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AZERBAIJAN CHEMICAL JOURNAL № 2 2022 ISSN 2522-1841 (Online)
ISSN 0005-2531 (Print)
UDC 541.183/183.7
THE USE OF ALUMINOSILICATE CLAYS AS SORBENTS IN THE PURIFICATION OF
MEDIA FROM HEAVY METAL IONS
Z.R.Agayeva\ S.S.Bayramova1, H.I.Rafiyeva2, Y.B.Gahramanova1, E.M.Kazimova3,
Kh.N.Ilyasova1
1M.Nagiyev Institute of Catalysis and Inorganic Chemistry, NAS of Azerbaijan
2
Baku State University 3Institute of Architecture and Construction
Received 14.10.2021
Accepted 24.12.2021
Shown that galvanic production, which is engaged in the application of protective or decorative coatings on metal and non-metal products (galvanizing, nickel plating, oxidation), can also be attributed to enterprises that pollute the environment with wastewater. Subject to all the norms of the technological process, despite the various methods of surface treatment of products, a certain amount of wastewater of complex composition is still formed. With an inferior degree of purification, they are one of the sources of pollution of aquatic environments. The main toxic components polluting this kind of wastewater are heavy metal ions such as chromium-6, cadmium-2, lead-2 and other toxic substances. Shown that in wastewater treatment the main place belongs to the sorption method, which uses natural sorbents such as activated carbons, zeolites, bentonite clays, and other natural materials. Searched for natural raw materials to obtain effective sorbents during decontamination of industrial effluents. The chemical-mineralogical composition of a number of deposits of aluminosilicate rocks in Azerbaijan has been studied. An analysis of the results obtained made it possible to establish the optimal variant of the synthesis of sorbents. Based on a frame-type aluminosilicate zeolite (clinoptilolite) and layered aluminosilicate (bentonite) with a high content of montmorillonite, their Na-forms were obtained. The results of the physicochemical analysis of the natural material and its modified Na-form are presented. Sorption treatment of wastewater from some heavy metal ions on modified forms of bentonite and clinoptilolite was carried out. It has been established that, in terms of sorption properties, the obtained sorbents based on natural raw materials Na-clinoptilolite and Na-bentonite can be recommended instead of synthetic industrial KU-2-8 in the sorption extraction of heavy metal ions from wastewater.
Keywords: aluminosilicate, sorbent, heavy metal ions, sorption method.
doi.org/10.32737/0005-2531-2022-2-100-106 Introduction
At present, during the period of intensive work of almost all branches of production, including nuclear and thermal energy, industrial and rural construction, transport, etc. there is some negative impact on the ecological balance of the environment. Chemical, metalworking, oil, metallurgical and some other industries pollute the biosphere with gas emissions, solid waste and sewage. The chemical industry, today, one can say, occupies one of the leading positions among enterprises that cause environmental harm to the environment [1].
Thus, galvanic production, which is engaged in the application of protective or decorative coatings on metal and non-metal products (zinc plating, nickel plating, oxidation), can also be attributed to enterprises that pollute the envi-
ronment with wastewater [2]. It should be noted that at present, galvanic coatings are used in almost all industries: mechanical engineering, instrument making, production of printed circuit boards, etc. the amount of wastewater of complex composition. With an inferior degree of purification, they are one of the sources of pollution of aquatic environments. The main toxic component polluting this kind of wastewater are heavy metals: chromium (VI), cadmium, lead and other toxic substances [3]. Some electroplating enterprises use old and inefficient wastewater treatment processes, and sometimes they do not even have treatment facilities, which contributes to the ingress of untreated and undertreated wastewater into natural reservoirs and causes irreparable damage to the environment. Discharges of waste solutions by volume make up 0.2-0.5% of the total amount of
