PHASE COMPOSITION OF FEED MONOCALCIUM PHOSPHATE PRODUCED FROM THE TREATMENT OF BONE MEAL WITH WET- PROCESS PHOSPHORIC ACID DERIVED FROM CENTRAL KYZYLKUM PHOSPHORITES

ABSTRACT

This study investigates the production of feed-grade monocalcium phosphate from desulfated and concentrated wet-process phosphoric acid (WPA) derived from Central Kyzylkum phosphorites and bone meal. The importance of feed phosphates in animal nutrition and the current state of their production are briefly considered. The synthesis of monocalcium phosphate was carried out under varying phosphoric acid concentrations, and the influence of process parameters was evaluated in a recycle mode system.

The interaction between evaporated WPA and bone meal was studied to determine optimal conditions for monocalcium phosphate formation. X-ray diffraction analysis confirmed the formation of a crystalline phosphate phase in the obtained product. Optimal synthesis conditions were identified using phosphoric acid with a concentration of approximately 40.46% P₂O₅, an acid excess of 105%, and a recirculation ratio of 1:0.5. The resulting product demonstrates a stable composition and high purity suitable for feed phosphate applications.

АННОТАЦИЯ

В работе исследуется процесс получения кормового монокальцийфосфата из десульфатированной и концентрированной влажной фосфорной кислоты (WPA), полученной на основе обожжённого концентрата Центрально-Кызылкумских фосфоритов, а также костной муки. Рассматривается значение кормовых фосфатов в животноводстве и кратко описывается современное состояние их производства. Синтез монокальцийфосфата осуществлялся при различных концентрациях фосфорной кислоты в режиме рециркуляции, а влияние технологических параметров оценивалось экспериментально.

Изучено взаимодействие упаренной WPA с костной мукой с целью определения оптимальных условий образования монокальцийфосфата. Методом рентгенофазового анализа подтверждено формирование кристаллической фосфатной фазы в полученном продукте. Оптимальные условия синтеза установлены при использовании фосфорной кислоты с содержанием около 40,46% P₂O₅, избытке кислоты 105% и коэффициенте рециркуляции 1:0,5. Полученный продукт характеризуется стабильным составом и высокой чистотой, пригодной для использования в качестве кормового фосфата.

Keywords: bone meal, wet-process phosphoric acid, retur, monocalcium phosphate, chemical composition.

Ключевые слова: костная мука, экстракционная фосфорная кислота, ретур, монокальцийфосфат, химический состав.

Introduction

Livestock farming is one of the main branches of agriculture in Uzbekistan. It contributes to food security, improved nutrition, poverty reduction and economic growth. To enhance food security through increased livestock production, several key initiatives have been introduced, including the widespread adoption of modern production techniques, the creation of value-added chains, and the development of cooperative relationships. State support for the livestock sector, alongside efforts to expand the feed base, has been a priority. This includes encouraging livestock raising by households in cooperation with large farms and processors, as well as addressing the demand for feed resources. Furthermore, there has been a focus on integrating modern information and communication technologies, as well as scientific advancements, into livestock farming. To support these efforts, several resolutions by the President of the Republic of Uzbekistan have been adopted [1, 2].

The development of livestock farming, poultry farming, fisheries, and other meat production sectors remains a top priority. As a result, the demand for feed phosphates continues to grow. To meet this increasing need, efforts are focused on maximizing the use of available raw materials and exploring technologies for producing feed phosphates through the processing of animal bones and phosphate materials. Intensive research and development in this field are underway to enhance production efficiency and meet the rising demand for high-quality feed phosphates.

Feed phosphate production can be classified into distinct categories based on the type of phosphate raw materials employed.

The production of feed phosphates involves several key processes:

- Processing of animal bones (bone meal): Utilizing animal bones as a raw material for phosphate extraction.

- Elemental phosphorus production: Derived from phosphoric acid solutions obtained via the "thermal" method, where water absorption plays a key role.

- Phosphoric acid production: Based on the extraction of phosphate raw materials using sulfuric acid.

- Mineral fertilizer production: Includes the synthesis of various phosphate-based fertilizers, such as calcium, ammonium, and sodium phosphates.

The bioavailability of phosphorus in feed phosphates for animals is influenced by numerous factors, including the phosphorus (P) content, the calcium-to-phosphorus (Ca:P) ratio, pH level, particle size, solubility, chemical bonding, and the presence of harmful elements. Equally important is the chemical structure of different phosphate types.

