1 STUDY OF ADSORPTION OF SPILLED CRUDE OIL IN AQUATIC TERRITORYUSING MODIFIED BENTONITE CLAY

Abstract

Over the past decades, the removal of crude oil from water and wastewater has been of primary interest across the world. The locally available materials such as bentonite clay used as adsorbent in removing crude oil from aqueous solution are limited due to their low affinity to adsorb organic molecules such as crude oil constituent and the fact that the active site of bentonite is not uniform, hence the need to improve its adsorption performance through its modification into organoclay as a functional material for crude oil adsorption. It was in view of this that the study investigated theadsorption of spilled crude oil in aquatic territory using modified bentonite clay. The primary objectives of the study are to developed organo modified bentonite clay adsorbent, characterization of the developed adsorbent, determine the adsorption efficiency of the adsorbent in adsorption of crude oil and to investigate the adsorption isotherm, kinetics and thermodynamics of the developed adsorbent. The XRD diffractograms shows that quartz and albite content of the acid pretreated CTMABr modified bentonite clay is higher than untreated CTMABr modified bentonite, the surface morphology of the acid pre-treated CTMABr modified bentonite clay shows that oxalic acid pre-treatment has impact on the surface morphology of the modified bentonite clay with favourable channels and voids for adsorbing crude oil, the EDX analysis shows that acid pre-treated CTMABr modified bentonite clay has higher silica content with lower alumna, Fe, K, Ti and Ag content compared to raw bentonite and untreated CTMABr modified bentonite clay. The FTIR bands confirm the intercalation of CTMABr in the interlayer of galleries of the bentonite clay mineral in both acids pretreated and untreated CTMABr modified bentonite clay. Also, oxalic acid pretreatment of bentonite clay prior to modification with CTMABr result in higher adsorption capacity compared to untreated CTMABr modified and raw bentonite clay adsorbents.In addition, the effect of time, temperature, dosage, pH and initial concentration on the adsorption of crude oil shows a maximum removal efficiency of 97.52 %at 50 min, 98.05 % at 75 oC, 95.04 % at an adsorbent dosage of2g, 85.11 % at a pH of 9 and 83.87 % at aninitial concentration of 0.30 mg/Lfor acid pre-treated CTMABrmodified bentonite clay followed by those of untreated CTMABr modified bentonite clay while raw bentonite clay shows the least percentage adsorption and uptake. Furthermore, the adsorption of crude oil in raw bentonite, acid pretreated and untreated CTMABr modified bentonite clay shows that Redlich-Peterson isotherm (acid pre-treated CTMABr: β is 0.8076, A0.7091 is L/g, R2 is 0.9979; untreated CTMABr: β is 0.7886, A0.8461 is L/g and R2 is 0.9998; raw bentonite: β is 0.8135, A2.1285 is L/g and R2 is 0.9992), followed by Freundlich (acid pre-treated CTMABr: 1/n is – 0.2989, Kf is 1.3772 is L/mg, R2 is 0.9871; untreated CTMABr: 1/n is – 0.1265, Kf is 1.0752 is L/mg, R2 is 0.9832; raw bentonite: 1/n is –0.1622, Kf is 0.8378 is L/mg, R2 is 0.9611) and then Tempkin isotherm model best described the adsorption process while kinetic study shows that pseudo-second order kinetics models (acid pre-treated CTMABr: k2 is 0.54 is g/mg min, qe is 41.32mg/g; untreated CTMABr: k2 is 0.37 is g/mg min, qe is 31.25mg/g; raw bentonite: k2 is 0.05 is g/mg min, qe is 30.85mg/g) best describe the adsorption kinetics, followed by Intra-particle diffusion model, Elovich model, Boyd model and pseudo-first order kinetics model, and the adsorption process is diffusionally control and not kinetically. Hence, oxalic acid pretreated CTMABrorganomodified bentonite clay has good potential for crude oil andother pollutant removal from polluted water.