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Recovery of phosphate from calcinated bone by dissolution in hydrochloric acid solutions
Resources, Conservation and Recycling 26 (1999) 251–258
Recovery of phosphate from calcinated bone by dissolution in hydrochloric acid solutions Ayhan Demirbas¸ a,*, Yu¨ksel Abalı b, Ebubekir Mert b b
a P.K. 216, TR-61035, Trabzon, Turkey Department of Chemistry, Faculty of Arts and Science, Celal Bayar Uni6ersity , 45030, Manisa, Turkey
Accepted 11 January 1999
Abstract In this study, the optimum conditions of dissolution of calcinated bone in HCl solutions with different concentrations are investigated. Recovery of phosphate from calcinated bone by dissolution with hydrochloric acid solutions was investigated in a batch reactor, it was observed that a 32% hydrochloric acid solution can dissolve the calcinated bone effectively. Using the Taguchi fractional design method, it was found that the optimum process conditions, at which 67.2% P2O5 dissolution was reached, were as follows: Reaction temperature: 318 K, solid-to-liquid ratio: 1/5 (g ml − 1), acid concentrations:32 (% w/v), stirring speed:400 min − 1 and reaction time: 60 min. © 1999 Elsevier Science B.V. All rights reserved. Keywords: Phosphate; Recovery; Optimization; Dissolution
1. Introduction Because of the fact that Turkey is an agriculturally dependent country, the fertilizer industry has vital importance. Phosphate fertilizers having an important
* Corresponding author. Tel.: +90-462-248-7344; fax: + 90-462-248-7344. 0921-3449/99/$ - see front matter © 1999 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 3 4 4 9 ( 9 9 ) 0 0 0 2 1 - X
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place in the fertilizer industry are produced from phosphate rocks. The phosphate fertilizer consumption of the world has increased 8% on average per year. The fact that the population of the world is increasing continuously and that the fertilization of land with chemical fertilizers for the solution of the problem of food shortage has an important role shows that phosphate will protect its important place in the world economy as a much-need material in the future [1,2]. Phosphorus is the basic material of phosphate fertilizers, and 76% of phosphorus production is consumed for fertilization [3]. Bones can be divided into two main parts: Inorganic and organic. The former is consisted of mainly calcium phosphate. The latter is made up of gelatine. According to Sisson, the chemical analyses of bone are as follow [4,5]: Gelatin: 33.30%, calcium phosphate: 57.35%, calcium carbonate: 3.85%, magnesium phosphate: 2.05%, sodium chloride+ sodium carbonate: 3.45% and total: 100.00%. Until the middle of 19th century, bone and quana were used as the raw materials to obtain phosphorus and phosphoric acid. In 1842, John B. Lawes had the first British licence in this field for reacting bone with sulphuric acid. This licence became the start of a great phosphoric acid industry and became the base of artificial fertilizer industry [6]. Artificial chemical fertilizers are the main goods that Turkey have to pay money after petroleum and iron. In this payment, phosphate rocks and phosphate fertilizers have the biggest percent [7]. Many studies have been carried out for the dissolution of phosphate minerals in order to obtain phosphate fertilizers rather than on bone: Tarantsova et al. [8] observed that the dissolution kinetics of flourapatite crystals in HCl solution in the range 293 – 333 K. The process has the following steps: 1. The diffusion of HCl into flourapatite surface, 2. The reaction occurring between HCl and subsurface, 3. The diffusion of products from the inner part of the solid material into the reaction medium. They found that the activation energy belonging to the dissolution reaction was 10 kcal mol − 1. In a similar study conducted by Tennakone et al. [9], related to the production of a non-hygroscopic super phosphate fertilizer from apatite; the phosphate rock was reacted with HCl and they reported that the super phosphate fertilizer obtained was hygroscophic because of the CaCl2 in it, then it was made non-hygroscophic by the addition of (NH4)2SO4. This investigation was aimed to determine the optimum process conditions for the reaction of bone with HCl solutions, using Taguchi fractional design method [10]; considering the production of several phosphate chemicals from bone. Thus it might be worthwhile to investigate the dissolution process in a stirred reactor to produce some phosphate products and the effect of the parameters such as temperature, solid-to-liquid ratio, stirring speed, and leaching time.
