Relevance. Environmental pollution due to the constant growth of the use of oil and oil products is one of the most large-scale and dangerous types of anthropogenic activity. Potential sources of pollution are facilities engaged in the extraction, processing, use, storage and transportation of oil and oil products, as well as wastewater and stormwater contaminated by them [5]. The greatest environmental damage is caused to the environment as a result of accidental oil spills, which can disrupt the ecological balance and stable operation of biological systems and technological facilities. Oil pollution of the hydrosphere is especially dangerous, since there is a high probability of the spill spreading to large areas. By entering natural waters, oil creates a film on the surface, complicating gas exchange and biological self-purification processes. In particular, the processes of dissolution and release of oxygen, carbon dioxide, heat exchange change, and the reflectivity of the water surface changes [18, 28, 29].
In the aquatic environment, oil products spread over the water surface, undergoing chemical and physical changes: assimilation by aquatic organisms, sedimentation, emulsification, formation of oil aggregates, oxidation, dissolution and evaporation [5]. The method and intensity of transformational changes of oil products in water bodies depend on the routes of their entry and the characteristics of hydrochemical and hydrometeorological conditions [5, 40].
Sorption treatment is one of the effective methods used to remove oil pollutants. Materials used to collect oil and oil products from the water surface are commonly called oil sorbents. They absorb and separate oil and oil products from water by adsorption or absorption. The quality of sorbents is determined mainly by their capacity in relation to oil, the degree of hydrophobicity, buoyancy after sorption of oil or petroleum products, the possibility of desorption, regeneration or utilization of the sorbent [5]. The range of sorption materials is quite wide. Currently, among all types of sorbents, organic and organo-mineral sorbents have become more widely used. In addition to activated carbon, zeolites and natural clays, wood chips and sawdust, modified peat, wool, waste paper, flax production waste, etc. are most often used. Promising sorbents are based on plant and animal raw materials. As materials for the production of such sorbents, buckwheat, sunflower, oat, rice, walnut shells, corn waste, fallen leaves, straw, waste from leather and fur production, chitin, chitosan [30, 34]. The main advantages of these sorbents are their environmental friendliness, broad raw material base, high hydrophobicity and oil capacity at a relatively low cost.

The study of the quality indicators of sorbents of natural origin was carried out in the laboratory under static conditions. Perlite, wood sawdust (from spruce), activated carbon and the biosorbent "Econadin" were used as sorbents. The efficiency of sorbents was assessed by the following indicators: water capacity, oil capacity, bulk density, buoyancy and sorption capacity for oil from the water surface. The study was carried out separately for each sorbent at a room temperature of +18° C. When determining the water and oil absorption capacity, the optimal time of the sorption capacity of the sorbent was previously determined. For this purpose, 1 g of sorbent was kept on the surface of water or oil for 5, 10, 15 and 20 min. and the amount of liquid absorbed by the sorbent was determined. Based on the constructed graphs, the optimal sorption time for each of the studied sorbents was determined. Thus, the optimal time for oil absorption by perlite and "Econadin" was 5 min.; sawdust – 15 min., coal – 10 min. Oil and water capacity were determined according to the methods [43].
Determination of oil capacity. Oil capacity is the ability of a material to absorb oil and retain it in its pores in direct contact with oil. To determine the oil capacity of sorbents, 200 ml of oil was poured into a glass crystallizer, a pre-weighed metal sieve was immersed. 1 g of the studied sorbent was evenly applied to the surface of the oil. After a certain time for each sorbent (determined by the above method), the sieve was removed, left on a glass vessel and allowed to drain the oil residues (1 min.), then the sieve was weighed together with the sorbent and the absorbed oil. The oil capacity was determined by the ratio of the mass of oil absorbed by the sorbent to the mass of dry sorbent and was calculated by the formula:

OC = (m₂ - m₁ - m_с)/m_с,where

OC – oil capacity, g oil/g sorbent;
m₂ – total mass of the sieve, sorbent and absorbed oil, g
m₁ – mass of the sieve, g
m_с – mass of the sorbent sample, g

Determination of water capacity. Water capacity (WC) – the ability of the material to absorb water and retain it in its pores in direct contact with water. Water capacity was determined similarly to oil capacity, immersing the sieve with the sorbent in distilled water and calculated as the ratio of the mass of water absorbed by the sorbent to the mass of dry sorbent (g/g).
Sorption capacity for oil from the water surface. 1.0 L of distilled water was poured into a glass crystallizer, a pre-weighed sieve was immersed in water. 2.5 g (3 ml) of oil was poured into the center of the sieve on the surface of the water, 0.834 g of sorbent (3:1) was poured evenly onto the surface of the stain. It was kept for a certain time (for each sorbent its own), the sieve was removed, allowed to drain for 1 min. and weighed. It was calculated as the ratio of the mass of oil absorbed by the sorbent to the mass of dry sorbent (g/g).
Bulk density is the ratio of the mass of bulk material to its volume, including the space between the particles. It is determined for granular and powdery materials. Buoyancy is the ability of the sorbent to remain on the surface or at a certain level in the middle of the liquid.
Determination of bulk density. 10 g of air-dry sorbent was poured into a measuring glass cylinder and the volume occupied by the sorbent was determined. Bulk density (g/L) was determined as the ratio of the mass of the sorbent to the volume it occupied.
Determination of the buoyancy of the sorbent. Buoyancy was determined by the amount of sorbent remaining on the water surface after a certain time. A 10 g portion of the sorbent was placed in a crystallizer filled with distilled water (3 L). The sorbent was evenly placed on the water surface and left for 30 min. After the specified time, the sorbent remaining afloat was collected and dried to an air-dry state. Buoyancy was determined by the formula:

B = ((m₁ - m₀)/ m₁)100%, where

B – buoyancy, %
m₁ – mass of the sorbent before contact with water, g
m₀ – mass of the sorbent remaining after contact with water, g
The measurements were carried out in four-fold repeatability. Statistical analysis of the results was performed using the Student's t-test, at P <0.05, using Microsoft Excel 2013.

