Recovery of Germanium from Aqueous Solutions by Ion-Exchange

Ind. Eng. Chem. Res. 2010, 49, 4817–4823

4817

Recovery of Germanium from Aqueous Solutions by Ion-Exchange Extraction of Its Catechol Complex Fa´tima Arroyo Torralvo,* Constantino Fernańdez-Pereira, and Marıá C. Campanario Departamento de Ingenierıá Quı´mica y Ambiental, Escuela Superior de Ingenieros de SeVilla, Camino de los Descubrimientos, s/n. Isla de la Cartuja, 41092 SeVilla, Spain

The paper is concerned with the recovery of germanium from dilute aqueous solutions. The method is based on the sorption of the selective complex formed by catechol with germanium onto low-cost anionic resins. Experimental investigations were undertaken using conventional quaternary ammonium macroporous resins: Amberlite IRA-900 and IRA-958. The influence of pH, metal concentration, and amounts of resin and catechol on the sorption capacity were investigated. For a proper set of experiments, a statistical technique such as a response surface methodology (RSM) has been used. For the investigation of the exchange equilibrium, the experimental data were analyzed using the Langmuir, Freundlich and Dubinin-Radushkevich equations, the Freundlich isotherm in general constituting a better fit. The uptake of the germanium complex by the ionexchange resins was reversed by acid and neutral solutions. The results obtained showed better performance for IRA-900 than IRA-958, measured in terms of global recovery yields (retention and elution). 1. Introduction The concentration of germanium in the earth’s crust is estimated in the range of 1-7 ppm1 but it is widely dispersed in nature, most of it in association with zinc and its minerals that nowadays are the main source of “new” germanium. The uses for germanium in novel and high technological industrial applications have considerably increased its price in the last year. As high-germanium raw materials are available only in restricted quantities it is necessary to process raw materials which are low in germanium, generally using hydrometallurgical processes. The aqueous solutions resulting from the leaching of these raw materials contain small amounts of germanium and considerable quantities of other materials. Different processes have been used for enriching germanium and separating it from other elements contained in leachates, such as As, Mo, Ni, Sb, V or Zn, including precipitation with tannin,2 distillation3 of GeCl4, flotation,4,5 adsorption onto activated carbon,6,7 precipitation,8 solvent extraction8–11 (SX), and sorption onto chelating exchange resins.12,13 Some of these methods are based on germanium complexation with catechol (CAT), but no ion-exchange method related to the germanium and catechol complex (Ge-CAT) has been described before. The structure of the Ge-CAT complex is shown in Figure 1. The formation of the complex14 at pH > 4 is described by eq 1. Ge(OH)4o + 3C6H4(OH)2 T Ge(C6H4O2)32- + 2H+ + 4H2O (1)

the selective extraction of germanium using resins that contain the appropriate functional groups.12,13 There are two ways to obtain an ion-exchange resin with functional groups: to incorporate the functional group during the polymerization or to introduce the functional groups on the matrix after the polymerization, by means of specific chemical reactions. For example, there are commercial resins recommended for the germanium extraction, such as Sephadex and N-methylglucamine,12 although some of them present some problems of selectivity, or those made by Hayashi et al.17 that synthesize chelatant polystyrene resins containing diol groups or chitosan type groups with good yields. Kunio et al.18 have patented a process for the recovery of germanium from diluted solutions using a resin loaded with tannin. In similar work by Ziegenbalg and Scheffer,19 different complexing agents containing hydroxyls groups are used. The main problem of these chelating resins is their high price and slow adsorption kinetics. Conventional strongly basic resins are described as not suitable to separate germanium(IV) in a selective way.20 However, in this paper the utilization of conventional anionic resins has been tested to extract germanium from an aqueous solution successfully. To achieve the selective extraction of germanium, its anionic catechol complex is first formed, and after that the complex is adsorbed onto the anionic resin. In this paper, two quaternary ammonium anion exchange resins in chloride form (IRA-900 and IRA-958, from RohmHaas) were studied. Ion-exchange resins in general have a major

In relation to ion-exchange methods, both Inukai et al.15 and Harada et al.12 have demonstrated that germanium(IV) is not retained on conventional chelating resins for metallic cations, since in aqueous solutions, germanium is not in cationic form, but in the oxoacid (Ge(OH)4) or oxoanion (GeO(OH)3- or GeO2(OH)22-) forms, depending on the solution pH. The same authors indicate that strongly basic anionic resins would extract the germanium in solution, but not in a selective way. Because germanium forms complexes with poly ol compounds16 and saccharides, some research groups have studied * To whom correspondence should be addressed. Tel.: +34954487282. Fax: +34-954486082. E-mail: [email protected]; [email protected].

