Thermal dehydration kinetics and characterization of pandermite

Abstract

Pandermite (Ca₄B₁₀O₁₉ 7H₂O) can be defined as a type of calcium borate hydrate which generally founds in Turkey and USA. It has been identified by using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and Scanning electron microscope (SEM) during dehydration process. Thermal gravimetry and differential thermal gravimetry (TG/DTG) methods have been applied to investigate the thermal dehydration kinetic of pandermite. The results showed that it lost its crystal water via three-step process approximately between 280°C and 550°C temperatures. Activation energies (E_a .) were found as 98.83, 136.86 and 391.24 kJ using Ozawa–Flynn–Wall (OFW) model; 89.82, 133.16 and 399.01 kJ using Kissinger–Akahira–Sunose (KAS) model; and 140.78, 131.01 and 486.22 kJ using Kissinger non-isothermal kinetic model for steps 1, 2 and 3, respectively. At the end of the dehydration process, Pandermite lost its water content and it decomposed to CaB₂O₄ (powder diffraction file number: 00-009-0247) and B₂O₃ (powder diffraction file number: 01-072-0626) occurred.

Keywords

Pandermite non-isothermal kinetic thermal decomposition characterization KAS method OFW method Kissenger method

1 Introduction

Boron is found as combinations of metal elements in nature. There are over 200 minerals worldwide that contain boron element. Turkey has 72% of the world’s boron reserves. Because of their significant thermal, mechanical and chemical features- boron minerals have been employed in a wide range of uses for different areas of applications such as glass, ceramic, cement, health, metallurgy, flame retardants, detergent, agriculture, catalysts, and nuclear energy fuels. They can be classified according to their metal complexes such as sodium borates, calcium borates and magnesium borates [1, 2]. Although the majority of borate minerals have identified, there are still other fine-grained, microcrystalline species whose structures and properties remain unknown.

Pandermite (Ca₄B₁₀O₁₉·7H₂O), which has a layered structure, belongs to the pentaborate group. It has a monoclinic crystal lattice structure with a density of 2.42 g/cm³ and hardness of 3 – 3.5 Mohr. Its crystals are white and fine grained. Chemical composition of pandermite is as follows; 49.87% of B₂O₃, 32.04% of CaO and 18.07% of H₂O. It was originally described in 1877; however chemical and optical studies showed that pandermite and priceite had the same structure and pandermite was identical to priceite [3, 4]. Pandermite can be associated with colemanite (Ca₂B₆O11·5H₂O), howlite (Ca₂B₅SiO₉(OH)₅) and gypsum (CaSO₄·2H₂O) under surface or near surface conditions. The reserves of pandermite are found as nodules in shale in Death Valley, California, USA; and also as large masses underlying gypsum and clay beds in the northwestern part of Turkey [5, 6]. Crystallographic structure of Pandermite was examined by Larsen [7] and Walwork et al., [4]. Gur et al., studied the dissolution kinetics and mechanism of Pandermite in acetic acid solutions [8]. Frost et al., examined the characteristic vibrations of Pandermite using Raman and FT-IR spectroscopy techniques [5].

