Appl. Sci. 2020 , x 5148 doi:10.3390 app10155148 www.mdpi.com journal applsci [616734]

Appl. Sci. 2020 , x; 5148 doi:10.3390 /app10155148 www.mdpi.com /journal /applsci
Article 1
Modelling the Processes of PH Correction of Salt 2
Solutions and H -Cationwater Rinsing Concentration 3
by Electrodialysis 4
Tina Kharebava1, Oleksandr Petrov2*, Irina Bejanidze3, Volodymyr Pohrebennyk4, Nato 5
Didmanidze5, Nunu Nakashidze6, Nazi Davitadze7, Anton Petrov8 6
1 Department of Chemistry, Batumi Shota Rustaveli State University, Batumi, 6010, Georgia; 7
tina.kharebava@ bsu.edu.ge 8
2 Department of Applied Computer Science, AGH University of Science and Technology, Kraków 30 -059, 9
Poland; [anonimizat] 10
3 Department of Chemistry, Batumi Shota Rustaveli State University, Batumi, 6010, Georgia; irina.bejanidze@ 11
bsu.edu.ge 12
4 Department of Ecological Safety and Nature Protection Activity, Lviv Polytechnic National University, Lviv 13
79013, Ukraine; volodymyr.d.pohr [anonimizat] 14
5 Department of Chemistry, Batumi Shota Rustaveli State University, Batumi, 6010, Georgia; 15
nato.didmanidze @bsu.edu.ge 16
6Department of Agroecology and Forestry, Batumi Shota Rustaveli State University, Batumi, 6010, Georgia; 17
nunu.nakashidze@ bsu.edu.ge 18
7 LTD Batumi Water, Batumi, 6010, Georgia; [anonimizat] 19
8 Department of Information Systems, Kuban State Agrarian University named after I.T. Trubilin , 3500 44, 20
Krasnodar, Russia ; petrov.a@ kubsau.ru 21
* Correspondence: [anonimizat] ; Tel. + 48-886-818-122 22
Received: 2020; Accepted: 2020; Published: date : 23
Abstract : The process of reagentless adjustment of the acidity of NaCl solution with different initial 24
pH values as well as the possibility of concentrating residual acid from the washing water of 25
H-cationization of KU -2-8 cation exchanger with the aim of returning HCI to the process cycle were 26
studied by electrodialysis method on a multi -chamber inslallatio. with two -layer bipolar MB -2 and 27
single -layer ion -exchange membranes MK -40, MA -40. In the r ange of initial values of 2.0 <pH <12.0 28
of the original solution, the patterns of changes in the acidity of solutions as a function of electric 29
current density, productivity, and energy consumption per process were investigated. It is shown 30
that the larger is the deviation of the pH of the initial solution from the neutral value and the higher 31
is the productivity of the apparatus, the higher is the electric current density and energy 32
consumption for the neutralization process. The possibility of maximum con centration of the 33
residual HCL acid in the washing waters of H -cationization, was studied under various hydraulic 34
and electrical operating conditions of the apparatus. It is shown it is possible to concentrate HCl up 35
to 5% and return it to the process cycl e for the regeneration of cation exchanger. 36

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Keywords : electrodial ysis, H -cationization, membrane, modelling, salt solutions. 37
38
1. Introduction 39
The issue of natural ecosystems preserving is becoming more and more actual at the present 40
stage in terms of increasing human influence on the environment [1-5]. Currently the problem of 41
surface water quality is relevant and requires urgent solution [6-10]. There is an intensive growth of 42
rivers’ water using those results in deterioration of water quality and hydrological regime [ 11-15]. 43
The present situation is aggravated by anthropogenic pollution of surface and groundwater by 44
utilities and agrarian sector. 45
Electrodialysis is one of the methods of membrane technology for the separation and 46
purification of liquids. According to the forecasts of the development of the world economy, 47
membrane technology is regarded as the technology of the futur e [16-22]. It has been widely used in 48
many industries and agriculture. Membrane processes are used in almost all spheres of human 49
activity, since they ensure high efficiency of processes, namely: reduce the cost of materials, raw 50
materials and energy, increase the thermal and energy potential, provide the population with 51
drinking water, protect the environment, etc. [ 23-26]. Electrodialysis is an environmentally friendly 52
and low energy -consuming process [ 27-31]. The application of this method allows you to 53
successfully carry out the processes of desalination and concentration of solutions, obtaining 54
drinking water from salt water, treatment of natural and industrial wastewaters, etc. It is widely 55
introduced in the energy, electronic, chemical and food industries, in medicine, agriculture and 56
othe r spheres of human activities [32– 35]. The annual global sales of membranes an d membrane 57
equipment has increased significantly in recent years and amounted to over 11 billion US dollars by 58
the beginning of the 21st century [ 36-39 ] (Figure 1). 59
60
61
Figure 1. Electrodialysis plant 62
The basis of electrodialysis is the selective transport of ions of dissolved substance through 63
ion-exchange membranes under the influence of an electric field. The driving force of this process is 64
the gradient of the electric potential on both sides of the membrane. Under the influence of an 65

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electric field, positively charged ions (cations) move towards the negative electrode (cathode), 66
through cation -selective memdranes, while negative ions (anions) move towards a positively 67
charged electrode (anode) thro ugh anion- selective membranes [40- 42] (Fig ures 2,3). 68
69
70
Figure 2. Scheme of electrodialysis process 71
72
Figure 3. Mechanism of the electrodialysis process 73
The scope of electrodialysis method expanded with the use of bipolar membranes. A bipolar 74
membrane is a two -layer composite membrane consisting of layers of cation – and anion -exchange 75
membranes that are direct ly in contact with each other [ 43-48 ]. 76
One layer of the membrane is exchanged for solution cations (the cation -exchange side of the 77
membrane), and the other – for anions (the anion- exchange side of the membrane). When the bipolar 78
membrane is located with the cation -exchange side to the cathode and the anion- exchange one to the 79
anode, the membrane generates H+ and OH- ions due to the splitting of water molecules, even with a 80
small electric field voltage at the interface between the layers [ 49-51]. This ability of the bipolar 81
membrane has been successfully used to produce acids and bases from salt solutions. The first use of 82
bipolar membranes for this purpose was proposed in the patent. Currently, electrodialysis with 83
bipolar membranes is used not only for the production of acids and bases [ 52-55], but also for th e 84
reagentless pH adjustment of various liquids [ 56,57 ] (Figures 4-7). 85
86

