Bitumen Extraction from Bituminous Sands by Ultrasonic Irradiation

Abstract

This paper discusses the efficiency of ultrasonic-assisted bitumen extraction from bituminous sands of the Beke deposit (Mangistau region, Kazakhstan) using alkaline aqueous solutions. The process parameters, including ultrasonic frequency (22 kHz), power (up to 1500 W), solution pH (>12), and optimal NaOH concentration (1 wt.%) were optimized to achieve a maximum bitumen recovery of 98 wt.% within 8 min. The most effective sand-to-solution mass ratio was determined as 1:2, while the optimal process temperature was 75 °C. The application of ultrasound significantly enhances cavitation and reagent penetration, enabling efficient separation of bitumen with minimal chemical usage. Fourier-transform infrared (FTIR) spectroscopy and GC–MS analyses revealed the presence of aromatic hydrocarbons, paraffinic and naphthenic structures, as well as sulfur- and oxygen-containing functional groups (e.g., sulfoxides, carboxylic acids). These characteristics suggest moderate maturity and a high degree of aromaticity of the organic matter. Despite suitable thermal and compositional properties, the extracted bitumen exhibits a relatively low stiffness and softening point, indicating the need for additional upgrading (e.g., oxidation) prior to use in road construction. Although standard rheological tests (e.g., dynamic shear rhinometry) were not conducted in this study, the penetration and softening point values suggest a relatively soft binder, possibly unsuitable for high-temperature paving applications without modification. Future research will focus on rheological evaluation and oxidative upgrading to meet the ST RK 1373-2013 specification requirements.

1. Introduction

Heavy oil and bitumen contained in bituminous sands are not referred to as estimated global oil reserves. The largest known bitumen deposits are located in the Orinoco Belt (Venezuela) and the Athabasca region (Canada). Bitumen reserves have been identified in 63 geological provinces, and they range from 1.7 to 1.8 trillion barrels, which is comparable to the current global reserves of conventional crude oil (approximately 1.75 trillion barrels). Bitumen can be a significant energy resource, but its extraction and processing require non-standard technologies and approaches. At present the global leader in the development and the processing of petroleum bituminous sands is Canada. Substantial bitumen resources were also found in the United States, Nigeria, Angola, Madagascar, Kazakhstan, and Indonesia. Smaller deposits are present in China, Europe, and the Middle East (Figure 1).

More than 50 bituminous sand deposits were found in Kazakhstan. The estimated resources of natural bitumen in the northeastern zone of Western Kazakhstan are approximately equal to 1 billion tons at depths of around 120 m, where total bituminous sand resources exceed 15 to 20 billion tons. The chemical composition of these sands is not studied enough. However, they can produce 10–22% of organic matter, including resinous–asphaltene substances, kerosene–gas oil fractions, oil components, and low sulfur content. Despite this, many deposits are now under conservation, so bitumen extraction process research is not being actively carried out at this moment.

Today Kazakhstan has four bitumen production plants, the combined annual capacity of which is 1.0 million tons, while the total bitumen demand for the road construction sector is nearly 1.3 million tons per year. Only additional imports can compensate for this shortage.

The increasing demand for road bitumen requires the development of new sources for its production. In this context, the vast reserves of bituminous sands are of huge interest. Due to the high viscosity of bitumen and the lack of well-developed extraction technologies, there are problems with their extraction and processing. Furthermore, the minimization of using expensive and environmentally hazardous organic solvents in the bitumen recovery process is also essential.

This problem can be solved by ultrasonic technologies, which enable efficient separation of heterogeneous systems with a minimal consumption of chemical reagents [3]. Ultrasonic waves induce cavitation, localized heating, and intense mixing, thereby enhancing heat and mass transfer processes that facilitate the separation of bitumen from sand [4]. Chemical reagents penetrate the pore structure more effectively due to capillary forces intensified by ultrasonic action. According to paper [5], ultrasound irradiation requires the presence of a liquid phase to reduce bitumen viscosity.

Using ultrasound in combination with the reagent tetrahydrofuran (THF), up to 88% of bitumen was recovered and 42% of sulfur was removed [6]. When hydrogen peroxide was employed together with THF, bitumen recovery achieved 93%, and sulfur removal reached 86% [7].