Thermal decomposition reaction of boron minerals generally starts with the removal of crystal water and continues with the removal of hydroxyl ions as water molecules from the structure. These stages of decomposition are defined as dehydration and dehydroxylation, respectively. Amorphization or reconstruction of dehydrated structure was observed with increasing temperature [9, 10]. There are some studies on the thermal dehydration behavior and kinetics of boron mineral and compounds [11 –22]. Borax (Na₂B₄O₇·10H₂O) lost its crystal water via a two-step process between 30 and 600°C and activation energy was found as 61 kJ and 11 kJ for the first and second step [11]. Thermal dehydration behavior of tincalconite (Na₂B₄O₇·5H₂O) was explained with the first order kinetic model by a two-step process [12]. Koga and Utsuoka indicated that dehydration process of lithium metaborate dihydrate (LiBO₂·2H₂O) ended at 450°C and phase transformation occurred with the increasing temperature to 900°C [13]. Erdogan et al., studied the thermal dehydration behavior of ulexite (NaCaB₅H₁₆O₁₇), tunellite (SrB₆H₈O₁₄) and howlite (Ca₂B₅SiH₅O₁₄) [14]. The thermal dehydration process of synthesized sodium metaborate tetrahydrate (NaB(OH)₄·2H₂O) was explained with Coats–Redfern method [15]. Thermal decomposition of inderite (Mg₂B₆O₁₁·15H₂O) proceeds in the 70–767°C temperature range with dehydration and dehydroxylation steps [16]. Yilmaz et al., studied thermal dehydration kinetic parameters of tunellite (SrB₆H₈O₁₄) in the range of 36–718°C and dehydration mechanism [17]. Derun et al., investigated the dehydration mechanisms of mcallisterite (Mg₂(B₆O₇(OH)₆)₂ 9(H₂O)) [18] and admontite (MgO(B₂O₃)₃·7(H₂O)) [19]. Thermal kinetic parameters of zinc borate hydrate (Zn₃B₆O₁₂·3.5H₂O) were determined by Kipcak et al. and the activation energies were found as 250 kJ for the first step and 520 kJ for the second step [20]. According to the thermal behavior of santite (KB₅O₈·4H₂O), dehydration process occurred via a two-step process and total mass loss was determined as 25% [21, 22].

The knowledge of thermal dehydration behavior of boron minerals have become very important for the production of boron compounds and development of various applications. For example, the boron minerals and compounds with high thermal resistance such as colemanite and zinc borate hydrates can be employed in the production of fire retardant materials [19]. This study aims to determine the detailed thermal behavior of pandermite. The non-isothermal kinetic parameters of the thermal dehydration of Pandermite were calculated by using the following methods: Ozawa–Flynn–Wall (OFW); Kissinger–Akahira–Sunose (KAS); Kissinger non isothermal analysis. The mineral were conducted by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscope (SEM).

2 Materials and methods

2.1 Mineral characterization and thermal behavior

Pandermite was provided from the region of Bigadic, Balikesir in Turkey. The mineral was cleaned from its visible impurities; then ground and sieved to achieve a uniform size (particle size < 75 μm). Identification of the mineral was carried out by PANalytical XPert Pro XRD (45 kV, 40 mA (λ= 1.53 cm^-1)) using Cu-Kα radiation in the 2θ range of 7–90°. The characteristic band values were detected by Perkin Elmer FT-IR supplied with a universal attenuation total reflectance (ATR) sampling accessory accommodated with a diamond/ZnSe crystal. The measurement range was 1800 cm^-1–650 cm^-1. The surface morphology of the mineral were investigated by using a CamScan Apollo 300 field-emission SEM at 15 kV. The detector used was a back scattering electron (BEI) and the magnification was set to 5,000.

Thermal dehydration behavior of Pandermite was studied between the temperature ranges of 50–650°C with a Perkin Elmer Diamond TG/DTA. Three different heating rates (10°C/min, 15°C/min, and 20°C/min) were applied in an inert (Nitrogen) atmosphere. After the characterization and thermal dehydration had been performed, mineral was placed in a Protherm MOS 180/4 high-temperature furnace in nitrogen flowing (5 ml/min) atmosphere in order to investigate the thermal conversion. Calcined sample was further analyzed by XRD and FT-IR.

2.2 Thermal dehydration kinetics

Kinetic parameters of activation energy (E_a) and exponential factor (k_o) were calculated by applying Ozawa–Flynn–Wall (OFW), Kissinger–Akahira–Sunose (KAS) and Kissinger non-isothermal kinetic methods.

