The pressure exerted on water supplies continues to increase as population density in urban areas. Additionally, in the state of Baja California, México, from the 48 groundwater aquifers five have salinization problems and seven have some degree of saltwater intrusion. This situation along with the dryness of the Cali-Baja (bi-national) region makes it necessary to take action on finding efficient ways to treat this type of water and make it accessible for the population.  The most popular technologies to improve water quality and aesthetics (such as alkalinity and hardness) are reverse osmosis, chemical precipitation, ion exchange, and electrochemical removal, but these processes often require a post-treatment adjustment, or they tend to be onerous.  In this paper we show iron-oxide magnetic nanoparticles and its chemical modification with chitosan by co-precipitation method with high potential to be used on ground water quality improvement. Five different types of magnetic chitosan were synthetized varying the amount of chitosan added to the nanoparticles, previous the nucleation of the magnetite. All the magnetic chitosan were studied and compared by DLS and Zeta potential to choose the most promising material for water treatment application.  The magnetic chitosan and raw magnetite were characterized previous their use by FT-IR, SEM/STEM, Zeta Potential, DLS, and TGA studies, proving the binding between magnetite and the biopolymer.  Studies of the magnetic materials on groundwater, from the ranch “Cacho” (Tijuana, B.C., México), were carried out to prove their effectiveness to remove alkalinity and hardness, and the results indicate that magnetic chitosan and raw magnetite proved to be effective for trap and remove carbonates salts from groundwater, and at the same time, we have the possibility of recovering them to further uses and reduce the operation cost. With these characteristics, we can classify magnetite and magnetic chitosan as sustainable nano softeners.

Magnetic chitosan as nano-softener to improve groundwater quality

ACS Fall 2021

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