A. Demirbas¸ et al. / Resources, Conser6ation and Recycling 26 (1999) 251–258
253
Table 1 Chemical analysis of sample Component
Weight %
P2O5 CaO
26.27 31.55
2. Experimental The calcinated bone which was in the form of fine powder used in the experiments was supplied from a bone factory located in Emiralem–Menemen, I: zmir. In the chemical analysis of material, standard gravimetric and volumetric wet analytical methods were used [11]. The chemical analysis of the material is given in Table 1. Dissolution process was carried out in a 250 ml 3-necked round-bottomed glass reactor equipped with a mechanical stirrer, at atmospheric pressure and constant temperature. 100 ml of hydrochloric acid solution with the reaction concentration was added to the reactor and then heated to the reaction temperature. Adding the calcinated bone in a given amount to the reactor the dissolution process was started. After the reaction was completed the mixture was immediately filtered. The amount of P2O5 in the filtrate obtained after each reaction was determined by gravimetric method. A schematic view of the experimental set-up is shown in Fig. 1.
Fig. 1. Schematic view of experimental set-up: 1, reactor; 2, mechanical stirrer; 3, cooler; 4, thermostat.
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In the experimentation, the Taguchi fractional design method was employed. The optimization criteria were as follows: 1. Maximum amount of P2O5 dissolved, 2. Minimum cost for H3PO4 obtained. The advantage of the Taguchi fractional design method over other experimental design methods is that it gives the facility of investigating a number of parameters at more than two levels. According to Taguchi, among the parameters considered, only important combined effects can be considered in the experimental plan. These combined effects were easily determined after a series of pre-experiments. Because the main and important combined effects are considered in the experimental plan, the number of the experiments should be reduced to a minimum. Increasing the number of experiments requires more time and research costs and, for this reason, some experiments cannot be done. The Taguchi fractional design method allowed us to obtain the optimum experimental conditions. Taking into consideration the number of parameters used in the experiments and their level, one of the standard experimentation plans was chosen. In order to find the dissolved amount of P2O5, for each parameter value a set of five experiments were performed. The average of these experimental results were reported as the dissolved amount of P2O5. At a given condition, each experiment was repeated three times, and the arithmetic average was used in kinetic analysis. These experiments could be repeated with a maximum deviation of 9 2%. 3. Results and discussion Dissolution process of calcinated bone was investigated in different concentrations of HCl solutions. The kind of products, dicalcium phosphate, mono calcium phosphate or phosphoric acid, strictly depends on the concentrations of acid. Reaction equations are as follows: Ca3(PO4)2 +2HCl 2CaHPO4 + CaCl2
(1)
Ca3(PO4)2 +4HCl Ca(H2PO4)2 + 2CaCl2
(2)
Ca3(PO4)2 +6HCl 2H3PO4 + 3CaCl2
(3)
To determine the optimum conditions for the dissolution of calcinated bone in the HCl solutions, the effects of solid-to-liquid ratio, reaction temperature, stirring speed, acid concentration and reaction period were investigated. The reaction conditions in which the effect of parameters investigated and the experimental results are given in Tables 2 and 3, respectively. The maximum amount of P2O5 in the solution and the production costs were considered as the final criteria for optimization. The evaluation of the results was carried out using the ANOVA-TM package programme, variance analyses were made to determine the effectiveness of the parameters are shown in Table 4. The effectiveness of each parameter on optimization criteria and the selected optimum reaction conditions are shown in Table 5.
