SAWDUST-BASED ACTIVATED CARBON FOR MALACHITE GREEN REMOVAL: KINETIC AND THERMODYNAMIC STUDY

Abstract

Sawdust as a lignocellulosic solid waste, has been valorized and used as an adsorbent for the removal of Malachite green (MG) from aqueous solution. Impregnation in 20% KOH (SDK), and (NH4)2S2O8 (SDP) solutions then pyrolysis at 600°C for 3 hours were found to enhance the adsorption capacity of malachite green (MG) as a pollutant significantly relative to its inactivated state (SDU). The batch adsorption experiments resulted in a maximum adsorption capacity determined from Langmuir models of up to 434.78 mg/g, 238.10 and 200.0 for SDK, SDP and Merck respectively. Parameters influencing adsorption capacity such as contact time, adsorbent dosage, pH and temperature were studied. FT-IR analyses and iodine number determination were also performed to characterize the prepared adsorbents. Adsorption kinetics was found to comply with the pseudo second order with a good correlation factor (R2 = 0.99) with intraparticle diffusion as the rate determining steps. Thermodynamic analysis and temperature effects of the process confirm that the adsorption reaction was spontaneous (ΔGo<0) and endothermic (ΔHo>0). This study showed that sawdust as a waste could prove to be a very useful in removing toxic substances from the environment.