Production and characterization of activated corban from boabab fruit shell via chemical activation for the removal of phenol

Abstract

Palm oil mill effluent (POME) causes severe environmental pollution due to its high concentrated pollutants. One of the most effective treatment methods is the adsorption using the activated carbon (AC), which is considered as a solution to wastewater pollution problems but suffering from high cost due to its non-renewable sources. In this study, the potential of converting baobab fruit shells (BFS) into activated carbon was investigated as well as being used in treating POME for removal of the phenol. In this research, different chemicals (ZnCl2, H3PO4, KOH) were used as activating agents for the preparation of AC from baobab fruit shell, which were impregnated (1:1) followed by the carbonized at temperature 500°C for 1 h. The effects of these chemicals on the performances of the prepared activated carbons (yield, iodine number, adsorption properties) were investigated. The BFS-ACs characterized to investigate by using the different analytical approaches such as FTIR, SEM, and XRD. The results indicated that the KOH in terms of adsorption and efficiency showed better results than the ZnCl2 and H3PO4 for the removal of phenol, with a maximum adsorption capacity of 36.9 mg/g at a higher initial concentration (600 mg/L). The aim was to obtain optimum operating conditions for KOH-AC production for maximum phenol removal. KOH-AC samples were produced under varying the operating parameters of temperatures, activation times, and impregnation ratio using face centered central composite design (FCCCD) experimental design under response surface methodology (RMS). The optimum conditions to attain a removal percentage of 93.56 % were determined by employing the RSM. The results demonstrated that the activated carbon prepared at the activation temperature of 700°C for 60 minutes with an impregnation ratio of 1:2 showed the best adsorbent of phenol. KOH-AC was found comparable to the commercial-grade activated carbon. Characterization of the KOH-AC showed good quality adsorbent with highly active sites and well-developed pores with BET surface area of 1263.127 m2/g. Furthermore, an optimization study for the adsorption conditions of the selected optimum parameters for KOH-AC production was investigated using the RSM. The determining factors such as contact time, AC dose, pH, agitation speed was initially screened using 2-level factorial approach. The screening revealed that the effect of the above parameters was significant. Furthermore, the impact of these four operating parameters was investigated using the FCCCD technique. The results presented the optimum conditions for phenol removal from aqueous solution were found to be contact time of 15 min, KOH-AC dose of 3 g/L, pH 2, and agitation speed of 250 rpm. Phenol adsorption behavior were described by the Redlich-Peterson (R-P) isotherm model as well as the pseudo-second-order kinetics. The maximum adsorption capacity of phenol (qm) was 196.68 mg/g. An evaluation of the adsorption efficiency of the BFS based KOH-AC was examined in real wastewater as the palm oil mill final effluent (POME) using batch adsorption. It was found that BFS-AC is an efficient adsorbent for the removal of phenol from palm oil mill effluent (POME). Also, BFS-AC with bed height of 15 cm provided better eliminations of phenol with empty bed contact time (EBCT) of 9.9 minutes and carbon usage rate (CUR) of 1.74 g/L. The results obtained in this study have exposed the capability of BFS based AC in the removal of phenol and treating POME wastewater. Thus, this activated carbon can be a promising source for treating POME wastewater.