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71CHEMICAL SCIENCES
ОЧИСТКА ВОДЫ ОТ ТЯЖЕЛЫХ МЕТАЛЛОВ ИОНИТАМИ
Бектенов Н.А.
д.х.н., профессор Казахский национальный педагогический университет им. Абая, г. Алматы Цой И.Г. к.х.н., доцент Таразский государственный университет имени М.Х. Дулати, г. Тараз.
Камбарова Э.А. магистр химии Таразский государственный университет имени М.Х. Дулати, г. Тараз.
Ыбыраимжанова Л.К. магистр химии Таразский государственный университет имени М.Х. Дулати, г. Тараз.
WATER PURIFICATION FROM HEAVY METALS WITH IONITES
Bektenov N.,
Doctor of chemical sciences, professor Kazakh National Pedagogical University. Abay, Almaty
Tsoy I.,
Candidate of Chemical Sciences, associated professor Taraz State University named after M.Kh. Dulati, Taraz.
Kambarova E., Master's degree in Chemistry Taraz State University named after M.Kh. Dulati, Taraz
Ybyrayymzhanova L. Master's degree in Chemistry Taraz State University named after M.Kh. Dulati, Taraz.
Аннотация
В статье рассматривается различные методы очистки тяжелых металлов ионитами, так как проблема загрязнения водной среды металлами очень распространено. Эффективным сорбентом для ионов тяжелых металлов являются синтетические ионообменные материалы. Для более эффективной очистки используются в последнее время модифицированные иониты.
Abstract
The article discusses various methods for water purification from heavy metals with ion exchangers, as the problem of pollution of the aquatic environment with metals is very common. Synthetic ion-exchange materials are an effective sorbent for heavy metal ions. For more efficient cleaning modified ion exchangers are being used currently.
Ключевые слова: ионообменные материалы, модифицированные иониты, катиониты, аниониты, тяжелые металлы, сорбент.
Keywords: ion exchange materials, modified ion exchangers, cation exchangers, anion exchangers, heavy metals, sorbent
The heavy metals include more than 40 metals of the periodic system with an atomic mass of over 50 atomic units: V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Cd, Sn, Hg, Pb, Bi, etc. The following conditions play an important role in categorizing heavy metals: their high toxicity to living organisms in relatively low concentrations, as well as the ability to bioaccumulate and bio-magnify. According to N. Reimer's classification, metals with a density of more than 8 g / cm3 should be considered heavy. Thus, heavy metals include Pb, Cu, Zn, Ni, Cd, Co, Sb, Sn, Bi, Hg [1].
The severity of aquatic pollution problem with toxic metals is determined by:
- high concentration of heavy metal compounds in the coastal areas of the ocean and inland seas;
- the formation of highly toxic organometallic complexes, which are included in the abiotic component of the ecosystem as well as absorbed by hydrobi-onts;
- the accumulation of metals by hydrobionts in doses that are dangerous to humans.
According to toxicological assessments of stress indexes, heavy metals occupy the second place among pollutants after pesticides [2].
Up to 200 kilotons of lead and 5 kilotons of mercury get up to the World Ocean every year. Currently the contribution of atmospheric deposition of lead to its total flow into the oceans already exceeds the geochem-ical contribution of this element with river flows. The entry of cadmium into the ocean due to precipitation and as a result of direct runoff from land is close, while for mercury the atmospheric flow is about 25% of the total input into the ocean environment. It is now recognized that the main source of heavy metals in the environment is not metallurgical production, but coal combustion. The annual combustion of 2.4 billion tons of coal and 0.9 billion tons of lignite disperses 200 kilotons of arsenic and 224 kilotons of uranium in the environment, while the world production of these metals is only 40 and 30 kilotons, respectively [3].
Currently, the pollution of reservoirs and the quality of drinking water in the Republic of Kazakhstan is one of the most acute environmental problems. The problem of water is particularly acute in the Kyzylorda region. In particular, these are the problems of the Aral Sea and the strong pollution of the Syr Darya River from anthropogenic impact. The Republic of Kazakhstan is one of the largest producers of non-ferrous and heavy metals in the world.
An effective sorbent for heavy metal ions are synthetic ion exchange materials (ion exchangers). Ion exchange is a specific case of sorption of charged particles (ions), when the absorption of one ion is accompanied by the release of another ion into the solution, which is part of the sorbent. In this case, the ion, whose presence in the water is undesirable, is fixed on the sorbent. Thus, there is a "replacement" of some ions (let's call them "harmful") to others (let's call them "harmless").
Sorbents that work by this mechanism are called ion exchange materials or ion exchangers. Ionites are able to extract some dissolved salts from water, replacing them with other salts (for example, calcium and magnesium ions can be replaced with sodium ions) [4].
