Acetylated African Oil Bean Seed Pod For Crude Oil Spill Mop

6 Oil spill remediation has continued to be a challenge in the world today. Thus efforts are still been 7 made to develop more efficient oil spill mop up techniques. Natural adsorption with agricultural wastes, 8 which otherwise constitute environmental pollution, has become an attractive technique for oil spill 9 mop. Acetylation using acetic anhydride with iodine catalyst was carried out to improve the 10 hydrophobicity of African oil bean seed pod (AOBSP), which is a lignocellulosic material and as such 11 is naturally hydrophilic. Characterization of the raw and acetylated AOBSP were done using SEM, 12 BET and FTIR analyses. Batch crude oil sorption tests were performed using both the raw and 13 acetylated AOBSP. Isotherm, kinetic and thermodynamic studies were also carried out. FTIR analysis 14 showed evidence of successful acetylation of AOBSP and adsorption of crude oil onto the raw and 15 acetylated AOBSP. SEM and BET analyses showed improvement of the surface properties of AOBSP 16 by the acetylation process. The BET surface area increased from 226.4 m 2 /g for the raw AOBSP to 17 310.0 m 2 /g for the acetylated AOBSP. Oil sorption was found to be by monolayer coverage, with 18 monolayer sorption capacity of 5000mg/g and 12500mg/g for raw and acetylated AOBSP, respectively. 19 The rate- controlling mechanism for the sorption processes was chemisorption. Negative values of ΔG o , 20 ΔH o and ΔS o were obtained, showing that the sorption processes were feasible, spontaneous and 21 exothermic, with a degree of orderliness at the solid – mixture interface. The results obtained from this 22 study show that both raw and acetylated AOBSP are efficient oil sorbents


INTRODUCTION
Environmental pollution due to crude oil spillage occurs during the various stages of its extraction, 27 transportation, refining, storage, and use. Up to 100 million gallons of crude oil have been estimated to    where W0 and W1 are the weight of adsorbent before and after oil adsorption, respectively, and the 95 quantity W1 -W0 is the amount of crude oil adsorbed in grams. The amount of crude oil adsorbed per 96 unit weight of adsorbent, qe (mg/g), was calculated using Equation 2.
where Co is the initial crude oil concentration (mg/L), Ce is the equilibrium crude oil concentration 99 (mg/L), m is the mass of the adsorbent (g) and V is the volume of the solution (L).

100
Kinetic study 101 Three well known kinetic models were employed to study the kinetics of the oil adsorption. These are 102 the pseudo first order, pseudo second order and intraparticle diffusion models.

103
The pseudo first order kinetic model 104 The linearized pseudo first order equation is as shown in Equation 3 (Ho and McKay, 2000).
where qe is the amount of adsorbate adsorbed at equilibrium (mg/g), qt is the amount of adsorbate 107 adsorbed in mg/g at time t (min), and k1 is the pseudo first order reaction rate constant (min -1 ). A plot 108 of ln (qe -qt) versus t gives a straight line graph yielding k1 and qe from its slope and intercept, 109 respectively.

110
The pseudo second order kinetic model 111 The where Kid is the rate constant of intraparticle diffusion (mg/(g·min 0.5 )), t 0.5 is the square root of the time, 122 and C is the intercept.

123
Isotherm study 124 Two popular isotherms were used to study the equilibrium of the oil adsorption process. They are 125 Langmuir isotherm and Freundlich isotherm.   and 10 indicate favourable adsorption (Karthikeyan et al., 2003).

146
Thermodynamic studies 147 The standard Gibbs free energy changes for the adsorption processes was determined using van't Hoff where Cs is the amount of adsorbate adsorbed on the sorbent at equilibrium.

155
The changes in enthalpy, ∆H o (kJ/mol), and entropy, ∆S o (kJ/mol.K) were calculated using Equation

161
The characterizing properties of the crude oil are shown in Table 1. The crude oil is less dense than water and so floats on water. It belongs to the class of medium crudes

194
The FTIR spectra for raw and acetylated AOBSP, before and after crude oil sorption, are shown in 195 Figures 3 -6, respectively. The assignment of functional groups are shown in Table 3.    Throughout the adsorption period, the acetylated AOBSP had higher sorption capacity than the raw 241 AOBSP. At 15minutes of contact time, the sorption capacities of the raw and acetylated AOBSP were 242 7.430 g/g and 11.795 g/g, respectively. The higher sorption capacity of the acetylated AOBSP is likely 243 due to its higher surface area and pore volume, as observed in surface area analysis, which provides

RAOBSP AAOBSP
to be 3.97 and 6.65 g/g, respectively, while raw and acetylated oil palm empty fruit bunch had values 247 of 3.04 and 6.48 g/g, respectively.
248 Effect of temperature 249 The effect of temperature on the crude oil sorption capacity of the raw and acetylated AOBSP is shown 250 in Figure 8.

256
The decrease in the crude oil sorption capacity with increasing temperature also shows that the .52 g/g and 3.25g/g for 1-day and 7-day weathered crude oil, respectively.

RAOBSP AAOBSP
As sorbent dose increased from 0.2g to 1g, amount of crude oil adsorbed on both the raw and acetylated 271 AOBSP increased from 0.734mg/g to 3.113mg/g and 1.869mg/g to 6.860mg/g, respectively. This may and acetylated corn cob to decrease from 4000mg/g to 1000mg/g and 2300mg/g to 500mg/g, 280 respectively on increasing the sorbent dosage from 0.5g to 2g.

281
Kinetic study 282 The pseudo first order, pseudo second order and intraparticle diffusion data for crude oil adsorption on The kinetic parameters are shown in Table 4.  For adsorption on both raw and acetylated AOBSP, the pseudo-second order rate constant is lower than 304 the pseudo-first order rate constant. This shows that chemisorption is the slowest step, and so is the 305 rate-controlling step in the sorption process. This is supported by the fact that for adsorption on 306 acetylated AOBSP, the pseudo-second-order R 2 value (0.9836) is higher than the pseudo-first-order R 2 307 value (0.9504). For adsorption on raw AOBSP the pseudo-first-order R 2 value (0.8621) is higher than 308 the pseudo-second-order R 2 value. However, the pseudo-second-order value (0.8307) is also high and 309 close to the pseudo-first-order value. Thus, it can be said that chemisorption is the rate-controlling 310 mechanism in the sorption of oil on both raw and acetylated AOBSP, with physisorption being partly 311 involved in the sorption process.   The isotherm parameters for the crude oil adsorption on raw and acetylated AOBSP are shown in Table   327 5. isotherm. This means that the adsorption of crude oil on both RAOBSP and AAOBSP are better The results of thermodynamic analysis of crude oil adsorption on the raw and acetylated AOBSP are 346 shown in Table 6.  showing that there was more efficient biosorption at lower temperature, which is supported by the