Optimization of Mn removal from aqueous solutions through electrocoagulation.

Manganese (Mn) was removed from aqueous solutions through electrocoagulation using Al electrodes. Effects of initial Mn concentration (185-405 mg l), the input voltage (1-11 V), inter electrode distance (1-5 cm), and initial pH (2-11) on Mn removal were investigated. Experiments were designed with an orthogonal central composite design on the four variables using the response surface methodology. Analysis of variance was applied and the final Mn concentration was expressed by a mathematical equation. Optimum values of the four factors to get the highest removal were also obtained. As the results showed, electrocoagulation using Al electrodes was able to remove Mn from aqueous solutions efficiently. An equilibrium state was achieved within 195 min. The mathematical model was appropriate to describe experimental data with a high regression coefficient. Kinetics and isotherm data were described appropriately by pseudo-second-order and Langmuir models, respectively. The optimum operating conditions were obtained as pH 9, initial Mn concentration 360 mg l, inter electrode distance 2 cm, and input voltage 10 V. The highest removal efficiency was 92% which is considered a high value.