Table 2 Reaction conditions in which the parameters are observed Temperature (K)
Solid-to-liquid ratio (w/v)
Concentration of HCl, (% w)
Stirring speed (min−1)
Time (min)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
293 293 293 293 293 303 303 303 303 303 318 318 318 318 318 333 333 333 333 333 353 353 353 353 353
1/3 1/5 1/10 1/25 1/50 1/3 1/5 1/10 1/25 1/50 1/3 1/5 1/10 1/25 1/50 1/3 1/5 1/10 1/25 1/50 1/3 1/5 1/10 1/25 1/50
15 22 27 32 37 22 27 32 37 15 27 32 37 15 22 32 37 15 22 27 37 15 22 27 32
200 400 600 800 1000 800 1000 200 400 600 400 600 800 1000 200 1000 200 400 600 800 600 800 1000 200 400
10 20 30 45 60 30 45 60 10 20 60 10 20 30 45 20 30 45 60 10 45 60 10 20 30
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Experiment number
255
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Table 3 Experimental results Experiment number
%P2O5 (a)
%P2O5 (b)
%P2O5 (average)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
12.34 27.31 46.81 60.35 94.70 14.93 37.73 50.45 58.28 55.49 45.21 52.46 55.34 70.62 92.34 41.77 47.07 45.70 59.62 69.23 33.74 47.89 49.93 64.51 96.77
16.07 43.17 53.94 60.64 97.93 14.06 31.85 48.09 70.83 57.50 44.45 52.22 61.28 68.94 93.88 44.89 43.96 46.78 54.79 72.84 33.48 39.21 45.76 54.79 67.10
14.21 35.22 50.36 60.49 96.30 14.50 34.79 49.26 64.63 56.48 44.83 52.34 58.31 69.78 93.10 43.32 45.50 46.23 57.20 71.03 33.59 43.55 47.83 59.65 81.92
The selection of optimum reaction conditions for P2O5 production is done according to the conditions where maximum amount with minimum cost. As it is seen in the tables, the optimum process conditions for dissolving calcinated bone, the formation of dicalcium phosphate, mono calcium phosphate or phosphoric acid are chosen as A3, B2, C4, D2 and E5. According to the following Table 4 Variance analysis carried out on the basis of P2O5 conversion Variation source
Degrees of freedom
Sum of squares
Mean of squares
Test statistics
A B C D E Error Total
4 4 4 4 4 29 49
206.372 1645.112 133.092 57.592 47.572 2089.730 4178.610
51.5930 411.278 33.273 14.398 11.893 72.030 85.279
0.176 5.709* 0.462 0.200 0.165 — —
* Effective parameters for 99% significance level.
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257
Table 5 Determination of optimum parameter values Parameter
Values of parameter
A Dissolution temperature (K)
B
Solid-to-liquid ratio (g ml
−1
C Acid concentration (%w/v)
D Stirring speed (min−1)
E
Reaction period (min)
293 303 318 333 353 )
1/3 1/5 1/10 1/25 1/50
Dissolving P2O5 (%)
Cost
Selection
51.318 44.312 64.212 53.112 53.768
Minimum
A3
30.056 44.444 50.838 62.734 80.450
Maximum Minimum
B2
Maximum
15 22 27 32 37
46.150 50.000 52.574 57.814 60.184
Minimum
200 400 600 800 1000
52.500 55.040 50.428 49.848 58.906
Minimum
10 20 30 45 60
50.140 51.032 52.862 53.958 58.730
C4
Maximum D2
Maximum Minimum
E5
Maximum
optimum processes condition 67.2% P2O5 dissolution was achieved as the maximum amount; Reaction temperature Solid-to-liquid ratio Acid concentrations Stirring speed Reaction time
318 K 1/5 (g ml−1) 32 (% w/v) 400 min−1 60 min
4. Conclusions In this study in which the recovery of phosphate from calcinated bone by dissolution with hydrochloric acid solutions was investigated in a batch reactor, it
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was observed that a 32% hydrochloric acid solution can dissolve the calcinated bone effectively. The importance of the production of phosphates and its compounds from bone is very important in terms of less availability of phosphate rocks in Turkey, much payment for its import and increasing consumption. The optimum process conditions obtained at the end of this investigation by the application of Taguchi fractional design method can be applied to the production of phosphates compounds in large scale.