Bone meal is a mineral feed derived from the bones of slaughtered animals through processes of degreasing and steam refining. It is a natural product rich in essential nutrients, serving as a source of amino acids, high-quality protein, phosphorus, carnitine, serotonin, and easily digestible fats. This nutrient-dense composition significantly enhances the nutritional value of feed, leading to notable benefits in animals, such as accelerated growth and balanced development in young livestock, along with improved immune function. And along with this, the productivity and efficiency of the enterprise grows. Bone meal is rich in minerals, especially calcium (245 g per 1 kg) and phosphorus (118 g per 1 kg) [3, 4]. It is mainly added to compound feed, silage, concentrated feed and mixed with crushed root crops. It is also recommended to feed bone meal to fish and fur animals. Dairy cows 60-200 g per day, calves (up to 1 year) 1540 g, sheep 35 g, poultry (chickens, ducks, geese, turkeys) 3-10 g. Bone meal is added to compound feed in the amount of 1% of the feed weight [5]. The objective of this study is to explore the process of producing water-soluble granular monocalcium phosphate through the chemical treatment of bone meal using thermal phosphoric acid. The focus is on optimizing the reaction conditions to maximize yield and quality, contributing to the development of efficient feed phosphate production methods.

Objects and methods of research

The primary raw materials utilized in this study were wet-process phosphoric acid (WPA) and bone meal. The bone meal was subjected to thermal treatment at 800°C to achieve calcination, resulting in a composition of 41.02% P₂O₅ and 50.68% CaO. Tricalcium phosphate was identified as the predominant component of the calcined material.

To evaluate the mineralogical phases and crystalline structure of the calcined bone meal, X-ray diffraction (XRD) analysis was performed. For the decomposition process, WPA was diluted with distilled water to prepare phosphorus solutions with concentrations of 34.83, 40.46, 46.01, 50.55, 55.65, and 59.41% P₂O_5.

The chemical interaction between the tricalcium phosphate in bone meal and the phosphoric acid was conducted to synthesize monocalcium phosphate according to the following stoichiometric equation:

Са₃(РО₄)₂ + 4Н₃РО₄ → 3Са(Н₂РО₄)₂

The synthesis was carried out using varying acid application rates of 80, 85, 90, 95, 100, 105, and 110% of the theoretical requirement for MCP formation.

The laboratory experiments were conducted using a porcelain vessel integrated with a thermostat to ensure precise temperature control throughout the synthesis process. Initially, the wet-process phosphoric acid (WPA) solution, characterized by a concentration of 40.46% P₂O₅, was preheated to 80°C and maintained at this temperature for 15 minutes to reach thermal equilibrium. Subsequently, a calculated quantity of calcined bone meal was introduced incrementally to the preheated acid under continuous stirring for 20 minutes, ensuring the formation of a homogeneous reaction mixture. The resulting wet mass underwent granulation via a rolling and stirring process, where a recycle (return) mode using fine product particles (less than 1 mm) was employed to optimize granule formation. During this stage, three distinct Product:Recycle mass ratios - 1:0.3, 1:0.5, and 1:0.7 - were systematically investigated to evaluate their impact on the commercial product yield. Upon completion of the granulation, the synthesized monocalcium phosphate (MCP) granules were dried in a controlled environment at 95-100°C for a duration of 3 hours.

The data indicate that as the concentration of 40.46% WPA increased from 80% to 105%, the digestible form of P₂O₅ in the recycled product rose from 48.73% to 51.19%. According to the GOST 23999-80 standard, regarding the content of digestible forms of phosphorus and calcium, these products meet the criteria for 2nd-grade MCP [6, 7]. These products subsequently functioned as recycled material for further granulation - classified as fine or small product.

The quality, stability, and physicochemical properties of the final granulated product were assessed through several standardized analytical techniques. The chemical composition, including the concentration of various forms of P₂O₅, CaO, MgO, and F, was determined using established analytical methods prevalent in the phosphorus industry. Specifically, the assimilable forms of P₂O₅ and CaO were quantified based on their solubility in a 0.4% hydrochloric acid (HCl) solution. The acidity of the final product was evaluated by measuring the pH value of a 10% aqueous solution using a METTLER TOLEDO FE20/EL20 potentiometric device. Furthermore, the mechanical integrity of the product was verified by assessing the static strength of the granules with a MIP-1 device, following the specialized methodology developed by the Research Institute of Fertilizers and Phytosanitary [8-9].

Results and discussion

The X-ray diffraction (XRD) patterns of bone meal calcined at 800°C are shown in Figure 1. These patterns reveal the crystalline structure of the bone meal after thermal treatment, providing key information on the phases present and confirming the composition of the calcined material. This analysis helps in understanding the transformations that occur during the calcination process, which is essential for optimizing the subsequent chemical reactions with phosphoric acid.

