Potassium Hydroxide Activation as an Adsorbent for Equilibrium Isotherms of Hexavalent Chromium Adsorptions onto <i>Garcinia mangosteen</i> Shell

Abstract

The equilibrium isotherms of hexavalent chromium adsorption from water on potassium hydroxide (KOH) activated for mangosteen shell as an adsorbent by carbonization at 400 °C for 2 hours has been researched. The effective specific surface area of a biochar adsorbent is 164 m2/g, and its hexavalent chromium adsorption capacity can be encountered to be replied to on the pH 2.0 with initial feed concentration and temperature. The equilibrium adsorption isotherm models based on the Freundlich, Langmuir, Temkin, Hurkins-Jura, Halsay, Dubinin-Radushkevich, and Jovanovic models have been accompanied to compare the sorbate-sorbent system. The Freundlich isotherm model indicated a good fit with the experimental data for the system studied.