Solubility and metastable zone width measurement of 2,4-diaminobenzenesulfonic acid in (H2SO4+H2O) system

Fanfan Shen,Lizhen Chen,Pengbao Lian,Jianlong Wang,Duanlin Cao

School of Chemical Engineering and Technology,North University of China,Taiyuan 030051,China

Keywords:2,4-Diaminobenzenesulfonic acid Solubility Correlation Metastable zone width

ABSTRACT The equilibrium solubility of 2,4-diaminobenzenesulfonic acid and super solubility as well as metastable zone width were measured in(H2SO4+H2O)system by the laser dynamic method at elevate temperature range from 298.15 K to 338.15 K.2,4-Diaminobenzenesulfonic acid solubility dependence on the temperature and solvent composition were correlated by the modified Apelblat equation,(CNIBS)/Redlich-Kister model and Jouyban-Acree model.The correlated results by three correlation models were in good accord with the experimental values according to relative average deviations(RD),root-mean-square deviations(RMSD),and correlation coefficients(R2).The metastable zone width increased with temperature and sulfuric acid content.The dissolution enthalpy,dissolution entropy and the Gibbs energy were calculated from the experimental values,which indicated that dissolution process of the 2,4-diaminobenzenesulfonic acid was endothermic.The solubility and calculation models of 2,4-diaminobenzenesulfonic acid in (sulfuric acid+water) system could provide the basic data to the crystallization and purifying of the 2,4-diaminobenzenesulfonic acid.

1.Introduction

2,4-Diaminobenzenesulfonic acid (CAS No.88-63-1) is a valuable intermediate in dyes synthesis and producing water-based varnishes and novel reactive blue dye [1].The industrial 2,4-diaminobenzenesulfonic acid is prepared by sulfonation and hydrolysis of the 1,3-diaminobenzene [2] or synthesized by the sulfonation of 2,4-dinitrochlorobenzene followed by reduction using iron powder and hydrochloric acid [3,4].The products synthesis from the former method includes 2,4-diaminobenzenesulfonic acid,2,4-diaminobenzenedisulfonic acid in some proportions and 1,3-diaminobenzene.It is not easy to isolate the products from the mixture.High purity and quality of 2,4-diaminobenzenesulfonic acid can be gainedviasolvent crystallization.So,It is necessary to investigate the solubility of 2,4-diaminobenzenesulfonic acid in sulfuric acid and water.

In general,crystallization referring to multiphase heat and mass transfer process can improve the various physical-chemical characteristics of the substance,such as shape and size,chemical purity and stability [5].The purity of the 2,4-diaminobenzenesulfonic acid is crucial factor for the dye production and the appliance.The solubility of sodium 2,4-diaminobenzenesulfonic acid in binary NaCl+H2O,Na2SO4+H2O,and C2H5OH+H2O solvent mixtures[6]and in liquid mixtures (methanol+water,isopropanol+water,and 1,2-propane diol+water) [7] were measured by a steady-state method.Up to now,no literature has been reported on the solubility of the 2,4-diaminobenzenesulfonic acid in (H2SO4+H2O) system.

In this work,the solubility and the metastable zone [8–10] of 2,4-diaminobenzenesulfonic acid in (H2SO4+H2O) system were determined at temperatures ranging from 298.15 K to 338.15 K under atmospheric pressure by the dynamic laser monitoring method. The experimental solubility data of 2,4-diaminobenzenesulfonic acid were correlated with three thermodynamic models of the modified Apelblat equation,CNIBS/Redlich-Kister equation and Jouyban-Acree model.Crystallization thermodynamics provided basic data for studying the crystallization process and the kinetics of 2,4-diaminobenzenesulfonic acid in (H2SO4+H2O) system.

2.Experimental

2.1.Materials and apparatus

2,4-Diaminobenzenesulfonic acid with a mass purity of 0.995 was supplied by Beijing coupling technology Co.,Ltd.,China.The final mass fraction purity of the 2,4-diaminobenzenesulfonic acid was identified by HPLC and was greater than 99% (Fig.1).

Fig.1.HPLC analysis of 2,4-diaminobenzenesulfonic acid.