The purpose of the work is to determine the effectiveness of the use of oil sorbents of natural origin by analyzing their quality indicators.
To achieve the goal, the following tasks were set:

1. to investigate the oil and water absorption capacity of sorbents of natural origin: perlite, sawdust, activated carbon and biosorbent "Econadin";
2. to study the oil capacity of these sorbents when removing oil from the water surface;
3. to determine the physical and mechanical parameters of the studied sorbents - bulk density and buoyancy;
4. to calculate the economic efficiency of the use of the studied sorbents of natural origin in the cleaning of oil pollution.

Chemical composition and physical properties of oil

Oil is a flammable oily liquid with a wide range of physical and technological properties, with a characteristic, specific odour and a complex hydrocarbon composition.
In general, oil consists of hydrocarbons, which represent the light part of oil, and non-hydrocarbon (heteroatomic) substances, which form the heavy part of oil. Different ratios of these components determine the variety of properties and composition of oil [11, 13].
Oil includes more than 450 individual compounds, its main chemical elements are carbon (82−87%) and hydrogen (11-14%), as well as a small content of sulfur (0.01−4.3%), oxygen (0.01−0.27%), nitrogen (0.02−1.7%). Oils contain metals (vanadium, nickel, iron, zinc, copper, magnesium, aluminum) in small amounts (0.02−0.03% of its mass) [33]. Oil components, which are a mixture of high-molecular compounds, molecules of which include nitrogen, sulfur, oxygen and metals, are called asphalt resinous substances (ASR). The composition of oil includes such groups of hydrocarbons as aliphatic (methane), cyclic saturated (naphthenic) and unsaturated (aromatic), mixed hydrocarbons (methane-oil, petroleum-aromatic). According to the density of oil, it is divided into fractions: light, which contains more gasoline, kerosene, and heavy, which contains more gas oil and fuel oil. Practically important properties of oil include viscosity, sulfur content, resins, paraffins, fraction yield under different heat treatment conditions. These characteristics of oil determine the conditions of its occurrence, its formation accumulations and the creation of the substance itself. The viscosity of oil is measured to determine its mobility at low temperatures. The viscosity of some types of oil can be so high that its pumping and transportation at low temperatures is practically impossible. Therefore, for these purposes, pipelines are equipped with heating. An increase in the viscosity of petroleum products with a decrease in temperature is a general pattern.
For different oils, the surface tension at the interface with air varies within 25–30 mN/m. Petroleum products that are poorly purified from polar impurities have a low surface tension at the interface with water. For well-purified types of gasoline and oils (medical, transformer), the surface tension value is up to 50 mN/m. With an increase in water mineralization, the surface tension of oil increases, but the appearance of surfactants in water, for example, organic acids, entails a decrease in the value of the surface tension.
The solubility of oil depends on the solubility of its individual components. In the direction from volatile oil components to heavy ones, its solubility decreases. The solubility of oil in water is very low and in exceptional cases exceeds 150 ml/m3. Its indicator increases with increasing temperature but decreases with increasing water mineralization. The solubility of oil in gases (reverse evaporation) is characterized to a greater extent by its light hydrocarbon components and to a lesser extent by asphalt-resin components. For the dissolution of oil by hydrocarbon gases, certain conditions must be created: high temperatures, a significant predominance of the gas phase and high pressure. The composition of oil and gas also plays an important role. With an increase in the content of heavy homologues of methane and carbon dioxide in the gas composition, the solubility of oil increases. The most important technological characteristics of oil are its boiling point under normal conditions and fractional composition: the ratio and properties of individual fractions that boil at certain temperature intervals. The products of oil refining are bitumen and petroleum coke, which are obtained from the heaviest fractions; carbon black, which is necessary for the production of rubber; the main solvents are benzene and toluene.
So, oil is a complex mixture of various hydrocarbons and non-hydrocarbon compounds, which have different consistencies. The physicochemical and structural-mechanical properties of oil are determined by its chemical composition and the ratio of individual components. Oil from different deposits differ in fractional composition, which determines the ways of industrial oil processing.

