USE OF POROUS COMPOSITE MATERIAL IN DRIP IRRIGATION

ABSTRACT

The article is devoted to the study of the properties of porous composite materials obtained by modifying interpolymer complexes based on urea-formaldehyde resin and sodium carboxymethylcellulose with phosphogypsum and their use in agriculture and water management.

АННОТАЦИЯ

Статья посвящена изучению свойств пористых композиционных материалов, полученных модифицированием интерполимерных комплексов на основе карбамидоформальдегидной смолы и натрийкарбоксиметилцеллюлозы фосфогипсом и их использованию в сельском хозяйстве и управление водными ресурсами.

Keywords: urea-formaldehyde resin (UFR), sodium carboxymethylcellulose (CMC-Na), phosphogypsum (PG), interpolymer complex (IPC), porous composite material (PCM).

Ключевые слова: карбамидоформальдегидная смола (КФС), натрийкарбоксиметилцеллюлоза (КМЦ-Na), фосфогипс (ФГ), интерполимерный комплекс (ИПК), пористый композиционный материал (ПКМ).

Introduction. One way to improve the complex properties of composite materials (CM) is their modification by adding various additives. This, in turn, increases the strength, hardness, heat resistance, water resistance and a number of other important properties of the material. To improve the complex properties of porous composite materials (PCM), it is necessary to physically modify them by adding various fillers and aggregates. After modification, PCM increases strength, stiffness, heat resistance, water resistance and a number of other important properties. It was reported in the literature that the properties of interpolymer complexes (IPCs) can be controlled by changing the nature of the intermolecular bonds of the interacting components [1, 2]. Equivalent interactions of the starting materials lead to IPC, and an increase in the concentration of one of the polymers leads to nonstoichiometric interpolymer complexes (NICs). The use of phosphogypsum is an important problem not only in the Republic of Uzbekistan, but also in almost all countries of the world that produce mineral fertilizers. In Uzbekistan, the scale of the accumulated as a whole can be estimated at about 80 million tons. The natural raw material from which phosphogypsum is obtained contains almost the entire table of chemical elements of D.I. Mendeleev. Currently, the average level of useful use of this industrial waste is no more than 2.0%, although in previous years it reached about 2.5 million tons / year (over 10% of the current output).

Despite the fact that most enterprises are striving to create low-waste and waste-free technologies, in practice there are often several tons of gypsum-containing waste per 1 ton of useful products. For example, in the formation of phosphoric acid, 4-5 tons of phosphogypsum are obtained per 1 ton of acid [3,4,5,6,7,8].

The conducted monitoring studies[9,10] of the phosphogypsum dump, located on the territory of the Almalyk mineral fertilizer plant of Ammophos-Maxam JSC, showed that the stale phosphogypsum has an identical chemical and phase composition. Phosphogypsum chemical composition contains mainly oxides of calcium, sulfur and silicon with an admixture of oxides of iron, aluminum, magnesium, phosphorus, sodium and others (table 1).

As can be seen from Table 1, the mass fraction of the main substance (CaSO4∙2H2O) in terms of dry dihydrate is 97%, the mass fraction of hygroscopic moisture is 16.4%, the content of water-soluble fluoride compounds in terms of fluorine is 0.12%. Impurities of toxic compounds of cadmium, arsenic, mercury, lead in the composition of phosphogypsum were not found [11,12,13]

Table 1.

Results of chemical analysis of phosphogypsum samples Ammophos-Maxam OJSC [20]

According to the technical characteristics, the stale phosphogypsum, located on the dump of the mineral fertilizer plant of OAO Ammophos-Maxam, meets the requirements of TU113-08-418-94 "Phosphogypsum for agriculture" grade No. 2 and therefore can be used for chemical soil reclamation [14,15] .

