Solubility in the Na,Ca||SO4,HCO3-H2O system at 25 °C 130 D O I: 1 0. 15 82 6/ ch im te ch .2 01 9. 6. 4. 02 Soliev L., Jumaev M. T., Varkaeva A. M., Makhmadov Kh. R., Sinoi G. Chimica Techno Acta. 2019. Vol. 6, No. 4. P. 130–137. ISSN 2409–5613 Soliev L., Jumaev M. T., Varkaeva A. M., Makhmadov Kh. R., Sinoi G. Tajik State Pedagogical University named after S. Ayni 121 Prospect Rudaki, Dushanbe, 734003, Tajikistan e-mail: Soliev.lutfullo@yandex.com, Jumaev_m@bk.ru Solubility in the Na,Ca||SO4,HCO3–H2O system at 25 °C Water solubility at 25 °C was studied in the four-component water-salt system comprised of sodium and calcium sulfates and hydrocarbonates in order to de- termine the concentration parameters of solution and crystallization of the con- stituent salts and to experimentally verify the phase equilibria in the geometric images of the system predicted previously by the translation method. The pre- diction of possible phase equilibria in geometric images of the system, followed by plotting its phase diagram, appreciably decreases the time and material costs of experimentation and improves the reliability of results. Our results can serve both as reference information and as a scientific base for optimizing the param- eters of natural and artificial processes, in particular, the recycling of salt from liquid waste of aluminum production facilities. Keywords: sodium; calcium; sulfate; hydrocarbonate; solubility diagram Received: 07.10.2019. Accepted: 10.12.2019. Published: 30.12.2019. © Soliev L., Jumaev M. T., Varkaeva A. M., Makhmadov Kh. R., Sinoi G., 2019 Introduction T h e   fou r- c omp on e nt Na , Ca||SO4, HCO3–H2O system is a constitu- ent of the more complex six-component Na,Ca||SO4,CO3,HCO3,F–H2O system; the phase equilibria in the latter determines the conditions for recycling of aluminum liquid waste. The  wastewater after cryo- lite recovery in aluminum plants contains fluorides, carbonates, hydrocarbonates and sulfates of sodium and calcium [1, 2]. In this paper we have examined the con- centration parameters of equilibrium solid phases for the particular crystallization fields in the Na,Ca||SO4,HCO3–H2O system stud- ied by the solubility method at 25 °C. Phase equilibria in the form of phase diagram es- tablished by the translation method were studied in our previous work [3]. The  use of  the  translations method for predicting and constructing of phase diagrams for various systems is based on the principle of compatibility of the struc- ture of constituent n-component systems with elements of the structure of a common (n+1) component system in one diagram [4]. According to the translation method, while the components number in the sys- tem is increasing from n to n+1, the geo- metric images of constituent n-component systems (i.e. nonvariant points, monovari- ants curves, divariant fields) are increasing their dimension by one, i.e. they have trans- formed and translated into the general area of (n+1) component composition. At a level of (n+1) — component compo- sition, transformed by the translation proce- 131 dure geometrical images of the n-component constituent systems involved in the forma- tion of the phase complex of the overall sys- tem, in accordance with their topological properties and requirements of the Gibbs phase rule [5]. Based on the obtained data, it is possible to construct an isolated phase diagram of the studied system. The application of the translation method for predicting and constructing phase dia- grams for multicomponent water-salt sys- tems is described in detail elsewhere [6–7]. The  use of  the  translation method for prediction and construction of phase diagrams of multicomponent systems sig- nificantly reduces the  time and material expenses of  experimental study of  vari- ous systems [9–11] constituting the  six- component Na,Ca||SO4,CO3,HCO3,F– H2O system. The equilibrium solid phases of the system under study at 25 °C are cal- cium hydrocarbonate, nahcolite, mirabilite, and gypsum [12, 13]. Experimental Fol low ing re agents were us e d in  our work: Na2SO4 · 10H2O; NaHCO3; Ca(HCO3)2; CaSO4 · 2H2O. The  ex- periments were carried out according to  the  “until saturation” method in  ac- cordance with the  following. Based on the  data reported in  works [3–15], we preliminary prepared the  mixtures of  precipitates with saturated solutions corresponded to  the  nonvariant points of the ternary systems, namely: Na2SO4– NaHCO3–H2O; CaSO4–Ca(HCO3)2–H2O; Na2SO4–CaSO4–H2O and NaHCO3– Ca(HCO3)2–H2O at 25 °C, which are con- stituting the four-component system under study. Then, according to the translation scheme, the nonvariant points of the level of  three-component system were trans- formed to  the  level of  four-component system [3] by  the  mixing of  appropriate amounts of the prepared saturated solu- tions with the corresponding equilibrium solid phases at 25 °C in an ultrathermostat U-8 with stirring using magnetic stirrers PD-09 for 50–100 h. The temperature was maintained with an  accuracy of  ±0.1  °C using a contact thermometer. The crystal- lization of the solid phases was detected using a POLAM-R 311 microscope. After reaching an equilibrium state in the sys- tem, the  equilibrium solid phases were photographed with a SONY — PSC 500 digital camera. The achievement of equilib- rium was judged by the unchanged phase composition of precipitation. Separation of liquid and solid phases was carried out with the help of a vacuum pump through a  desalted (blue ribbon) filter paper on a Büchner funnel. The  precipitate after filtration was wasted with 96% ethyl alcohol and dried at 120 °C. Chemical analysis of products was carried out using well-known methods described elsewhere [15–17]. Results and discussion The  micrographs of the  crystalline equilibrium solid phases are presented in Fig. 1, and the results of chemical analy- sis of  saturated solutions are presented in Table 1. The phases are denoted as fol- lows: CaH  — calcium hydrocarbonate, Ca(HCO3)2; Gp — gypsum, CaSO4 · 2H2O; Mb — mirabilite, Na2SO4 · 10H2O; Nh — nahcolite, NaHCO3; Gb  — glauberite, Na2SO4 · CaSO4. 132 Fig. 1. Micrographs of equilibrium solid phases of the Na,Ca||SO4,HCO3-H2O system at 25 °C 133 Based on the obtained results, the solubil- ity diagram for the Na,Ca||SO4,HCO3–H2O system at 25 °C was constructed (Fig. 2). The  location of  invariant points at each level of the diagram within three- component (En 3) and four-component (En 4) systems under study was established by  the  mass-centric method [19, 20]. The  mass-centric method which is  used for presentation of multicomponent sys- tems allows changing the  scale of  one of  the  constituent parts without distur- bance of the general diagram laws, and it also allows using the polygon area more ra- tionally, i.e. to increase the length of small individual geometric images. This is espe- cially important when the solubility of salts in water is small and the use of the same scale leads to the situation when the figu- rative point of  the  mixture is  shifted to- wards the water angle while constructing of water-salt system diagrams. Fig. 2 shows the total (a) and