Enhanced Hydrophobicity and Oleophilicity for the Removal of Crude Oil from Aqueous Medium Using Modified Coconut Coir Activated Carbon (CCAC) and Empty Palm Fruit Bunch Activated Carbon (EPFBAC)
Crude oil spillage has tremendous environmental impacts and poses severe pollution problems worldwide due to the continuous activities and opera-tions in the oil and gas sector. This has resulted in the urgent need for cleanup techniques such as the use of natural adsorbents which are con-sidered a low-cost, readily available, efficient, eco-friendly, and easy-to-deploy method of handling oil spillage due to their high oil sorption capacity, high oil selectivity, oleophilic, enduring, reusability and biodegradable properties. Empty palm fruit bunch (EPFB) and coconut coir were used as precursors to produce activated carbon (modified with Lauric acid solution) for oil spill remediation. The influence of varying parame-ters was investigated using a batch experimental procedure and the results showed that the crude oil adsorption capacity increased with a corresponding increase in contact time, initial oil concentration, temperature, agitation speed, and particle size but a decrease in adsorbent dosage. The combination of surface morphological modification and hydrophobicity enhancement resulted in significantly improved adsorption capacity for crude oil removal (2710.0 mg/g and 4859.5 mg/g for EPFBACL.A and CCACL.A respectively), as evidenced by both FTIR and SEM analyses. The experimental isotherm data were analysed using various isotherm models and the bestfitted isotherm model was the Freundlich model with a correlation coefficient (R2 = 0.991 and R2 = 0.999) for EPFBL.A and CCACL.A respectively. The kinetic behaviour of the adsorption process was best de-scribed by pseudosecond order with R2 values of 0.970 and 0.999 for EPFBACL.A and CCACL.A respectively while Boyd model revealed that the adsorption was controlled by an internal transport mechanism and film diffusion was the rate-limiting step. The crude oil adsorption was chemi-sorption and endothermic owing to the positive enthalpy values (ΔH˚ = 183.890 KJ/mol for EPFBACL.A and ΔH˚ = 69.656 KJ/mol for CCACL.A), the positive value of entropy (ΔS˚ = 0.68 KJ/mol？K for EPFBACL.A and ΔS˚ = 0.295 KJ/mol？K for CCACL.A) suggested that the adsorption process was accompanied by an increase in the degree of randomness or disorder at the interface between the adsorbent and the adsorbate. A temperature rise led to a decline in Gibbs energy (ΔG˚), suggesting that adsorption became more feasible and spontaneous at higher temperatures and the significant activation energies for EPFBACL.A (Ea = 183.889 KJ/mol) and CCACL.A (Ea = 69.656 KJ/mol) indicated the existence of a substantial energy barrier that must be overcome to initiate the reaction. The results from the prepared adsorbents showed the significant capability to be used as a low-cost, regenerable and eco-friendly adsor-bent in oil spill cleanup and is recommended to exploit its usage on a large scale.
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