Most often, during the water treatment process, ion exchange is used to remove heavy metal (for example, lead) cations from water that pose a risk to human health, as well as to get rid of nitrates. Another application of ion exchangers is the softening of hard water, that is, the removal of excess content of calcium and magnesium ions from water. An essential characteristic of ion exchange resins is their exchange capacity, that is, the ability to "replace" a certain amount of "harmful" ions.
One of the main properties of ion exchange resins is their ability to regenerate after the "resource" has been exhausted. They are characterized by high exchange capacities [5-6].
New ion-exchange materials of foreign manufacturers for complex treatment of waste and natural waters have appeared on the Ukrainian market, the disadvantage of which is the high cost despite all their positive properties, At the same time, the Ukrainian enterprise State enterprise «Смолы» constantly works to create new brands of effective sorbents for
wastewater treatment from HMs and water treatment, which are not inferior in their properties to foreign analogues [7-8]. A technology and industrial production of weakly basic AHC, AMH-2 anion exchangers (technological analogs of AH-31) has been developed, which besides the ability to extract strong acid anions, effectively absorb organic impurities. New various anion exchangers are produced at the enterprises. Employees of the Kiev National University (KNUBA) proposed a comprehensive technology for purifying acidic (pH 3-4) washing wastewater from electroplating plants that meets all requirements, as well as instrumentation of this technology [9].
The effectiveness of anion exchangers Lewatit MP62 and AM-2b and ampholite VP-14K in the conversion of sodium tungstate to ammonium tungstate is compared. It was found that the Lewatit MP62 anion exchange resin is close to Bn-14K ampholyte in terms of tungsten capacity and ~ 1.5 times larger than AM-2b anion exchange resin. It has been shown that desorption of tungsten from Lewatit MP62 anion exchangers and AM-2b with ammonia solution at room temperature is not complete. Increasing the temperature to 52-54 ° C allows to improve the results of desorption of tungsten from both anion exchangers noticeably. This significantly increases the completeness of desorption of tungsten, reduces the amount of eluent that must be passed through anion exchange resin, increases the concentration of tungsten in desorbates. Experiments were carried out under dynamic conditions with the use of Lewatit MP62 anion exchanger for processing sodium tungstate solution obtained as a result of autoclave-soda leaching of tungsten from scheelite concentrate from one of the processing plants. Tungsten was desorbed with a 14% NH4OH solution at 54 ° C. It was shown that during the sorption of tungsten from industrial solution, the MP62 anion exchanger has a tungsten capacity which is not less high than for model solutions (> 300 mg WO3 / ml anion exchange resin). In addition, it was confirmed that hot ammonia solutions desorb tungsten from MP62 anion exchange resin sufficiently. The concentration of WO3 in commercial desorbate was 78 g / l [10].
In Bekturov Institute of Chemical Sciences new ion-exchange polymers and inorganic sorbents based on synthetic and natural raw materials have been created. Sorption and membrane technologies have been developed for the separation, concentration, and sorption of ions of various metals on their basis,
The use of epoxy compounds, quinones and glyc-idyl methacrylate (GMA) as initial reagents made it possible to synthesize ion exchange materials with high sorption and kinetic characteristics. The practical application of synthesized new sorbents will contribute to the development of import substitution.
Sorption technology in our Republic. The use of synthesized membranes that are not inferior, and in some cases exceed those of well-known foreign analogues, will reduce electricity consumption and eliminate the problem of water supply in arid regions.
A method has been developed for the synthesis of S, N-containing redox polymers by condensation of
polyethyleneimine with naphthoquinone in the presence of elemental sulfur. It was shown that with the introduction of elemental sulfur, the redox capacity of the redox polymer increases as well as the sorption characteristics with respect to heavy metal ions.
Anion exchanger based on glycidyl derivative of benzylamine, allyl glycidyl ether and polyethylene amine was synthesized, having a static capacity 4.8 mg-eq / g with respect to 0.1N HCl When the concentration of metals in the solution is 1.96-2.14 g / l, the selectivity of the anion exchanger based on the glycidyl derivative of benzylamine (GBA), allyl glycidyl ether (AGE) and polyethyleneimine (PEI) decreases in the series Cu2+> Zn2+> Ni2+> Cd2+> Pb2+> Co2+. SC anion exchangers in these conditions for ions of copper, zinc, nickel, cadmium, and lead are 434.0; 248.4; 170.4; 168.4 and 124.4 mg / g.