Pollution of aquatic ecosystems with oil and petroleum products

The problem of effective cleaning and measures to prevent pollution of water sources by oil products is one of the most urgent in modern conditions [10, 32].
Modern industry cannot exist without the use of such valuable raw materials as oil and oil products. However, in terms of the level of negative impact on the environment, especially on the hydrosphere, the oil industry is one of the most dangerous among other industries [27]. Oil and oil products enter the aquatic environment through their extraction and transportation, as well as during storage on the territory of enterprises, through wastewater and stormwater contaminated by them.
Significant damage is caused to marine ecosystems by transportation. Thus, about 2 billion tons of oil and oil products are transported annually by tankers. The greatest losses of oil occur due to its transportation from the areas of extraction. Constant pollution on sea routes is caused by emergency situations, the discharge of flushing and ballast water by tankers. During accidents, up to 40-50 thousand tons of oil can spill, in such cases the area of ​​contamination can be 100 km² [12]. Oil spills can cause disruption of the ecological balance and stable operation of biological systems and technological facilities. The most dangerous is oil pollution of the hydrosphere since the spill is likely to spread over large areas. Oil pollution has a toxic effect on living organisms. The permissible norm of oil and oil products in water is from 0.05 mg/dm³ to 0.1-0.3 mg/dm³, depending on the nature of the water use [6, 37, 40].
In the aquatic environment, oil products spread over the surface of the water, undergoing chemical and physical changes. In particular, they can undergo one of the following processes: assimilation by aquatic organisms, sedimentation, emulsification, formation of oil aggregates, oxidation, dissolution and evaporation [40]. The method and intensity of transformational changes of oil products in water bodies depend on the ways of their arrival and the features of hydrochemical and hydrometeorological conditions [5, 36].
According to the US Environmental Protection Agency, as a result of the arrival of 1 ton of oil into the water after 10 min. an oil slick 10 mm thick is formed. Subsequently, the thickness of the film decreases (to 1 mm or less), but the area of ​​the slick increases (1 ton can cover an area of ​​up to 12 km²) [12]. Also, oil films, due to their high stability, are able to move under the influence of winds and currents at a distance of tens and hundreds of kilometres from the place of arrival, polluting more and more new parts of the water body.
The film created by oil and oil products on the water surface complicates gas exchange and biological self-purification processes. It is known that a film of diesel fuel 0.1 mm thick slows down the gas exchange of oxygen, which negatively affects the hydrobiota and can lead to its death [17, 24]. In particular, the processes of dissolution and release of oxygen, carbon dioxide, heat exchange, and the reflectivity of seawater change.
A significant proportion of oil products that are in a suspended state are adsorbed on particles of finely dispersed mineral and organic suspended substances and settle together with them to the bottom. Oil products that have settled to the bottom enter the food chain of biota, and enter into physicochemical interaction with components of bottom sediments, negatively affecting benthic organisms and the state of the ingredients of bottom sediments [9].
In addition, aromatic and polycyclic hydrocarbons of oil products pose a particular danger when they enter drinking water. During bacterial decontamination of such waters with gaseous chlorine, polychlorinated derivatives and dioxins are formed, which are more toxic than hydrocarbons themselves.
Therefore, in order to prevent pollution of the hydrosphere with oil and oil products, it is first, necessary to improve the technological processes of extraction, transportation, storage, processing, use of oil or oil products, to exclude the discharge of wastewater containing oil and oil products. Pollution of aquatic ecosystems with oil and oil products causes significant damage to aquatic biocenoses, disrupting the exchange of energy, heat, moisture and gases, affects the physicochemical and hydrological conditions, and causes the death of fish, seabirds, mammals and microorganisms.

