Investigation of Solubility Behavior, Data Correlations and Thermodynamic Study of Succinic Acid in Water + Methanol Mixtures at Various Temperatures

Introduction

With the chemical formula C₄H₆O₄, succinic acid (SA) is a dicarboxylic acid that is also known as butanedioic acid or amber acid. It is used as a precursor in the synthesis of several fine and bulk compounds, such as vitamins, antibiotics, medications, and biodegradable polymers like polyamides and polybutyrate succinate, as well as food additives, ion chelators, and surfactants^1-5. Studies on the solubility of succinic acid in a variety of organic solvents, including isopropanol⁶, water + methanol and water + ethanol mixtures⁷, binary mixtures of cyclohexanone, cyclohexanol, and cyclohexane⁸, binary mixtures of methanol, ethanol, and propanol⁹, and fumaric acid’s solubility in n-propanol, isopropanol, ethanol, and acetone¹⁰, are all reported in the literature. With the use of a gravimetric technique, the solubility of succinic acid in water, methanol, and water + methanol binary solvent was investigated at temperatures between 305.15 and 313.15 K in the local environment. Apelblat and van der Hoff equations are two examples of thermodynamic models with which obtained experimental solubilities have been related. Furthermore, the van der Hoff equation has been used to evaluate the energies of solution in order to obtain a better understanding of the phenomena of the succinic acid dissolving process.

Materials and Methods

Triple-distilled water was employed in these studies. MERCK provided 99.5% pure succinic acid, whereas Jiangyin Huaxi International Trade Co. (China) provided 99.9% pure methanol. The equipment and procedures utilized to determine solubility have previously been thoroughly discussed^11–13.

In this experiment, a specifically built 100 mL double jacketed flask was used to generate binary solvent mixtures by weight (Shimadzu, Auxzzo) with an uncertainty of ± 0.1 mg. An excess of succinic acid was added to the mixes. Water was pumped between the flask’s inner and outer sides at a steady temperature.

A thermostat was used to regulate the water’s temperature, keeping it within (±0.1) K. In order to ensure equilibrium, the solution was constantly stirred with a magnetic stirrer for a duration of about one hour. Following this, the solution was allowed to stand for one hour. The supernatant liquid was then taken out of the flask and placed in a weighing container in a predetermined quantity using a pipette that is hotter than the solution. This sample was weighed, and it was then maintained at 343 K in an oven until all of the solvent had evaporated. Weighing twice or three times to get a consistent weight allowed us to confirm this.

Weight of solution and solute have been used to calculate solubility. Every solubility value measured is the mean of at least three experiments.

Using standard Eqs. 1 and 2, the saturated mole fraction solubility (X_b), starting methanol mole fraction (X_C⁰), and initial water mole fraction (X_A⁰) were determined.

X_b = (m_b / M_b) / (m_b / M_b + m_A / M_A + m_C / M_C)                                                                    (1)

 X_C⁰= (m_C / M_C) / (m_A / M_A + m_C / M_C) and  X_A⁰= (m_A / M_A) / (m_A / M_A + m_C / M_C)               (2)

In this case, the molecular weights of the solute, water, and methanol are represented by the letters M_b, M_A, and M_C respectively, while the masses of the solute, water, and methanol are denoted by the letters m_b, m_A, and m_C.

Results and Discussion

Table 1 lists the solubility values (X_b) of SA in pure water and methanol between 305.15 and 313.15 K, and Figure 1 illustrates how these values change with temperature. It has been noted that temperature has a direct correlation with SA’s solubility in pure solvents. In water + methanol solvent mixes at T = 305.15 to 313.15 K, Table 2 displays the mole fraction solubilities of SA along with the solubilities that were estimated using corresponding models. Figures 2 and 3, respectively, illustrate the solubility of SA in binary solvent mixtures as a function of temperature and the initial mole fraction of solvent.

Table 1: Experimental of mole fraction solubility (X_b) of SA in pure water & methanol at T= (305.15 -313.15 K).

Figure 1: Mole fraction solubility (Xb) variation with temperatures for water (♦), methanol (■). Click here to View Figure

It is evident that when temperature rises, SA becomes more soluble in all binary solvent mixes. Additionally, when the initial mole fraction of methanol increases, so does SA’s solubility in the water + methanol mixture.

