INVESTIGATION OF KINETICS LEACHING AND EXTRACTION OF VANADIUMPENTOXYDE AS A FUNCTION OF TEMPERATURE
RAZISKAVE KINETIKE LUŽENJA IN EKSTRAKCIJE VANADIJEVEGA PENTOKSIDA V ODVISNOSTI OD TEMPERATURE
NIKOLA NACEVSKI1, B. NIKOV2
'Faculty of TechnoIogy and metallurgy, Skopje, Macedonia 2Smelter Zletovo, Veles, Macedonia
Prejem rokopisa - received: 1997-10-01; sprejem za objavo - accepted for publication: 1997-10-21
In several thermal povver plants in operation in the Republic of Macedonia a substantial quantity of ash is produced by oil burning. Ashes are considered as highly hazardous for the environment due to their fine particle size. On the other hand, analyses carried out so far, indicate appreciable contents of vanadium, gallium, beryllium etc. in the ashes.
Key words: oil ashes. V2O5, leaching, effect of temperature and solution composition, activation energy of leaching
V Makedoniji obratuje več termoelektrarn, kjer pri zgorevanju olj nastaja pepel, ki je nevaren za okolje zaradi drobnozrnatosti. Po drugi strani pepel vsebuje pomembne količine vanadija, galija, berilija itd.
Ključne besede: oljni pepel, V2O5, luženje, vpliv temperature in sestave raztopin, aktivacijska energija luženja
1 INTRODUCTION
Investigations presented in this paper are aimed to ex-amine the possibility of hydrometallurgical treatment of ashes, produced with burning of fuel in povver and met-allurgical plants. The topics of the present investigations are the recovery of vanadiumpentoxyde as value compo-nent and the utilization of dust vvhich is an ecological problem. The investigations of the hydrometallurgical treatment of ashes vvere aimed to determine the vvorking conditions and process lavvs of leaching of vanadiumpen-toxyde in solution. The purification of V2O5 solution and its concentration of V205 is obtained vvith liquid-liquid extraction with D2EHPA (DI - 2 etil heksil phosphoric acid).
The effects of temperature (298 - 373 K), phase ratio (S/L : 1/50 - 1/5), concentration of H2SO4 in solution (0,5 ; 1 ; 1,5) mol/dm3, vvere investigated by constant particle size (-0,074 mm 100 %), velocity of mixing 8000 rev./min and leaching time 3 hours.
Experimental results shovving the influence of temperature, concentration of H2SO4 and phase ratio on V205 leaching are shovved on figures 2, 3, 4.
2 RESULTS AND DISCUSSION
The kinetics shovvs that by the maximal investigated temperature of T = 373 K and the follovving conditions S/L 1/50, H2SO4 1 mol/dm3 in the first 30 min of leaching 67,4% V205 is dissolved. Prolonging the leaching time is vvithout significant influence on volume of V2O5 in solution. Changes of concentration of H2SO4 (0,5 - 1,5 mol/dm3), of phase ratio (1/50 - 1/5) affect by constant temperature (343 K) also in the first period the V205 leaching efficiency.
A leaching activation energy Ea = 24,8 kJ/mole vvas determined through Arhenius analysis of the kinetics curves in figure 2.
Figure 1: Apparatus for leaching Slika 1: Naprava za izluževanje
Figure 2: Kinetics of V2O5 leaching for different temperatures Slika 2: Kinetika izluževanja V2O5 za različne temperature
•	373 K
•	3(3 K x30K
•	3?i K O 313 k »2MK
Figure 3: Kinetics of V2Os leaching for different concentrations of H2S04
Slika 3: Kinetika izluževanja V205 za različne koncentracije H2S04
Figure 7: Effect of concentration D2EHPA on coefficient of distribution D(V205) (Cjniliai = 0,4 mol/dm3)
Slika 7: Vpliv koncentracije D2EHPA na razdelitveni koeficient
D(V205) (Cza&lna = 0.4 mol/dm3)
0,1 M D2EHPA -O-0.2M 02EHPA —*— 0.4M 02 E HPA —0.6M 02EHPA
X	-1«5
A	-1:10
O	
O	-1:30
log cD2 EHPA
Figure 8: Log-log dependence of D(V205) and (D2EHPA) for different concentrations of HC1 (Cjniuai = 0,2 mol/dm3) Slika 8: Log-log odvisnost med D(V205) and (D2EHPA) za različne koncentracije HC1 (Czačetna = 0.2 mol/dm3)
log CD2 EHPA
Figure 4: Kinetics of V2Os leaching for different phase ratios Slika 4: Kinetika izluževanja V1O5 za različna razmerja faz
-s ----—
vo	}00	VO	V0	V0
A/T » 103
Figure 5: Graph of variables in Arhenius presentation Slika S: Odvisnosti v Arhenius predstavitvi
Figure 6: Effect of concentration D2EHPA on coefficient of distribution D(V205) (Cinitiai = 0,2 mol/dm3)
Slika 6: Vpliv koncentracije D2EHPA na razdelitveni koeficient D(V205) (Czagetna = 0.2 mol/dm3)
Figure 9: Log-log dependence of D(V205) and (D2EHPA) for different concentrations of HCl (Cj„jtjai = 0,4 mol/dm3) Slika 9: Log-log odvisnost med D(V2Os) in (D2EHPA) za različne koncentracije HCl (C2ačema = 0.4 mol/dm3)
The experimental investigation of liquid-liquid ex-traction using D2EHPA was carried out vvith initial con-centrations of V2O5 of 0,2 mol/dm3 and of 0,4 mol/dm3. In the tests sulfate solutions vvere used and the liquid-Iiq-uid extraction investigated as function of the follovving parameters:
a)	pH of solution: 1 ; 2 ; 4 ; 6 ; 8 ; 10 mol/dm3
b)	Concentration of D2EHPA: 0,1 ; 0,2 ; 0,4 ; 0,6 mol/dm3
3 RESULTS AND DISCUSSION
The experimental results shovving the coefficient of distribution DCV2O5) and the level of extraction ECV2O5) as a function of parameters a) and b) are given in table 1 and 2 and figure 6 and 7.
The analyses of the experimental data shovv by determined changes of the coefficient of distribution and level of extraction V2O5 as a function of pH an intial period of
decreasing grade of extraction vvhile by increasing of pH, the extraction efficiency of V205 is increased.
In logarithmic presentation the functions are straight lines vvhich slopes represent the solvent coefficients. In figure 8 and figure 9 the line slope have a tangents value of 2. It is concluded that vanadium vvill be recov-ered vvith a phase ratio CD2EHPA/LPhase = 2. With increasing the pH solutions until 10 mol HC1 the slope is tangent decreased to 1, 2 and in this čase extraction vvill be real-ized vvith a ratio phase D2EHPA/LphaSe =1:1.
4 REFERENCES
'A. N. Zelikman, T. M. Voldman, A. B. Beloevsija: Teorija gidrometalurgicheskih procesov Moskva, Metalurgija, 1983 2 Processing of petroleum coke for recovery vanadium, Hazen Research Inc. 4601 Indiana str. Golden C.O. 80403, USA, 1986 3O. B. Michesen: Recovery of vanadium from dust in the aluminum industry, Institute for energy technology P.O. 40 Norway, 1987 "N. Nacevski, F. Popovska, B. Nikov: Extraction of indium from sul-phate solutions vvith D2EHPA solutions; Journal de Physique III, 5, (1995) nov.