Figure 1. Germanium-catechol structure.

10.1021/ie901020f  2010 American Chemical Society Published on Web 04/13/2010

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Ind. Eng. Chem. Res., Vol. 49, No. 10, 2010

Table 1. Amberlite IRA 900 and IRA 958 Properties [Data from Rohm and Haas] AMBERLITE IRA900 Cl-

AMBERLITE IRA958 Cl-

macroreticular strongly basic quaternary ammonium total exchange capacity 1.0 meq/ml moisture holding capacity 58 to 64% shipping weight 44 lbs/ft3 particle size: 16 to 50 mesh (US std screens) screen analysis: 3% max. on 16 mesh (US std screens) 0.5% maximum thru 50 mesh mean size 0.65 to 0.82 mm

macroreticular strongly basic quaternary ammonium total exchange capacity 0.8 meq/ml minimum moisture holding capacity 66 to 72% shipping weight 45 lbs/ft3 particle size: 16 to 50 mesh (US std screens) screen analysis: 5% max. on 16 mesh (US std screens) 1% maximum thru 45 mesh mean size 0.63 to 0.85 mm

affinity with ions of a higher atomic mass. Therefore, in an aqueous solution in which many metals are present, though in theory the resin might absorb any metal, and when the germanium-catechol complex is present, its anionic nature along with its high molecular mass implies (in principle) an advantage in reaching a higher selectivity for germanium.21 The reaction of exchange between the resin and the germanium-catechol complex is probably well represented by 2RzNR3Cl + GeCAT23 T (RzNR3)2GeCAT3 + 2Cl (2)

where Rz is the resin polymer matrix. Traditional experimental techniques, such as the one-factorat-a-time method, do not depict the combined effect of all factors involved in the ion-exchange process,22 and moreover they do not guarantee the determination of optimal conditions. However, with a properly designed set of experiments, better information can be obtained in less time.23 The response surface methodology (RSM) is a statistical technique for designing experiments that has been found to be a useful tool to study the interaction of two or more variables.24 This statistical technique has been extensively applied to many areas of biotechnology,25 but it is not usual in ion-exchange or in hydrometallurgy studies. 2. Materials and Methods 2.1. Materials. All the reagents used in this study were analytical grade reagents. IRA-900 and IRA-958 in chloride form were obtained from Rohm-Haas. Both resins were chosen among the conventional strongly basic anionic resins with pore size sufficiently high to absorb the germanium-catechol complex. The properties of the resins are given in Table 1. 2.2. Ion-Exchange Procedure. The adsorption tests were performed in 150 mL flasks in which 100 mL of fertile solutions were placed and maintained in contact with the resin at constant temperature using a shaker. The fertile solution was prepared by adding catechol to the germanium-bearing standard solution and NaOH 0.5 M in order to adjust the pH. Fertile solution/ resin ratios, CAT/Ge molar ratio, pH, and contact times were varied throughout the study. After the contact, the resin and residual solution (raffinate) were separated by filtration through a membrane filter (0.45 µm). Raffinates were analyzed for germanium content by atomic absorption spectrometry (AAS, model 3100 Perkin-Elmer) and inductively coupled plasma atomic emission spectroscopy (ICP-AES, model ARL-3410 Fisons). The metal retained in the resin was obtained by a mass balance. The resins were washed with doubly distilled water before the eluting stage in which pregnant resins and eluting

Table 2. Design Matrix Evaluation for Response Surface Quadratic Model run

replicates

coded C

coded R

coded G

actual C

actual R

actual G

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

1 1 -1 -1 1 1 -1 -1 1.682 0 0 -1.682 0 0 0 0 0 0 0 0

1 -1 1 -1 1 -1 1 -1 0 1.682 0 0 -1.682 0 0 0 0 0 0 0

1 -1 -1 1 -1 1 1 -1 0 0 1.682 0 0 -1.682 0 0 0 0 0 0

7.78 7.78 4.22 4.22 7.78 7.78 4.22 4.22 9.00 6.00 6.00 3.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00

3.39 1.61 3.39 1.61 3.39 1.61 3.39 1.61 2.50 4.00 2.50 2.50 1.00 2.50 2.50 2.50 2.50 2.50 2.50 2.50