effluents from galvanic production, however, due to their high concentration, they contain up to 70% of discharged contaminants. Concentrated waste solutions, discharged without their neutralization, lead to a violation of the purification technology and the loss of valuable components, therefore, the introduction of closed water use systems is of great importance, with preliminary disinfection of harmful effluents. Acid wastewater after washing (pickling and pickling operations) contains a mixture of acids (hydrochloric, sulfuric, sometimes nitric and phosphoric acids), alkaline wastewater (pH - 911), including washing water after degreasing, washing, alkaline electroplating (zinc plating) and contain 50-150 mg/l of oils and petroleum products. Cyanic wastewater (pH = 8-11) after electroplating from cyanide baths (zinc plating, copper plating, cadmium plating, clarification) contains 50-100 mg/l of complex heavy metal cyanides, which, when mixed with acidic effluents, form hydrocyanic acid. Sorption treatment of wastewater from some heavy metal ions on modified forms of bentonite and clinoptilolite was carried out. It has been established that, in terms of sorption properties, the obtained sorbents based on natural raw materials Na-clinoptilolite and Na-bentonite can be recommended instead of synthetic industrial KU-2-8 in the sorption extraction of heavy metal ions from wastewater. It has been established that chromium-containing wastewater contains cadmium - 0.3-0.5 mg/l chromium (III) - 0.2-0.5 copper - 0.5-1.0 iron - 0.1-0.5 nickel -0.2-0.5 and zinc - 0.2-1.0, these indicators do not correspond to MPC according to GOST 9.314.90 and are subject to neutralization [5], because Currently, with the tightening of environmental legislation, more stringent standards are being established for the discharge of industrial effluents and penalties for exceeding the established MPCs are increasing.
Among the variety of existing methods currently at treatment facilities, the most common method for neutralizing galvanic waste-water is the reagent method, in particular, the precipitation of metals with calcium hydroxide, but it does not ensure that the content of heavy metal ions in wastewater reaches the modern MPCs [4]. Also, for more efficient precipitation
of the formed insoluble heavy metal complexes, solutions of flocculants [5] are used, however, after applying this technology, the effluent is suitable only for discharge into the sewer, with subsequent transfer of the effluent for post-treatment to municipal wastewater treatment plants. The main disadvantage of this method is the formation of a large amount of sludge containing toxic compounds of heavy metals, and the main way to neutralize these wastes is their burial corresponding to the 3rd hazard class [6].
Among the listed wastewater treatment methods, the main place belongs to the sorption method, which uses natural sorbents, such as activated carbons, zeolites, bentonite clays and other natural materials [7]. The significance of the use of these natural resources lies in the fact that they do not have such a high cost and are easily accessible.
Experimental part
The smectite group belongs to the family of clays that do not contain metals and consist mainly of hydrated sodium, and calcium. and aluminum silicate, in general, is a clay mineral with an expanding crystal lattice of 2:1 [8]. Its amorphous substitution gives different types of smectite and causes a net permanent charge balanced by cations so that water can move between the sheets of the crystal lattice, providing reversible cation exchange and very plastic properties. Membranes of the smectite group include decahedral minerals montmorillonite, beidellite, nontronite, bentonite and tetryocta-hedral minerals hectorite (lithium-rich), sapo-nite (magnesium-rich), and sauconite (zinc-rich). Zeolites belong to the class of aluminosil-icates and have a crystalline framework whose spatial lattice consists of SiO4 and AlO4 tetra-hedra associated with an oxygen atom resembling a truncated octahedron. This structure is characteristic of clinoptilolite and heulandite and contains micropores the size of molecular diameter, giving them the function of a molecular sieve. When heated, hydrated zeolites release water, leaving hollows with a large total amount of pores ready to absorb molecules of toxic substances[9].
Bentonite clays-syllabic mineral formations are also classified as aluminic clays, the main component of which is montmorillonite, and have an elementary structural layer type 2:1 (three-story layer) consisting of an octahedral ox-ygen-hydroxyl grid Al(O,OH)6, between two SiO4 tetrahedral nets. As a result of the amorphous substitution
of Mg2+ AI cations in octahedral and AI3+ Si4+ tetrahedral mesh, the negative charge of the aluminic layers is compensated by the exchange cations Na+ or Ca2+ in its interlayer space. The main rock-forming component of bentonite clays is predominantly montmorillonite (>60-70%), which is itself part of the smectite group [10]. As impurities are quartz, field spades, cal-cite, rarely pyrite and organic matter, as well as other clay minerals - kaolinite, illite, mixed clay
minerals, sometimes chlorite and vermicu-lite. Montmorillonite has a predominant charge localization in octahedral meshes leading to high sorption of toxic cations, and it is the features of the montmorillonite structure that determine specific properties such as binding and sorption capacity, heat-resistance and others (Figure 2).