salt (b) parts of  the  solubility diagram for the  Na,Ca||SO4, HCO3–H2O system at 25 °C, where the relative position and the relative sizes of the crystallization fields for the  corresponding equilibrium solid phases are reflected. As follows from Fig. 2, the crystallization fields of Ca(HCO3)2 and CaSO4·2H2O occupy a  significant part of  the  solubility diagram for the  studied four-component system, which character- izes the low solubility of these salt in water solution of given content at 25 °C. A de- scription of  content for the  geometric images (fields, curves, points) in  Fig.  2 is given in Table 2. Table 1 The solubility values of various salts correspondent to the invariant points in the Na,Са||SO4,НСО3–H2O system at 25 °С Point no. Liquid phase, wt. % Phase composition of precipitates NaНСО3 Na2SO4 Са(НСО3)2 CaSO4 H2O е1 9.31 – – – 90.69 Nh е2 – 21.9 – – 78.10 Mb е3 – – 0.0160 – 99.984 CaH е4 – – – 0.219 99.78 Gp 3 1E 4.16 20.68 – – 75.16 Nh+Mb 3 2E 4.89 – 0.0109 – 95.09 Nh+CaH 3 3E – – 0.0168 0.186 99.797 CaH+Gp 3 4E – 21.75 – 0.197 78.05 Mb+Gp 3 5E – 25.78 – 0.188 74.03 Gb+Gp 4 1E 5.20 28.38 – 0.270 66.15 Nh+Mb+Gb 4 2E – 25.14 0.0136 0.184 74.66 Gb+Gp+CaH 4 3E 7.12 24.40 0.0163 – 68.46 Nh+CaH+Gb 134 Fig. 2. (a) General and (b) salt-area solubility diagrams for the Na,Ca||SO4,HCO4–H2O system at 25 °C b a 135 Table 2 Description of the content for the geometric images in Fig. 2 Designation Content e1 Solubility of sodium hydrocarbonate in water e2 Solubility of sodium sulfate in water e3 Solubility of calcium hydrocarbonate in water e4 Solubility of calcium sulfate in water Е1 3 Joint crystallization point Mb+Nh in the system NaHCO3–Na2SO4–H2O Е2 3 Joint crystallization point Nh+CaH in the system NaHCO3–Ca(HCO3)2–H2O Е3 3 Joint crystallization point CaH+Gp in the system Ca(HCO3)2–CaSO4–H2O Е4 3 Joint crystallization point Mb+Gb in the system Na2SO4–CaSO4–H2O Е5 3 Joint crystallization point Gp+Gb in the system Na2SO4–CaSO4–H2O Е1 4 Joint crystallization point Nh+Mb+Gb in the system Na,Ca||SO4,HCO3–H2O Е2 4 Joint crystallization point CaH+Gb+Gp in the system Na,Ca||SO4,HCO3–H2O Е3 4 Joint crystallization point Nh+Gb+CaH in the system Na,Ca||SO4,HCO3–H2O Е1 3 Е1 4 Curve of the joint crystallization of Nh+Mb in system NaHCO3–Na2SO4–H2O Е2 3 Е3 4 Curve of the joint crystallization of Nh+CaH in system NaHCO3–Ca(HCO3)2–H2O Е2 3 Е2 4 Curve of the joint crystallization of CaH+Gb in system Ca(HCO3)2–CaSO4–H2O Е4 3 Е1 4 Curve of the joint crystallization of Mb+Gb in system Na2SO4–CaSO4–H2O Е5 3 Е2 4 Curve of the joint crystallization of Gb+Gp in system NaHCO3–Na2SO4–H2O Е1 4 Е3 4 Curve of the joint crystallization of Nh+Gb in system Na,Ca||SO4,HCO3–H2O Е2 4 Е3 4 Curve of the joint crystallization of CaH+Gb in system Na,Ca||SO4,HCO3–H2O NaHCO3E1 3E1 4E3 4E2 3NaHCO3 Crystallization field Nh Ca(HCO3)2E2 3E3 4E2 4E3 3 Ca(HCO3)2 Crystallization field CaH Na2SO4E1 3E1 4E4 3Na2SO4 Crystallization field Mb CaSO4E3 3E2 4E5 3CaSO4 Crystallization field Gp E4 3E1 4E3 4E2 4E5 3E4 3 Crystallization field Gb (I) Notation of the figurative point of the mixture in the water-salt area of the diagram 136 References 1. Morozova VA, Rzhechitskii EP. Solubility in the NaF–Na2SO4–NaHCO3–H2O system at 0 °C. Russian Journal of Applied Chemistry. 1976;49(5):1152–4. Russian. 2. Morozova VA, Rzhechitskii EP. Solubility in the systems NaF–NaHCO3–H2O, NaF– Na2SO3–H2O and NaF–Na2CO3–H2O at 0 °C. Russ J Inorg Chem. 1977;22(3): 873–4. Russian. 3. Soliev  L., Dzhumaev  M. T., Nuri  V., Avloev  Sh. Kh.  