Study of pH correction process of chloride-bicarbonate dilute solutions by electrodialysis with bipolar membranes

Abstract

The pH of a dilute chloride-hydrocarbonate solution and the concentrations of chloride ions and carbonic acid anions at the outlet of the alkaline and acid chambers of the electrodialysis cell formed by bipo lar and anion exchange membranes were determined. The decrease in the concentration of hydrocarbonate ions in the alkaline chamber with growth of current density was not equal to its increase in the acid chamber. This disbalance was caused by two concurrent processes: the electromigration ion transport through the anion exchange membrane and the chemical reactions of hydrocarbonate ions with the water dissociation products formed on the bipolar and anion exchange membranes. A mathematical model was suggested to describe the electrodialysis correction of the pH of a dilute chloride-hydrocarbonate solution. The experi mental data on the correction of pH of the chloride-hydrocarbonate solution were well approximated by both the model that takes into account water dissociation on the anion exchange membrane and the simpli fied model that neglects water dissociation. The experimental data agreed well with the results of calculations by the model in which the effective anion transport numbers were calculated only from ion concentrations and diffusion coefficients in solution. This reflects the outer diffusion character of the kinetics of ion transport through the anion exchange membrane, with pH of dilute solutions corrected by electrodialysis.

Reagent-Free Electromembrane Process for Decarbonization of Natural Water

“…We write the flow balance equations for all components (j = 1, … 9) in the acid and alkaline compartments. , ( 5,8).…”

“…In electro-membrane processes for adjusting pH of dilute solutions, electrodialyzers with a two-compartment unit cell consisting of monopolar and bipolar membranes are used. The process of pH correction of model binary electrolytes and multi-ion chloride-sulfate-bicarbonate solutions in an electrodialysis cell with bipolar and anion-exchange membranes was theoretically and experimentally studied [5]. The authors showed that from a practical point of view, an electrodialyzer circuit with bipolar and anion-exchange membranes can be effectively used to alkalize technological solutions, while a cation-exchange membrane scheme is preferred for acidification of solutions.…”

Analysis of bipolar membranes for electrochemical CO2capture from air and oceanwater

“…39,40 There is also little precedent for modeling the transport of dilute carbon species in seawater feedstocks used for DOC. 7,41 Models that relate the chemistry and material properties of BPMs to the energy intensity of BPM-ED are therefore warranted. 42 In this work, we demonstrate a comprehensive model of BPM-ED based on our prior work modeling multi-component transport in BPMs, 27 now with the homogeneous reaction kinetics of reactive carbon species (eqn (2)-( 5)).…”

Exploring Bipolar Membranes for Electrochemical Carbon Capture

“…39,40 There is also little precedent for modeling the transport of dilute carbon species in seawater feedstocks used for DOC. 7,41 Models that relate the chemistry and material properties of BPMs to the energy intensity of BPM-ED are therefore warranted. 42 In this work, we demonstrate a comprehensive model of BPM-ED based on our prior work modeling multi-component transport in BPMs, 27 now with the homogeneous reaction kinetics of reactive carbon species (Eq.…”