References [1] Calmonovici CE, Giuliette M. Technological optitude of some Brazilian phosphate rocks for acid decomposition. Ind Eng Chem Res 1990;29:482. [2] Yartas¸ı A, Kocakerim MM, Yapıkı S, O8 zmetin C. Dissolution kinetics of phosphate ore in SO2-saturated water. Ind Eng Chem Res 1994;33:2220. [3] Abalı Y, C ¸ olak S, Yapıcı S. The optimization of the dissolution of phosphate rock with Cl2 – SO2 gas mixtures in aqueous medium. Hydrometallurgy 1997;46:27. [4] Terem N. Anorganic Industrial Chemistry. I: stanbul: University Chemistry Faculty, 1977. [5] O8 zgen H. Animal Feeding, No, 341. Ankara: Ankara University, 1986. [6] C ¸ ataltas¸ AI: . Chemical Process Industries. I: stanbul: I: nk lap ve Aka, 1983. [7] Anon. Chemical industry investigations: phosphate. Bank Ind Dev Turkey 1979;17:1 – 157. [8] Tarantsova MI, Kulikov BA, Chaikina MV, Kolasav AS, Boldyre VV. Kinetics of dissolution of fluoroapatite crystals in solutions of hydrochloric acid. Izv Sib Otd Akad Novk SSSR Ser Khim Nouk 1980;4:55. [9] Tennakone K, Weerasooriya SVR, Jayatisa DI, Damayanthi MLWD, Silva IHK. Nonhygroscopic superphosphate fertilizer from apatite and hydrochloric acid. Funt Stud Fer Res 1988;16:87. [10] Taguchi G. System of Experimental Design, Quality Resources, vol. 1. New York: Kraus, 1987:1189. [11] Furman NH. Scott’s Standard Methods of Chemical Analysis, vol. 1, 6th edn. New York: Van Nostrand, 1963:798.
.
Recovery of phosphate from calcinated bone by dissolution in hydrochloric acid solutions Ayhan Demirbas¸ a,*, Yu¨ksel Abalı b, Ebubekir Mert b b
a P.K. 216, TR-61035, Trabzon, Turkey Department of Chemistry, Faculty of Arts and Science, Celal Bayar Uni6ersity , 45030, Manisa, Turkey
Accepted 11 January 1999
Abstract In this study, the optimum conditions of dissolution of calcinated bone in HCl solutions with different concentrations are investigated. Recovery of phosphate from calcinated bone by dissolution with hydrochloric acid solutions was investigated in a batch reactor, it was observed that a 32% hydrochloric acid solution can dissolve the calcinated bone effectively. Using the Taguchi fractional design method, it was found that the optimum process conditions, at which 67.2% P2O5 dissolution was reached, were as follows: Reaction temperature: 318 K, solid-to-liquid ratio: 1/5 (g ml − 1), acid concentrations:32 (% w/v), stirring speed:400 min − 1 and reaction time: 60 min. © 1999 Elsevier Science B.V. All rights reserved. Keywords: Phosphate; Recovery; Optimization; Dissolution
1. Introduction Because of the fact that Turkey is an agriculturally dependent country, the fertilizer industry has vital importance. Phosphate fertilizers having an important
* Corresponding author. Tel.: +90-462-248-7344; fax: + 90-462-248-7344. 0921-3449/99/$ - see front matter © 1999 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 3 4 4 9 ( 9 9 ) 0 0 0 2 1 - X
252
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place in the fertilizer industry are produced from phosphate rocks. The phosphate fertilizer consumption of the world has increased 8% on average per year. The fact that the population of the world is increasing continuously and that the fertilization of land with chemical fertilizers for the solution of the problem of food shortage has an important role shows that phosphate will protect its important place in the world economy as a much-need material in the future [1,2]. Phosphorus is the basic material of phosphate fertilizers, and 76% of phosphorus production is consumed for fertilization [3]. Bones can be divided into two