83.78 36.22 36.22 83.78 36.22 83.78 83.78 36.22 60.00 60.00 100.00 60.00 60.00 20.00 60.00 60.00 60.00 60.00 60.00 60.00

solution were contacted as in the sorption stage. Samples containing ethanol were measured for Ge using the phenylfluorone colorimetry method.26 2.3. Design of Experiments (DOE). The response surface methodology (RSM) technique has several designs; in this study a five-level, three-variable central composite rotatable design (CCRD) was employed. The variables chosen for the study were C, amount of catechol (as CAT/Ge molar ratio), R, resin dosage (as resin/Ge equivalent ratio) and G, initial Ge concentration (mg/L). The space of interest was defined by the following ranges: C, 3-9 (molar ratio); R, 1-4 (equivalent ratio); and G, 20-100 (mg/L). The lowest values of catechol and resin dosages of the ranges are based on stoichiometric ratios and the highest are based on preliminary experiments and manufacturer recommendations. The CCRD consisted of 2 × 3 factorial runs with 2 × 3 axial runs and 6 center runs (six replicates), so a total of 20 experiments were required for each resin. Table 2 shows the design matrix in which the variables, the coded levels used, and the real values are given. The general design of the trials to be conducted is expressed in coded terms for statistical calculations (eqs 3-5). Gcod )

Greal - 60 23.7812

(3)

Ccod )

Creal - 6 1.7838

(4)

Rreal - 2.5 0.9818

(5)

Rcod )

The experimental data obtained in the tests were fitted by a second order polynomial equation in order to determine if any relationship between the factors and the response variables existed. The equation has the following form: 3

EGe(%) ) ao +

∑ i)1

3

aixi +

∑

i,j)1

3

aiixii +

∑ a xx

ij i j

(6)

i,j)1

where EGe is the predicted response (germanium extraction yield), ao is the offset term, ai is the linear coefficient, aii is the


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Table 3. Equilibrium Tests for IRA-900 and IRA-958 IRA 900

IRA 958

R coded

R/Ge

resin (mg)

0.00 0.15 0.30 0.45 0.60 0.75

2.50 2.63 2.77 2.90 3.04 3.17

269.42 283.84 298.25 312.67 327.09 341.50

Ge absorbed (%)

R codif

R real

resin (mg)

Ge absorbed (%)

99.49 99.54 99.56 99.67 99.74 99.75

0.00 0.15 0.30 0.45 0.60 0.75

2.50 2.63 2.77 2.90 3.04 3.17

338.84 357.00 375.10 393.24 411.37 429.50

98.30 98.40 98.57 98.83 98.94 99.14

first-order interaction effect term, aij is the cross-product coefficient, and xi and xj are the level of coded variables. The software Stat-Ease Design-Expert (version 7.0.3) was used for experimental design and response surface design and analysis. 2.3. Equilibrium Studies. A common way to represent the equilibrium in ion-exchange systems is through the isotherm equations27 that represent the distribution between solid and liquid phases at equilibrium and illustrate the type of interaction between the germanium complex and the resin in this case. The most important adsorption isotherms come from the Freundlich and Langmuir adsorption models, and their equations are shown in eqs 7 and 8. Both isotherms were used for determining the capacity and affinity of the adsorption process at equilibrium. Dubinin28 has reported that the isotherm curve is related to the porous structure of the resin thus proposing a different isotherm in the form shown by eq 9. log qe ) log KF +

1 log Ce Fr

(7)

1 1 1 ) + qe QM KLQMCe

(8)

ln(qe) ) ln(qo) + (-βε2)

(9)

where Ce is the equilibrium solution concentration (mg of Ge/L of solution), qe is the germanium adsorbed at equilibrium (mg of Ge/g of resin, also calculated by eq 10). The terms KF and Fr are related to the adsorption capacity and intensity, respectively. QM is also the adsorption capacity (mg/g), and KL is related to the energy of adsorption. β is the activity coefficient and ε is the Polanyi potential given by eq 11. qe )

(Co - Ce)V Wr

(

ε ) RT ln 1 +

1 Ce

(10)

)

(11)

where V is the volume of solution (L), Wr is the weight of resin used (g), R is the universal gas constant, Co is the initial solution concentration (mg/L), and T is the absolute temperature. Equilibrium data were obtained by shaking different amounts of both resins (Table 3) with equal volumes (100 mL) of a standard solution containing 60 mg/L of germanium (Gcoded ) 0) at room temperature for 24 h. CAT/Ge molar ratio of 9 (IRA900) and 6 (IRA-958), pH ) 7 and contact time of 8 h were used to ensure the equilibrium. The amounts of resin and catechol were chosen on the basis of previous experiments inside the range of maximum germanium extraction. After equilibrium, the resin and solution were separated by filtration, and the metal content of the solution was determined by AAS. The amount

