| Summary: | Current environmental policies aim to reduce the levels of toxic substances in aquatic ecosystems and to promote the water reuse after appropriate treatment of wastewaters. Chromium is a hazard element present in effluents of various industries that should be reduced to achieve the objectives of these policies. New materials and low-cost techniques of high efficiency in the removal of chromium have been developed in the recent years. Most of the reported research concerns the use of surface functionalized nanomaterials for sorption of chromium dissolved either in synthetic or mono-elemental spiked solutions, and with unrealistic concentrations of chromium (since very high concentrations allow experimental procedures not to have problems with contamination or quantification). The present work compiles the research undertaken so far on the application of various nanomaterials in the treatment of chromium contaminated waters. On the basis of this literature review, major factors influencing the removal efficiency are examined and gaps of knowledge are identified. Magnetic nanomaterials have gained interest as sorbents by allowing the removal from the water of the materials containing contaminants by magnetic separation. In this work, magnetite, manganese ferrite and cobalt ferrite NPs were synthesized. The NPs were characterized using various techniques as follows: XRD, FTIR, TEM/STEM, Chemical Analysis, BET Method, Magnetic Studies and Isoelectric Point. Chromium removal by CoFe2O4 NPs with percentages above 95% was verified for the removal at pH 6 (from saline water and saline water with dissolved organic matter) and pH 10 (from ultra-pure, mineral, saline water and saline water with dissolved organic matter). This material proved to be promising for the treatment of wastewaters and industrial effluents. The kinetics of these adsorption experiments was evaluated using three kinetic adsorption models: pseudo-1st order, pseudo-2nd order and Elovich, evaluating which one of these mathematical models has a better adjustment to the experimental data. It was concluded that the interaction between Cr(III) and NPs is of chemical nature
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