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87
Figure 4, 5. Schematic concentration profiles in a bipolar membrane [ 46] 88
89
Figure 6, 7. Mechanism of the electrodialysis process with bipolar membranes 90
Many scientists and engineers have attempted to develop fluid treatment systems in industrial 91
and agricultural processes to control pH (preparation of washing water, treatment of industrial 92
effluents, processes for producing caustic soda and chlorine, treatment of milk whey, preparation of 93
water for use in agriculture and water supply systems) [58-60]. 94
Enterprises, consumers of large amounts of water, have certain requirements for water. For 95
example, the efficiency of the coagulation process in water treatment systems is largely dependent 96
on the pH of water under treatment, since only at the optimum pH = 10.0 –10.5, the minimum 97
solubility and maximum mechanical strength of the resulting hydroxides is achieved. Also, washing 98
wastewater, obtained after ac id-base regeneration of ion -exchangers and those used in thermal and 99
nuclear energy, before being discharged into the sewer, requires adjusting the acidity to a neutral 100
media [61-64]. 101
When adjusting the pH of liquids with che mical reagents , in particular , when preparing water 102
for clarification, acidity is controlled by dosing alkaline or acid solutions. In control systems for 103
growing plants under cover , an automatic measuring device of alkali and acid solutions with a 104
concentra tion of 20 –30% is also propo sed. Despite the variety of methods for dosing chemical 105
reagents, their use, as a rule, leads to great inconvenience in work for the following reasons: 106
 the formation of a large amount of sediments as a result of changes in acidity; 107
 disruption of dosing mechanism operation due to clogging of holes; 108

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 the need to prepare reagent solutions of a certain concentration; 109
 inaccuracy in predicting and obtaining acidity values. 110
In addition, increasing the scale of production consumption requires additional reagent costs 111
and, accordingly, increases the cost of water treatment. And water s with pH~7 , in case of their 112
increased salinity of large water volumes, pose an environmental threat . It is known that heat and 113
nuclear power plants annually discharge 780 -800 thousand tons of salt . 114
An alternative to reagent pH control systems are electrodialysis systems . In particular, in , an 115
electrodialysis process for adjusting the pH of dilute solutions was carried out on a two -chamber 116
electrodialysis cell and it was sho wn that the efficiency of the process is determined by two key 117
factors: the voltage on the bipolar membrane and the associated generation rate of H+ and OH– ions, 118
and, the second factor is due to the influence of the dissociation of water molecules on monopolar 119
membranes which form, together with the bipolar membranes, a packet of electrodialysis apparatus. 120
The efficiency of the electrodialysis process of pH adjustment is determined, first of all, by the 121
voltage and the numbers of H+ and OH– ions transport on the bipolar membrane [ 65, 66]. 122
On an industrial scale, the electrodialysis process is carried out in multi -chamber installations in 123
a continuous flow. Depending on the goal, membranes of appropriate selectivity are chosen, the 124
working chambers in the apparatus are connected in series or in parallel, i.e. for each specific case, 125
the type of apparatus and membranes, the hydraulic circuit and the electrical process parameters are 126
selected [67]. 127
Thus, the issue of adjusting the pH of saline solutions and industrial effluents, without the use 128
of chemical reagents, is very relevant, since it will simplify the technological schemes in use, reduce 129
the volume of effluents and the cost of chemical reagents, also concentrating and returning v aluable 130
products to the technological cycle will make the process more economical and, accordingly, reduce 131
the risk of environmental pollution [68]. 132
The purpose of the work is to study the process of reagentless pH adjustment of salt solutions of 133
various acidity and the possibility of concentrating and returning to the process cycle of residual 134
acid from the H-cationization washing water. 135
2. M ethods and materials 136
Investigation on the change in pH of salt solutions of different acidity was carried out on an 137
experimental electrodialysis apparatus, consisting of two platinized titanium electrodes and a 138
membrane package located between them which, when adjusting the pH of alkaline salt solutions, 139
consisted of alternately arranged cation -exchange MK -40 and bip olar MB -2 membranes, and in the 140
case of acidic solutions – anion -exchange MA -40 and bipolar MB -2 membranes. The membranes are 141
mass -manufactured at JSC Shchekinoazot (Russia). The MK -40 cation -exchange membrane was made 142
of the KU -2 (2/3) strongly acidic cat ion exchanger composition containing sulfo groups and 143
polyethylene, the MA -40 anion -exchange membrane was made of the EDE- 10 P anion exchanger 144
composition containing quaternary ammonium bases (20%), secondary amines and polyethylene. 145
The bipolar membrane o f the MB -2 brand is made on the basis of KU -2 gel -type sulfocationionite 146
and AB -1 gel -type benzyltrimethylammonium anionite containing the groups: – SO 3H, +N(CH 3)2. 147
The working solutions with different pH values were prepared by adding sodium chloride (0.5 148
g/l), sodium hydroxide or hydrochloric acid solutions to the solution. The pH of the initial solutions 149
varied in the range of pH = 2.0 -12.0. The membrane package of the electrodialysis apparatus 150