Bentonite clays can thus be seen as a promising and widely used industrial raw material. In the submitted work, bentonite clay from the Dash Salahla deposit in the Gazakh district of our republic, one of the highest quality natural clays, was used as a sorbent in the process of sorption of toxic metal ions from wastewater sodium deposits in the world with high mont-morillonite content [11-12].
Fig. 1. Structure of natural zeolite.
Fig. 2. Montmorillonite structure. AZERBAIJAN CHEMICAL JOURNAL № 2 2022
Analysis of the mineral and raw material base of bentonite clays of Azerbaijan has established that the reserves of the deposits, their degree of development and the volumes of production are the most favorable object for our research, therefore the selection of this deposit was not accidental and is also based on the fact that that the bentonite clay of this deposit contains the largest quantity (75-80%) mont-morillonite [13-14].
When creating high-efficiency sorbents, it is necessary to conduct in-depth studies of the initial material and to further choose the optimal method of their modification [15-16]. When collecting the raw material, the sorbents excluded the defects of the crystal lattice, convex surfaces and concave surfaces, which usually result in irregularities in the packages of the layers and adversely affect the quality of the final product. The structure of the clay was studied under an electron microscope and mineralogical and elemental composition was determined. In addition to montmo-rillonite, the sample contains other minerals such as quartz, calcite, feldspar, and mica, which do not participate in chemical reactions (Tables 1 and 2). Table 3 presents the characteristics of the investigation of natural and modified sorbents The composition of natural and modified Na-forms has been investigated by various modern physico-chemical methods of analysis. (spectro-photometric, derivatives, X-ray phase, etc.). Spectrophotometry analysis of the samples was carried out on the spectrophotometer ALFHA (firm Bruker) in a range of wavelength numbers of 400-3000 cm-1. Thermographic analysis was carried out on Yupiter NETZS Ch STA 449F3AE derivatives with a heating rate of 10 0/s. The weight of the canopy was 0.7 g. Aluminium oxide was taken as the reference. The studies were carried out at a temperature range of 200-800°C. Roentgenographs investigations of said bentonite sorbents were carried out on a diffractometer of type "D2-Phaser" on CuK« radiation.
In the study of sorption properties of natural material, modified Na-forms of natural sorbents of clinoptilolite from the deposit of Ayu Dag and bentonite from the deposit of Dash Salahla of the Republic of Azerbaijan
were used in experiments. For comparison from industrial sorbents synthetic cation KU-2-8 (sterol copolymer and divinyl benzene) was used, modified by us in H+ and Na+-forms. For experimental studies, solutions with concentrations of heavy metal ions CO and Cd in the range
were used, which corresponded to concentrations of heavy metal ions in industrial liquid waste. The necessary ion forms of clinoptilolite and KU-2-8 were obtained dynamically by washing 0.1 N with NaCl and HCl solutions at room temperature (220C). Na bentonite was obtained under static conditions by mixing with 0.1N NaCI solution at room temperature for three days. Sorbent samples were airdried and stored in glass jars with caps attached. Complex titration and photocol-orimetric determination [17-18] were used to determine the concentration
of Co2+ and Cd2+
ions in solutions in the range 0.001-0.1N. Dynamic exchange capacitances (DOE) have been determined for the H-, Na-forms of the industrial sorbent: KU-2-8 (H), KU-2-8 (Na), and Na-clinoptilolite (g=5g). In this case, acetate and chloride solutions of cobalt and cadmium were used in a wide range of concentration changes at a rate of 1ml/min. For Co and Cd (1 • 10" -110-4). Full dynamic exchange capacity was calculated in mg-eq/g sorbent. The results of the tests are shown in Tables 4 and 5. In the experiments, the clinoptilolite dispersion fractions of 0.63-1.00 mm and bentonite of 0.3-0.5 mm were used.