In OFW non-isothermal kinetic method, thedata from the TG curve in the dehydration range for each heating rate was used to determine the kinetic parameters. Kinetic parameters were calculated using the plot of conversion (α) as a temperature function (T). The OFW kinetic method equations are given in Equation (1): $ln β = In \frac{0.0048 k_{0} E_{a}}{g (α) R} - 1.0516 \frac{E_{a}}{RT}$ (1)

In KAS kinetic method, kinetic parameters were calculated by using the plot of conversion (α) as the temperature function (T) of TG curves. The data are plotted on the graph as “–ln(β/T²) and 1/T”. The slope of line was -E_a/R. The equation for KAS kinetic method was given in Equation (2): $In \frac{β}{T^{2}} = In \frac{k_{0} E_{a}}{g (α) R} - \frac{E_{a}}{RT}$ (2)

In Kissinger kinetic method (Equation (3)), kinetic parameters were calculated by using the peak temperatures of DTG curves. Ea is obtained from the slope of the –ln(β/T_m²) vs 1/T_m plot. $In \frac{β}{T_{m}^{2}} = In \frac{k_{0} E_{a}}{R} - \frac{E_{a}}{{RT}_{m}}$ (3)

3 Results and discussion

3.1 Characterization of Pandermite

According to XRD analysis, the mineral used in the study was found to be Ca₄B₁₀O₁₉ 7H₂O with powder diffraction file number of “00-009-0147”. XRD pattern of pandermite is presented in Fig. 1. The characteristic peaks (d_spacing) of pandermite were observed at the 2θ positions of 8.105° (10.90Å), 16.221° (5.46Å), 24.503° (3.63Å), 25.502° (3.49Å), 32.309° (2.72Å) and 41.385° (2.18Å).

Fig.1

XRD pattern of Pandermite.

FT-IR spectrum of pandermite is given in Fig. 2. The band values in the range of 3547–1657 cm^-1 indicate that the mineral has crystal water content. The characteristic peaks at 1421 and 1347 cm^-1 can be explained by an asymmetric stretching of three coordinate boron to oxygen bands [ν_as(B₍₃₎–O)]. The bands at 1310 and 1247 cm^-1 are assigned to the bending mode of boron-oxygen-hydrogen [δ(B–O–H)]. The peaks between 1060 cm^-1 and 1010 cm^-1 are the asymmetric stretching of four coordinate boron to oxygen bands [ν_as(B₍₄₎–O)]. The bands in the region of 883 cm^-1 are symmetric stretching of three coordinate boron to oxygen bands [ν_s(B₍₃₎–O)]. The band at 782 cm^-1 is related to the symmetric stretching of four coordinate boron to oxygen bands [ν_s(B₍₄₎–O)]. The frequency at 712 cm^-1 belongs to the bending of three coordinate boron [δ(B-O-H)]. The obtained FT-IR bands were in accordance with the results obtained by Jun et al., [23].

Fig.2

FT-IR spectrum of Pandermite.

The surface morphology of the mineral is presented in Fig. 3. The surface occurs from the particles in the form of angular layers. The size of layers are in the range of 5–10μm, and some particles are seen in sub-micron scale on the layers.

Fig.3

SEM image of Pandermite.

3.2 Thermal dehydration behavior and kinetic results

The dehydration process was observed in three stages within the temperature range of 200 and 650°C. The mass loss was negligible at the temperatures under the 200°C. Thermal analyses results are presented in Table 1 and Fig. 4. The probable reactions for the thermal dehydration process are given in Equation (4), (5) and (6). Removal of crystal water could occur in the first stage of the process. It was seen in the range of 278.40°C –309.20°C and its DTG peak was observed at 309.20°C. In this stage, weight loss was 2.83%, which is equal to 1.0 moles of water. The second stage, which has a DTG peak at 363.87°C, was obtained between 339.23 and 398.52°C. The 2.43% weight loss in the second step, was similar to the first step of dehydration and this value is approximately equal to 1.0 moles of water. The rebuilding of the structure may occur with the release of 2 moles of water. In last step dehydration and dehydroxilation processes occurred together. This stage began at 423.93°C and ended at 522.50°C. The third DTG peak was seen at 466.05°C. Higher amount of water removal was seen at the third step with a weight loss of 12.93% and this is equal to 5.0 moles of water. Total average weight loss was found as 18.15%.