According to the literature [8], calcium ions present in the mineral fraction of bituminous sands can interact with the carboxyl groups of natural bitumen to form calcium carboxylates, which create strong bonds between clay minerals and bitumen. To break these bonds, surfactants are needed, as they reduce the interaction forces between the mineral matrix and bitumen. Additionally, the adsorption or adhesion of resin and asphaltene components onto the sand surface is another key factor that hinders efficient bitumen separation.

The use of surfactants in ultrasonic bitumen extraction from bituminous sands has been shown to significantly improve extraction efficiency [9,10]. Surfactants reduce the interfacial tension between bitumen and water and facilitate the detachment of bitumen from solid surfaces [11].

In our view, the increase in the pH of the aqueous solution enhances bitumen extraction efficiency. Besides high molecular components of bitumen forming surfactants with alkali ions in solution [10], that improves the bitumen extraction.

In the previous studies, bitumen was extracted from bituminous sands using ultrasound at 28 kHz. The bitumen recovery rate from alkaline solutions with the help of ultrasound together with CO₂ injection reached approximately 70% [12,13]. Surfactants reduce the interfacial tension between bitumen and water, thereby improving separation efficiency [14]. Moreover, the increase in pH of the solution enhances extraction, as the carboxylic acids in bitumen react with alkaline agents, facilitating improved recovery [15].

Recent studies have shown that combining ultrasound with alkaline media and CO₂ injection enables bitumen recovery rates of 70% or higher [16,17]. This study focuses on optimizing ultrasonic parameters (frequency, power, duration), surfactant selection, and alkaline conditions to maximize extraction efficiency while minimizing reagent consumption and environmental impact [18,19]. In addition, integrated technologies that combine ultrasound, surfactants, and environmentally friendly solvents have demonstrated a promising potential for sustainable, industrial-scale bitumen recovery [20,21].

This present study aims at investigating the influence of various factors on ultrasonic bitumen extraction from the Beke deposit bituminous sands in Kazakhstan using alkaline solutions.

2. Materials and Methods

The object of this study is the bituminous sands from the Beke field in the Mangistau region. A distinctive feature of these deposits is the natural exposure of bituminous sands at the surface, which facilitates their exploration and extraction. Bituminous sand deposits commonly occur as lenses and layers. Visually, the bituminous sand is black and glossy, and all its grains are coated in viscous bitumen. At 20 °C, the sand is difficult to separate; although, at 50–60 °C, it easily breaks down into a mastic mass when the bitumen viscosity decreases.

Natural bitumen extraction from the bituminous sands by ultrasound was conducted on the MLUK-3/22-OL laboratory setup (Figure 2).

The bituminous sand was ground to a particle size of 100–200 microns to enhance its reactivity. The finest fractions were obtained using a soil mill, then weighed and placed into a 500 mL glass vessel, where 200 mL of water and the required amount of alkaline reagent were added to achieve a pH of 12 or higher. Bitumen extraction was carried out using aqueous solutions of NaOH (1.25 mol/L), KOH (0.89 mol/L), Na₂SiO₃ (0.5 mol/L), or Na₂CO₃ (1.13 mol/L). The optimal mass ratio of bituminous sand to solution was 1:2 (50 g of bituminous sand to 100 g of solution). The ultrasonic separation process lasted 8–15 min, during which bitumen floated to the surface while the mineral fraction settled at the bottom. The yield of the organic component reached 95–96%. The remaining solution was filtered, then the filter was dried and weighed, and the precipitated sand was also dried.

The group composition of the natural bitumen organic fraction was determined using a conventional analytical procedure. Initially, the asphaltene content in the sample was measured using Golde’s cold precipitation method. Subsequently, the concentration of resins in the obtained maltenes was calculated by adsorption chromatography. For this purpose, the sample was applied to activated silica gel (ASK). It was placed in a Soxhlet extractor and underwent sequential extraction: first, hydrocarbon components (oils) were eluted with n-hexane, followed by resins using a 1:1 ethanol–benzene mixture [22].

The individual composition of the oils was analyzed by gas chromatography–mass spectrometry (GC–MS, Shimadzu, Japan) using a GSMS-QP5050 system equipped with a DB5-MS capillary column, with helium as the carrier gas. The temperature program ranged from 80 to 290 °C, with a heating rate of 2 °C/min.

