Investigation of the adsorption performance of cationic and anionic dyes using hydrochared waste human hair

In this study, waste human hair was converted into hydrochar using the subcritical water medium for the first time. The produced hydrochar from waste human hair (WHH) was employed as an adsorbent for Reactive Red 180 (RR180) and Basic Red 18 (BR18) removal from the aqueous solutions. The adsorption processes were optimized by studying the affecting factors. As a result of the optimization process, the maximum RR180 removal occurred at pH 2, WHH dose of 1 g/L, and at a time of 60 min. For BR18, the best conditions were pH 8, WHH dose of 1 g/L, and time of 60 min. Langmuir and Freundlich models were used to study the adsorptions isotherms. Langmuir isotherm described the RR180 adsorption, while Freundlich had the best fit data for BR18 adsorption. The kinetic studies showed that the adsorptions of RR180 and BR18 were represented by the pseudo-first-order and Elovich models, respectively. Also, the thermodynamic results ensured that the adsorption process occurred spontaneously in nature.