Application of sorbents for water purification from oil and petroleum products

There are a large number of methods for purifying water from oil spills. There are physicochemical, chemical, membrane, electrochemical, thermal, mechanical and biological purification methods. The choice of method will depend on the scale and primary source of pollution, the volume of oil emissions [2, 3]. Nowadays, considerable experience has been accumulated in the purification of oil-containing wastewater. There are many methods for preventing and disposing of oil spills, and oil sorbents occupy a very important place among them [6, 10]. Materials used to collect oil and oil products from the water surface are commonly called oil sorbents, as well as oil absorbers and oil collectors. Three main indicators are used to determine the quality of oil sorbents: buoyancy, water absorption, oil absorption [14]. Currently, about 200 types of sorbents are produced or used in the world for the elimination of oil pollution, which can be classified according to various characteristics: origin, dispersion, purpose, method of disposal. The quality of sorbents is determined mainly by their capacity for oil, the degree of hydrophobicity, buoyancy after sorption of oil or oil products, the possibility of desorption, regeneration or disposal of the sorbent. There are sorbents that float on the surface of the water and sorbents that sink in water.
By appearance, sorbents are classified into: loose sorbents; sorbents surrounded by a shell (granulated); solid; fibrous sorbents. By type, sorbents are divided into: inorganic; natural organic and organo-mineral; synthetic.
Sorbents are characterized by their absorption or adsorption capacity (sorbent activity), which is determined by the concentration of the adsorbate per unit mass or volume of the adsorbent. The maximum absorption capacity of the adsorbent possible under these conditions is conventionally called its equilibrium activity.
The structure of the sorbent largely determines its specific consumption and therefore affects the cost-effectiveness of the adsorption water purification technology. To remove organic substances, adsorbents with pore sizes of 0.5 - 10 nm are required. In this case, activated carbon and synthetic polymer sorbents are mainly used. In addition, mineral adsorbents are used - oilseeds, silica gels, clay materials, etc. They are characterized by a variety of properties and applications. They are especially widely used for the purification of gases and non-aqueous solutions.
The use of natural sorbent materials is an attractive method for combating oil spill pollution: due to lower costs, high efficiency and their properties, such as reuse, biodegradation and recovery [42]. The most promising for the elimination of hydrocarbon pollution are natural organic and organo-mineral sorbents. Wood chips and sawdust, modified peat, dried grain products, wool, waste paper, flax production waste are most often used [15, 18, 20, 21, 22]. One of the best natural sorbents in terms of its absorption capacity is wool. It can absorb up to 8–10 kg of oil per 1 kg of its mass, while the natural elasticity of wool allows you to remove most of the volatile oil fractions. However, after several such pressings, wool becomes unsuitable for further use. Its high cost, insufficient quantity and high storage requirements (wool attracts rodents, insects, and undergoes biochemical transformation) do not allow it to be considered a promising sorbent [38].
Another effective sorbent is sawdust, which absorbs pollution well and quickly but absorbs moisture even better, so its effective use requires preliminary saturation with water-repellent substances, for example, fatty acids. The created hydrophobic coating provides good quality oil sorbents but is very short-lived. The situation is similar to peat, which is much superior in its potential sorption capacity to sawdust and even wool [1].
In Ukraine, the highly effective sorption material "Ecotorf" is widely used for the elimination of emergency spills of oil and petroleum products based on environmentally friendly natural raw materials - peat [25]. Peat-based adsorbents are able to collect spills from any surface and contain them, preventing them from spreading again. For the sorbent "Ekotorf" the capacity for crude oil is 3–5 mg/g. When treated with special modifiers, the oil capacity of peat sorbents can be increased. At the same time, the buoyancy in the saturated state is from 2 to 10 days due to the small amount of water absorption (70–100%). With a film thickness of 0.1 cm and an ambient temperature of 12–15 °C, the economic consumption in case of emergency spills is 0.2–0.3 kg/m. The sorbent is characterized by ease of application and collection by hand using auxiliary mechanical devices, or using special pumping and suction equipment, aviation equipment. Utilization of oil-saturated sorbents is carried out either by burning or composting with soil [19]. Based on hydrocarbon and oil destructors absorbing sorbents in Ukraine, the preparations "Ekolan" and "Rodoyl" were created to clean soil and water from oil pollution. In model studies using these preparations, the greatest reduction in the concentration of hydrocarbons in water was achieved in 7 days by 89.6%, in soil in 3 months by 92.7%, and in oil sludge in 6 months by 92.1% [30].
One of the options for solving the problem is to combine preparations that have the properties of sorbents and preparations based on hydrocarbon-destructor microbes. The preparation "Econadin" has been developed, which is a fairly effective sorbent with some destructive activity against a certain spectrum of oil hydrocarbons [8]. This sorbent localizes oil pollution and destroys adsorbed oil products by a biological method. Unlike other sorbents, the sorbent is not collected after use. Within a few days after oil sorption, the preparation sinks to the bottom. The decomposition of petroleum hydrocarbons localized on the preparation occurs directly in the aquatic environment.
Synthetic sorbents are made on the basis of hydrated cellulose, polyurethane in spongy or granular form, as well as polypropylene fibres formed into non-woven roll materials of various thicknesses. In addition, molded polyethylene with polymer fillers and other types of plastics are used. They are most often used in countries with highly developed industry (USA, EEC countries, Japan). Synthetic materials, as a rule, have a high oil capacity, but most of them are toxic (which limits their use in the form of fine powders), especially in the event of fire. The disadvantages of these preparations should also include the poor absorption capacity of thin oil films, and the difficulty of disposal [41].
So, various organic, inorganic and synthetic materials are used as oil sorbents. Strict requirements are set for sorbents: when in contact with the water surface, sorbents must collect oil or oil products, with a minimum process of water adsorption. The sorbent must have high buoyancy, that is, remain on the water surface for a long time, preventing the return of oil products into the water. The use of natural sorbent preparations does not cause a negative impact on aquatic organisms of freshwater ecosystems. The main advantage of these sorbents is the ability to almost completely eliminate oil products directly at the place of application. At the same time, both the sorbent itself and the products of its interaction with oil products are environmentally friendly and do not require special disposal.

Characteristics of oil and sorbents of natural origin

The research used oil "URALS" (photo 2.1, A). "URALS" is a mixture of heavy high-sulfur oil of the Urals and Volga regions (the sulfur content of which reaches 3.0%) with light West Siberian oil Siberian Light (sulfur content of 0.57%). The final sulfur content of oil of the Urals grade is no more than 1.2-1.4%, density in degrees API - 31-32 (or 860-871 kg / m³). It has a characteristic dark brown color.
Four sorbents of natural origin were selected for the study: inorganic sorbent - perlite, organic - sawdust and coal and biosorbent "Econadin".
Perlite belongs to the class of natural silicate rocks of volcanic origin. Its peculiarity is that when heated rapidly at a temperature of 900-1100°C, it increases in volume up to 20 times and turns into porous white granules 1-10 mm in size. The result is a very light environmentally friendly material with excellent heat-conducting qualities, which allows the use of perlite and final products from it in many industries: construction, metallurgy, agriculture and other areas in the temperature range from -200°C to +900°C.
A B
C D
E
Photo 2.1. Materials used in the studies:
A - oil "URALS"; B - perlite; C - sawdust; D - activated carbon;
E - biosorbent "Econadin" (photo by M. Lupul)

