Determination of limiting current density for different electrodialysis modules

Abstract

Limiting current density of ammonium nitrate solution in laboratory-, pilot-, and industrial-scale electrodialysis modules were determined to provide a method for the prediction of the limiting current density of ammonium nitrate solutions at any conditions. The current-voltage curve was measured in each case and the limiting current density was evaluated using the dependence of the derivative, dI/dU, on the electric current, I. The limiting current was determined as a current at which the derivative dI/dU equals zero. The developed method enables not only the prediction of the limiting current density but the limiting cut and limiting flux can be determined concurrently at any linear flow velocity of the diluate and inlet ammonium nitrate concentration. It could help to prevent working in the overlimiting region and to avoid undesirable decrease of current efficiency and pH changes. The limiting cut is the maximal cut that can be obtained at certain linear flow velocity and module geometry irrespective of the inlet ammonium nitrate concentration and it is very useful information when designing a new electrodialysis unit for specific application.

Evaluation of Electrodialysis Desalination Performance of Novel Bioinspired and Conventional Ion Exchange Membranes with Sodium Chloride Feed Solutions

“…Electrical current density is the amount of electrical current (or charge flux: Coulombs per second per square meter) passing through the membrane’s active area inside the electrodialysis stack. For a given stack voltage, current density increases with the increase of concentrations in feed solution and the increase of solution velocity in the process streams, whereas current density declines with the decrease of solution temperature in the process streams as the effective cell resistance increases [ 38 , 39 ]. Theoretically, in an ideal electrodialysis system, the ion separation rate is proportional to the electrical current density through the electrodialysis stack.…”

Influência Da Concentração E Do Ph Na Densidade De Corrente Limite De Um Sistema De Membranas De Troca Iônica Por Eletrodiálise Para Separação De Cobalto (Ii)

“…Figura 1 -CVC ou curva de polarização típica de uma membrana [17,23,24] A região I, comumente chamada de região ôhmica, é caracterizada por um aumento linear do potencial conforme aumenta-se a corrente. A região II apresenta a zona de platô e marca a ocorrência do fenômeno da polarização por concentração.…”

“…Observou-se pelas das curvas corrente-potencial do ensaios A, B e C apresentadas na Figura 3, que a densidade de corrente limite aumenta com o aumento da concentração de íons, em conformidade com os resultados obtidos por Krol [16], Káňavová [24], Herraiz-Cardona [27] e Barros [22]. Este comportamento é explicado pela maior quantidade de íons que carregam a corrente elétrica.…”

Overcoming transport limitations in miniaturized electrophoretic delivery devices

“…28 The electric field at the inlet increases sharply as a result of ion depletion and causes electric field-enhanced water splitting, which then generates protons and hydroxide ions along the inlet interface. [29][30][31][32] In Fig. 1D an archetypical ionic current-voltage (I-V) curve is given for a CEM channel with the three distinct regions in the I-V regions clearly displayed.…”