Removal behavior and mechanisms of reactive dyes from aqueous streams using engineered nanocomposites of Barona marble waste

The removal of dyes from wastewater has becomes a global issue since there is no penetration of sunlight into colored waters and this results in the ultimate reduction of aquatic life forms in addition to severe diseases to humans and significant problems to the environment. An attempt was made to synthesize economical and eco-friendly nanocomposites of high adsorption capacity for dye removal. For this purpose, waste material such as Barona marble was used as an adsorbent, and its adsorption properties were enhanced by treating it with sodium metasilicate, potassium ferricyanide, and their mixture. The prepared nanocomposites effectively removed Reactive red 120 and Reactive green 5 dyes by the adsorption process. The effect of different parameters such as initial dye concentration, adsorbent dosage, time, temperature, and pH was determined for adsorption process optimization. The equilibrium adsorption data were examined using the Langmuir, Freundlich, Temkin, Dubinin–Radushkevich, and Harkins–Jura isotherm models. According to the obtained results, the pseudo-first-order kinetic model best fitted to both dyes for all four composites, considering its high R2 values (R2 > 0.9). All the prepared nanocomposites were characterized by X-ray diffraction, scanning electron microscopy, and Fourier-transform infrared spectroscopy.