Figure 2: Mole fraction solubility (Xb) variation with Initial mole fraction ( of methanol, at various temperatures (◆T=305.15 K, ■T=308.15 K; ▲T=310.15 K; ×T=313.15 K) Click here to View Figure

Figure 3: Mole fraction solubility (Xb) variation with temperature at initial mole fraction ( of methanol (◆ = wt. fraction 0.0; ■ = 0.1; ▲= 0.2; × = 0.3; × = 0.4; ● = 0.5; + = 0.6; – = 0.7; ▬ = 0.8 and ◇ = 0.9; □ =1). Click here to View Figure

Apelblat^14-15 and the van’t Hoff model¹⁶ are used to link the observed X_b values of SA with temperature. Table 2 provide the computed values of SA in binary solvents for X_b^Apel and X_b^van’t. It is discovered that there is relatively little variation between the calculated and experimental solubilities of these three models. In terms of correlation coefficient (R²) values, the X_b values of SA are correlated with the X_b^Apel and X_b^van’t values of SA in all binary solvents.

Table 2: Experimental (X_b) and calculated mole fraction solubility of SA in various initial mole fraction X_C⁰ of methanol at T= 305.15 to 313.15 K

The correlation coefficient (R²) values are nearly equal to one. Based on the Apelblat Model and van’t Hoff model, the estimated solubility and the measured mole fraction solubility show extremely high agreement in these results. As a result, the solubility data fits the van der Hoff equation and the Apelblat Model extremely well. Table 3 and 4 presents the values of the parameters derived from the van der Hoff equation and the Apelblat model, together with R². The correlation coefficient data (R² ≈ 1) show a strong relationship between the experimental mole fraction solubility, the Apelblat Model, and the van der Hoff model.

Table 3: Model parameters and correlation coefficient of the Apelblat equation.

Table 4: Model parameters and correlation coefficient of the Van’t Hoff equation.

The thermodynamic study of solubility of SA is carried out in order to evaluate dissolution pattern of SA in pure as well as binary solvent combinations. Thermodynamic parameters (∆H⁰_soln,∆S⁰_soln, ΔG⁰_soln) of dissolution are calculated for this purpose. Using Eq., the ∆H⁰_soln values at the mean harmonic temperature (T_hm) of 309.15 K are calculated using van’t Hoff analysis^17,18.       

Table 5 displays the values of ΔG⁰soln, ∆H⁰_soln, and ∆S⁰_soln, for the SA dissolution in water + methanol. The findings indicate that when the initial mole fraction of alcohols increases, the, ∆H⁰_soln values for SA dissolution in all mixes decrease. Every mixture’s SA dissolving process is endothermic, as indicated by the positive ∆H⁰_soln values. In pure water, the value of ∆H⁰_soln is 32.69 kJK^-1mol^-1, whereas in methanol, it is 15.80 kJK^-1mol^-1. This shows that dissolving SA in water takes more energy than dissolving it in methanol. The total organic acid solubility and the Gibbs free energy data show a similar trend: the greater the solubility values, the lower the Gibbs free energy.

Table 5: Thermodynamic parameters relative to solution process of SA at T_hm= 309.15K

Conclusion

The mole fraction solubility of succinic acid (SA), a significant industrial chemical, in pure and binary solvent mixtures has been experimentally evaluated within the temperature range of 303.15 to 313.15K. Investigations are done on the impact of temperature and solvent composition. It has been noted that solubility constantly rises with temperature, indicating that all solvent mixes have a positive dissolving enthalpy.

As the initial mole fraction of methanol increases, so does SA’s solubility in the water + methanol combination. Using the Apelblat and van der Hoff models, the experimental solubility values of SA are extremely strongly associated with temperature. Thermodynamic characteristics demonstrate that the SA dissolving process is endothermic.

Acknowledgement

The author is thankful to Principal of MSG Arts, Science and Commerce College Malegaon for providing laboratory facilities. The authors also express their sincere thanks to Dr Apoorva Hiray (Co-ordinator M.G. Vidyamandir Malegaon).

Funding Sources

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Conflict of Interest

The authors do not have any conflict of interest.

Data Availability Statement

This statement does not apply to this article

Ethics Statement

This research did not involve human participants, animal subjects, or any material that requires ethical approval.

Informed Consent Statement

This study did not involve human participants, and therefore, informed consent was not required

Authors’ Contribution

The sole author was responsible for the conceptualization, methodology, data collection, analysis, writing, and final approval of the manuscript

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