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| Author | Methodology | Main parameters’ effects discussed | Conclusions | Remarks |
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| Johnson and Winnick [18] (1999). | (i) An AEM process is developed for recovery of chlorine from gaseous HCl, but here chloride ions migrate across the molten salt electrolyte saturated membrane. | (i) In free electrolyte (no membrane) trials, conversion and current efficiency were determined as a function of current density, required cell voltage, and feed gas flow rate.
(ii) At single-cell membrane, cross cell potentials at different feed rates are studied. | (i) This study shows that electrochemical membrane separation is a feasible alternative for the removal of chlorine from HCl at reasonable voltages, high conversion. | (i) This paper is more of a feasibility study.
(ii) Nothing in regard to power consumption or process economics is said. |
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| Vidakovic-Koch et al. [10] (2012). | (i) Polymer electrolyte membranes have broad applications; in this review emphasis is upon the application of Nafion membranes for chlorine recycling. | (i) The Nafion membrane has role of a separator and a solid electrolyte.
(ii) Proton transport, mechanical stability of membrane, and influence of dispersion medium and its relevance for formation of ion conducting network are studied. | (i) Nafion performance is studied in the range of 18 wt% to 20 wt% HCl.
(ii) Nafion performance is important for reactor optimization. | (i) This review study only considers Nafion membranes performance and no reference is made to process economics. |
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| Barmashenko and Jörissen [3] (2005). | (i) An AEM process is developed for recovery of hydrogen and chlorine from dilute HCl to overcome the limitations of CEM process.
(ii) The results are shown with alternative designs to overcome its limitations (EOD). | (i) Parameters like selectivity of membrane and current efficiencies with respect to CaCl2 concentration and cell voltage are discussed.
(ii) Voltage drop versus current density and water transfer through membrane is also considered.
(iii) A possible design for an AEM with empty (gas filled) anode chamber is presented. | (i) This paper reviewed almost all electrolysis processes developed till 2005.
(ii) They were able to perform AEM process with cathode concentration as low as 3.2 wt%. | (i) The energy requirement is 1740 kWh at 4 kAm−2 and cell voltage of 2.3 V.
(ii) Effects of membrane surface area, electrode surface area, and temperature of the system are not considered. Process economics is not studied in detail. |
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| Mazloomi et al. [19] (2012). | (i) This paper tries to study parameters which affect electrical efficiency of KOH electrolysis to optimize electricity expense which is a majority in electrolysis. | (i) Total electrical efficiency is divided into three separate factors: electrical resistance, electrolysis, and thermal efficiency.
(ii) Temperature, pressure, and resistance of electrolyte, alignment of electrodes, electrode material, and applied voltage waveform are studied. | (i) This paper does not exactly deal with AEM electrolysis, but the nature of the parameters might remain the same to some extent in all electrolysis processes. | (i) Almost all of the parameters studied are only on KOH electrolysis.
(ii) This study only focused on electrical efficacy. |
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| Koter and Warszawski [20] (2000). | (i) Electrodialysis, electro-electrodialysis, and membrane electrolysis are discussed along with their applications to reduce environmental impact. | (i) A great deal regarding ion exchange membranes is discussed like application of membranes in fuel cells. Membranes (Nafion) properties are also discussed. | (i) Concludes that ion exchange processes are more sustainable and cleaner technologies in comparison to other recovery processes. | (i) This paper is more of a review study for membrane electrolysis.
(ii) Economic aspects are not discussed in detail. |
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| Ando et al. [7] (2010). | (i) This R&D report of Sumitomo Chemical Co., Ltd. mainly deals with newly developed rutile-type catalyst for oxidation of dilute HCl and also considers energy economics. | (i) Performance of rutile catalyst is determined in comparison to other catalysts based on conversion, corrosion resistance, and stability.
(ii) Complete overview of the process is presented. | (i) Rutile-type catalysts consume very less energy compared to UHDE ODC process.
(ii) The paper also reviews all recovery processes in the literature. | (i) Although it says that rutile based catalytic oxidation is better than electrolysis, it does not recover hydrogen.
(ii) Direct comparison of capital and operating costs with UHDE is not reported. |
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