Compound identification was performed by comparing mass spectra with reference libraries NIST11, NIST02, and Wiley229, focusing on characteristic ions for various hydrocarbon classes.

Infrared (IR) spectroscopy of bitumen was recorded using Fourier transform infrared (FTIR) spectroscopy on a Nicolet 205xB spectrophotometer (Madison, WI, USA).

3. Results and Discussion

3.1. The Influence of Ultrasound Irradiation Power and Frequency on Bitumen Extraction

The experimental results demonstrated that the improvement of ultrasound power at 22 kHz in all alkaline solutions leads to a rise in bitumen yield (Figure 3). At 1500 W, up to 98 wt.% of bitumen was extracted from the sand. In the case of pure water, bitumen extraction began when the power exceeded 1000 W and reached a maximum yield of 80 wt.% at 1500 W.

The influence of ultrasound power on bitumen yield from bituminous sand is attributed to the concentration of cavitation bubbles in the solution; an increase in bubble concentration enhances the degree of bitumen separation from the mineral matrix.

The experimental results showed that an increase in ultrasound power at 22 kHz in all alkaline solutions causes an increase in bitumen yield (Figure 3). At a power level of 1500 W, up to 98 wt.% of bitumen was extracted from the sand. In the case of pure water, bitumen extraction starts when the ultrasound power exceeds 1000 W, reaching a maximum yield of 80 wt.% at 1500 W.

The observed effect of ultrasound power on bitumen recovery from bituminous sand is due to the concentration of cavitation bubbles in the solution. An increase in bubble concentration enhances the degree of bitumen separation from the mineral matrix.

Figure 3 shows the effect of increasing ultrasonic power on the yield of bitumen extraction from bituminous sands using various alkaline solutions at 22 kHz. Extraction efficiency is expressed as the percentage of bitumen recovered by weight (wt.%).

The graph illustrates a clear positive correlation between ultrasonic power and bitumen extraction yield throughout all tested reagents. At lower ultrasonic power levels (below 320 W), bitumen extraction yield is relatively low for all solutions, and its values are below 30 wt.%. Among the reagents, Na₂SiO₃ exhibited the highest extraction efficiency, reaching 0.7 wt.% at 80 kHz. Na₂CO₃, NaOH, and KOH also demonstrated relatively high yields, with slight variations across the frequency range. Specifically, Na₂CO₃ showed a peak at 59 kHz followed by a slight decline at 80 kHz, while NaOH and KOH maintained stable extraction efficiencies beyond 40 kHz. In contrast, distilled water exhibited the lowest extraction performance, although a steady increase in frequency was observed, reaching only 0.4 wt.% at 80 kHz. These results suggest that increasing ultrasonic frequency enhances cavitation and mass transfer processes, thereby improving bitumen detachment from the sand matrix. Nonetheless, the effect is more pronounced in alkaline media than in pure water, indicating that the chemical nature of the solution plays a critical role in facilitating extraction. Sodium silicate (Na₂SiO₃), in particular, was found to be the most effective reagent under the tested conditions.

As ultrasonic power increases from 320 W to 800 W, a steep rise in bitumen recovery is observed, particularly for NaOH, Na₂CO₃, and Na₂SiO₃ solutions. Among these, Na₂SiO₃ demonstrates the highest extraction efficiency within this range, reaching over 90 wt.%. Beyond 800 W, the yield of bitumen extraction approaches a plateau for most alkaline reagents with the extraction rates of around 95–98 wt.%. On the contrary, pure water shows a slower and less efficient bitumen recovery, with noticeable increases only occurring above 1000 W and reaching a maximum of approximately 80 wt.% at 1500 W. Among the alkaline reagents, Na₂SiO₃ and Na₂CO₃ demonstrate the best extraction performance at the highest ultrasonic powers, closely followed by NaOH and KOH. KOH shows a slightly lower extraction efficiency compared to NaOH, Na₂CO₃, and Na₂SiO₃ but still significantly outperforms pure water. These results suggest that increasing ultrasonic power enhances cavitation effects and improves the separation of bitumen from the mineral matrix. Furthermore, the choice of alkaline reagent optimizes this process, likely due to specific interactions that facilitate bitumen detachment and dispersion.

