SYNTHESIS OF A HIGHLY SWELLABLE OLEOGEL BASED ON STYRENE-BUTADIENE RUBBER

ABSTRACT

This research provides information on the synthesis of oleogels based on butadiene-styrene rubber and maleic anhydride for the purification of water reservoirs from oil and oil products contamination. The physicochemical properties of the obtained oleogels were also studied. The effect of the ratio of initial materials used in the synthesis process on the breaking properties of the oleogel was studied. It was found that the addition of more than 0.5% of a gelling agent to the BSK-based oleogel composition resulted in a decrease in oil absorption. The properties of the obtained oleogels were investigated using IR (infrared) spectroscopy.

АННОТАЦИЯ

В данной работе представлена ​​информация о синтезе олеогелей на основе бутадиен-стирольного каучука и малеинового ангидрида для очистки водоемов от загрязнений нефтью и нефтепродуктами. Также были изучены физико-химические свойства полученных олеогелей. Изучено влияние соотношения исходных материалов, используемых в процессе синтеза, на разрушающие свойства олеогеля. Установлено, что добавление более 0,5% гелеобразователя в состав олеогеля на основе БСК приводит к снижению нефтепоглощения. Свойства полученных олеогелей исследованы с помощью ИК-спектроскопии.

Keywords: Oil, toluene, carbontetrachloride, rubber, butadiene-styrenerubber, maleicanhydride.

Ключевые слова: Нефть, толуол, четыреххлористый углерод, каучук, бутадиен-стирольный каучук, малеиновый ангидрид.

Introduction:

Pollution of drinking and industrial waters remains the most pressing environmental problem in areas where oil is extracted, transported, and refined. The collection of spilled oil and oil products in water resources is one of the pressing issues of today. As a result of environmental protection and the formation of a sustainable environment, various cheap, non-toxic, and biodegradable materials, from micro to nanomaterials, membranes, oleogels/aerogels, and other types have emerged for the development and restoration of various biomaterials [1,p. 262]. One of the most urgent issues today is the cleanup of water resources contaminated with spilled oil and oil products. The oil spilled into the water can quickly spread by wind and current, and the spread oil either evaporates, disperses in the water, or settles and accumulates in sediments. Additionally, temperature also increases the rate at which oil spreads.

When oil reaches the surface, its composition and properties change almost immediately. After the initial spillage of oil, several processes occur, such as volatilization, oxidation, emulsification, sedimentation, biodegradation, and dispersion.

Environmental pollution by oil substances can be divided into four groups depending on the location: atmospheric pollution due to the volatilization of volatile components of oil products, soil pollution, water system pollution, and environmental pollution caused by the spillage of oil products on the ground.

It is very important to select appropriate and effective methods for removing organic substances for each of these groups. Solvents used for the removal of volatile organic compounds are primarily focused on monitoring, and a variety of mechanical, biological, chemical, and adsorption methods are applied.

The most used methods for cleaning water bodies from spilled oil and volatile organic compounds are shown in Figure 1. [2, p.527].

Figure 1. Methods of oil and oil product purification

Mineral adsorbents form a very large group and are widely used due to their non-combustibility, chemical inertness, relatively low cost, convenience, and a range of other advantages. Typically, the adsorption of mineral sorbents towards petroleum derivatives is in the range of 0.20–0.50 g/g, and their bulk density is around 0.45–0.90 kg/dm³ [3, p.772].

Mechanical methods are more expensive solutions because they often require the use of specialized equipment. However, they are considered much less harmful to the environment compared to chemical methods. These include the use of booms, skimmers, floating dams, and barriers to limit the spread of oil and to mechanically collect it from the water surface [4, p.79]. Mechanical methods are effective only in calm water and calm seas, with little wind. The design of skimmers' construction has a significant impact on their efficiency [5, p.7914].

Hardening agents are typically dry, granular, hydrophobic organic polymers that react with oil to form a monolithic solid that floats on water. The resulting solid can be easily removed from the water surface. The effectiveness of hardening depends on environmental temperature, the type of oil, and its chemical composition [6, p.144].

Biological methods are typically used in the final stages of water treatment or when the level of pollution in the water exceeds an acceptable threshold. Biological methods are also applied to soils contaminated with petroleum products. For this purpose, strains of local microorganisms are cultured, as they are considered the most effective in the degradation of hydrocarbons, especially in local conditions [7, p.3690].

In cleaning spilled oil, oil-absorbing materials can be classified into three main categories: inorganic mineral products, synthetic organic products, and organic plant products [8, p.831]

Mineral products include materials such as zeolites, silica, perlite, graphite, vermiculites, bentonite clay, and diatomite [9, p.127].

Materials and methods

Experimental part: Synthesis of oleo gels based on butadiene-styrene rubber. Butadiene-styrene rubber is a group of products obtained by the copolymerization of 1,3-butadiene and styrene or methyl styrene, synthesized through a free radical mechanism in an emulsion. Approximately 30% of the styrene units are isolated, and about 40% are paired. 80% of the butadiene units in the polymer chain are in the 1,4 configurations, mostly in the transform (approximately 70%), while about 20% are in the 1,2 configurations. Various types of styrene-butadiene rubbers are styrene-butadiene-α-methyl styrene rubbers (SBMS), which differ in structure and properties.

Maleic anhydride (2,5-furandione) is an organic compound with the formula C₄H₂O₃. In its pure form, it is a colorless or white solid. Its melting point is 52.8°C, and its boiling point is 202°C.