Fig.4

TG/DTG analyses results of Pandermite.

Table 1

Thermal analyses results of Pandermite

Heating Rate (°C/min)	10	15	20
1st stage
T_initial (°C)	278.40	288.41	300.73
T_final (°C)	339.23	350.01	360.02
T_peak (DTG) (°C)	309.20	328.45	333.84
w_loss (%)	2.83	2.70	2.64
2nd stage
T_initial (°C)	339.23	350.01	360.02
T_final (°C)	398.52	403.14	410.07
T_peak (DTG) (°C)	363.87	372.26	380.81
w_loss (%)	2.43	2.00	1.71
3rd stage
T_initial (°C)	423.93	403.14	410.07
T_final (°C)	522.50	541.71	558.69
T_peak (DTG) (°C)	466.05	470.13	474.29
w_loss (%)	12.93	13.44	13.78
Total weight loss (%)	18.19	18.14	18.13

The crystal water content of pandermite was found to be compatible with the previous studies. According to the studies of Stoch and Waclawska, thermal behavior of pandermite can be explained with the splitting off of the H₂O groups, splitting off of the hydroxyl groups from borate anion, and formation of free water molecules. The rearrangement of the structure could be seen with the increasing temperature [9, 10]. ${Ca}_{4} B_{10} O_{19} \cdot 7 H_{2} O (s) \overset{h e a t}{\to} {Ca}_{4} B_{10} O_{19} \cdot 6 H_{2} O (s) + H_{2} O (g) 1^{st} step$ (4) ${Ca}_{4} B_{10} O_{19} \cdot 6 H_{2} O (s) \overset{h e a t}{\to} 2 ({Ca}_{2} B_{5} O_{8} (OH)_{3} \cdot H_{2} O) (s) + H_{2} O (g) 2^{nd} step$ (5) $2 ({Ca}_{2} B_{5} O_{8} (OH)_{3} \cdot H_{2} O) (s) \overset{h e a t}{\to} 4 {CaB}_{2} O_{4} (s) + B_{2} O_{3} (s) + 5 H_{2} O (g) 3^{rd} step$ (6)

OFW, KAS and Kissinger non-isothermal kinetic methods have been applied for the calculation of the activation energy (E_a) and the exponential factor (k_o). E_a values were calculated for the conversion values between 0.1 and 0.9 in the methods of OFW and KAS. The calculated kinetic parameters for the OFW and KAS methods can be seen in Table 2.

