core–shell structure, a good magnetic property, and plenty of functional groups on its surface. MB adsorption experiments showed that the adsorption capacity of FSMAA was notably enhanced as the grafted monomer concentration and solution pH were increased. The adsorption kinetic data and isothermal data were well described by the pseudo-second-order kinetic model and the Langmuir model, respectively. The maximum adsorption capacity of FSMAA was 421.9 mg g−1 with grafted monomer concentration at 2.0 mol L−1 and solution pH at 9, much higher than those of other adsorbents stated in previous literatures. Based on XPS analysis, surface adsorption mechanism between FSMAA and MB was electrostatic interaction, hydrogen bonding, and hydrophobic interaction. Furthermore, FSMAA was effectively regenerated by acid pickling, and the remaining adsorption capacity was more than 60% after eight adsorption–regeneration cycles. All the results demonstrated the self-made FSMAA was a desirable adsorbent to remove MB from wastewater. [ABSTRACT FROM AUTHOR]