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consisted of 50 pairs of working chambers. The thickness of each chamber is 1.2 mm, and the 151
effective working area of one membrane is 0.124 m2. The membrane package was hydraulically 152
assembled in parallel, which provides the same process conditions in all chambers. The initial 153
solution was not supplied to the concentration chambers. The movement of fluid in these chambers 154
was carried out due to the electroosmotic transfer of the solvent from the dialysate chamber. 155
The study on the possibility of maximum concentration of the residual acid of the washing 156
water of H -cationization in order to return HCl to the processing cycle was carried out on a filter 157
press -type electrodialysis apparatus. The membrane package located between the two 158
platinum -plated titanium electrodes was assembled with sequentially arranged monopolar 159
membranes MK -40 and MA -40. Therefore, consecutive desalting (dialysate) and acid concentration 160
sections were created in the apparatus. The number of similar membran es and the working area, 161
respectively, amounted to 200 pieces and 32.8 m2 (Figure 8). 162
163
164
165
Figure 8. Installation of bipolar electrodialysis [39] 166
Washing water, containing after H -cationization a residual concentration of HCl up to 1%, was 167
used as a working solution. The electrodialysis process of acid concentrating, based on the operating 168
capacity of the apparatus (660 l/h), was studied under the following hydrau lic modes: mode 1 – the 169
flow rate of the initial solution in the dialysate and concentration sections was the same – 330 l/h; 170
mode 2 – the flow rate of the initial solution in dialysate sections was 660 l/h, in brine sections – 400 171
l/h; mode 3 – the flow r ate of the initial solution in dialysate sections was 660 l/h, in brine sections – 50 172
l/h; mode 4 – the flow rate of the initial solution in the dialysate sections is 660 l/h, and in the brine 173
sections – the solution was not supplied. For each hydraulic mode, by changing the value of the 174
applied voltage to the apparatus, the optimal electrical parameters of the process were set and the 175
following process indicators were calculated on their basis: desalination depth, degree of 176
concentration, current efficiency, operating capacity and energy consumption per process. 177

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3. Results and discussion 178
Reagentless acidity adjustment of saline solutions with initial pH = 2.0 -12.0 was studied 179
depending on the applied voltage to the apparatus. When alkaline salt solutions w ere passed 180
through an electrodialysis apparatus, the pH of the solutions in the dialysate chambers decreased in 181
accordance with the increase in voltage, almost to a neutral value. The alkaline working solutions 182
were neutralized with hydrochloric acid which was formed in the dialysate tract due to chlorine ions 183
and hydrogen ions migrated from the cationic layer of the bipolar membrane. 184
The process of adjusting the pH of solutions was studied at differen t operating capacities ( Q = 185
0.5-1.5 m3/h) of the apparatus. The results obtained during the experiment are shown in Figures 9 -12. 186
187
Figure 9. Electrodialysis of weakly alkaline solutions (pH = 7.5, Q = 1 m3/h) 188
The analysis of the study results showed that the neutralization of weakly alkaline solutions 189
(pH=7.5- 8.5) can be achieved under conditions of low voltage values ( U≈50V ). Further voltage 190
increase leads to a shift of pH in the solutions (dialysate) from a neutral (pH~7) to acidic 191
environment. An increase in the alkalinity of the working solutions in the pH range of 8.5 –11.0 192
requires a significant increase in the voltage to neutralize these solutions: the greater the deviation of 193
the pH value of the initial solution from neutral, the higher the voltage should be. 194
195
Figure 10. Elect rodialysis of weakly alkaline solutions (pH = 8.5, Q = 1 m3/h) 196
Figures 13 -16 and Figures 17 -20 show the results of pH adjusting of solutions with an initial 197
value of pH = 9.3 and pH = 10.6, respectively, with different operating capacity of the apparatus. It 198
was found that in conditions of constant productivity, an increase in voltage increases t he intensity 199
of pH decreasing, and an increase in productivity increases the value of voltage required to 200
neutralize the solution. Besides, the intensity of lowering the pH of the solution is greater, the higher 201
the current density, and it is the less, the greater the productivity of the apparatus. It was 202
02468101214
0 50 100 150U,vI,A/m²
pH (d)
051015
0 50 100 150U, vI,A/m²
pH (d)
pH (c)

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established: the higher the productivity of the apparatus and the alkalinity of the solution, the higher 203
the current density, voltage and energy consumption should be. 204
205
Figure 11. PH adjustment of weakly alkaline solutions (Q = 1 m3/h) 206
207
Figure 12. Comparison of pH adjustment data for acidic and alkaline solutions (Q =1 m3/h) 208
209
210
211
Figure 13. pH adjustment of alkaline solutions (pH = 9.3) at an operating capacity of Q = 0.5 m3/h 212 02468101214
0 50 100 150pH
U,vpH(d), pH=7.5 pH(d),pH=8.5
pH(c), pH=7.5 pH(c), pH=8.5
02468101214
0 50 100 150 250 270 300pH
U, VpH(d), pH=7.5
pH(d),pH=8.5
pH(c), pH=7.5
pH(c), pH=8.5
pH(d),pH=3.3
pH(c), pH=3.3
02468101214
pH(d) pH(c) W, kW· h/m³0v 100v

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213
214
Figure 14. pH adjustment of alkaline solutions (pH = 9.3) at an operating capacity of Q = 1 m3/h 215
216
Figure 15. pH adjustment of alkaline solutions (pH = 9.3) at an operating capacity of Q = 1 m3/h 217
218
Figure 16. Change in adjustment parameters (pH = 9.3) at Q = 1.5 m3/h with increasing voltage 219
During electrodialysis of the initial solution with pH> 1, a decrease in the pH of the product 220
(dialysate) was practically not achieved. This is probably due to the excess of hydroxyl ions in the 221
initial solution itself, as well as to the operation of the apparatus in the over -extreme mode, which 222
impedes the generat ion of OH- ions by the bipolar membrane. 223 02468101214
0 100 150U,VpH(d)
02468101214
0 100 150 160 200U,VpH(d) pH(c)
W, kW· h/m³02468101214
pH(d) pH(c) W, kW· h/m³0в 100v 150v

