Kazakhstan ranks second in the world in natural uranium reserves and a leading position in its production. Hydrometallurgical processing of uranium raw materials results in a significant amount of liquid technogenic wastes containing radionuclides. Sorption cleaning methods for these wastes are the most effective ones. However, the high cost of synthetic sorbents and the low sorption capacity of natural ones is a deterrent to their use. So, to increase the sorption capacity of natural sorbents by their modification is an urgent problem. In this paper, a method to modify Kazakhstani natural zeolite was proposed by us and previously not investigated. Also the data of physicochemical studies of the initial raw material and the modified product was given and the increase in the natural sorbent specific surface in the modification process was demonstrated

A. N. Berkinbayeva

B. E. Abdikerim

B. K. Kenzhaliyev

T. Yu. Surkova

Z. D. Dosymbayeva

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117METALURGIJA 59 (2020) 1, 117-120B. K. KENZHALIYEV, T. YU. SURKOVA, A. N. BERKINBAYEVA, Z. D. DOSYMBAYEVA, B. E. ABDIKERIMREVISITING THE KAZAKHSTAN NATURAL SORBENTS MODIFICATION Received – Primljeno: 2019-07-03Accepted – Prihvaćeno: 2019-09-03Preliminary Note – Prethodno priopćenjeB. K. Kenzhaliyev (e-mail: bagdaulet_k@mail.ru) JSC “Satbayev Uni-versity after K. I. Satpaev”, T. Yu. Surkova, A. N. Berkinbayeva, Z. D. Dosymbayeva, B. E. Abdikerim JSC “Institute of Metallurgy and Ore Benefi cation”, Almaty, KazakhstanKazakhstan ranks second in the world in natural uranium reserves and a leading position in its production. Hydro-metallurgical processing of uranium raw materials results in a significant amount of liquid technogenic wastes con-taining radionuclides. Sorption cleaning methods for these wastes are the most effective ones. However, the high cost of synthetic sorbents and the low sorption capacity of natural ones is a deterrent to their use. So, to increase the sorption capacity of natural sorbents by their modification is an urgent problem.In this paper, a method to modify Kazakhstani natural zeolite was proposed by us and previously not investigated. Also the data of physicochemical studies of the initial raw material and the modified product was given and the in-crease in the natural sorbent specific surface in the modification process was demonstrated. Key words: zeolite, modification, activation, raw material, KazakhstanINTRODUCTIONA significant amount of liquid technogenic wastes - waste solutions are produced in the course of hydromet-allurgical processing of uranium-containing raw mate-rials.Industrial products and wastes from the uranium in-dustry contain rare earth elements and radionuclides [1]. The sorption, precipitation and membrane process-based methods are used most often to extract radionu-clides thereof. The choice of one or another method depends on the chemical and radionuclide composition of liquid radioactive waste (LRW) and is determined under the state of the radionuclides in the solution. The use of sorption methods is one of the most effective methods to clean objects contaminated with radionu-clides and, in particular, water. Today, sorption purifica-tion methods using synthetic and natural sorbents are the most common and effective, and they have no alter-natives in many cases.The disadvantage of synthetic sorbents is their high cost, and that of natural ones is low exchange capacity. In order to increase the sorption properties, natural ma-terials used for cleaning solutions undergo different modifications. At the same time, there are no actual methods to obtain modified sorbents that would be well-proven in the uranium sorption process. So, the problem to obtain modified sorbents based on natural raw materials remains relevant for the nuclear industry. ISSN 0543-5846METABK 59(1) 117-120 (2020)UDC – UDK 553.495.001.43:541.124:388.987.4:479=111METHODS OF ANALYSISThe elemental and phase compositions of natural zeolites were determined tith the help of X-ray fluores-cence and X-ray phase analyzes using Venus 200 X-ray fluorescence wave dispersion spectrometer made by PANalytical and a D8 Advance diffractometer made by Bruker (Cu –Kα radiation).The quantitative uranium content in solutions before and after sorption with the help of an Optima 8000DV inductively coupled plasma (ICP) atomic emission spectrometer was determined.RESULTS AND ITS DISCUSSIONZeolites are widely used among inorganic ion ex-changers. In their turn, in terms of practical importance, first of all, high-silica zeolite - clinoptilolite – can be distinguished among zeolites due to its high sorption properties and selectivity.Natural zeolite-containing minerals are subject to close attention of researchers because they are much cheaper materials compared with synthetic zeolites.At the same time, the demand for natural sorbents imposes the need to study the possibility to use mineral raw materials produced in newly discovered and little-studied deposits in order to develop the conditions for their modification and subsequent targeted use.The zeolites produced in the Shankhayskoye field with 80 % composed of sodium-type clinoptilolite are the most thoroughly investigated among the Kazakh-stani ones. The mineralogical and chemical composi-tion of the averaged sample of natural zeolites previ-118B. K. KENZHALIYEV et al.: REVISITING THE KAZAKHSTAN NATURAL SORBENTS MODIFICATION METALURGIJA 59 (2020) 1, 117-120ously unexplored originated from northern Kazakhstan was studied (the Kusmurynskoye deposit).Table 1 presents the zeolite elemental composition under X-ray fluorescence analysis.Table 1  The original natural zeolite elemental composition / wt. %Components ContentSiO2 62,2Al2O3 13,4Fe2O3 5,9Na2O 1,6CaO 5,3К2O 6,5MgO 2,2P2O5 0,4MnO 0,2TiO2 0,5SiO2/ Al2O3 1,8Others 4,6As specified in the table, the ratio of the main com-ponents - SiO2 / Al2O3 cations is 4,6 confirming the ag-gressive substances and high temperatures resistance of the zeolite studied.The phase composition is represented by clinoptilo-lite, quartz, albite, diopside, hematite, lomonite, ernite. The results of the phase analysis confirm the prevalence of clinoptilolite and quartz in the zeolite composition, and those of mineralogical analysis - calcium-form clinoptilolite.Thermogravimetric studies (TG, DTA, DTG) supple-mented the zeolite phase composition information with the presence of a small amount of harmotome and chabazite.Thus, the Northern Kazakhstan zeolites to be stud-ied belong to the calcium-form zeolite less studied and not typical for the Kazakhstani zeolite raw materials studied (Figure 1).The zeolite structure specificity resulting in its prop-erties makes it an attractive and promising material for sorption processes, but its low sorption capacity is an obstacle to its widespread use. Due to it, the task to im-prove the sorption properties of natural ion-exchange materials, or their modification, comes to prominence.There are different methods to change the structural features of natural sorbents enabling to improve their properties. However, a common disadvantage of the methods described is the complexity of the perfor-mance, high cost and use of scarce reagents.There is limited data on uranium sorption by modi-fied zeolites in the scientific literature. Basically, the modification principles include coating the zeolite sur-face with hydroxides of metal [2, 3], such as iron, zinc and copper.The sorption capacity of zeolites increases, and the possibility to use them in the uranium recovery technol-ogy and LRW disposal is growing in this case. However, these methods are difficult to implement, and therefore, the new modified reagents search and the development of new modification