Maldonado Figueroa, Cristian

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    Synthesis and evaluation of alginate coated magnetite nanoparticles for the removal of dyes from wastewater
    (2020-12-11) Maldonado Figueroa, Cristian; Román Velázquez, Félix R.; College of Arts and Sciences - Sciences; Rivera Portalatín, Nilka M.; Meléndez, Enrique; Department of Chemistry; Morales Payán, José P.
    The discharge of wastewater from the dyeing industry is an environmental concern across the world. These effluents are considered highly toxic since they contain high concentrations of synthetic dyes, which are a great environmental concern due to their non-degradability and toxicity. A variety of procedures have been used for the remediation of synthetic dyes from water; however most have low efficiencies and are expensive. Adsorption has emerged as a promising remediation strategy, due to its high efficiency, and ease and low cost of operation. Adsorbent materials such as iron oxide nanoparticles are considered highly effective in the adsorption of synthetic dyes due to their easy functionalization, which can help enhance their adsorption capacity. In our study, we developed an eco-friendly iron oxide nanoparticles synthesis using sodium alginate as stabilizing agent and explored the material’s application in the adsorption of synthetic dyes from aqueous solutions. The synthesis was optimized by exploring different alginate to iron ratios, while parameters such as contact time, adsorbent amount and pH were evaluated in order to optimize the sorption uptake conditions of the methylene blue (MB) dye. In addition, the effect of co-existing ionic species in the adsorption process and the reusability of the adsorbent material were studied. The results showed that the presence of hydroxyl and carboxyl groups in the sodium alginate polymer act as a stabilizing agent and that iron oxide nanoparticles with diameters around 5-10 nm were successfully prepared (Alg-Fe3O4). Characterization and adsorption studies showed that the optimum alginate to iron ratio for the nanoparticles synthesis was 0.25. The determination of the point of zero charge (PZC) showed that the Alg-Fe3O4 nanoparticles has a negatively charged surface in a wide pH range and suggested the adsorption mechanism of the MB dye is governed by electrostatic attractions. The optimum sorption conditions were 60 minutes of contact time, 45 mg of adsorbent, and pH values above 5. The adsorption isotherm was well interpreted by the Langmuir model, with a maximum MB adsorption capacity of 114.87 mg/g at pH 7 and 127.98 mg/g at pH 9.2. The reusability of the nanoparticles was studied in a quantitative manner and it showed that the material could be effectively regenerated with methanol for further use. The adsorption capacity of the Alg-Fe3O4 nanoparticles was mainly affected by increasing concentration of monovalent and divalent cations, and the anionic methylorange (MO) dye. Adsorption of the MO dye was achieved by the synthetized Alg-Fe3O4 nanoparticles in the presence of MB. Overall, the results reported here provide new insights into the potential application of iron oxide nanoparticles, synthetized in the presence of sodium alginate, in the removal of synthetic dyes from wastewater.