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Alaoui A.,Laboratoire Hydrometallurgie et Environnement | El Kacemi K.,Mohammed V University | El Ass K.,Laboratoire Of Metrologie Of Lenvironnement | Kitane S.,Laboratoire Hydrometallurgie et Environnement | El Bouzidi S.,Center Detudes Nucleaires Of La Maamoura Cnesten nitra
Separation and Purification Technology | Year: 2015

The electrochemical oxidation of methylene blue (MB) in aqueous solution was studied by galvanostatic electrolysis using MnO2 electrode as anode. The MnO2 electrode was prepared by electroplating method, and was characterized by X-ray diffraction (XRD), the cyclic voltammetry (CV) and amperometry j = f(t). This study has been done in synthetic media using sulfate sodium as electrolyte and thus only the contribution of the direct effect of electrolysis has been put into evidence. The electrochemical oxidation performance of the prepared electrode was investigated using MB as a model pollutant. UV spectroscopy and chemical oxygen demand (COD) measurements were conducted to study the kinetics of MB electrochemical degradation and the mineralization under different operating conditions. An experimental design methodology (Box-Behnken design) has been applied to determine the optimal experimental condition in term of effectiveness. The best conditions have been found after 120 min of electrolysis with Pt/MnO2 operated at pH ≈ 8 with a current density of 7 mA cm-2 in presence of <0.1 mol L-1 of sodium sulfate. In these conditions, higher than 90% of MB removal can be obtained with an abatement of slightly over 70% of COD. These results indicate that the suggested modified electrode was highly efficient in the treatment of effluents containing methylene blue dye with very slight effect of matrix. © 2015 Elsevier B.V. All rights reserved. Source

Alaoui A.,Laboratoire Hydrometallurgie et Environnement | El Kacemi K.,Mohammed V University | El Ass K.,Laboratoire Of Metrologie Of Lenvironnement | Kitane S.,Laboratoire Hydrometallurgie et Environnement | El Bouzidi S.,Center Detudes Nucleaires Of La Maamoura Cenm nitra
JOM | Year: 2015

The leaching capacity of olive mill wastewater (OMW) for pyrolusite mine tailings (MnO2) was evaluated using the Box–Behnken experimental design of response surface methodology. The selected test parameters include the concentration of sulfuric acid, the OMW dosage chemical oxygen demand (COD), the solid/liquid ratio S/L, and particle size. It was determined that the MnO2 dissolution increased with an increase in the sulfuric acid concentration and the OMW dosage, and with a decrease in the solid/liquid ratio. The particle size does not have significant influence on the manganese recovery. A quadratic polynomial model has been developed to predict the amount of manganese extraction from pyrolusite for other operating conditions that were not directly tested. The leaching ability was evaluated based on manganese recovery (Mn%) and the removal capability of chemical oxygen demand (COD%). The predicted values for the responses agreed well with experimental values; R2 (correlation coefficient) values for Mn% and COD% were 0.9602 and 0.9687, respectively. Within the design space, the optimum conditions for the lixiviation of MnO2 in terms of manganese recovery and COD removal were established and include [H2SO4] of 3 mol L−1, OMW in range of 23 g L−1 to 25 g L−1 COD, and pulp density in range of 90 g L−1 to 100 g L−1. Under these conditions, the response values generated by the model are Mn% ∼49% and COD% >40%. These values show good agreement with those obtained in the validation test. This study has demonstrated that it is possible to use the olive mill wastewater as a reductant agent to recover manganese from a pyrolusite mining residue. © 2015 The Minerals, Metals & Materials Society. Source

Alaoui A.,Laboratoire Hydrometallurgie et Environnement | Kacemi K.E.L.,Mohammed V University | Ass K.E.L.,Laboratoire Of Metrologie Of Lenvironnement | Kitane S.,Laboratoire Hydrometallurgie et Environnement
Transactions of the Indian Institute of Metals | Year: 2015

Understanding the mechanism that governs the leaching process is of major importance to optimize the various factors involved in the reaction; this article is devoted to this subject. The application of leaching process to extracting Mn from a manganese mine tailings was investigated using a software based design of experiments. The Box-Behnken experimental design was used to provide data for modeling and the variables of model were potassium oxalate concentration, solid-to-liquid ratio and sulphuric acid concentration. The recoveries of Mn are selected as response of design. The optimum condition under which the Mn recoveries are the highest is determined using statistical analysis and analysis of variance. A quadratic model with good adherence to the experimental data in the domain analyzed was developed, which was used to plot the response surface curves and to perform process optimization. The results showed that Mn recovery was 80 % under the optimum conditions: a ratio S/L = 50–70 (g L−1) approximately; also, sulfuric acid concentration is 1.1–1.3 M and oxalate concentration in range 0.35–0.45 M, time and temperature of the process were 30 min and 25 °C, respectively. The methodology employed allowed to evaluate and identify the effects and interactions of the considered variables with statistical meaning in the process response, i.e., the highest recovery of Mn after 30 min of reaction. © The Indian Institute of Metals - IIM 2015. Source

Alaoui A.,Laboratoire Hydrometallurgie et Environnement | EL Kacemi K.,Mohammed V University | EL Ass K.,British Petroleum | Darmane Y.,University Ibn Zohr | Kitane S.,Laboratoire Hydrometallurgie et Environnement
Transactions of the Institutions of Mining and Metallurgy, Section C: Mineral Processing and Extractive Metallurgy | Year: 2016

A kinetic study of the leaching of manganese mining residue by sulphuric acid and potassium oxalate has been investigated. The effects of the agitation speed, manganese ore particle size, acid concentration, oxalate concentration and temperature on the manganese dissolution rate was determined. The leaching rate is significantly influenced by the reaction temperature, and both concentrations oxalate and acid. The observed effects of the relevant operating variables on the leaching rates are consistent with a kinetic model for chemical control. The apparent activation energy for the leaching of pyrolusite has been calculated using the Arrhenius expression and was found to be (63.7 ± 2.9) kJ mol−1. The experimental results indicate a reaction order of 1.07 for [H2SO4] concentration and 0.96 for [K2C2O4]. It is concluded that the reductive leaching of pyrolusite with potassium oxalate in acid medium is controlled by chemical reaction. The rate expression associated with the dissolution rate of pyrolusite depending on the parameters chosen may be summarised as follows:s (Formula presented.) © 2016 Institute of Materials, Minerals and Mining and The AusIMM. Source

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