Valorization of human hair as methylene blue dye adsorbents

Abstract

The present study was aimed at evaluating the performance of human hair as adsorbents for methylene blue (MB) dye removal. Human hair was treated using 0.1 m potassium hydroxide (KOH) and 0.1 m nitric acid, and the adsorbents were characterized for specific surface area and surface chemistry. The basic-treated human hair adsorbent (BH) exhibits a specific surface area of 3.51 m2/g, which is relatively higher than the acid-treated (AH) and untreated (UH) counterparts. The equilibrium data of all adsorbents obeyed the S-shaped isotherm, suggesting a cooperative adsorption. The BH displays a maximum capacity of 13.5 mg/g, while a comparable capacity of 3.4 mg/g was recorded by AH and UH. The adsorption of MB by BH increased with increasing pH. Based on the equilibrium and kinetics data, the adsorption of MB onto BH is proposed to have the following mechanisms: (i) external diffusion, (ii) intraparticle diffusion, and (iii) cooperative adsorption. In addition, the MB adsorption at a concentration of 20 mg/l is endothermic and spontaneous with temperature increasing from 35°C to 55°C. A basic treatment of human hair using KOH yields a promising adsorbent for dye in wastewater treatment.