Desalination of Neutral Amino Acid Solutions in an Electromembrane System

Abstract

This article’s main focus is to highlight significant aspects of amino acid solution demineralization. The main part of the amino acid production method requires the provision of downstream treatment solutions for the process of desalination. Electrodialysis (ED) and electrodeionization (EDI) are prospective technologies for such treatment. The article presents a brief review of the first studies and current research on electromembrane desalination of amino acid solutions as well as the analysis of some electrochemical features for the mineral salt–amino acid system (model solution) in an ED process based on the experimental results. The influence of various factors on the desalination of neutral amino acid-containing solutions and on target product losses in this process is estimated. The behavior of aliphatic (alanine) and aromatic (phenylalanine) amino acids in the electromembrane system is considered in mixed solutions with inorganic electrolytes. The influence of various mineral cations (Na+, K+ and NH4+) and anions (NO3−, SO42−, Cl−) on the features of the transport and current−voltage characteristics of ion-exchange membranes in the electrodialysis of phenylalanine- and alanine-containing solutions is considered. A comparative analysis of the desalination parameters of AA solutions in electrodialysis with the following pairs of heterogeneous MA-41/MK-40, MA-40/MK-40 and homogeneous AMT/CMT membranes is carried out. The minimum amount of amino acid loss along with rather high values of the degree of desalination are revealed in electrodialysis with polypropylene spacers in comparison with EDI, ED with a copolymer of styrene and divinylbenzene as spacer, as well as ED with a smooth deionization channel. At the same time, EDI is the most promising method to reach the highest desalination degree in the considered range of mineral salt content.

Current-Voltage and Transport Characteristics of Heterogeneous Ion-Exchange Membranes in Electrodialysis of Solutions Containing a Heterocyclic Amino Acid and a Strong Electrolyte

“…There was an increase in the geometric inhomogeneity of the membrane surface, as well as the blocking of its pores. This occurred as a result of the ion-exchange, as well as the non-exchange sorption of a heterocyclic amino acid due to weak ion-dipole and dipole-dipole interactions; and in the case of tryptophan, additionally, hydrophobic interactions of aromatic fragments of the amino acid structure and membrane [ 4 , 53 ]. An increase in the surface roughness of membranes that had been in contact with solutions of heterocyclic amino acids may also have been the cause of the increase in the contribution of electroconvection to the mass transfer of components through the membrane.…”

“…Amino acids are often required as high-purity compounds in medical, pharmaceutical, and cosmetic industry settings; however, when they are produced by the conventional methods, such as microbiological, chemical, or enzymatic synthesis, the target product is contaminated with impurities, in particular mineral salts. The modern electromembrane method–electrodialysis solves the problem of separating amino acids from mineral salts [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ].…”

“…However, studies of the transport and current-voltage, structural, and other characteristics of ion-exchange membranes in the electrodialysis of solutions containing a heterocyclic amino acid are represented by only a few works [ 13 , 14 , 15 ].…”

Electrodialysis Tartrate Stabilization of Wine Materials: Fouling and a New Approach to the Cleaning of Aliphatic Anion-Exchange Membranes

“…Standard procedure for determining the limiting current density (i lim exp ) is shown at Figure 11b. The CVC of a pristine membrane in model solution 1 (Figure 11a), which contains only a mixture of KCl and KHT, has the traditional shape described in much research [62,[67][68][69]. The curve contains the initial section I, the section of the inclined plateau II and the "overlimiting" section III.…”

Stability of Ion Exchange Membranes in Electrodialysis

“…Fouling intensity depends on the compatibility of the chemical nature of membranes and contaminants: for example, since large molecules in the food industry are usually negatively charged, in treatment of solutions of food industry anion exchange membranes are more susceptible to fouling than cation exchange ones (as, for example, shown for the processing of food industry solutions containing polyphenols [ 43 ] and liquid digestate [ 44 ]); since large organic molecules in the food industry are mainly hydrophobic, hydrophobic membranes are more prone to fouling than hydrophilic ones [ 45 ]; if the cause of fouling is a compound with benzene rings, such as aromatic amino acid, phenol, anthocyanin or tannin, then polystyrene-divinylbenzene membranes are more susceptible to fouling due to the occurrence of π-stacking interactions between foulants and membranes [ 46 , 47 ] than the aliphatic membranes. In addition, even the result of colloidal fouling of paired cation exchange and anion exchange membranes in the same chamber of the electrodialyzer depends on the nature of the membrane: at the end of period of useful operation in the food industry both cation exchange and anion exchange membranes were degraded and both of them lost part of their exchange capacity, but cation exchange membranes became denser and their thickness decreased while the thickness of anion exchange membranes doubled [ 48 ].…”