The drug also has high porosity, which increases the sorption capacity. To increase sorption, perlite is additionally treated with polysilicon (hydrophobized). Large industrial reserves of perlite raw materials are located in the Transcarpathian region of Ukraine (the Fogosh deposit). This is the only unique perlite deposit in Ukraine. Other deposits in the CIS exist only in the Russian Federation (in small quantities) and Armenia. The experiment used perlite with a granule size of 2-4 mm (photo 2.1, B).
Sawdust is wood particles formed as sawing waste, a type of crushed wood. The length of sawdust particles depends on the type and technological parameters of the cutting tool, as a result of which they are formed. Sawdust contains about 70% carbohydrates (cellulose and hemicellulose) and 27% lignin. The balance of chemical substances: is 50% carbon, 6% hydrogen, 44% oxygen and about 0.1% nitrogen [28]. In the experiment, coniferous sawdust (spruce) was used as a sorbent. The particle size is 0.5-1.5 cm² and the thickness is 0.5 mm (photo 2.1, B).
Activated carbon is a substance with a highly developed porous structure, which is obtained from various carbon materials of organic origin, such as charcoal, coal coke, petroleum coke, coconut shells, walnuts, apricot kernels, olives and other fruit crops. Activated carbon consists of 87-97% by weight of carbon, and may also contain hydrogen, oxygen, nitrogen, sulfur and other substances. Activated carbon has a huge number of pores and therefore has a very large surface area, as a result of which it has a high adsorption capacity (1 g of activated carbon, depending on the manufacturing technology, has a surface area of ​​​​from 500 to 1500 m²). It is this high level of porosity that makes activated carbon “activated”. The increase in the porosity of activated carbon occurs during a special treatment - activation, which significantly increases the adsorbing surface [28]. In our experiment, coconut activated carbon with a size of 2 to 5 mm was used (photo 2.1, D). "Econadin" is a biological sorbent that combines the properties of organic sorbents and the destructive properties of microbial preparations [4]. This is an organic material (top sphagnum peat) with a high absorbent capacity, on which avirulent oil-oxidizing bacteria are applied, which exhibit sorption and destructive properties in relation to oil hydrocarbons. Specially selected bacteria (1 g of the preparation contains 107 bacteria) oxidize oil hydrocarbons to water and carbon dioxide. The preparation is based on a culture of hydrophilic bacteria Pseudomonas fluorescens 2-aB-2256 [16]. The sorbent has a light brown color, a dispersed composition with fibrous inclusions, has buoyancy and hydrophobic properties (photo 2.1, E). It is used for cleaning oil pollution from the water surface, wastewater, hard surfaces (road surfaces, concrete, metal surfaces) and soil bioremediation. It is used by pouring the sorbent onto the contaminated water surface.

Surface water purification from pollution includes the removal of oil film by mechanical and/or physicochemical methods. The most promising and environmentally appropriate detection of oil and oil products using oil sorbents [7, 35]. The advantages of the sorption method include the ability to remove contaminants of any nature to a minimum protein concentration.
The main requirements for the quality of oil sorbents for the collection of oil and oil products are high oil absorption and low water absorption capacity, buoyancy. The regeneration capacity of the sorbent, its availability and cost are also important. The effectiveness of sorbents is assessed, first of all, by the value of oil capacity. The water absorption rate can be adjusted by additional hydrophobization, reducing the ability to absorb water. Sorption materials with low buoyancy can be used in products with reinforcing plant - booms, mats, etc. [7].
At the first stage of the study, we studied the absorption properties of the studied sorption materials depending on the contact time. The water and oil absorption of the sorbents was studied. Perlite and wood sawdust have a higher ability to absorb water than oil (Fig. 3.1, 3.2). The water absorption capacity of perlite during the first 10 min. remains at the level of 9.2 g/g, and then rapidly decreases over time (Fig. 3.1). The highest oil capacity of perlite (7.6 g/g) during the first 5 min., then decreases during the next 10 min., and then increases.
The ability of sawdust to absorb water during the first 10 min. increases (8.5 - 9.8 g/g), and then decreases, reaching a plateau (Fig. 3.2). In turn, the oil capacity of sawdust increases and reaches a maximum after 15 min. (7.7 g/g).

Fig. 3.1. Sorption capacity of perlite depending on contact time (min), g/g

 

Fig. 3.2. Sorption capacity of sawdust depending on contact time (min), g/g

 

Regarding "Econadin" and coal - we observed the opposite picture. These sorbents have a higher oil absorption capacity than water absorption (Fig. 3.3, 3.4). At the same time, the ability of "Econadin" to absorb oil decreases
during the observation period, with a maximum oil capacity during the first 5 min. (4.4 g/g) (Fig. 3.3). The maximum water capacity of this sorbent is your

Fig. 3.3. Sorption capacity of "Econadin" depends on contact time, g/g

 

after 15 min. of contact with the water surface (2.7 g/g). The water and oil absorption capacity of coal increases slightly with increasing contact time with the surface liquid and reaches a maximum value after 20 min. – 5.7 g/g and 3.6 g/g, respectively (Fig. 3.4). In the literature [35] it is noted that the sorption of oil and oil products exclusively by sorbents significantly depends on the density of the sorbent itself and the viscosity of the oil, as well as on the saturation time.
Therefore, the oil capacity of the studied sorbents varies depending on the contact time with oil, which is associated with the structure of the sorbents, in particular their porosity and saturation time. Also, perlite and "Econadin" exhibit a high ability to absorb oil within 5 min., while activated carbon – within 10 min., and sawdust – 15 min.

Fig. 3.4. Sorption capacity of coal properties depending on contact time, g/g

 

According to the results of our research, high oil capacity of sawdust (5.39 g/g) and perlite (5.14 g/g) was found in the state with "Econadin" and coal (Table 3.1).

Table 3.1. Properties of natural sorbents

Sorption properties	Perlite	Wood sawdust	"Econadin"	Coal
Oil capacity, g/g	5.14 ± 0.09#	5.39 ± 0.30#	2.47 ± 0.26	3.86±0.07**
Water capacity, g/g	6.62 ± 0.19	7.57 ± 0.27*	1.46 ± 0.13	2.39±0.10**

Note: * – significant difference between the water capacity of sawdust and other sorbents according to the Student's t-test, at P <0.05; ** – significant difference between the values ​​of "Econadin" and coal according to the Student's t-test, at P <0.05; # – significant difference between the indicators of perlite or sawdust depending on “Econadin” and coal according to the Student’s t-test, at P <0.05

At the same time, the conducted studies showed that perlite and sawdust with “Econadin” and coal have a high water absorption capacity (Table 3.1). Therefore, according to this indicator, the use of “Econadin” and coal is more rational. The obtained results are consistent with the literature data. The scientific literature [7, 29] indicates that wood sawdust has a high oil capacity, but the disadvantage of its widespread use in oil pollution is its high water capacity. This problem is solved by increasing its hydrophobicity by treating sawdust with water-repellent substances, e.g. fatty acids. In addition, the author [23] showed that sawdust absorbs oil from the surface of the water well under conditions of a large layer of it, and with a small layer - sawdust absorbs more water, which in its place displaces the oil product. Therefore, it is recommended to use sawdust as a sorbent in emergency spills of oil and oil products immediately after the accident, when the layer of oil products or oil is large enough.