The scientific basis for the creation of new selective ion exchangers by chemical modification of GMA copolymers with polyamines (polyethylene polyamine (PEPA), PEI) and inorganic acids (H3PO4) has been developed. The sorption capacities of polyelectrolytes based on GMA copolymers, styrene (St), acrylonitrile (ACN) with aliphatic polyamines with respect to Cr3 + and Cr6 + ions were studied. The sorption properties of the phosphoric acid cation exchanger with respect to the ions Cu2 + ,Zn2 +, Cd2 + vs the concentrations, pH of the solution and the contact time of the solutions were studied.
Double and ternary copolymers of GMA-MMA (methyl methacrylate) -AKH, GMA-St-MMA and GMA-AKN were synthesized by radical polymerization in solution. For chemical modification, crosslinked insoluble ion exchangers based on GMA copolymers and complexones of nitrilo-trimethylphosphonic acids were obtained for the first time. The proposed method of synthesis provides complexing ion exchangers based on copolymers of epoxy acrylates and complexones with improved physicochemical characteristics, and, moreover, the implementation of this method of obtaining cation exchangers using available reagents that do not require special equipment.
Anion exchangers based on tetraglycidyl esters of aromatic amines, FFA and polyamines were synthesized. The basic physicochemical properties and the sorption capacity of the obtained ion exchangers with respect to copper ions were studied. It was found that they have sufficient sorption and kinetic properties and can be used to extract copper ions from technological solutions of hydrometallurgical production. The process of sorption of chromium (VI) and vanadium (V) ions by a new nitrogen-containing ion exchanger synthesized by condensation of GBA, AGE and PEI was studied. Under static conditions, its exchange capacity for chromium and vanadium (V) ions reaches 343.2 and 585.6 mg / g, respectively. It has been established that in its sorption and kinetic properties with respect to chromium (VI) and vanadium (V) ions a new ion exchanger surpasses all known industrial anion exchangers.
New anion exchanger obtained based on GBA, FGE and PEI has selectivity with respect to Cu2 + ions in the presence of Co2 + cations. In this regard, it is
promising to use synthesized anion exchanger for sorption of Cu2 + ions in the presence of Co2+cations in hy-drometallurgical processes and analytical chemistry.
Non-ferrous metallurgy is one of the largest consumers of water. Fresh water is consumed by non-ferrous metallurgy enterprises for the preparation of slurries and solutions, washing various sludges, cooling chemical equipment and for other purposes. At the same time, the large part of water is polluted by toxic substances: heavy metals and their compounds and is discharged back into the water bodies, causing irreparable harm to the environment. In addition, many valuable components are lost with waste waters - copper, nickel and other non-ferrous and rare metals. Ion exchange and sorption are the most effective methods for extracting heavy metal ions from wastewater, the advantages of which are the ability to remove contamination to almost any residual concentration, the absence of secondary contamination and process controllability. Compared with chemical reagent cleaning methods, sorption methods are more environmentally and energetically beneficial. The main requirements of sorption processes are sorbents with sufficient selectivity, high sorption capacity and resistance to high temperatures.
Based on aniline (A) or benzyl amine (BA) and epichlorohydrin (ECH), epoxy amines were synthesized, by condensing them with PEI or PEP polyfunc-tional anion exchangers A-ECG-PEPA, A-ECG-PEI and BA-ECG-PEI with a static capacity ( SOY) at 0.1 n solution of HCl 3.03; 4.83 and 8.95 mg-eq / g, respectively, as well as an anion exchanger based on tetraglycidyl ether 4,4'-diaminodifinylmethane, PEPA AGE, Ional A-16 based on diglycidyl ether rizortin (DGER), monoethanolamine vinyl ether (WEMEA) , allilbromide (AB), hexamethylenediamine and Ional A-17 on the basis of DGER, WEMEA, AB and PEI have been obtained.
The composition and chemical structure of the anions obtained were investigated by means of IR spec-troscopy and elemental analysis on a CHN628 analyzer (LECO, USA). The surface structure of anion exchangers was examined by electron microscopy on a JSM 6510LA scanning microscope (JEOL, Japan) with a resolution of 30A * cm -1. It is shown that anion exchangers have a developed system of macropores, whose sizes are in the range of 0.698-1.764 microns, and individual pores reach 2.585 microns. Therefore, the increased sorption capacity of anion exchangers is obviously due to the greater porosity. Consequently, the increased sorption capacity of anion exchangers is obviously due to the greater porosity.
The sorption capacity of an ion exchanger based on GBA, AGE, and PEI was studied. When the concentration in the initial solution of rhenium ions is 1.1 g / l, the exchange capacity is 209.2 mg / g, which corresponds to a 46% recovery rate. At a metal concentration of 0.1 g / l, the exchange capacity is 33.2 mg / g, and the degree of extraction is 80%.