Figure 1. The XRD patterns of bone meal calcined at 800°C

The XRD composition of bone meal calcined at 800°C is detailed in Table 1. This table presents the various crystalline phases identified in the calcined bone meal, providing insights into the mineralogical composition post-treatment. Understanding these phase compositions is crucial for optimizing the chemical processes involved in producing monocalcium phosphate, as the crystalline structure directly influences reactivity and the efficiency of the phosphate production process.

Table 1.

The XRD composition of bone meal calcined at 800°C

For each specified condition, the corresponding product was prepared and used as a return (Table 2). Consequently, the content of the water-soluble form P₂O₅ increases from 39.42 to 42.91%, from 39.45 to 42.95% and 39.55 to 43.03% (Table 2) and the recycling rates are 1:0.3, 1:0.5 and 1:0.7.

Table 2.

Composition of samples of the recycled product monocalcium phosphate depending on the norm and concentration of thermal phosphoric acid

The composition of granulated samples of MCP is given in Table 3.

The data presented in Table 3 demonstrate that at a WPA concentration of 40.46% P₂O₅, with a recirculation ratio of 1:0.3, increasing the application rate from 80% to 110% results in a rise in the digestible P₂O₅ content from 48.79% to 51.25%. Similarly, for a recirculation ratio of 1:0.5, the digestible P₂O₅ content increases from 48.83% to 51.29%, and for 1:0.7, it increases from 48.92% to 51.39%.

Table 3.

Composition of granulated feed monocalcium phosphate samples depending on the extraction phosphoric acid rate and the mass ratio Product:Retur (conc. H₃PO₄ - 40.46% P₂O₅)

The second-grade monocalcium phosphate (MCP) produced under laboratory conditions, with the specified concentrations of digestible and water-soluble forms of P₂O₅, is regarded as a high-quality and efficient product. It is suitable for use as a phosphate supplement in the diets of cattle, poultry, and fish feed, contributing to enhanced nutritional value and overall productivity in animal husbandry.

The interaction of bone meal with WPA concentrations of 34.83%, 46.01%, 50.55%, 55.65%, and 59.41%, combined with recycle ratios of 1:0.3, 1:0.5, and 1:0.7, follows a consistent pattern. The only variations observed lie in the absolute values of the components within the products. The difference between the digestible and water-soluble forms of P₂O₅ indicates the dicalcium phosphate content present in the final product.

Also, the process of interaction of bone meal with WPA at concentrations of 34.83; 46.01; 50.55; 55.65 and 59.41% P₂O₅ and a recirculation ratio of 1:0.3, 1:0.5 and 1:0.7 takes a lot of time (from 1 to 3 hours), which is due to energy costs. In this context, the decomposition time of bone meal using WPA with a concentration of 40.46% P₂O₅ is 20 minutes at a recycle ratio of 1:0.7. This duration proves to be more favorable for the technological process. Consequently, WPA with a concentration of 40.46% P₂O₅ is considered optimal for achieving efficient decomposition and desired outcomes in the process.

The products contain a significant amount of digestible and water-soluble forms of CaO. This component is essential for the formation of bone tissue of any type of living organism. About 99% of calcium reserves in the body are in the bone tissue of an animal [10-13]. With sufficient intake of calcium and phosphorus with food, with the correct ratio (1.5-2:1) and normal absorption, their content in the bones is stable and practically does not change.

At the studied acid rates (80-110%) and recirculation ratios (1:0.3-0.7) using the concentration of WPA – 40.46% P₂O₅, the resulting feed products have 23.28-26.55% CaO_total, 23.07-26.39% CaO_dig. and 15.01-16.55% CaO_wat. Additionally, all products exhibit a magnesium oxide (MgO) content ranging from 0.18% to 0.25%. Magnesium, alongside calcium, sodium, and potassium, is one of the four most essential minerals in the body. Within cells, magnesium ranks second only to potassium in terms of abundance, playing a crucial role in numerous biochemical processes and contributing to overall mineral balance [14].

The products obtained at phosphoric acid (H₃PO₄) standards ranging from 80% to 110%, in terms of phosphorus content, comply with the specifications outlined in GOST 23999-80 for second-grade monocalcium phosphate. This standard ensures that the phosphorus levels meet the required benchmarks, making the products suitable for use as feed supplements in animal nutrition. Thus, with a recycle ratio of 1:0.3-0.7 and a phosphoric acid concentration of 40.46% P₂O₅, the resulting products contain 48.79-51.39% P₂O_5dig., 39.42-43.03% P₂O_5wat., 23.28-26.55% CaO_dig., 23.07-26.39% CaO_wat., 0.18-0.25% MgO. But most importantly, all products have a minimum F content – ​​less than 0.18% (should be no more than 0.2%).

