Activator effect on sawdust-based adsorbent efficiency: application to organic pollutants decontamination

Abstract

The aim of this study is to valorize available Sawdust as a ligno-cellulosic and locally abundant solid waste generated by different activities, via combined chemical and physical activations route and its application for the removal of hydroxybenzene as a toxic pollutant from aqueous solution in discontinuous mode. Enhancement of adsorption capacities by impregnating separately the powdered sawdust in acidic (phosphoric acid: 20%), basic (potassium hydroxide: 20%) and salty (Ammonium Persulfate: 0.1M) solutions then pyrolysis at 600°C for 1hour in tubular furnace resulting in SWDA, SWDB and SWDS- based adsorbents. The adsorptive rates of the obtained adsorbents were compared to the commercial activated carbon from Merck taken as a reference. The batch adsorption experiments resulted in a maximum adsorption capacities obtained from Langmuir model of up to 192.31, 123.56 and 109.89 and 133.33 mg/g for SWDA, SWDB, SWDS and Merck respectively. Conventional parameters influencing the removal capacity of the considered pollutant such as contact time, adsorbent dosage, pH, initial concentration and temperature were also studied. Samples characterization was carried out using Fourier-transform infrared spectroscopy (FTIR) analyses for functional groups determination, Iodine number test for porosity and scanning electronic microscopy (SEM) for microstructure examination of the samples.  Adsorption kinetics was found to comply with the pseudo second order with a good correlation factor (R2 > 0.99) with intra-particle diffusion as the rate determining steps. Thermodynamics of Hydroxybenzene adsorption process was spontaneous (ΔG o <0) and endothermic (ΔHo >0). This study showed that sawdust as a waste could prove to be a very efficient adsorbent in removing toxic substances from wastewater.