Sorption of perrhenate ion by exchangers based on GBA, AGE, PEI was studied in the pH range from 1.2 to 8.4. At pH 2.9 anion exchange resin has a maximum absorption capacity. The recovery rate is 67%. Appar-
ently, at given pH values of the solution, the dissociation of the functional groups of the anion exchanger improves. A change of the medium pH from 3.6 to 8.4 practically does not affect the sorption activity of the ion exchanger. The time to reach an equilibrium between anion exchangers based on GBA, AGE, and PEI and a solution of NH4ReO4 containing 1 g / l of rhenium ions and having a pH of 2.9 is 3 hours. It was revealed that the maximum sorption capacity (SC) for A-16 and Ional-17 with respect to platinum (IV) ions from solutions in which their concentration is equal to 1.464 g / l is 234.4 263.6 mg / g, respectively. Anionite Ional A-17 is more selective for platinum (IV) ions than Ional A-16.
The sorption characteristics of Ional A-16 and Ional A-17 with respect to Pd (II) ions, depending on the extraction conditions (concentration and pH of solutions, duration of contact) were studied. It is shown that palladium ions are absorbed by the anion exchangers Ional A-16 and Ional A-17 from the chloride solutions much better than the platinum cations. The maximum absorption of Pd (II) anion exchangers Ional A-16 is observed at pH 2.0, and for Ional A-17 it is observed at pH 3.0. This is apparently due to the varying degree of protonization of the amino groups of anion exchangers.
The maximum SC values of the synthesized sorbents with respect to palladium (II) ions for Ional A-16 is 356 mg / g (3.35 mmol / g) and for Ional A-17 is 402 mg / g (3.78 mmol), respectively. Consequently, the polyfunctional anion exchangers Ional A-16 and Ional A-17 are able to extract palladium (II) chlorocom-plexes and are promising for its selective extraction and concentration.
Thus, new polyfunctional anion exchangers Ional A-16 and Ional A-17, can be used to extract Pt (IV) and Pt (II) ions from chloride solutions due to their high sorption properties with respect to ions of platinum metals, [11].
I.F. Samborsky and his co-workers received ion exchanger by condensation of epichlorohydrin and pol-yethylene-polyamines in an aqueous medium, when 2-mercaptobenzthiazole is added to the monomer mixture, which has complexing properties and provides high complexation of several elements (mercury, nickel, arsenic, etc.). The synthesized ionite can be used in hydrometallurgy, for wastewater treatment, and in other areas of ion exchange technology. Ionites based on the interaction products of thiocarbamide, epichlo-rohydrin and polyethylene polyamine have relatively better sorption properties with respect to divalent ions Cu2^ Ni2+, Co2+ than similar ionites of epichlorohydrin series [12].
At present, worldwide, including Russia, the ion exchange method is intensively used for water purification, which allows the use of a wide range of ion exchange materials, such as natural bentonite clays. There are several large bentonite deposits in Russia: the East European Platform, the Urals, the West Siberian Platform, and the Far East. As a rule, the depth of bentonite clay is rather small and does not exceed 20 m [13]. This makes it possible to mine them in an open way, due to
which they are characterized by low cost. In the composition of bentonite, the dominant mineral is montmo-rillonite, which has pronounced sorption and ion-exchange properties. Montmorillonite contains metal cations, which act as exchange cations. The most common exchange cation in bentonites is Ca2+■Bentonites carrying Na+, K+ and H+ as exchange cations have a significantly higher activity. Sorption-ion exchange materials based on bentonite clays by applying basalt fibers to the surface are known. Such complexes can be used to purify water containing heavy metals. Therefore, it is of interest to select other materials that can serve as a skeleton when applying bentonite clays. The ion-exchange properties of new geosynthetic sorbents based on basalt fibers and natural mineral sorbents of bentonite clays were studied with the aim of extracting heavy metal ions from water, using lead as an example. A fundamentally new way of using bentonite clays in the filter element has been developed [14].
Currently, special attention is paid to the creation and study of hybrid organic-inorganic materials intended for ion-exchange materials [15-16]. The combination of substances of different nature provides nano-composites with both granulated ion exchangers and membranes based on them - a complex of certain functional properties: high exchange capacity, selectivity to certain ions, thermal stability, significant proton conductivity and elasticity [17-18]. Another advantage of organic-inorganic materials, unlike polymeric materials, is their low propensity to accumulate organic substances and microorganisms that are usually found in solutions [19-20]. Composites based on cation exchange resins have already found application in catalytic and electrocatalytic processes, in particular for the deoxygenation of water and liquid hydrocarbons [21].
Based on the above materials, despite the undeniable success and the increasing amount of work on obtaining ion-exchange materials and various modifications of ion exchangers, the development of effective sorbents based on available raw materials with improved sorption and physico-chemical characteristics for the extraction of various metals remains an urgent task.
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