Modification of perlite with organosilicon compounds leads to its hydrophobization and increased floating oil collection efficiency [31]. In addition, the main advantages of these sorbents are environmental friendliness, safety, a wide raw material base and high oil capacity compared to low cost.
"Econadin" refers to biosorbents, the action of which is based on the use of microorganisms-destructors and their fixation on water-insoluble carriers. The authors [16] showed that the effectiveness of biosorbents, in particular, "Econadin" depends on the temperature of the environment and the chemical composition of petroleum products. The optimal temperature is +28° C, and in our studies, the temperature in the room was +18° C, which probably explains the low oil capacity of "Econadin".
Activated carbon is a solid porous material, the adsorption properties of which are determined by the porous structure, which is formed by various combinations of graphite crystallites and amorphous carbon. Activated carbon is obtained from all types of carbon-containing raw materials: wood, cellulose, various types of coal, peat, nut shells and fruit stones. Depending on the type of raw material, activated carbon with different porosity is obtained. In particular, activated carbon based on coconut shells has developed microporosity and is effective for the extraction of low-molecular compounds.
The next stage of research is the study of oil sorption by sorbents from the water surface. According to the results of the study, it was found that the studied sorbents of natural origin have different absorption capacities for oil from the water surface. Thus, the absorption capacity of "Econadin" and coal is the same and is 1.17 g/g, while perlite and sawdust absorb 1.33 g and 1.58 g of oil, respectively (Fig. 3.5). At the same time

Fig. 3.5. The mass of oil absorbed from the water surface by sorbents, g/g

 

The percentage of oil retained by perlite and sawdust is 42−44%, while Econadin and coal retain 62−63% of oil (Fig. 3.6). When removing oil from the water surface and sorption treatment of wastewater, sorption occurs mainly due to the adhesion of the pollutant to the surface of the particles of the sorbent material [34]. The amount of oil and oil products absorbed depends on the hydrophobicity, oleophilicity and the size of the specific surface area of ​​the sorbent material.

Fig. 3.6. Percentage of oil retained by sorbents

One of the main indicators of the quality of oil sorbents is buoyancy. Floating sorbent materials are easy to use for collecting oil and oil products from the water surface. Buoyancy depends on the speed of water penetration into the pores, the ratio of open and closed pores [34]. High buoyancy allows the sorbent to remain on the surface for a long time without causing secondary pollution.
A comparative analysis of the buoyancy of sorption materials showed that sawdust (78.31%) and coal (81.9%) have lower buoyancy (Fig. 3.7). Perlite (98.5%), which can be explained by its structure, and "Econadin" (91.14%), since the carrier in this biosorbent is sphagnum moss, has high buoyancy. Among the studied sorbents, sawdust has a relatively low buoyancy and high water absorption capacity, therefore, when using this sorbent, the removal of saturated sorption material from the water surface should occur in a short time. Also, this sorbent is probably better to use for dynamic treatment of wastewater containing oil and oil products.

Fig. 3.7. Buoyancy of the studied sorbents

The main indicator of efficiency when choosing a sorbent is the bulk density, which is expressed in the amount of sorbent weight per unit volume (g/dm3). Bulk density depends on the size of the sorbent particles: the smaller they are, the higher the bulk density. This indicator is related to transportation and economic profitability of using the sorbent. In order of increasing bulk density, the studied sorbents can be placed in the following order: sawdust → perlite → coal → "Econadin" (Fig. 3.8).

Fig. 3.8. Bulk density of sorbents, g/dm3

The cost of the studied oil sorbents was researched (Table 3.2), which shows that it is economically profitable to use "Econadin" and wood sawdust for cleaning oil pollution. These materials have a lower cost than activated carbon and perlite.

Table 3.2.
Cost of sorbents required for cleaning oil pollution from the water surface 

Sorbent	Average price of sorbent per 1kg, CAD.	Amount of oil absorbed by 1 kg of sorbent, kg	Amount of sorbent for cleaning 1 kg of oil, kg	Cost of sorbent for cleaning 1 ton oil pollution , CAD.	Cost of sorbent for cleaning 1 barrel oil pollution , CAD.
Perlite	21	1,33	0,750	15750	2142
Sawdust	16	1,58	0,632	10112	1375
Coal	18	1,17	0,858	15444	2100
«Econadin»	5	1,17	0,857	4285	641

Thus, the analysis of the oil sorption capacity of the studied sorbents of natural origin showed that taking into account the main indicators - oil capacity, water capacity, oil sorption from the water surface, buoyancy and bulk density, the use of the biosorbent "Econadin", activated carbon and perlite is more effective. To use wood sawdust as an oil sorbent, it is necessary to first carry out its hydrophobization. Also, taking into account the high oil capacity and low cost of wood sawdust, further research is necessary to optimize the use of this material as an oil sorbent.

