Synthesis and characterization of FSB@Fe3O4 composites and application in removal of indigo carmine dye from industrial wastewaters

The syntheses and characterization of fish scale biochar magnetic composites (FSB@Fe3O4) and their applications in the removal of indigo carmine dye from effluents are described. Preparation of the fish scale biochar magnetic composites, FSB@400 °C-Fe3O4, FSB@600 °C-Fe3O4, and FSB@800 °C-Fe3O4, was done following the chemical co-precipitation method. The adsorbents were characterized using peak optical absorbance, functional groups, magnetic strength, surface morphology, particle size, elemental compositions, surface charge, surface area, thermal stability, and crystalline phase, using ultraviolet-visible spectroscopy (UV-vis spec), Fourier transform infrared (FTIR) spectroscopy, vibrating sample magnetometry (VSM), transmission electron microscopy/scanning electron microscopy (TEM/SEM), energy dispersive X-ray (EDX), point of zero charge pH (pHpzc), Brunauer-Emmett-Teller (BET), thermo-gravimetric analysis (TGA), and powder x-ray diffraction (PXRD) techniques, correspondingly. The potential of magnetic composites for the abstraction of indigo carmine dye from wastewater was determined as a function of the initial concentration of indigo carmine dye, contact time, dye solution pH, adsorbent dosage, and solution temperature. The results demonstrated that the quantity (q) of indigo carmine dye adsorbed onto magnetic composites improved with a rise in initial dye concentration, adsorbent load, and solution temperature. Conversely, lower quantities of adsorbed dye were recorded at higher pH levels. The data fitted a pseudo-second-order kinetic model. The Langmuir isotherm gave the best fit (Langmuir>Freundlich>Redlich-Peterson>Toth>Hill>Sips>Temkin) suggesting a uniformly monolayer adsorption. Adsorption of environmental wastewater samples revealed that all the adsorbents can be used to effectively treat industrial wastewaters. The recycling data established that the adsorbents could be used for five consecutive cycles without significant loss of adsorption capacities.