Fig.2.Experimental setup of solubility measurement.1-laser generator;2-crystallizer;3-condenser pipe;4-burette;5-mercury thermometer;6-digital display;7-thermostatic bath;8-photoelectric switch;9-mercury thermometer.

The solubility of 2,4-diaminobenzenesulfonic acid in different mass fraction of sulfuric acid were determined by laser monitoring system [11] given in Fig.2.The experimental apparatus included the laser transmitter which is used to monitor the transition point of the phase,crystallizer,air condenser,burette,thermometer,optical-to-electrical transducer,constant temperature bath,mechanical agitation.

2.2.Solubility determinations

The laser monitoring system was used to measure phase transition point reported in the work of Lanet al.[12] and Chenet al.[13].Firstly,the experimental was carried in a 100 ml jacketed glass vessel with the magnetic stirrer which was kept in the thermoelectric controller.A mercury thermometer inserted into the suspension to measure the dissolution temperature with accuracy of 0.05 K.A certain amount of solvent was transferred by suction pipette into glass vessel with an accuracy of 0.1 ml.Add a small amount of 2,4-diaminobenzenesulfonic acid with an accuracy of 0.0001 g was add into the solvent frequently and stir for 30 min after each addition.Stop adding the solute and start to add the solvent several times in a small amount when undissolved 2,4-diaminobenzenesulfonic acid particle is view and the laser intensity indicator is obviously reduced,and stir for 30 min after each addition of solvent.When the laser intensity indicator reaches a stable value within 30 min and no longer increases,it is considered that the solute has been completely dissolved.And subsequently adding solvent and solute was recorded.To avoid measurement deviations,each solubility experiment was carried out three times and average values of the measurements would be the experimental value and the absolute standard uncertainty of experimental solubility data was not greater than 0.3%.

Values of the saturated mole solubility of the 2,4-diaminobenzenesulfonic acid is calculated by the Eq.(1),and the initial composition of binary solvents can be calculated by the Eq.(2)

Here,xAis the saturated solution mole fraction solubility of 2,4-diaminobenzenesulfonic acid,mA,represent the mass of solute.m1andm2indicate the mass of the solvent.MA,M1andM2are the molecular weight of the solute and solvent,respectively.wis the mass fraction of the sulfuric acid.

2.3.Powder X-ray diffraction analysis

In order to check whether the substance will change (transformation of crystal form,formation of solvent compounds,reaction,etc.) before and after the solubility measurement,the powder Xray diffraction analysis (PXRD) (Bruker-AXS/D8 ECO,Germany)was performed on the raw material and the equilibrium solid phases obtained from the solubility measurement.After the solubility test of 2,4-diaminobenzenesulfonic acid in different mass fraction of sulfuric acid at temperature ranging from 298.15 to 338.15 K,the system was cooled down to room temperature and the solute were precipitated.Then the equilibrium solid phases could be obtained by vacuum filtering and drying at 80 °C.During the PXRD analysis,Cu Kα radiation(λ=1.54 nm)was used and the tube voltage and current were set at 60 kV and 80 mA,respectively.The data were collected over the diffraction angle(2θ)range of 5°–60° with a scanning rate of 5 (°)?min-1and a step size of 0.02°.

2.4.Metastable zone width determinations

The metastable zone width (MSZW) between the solubility equilibrium curve and super-solubility curve is an essential requirement for all crystallization,which usually are influenced by temperature,stirring state,initial mole ratio of the solute to solvent,the presence of impurities [14].MSZW data of 2,4-diaminobenzenesulfonic acid in the H2SO4+H2O mixture was determined by the laser dynamic method.The accurate mass of 2,4-diaminobenzenesulfonic acid,sulfuric acid and water were added in the crystallizer and developed saturated solution.The saturated solution was agitation for more than 30 min under the constant temperature.When the solution was cooled at 0.1 K?min-1with the stirring rate of 300 r?min-1,the first nucleation appeared and solution temperature was recorded by the laser at that time,then,super-solubility of 2,4-diaminobenzenesulfonic acid can be obtained and the corresponding MSZW region can be calculated[15].