Table 2

Calculated parameters for the OFW and KAS kinetic methods

		OFW			KAS
	Conversion (α)	E_a (kJ)	k_o	R²	E_a (kJ)	k_o	R²
1st stage	0.1	85.08	–4.25×10⁷	0.9850	79.97	–19.68	0.9812
	0.2	88.50	–3.24×10⁵	0.9831	83.44	–0.15	0.9789
	0.3	91.69	–5.05×10⁵	0.9823	86.68	–0.22	0.9780
	0.4	94.49	–7.27×10⁵	0.9904	89.53	–0.31	0.9881
	0.5	96.70	–9.42×10⁵	0.9921	91.79	–0.40	0.9902
	0.6	98.68	–1.16×10⁶	0.9967	93.77	–0.48	0.9959
	0.7	97.88	–8.33×10⁵	0.9913	92.83	–0.34	0.9892
	0.8	99.07	–8.87×10⁵	0.9928	94.01	–0.35	0.9911
	0.9	101.36	–1.17×10⁶	0.9929	96.32	–0.46	0.9912
	E_a. _average	98.83			89.82
2nd stage	0.1	109.82	–8.60×10⁸	0.9959	105.04	–1.56	0.9950
	0.2	118.81	–1.92×10⁷	0.9892	114.41	–7.07	0.9870
	0.3	127.67	–8.63×10⁷	0.9899	123.65	–31.12	0.9880
	0.4	134.50	–2.69×10⁸	0.9864	130.75	–95.28	0.9840
	0.5	138.47	–4.88×10⁸	0.9807	134.86	–170.53	0.9775
	0.6	143.38	–1.04×10⁹	0.9861	139.96	–359.19	0.9838
	0.7	148.23	–2.16×10⁹	0.9847	145.00	–734.71	0.9823
	0.8	151.18	–3.00×10⁹	0.9724	148.01	–1003.13	0.9682
	0.9	159.63	–1.01×10¹⁰	0.9652	156.77	–3285.96	0.9602
	E_a. _average	136.86			133.16
3rd stage	0.1	253.12	–2.73×10¹⁸	0.9865	254.32	–3.65×10⁹	0.9854
	0.2	811.22	–3.02×10⁵⁷	0.9292	840.99	–7.82×10⁵⁰	0.9277
	0.3	589.76	–2.76×10⁴⁰	0.9571	607.99	–7.08×10³³	0.9558
	0.4	482.24	–1.54×10³²	0.9811	494.82	–3.90×10²⁵	0.9804
	0.5	388.08	–1.16×10²⁵	0.983	395.70	–2.92×10¹⁸	0.9822
	0.6	331.27	–5.63×10²⁰	0.9829	335.87	–1.40×10¹⁴	0.9818
	0.7	277.65	–5.07×10¹⁶	0.9805	279.35	–1.24×10¹⁰	0.9773
	0.8	229.37	–1.20×10¹³	0.9809	228.41	–2.91×10⁶	0.9836
	0.9	158.49	–8.86×10⁷	0.9754	153.62	–21.1	0.9929
	E_a. _average	391.24			399.01

In the OFW kinetic method, correlation factors (R²) were found between 0.9292 and 0.9962. Average of E_a values in the first, second and third steps of dehydration processes were determined as 98.83, 136.86 and 391.24 kJ, respectively. The k_o values were calculated between the –4.25×10⁷ and –3.24×10⁵, between the –1.01×10¹⁰ ––1.92×10⁷ and between the –3.02×10⁵⁷ ––8.86×10⁷ during the first, second and third step of dehydration respectively.

In the KAS kinetic method, R² values were found between 0.9959 and 0.9277. Average of E_a values in the first, second and third steps of dehydration processes were found as 89.82, 133.16 and 399.01 kJ, respectively. k_o values were found between –19.68 and –0.15 for the first step of dehydration. At the second step of dehydration, k_o values varied in the range of –3285.96 – –1.56. At the third step of dehydration, k_o values were observed between –7.82×10⁵⁰ and –21.1.

The calculated kinetic parameters for Kissinger method are given in Table 3. In the Kissinger kinetic method, R² values varied between 0.9989 and 0.9893. E_a and k_o values were found as 140.78 kJ and 1.95×10¹³ for the first step, 131.01 kJ and 2.92×10¹² for the second step, 486.22 kJ and 8.98×10³³ for the third step, respectively.

Table 3

Calculated parameters for Kissinger kinetic method

	E_a (kJ)	k_o	R²
1st Stage	140.78	1.95×10¹³	0.9989
2nd Stage	131.01	2.92×10¹²	0.9893
3rd Stage	486.22	8.98×10³³	0.9917

As it is seen from the thermal kinetic results, the activation energies were found in the ranges of 89.82–140.78 kJ for the first step, 131.01–136.86 kJ for the second step and 391.24 –486.22 kJ for the third step. In comparison with other types of boron minerals, pandermite has a higher thermal resistance than the majority of borates. The activation energies of metal are compared in Table 4 [11 , 18–21].

