Batch and fixed-bed column adsorption of crystal violet and safranin by zero-valent iron (nZVI) and nZVI-modified S. cerevisiae

Batch and continuous studies were conducted to examine the adsorption and degradation of zero-valent iron (nZVI) and nZVI-modified S. cerevisiae (magnetic yeast) to remove crystal violet (CV) and safranin (SF) from synthetic wastewater. The nZVI and magnetic yeast were characterized using FTIR, SEM, EDX, and BET analysis. pH, initial dye concentration, contact time, adsorbent dosage, temperature, ion selectivity, and the effect of ionic and cationic strength were examined. The adsorption equilibrium data are an excellent fit to the Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm models. Different adsorption kinetics were used to examine the removal process of CV and SF, which followed a pseudo-second-order model. Adsorption was spontaneous. The adsorption of CV and SF dyes by nZVI-alginate and magnetic biosorbent-alginate in a column was studied. Regeneration efficiency was 76-87% after two cycles.