1. It is shown that perlite and sawdust have a high oil capacity (t = +18° C) of 5.14 g/g and 5.39 g/g, respectively, which is observed against the background of a high water capacity of 6.62 g/g and 7.57 g/g.
2. Low water capacity of "Econadin" and activated carbon (1.46 and 2.39 g/g, respectively) and oil capacity (2.47 and 3.86 g/g, respectively) were established. At the same time, the oil capacity of activated carbon is higher than that of "Econadin", which may be due to temperature conditions.
3. It was found that the studied natural sorbents differ in their ability to absorb oil from the water surface. Thus, the sorption capacity for oil of "Econadin" and coal is the same and is 1.17 g/g, while perlite and sawdust absorb 1.33 g and 1.58 g of oil, respectively. At the same time, the share of oil retained from the water surface by "Econadin" and coal is 62-63%, and by perlite and sawdust - 42-43%.
4. It is shown that perlite and "Econadin" have high buoyancy (98% and 91%, respectively), while activated carbon and sawdust have lower buoyancy (82 and 78%, respectively).
5. The studied natural sorbents can be arranged in a row in ascending order of bulk density: sawdust → perlite → coal → "Econadin".
6. Due to the high water absorption capacity and relatively low buoyancy of wood sawdust (fraction 0.5-1.0 cm), it can be recommended to carry out its hydrophobization or use it for dynamic treatment of wastewater containing oil and oil products in the composition of filters.

