Production of activated carbon from oil palm empty fruit bunches for removal of cadmium

Abstract

Different method of preparations had been proposed by prior research studies to remove heavy metals from industrial wastewater. In this research, various PAC samples from oil palm empty fruit bunches have been prepared by physical activation using steam to study the varying operating parameters of activation temperature, activation time and steam flow rate using 2- level full factorial experimental design to screen for the best quality adsorbent. The prepared EFB samples were carbonized for 30 minutes using nitrogen gas, followed by activation with steam gas at different thermal activation temperature of 600, 750 and 900°C with steam flow rates 2.0, 3.0, 4.0 mL/min, and contact time at 15, 30 and 45 minutes respectively for the production of activated carbon. Series of batch laboratory experiments were conducted in order to investigate the feasibility of activated carbon –derived from oil palm empty fruit bunches for the removal cadmium from aqueous solution through the adsorption process. Assessment was carried out by studying the influence of removal of Cadmium due to pH, adsorbent dosage and agitation rate to select the optimum production conditions for the novel PACs. Based on the analysis of variance (ANOVA) and batch adsorption test, the results indicated that activated carbon derived from 900°C, steam flow rate- 2ml/min and activation time of 15 minutes had maximum adsorption capacity at 2 mins (0.273 mg/g) for the removal of cadmium (97.2 %), R2 = 0.999 in the aqueous solutions with a yield of 21.8% and correlation coefficient R2 = 0.992. The optimum PAC sample selected was investigated through adsorption tests on aqueous solution of cadmium using the adsorption isotherms such as Langmuir and Freundlich to evaluate or predict the adsorption characteristics. In the isotherm studies, the trend of Langmuir and Freundlich coefficients ( , , and n) were in agreement with cadmium initial concentration trend. Batch adsorption studies showed that equilibrium time of 2 mins of agitation at 150 rpm was needed for the adsorption of cadmium on the activated carbon during experiment. The regression coefficient (R2) showed that Langmuir isotherm (R2= 0.984) fits the result better than Freundlich isotherms (R2 = 0.950). The characterization of PACs produced was measured to evaluate its quality and the results showed that 900°C activation temperature, 15 minutes activation time and 2.0 ml/mins steam flow rate had a high surface area of 635.16m2/g. These characteristics were observed to have favoured 900°C activated temperature, 15 mins activation time and 2.0 ml/mins steam flow rate with respect to adsorption of cadmium. EFB based- PAC would be promising in such a way that the industrial oil palm solid residue would