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During the experiment on alkaline salt solutions, in the concentration sections of the apparatus, 224
in contrast to dialysate chambers, the formation of a 5 -6% sodium hydroxide solution, with a volume 225
of no more than 2 % of the product volume, took place. 226
227
Figure 17. Dependence of the process parameters on the current density (Q = 0.5 m3/h, pH = 10.6) 228
In addition to alkaline solutions, the possibility of adjusting the pH of acidic saline solutions 229
was studied. To solve this problem, the electrodialysis apparatus was equipped with bipolar – and 230
anion -exchange membranes. 231
Correction of the content of sodium chloride solutions with pH = 2.7 and pH = 3.3 was carried 232
out. The initial solution was supplied only to the dialysate chambers of the apparatus. 233
234
Figure 18. Dependence of the process parameters on the current density (Q = 0.7 m3/h, pH = 10.6) 235
236
Figure 19. Dependence of the process parameters on the current density (Q = 1 m3/h, pH = 10.6) 237 02468101214
3,4 6,5 9,7i,A/m2pH(prod.)
pH(conc)
W, kW· hour/m3
02468101214
6,7 13,8 21,3 i, A/m2pH(d) pH(c) W, kW· h/m³
02468101214
8,2 16,9 25,2 28,8i,A/m2pH(d) pH(c) W,kW· h/m³

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238
Figure 20. Dependence of the process parameters on the current density (Q = 1.5 m3/h, pH = 10.6) 239
In these chambers, when voltage is applied, sodium hydroxide is formed due to Na+ cations of the saline 240
solution and OH- anions generated by the bipolar membrane. As a result of the experiment, it was found that 241
when treating a solution with pH = 2.7, even at a high current density (i > 20 A/m2), the device does not 242
significantly change the pH of the product, which is probably due to the presence of excess hydrogen ions in 243
the initial solution and high current densities that impede the process of generating H+ ions by a bipolar 244
membrane he results obtained during the electrodialysis treatment of the acidic saline solution with a pH> 3.3 245
are presented in Fig. 21 and Fig. 22 . 246
247
Figure 21. PH adjustment of acidic solutions (pH = 3.3) 248
As follows from the data obtained, the intensity of change in the acidity of the solution depends 249
on the current density and apparatus operating capacity: with an increase in the value of these 250
indicators, the pH of the product increases and, consequently, the energy consumption o f the 251
process increases. Fig. 22 presents data on compar ing pH adjustments of acidic and alkaline 252
solutions. 253
254 02468101214
8,7 19,35 29,09 28,79 i, A/m2pH(d) pH(c)
024681012
0 150 180 200 250 270 300pH
U,vpH(d), Q=0.5 m³/h
pH(c), Q=0.5 m³/h
00,20,40,60,811,2
10,5 10,6 13,3 16,1 17,1 20,3 22,6W, kW h /m³
i, A/m2W, k Wh/m³, Q=0.5 m³/h W, кW· h/m³, Q=1,0 m³/h

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Figure 22. Dependence of the energy consumption of the process of adjusting acidic solutions on the 255
current density 256
During the experiment, in the concentration chambers of the apparatus, the formation of a 257
1.8-3% hydrochloric acid solution took place, the total volume of which did not exceed 2% of the 258
product volume. 259
Further, on an industrial electrodialysis apparatus, the membrane package of which was 260
assembled only from monopolar membranes M K-40 and MA -40, the possibility of maximum 261
concentrating residual acid HCl in the washing water after H -cationization (regeneration) of KU -2-8 262
cation exchanger was experimentally studied. This cation exchanger is used in many water 263
treatment systems to sof ten water. The regeneration of cation exchangers is carried out with 264
solutions of hydrochloric (5 -7%) or sulfuric (1 -1.5%) acids. When using hydrochloric acid, its 265
residual concentration in the washing water is approximately 1%. 266
The electrodialysis process of acid concentrating was studied depending on the applied voltage 267
at different hydraulic mo des of the apparatus operation. The data ob tained are presented in Figs. 268
23-27. 269
270
Figure 23. Curves of changes in HCl concentration in brine C (c) and dialysate C (d) sections 271
depending on the applied voltage 272
273
Figure 24. Curves of the process parameters changes depending on the voltage value 274
As can be seen from Fig. 23 and Fig. 24 (mode 1), when the source water is supplied to the 275
dialysate and concentration sections with a ratio of 1:1, even at a voltage of 50 V, the acid 276
concentration in the concentration section increases from 9 to 16 g/ L. 277 048121620
0 50 100 160 180 220C, g/l
U, VC(d), g/l C(c),g/l
050100150200
50 100 160 180 220U,vβ(d)
η,% ( d)
β(c)
η,%( c)
W(d),kW· h/m³
W(c),kW · h/m³

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Howe ver, as can be seen from Fig. 23 , under the conditions of this mode, a further increase in 278
voltage practically does not cause a change in the concentration of acid in the concentration 279
sections. Whereas the concentration of acid in the dialysate section decreases sharply with 280
increasing voltage, i.e. in this mode, the depth of desalination tends to infinity, while the degree of 281
acid concentration reaches its theoretical maximum value (β (c) = 2), which is confirmed by the data 282
presented in Fig. 24 . 283
The process proceeds similarly in the case of hydrau lic flows of solutions in sections of the 284
apparatus with a ratio of 3:2 (mode 2). When a voltage of 160 V was applied to the installation, the 285
concentration of hydrochloric acid in the concentration sections increased to 20 g/ L and the 286
subsequent increase in voltage only increased the desalination depth, which is clearly shown by the 287
curves in Fig. 25 . 288
289
Figure 25. The dependence of the process parameters on voltage (mode 2) 290
In the case of hydraulic flows with a ratio of 13:1 (mode 3), after applying a voltage of 200 V to 291
the installation, the concentration of hydrochloric acid in the concentration section was 50 g/l. At 292
the same time, in this mode, there was a decrease in the depth of desalination compared to the 293
above modes, but it still rem ained quite high. The concentration of hydrochloric acid, at the above 294
voltage value, in the dialysate section was 0.6 g/ l. Fig. 26 shows the dependence of process 295
parameters on voltage value (mode 3). 296
During the hydraulic mode, when the initial solution w as not supplied to the concen tration 297
section (mode 4, Fig. 27 ), applying a voltage of 150 -160 V to the apparatus made it possible to 298
achieve high levels of hydrochloric acid concentration. But under these conditions, an acceptable 299
desalination depth could not be achieved in the dialysate section, and an increase in voltage made 300
the process practically ineffective. This is easily explained by the presence of a high concentration 301
gradient between the concentration and dialysate sections. 302
Thus, the most effective method for concentrating hydrochloric acid of all the studied 303
hydraulic modes is mode 3 – with a ratio of solution flow in dialysate and concentration sections of 304
13:1. 305
Under the abovementioned operating conditions, when applying a voltage of 180 -200 V to the 306
installation, hydrochloric acid can be concentrated up to 5%, which is quite enough for the 307
regeneration of cation exchanger. At the same time, the residual concentration of hydrochloric acid 308
in the dialysate is 0.05%, which significantly red uces the consumption of alkali that is currently 309
used to neutralize industrial wastewater. 310 020406080100120
100 130 150 170 225 260 300U,vβ(d)
η,% ( d)
β(c)
η,%( c)