Table 4

Activation energy comparison of pandermite among the other types of borates

Borates	Kinetic method	Reaction Steps	E_a (kJ)	Reference
Pandermite	OFW	1	98.83
		2	136.86
		3	391.24
	KAS	1	89.82
		2	133.16
		3	399.01
	Kissenger	1	140.78
		2	131.01
		3	486.22
Tincal	Kissenger	1	73.79	[11]
	Doyle	1	75.89
Howlite	First order thermal decomposition	1	65.0	[14]
Tunellite	First order thermal decomposition	1	50.4	[14]
Ulexite	First order thermal decomposition	1	39.5	[14]
Inderite	Ozawa	1	87.0	[16]
Mcalisterite	Ozawa	1	100.0	[18]
	KAS	1	98.0
Admontite	Ozawa	1	107.72	[19]
		2	165.72
Zinc borate hydrate	Coast Redfern	1	225.40	[20]
		2	570.63
Santite	Doyle	1	107.77	[21]
		2	304.18

3.3 Characterization of calcined mineral

A non-hydrate form of the mineral was obtained from the thermal conversion of pandermite. XRD pattern of dehydrated mineral is presented in Fig. 5. According to the XRD result, Pandermite decomposes into calcium borate and boron oxide, which is compatible with the probable reaction given in Equation (6). The calcined mineral was identified as the mixture of CaB₂O₄ (powder diffraction file number: 00-022-0140) and B₂O₃ (powder diffraction file number: 01-072-0626).

Fig.5

XRD pattern of dehydrated Pandermite.

FT-IR spectrum of calcined pandermite sample can be seen in Fig. 6. According to FT-IR results, the characteristic band values of the crystal water content, which were between 3547 and 1657 cm^-1, disappeared. After calcination step, there were some minor changes at the band values of characteristic B-O vibrations because of the decomposition of structure.

Fig.6

FT-IR spectrum of dehydrated Pandermite.

The surface morphology of dehydrated mineral is given in Fig. 7. After the dehydration, some cracks and agglomerations on the angular layers of pandermite particles occur by the separation of water from the structure as well as the heat effect. The amount of sub-micron particles increase and they take the shape of polygonal structures.

Fig.7

SEM image of dehydrated Pandermite.

4 Conclusion

The investigation of thermal dehydration kinetics are important in the development of applications for boron minerals and compounds. In this paper, a calcium borate mineral of Pandermite (Ca₄B₁₀O₁₉ 7H₂O) was investigated. Thermal analysis results showed that dehydration process of pandermite occurred in three steps. Mineral started to lose its water content at 278.40°C; however weight losses were quite low until 423.98°C. Activation energies were determined by using OFW, KAS and Kissinger non-isothermal kinetic techniques. In the OFW method, E_a values were found as 98.83, 136.86 and 391.24 kJ for the first, second and third stages of dehydration process respectively. In KAS method, E_a of the first step was determined as 89.82 kJ; E_a of the second step was found as 133.16 kJ; and E_a of the third step was calculated as 399.01 kJ. In the Kissinger method, activation energies were determined as 140.78 kJ for the first step, 131.01 kJ for the second step, 486.22 kJ for the third step, respectively. According to XRD results, Ca₄B₁₀O₁₉ 7H₂O decomposes into CaB₂O₄ and B₂O₃. At the FT-IR analysis, characteristic band values are found in good agreement with the previous studies. On the basis of SEM observations of the mineral, particle size decreases and agglomerations increase with the effect of heat.

Footnotes

Acknowledgments

The author would like to express her deepest gratitude to Prof. Dr. Sabriye Piskin and Assoc. Dr. Emek Moroydor Derun for their contribution to my academic life.

References

Bulton

R.B.

, Chemicals, Society of Mining, Metallurgy and Exploration, USA, 2006, 7th edn.

Povarennykh

A.S.

, Crystal Chemical Classification of Minerals, Springer, 2014, 1st edn.

Ropp

R.C.

, Encyclopedia of the alkaline earth compounds, Oxford, 2013, 1st edn.

Wallwork

K.S.

, Pring

, Taylor

M.R.

and Hunter

B.A.

, The structure of priceite, a basic hydrated calcium borate, by ab initio powder-diffraction methods, The Canadian Mineralogist 40 (2002), 1199–1206.

Frost

R.L.

, Lopez

, Scholz

and Xi

, Vibrational Spectroscopy of the Borate Mineral Priceite—Implications for the Molecular Structure, Spectroscopy Letters 48 (2015), 101–106.

