Adsorptive behavior of biochar and zinc chloride activated hydrochar prepared from acacia leucophloea wood sawdust: Kinetic equilibrium and thermodynamic studies

Abstract

In the present study, two adsorbents, namely biochar (BC) and ZnCl2 activated hydrochar (ZAHC) are prepared from Acacia leucophloea wood sawdust. BC is prepared by direct pyrolysis of the sawdust at 700°C while ZAHC is prepared by two-stage process, which includes hydrothermal carbonization to produce hydrochar followed by chemical activation with ZnCl2. The structural properties of the adsorbents prepared are characterized by Fourier-transform infrared spectroscopy, Brunauer–Emmett–Teller surface area and point zero charge. The adsorption performance of the prepared BC and ZAHC toward anionic dye, acid blue 15 is evaluated by batch mode studies. The study shows that the isotherm data are found to fit with Langmuir and fairly with Freundlich and Temkin isotherms. Likewise, kinetics data are found to fit with the pseudo-second-order kinetic model. The adsorbents exhibit favorable surface area of 1,380 and 550 m2g–1 for ZAHC and BC respectively. Therefore they can be used as adsorbents for the removal of dyes from aqueous solutions.