methods remain urgent problems.Modification, as a rule, results in phase and some-times structural changes of natural sorbents. Phase changes are also observed when natural sorbents are processed with chemical reagents, such as acids, alka-lis, and salts. These changes are not as dramatic as in the methods specified above but they have a positive effect on the sorption capacity of sorbents [4, 5].It should be noted that there is quite extensive infor-mation about the sorption properties of zeolite minerals with respect to 137Cs and 90Sr isotopes in the scientific literature; moreover, the greatest exchange capacity for these components is typical for natural calcium-form clinoptilolite [5]. But such information is limited for uranium.During the research the activation process of alumino-silicates with acids, alkalis, and salts, and carried out ex-Figure 1 Zeolite Thermogram119B. K. KENZHALIYEV et al.: REVISITING THE KAZAKHSTAN NATURAL SORBENTS MODIFICATIONMETALURGIJA 59 (2020) 1, 117-120periments to sorb uranium from technological solutions with activated materials in a static mode was studied.The activation was carried out as follows. Transfer 5 g zeolite sample into a beaker, pour 50 ml HCl, NH4Cl or NaOH solution with a certain concentration and keep at room temperature within two days. Then filter it, dry at 400 ° C and analyze. Activate the sample with 1,75 N HCl solution boiling it within 30 minutes.Tabular data (Table 2) confirm that after activation with hydrochloric acid under the normal conditions, the aluminum content is reduced by 30,6 %, that of magne-sium – 22,8 %, calcium – 53,95 %, the silicon content increases by 29,6 %, that of iron – by 27,4 %, at elevat-ed temperatures – respectively, Al – 23,5 %, Mg – 48,11 %, Ca – 35,23 %, Si – 19 %, Fe – 8,9 %.When activated with sodium hydroxide, the alu-minum content decreases by 2,7 %, calcium one in-creases by 41,02 %, the content of iron and silicon prac-tically does not change. Processing a zeolite sample with ammonium chloride results in the iron content in-crease by 14,6 %, on average, and the content of silicon and calcium changes slightly.Thus, it follows from the above results that the high-est degree of decationization and dealumination was achieved when the zeolite was activated with hydro-chloric acid. With acid activation, the decation and dea-lumination processes proceed simultaneously. This is evidenced by an increase in the silica content with a si-multaneous decrease in the alumina content.The increase in silicate modulus observed in this case indicates phase transformations, which is confirmed by X-ray diffraction studies. According to the author [6], an increase in the silicate module indicates the appearance of active centers, which, in his opinion, can contribute to an increase in the sorption capacity of the zeolite. Ac-cording the X-ray phase analysis of a sample of zeolite after acid activation we can see that phase transforma-tions occurred during the activation process: the content of cliniptilolite, albite, diopside, erinite and hematite de-creased. The transformation of lomontite almost took place. New components have appeared: sodium silicate, calcium silicate carbonate, and terranovite. The quartz content is almost unchanged. When zeolite is activated with hydrochloric acid of a higher concentration, there is decrease in the content of hematite, diopside and clinop-tilolite that is destroyed and transformed, the content of sodium silicate and calcium silicate carbonate increases, a new phase - microcline - appears.Brunauer, Emmett and Taylor studies have shown that the specific surface area increases, and the average pore diameter decreases (Table 3) during the zeolite ac-tivation process contributing to sorption capacity in-crease. At the same time, the zeolite specific surface area increases by 1,5 times after activation.It