For samples of stale phosphogypsum (waste of Ammophos-Maxam JSC), the specific effective activity of natural radionuclides was determined, on the basis of which a sanitary and epidemiological conclusion was given that the phosphogypsum samples correspond to SP No. 202 dated 03.02.2012. "Sanitary and epidemiological requirements for ensuring radiation safety" and phosphogypsum can be used without restrictions in economic activities.

Phosphogypsum is a large-tonnage secondary resource; if the requirements for storage facilities are fully observed, it is not dangerous for the environment. Phosphogypsum, a practically unused product, contains a number of valuable components: it is enriched with calcium oxide and rare earth elements - silicon, iron, titanium, magnesium, aluminum and manganese.

According to numerous data, phosphogypsum has advantages over natural gypsum in some areas of application: melioration of solonetzic soils, protection from radiation, recultivation of soils contaminated with oil products [16]. At a dose of phosphogypsum application of 5 t/ha, 100-130 kg of P2O5 in an assimilable form can enter the soil, which largely compensates for the costs of agriculture for its transportation and application. The most valuable macro- and microelements in huge quantities go to dumps. The ways of utilization of phosphogypsum available in world practice, for example, in agriculture, have not found wide application and use for economic, technological and environmental reasons. As a result, phosphogypsum lies in landfills, while in our country calcium is washed out of the soil every year, which must be replenished by liming and gypsuming. However, phosphogypsum is practically not used for these purposes. [17]

In agricultural production, phosphogypsum can be used for the following purposes: for reclamation of solonetzes (soil desalinization), mixed with lime for reclamation of acidic soils, as fertilizer ameliorants (1 ton of phosphogypsum contains 0.6–4.5% P2O5) [18] , for composting with biopreparations and organic fertilizers, for use as a sulfur or silicon fertilizer [14-16]. It has been established that the application of phosphogypsum at a dose of 2-4 c/ha can satisfy the needs of agricultural plants in this element [7]. The results of the experiments indicate an increase in the efficiency of liming and gypsuming with the combined application of these materials, which provide a weakly acidic reaction, an increased level of Ca, and an improvement in the provision of plants with sulfur [8]. On soils in which the content of mobile aluminum is minimal, but there are toxic amounts of Mn and Cu, it is advisable to use phosphogypsum to improve the Ca : Al, Ca : Cu and Ca : Mn ratios. In this case, phosphogypsum may also be more suitable for crops that need improved aluminum–iron–sulphur nutrition but react poorly to a shift in the soil reaction to the alkaline side, for example, for potatoes [19].

A distinctive feature of neutralized phosphogypsum is the low content (0.46%) of stable strontium. With such a content of this element, introduced into the soil with phosphogypsum, even at the maximum doses of the ameliorant (10–15 t/ha), the Ca : Sr ratio in the soil does not change significantly. This is a factor in the environmental safety of the use of the ameliorant, and hence the guarantee of the absence of toxicity of strontium [10].

Methodology and methods of study. To obtain a composite material, the following components were used: CMC-Na from the Namangan Chemical Plant, obtained by the method of heterogeneous solid-phase esterification of sulfite wood cellulose with monochloroacetic acid, GOST 5.588-79 with a degree of substitution (SZ) 70 and polymerization (SP) 400. Urea-formaldehyde resin (UFR). Industrial urea-formaldehyde resins of the KFZhS brand (urea-formaldehyde viable resin) were used, representing a 60-70% solution containing condensation products of urea and formaldehyde.

Phosphogypsum (FG) is a waste product of the Ammophos-Maxam phosphate fertilizer chemical plant (Almalyk, Uzbekistan).

Sand of the Syrdaryn quarry. The physical and mechanical properties of the sand used in the work are as follows: fineness modulus 0.2-0.25 mm; volumetric weight-1.42 g/cm3. By mixing the above ingredients in various ratios and under various conditions, porous composite materials (PCM) were obtained.

