Possibilité d’élimination des colorants par coagulation - floculation. Effet des paramètres réactionnels

Goudjil, Sarah (2023) Possibilité d’élimination des colorants par coagulation - floculation. Effet des paramètres réactionnels. Doctoral thesis, Faculté des Sciences et de la technologie.

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Abstract

Dyes are a very important element in the textile, cosmetics, paper, leather, pharmaceutical, food and other industries. Knowing that, the production and use of dyes result charged waste cause undesirable effects on human health and the environment. In order to protect our environment, we have tried to study the performance of the coagulation-flocculation process, by two coagulants often used in water treatment, which are aluminium sulphate and ferric chloride on the elimination of synthetic dyes. Different reaction parameters were also checked, such as the dose of coagulant, initial pH, initial dye concentration and the effect of coagulants aid. For the dyes, our choice is opted for three dyes of different charges (Methyl Violet (MV), Congo Red (RC) and Brilliant Green (VB)), in synthetic solutions (simple and binary systems) and on the discoloration of two different types of wastewater. The synthetic wastewater was collected in the Research Laboratory in Subterranean and Surface Hydraulics (LARHYSS), University of Biskra and another comes from a discharge of a paint production unit located in Barika, Wilaya of Batna. First, in the simple system, the best removal efficiencies were obtained by RC for both aluminium sulphate and ferric chloride. Whereas, the MV is the least eliminated whose yields did not exceed 35% for the two coagulants tested. Removal efficiencies increase with increasing initial dye concentrations. Optimum treatment pH indicated for both aluminium sulphate and ferric chloride that maximum MV removal was obtained at acidic (pH = 2) and basic (pH = 10) pH. VB had a significant abatement rate at pH equal to 8 and 10. Along with VB and MV, the best performance in terms of colour elimination for RC was achieved at pH between 4 and 6. The addition of coagulants aid (powder activated carbon, lime and polymer) in the presence of optimal doses of each coagulant improves the elimination yields even better, the effectiveness of which was maximum in some doses of coagulants aid, however, it is necessary take into account the harmful effect of lime on the increase of the pH of the treated solutions. Secondly, in the binary system, the dye removal efficiency (MV-VB) decreases in comparison with that in the simple system, while their removal increases in the presence of the anionic dye RC in the systems (MV-RC) and (VB-RC). While the elimination of RC decreases in the presence of MV and VB. The elimination of MV-VB increases with the increase in the initial dye concentration, the latter leads to a decrease in yields in the VB-RC system. In this binary system, the optimum pH of the treatment is obtained for acidic media whose pH ranges from 2 to 4 and for pH close to neutrality (pH between 5.3 (pH of the medium) and 6). Following all of our results, the application of the modelling was carried out using the statistical software Design Expert (RSM) whose empirical models were significant. The improvement of the results is possible by optimizing them with this software. Thirdly, the application of the coagulation-flocculation process to treat two types of wastewater as well as the elimination of RC, MV and VB found in the wastewater tested is globally higher than 50%, both for aluminium sulphate and that for ferric chloride. The optimum pH for wastewater treatment as well as for MV and VB is between 6 and 8.28 and that RC is very well eliminated in the different initial pH. The addition of coagulants aid improves the removal/decolourization yields which have reached 99%. The COD reduction rates and th

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