Note, many of the sources used in this work are in Ukrainian language 

1. Адсорбция органических веществ из воды  /Когановский А.М., Клименко Н.А., Левченко Т.М., Рода И.Г. Химия, 1990. 256 с.
2. Аренс В.Ж., Саушин А.З., Гридин О.М., Гридин А. О. Очистка окружающей среды от углеводородных загрязнений. М., 1999. 370 с.
3. Бека К., Высоцкий П. Геология нефти и газа. М., 1976. 592 с.
4. Биопрепарат «Эконадин» − сорбент биодеструктор углеводородов нефти URL: https://econadin.com/wp-content/uploads/2018/01/Biosorbent-E%60konadin-2018.pdf 
5. Бойченко С. В., Черняк Л. М., Радомська М. М., Бондарук А. В. Проблема очищення природних водойм, забруднених стічними водами об’єктів сфери нафтопродуктозабезпечення. Наукоємні технології. 2015. № 4. С. 353–357.
6. Бордунов В.В., Бордунов С.В., Леоненко В.В. Очистка воды от нефти и нефтепродуктов. Экология и промышленность России. 2005. С. 8–11.
7. Веприкова Е.В., Терещенко Е.А., Чеснокова Н. В., Щипкова М.Л., Кузнецова Б.Н. Особенности очистки воды от нефтепродуктов с использованием нефтяных сорбентов, фильтрующих материалов и активных углей. Journal of Siberian Federal University. Chemistry. 2010. С.285–304.
8. Гігієнічний висновок Державної санітарно-гігієнічної експертизи на вітчизняну продукцію Препарат бактеріальний «Еконадін-1», № 50403/2317: 2000. 2с.
9. Гринюк В. І. Моделювання процесу поширення нафтопродуктів у воді правої притоки р. Свічі. Науково-технічний журнал. 2020. № 1(21). С. 41–48. 
10. Гурвич Л.М., Немировская И.А. Роль неуглеводородных компонентов нефти в загрязнении гидросферы. Океанология. 2009. С.516–522.
11. Давыдова С.Л. Нефть и нефтепродукты в окружающей среде. М., 2004. 163 с.
12. Дембович Б. І., Яворська С. В. Забруднення океанів нафтою та нафтопродуктами. «Біорізноманіття та роль тварин в екосистемах»: Матеріали VІІ Міжнародної наукової конференції. Дніпропетровськ: Адверта, 2013.  С. 45−48.
13. Другов Ю.С., Родин А.А. Экологические анализы при разливах нефти и нефтепродуктов. М., 2015. 48 с.
14. Зеленько Ю.В. Поглотительная способность материалов, используемых для ликвидации транспортных аварий с нефтепродуктами. Экотехнологии и ресурсосбережение. 2004. С.35–37.
15. Ивасишин П.Л. Ликвидация последствий разливов нефти посредством биоразлагающих сорбентов. Нефтяное хозяйство. 2009. № 5. С.112–113.
16. Каблов В.Ф., Уткина Е.Е., Быкадоров Н.У. Использование сырьевых ресурсов региона для решения проблем загрязнения водных объектов нефтепродуктами. Фундаментальные исследования. 2011. № 8 (Ч. 2). С.406–409.
17. Казанок А. В., Матвєєва О. Л. Очищення  нафтозабруднених стічних вод за допомогою біосорбентів. Наукоємні технології. 2014. № 1 (21) С.131–134.
18. Кириченко О. В.,  Мальований М. С. Очищення природних водойм від нафтопродуктів гідрофобізованими сорбентами. Науковий вісник НЛТУ України. 2009. С.60–64.
19. Климов Е.С. Природные сорбенты и комплексоны в очистке сточных вод / за ред. М.В. Бузаева. Ульяновск: УлГТУ, 2011. 7с.
20. Кожанова Г.А. Методи ліквідації нафтового забруднення з застосуванням сорбенту «Екоторф». Вісник Одеського національного університету. Біологія. 2001. С.154–157.
21. Колосов П.В., Базарнова Н.Г., Маркин В.И. Высокомолекулярные продукты карбоксиметилирования растительного сырья с сорбционными свойствами. Барнаул: Изд-во АлтГУ, 2013. 51 с.
22. Косов В.И., Испирян С.Р. Использование торфа для очистки вод, загрязненных нефтепродуктами. Вода и Экология: проблемы и решения.  2001. № 4.  С.41–46.
23. Кравченко О.В., Швець Д.І. Дослідження сорбції нафтопродуктів вуглецевими матеріалами на основі рослинної сировини. Хімія, фізика та технологія поверхні. 2004. Вип. 10. С.161–165.
24. Кулагін О.О. Еколого-гігієнічна оцінка та регламентація вмісту нафтопродуктів у чорноземному ґрунті і шляхи його біологічної ре медіації: десерт…. кандидата медичних наук, спеціальність 03.00.16 – екологія (медичні науки). Дніпро. 2017. 155 с.
25. Ллорі Дж. Методологія екологічно-безпечного відновлення забруднених нафтопродуктами територій і акваторій: магістерська робота, спеціальність 8.04010603 «Екологічна безпека». Вінниця. 2017. 83 с.
26. Максимюк М. Р., Міцкевич Д. І., Міцкевич А. І. Нафтове забруднення поверхневих вод та шляхи подолання його наслідків. Наукові праці. Техногенна безпека. Вип.221. Т.233. С. 37–40.
27.   Мальований М. С. Очищення води від нафтопродуктів природними та модифікованими сорбентами. Екологія довкілля та безпека життєдіяльності. 2007. № 4. С. 61–65.
28. Матвєєва О.Л., Бондарець Ю.В. Дослідження характеру сорбції матеріалу на основі торф’яного моху роду Sphagnum. Восточно-Европейский журнал передовых технологий. 2014. 5/10(71). С. 80–85.
29. Матвєєва О.Л., Демянко Д.О., Копиленко A.B., Шараєв К.О. Ефективність застосування сорбентів при очистці забруднених вод. Харчова промисловість. Вип. 12. 2012. С.162–166.
30. Матвєєва О. Л., Качуренко, Я. О. Аналіз методів очищення нафтовмісних вод із застосуванням рослинних сорбентів типу Sphagnum. Наукоємні технології. 2013. № 17(1). С. 97–99.
31. Орлов Д.С., Садовникова Л.К., Лозановская И.Н. Экология и охрана биосферы при химическом загрязнении. М., 2002. 334 с.
32. Павлюх Л.І. Удосконалення технології очищення нафтовмісних стічних вод сорбентами рослинного походження. 2012. 23 с.
33. Панченко В. О., Гусак О. Г., Папченко А. А. Гідроаеромеханіка нафтогазових комплексів : навчальний посібник.  Суми : Сумський державний університет, 2016.  151 с.
34. Привалова Н.М., Двадненко М.В., Некрасова А.А., Попова О.С.,
    Привалов Д.М. Очистка нефтесодержащих сточных вод с помощью
    природных и искусственных сорбентов. Научный журнал КубГАУ.  2015. 113(09). С. 1–10.
35. Сироткина Е.Е., Новоселова Л.Ю. Материалы для адсорбционной очистки воды от нефти и нефтепродуктов. Химия в интересах устойчивого развития. 2005. № 13. С. 359−377. 
36. Стахов Е.В. Очистка нефтесодержащих сточных вод предприятий хранения и транспорта нефтепродуктов.  Санкт-Петербург.: Недра, 1983. 263 с.
37. Стебельська Г. Я. Новий погляд на проблему класифікації нафт. Вісник Харківського національного університету імені В.Н. Каразіна. Серія «Геологія. Географія. Екологія». 2017. Вип. 46. С. 50−56.
38. Татаринцева Е.А. Полифункциональные сорбционные материалы на основе модифицированных отходов промышленности для очистки вод : дисерт….доктора технических наук, 03.02.08 − экология (химия и нефтехимия). Саратов. 2020. 425 с.
39. Темирханов Б.А., Султыгова З.Х., Саламов А.Х., Нальгиева А.М. Новые углеродные материалы для ликвидации разливов нефти. Фундаментальные исследования. 2012. № 6. С. 471−475.
40. Теут В. М. Аналіз физико-хімічних властивостей нафти і нафтопродуктів, що впливають на водне середовище при розливі в морських акваторіях: постановка завдання і шляхи його рішення. Системи управління, навігації та зв’язку. 2016. № 3. С. 129–131.
41. Трусова В.В. Очистка оборотных и сточных вод предприятий от нефтепродуктов сорбентом на основе бурых углей: дис. канд. хим. наук: 05.23.04. Иркутск, 2014. 132 с.
42. Хлесткин Р.Н., Самойлов Н.А., Шеметов А.В. Ликвидация розливов нефти при помощи органических сорбентов. Нефтяное хозяйство. 2006. № 2. С.46–49.
43. Чухарева Н.В., Рожкова Д.С., Хадкевич И.А. Исследование нефтеемкости  верхового торфа по отношению к товарной нефти и газовому конденсату. Международный научно-исследовательський журнал. 2012. Вып. 5(5). С. 132–134.
44. Шамраев А.В., Шорина Т.С. Влияние нефти и нефтепродуктов на различные компоненты окружающей среды. Вестник ОГУ. 2009.  № 6. С.642–645.
45. Ярошовець К., Ремезова О. Еколого-економічна ефективність використання торфових сорбентів для розв'язання екологічних проблем. Вісник КНУ імені Тараса Шевченка. Сер. Геологія. 2021. № 1(92). С. 103–107.
46. Belgiorno V. Oil and Grease Removal from Industrial Wastewater Using New Utility Approach. 2014. 2 p.
47. Fingas M. The basics of Oil Spill Cleanup. Lewis publishers: Boca Raton, Florida: 2001. 208 p.

I would like to thank my science fair coordinator, Jacqueline Pollard and scientific advisor, Iryna Sytnikova for guidance and inspiration.