Maleic anhydride easily hydrolyzes to maleic acid or isomerizes to fumaric acid in the presence of thiocarbamide or other catalysts. Methods for obtaining maleic anhydride include: 1) vapor-phase catalysis, where benzene is oxidized with air over a stationary vanadium-molybdenum oxide catalyst (accounting for approximately 50% of global production in 1987); 2) vapor-phase oxidation of n-butane over a stationary or fluidized bed vanadium-phosphorus oxide catalyst (accounting for approximately 40% of production).

Synthesis of oleo gels based on butadiene-styrene rubber.
For the synthesis, SKS-30-ARKM-15 grade butadiene-styrene rubber (BSR) was used. To carry out the crosslinking reaction of the rubber, the rubber was first dissolved in its solvent and converted from an elastic state to a liquid solution. Solvents such as toluene, gasoline, xylene, and carbon tetrachloride were used to dissolve the butadiene-styrene rubber. In the rubber dissolution process, 4 g of BSR was added to 46 ml of toluene.

The BSR was left at room temperature with the solvent until a light-yellow solution was formed in toluene. To carry out the reaction process for obtaining the oleo gel based on BSR in toluene, a maleic anhydride solution in toluene and an initiator were used as binders. The reaction process was carried out at 60-70°C. The resulting product was first left at room temperature and then dried in a drying oven at 40°C.

The prepared oleo gels were soaked in toluene, xylene, and benzene. The oleo gel product showed absorption rates of up to 85% for toluene, 80% for xylene, and 70% for benzene.

Results and discussion

Analysis of the obtained results: Oil product absorption capacity. The oleo gels are weighed and immersed in the oil product. Typically, within 6 hours, the sorption process results in the oleo gels absorbing non-polar organic compounds. After the absorption process is complete, the oleo gels are removed and naturally hung for 30 seconds to separate excess oil product. The mass of the oleo gels is then immediately weighed and determined. The oil holding capacity of oleo gels was determined by a modification of the Manzocco method [12]. Approximately 0.1 g of oleo gels were placed in 10 ml centrifuge tubes and then centrifuged at 13,000 rpm for 30 min.

Infrared spectra of the samples were recorded on an IRA ffinity-1SIR-Furespectrometer (Shimadzu, Japan) in the range of 600–4000 cm–1 at room temperature.

Figure 2 a/b. IR spectra of BSK (a) and oleo gel (b) based on BSK with MA

Figure 2a shows the IR spectra of BSK rubber and the oleo gel obtained from BSK and maleic anhydride samples. In the IR spectra of BSK, peaks corresponding to the characteristic peak of the –CH– groups of benzene and the –CH– flat deformation absorption region appear in the region of 2980.02 and 2951.09 cm-1, respectively, and represent the structure of BSK (Figure 2a).

At the same time, the intensity of the peak at 966 cm-1 increased in the oleo gel compared to the original BSK, which indicates an increase in the interactions of covalent bonds formed as a result of the reactions of unsaturated bonding of BSK with MA.

Figure 3a shows a 100x magnified image of the pores of the synthesized oleo gel with a new composition. Figure 3b shows a 250x magnified image of the oleo gel, revealing a close-up view of the arrangement of its macromolecules.

Figure 3. Scanning electron microscope images of the synthesized oleo gel with a new composition at a) 100, b) 250 times magnification

These oleo gels based on maleic anhydride and rubber are distinguished from other oleo gels by their toxicological harmlessness, high level of oil and grease absorption and kinetics. They are chemically very stable and do not easily react with other organic substances in an oily environment and are not destroyed. For example, the mass fractions obtained from the elemental analysis of the obtained oleo gels are presented in the table below, and we can see that 98.74% of the mass fraction is C and O elements.

This ratio of elements and the low number of additional element species play an important role in determining its physical and chemical stability, as well as its toxic properties.

The absorption properties of sorbents for aqueous media are shown in Figure 4. Two types of petroleum products (diesel and crude oil) were used as representatives of petroleum products. The ability of BSK-based oleo gel to absorb petroleum products in the oil-water system can be seen. The presence of styrene in the BSK-based oleo gel created an increased surface area for the sorbent materials, resulting in increased oil absorption in molecules with such a structure. Oil absorption also depends on the concentration of the sorbent. In this case, the amount of sorbent was 0.5%. At the same time, the addition of more than 0.5% of the sorbent to the BSK-based oleo gel reduces the absorption capacity of oil, since oil products lead to a dense formation of the sorbent matrix and reduce the absorption of oil products. The amount of product absorbed in 60 minutes of the sorption process is reflected in the results in Figure 4.

Figure 4. The ability of oleo gel to absorb petroleum products in a water-oil system

The oil absorption capacity depends on the density and viscosity of the oil. Oil (or diesel) with low viscosity spreads easily on the surface and immediately penetrates into the interior of the sorbent, while oil with high viscosity (crude oil) remains on the surface of the sorbent and slows down the penetration into the interior of the oleo gel. The viscosity of petroleum products is temperature-dependent, and temperature is a major factor affecting the oil absorption capacity of sorbent materials, as it changes the viscosity of the oil. Typically, the viscosity of a material decreases with increasing temperature. This may explain the decrease in the oil absorption capacity of BSK sorbents at temperatures above 45 °C. At higher temperatures, the oil retention in the pores of the rubber decreased due to the shortening of the rubber molecular chains.

Conclusion

Methods for synthesizing new oil and oil product-absorbing oleo gels were studied because of the interaction of rubbers with maleic anhydride, and their composition and structure were determined using modern physicochemical methods. The properties of oleo gels obtained based on rubbers as sorbents for absorbing oil products were studied. It was found that the ability to absorb oil products depends on various factors, such as the structure and composition of the synthesized oleo gels, the type of oil, and the properties of the oil.

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