main parts: Inorganic and organic. The former is consisted of mainly calcium phosphate. The latter is made up of gelatine. According to Sisson, the chemical analyses of bone are as follow [4,5]: Gelatin: 33.30%, calcium phosphate: 57.35%, calcium carbonate: 3.85%, magnesium phosphate: 2.05%, sodium chloride+ sodium carbonate: 3.45% and total: 100.00%. Until the middle of 19th century, bone and quana were used as the raw materials to obtain phosphorus and phosphoric acid. In 1842, John B. Lawes had the first British licence in this field for reacting bone with sulphuric acid. This licence became the start of a great phosphoric acid industry and became the base of artificial fertilizer industry [6]. Artificial chemical fertilizers are the main goods that Turkey have to pay money after petroleum and iron. In this payment, phosphate rocks and phosphate fertilizers have the biggest percent [7]. Many studies have been carried out for the dissolution of phosphate minerals in order to obtain phosphate fertilizers rather than on bone: Tarantsova et al. [8] observed that the dissolution kinetics of flourapatite crystals in HCl solution in the range 293 – 333 K. The process has the following steps: 1. The diffusion of HCl into flourapatite surface, 2. The reaction occurring between HCl and subsurface, 3. The diffusion of products from the inner part of the solid material into the reaction medium. They found that the activation energy belonging to the dissolution reaction was 10 kcal mol − 1. In a similar study conducted by Tennakone et al. [9], related to the production of a non-hygroscopic super phosphate fertilizer from apatite; the phosphate rock was reacted with HCl and they reported that the super phosphate fertilizer obtained was hygroscophic because of the CaCl2 in it, then it was made non-hygroscophic by the addition of (NH4)2SO4. This investigation was aimed to determine the optimum process conditions for the reaction of bone with HCl solutions, using Taguchi fractional design method [10]; considering the production of several phosphate chemicals from bone. Thus it might be worthwhile to investigate the dissolution process in a stirred reactor to produce some phosphate products and the effect of the parameters such as temperature, solid-to-liquid ratio, stirring speed, and leaching time.
A. Demirbas¸ et al. / Resources, Conser6ation and Recycling 26 (1999) 251–258
253
Table 1 Chemical analysis of sample Component
Weight %
P2O5 CaO
26.27 31.55
2. Experimental The calcinated bone which was in the form of fine powder used in the experiments was supplied from a bone factory located in Emiralem–Menemen, I: zmir. In the chemical analysis of material, standard gravimetric and volumetric wet analytical methods were used [11]. The chemical analysis of the material is given in Table 1. Dissolution process was carried out in a 250 ml 3-necked round-bottomed glass reactor equipped with a mechanical stirrer, at atmospheric pressure and constant temperature. 100 ml of hydrochloric acid solution with the reaction concentration was added to the reactor and then heated to the reaction temperature. Adding the calcinated bone in a given amount to the reactor the dissolution process was started. After the reaction was completed the mixture was immediately filtered. The amount of P2O5 in the filtrate obtained after each reaction was determined by gravimetric method. A schematic view of the experimental set-up is shown in Fig. 1.
Fig. 1. Schematic view of experimental set-up: 1, reactor; 2, mechanical stirrer; 3, cooler; 4, thermostat.