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311
Figure 26. The dependence of the process parameters on voltage value (mode3) 312
313
314
Figure 27. The dependence of the process parameters on voltage value (mode 4) 315
It is shown that when applying the sorption method for water softening in the water treatment 316
system, it is recommended to concentrate the residual acid present in the wastewater by the 317
electrodialysis method and return it to the process cycle, which makes the sorption method for 318
water softening more environmentally friendly and economical. 319
It was found that at high concentration gradients between the concentration and desalination 320
sections , the required level of desalination is not achieved in the dialysate chamber, and the voltage 321
increase is practically ineffective. 322
4. Conclusions 323
The possibility of reagentless pH adjustment of salt solutions by bipolar electrodialysis is 324
shown. It was found that at 3.0≤pH≤11.0, the change in the pH of the solution depends on its initial 325
value, electric current density and apparatus performance. 326
Results obtained : the higher the deviation of the pH of the initial solution from the neutral, the 327
higher should be the current density and energy consumption for the neutralization process. It is 328
found : with the acidity of the initial solution with 3.0> pH> 11.0, it is practically impossible to adjust 329
the pH of the solution by electrodialysis , which is due to the presence of the excess of hydrogen 330
(acidic solutions) or hydroxyl (alkaline solutions) ions in the initial solution and high current 331
densities which impede the process of generating H + and OH- ions by a bipolar membrane. 332 0102030405060
100 120 164 200 220 240 260 284 328U,vβ(d)
η,% ( d)
010203040506070
100 119 125 150 160 200 212U,vβ(d)
η,% ( d)

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When using the sorption me thod to soften water, it is recommended to concentrate the 333
residual acid present in the wash ing water after H -cation ization by the electrodialysis method . 334
It is shown that the most effective method for concentrating hydrochloric acid of all the 335
studied hydraulic modes is mod e 3 — with a ratio of solution flow in dialysate and concentration 336
sections of 13: 1. It has been established that under the a bovementioned op erating conditions, when 337
a voltage of 180 -200 V is applied to the installation, it is possible to concentrate hydrochloric acid up 338
to 5% and return it to the pro cess cycle for the regeneration of cation exchanger. It is shown that in 339
this mode, the residual concentration of hydrochloric acid in the dialysate is 0.05%, which 340
significantly reduces the consumption of alkali that is currently used to neutralize industrial 341
wastewater . 342
The data obtained in this work can be used to model the processes of pH correction of saline 343
solutions and to concentrate rinsing water of H -cationization by electrodialysis . 344
345
Author Contributions: Conceptualization, I.B. and T.K.; methodology, I.B. and T.K.; software, I.B.; validation, 346
I.B., T.K., and V.P.; formal analysis, N.D. and V.P; investigation, N.D., N.N and N.D.; resources, I.B.; data 347
curation, I.B., and N.D.; writing —orig inal draft preparation, I.B., T.K. and V.P ; writing —review and editing, 348
I.B., T.K., A.P. and O.P.; visualization, N.D.; supervision, V.P.; project administration, O.P. All authors have 349
read and agreed to the published version of the manuscript. 350
Funding: This research received no external funding. 351
Conflicts of Interest: The authors declare no conflict of interest 352
5. References 353
1 Kvaternyuk, S. ; Pohrebennyk, V.; Petruk, R.; Kochanek, A.; Kvaternyuk, O. Multispectral television 354
measurements of paramete rs of natural biological media, In Proceedings of the 17th International 355
Multidisciplinary Scientific GeoConference SGEM , Albena, Bulgaria, 29 June –5 July 2017 , pp. 689 –696. 356
2 Pohrebennyk, V.; Petryk, A. The degree of pollution with heavy metals of fallow soils in rural 357
administrative units of Psary and Płoki in Poland. In Proceedings of the 17th International 358
Multidisciplinary Scientific GeoConference, SGEM, Albena, Bulgaria, 29 June –5 July 2017; Volume 17, pp. 359
967–974. 360
3 Mitryasova, O. ; Pohrebennyk, V.; Kochanek, A ., Sopilnyak , І. Сorrelation interaction between electrical 361
conductivity and nitrate content in natural waters of small rivers . In Proceedings of the 16th International 362
Multidisciplinary Scientific Geoconference, SGEM , 2016, Vienna, AUSTRIA, 02-05 November 2016, pp. 363
357-364 364
4 Cherniuk , V. V., Ivaniv , V. V, Bihun , I. V. and Wojtowicz , Ja. M. C o e f fi c i e n t o f F l o w R a t e o f I n l e t 365
Cylindrical Nozzles with Lateral Orthogonal Inflow. Proceedings of CEE 2019 . Advances in 366
Resource -saving Tec hnologies and Materials in Civil and Environmental Engineering. Springer. Nature 367
Switzerland AG 2020. 2020, 50-57 (https://doi.org/10.1007/978 -3-030-27011 -7_7) 368
5 Bosak, N., Cherniuk, V., Matlai, I., Bihun, I. Studying the mutual interaction of hydraulic characteristics of 369
water distributing pipelines and their spr aying devices in the coolers at energy units. Eastern -European 370
Journal of Enterprise Technologies, 2019 , 3/8 (99), 23-29. (DOI: 10.15587/1729- 4061.2019.166309). 371
6 Mitryasova, O.; Pohrebennyk, V. Integrated environmental assessment of the surface waters pollution: 372
Regional aspect. In Proceedings of the International Multidisciplinary Scientific GeoConference SGEM, 373
Vienna, Austria, 27 –29 November 2017; 33, pp. 23 5–242. 374

