Bio-sorptive remediation of crude oil polluted sea water using plantain (Musa parasidiaca) leaves as bio-based sorbent: Parametric optimization by Taguchi technique, equilibrium isotherm and kinetic modelling studies

This study investigated the potential of employing plantain leaves as a natural bio-based sorbent for crude oil spill polluted seawater remediation. Type L₉(3⁴) Taguchi orthogonal array technique was used to evaluate the effect of four independent bio-sorption factors at three different levels (crude oil initial concentration (X₁ 7.8, 11.5 and 15.6 g/L), seawater-crude oil temperature (X₂ 25, 35 and 45 °C), bio-sorbent dosage (X₃ 1, 2 and 3 g) and bio-sorbent particle size (X₄ 1.18, 2.36 and 4.72 mm) on two response indices (bio-sorption efficiency (%) and bio-sorption capacity (g/g)). Taguchi optimization technique, numerical-desirability index function optimization technique and a proposed optimization method were utilized to determine the optimum bio-sorption factors needed for the optimum bio-sorption efficiency and bio-sorption capacity. The results demonstrated that the crude oil bio-sorption efficiency of the plantain leaves was significantly influenced by X₁, X₃ and X₄ and the bio-sorption capacity was mainly influenced by X₁ and X₃. The optimum bio-sorption efficiency and the optimum bio-sorption capacity were 99.05 % and 12.82 g/g, respectively, obtained at optimum combination of factors and levels of X₁₁ (7.8 g/L), X₃₃ (3 g) and X₄₁ (1.18 mm) for bio-sorption efficiency and X₁₃ (15.6 g/L) X₃₁ (1 g) for bio-sorption capacity. The Freundlich and Dubinin-Rudeshkevich isotherm models best explain the equilibrium bio-sorption data, while the pseudo-second order kinetic model best describes the bio-sorption kinetics. The bio-sorptive remediation mechanism followed dual mechanism of physical and chemical bio-sorption and the mass transfer controlled by film diffusion. The maximum bio-sorption capacity (K_f) was 14.0 gg^-1.