3.Results and Discussion

3.1.Powder X-ray diffraction analysis

The equilibrium solid phases obtained from the solubility measurement were compared with the raw material by Powder X-ray diffraction (PXRD),and the results are shown in the Fig.3.It can be seen that the PXRD patterns of the equilibrium solid phases from different mass fraction of sulfuric acid are consistent with that of the raw material,and there is no peak shift.Which shows that 2,4-diaminobenzenesulfonic acid did not change before and after the solubility measurement.

Fig.3.The PXRD patterns of raw material and equilibrium solid phases of 2,4-diaminobenzenesulfonic acid in different mass fraction of sulfuric acid.

3.2.Solubility data

The solubility data of 2,4-diaminobenzenesulfonic acid in different mass fraction of sulfuric acid at temperature ranging from 298.15 to 338.15 K at atmospheric are listed in the Table 1,and graphically potted in Figs.4 and 5.The results suggest that the solubility of the 2,4-diaminobenzenesulfonic acid increases with temperature.The solubility data shows a clear non-linear trend and are in descending order of 0.7>0.3>0.4>0.6>0.45>0.5 in different mass fraction of sulfuric acid.The solubility in(w=0.5)mass fraction of the sulfuric acid is lowest among the studied solution.Interestingly,2,4-diaminobenzenesulfonic acid solubility in the(w=0.7) mass fraction of the sulfuric acid is remarkably high and almost with linear temperature dependence.The mass fraction of sulfuric acid(w=0.5)is suitable for crystallization.The affected factors may include the polarity of the solvents,the intermolecular interactions between solute and solvent,hydrogen bonding interaction,salting-out effect and so on.

3.3.Solubility of thermodynamic models

Since equilibrium between the liquid and solid is usually not available,correlation and prediction are frequently utilized.Three solubility models of the Apelblat equation,the CNIBS/Redlich-Kister equation and Jouyban-Acree Model are put forword to correlate the experimental solubility values.And the solubility model of 2,4-diaminobenzenesulfonic acid in(H2SO4+H2O)system are discussed below.

The correlation equation are evaluated by the relative deviation(RD) and the root-mean-square deviation (RMSD) [15].They are defined as follows:

wherexexpare the experimental data andxcalare the calculated values,Nis the total number of the experimental data for each system.

3.3.1.Apelblat equation

The Apelblat solution equation deduced from the Clausius-Clapeyron equation is a semiempirical expression for the solubility of a solid in a solution on the solubility[16–18].It is widely used to correlate between solubility of the 2,4-diaminobenzenesulfonic acid and the temperature.The Eq.(5) is expressed as follows:

wherexrepresents the mole fraction solubility of the 2,4-diaminobenzenesulfonic acid,Tis the absolute temperature in Kelvin,A,BandCrepresent the model parameters.A,Brepresent the variation of the activity coefficient and the effect of the solubility of solute in a nonideal solution,andCrepresents the change of the molar heat capacity of dissolution.Three parameters can be acquired by regression of the solubility using multidimensional unconstrained nonlinear minimization.

The experimental and correlated solubility values and figures are listed in the Table 1 and Fig.4,respectively.The parameters,correlation coefficient (R2) together with the RMSD are presented in Table 2.The values ofR2and the tiny RMSD illustrated the fitting curves of modified Apelblat can accurately describe the relation between the solubility of 2,4-diaminobenzenesulfonic acid and the temperature.

Table1 The measured solubility xexp and the calculated solubilityof the 2,4-diaminobenzenesulfonic acid in the binary solvent (H2SO4+H2O) from 298.15 K to 338.15 K

Table1 The measured solubility xexp and the calculated solubilityof the 2,4-diaminobenzenesulfonic acid in the binary solvent (H2SO4+H2O) from 298.15 K to 338.15 K

lnxis a linear relation with 1/Tand lnTin the three-dimensional diagram by the experimental values and each experimental data points lay on the fitting line,shown in Fig.6.Moreover,the values of RMSD are lower than other two fitted equation,so the modified Apelblat equation is the best correlation equation to fit solubility of the 2,4-diaminobenzenesulfonic acid in different mass fraction of sulphuric acid.