16 of 20
7 Pohrebennyk, V. ; Karpinski, M.; Dzhu melia, E.; Klos-Witkowska, A.; Falat, P. Water bodies pollution of the 375
mining and chemical enterprise. In Proceedings of the 18th International Multidisciplinary Scientific 376
GeoConference, SGEM, Albena, Bulgaria, 30th June to 9th July 2018 , 18 (5.2), pp. 1035-1042. 377
8 Pohrebennyk, V.; Mitryasova, O.; Klos-Witkowska, A.; Dzhumelia, E. T he Role of M onitoring the Territory 378
of Industrial Mining and C hemical Complexes at the S tage of L iquidation . In Proceedings of the 379
International Multidisciplinary Scientific GeoConference SGEM, Vienna, Austria, 27 November – 29 380
November 2017, 33 (17), pp. 383–390. 381
9 Prokopenko, O.; Eremenko, Y.; Omelyanenko, V. Role of international factor in innovation ecosystem 382
formation, Economic Annals -XXI 2014, 3-4, pp. 4 -7. 383
10 Prokopenko, O.; Kysly, V.; Shevchenko, H. Peculiarities of the natural resources economic estimation under the 384
transformational condi tions . Economic Annals -XXI 2014 , 7-8, 40-43. 385
11 Pohrebennyk, V.; Dzhumelia, E.; Korostynska, O.; Mason, A.; Cygnar, M. X-Ray fluorescent method of 386
heavy metals detection in soils of mining and chemical enterprises. In Proceedings of the 9th International 387
Conference on Developments in eSystems Engineering, DeSE 2016, Liverpool, UK, 31 August –2 388
September 2017; pp. 323 –328. 389
12 Ishchenko , V.; Pohrebennyk, V. ; Kozak, Y. ; Kochanek, A. ; Politylo, R. , Assessme nt of batteries influence on 390
living organisms by bioindication method, 16th International Multidisciplinary Scientific GeoConference, 391
SGEM , Albena, Bulgaria, 30 June -6 July 2016 , 2, pp. 85 -92. 392
13 Petruk , R.; Pohrebennyk, V. ; Kvaternyuk, S. ; Bondarchuk, O. ; Cygnar, M. Multispectral television 393
monitoring of contamination of water objects by using macrophyte -based bioindication. In 16th 394
International Multidisciplinary Scientific GeoConference:, SGEM 2016, Albena, Bulgaria , 30 June -6 July 395
2016, 2, pp. 597-602. 396
14 Karpinski , M.; Pohrebennyk , V.; Bernatska , N.; Ganczarczyk , J.; Shevchenko , O. Simulation of artificial 397
neural networks for assessing the ecological state of surface water. In Proceedings of the 18th International 398
Multidisciplinary Scientific GeoConference , SGEM, Albena, Bulgaria, 30th June to 9th July 2018 , 18 (2.1), 399
pp. 693 -700. 400
15 Kvaterniuk, S.; Pohrebennyk, V.; Petruk, V.; Kvaterniuk, O.; Kochanek, A. Mathematical modeling of light 401
scattering in natural water environments with phytoplankton particles. In Proceedings of the 18th 402
International International Multidisciplinary Scientific GeoConference , SGEM, Albena, Bulgaria, 30th June 403
to 9th July 2018, 18 (2.1), pp. 545- 552. 404
16 Bejanidze , I.; Pohrebennyk , V.; Kharebava, T.; Koncelidze, Z.; Jun, S . Development of waste-free, eco -pure 405
combined technology for fruit processing. In Proceedings of the International Multidisciplinary Scientific 406
GeoConference SGEM. 30 June -6 July 2019, Albena, Bulgaria, 19 (5.1), pp. 173-180. 407
17 Bejanidze, I.; Pohrebennyk , V.; Kharebava, T.; Koncelidze, L.; Sun Jun. Correction of the chemical 408
composition of the washing waters received as a result of h cation exchange of ionex change resin. In 409
Proceedings of the International International Multidisciplinary Scien tific GeoConference SGEM. 30 June -6 410
July 2019, Albena, Bulgaria, 19(5.1), pp. 133-140. 411
18 Bejanidze, I.; Kardash, P.; Pohrebennyk, V.; Kharebava, T.; Didmanidze, N. Influence of technological 412
parameters of ultrafiltration process of vegetable juices on their quality. In Proceedings of the 413
International Multidisciplinary Scientific GeoConference SGEM. 30 June -6 July 2019, Albena, Bulgaria. 414
19(2.1), pp. 321-328. 415
19 Zabolo tsky, V.; Novak , L.; Kovalenko , A.; Nikonenko , V.; Urtenov , M.; Lebedev , K. But A.: Electroconvection 416
in Systems with Heterogeneous Ion -Exchange Membranes. Petroleum Chemistry , 2017, 57, (9), 779–789. 417