Results and discussion
Tables 1 and 2 present the results of the chemical and mineralogical recovery of clay minerals of a number of bentonite deposits of Azerbaijan, Ag-Dere and Kyzyl-Dere (Khyzin district), Gyuzdek (Absheron district) and Dash-Salahla (Kazakh district). According to table data, the composition of the bentonite of the Dash Salahla deposit (Kazakh district) and its co-location with montmorillonite is significantly different from that of other clays, but the latter solves the content of montmorillonite (83.7%) [19].
Table 1. Results of chemical analyzes of bentonite clay samples, %
№ Name of fields Na2O MgO Al2Os SiO2 P2O5 SO3 K2O CaO TiO2 MnO Fe2Os
1 Ag-Dere 3.17 3.41 13.04 55.17 0.024 0.031 1.19 2.66 0.590 0.286 4.57
2 Quzdek Absheron 3.07 2.45 12.6 55.8 0.07 0.02 1.09 3.66 0.52 0.24 4.8
3 Das-Salahli Qazax 3.20 2.45 21.3 57.55 0.020 0.024 1.10 2.0 0.58 0.46 4.0
Table 2. Mineralogical composition of the presented samples of bentonite clays, %
№ Name of fields SiO2 (a-kvars) Feldspar Montmorrilonit CaCOs (calcit) Fe2O3 NaCl
1 Aq-Dere 6.2 10.3 74.6 4.2 4.5 0.4
3 Das-Salahli 5.7 30.4 83.7 6.3 4.3 0.3
4 Quzdek 16.8 28.6 46.2 2.7 4.9 0.6
Table 3. Physico-chemical characteristics of natural and modified sorbents
Aluminosilicate minerals Density, g/sm Porosity, p, % Humidity hygroscopic, W % Bulk density, V, q/sm
Natural bentonite clay 2.22 54.59 7.69 1.08
Modified Na-form 2.35 55.02 7.55 1.29
Table 4. The dynamic and static exchange capacity of modified sorbents during sorption of CO2+ ions mq-ekv/q
Sorbent name Exchange capacity Ion concentration,N
110-1 110-2 110-3 5 10-4 110-4
KU2-8 (H) Dynamic exchange capacity 5.3116 1.4918 0.1531 0.0644 0.01463
KU-2-8((Na) Dynamic exchange capacity 5.4922 1.6144 0.1942 0.0834 0.0365
Na-klinoptilolit Dynamic exchange capacity 0.8723 0.6931 0.1311 0.0483 0.0186
Na-bentonit Static exchange capacity 2.0815 1.0744 0.1962 0.0692 0.0296
Table 5. The dynamic and static exchange capacity of modified sorbents for sorption of Cd2+ mq-ekv/q ions
Sorbent name Exchange capacity Cd+2 ion concentration,N
110-1 110-2 110-3 5 10-4 110-4
KU2-8 (H) Dynamic exchange capacity 5.2418 1.4106 0.1409 0.0511 0.0198
KU-2-8((Na) Dynamic exchange capacity 5.3946 1.5339 0.1744 0.0667 0.0293
Na-klinoptilolit Dynamic exchange capacity 0.9050 0.7108 0.1291 0.0363 0.0171
Na-bentonit Static exchange capacity 1.6126 1.6126 0.1663 0.0547 0.0329
The tables (Table 4 and 5) show DOE
2+ 9+
values for Co and Cd in particular at low concentrations (5 10-4 N, 110-4N). Na-clinopti-lolite and Na-bentonite sorbents are close to DOE values for synthetic sorbents H+ and Na+-KU-2-8. These low concentrations correspond to the concentrations of used ions in wastewater. DOE is very important because sorption methods using solid sorbents are often used to concentrate, extract and separate valuable components (ions of a number of heavy, rare-earth, transuranic elements, etc.) from diluted production waste-water solutions from toxic ions of a number of heavy metals before being released into natural water bodies [20-21].
