The physicochemical properties and distribution in the system NaBO 2в€’H 2O were presented, and the distributions for boron species in the mixed system Na 2SO 4вЂ“NaBO 2вЂ“H 2O at 298.15вЂ‰K were also calculated with the Pitzer model. NaBO 2 is an important boron compound, especially in the industrial production of NaBH 4, and it is a promising hydrogen solid carrier due to its easy hydrolysis and adjustable hydrogen release. At present, there are relatively few studies on the distribution of chemical species in the solution of multiple systems. The total boron concentration, pH value, metal cations, and temperature in the medium all affect the existence form and equilibrium relationship of borate anions, among which the total boron concentration and pH value are particularly important. Although the calculation may not be correct, the calculated results can also describe the distribution of boron species in the solution. The concentration of boron species was calculated in references, and it was considered that the activity coefficients of all boron ions were 1.0. The calculated results in these literatures are in agreement with those with the Pitzer model in the systems NaBO 2в€’H 2O and K 2B 4O 7в€’H 2O. With the pH values in the solution and equilibrium constant between different boron species, the distribution of boron species was calculated. Д«oron form depends on boron concentration, pH, temperature, and ionic strength. The calculated results for distribution of boron species in the system KClв€’K 2SO 4в€’K 2B 4O 7в€’H 2O at 298.15вЂ‰K show that the mole fraction of the boron species is mainly affected by the concentration of boron but no other anions in the solution. The preponderant boron species is B(OH) 4 в€’, whose mole fraction is more than 0.95. The distributions of boron species in the system NaClв€’NaSO 4в€’NaBO 2в€’H 2O were also calculated in our previous work. The main boron species in the mixed borate solution are B(OH) 4 вЂ’ and B 4O 5(OH) 4 2вЂ’. In the quaternary system NaClв€’NaBO 2в€’Na 2B 4O 7в€’H 2O at 298.15вЂ‰K, the distributions of boron species in the liquid phase were calculated with the Pitzer model. The concentrations of various boron species in different aqueous borate solution can be calculated theoretically by the Pitzer model. The behavior of borate solution extremely complicated, and it can exist in several different species in aqueous solution, such as metaborate B(OH) 4 в€’, B 2O(OH) 6 2в€’, B 3O 3(OH) 4 в€’, B 4O 5(OH) 4 2в€’, B 5O 6(OH) 4 в€’, and B 6O 7(OH) 6 2в€’. Aqueous boron species can be found in natural waters, including seawater, salt lakes, oilfield brine, and hydrothermal fluids. Therefore, it is urgent to solve the problem of developing liquid boron resources in western China as soon as possible. In the last century, high-quality solid boron deposits were almost depleted. In chemical engineering, the formation conditions and transformation rules of borate and hydrated borate crystals were expounded, and borate minerals were comprehensively developed and utilized to select the optimal extraction process. Borates are gaining more and more attention, and global demand for boron will continue to grow over time. With the continuous development of social progress and high-tech, borates are widely used in glass production, agricultural and sideline products, and pharmaceuticals, and the application of boron-containing compounds is in aerospace and defense construction. Boron is usually distributed in liquid brine boron deposits and solid borate deposits.

The Qaidam Basin in Qinghai Province is rich in boron resources. The results of distribution for boron species in this study and those with the Pitzer model can both be used to describe the distribution of boron species in the mixed solution. The polyborate ions are easier to form as the temperature increases. The mole fraction of B(OH) 3, B 5O 6(OH) 4 вЂ’, and B 3O 3(OH) 4 вЂ’ can be neglected. The dominant boron species in the mixed solution at the two temperatures is B(OH) 4 вЂ’.

The molar fractions of the six boron species are mainly affected by the total boron concentration and temperature, but rarely affected by the concentration of SO 4 2вЂ“.

Combining the equilibrium constants for different boron species, the distributions of six boron species in the mixed solution were calculated with total boron concentration and pH values. The densities and pH values in the system NaBO 2вЂ“Na 2SO 4вЂ“H 2O at 298.15вЂ‰K and 323.15вЂ‰K were investigated.

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