Additionally, it is important to highlight the investigation of the X-ray diffraction (XRD) patterns of monocalcium phosphate obtained from the reaction between bone meal and wet-process phosphoric acid (WPA). The XRD results, which are presented in Figures 2, provide valuable insights into the phase composition and crystallographic structure of the resulting product.

Figure 2. The XRD patterns of monocalcium phosphate obtained from the reaction between bone meal and WPA

The results of the XRD analysis are presented in Table 4, offering detailed insights into the crystalline phases present in the monocalcium phosphate obtained from the reaction between bone meal and WPA. These data are crucial for understanding the structural composition and quality of the product.

Table 4.

Substances in the XRD indicator of monocalcium phosphate

Conclusion

The study has demonstrated the fundamental feasibility of producing feed-grade monocalcium phosphate by processing calcined cattle bone meal with extraction phosphoric acid in the presence of a recycled product. The decomposition of bone meal and granulation of the reaction mass were effectively carried out in a single-stage process within a single apparatus. The resulting products exhibit high phosphorus and calcium content, which positively influences animal productivity. Monocalcium phosphate produced using 80-110% of the phosphoric acid standard meets the criteria for a second-grade product, in accordance with industry standards.

References:

1. Resolution of the President of the Republic of Uzbekistan dated 08.02.2022 No. PP-120. “On approval of the Program for the development of the livestock sector and its branches in the Republic of Uzbekistan for 2022-2026” [Electronic resource]. URL: https://lex.uz/ru/docs/5858730
2. Resolution of the President of the Republic of Uzbekistan dated 08.02.2022 No. PP-121 “On measures for the further development of animal husbandry and strengthening the feed base” [Electronic resource]. URL: https://lex.uz/ru/docs/5851477
3. Degtyarev V. Efficiency of monocalcium phosphate in animal feeding. // Dairy and beef cattle breeding. 2003. 2. - P. 7-10.
4. Litusova N.M. Technology of obtaining feed calcium phosphates in granulated form based on chalk and extraction phosphoric acid: Diss. … Cand. of Technical Sciences. - Moscow, 2004. - P. 136.
5. John J. Mcketta., William A.  Phosphoric acid and phosphates. // Encyclopedia of chemical processing and design: Vol. 35. P. 478-489.
6. Calcium phosphate feed. GOST 23999-80. – P. 9.
7. Khoshimov, I. E. U., Turdialieva, Sh. I., Namazov, Sh. S., Seitnazarov, A. R., & Turdialiev, U. M. (2024). Feed monocalcium phosphate based on bone meal treatment with thermal phosphoric acid. Universum: technical sciences, 3(8 (125)), P. 61-68.
8. Vinnik M.M., L.N. Erbanova, P.M. Zaitsev, et al. Methods of analysis of phosphate raw materials, phosphorus and complex fertilizers, feed phosphates. – M/: Chemistry, 1975. – P. 218.
9. GOST 24596.5-81. Feed phosphates. Method for determination of pH of solution or suspension. – M.: IPK Publishing House of Standards, 2004. - P. 2.
10. Khoshimov I, Turdialieva SH, Namazov SH, Karshiev B, Seytnazarov A, Rajabov R. Production of feed calcium phosphates based on Kyzylkum evaporated extraction phosphoric acid and lime raw materials. Uzbek Chemical Journal/O'Zbekiston Kimyo Jurnali. 2024 May 1;1(3).
11. Khoshimov I. Е., Turdialieva, S. I., Seytnazarov, A. R., Namazov, S. S., & Rifky, M. (2024). Investigation of Vapor Pressure and Infrared Spectroscopic Analysis of Phosphoric Acid Extract Evaporation after Desulfation with SrCO₃. EURASIAN JOURNAL OF CHEMISTRY, 29(4 (116), 82–91. https://doi.org/10.31489/2959-0663/4-24-4
12. Turdialieva, S., Khoshimov, I., Seytnazarov, A., Namazov, S., Kholmurodov, J., Nomozov, S., ... Valeeva, N. (2025). Producing Feed Ca(H2PO4)2 based on Animal Bone Meal and Wet-Process Phosphoric Acid. New Materials, Compounds and Applications, 9(2), 326-338. https://doi.org/10.62476/nmca.92326
13. Khoshimov, I. E. U., Turdialieva, S. I., Seytnazarov, A. R., & Namazov, S. S. (2025). Concentration of wet process phosphoric acid from washed thermo concentrate of phosphorites Central Kyzylkum and its rheological properties. Journal of Chemical Technology and Metallurgy, 60(2), 207–214. https://doi.org/10.59957/jctm.v60.i2.2025.2
14. Gurtsieva D.A., Neyolova O.V. Biological role of magnesium and application of its compounds in medicine // Advances in modern natural science. – 2014. – No. 8 - P. 165-166.