3.2. The Influence of the Concentration of Alkaline Solutions on Bitumen Extraction

Table 1. Bitumen yield on sodium hydroxide concentration.

Particle Size of Bituminous Sands, mm	Concentration of NaOH Solution, wt.%
	0.5	1	2	3	5
	Bitumen yield, wt.%
1.0	85	75	75	75	75
2.5	96	98	98	98	98
5.0	35	75	78	78	81
10.0	8	10	15	17	20

presents the results of studying the impact of solution concentration and bituminous sand particle size on bitumen extraction rate.

The optimal concentration of NaOH solution was found to be 1 wt.%, and the optimal particle size of bituminous sand was 2.5 mm. Grinding bituminous sand particles down to 1 mm resulted in decreased bitumen extraction efficiency. This may be due to the further particle size reduction caused by high ultrasound power, which leads to intense mixing and the re-agglomeration of extracted bitumen with fine mineral particles. A similar trend was observed for KOH solutions. In contrast, salt solutions exhibited a different behavior: an increase in the concentration resulted in higher extraction degrees. The optimal concentrations for sodium carbonate and sodium silicate solutions were determined to be 12 wt.%.

3.3. The Influence of the Bituminous Sand/Solution Ratio on the Bitumen Extraction

Bitumen extraction from bituminous sand was carried out at different sand-to-solution ratios ranging from 1:1 to 1:5. At ratios of 1:1 and 1:1.5, bitumen separation proved to be difficult. When the ratio increases beyond 1:2.5, the degree of bitumen extraction decreases due to the dissipation of ultrasonic energy throughout the larger volume, resulting in reduced effective power. Therefore, the optimal sand-to-solution ratio was determined to be 1:2 (Figure 4).

3.4. The Influence of the Temperature on the Bitumen Extraction

Table 2. The impact of solution temperature on bitumen extraction rate during ultrasonic processing.

Temperature (°C)	Extraction Rate of Bitumen from the Beke Deposit (%)
	NaOH Solution	KOH Solution
5	80	80
15	82	88
25	84	90
50	86	90
75	98	98
90	87	94

shows the extraction rate of natural bitumen from bituminous sands by NaOH and KOH solutions at different temperatures.

As shown in Table 2, increasing the solution temperature to 75 °C leads to a rise in bitumen yield. However, when the temperature increases to 90 °C, the degree of bitumen extraction decreases. This effect may be explained by the molten state of bitumen particles at higher temperatures, which promotes agglomeration of the extracted bitumen with fine mineral sand particles. During the experiments, a rise in the solution temperature was observed due to ultrasonic processing of bituminous sands.

3.5. The Influence of Ultrasonic Irradiation Time

Table 3. The influence of ultrasonic irradiation time.

Extraction Time (min)	Extraction Rate of Bitumen from the Beke Deposit (%)
	Pure Water	NaOH Solution	KOH Solution
2	0	5	6
4	5	20	20
6	10	75	80
8	40	98	98
20	80	-	-

presents the dependence of bitumen extraction degree from bituminous sands on exposure time to ultrasound at the optimal alkali concentration (1 wt.%).

Bitumen extraction using pure water results in a relatively low yield, with 80% of bitumen extracted after 20 min. On the contrary, potassium and sodium hydroxide solutions enable the extraction of up to 98% of bitumen within 8 min. This improvement is connected with the ultrasonic formation of microcracks in the rock, allowing solution cations to penetrate. Sodium and potassium hydroxide ions interact with bitumen molecules; the cations in the solution act as surfactants by attacking bitumen micelles. Strong ionic bonds form between the cations and bitumen that break the polar structure of bituminous sands. The polar organic components of bitumen are then transferred to the aqueous phase and rise to the surface under buoyancy forces. This process requires approximately 8 min of ultrasonic treatment.

3.6. Composition and Properties of Bitumen Extracted Using Ultrasound

Natural bitumen extracted from the Beke deposit bituminous sands using ultrasound is characterized by the following physicochemical properties: density of 997.0 kg/m³, pour point of 18 °C, coking value of 30%, ash content of 0.4 wt.%, sulfur content of 1.5%, and a softening point of 20 °C measured by the Ring and ball method. The needle penetration depth at 0 °C is 17 mm. These characteristics indicate a high degree of bitumen processing, as well as suitable density and thermal resistance.

