SOURCE:

Faculty: Physical Sciences
Department: Pure And Industrial Chemistry

CONTRIBUTORS:

Arinze-Nwosu, U. L.
Ajiwe, V. I. E.
Okoye, P. A. C.

ABSTRACT:

Oil spills have caused enormous environmental, health and ecological problems which affect humans and animals. There is need to develop natural sorbents which are biodegradable, cheap and readily available to clean up the crude oil spill. In line with this, five different agricultural wastes Borassus coir (BC), African breadfruit seed husk (ABF), corn husk (CH), plantain peel (PP) and plantain pseudostem (PS) were modified by acetylation to increase their hydrophobic properties thereby enhancing their oil sorption capacities in aquatic environment.. Mineral analysis was done by X-ray fluorescence (XRF), the extent of acetylation was investigated using Fourier Transform Infrared Spectroscopy (FTIR) and the surface morphology of the modified samples was determined using Scanning Electron Microscope (SEM). Result of XRF showed that all the five samples contained essential minerals like potassium and calcium in high proportion which was in agreement with other lingo-cellulosic biomass. The result of FTIR analysis suggested alterations in the chemical structure and subsequent increase in hydrophobicity of all the acetylated samples. The SEM micrographs showed that the acetylation process changed the physical configuration of the raw samples with the surface becoming rougher and more porous which makes oil entrance into the internal parts of the material easier and helpful in the sorption process. The kinetics of acetylation of CH, BC, ABF, PP and PS were optimally fitted by the pseudo- second order kinetic model with high R2 values of 0.9747, 0.994, 0.9637, 0.9875 and 0.9871 respectively. Kinetics analysis suggests intra-particle diffusion mechanism for BC while we could not conclude if the mechanism for the other four samples was either intra particle or liquid film diffusion models due to the very low R2 values. The kinetics of crude oil sorption for CH and BC were best fitted into the pseudo-second order kinetics with a very high R2 value of 0.9865 and 0.9867 and indicated the existence of intra-particle diffusion mechanism for the sorption of crude oil onto acetylated CH and BC. The crude oil sorption kinetics for acetylated ABF, PP and PS were best fitted into the pseudo-first order kinetics with a very high R2 value of 0.9898, 0.992 and 0.9732 and it equally indicated the existence of intra-particle diffusion mechanism all with good R2 values. The optimum acetylation conditions were found to be at 300C for all the five samples at 60 minutes using 1.2% catalyst for BC, 90 minutes using 0.2% catalyst for CH, 150 minutes using 0.2% catalyst for ABF, 60 minutes using 0.2% for PP and 60 minutes using 0.4% catalyst for PS. The water absorption capacity (WAC) studies gave the maximum values of 3.45 and 2.97 for raw and acetylated CH, 2.7 and 2.55 for raw and acetylated BC, 2.66 and 2.21 for raw and acetylated ABF, 2.90 and 2.32 for raw and acetylated PP, 2.97 and 2.58 for raw and acetylated PS all in g/g. These values confirmed that all the raw samples had their WAC reduced after acetylation which indicated a considerable increase in hydrophobicity. The crude oil sorption equilibrium data for CH, BC and ABF were best fitted into the Freundlich isotherms with high values R2. Langmuir isotherm model fitted adequately the experimental data of PP and PS with high R2. From the study, it was confirmed that acetylated sample of PS was the best sorbent material for oil spill clean-up with the highest sorption capacity of 13.39g/g, followed by BC at 9.92g/g, CH at 8.65g/g, PP at 8.40g/g while the sample with the least oil sorption capacity was Africa breadfruit seed husk at7.37g/g therefore the least suitable for oil spill mop up.