Helvaci

and Alonso

R.N.

, Borate Deposits of Turkey and Argentina; A Summary and Geological Comparison, Turkish Journal of Earth Sciences 9 (2000), 1–27.

Larsen

E.S.

, Proof That Priceite Is A Distinct Mineral Species American Mineralogist, 2 (1917), 1–2.

Gur

, Caglayan

, Yildiz

and Selcuk

, Dissolution kinetics and mechanism of pandermite in acetic acid solutions, African Journal of Biotechnology 9 (2010), 3404–3413.

Stoch

and Waclawska

, Thermal decomposition of hydrated borates: Part 3. Structural mechanism of thermal decomposition of borates, Thermochimica Acta 215 (1993), 273–279.

10.

Stoch

and Waclawska

, Thermal decomposition of hydrated borates: Part 1. Thermal decomposition of pandermite Ca₂B₅O₈(OH)₃ 2H₂O, Thermochimica Acta 215 (1993), 255–264.

11.

Ekmekyapar

, Baysar

and Kunkul

, Dehydration Kinetics of Tincal and Borax by Thermal Analysis, Industrial and Engineering Chemistry Research 36 (1997), 3487–3790.

12.

Ekmekyapar

, Basar

and Yuceer

, Nonisothermal Dehydration Kinetics of Tincalconite by Thermal Analysis Data, Journal of chemical engineering of Japan 42 (2009), 478–484.

13.

Koga

and Utsuoka

, Thermal dehydration of lithium metaborate dihydrate and phase transitions of anhydrous product, Thermochimica Acta 443 (2006), 197–205.

14.

Erdogan

, Zeybek

, Sahin

and Demirbas

, Dehydration kinetics of howlite, ulexite, and tunellite using thermogravimetric data, Thermochimica Acta 326 (1999), 99–107.

15.

Kanturk

, Sari

and Piskin

, Synthesis Crystal Structure and Dehydration Kinetics of NaB(OH)₄.2H₂O, Korean Journal of Chemical Engineering 25 (2008), 1331–1337.

16.

Kanturk

, Sari

and Piskin

, Structural characterization and dehydration kinetics of Kirka inderite mineral: Application of non-isothermal models, Material Characterization 61 (2010), 640–647.

17.

Yilmaz

M.S.

, Kanturk

and Piskin

, Study on the dehydration kinetics of tunellite using non-isothermal methods, Research on Chemical Intermediates 41 (2015), 1893–1906.

18.

Derun

E.M.

and Senberber

F.T.

, Characterization and Thermal Dehydration Kinetics of Highly Crystalline Mcallisterite, Synthesized at Low Temperatures, The Scientific World Journal 2014 (2014), 1–10.

19.

Derun

E.M.

, Kipcak

A.S.

, Senberber

F.T.

and Yilmaz

M.S.

, Characterization and thermal dehydration kinetics of admontite mineral hydrothermally synthesized from magnesium oxide and boric acid precursor, Research on Chemical Intermediates 41 (2015), 853–866.

20.

Kipcak

A.S.

, Senberber

F.T.

, Derun

E.M.

, Tugrul

and Piskin

, Characterization and thermal dehydration kinetics of zinc borates synthesized from zinc sulfate and zinc chloride, Research on Chemical Intermediates 41 (2015), 9129–9143.

21.

Asensio

M.O.

, Yildirim

, Senberber

F.T.

, Kipcak

A.S.

and Derun

E.M.

, Thermal dehydration kinetics and characterization of synthesized potassium borates, Research on Chemical Intermediates 42 (2016), 4859–4878.

22.

Ceyhan

A.A.

, Demir

and Sahin

, The Investigation Of Thermal Decomposition Kinetics Of Potassium Tetraborate Tetrahydrate By Thermal Analysis, Selcuk University Journal of Engineering, Science and Technology, 24 (2009), 39–45.

23.

Jun

, Shuping

and Shiyang

, FT-IR and Raman spectroscopic study of hydrated borates, Spectrochim Acta 51 (1995), 519–532.