Optimization of oxytetracycline sorption onto iron modified montmorillonite

Aims: Iraqi montmorillonite was saturated with iron (III) to investigate the improvement in the adsorption efficiency towards the antibiotics represented by oxytetracycline Methods Design of Experiments was carried out to determine the effect of experimental conditions: initial oxytetracycline molarity concentration (0.1-1.0 mM), montmorillonite content (0.5 - 10 g/L) and the pH value of the solution (3-10) on the adsorption efficiency. Batch equilibration runs were also conducted to study the adsorption of OTC in aqueous solutions onto the modified clay mineral powder for 24 hours. The UV absorption of the residual material at 360 nm was employed to determine the remaining oxytetracycline after equilibration for 24 hours. The iron introduction into montmorillonite resulted in enhancement of adsorption efficiency towards oxytetracycline which may be related to the possibility of stable complex with Fe(III) to make a 1:3 complex with it. Results: On using the optimum conditions, a mathematical model simulating the operation for the treatment was obtained as follows: Eff % =-0.467+0.160 m + 0.839C_o +0.126 pH - 0.046 m.C_o + 0.041 C_o ² - 0.071 C_o.pH Experimentally the OTC concentration could be decreased from 0.5 down to 0.03 mM in synthetic wastewater at a pH value of 5.5 by sorption onto 6.85g.L^-1 clay (montmorillonite)/L. Conclusion: The treatment with iron allows the use of lower clay material to perform the OTC removal.