17 of 20
20 Tufa , R.; Curcio , E.; Van Baak , W.; Veerman , J.; Grasman , S.; Fontananova , E. Potential of brackish water 418
and brine for energy generation by salinity gradient powerreverse electrodialysis”, (SGP -RE), RSC Adv., 419
4 (2014), pp. 42617 –42623,2014. DOI: 10.15587/1729- 4061.2016.75338 420
21 Vasylkivskyi, I. ; Ishchenk o, V. ; Pohrebennyk, V.; Palamar, M. ; Palamar , A. System of water objects 421
pollution monitoring . In Proceedings of the International Multidisciplinary Scientific GeoConference 422
SGEM, Vienna, Austria, 27 November – 29 November 2017, 33 (17), pp. 355– 362. 423
22 Petrov, O. ; Petrichenko, S.; Yushchishina, A.; Mitryasova, O.; Pohrebennyk, V. Electrospark Method in 424
Galvanic Wastewater Treatment for Heavy Metal Removal . Applied Sciences 2020, 425
10(15) , 5148; https://doi.org/10.3390/app10155148 426
23 Bejanidze, I. Save natural -save your life. Georgia National Science Academy Bulletin 2010 , 36(1), 76–84. 427
24 Daniilidis, A.; Vermaas, D.; Herber, R.; Nijmeijer, K. Experimentally obtainable energy 428
from mixing river water, seawater or brines with reverse electrodialysis, Renew. Energy 2014, 64, 123 -131, 429
doi: http://dx.doi.org/10.1016/j.renene.2013.11.001 430
25 Kharebava, T.; Bejanidze, I.; Koncelidze, Z.; Koncelidze, L Transfer of manganese and iron ions with ionic 431
exch ange membranes. International Scientific Conference „Kolkha 2009 “. Collection of works. Kut aisi, 432
2009, pp. 111 -114. 433
26 Sillanpaa, M. Advanced Water Treatment. Electrochemical Methods. Elsevier, 2020 , 382 p. 434
ISBN: 9780128192276 435
27 Hurwitz, H.; Dibiani, R. Experimental and theoretical investigations of steady and trans ientstates in 436
systems of ion exchange bipolar membranes. J. Membr. Sci. 2004 , 228, 17-43. 437
28 Kang, M.; Choi, Y.; Lee, H.; Moon, S. Effects of inorganic substances on water splitting in ion-exchange 438
membranes II. Optimal contents of inorganic substances in preparing bipolar membranes. J. Colloid and 439
Interface Sci. 2004 , 273, 533-539. 440
29 A. Basile, A.; Cassano, A.; Rastogi, N. Advances in Membrane Technologies for Water Treatment. 441
Materials, Processes and Applications Woodhead Publishin g, 2015, 666 p. ISBN: 9781782421214 442
30 Dorofeeva, L. Separation and purification of substances by membrane, exchange and elec trochemical 443
methods. Tomsk. TPU, 2008 , 111 p. (In Russia) 444
31 Tanaka, Y. Water dissociation reaction generated in an ion exchange membrane. 445
J. Membr. Sci . 2007, 303, pp. 234. 446
32 Serdiuk, V.; Sklavbinskyi, V.; Bolshanina, S.; Ivchenko, V.; Qasim, M.; Zaytseva, K. Membrane 447
Processes during the Regenerat ion of Galvanic Solution. Jour nal of Engineering Scien ces 2018, Sumy: Sumy 448
State University, 5(2), pp . F1-F6. 449
33 Wilhelm, F. Bipolar membrane electrodialysis: Ph. D. thesis. – Twente: University of Twente. 2001, 235 p. 450
34 Xue, Y.; Wang, N.; Huang, C.; Cheng, Y.; Xu, T. Catalytic water dissociation at the intermediate layer of a 451
bipolar membrane: The role of carboxylated Boltorn® H30. J. Membr. Sci . 2009 , V. 344, 129-135. 452
35 Sillanpaa, M. Advanced Water Treatment. Adsorption. Elsevier, 2020 , 694 p. ISBN: 9780128192160 453
36 Kao, D. Study on the leachable behavior of cation exchange resins. Journal of Nuclear Science and 454
Technology , 2016 , 53(6), 921– 927. 455
37 Pal, P. Membrane -Based Technologies for Environmental Pollution Control. Butterworth- 456
Heinemann, (2020), 784 p. 9780128194553 457
38 Niftaliev , S.; Kozaderova, O.; Kim, K.; Velho, F. The use of electrodialysis to obtain acid and alkali from a 458
concentrated solution of sodium sulfate. Bulletin of VGUIT 2014 , 4. 175-178. ( In Russia) 459

18 of 20
39 Nikonenko, V.; Pismensk aya, N.; Belova , E.; Sistat, P.; Huguet, P.; Pourcelly, G., Larchet, I. Intensive 460
current transfer in membrane systems: Modelling, mechanisms and application in electrodialysis. 461
Advances in Colloid and Interface Science 2010 , 160, 101–123. 462
40 Shatalov, V.; Savelyeva,T.; Glukhova,L. The use of electrodialysis to obtain regeneration solutions in the 463
ion-exchange process of whey demineralization. FSUE VNII chemical technology, Moscow Series. Critical 464
technology. Membranes 2003 , 3 (19), 38 -40. ( In Russia). 465
41 Sinelnikov, A.; Shcherbakov, P.; Berenda, A.; Malkov,V. Electro -membrane synthesis of glycolic acid. 466
Bulletin of Tomsk State University 2014 , 380, 230-236. ( In Russia). 467
42 Bezhanidze, I.; Kharebava, T.; Koncelidze, Z. The use of bipolar electrodialys is for processing juice 468
production waste. Science Review 2018, Vol. 2, 1 (8), 35 -38. 469
43 Kharebava, T.; Bezhanidze, I.; Kontselidze, Z.; Kontselidze, L. Transfer of manganese and iron ions to ion 470
exchange membranes. International Scientific Conference "Kolkha 2009" Proceedings. Kutaisi, 2009, pp. 471
111-114. 472
44 Donskikh, A. A method for regulating serum acidity during electrodialysis. Pat. No. 2515096 of the 473
Russian Fede ration, IPC B01D 61/42, patent owner of Innovative Food Technologies LLC. No. 474
2012145182/10, declared 10.24.2012; publ. 05/10/2014. Bull. Number 13. Access date 14.10.2018 (Russia). 475
45 Shmandiy, V.; Bezdeneznych , L.; Kharlamova, O.; Svjatenko , A.; Malovanyy, M.; Petrushka, K.; 476
Polyuzhyn, I. Methods of salt content stabilization in circulating water supply systems. 477
Chemistry & Chemical Technology 2017 , 11(2), 242 –246. 478
46 Bezhan idze, I.; Kharebava , T. Monograph: Ultrafiltration and Ele ctrodialysis in Industry . Publishing 479
House "Shota Rustaveli State University". Batumi, 2009, 153 p. 480
47 Tedesco, M.; Brauns, E.; Cipollina, A.; Micale, G.; Modica, P.; Russo, G.; Helsen, J. Reverse Electrodialysis 481
with saline waters and concentrated brines: a laboratory investigation towards technology scale -up. J. 482
Memb. Sci. 2015 , 492, 9-20. 483
48 Kharebava, T.; Bejanidze, I.; Jibladze, K. The effect of microbiological corrosion on the properties of 484
polymer materials used in membrane technology. RSU's Works, Natural Sciences, Medicine 2008, Batumi, 485
XII, 174 – 178. 486
49 Singh, R.; Hankins, N. Emerging Membrane Technology for Sustainable Water Treatment . Elsevier 487
Science, 2016 , 480 p. ISBN: 9780444633125 488
50 Gotsiridze, R.; Kontselidze,L.; Kharebava, T.; Kontselidze, Z. Description of the technological scheme of 489
wastewater treatment in the galvanizing shop. Materials of the International Scientific and Practical 490
Conference "Innovative Technologies and Environmental Protection". Kutaisi. 30 -31 May , 2012. 491
51 Zabolotsky, V.; Utin, S.; Sheldeshov, N.; Lebedev, K.; Vasilenko, P. Investigation of the process of pH 492
adjustment of d ilute electrolyte solutions by electrodialysis with bipolar membranes. Electrochemistry 493
2011, 47(3), 343-348. 494
52 Kharebava, T.; Bezhanidze, I. Investigation of selectivity of polymer membranes. International 495
Scientific -Practical Conference "Innovative Technologies and Modern Materials". Collection of works. 496
Akaki Tsereteli State University, Kutaisi, 2010, pp. 386-389. 497
53 Winiewski, J.; Wigniewska, G.; Winnicki, T. Application of bipolar electrodialysis to the recovery of acids 498
and bases from wa ter solutions. Desalination 2004 , 169, 11-20. 499
54 Xu, T. A simple model to determine the trends of electric -field-enhanced water dissociation in a bipolar 500
membrane. II. Consideration of water electrotransport and monolayer asymmetry . Desalination 2006 , 190, 501
125-136. 502