Tests were conducted to assess the compliance of the natural bitumen with the requirements of the ST RK 1373-2013 standard for “Bitumen and Bitumen Binders. Road Viscous Petroleum Bitumen. Technical Specifications” (

Table 4. Physicochemical characteristics of natural bitumen extracted from bituminous sands.

Indicators	Regulatory Documents on Test Methods	Bituminous Sand Bitumen	Bitumen 100/130
Density, kg/m3	[23]	940.1	1030.0
Penetration at 25 °C, 0.1 mm	[24]	133	110
Softening point, °C	[25]	29	44
Ductility at 25 °C, cm	[26]	95	150
Ash content, wt.%	[27]	0.4	3.1
Brittleness temperature, °C	[28]	−13	−24
Mechanical impurities, wt.%	[29]	6.5	2.5
Mass change after heating, %	[30]	2.5	0.5
Bitumen content, wt.%		8–10	–
Asphaltenes, wt.%		11.1	19.8
Oils, wt.%		46.7	48.9
Resins, wt.%		42.2	31.3

).

Natural bitumen extracted from bituminous sands using ultrasound contains a large quantity of mechanical impurities such as clay and sand. The density of the natural bitumen (997.0 kg/m³) is lower compared to the one of grade 100/130 bitumen (1030 kg/m³). The needle penetration value of the natural bitumen (133) was higher than that of the grade 100/130 bitumen (110). The softening point and elasticity of the natural bitumen were lower than the corresponding values for road petroleum bitumen. High ultrasound power causes slight degradation of hydrocarbons in the bitumen composition, which was proved by the component analysis. The oil content in natural bitumen is comparable to that in petroleum bitumen, while the tar content is higher and the asphaltene content is lower. The relatively low brittleness temperature and mass change after heating can be explained by the high content of fractions with boiling points up to 300 °C in the natural bitumen. These results indicate that the use of natural bitumen as road bitumen requires an additional oxidation process.

Using gas–liquid chromatography and chromatograph–mass spectrometry methods, the hydrocarbon composition of natural bitumen from the Beke deposit was identified (

Table 5. Hydrocarbon composition of bitumen.

Hydrocarbons	Contents (wt.%)	Hydrocarbons	Contents (wt.%)
n-Alkanes	68.7	n-Alkyltoluenes	1.9
Cyclohexanes	1.4	Alkylnaphthalenes	0.4
Terpans	20.1	Alkylphenanthrenes	1.1
Sterans	2.4	Naphthenophenanthrenes	0.5
Naphthenomonoarenes	2.3	Dibenzothiophenes	0.2
n-Alkylbenzenes	1.0

). The analysis of the results allows not only characterizing the composition but also drawing conclusions about the mechanisms of geochemical transformations that occurred during catagenesis and diagenesis of the organic matter.

Based on the group composition, bitumen from the Beke deposit was found to consist of 68.7 wt.% n-alkanes, which show the contribution of the paraffinic fraction; 20.1 wt.% terpenes (pentacyclic triterpenoids), which are stable biomarkers and indicate the presence of residues of wax resins and smoloids; and 2.4 wt.% steranes (tetracyclic steroids), which suggest a slight biodegradative effect and a moderate degree of organic matter maturity.

The influence of ultrasound on natural bitumen includes both physical and chemical effects that can enhance its technological properties. Ultrasonic vibrations generate mechanical forces capable of breaking large organic molecules that constitute bitumen, causing their rupture or deformation. This process can reduce bitumen viscosity, which is a key factor that affects its processing and transportation.

Ultrasonic exposure can initiate oxidation or degradation reactions that influence bitumen composition and stability. It is important to take into account that the impact of ultrasound on bitumen depends on the frequency and intensity of the ultrasonic waves, as well as environmental conditions such as temperature and pressure. These effects are caused by the generation of microscopic cavitation bubbles in the liquid, which produce localized heating and mechanical stress, thereby promoting more effective modification of the material’s properties.

