%0 Journal Article
%T Selection of the Best Process Stream to Remove Ca2+ Ion Using Electrodialysis from Sugar Solution
%A Jogi Ganesh Dattatreya Tadimeti
%A Shilpi Jain
%A Sujay Chattopadhyay
%A Prashant Kumar Bhattacharya
%J International Journal of Electrochemistry
%D 2014
%I Hindawi Publishing Corporation
%R 10.1155/2014/304296
%X Electrodialytic removal of calcium chloride (CaCl2, 25¨C50£¿mol¡¤m£¿3) from 5% sugar solution was executed in batch recirculation mode. Calcium ion removal rate was monitored with (i) applied potential, (ii) feed flow rate, (iii) solution viscosity and conductivity, and (iv) catholyte streams (NaOH or sodium salt of ethylene diamine tetraacetic acid-acetic acid, Na2EDTA-AA). Unsteady state model for ion concentration change was written for the ED cell used. Linearized Nernst-Planck equation instead of Ohm¡¯s law was applied to closely obtain the current density and concentration change theoretically. The model developed could closely predict the experimental observation. Mass transfer coefficients and specific energy densities were estimated for each combination of catholyte stream used. NaOH showed better performance for a short duration over Na2EDTA-acetic acid combination. 1. Introduction In cane based sugar industry the sugar concentration in the extracted juice after lime (CaO + H2O) treatment and color removal (clarification step) usually reaches around 5% (mass basis). This stream subsequently enters into series of evaporators to get concentrated. Presence of excess calcium in the postfloculation and precipitation stage of clarified sugar juice creates series of nuisance [1] to the subsequent stages (evaporators, etc.) in sugar industries affecting product quality as follows.(1)Scale formation in the evaporators.(2)Improper crystallization.(3)Molasses percentage may increase due to inversion of sugar in alkaline medium.(4)Storage is hampered because of hygroscopic nature of these metals ions.(5)Excess calcium is not hygienic as well. Therefore, removal of it at appropriate stage would drastically reduce operation and maintenance (evaporator scaling) cost and improve product quality. Electrodialysis (ED) was chosen to remove CaCl2 from its sugar solution. ED was applied earlier in sugar industry to recover tartrate and malate from grape sugar [2] and in demineralisation of beet sugar syrup, juice, and molasses [3, 4]. The technological difficulties arise due to fouling of ion exchange membranes mainly due to deposition of organic/inorganic molecules (sugars, proteins, Ca2+, Mg2+, etc.). With increase in solution viscosity fouling becomes even severe and affects the current efficiency and ion removal rate. The concentration polarization occurs around membrane surface leading to increase in ion resistance, and this is minimized with the help of suitable spacer design, temperature, pH, and flow rates applied [5¨C11]. A batch recirculation ED process having
%U http://www.hindawi.com/journals/ijelc/2014/304296/