Four common waste keratin biofibers (human hair, dog hair, chicken feathers and degreased wool) have been used as biosorbents for the removal of heavy metal ions from aqueous solutions. Different parameters of the biosorption processes were optimized in batch systems. For multiple-metal system, consisting on a mixture of eight metal ions (Cr(III), Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II)) , the total metal biosorption increased following the order: degreased wool > chicken feathers> human hair > dog hair. From the kinetic models tested, the pseudo-second order provided better results. Furthermore, biosorption isotherms of Pb(II) with the different keratin biofibers fitted properly Langmuir model. Surface morphology of the biosorbents were analyzed

Human hair natural fiber is mainly considered a waste in our society and its disposal can cause a major environmental impact. Hence, its valorization as a biosorbent of pollutants such as heavy metals is an interesting route to explore since it can reduce the amount of waste and at the same time contributes to the circular economy strategy. In this work, the ability of two kind of human hairs, used as biosorbents to remove Cr(III), Ni(II), Co(II), Mn(II), Cu(II), Zn(II), Cd(II) and Pb(II) ions from multiple-metal aqueous solutions, were examined and compared under different operating conditions. The influence of the time, pH and initial metal concentration on the metal uptake were studied. The biosorption kinetics and isotherm were also modeled observing that pseudo-second order kinetic model and Langmuir model fitted successfully experimental data. Moreover, biosorption process did not significantly modify the morphology and the chemical structure of the hair samples, which was proved by SEM and FT-IR studies. These kinetic results underline the satisfactory capacity of human hair for the biosorption of Pb(II), Cu(II) and Cr(II) (values up to 95%), pointing up the high efficacy of human hair for the removal of heavy metal ions from aqueous media.

Human hair is considered a ubiquitous waste product and its accumulation can cause environmental problems. Hence, the search for alternatives that take advantage of this waste as a new raw material is of interest, and contributes to the idea of the circular economy. In this study, chemically modified human hair was used as a low cost biosorbent for the removal of heavy metal ions from aqueous solutions. The effect of the contact time, the pH, and the biosorbent concentration on the biosorption process were investigated. Kinetic modeling indicated that the pseudo-second order kinetic equation fitted well with R2 > 0.999. Furthermore, the equilibrium data fitted the Langmuir adsorption isotherm at 295 K resulting in saturation concentrations of 9.47 × 10−5, 5.57 × 10−5, 3.77 × 10−5, and 3.61 × 10−5 mol/g for the sorption of Cr(III), Cu(II), Cd(II), and Pb(II), respectively. The biosorption process did not change the chemical structure and morphology of the hair, which was shown by FTIR and SEM. In addition, desorption experiments prove that 0.1 mol/L EDTA solution is an efficient eluent for the recovery of Pb(II) from the treated human hair. To summarize, treated human hair showed satisfactory biosorption capacity and can be considered as an effective biosorbent for the treatment of water with a low concentration of heavy metal ions.