The IR spectra (Figure 5) of the extracted bitumen show the presence of aromatic hydrocarbons, naphthenes, normal and iso-paraffins, as well as sulfur- and oxygen-containing heterocompounds. Intense absorption bands at 1036 cm⁻¹, 1377 cm⁻¹, and 1465 cm⁻¹, corresponding to deformation vibrations of CH₂ and CH₃ groups (characteristic of paraffins and cycloparaffins), indicate the degree of branching of paraffin hydrocarbons, evidenced by the absorption intensities at 1377 cm⁻¹ and 1465 cm⁻¹ [31].

The characteristic presence of highly condensed and highly substituted aromatic structures is indicated by absorption bands at 3030, 1600, and 868–746 cm⁻¹, as well as alkyl substituents evidenced by the band at 721 cm⁻¹. Intense absorption bands at 2921, 1477, and 1377 cm⁻¹ show the presence of chain alkyl substituents [24,25]. In the IR spectra of asphaltenes, the absorption bands corresponding to aromatic hydrocarbon structures are more pronounced [32].

In addition, absorption bands in the 2850–2920 cm⁻¹ region, characteristic of alkyl substituents such as methylene (–CH₂–) and methyl (–CH₃) groups, are observed. Bands around 1960 cm⁻¹ indicate the presence of C=C=C allyl groups. Notably, relatively intense bands at approximately 1705 cm⁻¹ correspond to C–O–C and C–OH groups, which are peculiar to carboxyl functionalities [33]. These bands are due to aromatic compounds containing C=O groups, showing a higher degree of oxidation in these bitumen components.

Oxygen-containing compounds are clearly observed in the spectra within the 1100–1300 cm⁻¹ region, while sulfur-containing structures are detected at 1036 cm⁻¹ [34]. In particular, the presence of sulfoxide (S=O) groups in the organic fraction of the Beke deposit is indicated by an absorption band at 1036 cm⁻¹, coinciding with the sulfur-containing structures mentioned above. A relatively high intensity of absorption bands in the ranges 3000–2800 cm⁻¹, 1730–1700 cm⁻¹, and around 1026 cm⁻¹ is peculiar to resinous–asphaltene substances. These bands correspond to vibrations of functional groups such as O–H, N–H, C=O, and S=O, which is explained by the presence of sulfoxide, phenol, carboxylic acids, and carbazole fragments [33,34].

The composition of resins and oils was further characterized by an absorption band at 1660 cm⁻¹, attributed to C–O amide group vibrations.

Thus, the composition of bitumen extracted from the Beke deposit bituminous sands under ultrasonic treatment was determined. The natural bitumen is rich in aromatic compounds, and a high aliphaticity coefficient (A₍₂₉₂₀₎/A₍₁₆₀₀₎) indicates a low content of branched isoalkanes [32,35]. Additionally, a low H/C ratio (<1) suggests a high degree of aromaticity, along with significant concentrations of sulfur-containing heterocomponents present in the asphaltenes and resins.

4. Conclusions

Kazakhstan bituminous sands are oil-wet and differ from the water-wet bituminous sands in Canada. In this case, when air is supplied with heat during extraction, bitumen releases from sand grains and elevates above the solids. This approach was developed for water-based extraction and may not be suitable for oil-wet bituminous sands. Thus, this study focuses on the efficiency of ultrasonic-assisted bitumen extraction from bituminous sands.

Ultrasound-assisted extraction of bitumen from bituminous sands in alkaline solutions has high efficiency. The optimized process parameters cover ultrasound power of 1500 W, a frequency of 22 kHz, alkaline concentration at 1 wt.%, a sand–solution ratio of 1:2, and a temperature of 75 °C. The study aimed at creating an alkaline environment. The selection of alkalis and salts was based on their efficiency in bitumen extraction, as well as their availability and cost-effectiveness.

FTIR and GC–MS analyses proved the presence of aromatic hydrocarbons, paraffinic chains, naphthenes, and sulfur-/oxygen-containing functional groups, indicative of moderate maturity, high aromaticity, and complex heteroatomic structures in the bitumen. Despite this, the rheological properties (e.g., softening point of 29 °C and penetration of 133 at 25 °C) suggest that the extracted binder is too soft for road construction and requires further upgrading by oxidation.