The adsorption of Ciprofloxacin (CPX) from aqueous solution by Pomegranate peels (POP) was investigated in a batch process. The influence of time (5-60 min) and CPX concentration (100-10,000 mg/L) on the adsorption ability of POP was studied. The POP was characterized by FTIR, scanning electron microscopy (SEM), and Zeta sizer. The kinetic of adsorption was analyzed by the pseudo-first-order and the pseudo-second-order kinetic equations using non-linear regression analysis. As well as non-linear regression analysis of Langmuir and Freundlich models were applied to specify the best non-linear curves, fitted to experimental data and estimate isotherm parameters. In order to assess the best-fit kinetic model or adsorption isotherm, three error analysis methods were used to evaluate the result of adsorption process, namely the sum of the squares of the errors (SSE), residual root mean square error (RMSE), and chi-square (χ2). On the basis of low three error analysis and high correlation (R2) of determination, it can be concluded that both the non-linear form of pseudo-second-order kinetic model and non-linear form of Langmuir are best suited to explain the adsorption of CPX onto POP. The maximum adsorption capacity for pomegranate peel as calculated by non-linear Langmuir curve was much higher than in previous work (999 mg/g) at natural pH (4-5) and 25 °C. The high adsorption capacity of POP makes them very low-cost and effective adsorbent materials for CPX from aqueous solution.
Keywords: Adsorption; Ciprofloxacin; Kinetics; Langmuir; Non-linear regression; Pomegranate peels.