3.3.2.CNIBS/Redlich-Kister equation

The (CNIBS)/Redlich-Kister model describes the solubility of a solute in binary solvents varies with binary solvent composition,which proposed by Acree and his workers [19,20].The solubility of the 2,4-diaminobenzenesulfonic acid in binary solvents calculated by the simplified CNIBS/Redlich-Kister model which expressed by Eq.(6).

wherexB,xCrefer to initial mole fraction of water and sulfuric acid in the binary solvent separate.(xA)Band(xA)Care the saturated mole solubilities of the solute in pure solvents B and C,Sirefers to the model parameters (i=0,1,2),when the species of solvent phaseN=2,and thexBis substituted by the 1-xC,up to four equations can be obtained from Eq.(6) representation of the experimental data and expressed Eq.(7).

B0,B1,B2,B3andB4are the parameters,obtained by the leastsquares regression.The solubility values calculated by the(CNIBS)/Redlich-Kister equation posted in the Table 3.The model parametersB0,B1,B2,B3,B4,correlation coefficient (R2) together the RMSD are listed in the Table 3.The values ofR2and the tiny RMSD illustrated (CNIBS)/Redlich-Kister equation can describe the solubility of the 2,4-diaminobenzenesulfonic acid in the H2SO4+H2-O mixture.

3.3.3.Jouyban–Acree model

The Jouyban-Acree model [21] is a well-known equation correlating composition of binary solvent and temperature on the solubility of a solute in binary solvent,which is proposed by Jouyban-Gharamaleki and co-workers.The model is expressed as follows:

whereJiis the model parameter,ln(xA)B,Tand ln(xA)C,Trepresents the solubility of solute in pure solvents,which can be calculated from the modified Apelblat equation,and substitutingwith(1-) and substitution ofN=2 [22],Eq.(9) can give a new simplified Eq.(10) as:

Fig.4.Experiment solubility (x) of 2,4-diaminobenzenesulfonic acid at different temperature in different mass fraction of the sulfuric acid mixture:(▲)0.3,(●)0.4,(▼) 0.45,(■) 0.5,(◆) 0.6,(★) 0.7.

Fig.5.Experiment solubility of 2,4-diaminobenzenesulfonic acid in different mass fraction of the sulfuric acid at controlled temperature:(■) 298 K,(●) 303.15 K,(▲) 308.15 K,(▼) 313.15 K,(◆) 318.15 K,(□) 323.15,(Δ) 328.15 K,(○) 333.15 K,(★) 338.15 K.

whereA0-A8are empirical model parameters,and the calculated values are displayed in the Table 1,and the model parameters values ofA0-A8,R2,and the RMSD are displayed in the Table 4.In addition,theR2values close to 1 and the tiny RMSD indicate that the Jouyban-Acree Model is the perfect equation to describe the solubility of the 2,4-diaminobenzenesulfonic acid in different mass fraction of sulfuric acid.

Table 2 Model parameters A, B, C, R2 and RMSD of Apelblat equation

Table 3 Parameters of B0-B4, R2 and RMSD of the (CNIBS)/Redlich-Kister equations

Table 4 Model parameters A0–A9, R2 and RMSD of Jouyban-Acree model

Table 5 Standard dissolution enthalpy (ΔdisH),entropy (ΔdisS) and Gibbs energy (ΔdisG) at mean temperature (317.62 K) together with the ξH, ξS

Fig.6.Experimental solubility and correlated values by the modified Apelblat equation for 2,4-diaminobenzenesulfonic acid in different mass fraction sulfuric acid:(▲) 0.3,(●) 0.4,(▼) 0.45,(■) 0.5,(◆) 0.6,(★) 0.7.