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A. Demirbas¸ et al. / Resources, Conser6ation and Recycling 26 (1999) 251–258
In the experimentation, the Taguchi fractional design method was employed. The optimization criteria were as follows: 1. Maximum amount of P2O5 dissolved, 2. Minimum cost for H3PO4 obtained. The advantage of the Taguchi fractional design method over other experimental design methods is that it gives the facility of investigating a number of parameters at more than two levels. According to Taguchi, among the parameters considered, only important combined effects can be considered in the experimental plan. These combined effects were easily determined after a series of pre-experiments. Because the main and important combined effects are considered in the experimental plan, the number of the experiments should be reduced to a minimum. Increasing the number of experiments requires more time and research costs and, for this reason, some experiments cannot be done. The Taguchi fractional design method allowed us to obtain the optimum experimental conditions. Taking into consideration the number of parameters used in the experiments and their level, one of the standard experimentation plans was chosen. In order to find the dissolved amount of P2O5, for each parameter value a set of five experiments were performed. The average of these experimental results were reported as the dissolved amount of P2O5. At a given condition, each experiment was repeated three times, and the arithmetic average was used in kinetic analysis. These experiments could be repeated with a maximum deviation of 9 2%. 3. Results and discussion Dissolution process of calcinated bone was investigated in different concentrations of HCl solutions. The kind of products, dicalcium phosphate, mono calcium phosphate or phosphoric acid, strictly depends on the concentrations of acid. Reaction equations are as follows: Ca3(PO4)2 +2HCl 2CaHPO4 + CaCl2
(1)
Ca3(PO4)2 +4HCl Ca(H2PO4)2 + 2CaCl2
(2)
Ca3(PO4)2 +6HCl 2H3PO4 + 3CaCl2
(3)
To determine the optimum conditions for the dissolution of calcinated bone in the HCl solutions, the effects of solid-to-liquid ratio, reaction temperature, stirring speed, acid concentration and reaction period were investigated. The reaction conditions in which the effect of parameters investigated and the experimental results are given in Tables 2 and 3, respectively. The maximum amount of P2O5 in the solution and the production costs were considered as the final criteria for optimization. The evaluation of the results was carried out using the ANOVA-TM package programme, variance analyses were made to determine the effectiveness of the parameters are shown in Table 4. The effectiveness of each parameter on optimization criteria and the selected optimum reaction conditions are shown in Table 5.
Table 2 Reaction conditions in which the parameters are observed Temperature (K)
Solid-to-liquid ratio (w/v)
Concentration of HCl, (% w)
Stirring speed (min−1)
Time (min)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
293 293 293 293 293 303 303 303 303 303 318 318 318 318 318 333 333 333 333 333 353 353 353 353 353
1/3 1/5 1/10 1/25 1/50 1/3 1/5 1/10 1/25 1/50 1/3 1/5 1/10 1/25 1/50 1/3 1/5 1/10 1/25 1/50 1/3 1/5 1/10 1/25 1/50
15 22 27 32 37 22 27 32 37 15 27 32 37 15 22 32 37 15 22 27 37 15 22 27 32
200 400 600 800 1000 800 1000 200 400 600 400 600 800 1000 200 1000 200 400 600 800 600 800 1000 200 400
10 20 30 45 60 30 45 60 10 20 60 10 20 30 45 20 30 45 60 10 45 60 10 20 30
A. Demirbas¸ et al. / Resources, Conser6ation and Recycling 26 (1999) 251–258
Experiment number
255
256
A. Demirbas¸ et al. / Resources, Conser6ation and Recycling 26 (1999) 251–258
Table 3 Experimental results Experiment number
%P2O5 (a)
%P2O5 (b)
%P2O5 (average)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
12.34 27.31 46.81 60.35 94.70 14.93 37.73 50.45 58.28 55.49 45.21 52.46 55.34 70.62 92.34 41.77 47.07 45.70 59.62 69.23 33.74 47.89 49.93 64.51 96.77
16.07 43.17 53.94 60.64 97.93 14.06 31.85 48.09 70.83 57.50 44.45 52.22 61.28 68.94 93.88 44.89 43.96 46.78 54.79 72.84 33.48 39.21 45.76 54.79 67.10
14.21 35.22 50.36 60.49 96.30 14.50 34.79 49.26 64.63 56.48 44.83 52.34 58.31 69.78 93.10 43.32 45.50 46.23 57.20 71.03 33.59 43.55 47.83 59.65 81.92
The selection of optimum reaction conditions for P2O5 production is done according to the conditions where maximum amount with minimum cost. As it is seen in the tables, the optimum process conditions for dissolving calcinated bone, the formation of dicalcium phosphate, mono calcium phosphate or phosphoric acid are chosen as A3, B2, C4, D2 and E5. According to the following Table 4 Variance analysis carried out on the basis of P2O5 conversion Variation source
Degrees of freedom
Sum of squares
Mean of squares
Test statistics
A B C D E Error Total
4 4 4 4 4 29 49
206.372 1645.112 133.092 57.592 47.572 2089.730 4178.610
51.5930 411.278 33.273 14.398 11.893 72.030 85.279
0.176 5.709* 0.462 0.200 0.165 — —
* Effective parameters for 99% significance level.
