Case Studies in Chemical and Environmental Engineering (May 2022)
Equilibrium isotherm modelling and optimization of oil layer removal from surface water by organic acid grafted plantain pseudo stem fiber
Abstract
This work is targeted towards addressing the crude oil pollution menace in Nigeria and other OPEC member countries where exploration and exploitation of crude oil causes oil spill in our environment. In order to achieve this, equilibrium, thermodynamics modelling and optimization of oil layer removal by activated plantain pseudo stem fiber has been demonstrated in this work. Plantain pseudo stem fiber adsorbent with well-ordered framework of porosity on the surface was prepared by esterification method of activation using organic acid. Effect of oil water ratio, pH and temperature were examined using batch adsorption studies. Scanning Electron Microscope and Fourier Transform Infrared spectrometer was used to ascertain the surface morphology and functional groups of the raw and treated plantain pseudo stem fiber. Thermodynamics and isotherm analysis of crude oil removal was studied using established equations. Optimization and modeling of the process parameters was done using response surface methodology and artificial neural network. Batch experiments revealed that the optimum removal of oil occurred at oil water ratio of 0.2g/100cm3 with 94.7% of oil removed. Scanning electron microscope analysis revealed the extent of changes on the surface of the composite after acid treatment. Disappearances of some functional groups occasioned by acid treatments were revealed by Fourier transform infrared spectrum analysis. Meanwhile, the activated plantain pseudo stem fiber exhibited high potential at a very low pH of 5 with 96.7% of crude oil removal. Thermodynamic studies revealed activation energy, change in enthalpy and change in entropy for irreversible pseudo-first order and pseudo-second order model as (20.51, 21.15, -0.121 KJ/mols) and (45.78, 33.59, -0.163 KJ/mols) indicating non-spontaneous process. Equilibrium modeling revealed that the composite material was highly matched to Temkin isotherm model with maximum adsorption capacity of 54.35mg/g. The adsorption capacity of 54.35mg/g is very close to 55.30mg/g reported in literature for standard adsorbent (commercial zeolite). Optimization of the process revealed the optimum conditions as 50 mins, 90 °C and 0.2 g. At this point, the theoretical oil removal was 98.61% which was experimentally validated as 98.56%. Response Surface Methodology and Artificial Neural Network adequately predicted the oil removal with correlation coefficient >0.97. Therefore, results obtained from this investigation has shown that esterified plantain pseudo stem fiber composite is an efficient, economic viable and sustainable adsorbent and suggested the production of the adsorbent in commercial quantity since the process of adsorption highly matched with the standard models.
