Removal of a reactive dye using NaOH-activated biochar prepared from peanut shell by pyrolysis process

Firstly, biochar was produced using peanut shell wastes at 500°C under inert gas nitrogen by pyrolysis. Then, the biochar was activated with NaOH. Activated biochar produced was characterized by SEM, FTIR, elemental analysis and N2 adsorption. The activated biochar obtained was utilized as an adsorbent for the removal of remazol orange RGB (RO-RGB), a reactive dye, from aqueous solution by adsorption method. The effects of initial dye concentration (20, 50, 75, 100 and 150 mg L−1), solution temperature (20°C, 30°C, 40°C, and 50°C) and pH (3, 5, 7 and 9) on the adsorption were investigated at different contact times. The amounts of the dye adsorbed increased with increasing initial dye concentration and temperature while it was decreasing with increasing pH. The most percent adsorption was found as 94.49% under conditions studied. Adsorption followed the Langmuir and Freundlich isotherm models as well as the pseudo-second order kinetic model. A favorable adsorption was observed by means of a dimensionless equilibrium factor, an essential characteristic of the Langmuir isotherm. From the results of single-stage batch adsorption, the required biochar mass for 90% dye removal in 10 L dye solution was estimated as 124.61 g. Thermodynamic data indicated a spontaneous and endothermic adsorption.