Okparanma R.N., Ayotamuno M.J., Akor A.J., Igoni A.H.
Department of Agricultural and Environmental Engineering, Rivers State University of Science and Technology, P. M. B. 5080, Port Harcourt, Nigeria
Okparanma, R.N., Department of Agricultural and Environmental Engineering, Rivers State University of Science and Technology, P. M. B. 5080, Port Harcourt, Nigeria; Ayotamuno, M.J., Department of Agricultural and Environmental Engineering, Rivers State University of Science and Technology, P. M. B. 5080, Port Harcourt, Nigeria; Akor, A.J., Department of Agricultural and Environmental Engineering, Rivers State University of Science and Technology, P. M. B. 5080, Port Harcourt, Nigeria; Igoni, A.H., Department of Agricultural and Environmental Engineering, Rivers State University of Science and Technology, P. M. B. 5080, Port Harcourt, Nigeria
In this study, a comparative evaluation of first- and second-order kinetic models was carried out in order to evolve a better predictive model, as well as determine the limiting phenomenon, in the adsorption of chromium onto powdered activated carbon (PAC) during the tertiary treatment of the flocculation effluent of liquid-phase oil-based drill cuttings (LP-OBDC). The treatment of the LP-OBDC was done by mixing 1g of commercial PAC with 100ml of the flocculation effluent of initial chromium concentration (Co) of 5.01mg/l in a flask using magnetic stirring at 25°C. The residual concentration of chromium in the liquid phase, C (mg/l), was measured after different stirring times of 15, 60, 120, 180 and 1440 minutes. Then, the adsorption q (mg/g) was found for each period. Results show that equilibrium was attained within 60 minutes of contact time and the equilibrium concentration of the chromium (qe) was 3.94mg/g indicating that the PAC was able to adsorb 78.64% of the chromium at initial PAC concentration of 10g/l of effluent. The first-order rate constant, K1 was 9.84 x 10-5min-1 and the second-order rate constant, K2 was 0.3644g/mgmin. Using the first-order kinetics, the value of the equilibrium concentration of the chromium (qe) was deduced as 3.47 mg/g, whereas; the qe deduced with the second-order kinetics was 3.96mg/g. When compared with the value of the qe obtained experimentally (i.e. 3.94mg/g), it shows that experimental data fitted the second-order kinetics relatively better than the first-order kinetics (with R2 = 0.999998), indicating that the second-order kinetic model could be used to predict chromium adsorption in the treatment process. This result also indicates that the limiting phenomenon in the treatment process was more of mechanisms of adsorption than mass transfer resistance.