Phase equilibria in Na,Ca||SO4,HCO3–H2O system at 25 °C. Vestnik Tadjikckogo natsional’nogo universiteta (seriya estesvennikh nauk) [Bulletin of the Tajik National University (series of natural sciences)]. 2012;1/3(85):221. Russian. 4. Goroshchenko YaG. Fiziko-khimicheskiy analiz gomogennykh I geterogennykh sistem [Physicochemical Analysis of Homogeneous and Heterogeneous Systems]. Kiev: Naukova Dumka; 1978. 490 p. Russian. 5. Anosov VYa, Ozerova MI, Fialkov YuYa. Osnovy fiziko-khimicheskogo analiza [Major Methods of Physicochemical Analysis]. Moscov: Nauka; 1976. 504 p. Russian. 6. Soliev  L.  Prediction of  Phase Equilibria in  Multinary Marine-Type Systems by the Translation Method, Book 1. Dushanbe: TSPU; 2000. Russian. 7. Soliev  L.  Prediction of  Phase Equilibria in  Multinary Marine-Type Systems by the Translation Method, Book 2. Dushanbe: TSPU; 2011. Russian. 8. Soliev  L. [Prediction of  Phase Equilibria in  Multinary Marine-Type Systems by the Translation Method, Book 3]. Dushanbe: R-Graph; 2019. Russian. 9. Soliev L, Dzhumaev MT, Avloev ShH, Toshov AF. Solubility in the CaSO4–CaCO3– Ca(HCO3)2–H2O system at  0 °C.  Doklady akademii nauk Respubliki Tajikistan [Reports of the Academy of Sciences of the Republic of Tajikistan]. 2015;58(2):139. Russian. 10. Dzhumaev MT, Soliev L, Dzhabborov BB, Ikbol G. Solubility in the Na,Сa||СО3, НСО3 — H2O System at 25 °С. Russ J Inorg Chem. 2017;62(9):1245–51. DOI:10.1134/S0036023617090169 11. Soliev L, Dzhumaev MT, Dzhabborov BB. Solubility and phase equilib- ria in  the  Na,Са||СО3, НСО3–H2O system at  0 °С.  Chimica Techno Acta. 2017;4(3):191–201. DOI:10.15826/chimtech/2017.4.3.04. 12. Spravochnik eksperimental’nykh dannykh po rastvorimosti mnogokomponent- nykh vodno-solevykh system [Reference book on experimental data for solubility in multicomponent water-salt systems]. Vol. 1. Saint-Petersburg: Khimizdat, 2003. 1151 p. Russian. 13. Spravochnik eksperimental’nykh dannykh po rastvorimosti mnogokomponentnykh vodno-solevykh system Reference book on experimental data for solubility in mul- ticomponent water-salt systems. Vol. II., Books. 1–2. Saint-Petersburg: Khimizdat, 2004. 1247 p. Russian. 14. Goroshchenko YaG, Soliev L, Gornikov YuI. Opredelenie polozheniya nonvariant- nykh tochek na diagrammakh rastvorimosti metodom donasyshcheniya [Determina- tion of the invariant points’ positions on solubility diagrams using the presaturation 137 method]. Ukrainskii Khimicheskii Zhurnal [Ukrainian Journal of  Chemistry]. 1987;53(6):568–71. Russian. 15. Kreshkov AP. Osnovy analiticheskoy khimii [Basics of Analytical Chemistry]. Vol. 2. Leningrad (USSR): Khimiya, 1970. 456 p. Russian. 16. Knipovich YuN, Morachevskii YuV, editors. Analiz mineral’nogo syr’ya [Analysis of mineral raw materials]. Leningrad: Goskhimizdat, 1959. 947 p. Russian. 17. Reznikov AA, Mulikovskaya EP, Sokolov IYu. Metody analiza prirodnykh vod [Methods of natural water analysis]. Moscow: Nedra, 1970. 488 p. Russian. 18. Tatarskii VB. Kristallooptika i immersionnyy metod analiza veshchestv [Crystal Op- tics and Immersion Method of Substances Analysis]. Leningrad (USSR): Izdatel’stvo LGU, 1948. 268 p. Russian. 19. Goroshchenko YaG, Soliev L, Savchenko LT, Mardanenko VKh, Romanenko ON, Zharovskiy IV, Borisenko LA. Sistema Na, К, Mg // SO4, Сl-Н2O pri 100 °С [Na, К, Mg // SO4, Сl-Н2O system at 100 °С]. Zhurnal Neorganicheskoy Khimii [Russ J Inorg Chem]. 1977;22(11):3129–34. Russian. 20. Goroshchenko YaG. Masstsentricheskiy metod izobrazheniya mnogokomponent- nykh system [The Center of Mass Method for Multi-component Systems Imaging]. Kiev: Naukova Dumka, 1982. 264 p. Russian.