19 of 20
55 Kharebava, T.; Loria, L.; Kajaia, T.; Ispiriani, A.; Kontselidze, L. Development and testing of a new 503
hydraulic circuit of the electrodialyzer to obtain deeply salted water. Scientific -peer-reviewed journal of the 504
Georgian Academy of Sciences "Science and Technologies" . 2006, Tbilisi. 4–6, 121 -124. 505
56 Wilhelm, F. Bipolar M embrane Electrodialysis. Ph.D. thesis University of Twente, 2001, 235 p. 506
57 Pourcelly, G. Bipolar membrane applications , Chapter 2 in A. Kemperman (ed), Handbook on Bipolar 507
Membrane Technology. Twente University Press, Enschede, The Netherlands, ISBN 90365152 03, 2000. 508
58 Jibladze, K.; Kharebava, T.; Bezhanidze, I., Tsagareli, M. Influence of microbiological corrosion on the 509
properties of polymeric materials used in membrane technology. Proceedings of RSU, Natural Sciences 510
Medicine 2008 , Batumi, XII. 174 –178. 511
59 Serdiuk, V.; Sklabinskyi , V.; Bolshanina, S.; Ableyev A., Dychenko T. Prevention of Hydrosphere 512
Contamination with Electroplating Solutions through Electromembrane Processes of Regeneration. 513
Journal of Ecological Engineering 2020, 21(4), 61–69. 514
60 Kharebava, T. ; Jibladze, K. To determine the specific composition of microorganisms that cause 515
microbiological corrosion of ion exchange membranes and polymeric materials used in electromembrane 516
technology. Scientific -peer-reviewed journal of the Georgian Academy of Sciences "Science and Technologies" . 517
2006, Tbilisi. 4–6, 127–129. 518
61 Zhang, Y.; Ghyselbrecht, K.; Meesschaert, B.; Pinoy, L.; Van der Bruggen, B. Electrodialysis on 519
RO concentrate to improve water recovery in wastewater reclamation. 520
J. Membr. Sci . 2011, V. 378, 101- 110. 521
62 Merkel, A.; Ashrafi, M.; Ecer, J. Bipolar membrane electrod ialysis assisted pH correction of milk whey. 522
Journal of Membrane Science . 2018, 555, pp. 185-196. 523
63 Bezhanidze, I.; Kharebava, T.; Koncelidze,Z.; Gorjeladze,D. Study of the possibility of membrane 524
regeneration without disasse mbly of the electrolytic device. Bulletin of Georgian Academy of Agricultural 525
Sciences, 2007 , 19, p. 199–202 526
64 Zabolotsky, V.; Utin, S.; Sheldeshov, N.; Lebedev, K.; Vasilenko, P. Investigation of the process of pH 527
adjustment of dilute electrolyte solutions by electrodialysis with bipolar membranes. Electrochemistry 528
2011, 47(3), pp. 343 -348. 529
65 Xue, Y.; Wang, N.; Huang, C.; Cheng, Y.; Xu,T. Catalytic water dissociation at the intermediate layer of a 530
bipola r membrane: The ro le of carboxylated Boltorn® H30 . J. Membr. Sci. 2009 , 344, 129-135. 531
66 Kharebava, T.; Bezhanidze, I. Simultaneous salinization -concentration of nickel -containing waters by 532
electrodialysis method. International Scientific -Technical Conference "New Technologies in Modern 533
Industry". Proceedings, Georgian Technical University, Tbilisi, 2010, pp. 113– 115. 534
67 Description of technological scheme of wastewaters purification of galvanic production zink plating 535
factory. Inte rnational Scientific -Practical Conference "Innovative technologies and environment 536
protection" works. Akaki Tsereteli State University, Kutaisi , 2012. 537
68 Kharebava, T.; Loria, L.; Kajaia, T.; Ispiriani, A.; Kontselidze, L. Separation of charged ions with the same 538
sign in binary solution by electrodialysis method. Scientific -peer-reviewed journal of the Georgian Academy of 539
Sciences "Science and Technologies " 2006, Tbilisi, 1–3, 144-147. 540
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