3.4.Apparent thermodynamic properties of 2,4-diaminobenzenesulfonic acid dissolution

Thermodynamic properties such as standard dissolution enthalpy(ΔdisH),standard entropy(ΔdisS)and standard dissolution Gibbs energy(ΔdisG)can be calculated from the Van’t Hoff analysis[22],the apparent enthalpy change of solution can be expressed as the Eq.(11)

whereRrepresents the gas constant(8.3145 J?K-1?mol-1),ΔdisHand ΔdisSrefer to the dissolution enthalpy and dissolution entropy of the 2,4-diaminobenzenesulfonic acid.ΔdisHand ΔdisScan be obtained separately from slope and intercept of ideal liner fitted.And the dissolution Gibbs energy of the 2,4-diaminobenzenesulfonic acid can be calculated as follows:

where the mean harmonic temperatureTmeancan be calculated in the Eq.(13)

wherenis the number of the experimental temperature.

The ξHand ξSrepresenting contribution of enthalpy and entropy to the dissolution Gibbs energy in the solution process defined by the formula below(14)and(15)and the results are in the Table 5.

ΔdisH>0 inferred the dissolution process is endothermic and solubility of 2,4-diaminobenzenesulfonic acid increased with temperature.ΔdisS>0 demonstrated that the force for the dissolution is entropy-driven [23].The values of dissolution entropy is higher than those of dissolution enthalpy,which suggest that the interaction between 2,4-diaminobenzenesulfonic acid and solvent molecules is more powerful than those between solvent molecules.As shown in Table 5,The dissolution of 2,4-diaminobenzenesulfonic acid exhibits a positive Gibbs free energy change,which indicates that the dissolution process in different mass fraction of sulfuric acid is nonspontaneous and need extra energy.Further,the contributor of enthalpy ξHis greater than ξSto the Gibbs energy inferred the dissolution enthalpy is the main contributor during the dissolution.

3.5.Metastable zone width (MSZW)

The MSZW of 2,4-diaminobenzenesulfonic acid in different temperature and mass fraction of sulfuric acid under stirring speed of 300 r?min-1and cooling rate of 0.1 K?min-1are exhibited in Fig.7,which shows MSZW is increased significantly as crystallization temperature from 298.15 K to 338.15 K and the mass fration of sulfuric acid from 0.3 to 0.7.The solubility and the corresponding supersaturation increased with temperature under the same MSZW,which makes the crystallization condition much easier.Moreover,high temperature enhances the nucleation rate and increases the movement and collision frequency of the molecules.Fig.7 reveals that MSZW broadens with increasing the mass fraction of sulfuric acid from 0.3 to 0.7 and value of MSZW approximately 9.86–24.9 K can be calculated in the Table 6.

Table 6 Supersolubility and MSZW of 2,4-diaminobenzenesulfonic acid in H2SO4+H2O mixture

4.Conclusions

Fig.7.The metastable zone width at different mass fraction of sulfuric acid:(■) 0.3,(●) 0.4,(▲) 0.45,(▼) 0.5,(◆) 0.6,(★) 0.7.

In this work,the solubility of 2,4-diaminobenzenesulfonic acid in different temperature and mass fraction of sulfuric acid were determined using a laser method over the temperature range from 298.15 to 338.15 K under atmospheric pressure.The solubility decreased in order 0.7 >0.3 >0.4 >0.6 >0.45 >0.5,andw=0.5 is lowest in the mass fraction of sulfuric acid because of hydrogen bonding and salting-out effect between 2,4-diaminobenzenesulfonic acid and sulfuric acid.The mole solubility of 2,4-diaminobenzenesulfonic acid is corrected by the modified Apelblat equation,(CNIBS)/Redlich-Kister model and Jouyban–Acree Model,which are found to provide satisfactory correlation.The lower RMSD of modified Apelblat equation is found to be best than the other two equation.The MSZW widened with the temperature and mass fraction of sulfuric acid from 0.3 to 0.7 and value of MSZW approximately 9.86–24.9 K can be calculated.The dissolution enthalpy,dissolution entropy and Gibbs energy were calculated and indicated the dissolution process of 2,4-diaminobenzenesulfonic acid is endothermic.The solubility data and the correlation equation are beneficial for the purification of 2,4-diaminobenzenesulfonic acid.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This work was supported by Scientific and Technologial Innovation Programs of Higher Education Institutions in Shanxi.