We created PCM by mixing IPC, filler and aggregate together and casting the samples into moulds. Because it helps them to study their physical and mechanical properties. The complex formation in this system and IPC was studied by the methods of potentiometric titration, viscometry and IR spectroscopy, microphotography.

To study the morphology of PCM, an electron microscope “EVO MA-10” by OXFORD Instruments was used, with a magnification of 100-10000 times.

In this case, first of all, they were interested in the micro- and macrostructure, the degree of porosity, the homogeneity of the microstructure, the elemental composition, etc. The samples were then viewed under a microscope and taken from both sides, which made it possible to understand the internal microstructure. Given the presence of large pores and large filler particles, the survey scale was chosen. The total increase of all shots is 55 times (fold), which made it possible to obtain panoramic shots. From each sample, 3-4 images of the most characteristic areas were taken.

Figure 1. Graph

Discussion. It should be noted that the maximum yield of IPC corresponds to the CFFA (for all CFB units): CMC-Na = 0.2:0.3. We used IPC with CFFA: CMC-Na = 0.3:0.2, which is an excess of CFFA. The lack of CMC-Na in the mixture leads to the polycondensation of the CPS, which is explained by the thickening of the mixture, the transition of the CPS to a three-dimensional state. This means that FSC polymers are part of the IPC and do not participate in other polycondensation reactions, allowing the formation of insoluble cross-linked polymers. Provides additional mechanical strength and control of PCM porosity by increasing water resistance. The physical and mechanical properties of the obtained PCM samples are given in Table.

Table 2.

Physical and mechanical properties of the obtained samples of porous composite materials

Results. Studies have shown that phosphogypsum was dried to a powder at 120° C. and that samples based on sand particles with a 075-1 mm sieve were effective. The amount of phosphogypsum without changing the ratio of the main components (starting from 15 parts by weight, but the mass of sand did not change) was determined from the results of many laboratory experiments in modified samples with a content of 20-25 sq.m. IM, consisting of phosphogypsum, has the best mechanical properties and is resistant to water and aggressive environments (salt solutions of various concentrations).

It follows that the use of phosphogypsum in PCM increases its strength, but reduces porosity, so phosphogypsum must be dried at a temperature above 1200C, crushed (through a sieve) and applied in a prescribed amount. This, in turn, not only ensures the strength of the material, but also makes it possible to obtain the expected PCM porosity.

Conclusion. In conclusion, PCM (IPK - phosphogypsum and sand) based on CFGS - CMC showed that the components are distributed evenly and have a fairly homogeneous structure. The simultaneous formation of two complexes and the processes of CPS polycondensation form a complex structure in which the properties of IPC and PCM not only complement, but also reinforce each other. This will significantly improve the physical and mechanical properties of PCM, which, in turn, will allow the use of a wide range of applications for irrigation of such PCM.

For stale phosphogypsum samples, the specific effective activity of natural radionuclides was determined, on the basis of which it was concluded that the specific activity of the phosphogypsum sample does not exceed the standard values ​​(SanPin No. 0134-03. “Sanitary and epidemiological requirements for ensuring radiation safety”) and can be used without restrictions in economic activity.

• technogenic wastes of phosphogypsum due to large deposits (several million tons), accessibility, easy opening and the availability of the necessary infrastructure at existing plants are a promising raw material source of calcium, phosphorus and other elements.
• by processing phosphogypsum, it is possible to obtain PCM-locs, which are needed by agricultural fields irrigated in saline areas of Uzbekistan in several thousand hectares. Based on this, a more specific task is set on the basis of a large-tonnage waste from the production of phosphogypsum, namely, to use it as a raw material for production in the national economy. It has been established that the developed interpolymer materials with an excess of carboxymethylcellulose sodium salt can be used as highly swelling hydrogels and impervious screen, and with an excess of urea-formaldehyde resin and dispersed fillers - to save irrigation water (uniform distribution of water along the length of the irrigation furrow). The fact of their role in water saving and cotton productivity has been confirmed.

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