Adsorption Studies of Oil Spill Clean-up Using Coconut Coir Activated Carbon (CCAC)

The adsorption of crude oil from water by using Potassium hydroxide (KOH) prepared from coconut coir activated carbon CCAC_KOH was investigated by batch adsorption under varying parameters such as adsorbent dosage, contact time, initial oil concentration, temperature and agitation speed. The morphological modification significantly increased the hydrophobicity of the adsorbent, thus creating a CCAC with a much better adsorption capacity for crude oil removal having a maximum adsorption capacity of 4859.5 mg/g at 304 K as evidently proven by FTIR and SEM analysis. The experimental results showed that the percentage of crude oil removal increased with an increase in adsorbent dosage, contact time and decrease in initial oil concentration. The experimental isotherm data were analysed using Langmuir, Freundlich, Temkin, Toth, Sip and Redlich-Peterson isotherm equations and the best fitted isotherm model was Freundlich model with a high correlation coefficient (R² = 0.999). The kinetic data were properly fitted into various kinetic models with Pseudo-second order model showing best fit having a correlation coefficient (R² = 0.999) and Boyd model revealed that the adsorption was controlled by internal transport mechanism and film-diffusion was the major mode of adsorption. The crude oil adsorption was chemisorption and endothermic in nature (ΔH° = 134 KJ/mol.K) and the positive value of entropy (ΔS° = 0.517 KJ/mol.K) showed an increase in disorder and randomness at the adsorbent-adsorbate interface during the adsorption of crude oil from water. The decrease in Gibbs energy (ΔG°) with increasing temperature indicated an increase in the feasibility and spontaneity of the adsorption at higher temperatures. The prepared adsorbent showed significant capability to be used as a low-cost, re-generable and eco-friendly adsorbent in oil spill clean-up.