Keratin nanoparticles obtained from human hair for removal of crystal violet from aqueous solution: optimized by Taguchi method

Developing the cheap but superior adsorbents is of importance for environmental applications. In this paper, the Taguchi experimental design was applied to establish the optimum condition for the removal of crystal violet (CV) dye using keratin nanoparticles obtained from human hair waste. The average diameter of keratin particles was found about 63.7 nm, using DLS. Effective factors on the removal of CV dye including pH, adsorbent dose, temperature and contact time were considered using an L₁₆ orthogonal array. The optimum condition was found to be pH = 9, adsorbent dose = 0.004 g, temperature = 25 °C and contact time = 10 h in the studied range for different parameters. ANOVA results indicated that the pH has the highest contribution percentage (75.97%) on the adsorption process. Moreover, the equilibrium data were well described by Freundlich Isotherm, indicating a multilayer adsorption process with a maximum adsorption capacity of 555.56 mg/g through an endothermic and spontaneous adsorption process that could be used for up to 5 cycles of adsorption process. The kinetic adsorption data were evaluated by different kinetic models, where the data followed a pseudo-second-order model with three steps of diffusion indicated by the intra-particle diffusion model. The obtained results clearly show the high potential of human hair-obtained keratin nanoparticles for removal of cationic dyes from wastewater.