Conclusions
The rational feedstock was selected to produce efficient sorbents, taking into account that the wastewater of a number of metallurgical and galvanic industries is contaminated
2+
with the cations of heavy metals such as Cu , Zn2+, Ni2+, Cr3+, Co2+, Cd2+ and others. In the studies, it was found that isomorphic substitutions in octahedral and tetrahedral meshes form a negative charge on the surface of the sorbent, which is compensated by inter-layer cations and results in high sorption of toxic cations as a result of the fact that sodium bentonite clays obtained by cationic exchange reaction are alkaline sorbents and have, as compared to alkaline soil sorbents (calcium, magnesium),
higher technological properties and hydration potential. It is assumed that the change in the porosity of the monocation forms of bentonite sorbents is related to the hydrability of the exchangeable cations and the least free voids of the highly dispersed Na-Bentonite are associated with the lack of propensity for free hydrated sodium ions to hold in interaquatic space. The study of the physicochemical characteristics of aluminum-oxidizing rocks, once in personal deposits, has provided the preconditions for the establishment of the scientific basis for the preparation of effective ben sorts of materials used in the treatment of wastewater and jets of heavy metal ions and various toxics, which is very relevant for the protection of the water and air basin from pollution by substances. In this aspect of the work, the production and use of modified sorbents based on natural material to remove heavy metal ions from wastewater are relevant and of great scientific, practical and economic importance.
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MÜHiTiN AGIR METAL iONLARINDAN TOMÏZLONMOSÏNDO ALÜMOSiLiKAT GÎLLORINÎN
SORBENT KiMi ÏSTÎFADOSi
Z.R.Agayeva, S.S.Bayramova, H.i.Rafiyeva, Y.B.Qahramanova, E.M.Kazimova, X.N.ilyasova
istehsalat tullanti sularini zarazliçdirmasi maqsadi ila yerri alümosilikat tipli xammal asasinda effektiv sorbentlar alinmiçdir. Onlarin tabii va modifikasiya olunmuç formalarin fiziki-kimyavi xassallari ôyranilmiçdir. Sorbsiya üsulu ila sorbentlarin vasitasi ila tullanti sulardan agir metall ionlarinin kanarlaçdirilmasi apanlmiçdir. Müayyan olunmuçdur ki, tabii xammal asasinda Na-klinoptilolit va Na-bentonit alinmiç sorbentlar istehsalat tullanti sularindan agir metall ionlarinin zarazliçdirilmasinda sanayada istifada olunan KU-2-8 avazinda müvaffaqiyyatla istifada oluna bilar.
Açar sözlar: alümosilikat, sorbent, agir metall ionlari, sorbsiya üsülu.
ИСПОЛЬЗОВАНИЕ АЛЮМОСИЛИКАТНЫХ ГЛИН В КАЧЕСТВЕ СОРБЕНТОВ ПРИ ОЧИСТКЕ
СРЕД ОТ ИОНОВ ТЯЖЕЛЫХ МЕТАЛЛОВ
З.Р.Агаева, С.С.Байрамова, Х.И.Рафиева, Е.Б.Гахраманова, Э.М.Кязимова, Х.Н.Ильясова
Проведен поиск природного сырья для получения эффективных сорбентов при обеззараживании производственных стоков. Исследован химико-минерологический состав ряда месторождений алюмосиликатных пород Азербайджана. Анализ полученных результатов позволил установить оптимальный вариант синтеза сорбентов. На основание алюмосиликата каркасного типа цеолиты (клиноптилолит) и слоистого алюмосиликата (бентонит) с высоким содержанием монтмориллонита, были получены их Na-формы. Приведены результаты физико-химического анализа природного материала и его модифицированной Na-формы. Проведена сорбционная очистка сточных вод от некоторых ионов тяжелых металлов на модифицированных формах бентонита и клиноптилолита. Установлено, что по сорбционным свойствам полученные сорбенты на основе природного сырья Na-клиноптилолит и Na-бентонит могут быть рекомендованы взамен синтетического промышленного КУ-2-8 при сорбционном извлечении ионов тяжелых металлов из сточных вод.
Ключевые слова: алюмосиликат, сорбент, ионы тяжелых металлов, сорбционный метод.