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257
Table 5 Determination of optimum parameter values Parameter
Values of parameter
A Dissolution temperature (K)
B
Solid-to-liquid ratio (g ml
−1
C Acid concentration (%w/v)
D Stirring speed (min−1)
E
Reaction period (min)
293 303 318 333 353 )
1/3 1/5 1/10 1/25 1/50
Dissolving P2O5 (%)
Cost
Selection
51.318 44.312 64.212 53.112 53.768
Minimum
A3
30.056 44.444 50.838 62.734 80.450
Maximum Minimum
B2
Maximum
15 22 27 32 37
46.150 50.000 52.574 57.814 60.184
Minimum
200 400 600 800 1000
52.500 55.040 50.428 49.848 58.906
Minimum
10 20 30 45 60
50.140 51.032 52.862 53.958 58.730
C4
Maximum D2
Maximum Minimum
E5
Maximum
optimum processes condition 67.2% P2O5 dissolution was achieved as the maximum amount; Reaction temperature Solid-to-liquid ratio Acid concentrations Stirring speed Reaction time
318 K 1/5 (g ml−1) 32 (% w/v) 400 min−1 60 min
4. Conclusions In this study in which the recovery of phosphate from calcinated bone by dissolution with hydrochloric acid solutions was investigated in a batch reactor, it
258
A. Demirbas¸ et al. / Resources, Conser6ation and Recycling 26 (1999) 251–258
was observed that a 32% hydrochloric acid solution can dissolve the calcinated bone effectively. The importance of the production of phosphates and its compounds from bone is very important in terms of less availability of phosphate rocks in Turkey, much payment for its import and increasing consumption. The optimum process conditions obtained at the end of this investigation by the application of Taguchi fractional design method can be applied to the production of phosphates compounds in large scale.
References [1] Calmonovici CE, Giuliette M. Technological optitude of some Brazilian phosphate rocks for acid decomposition. Ind Eng Chem Res 1990;29:482. [2] Yartas¸ı A, Kocakerim MM, Yapıkı S, O8 zmetin C. Dissolution kinetics of phosphate ore in SO2-saturated water. Ind Eng Chem Res 1994;33:2220. [3] Abalı Y, C ¸ olak S, Yapıcı S. The optimization of the dissolution of phosphate rock with Cl2 – SO2 gas mixtures in aqueous medium. Hydrometallurgy 1997;46:27. [4] Terem N. Anorganic Industrial Chemistry. I: stanbul: University Chemistry Faculty, 1977. [5] O8 zgen H. Animal Feeding, No, 341. Ankara: Ankara University, 1986. [6] C ¸ ataltas¸ AI: . Chemical Process Industries. I: stanbul: I: nk lap ve Aka, 1983. [7] Anon. Chemical industry investigations: phosphate. Bank Ind Dev Turkey 1979;17:1 – 157. [8] Tarantsova MI, Kulikov BA, Chaikina MV, Kolasav AS, Boldyre VV. Kinetics of dissolution of fluoroapatite crystals in solutions of hydrochloric acid. Izv Sib Otd Akad Novk SSSR Ser Khim Nouk 1980;4:55. [9] Tennakone K, Weerasooriya SVR, Jayatisa DI, Damayanthi MLWD, Silva IHK. Nonhygroscopic superphosphate fertilizer from apatite and hydrochloric acid. Funt Stud Fer Res 1988;16:87. [10] Taguchi G. System of Experimental Design, Quality Resources, vol. 1. New York: Kraus, 1987:1189. [11] Furman NH. Scott’s Standard Methods of Chemical Analysis, vol. 1, 6th edn. New York: Van Nostrand, 1963:798.
.