should be noted that a similar pattern is observed in the uranium sorption with activated zeolite, i.e. the sorption degree increases by 1,5 times, on average.Table 3  Properties of natural zeolites before and after activationName Zeolite No.1 (initial) Zeolite No.1(after activation)Specifi c surface areaSBET / m231,70 47,55Actual pore volume∑act, / ml/g0,0685 0,0677Average pore diam-eter Dav, / Å43,6337 31,7014Mechanicalstrength / kgf/cm235 - 40 35 - 40CONCLUSIONThus, based on the studies conducted, as well as the authors’ results [3] can be assumed that processing the Table 2  Results of X-Ray fluorescence analysis of zeolite samples after activationName О К Al Si Fe S Na Mg P CaInitial Content/ % 47,12  0,61 6,58 21,51 3,02 0,004 1,46 1,35 0,05 2,232 N HCl Content after acti-vation, %50,58  0,85 4,57 27,88 3,84 0,006 1,27 1,04 0,01 1,031,7N HCl 50,68  0,89 4,69 26,89 3,70 0,005 1,17 1,11 0,008 1,2231N HCl 48,7  0,82 5,38 23,9 3,62 0,01 1,25 1,23 0,01 1,492N NH4Cl 43,51  0,76 6,41 21,02 3,35 0,004 1,29 1,28 0,06 2,331.7 N NH4Cl 47,64  0,78 6,92 22,27 3,54 0,004 1,42 1,41 0,07 2,641 N NH4Cl 48,78  0,82 6,89 22,76 3,47 0,004 1,40 1,37 0,07 2,641.7 NHClwhen boiled46,01  0,85 5,03 25,62 3,29 0,004 1,23 0,70 0,02 1,443 NHCl 49,05  0,88 3,54 27,39 3,31 0,004 0,91 0,79 0,008 0,756 NHCl 49,9  0,84 3,09 29,1 3,06 0,01 0,89 0,72 0,01 0,582 NNaOH 47,59  0,80 6,41 21,16 3,22 0,005 2,10 1,28 0,063 2,904 NNaOH 45,76  0,74 6,31 20,59 3,14 0,003 2,16 1,26 0,05 2,736 NNaOH 48,08  0,79 6,58 21,98 3,46 0,004 2,51 1,31 0,07 3,14120B. K. KENZHALIYEV et al.: REVISITING THE KAZAKHSTAN NATURAL SORBENTS MODIFICATION METALURGIJA 59 (2020) 1, 117-120zeolite-containing rock with acid solutions under differ-ent conditions results in the specific surface increase and the average pore diameter decrease contributing to increase in the sorption capacity due to more active ac-cess of adsorbent molecules to the active centers of the sorbent, i.e. samples of various decationation and dea-lumination degrees can be obtained with the sorption capacity higher than that of the initial ones depending on the conditions of the acid processing of zeolites - the change in the acid concentration, its nature, and the temperature of the process.AcknowledgementsThis work was supported by Committee of Science of the Ministry of Education and Science of Republic of Kazakhstan with the grant No. AR 05131104.REFERENCES[1] B.K. Kenzhaliyev, T.Yu. Surkova, S.B., E.A. Pirmatov, A.P. Dulenin Receiving a concentrate of rare-earth elements of their waste and middlings of the uranium industry, Kom-pleksnoe Ispolʹzovanie Mineralʹnogo Syrʹa 3 (2016), 70-77, www.kims-imio.kz DOI 10.31643/2018/166445[2] D.S. Balpanov, O.A. Ten, N.K. Zhappar, V.M. Shaikhutdi-nov, R.A. Khannanov, Biotechnological methods of rege-neration of three-value iron and sorption of rare and rare-earth metals from circulating solutions of In Situ Leach Mining of Uranium, Kompleksnoe Ispolʹzovanie Mineralʹnogo Syrʹa 4 (2017), 21-26, www.kims-imio.kz DOI 10.31643/2018/166445[3] S. Zhehao, L. Cheng, C. Zhen, Ch. Wei, Study on regene-ration effect and mechanism of high–frequency ultrasound on biological activated carbon, Ultrasonics Sonochemistry 44 (2018), 86-96.[4]  N.F. Chelish’ev, B.G. Berenshtein, N.S. Martynova, Com-parative study of various cationic forms of clinoptilolite, News of AS USSR. Nonorganic Materials 11 (1975) 4, 172-177.[5]  G.V. Tsitsishvilli, T.G. Andronikashvilli, G.N. Kirov, Na-tural zeolits, Chemistry, (1985), 224.[6]  E.E. Ergozhin, A.M. Akimbayeva Organic mineral sor-bents and semi-functional systems based on natural alumi-nosilicate and coal-mineral raw materials, Almaty, 2007, 373.Note:  The responsible translator for the English language is D. Imanku-lova, JSC “KBTU”, Kazakhstan.

Revisiting the Kazakhstan natural sorbents modification

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