Figure 2. Germanium extraction yields and log Kd for different initial pH with IRA-900 and IRA-958 resins. Table 4. Statistical Significance of Model (F-Test) and the Analysis of Variance (ANOVA) source

sum of squares

df

mean value p-valueprob square F >F

model IRA-900 pure error correlation total

599.49 3.15 641.89

9 5 19

66.61 0.63

15.71 25), and the catechol amount being the most important variable in case of the resin IRA-958 (coefficient ≈ 7). It was found that the retention of germanium increased as the resin amount increased up to an equivalent ratio of resin/ germanium of 2.5-3, slightly superior to that recommended by the manufacturer (ratio ) 2), and above this value the sorption yield diminished slightly (from 99 to 95%). These values are independent of the quantity of catechol added (coefficients 0.28 in the equation) in the range of study. A similar behavior can be seen in the representation of the extraction yield versus the quantity of resin and the initial content of germanium: the yield remains approximately constant

Figure 6. Freundlich fit of experimental values and linearized equations.

Figure 7. Langmuir fit of experimental values and linearized equations.

Figure 8. Dubinin-Radushkevich fit of experimental values and linearized equations.

for the whole range of initial concentrations of germanium studied, reaching a maximum when an equivalent ratio of resin/ germanium of 2.5-3 was used. The behavior of resin IRA-958 was different from resin IRA900 (see Figure 5). A synergic effect existed among the resin and catechol amounts added to the solution (coefficients 0.19 and 0.60 for IRA-900 and 958, respectively) so that the maximum retention yield was achieved for an equivalent ratio of resin/germanium of 2, and a proportion catechol/germanium ) 6 (double of the stoichiometric amount). It is also possible to observe certain synergy between the resin amount and the initial germanium content, with maximum yield values for concentrations of germanium around 100 mg/L, diminishing the adsorption for more dilute solutions. 3.4. Process Optimization. The optimum germanium sorption yield can be estimated for a fixed initial germanium content using the ANOVA program, and some results are shown in Table 5 for both resins. This information is useful for applying the method to different solutions, since it allows estimation of the optimum extraction conditions for each initial concentration. 3.5. Equilibrium Studies. The sorption data obtained were fitted to Freundlich, Langmuir, and Dubinin-Radushkevich isotherm models and the obtained linearized equations are shown for IRA-900 and IRA-958 in Figures 6-8. All models satisfactorily represent the adsorption process (showing high correlation coefficients) although it seems that the Freundlich isotherm constitutes a better fit, which might be due to a heterogeneous distribution of the active sites on the resin surface, consisting in sites with different sorption potentials. The Langmuir capacity (QM), Freundlich capacity (KF), Fr, KL, β, and qo parameters were calculated as were the

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Table 6. Composition of Original Leachate and Solutions after Contact (mg/L). Retention Capacity of Each Element (mg of Element/g of Resin) R/Ge

CAT/Ge

Ni, 37.71 mg/L

Ge, 35.59 mg/L

Sb, 19.13 mg/L

2.5 1.8 1.1

5.0 4.0 3.0

29.91 (3.88) 33.33 (2.55) 31.62 (12.45)

2.63 (17.39) 13.99 (14.03) 16.19 (42.47)

14.50 (2.33) 18.20 (0.43) 17.91 (2.12)

2.5 1.8 1.1

5.0 4.0 3.0

29.14 (11.25) 31.87 (7.42) 32.86 (6.03)

2.42 (45.83) 11.40 (32.23) 8.75 (36.94)

14.36 (6.31) 17.85 (1.40) 17.91 (1.32)

As, 18.22 mg/L

Zn, 2.04 mg/L

Mo, 0.43 mg/L

V, 0.33 mg/L

Co, 0.25 mg/L

1.59 (0.23) 1.72 (0.19) 1.01 (2.25)

0.02 (0.22) 0.14 (0.19) 0.18 (0.55)

0.07 (0.14) 0.10 (0.15) 0.17 (0.35)

0.22 (0.02) 0.24 (0) 0.23 (0.05)

1.59 (0.60) 1.72 (0.41) 1.73 (0.40)

0.09 (0.47) 0.29 (0.19) 0.02 (0.57)

0.10 (0.31) 0.19 (0.19) 0.07 (0.36)

0.21 (0.05) 0.23 (0.03) 0.24 (0.01)

IRA-900 17.68 (-) 15.41 (-) 13.22 (-)

IRA-958

Table 7. Germanium Recovery. Eluting (Stripping) Agents Tested and Elution Yields eluate

IRA-900

IRA-958

1.5 M HCl 1 M HCl 1 M NaOH 1 M NaCl 1.5 M NaCl 1 M HCl in 50% ethanol 1.5 M HCl in 50% ethanol 2 M HCl in 50% ethanol 1 M H2SO4 in 50% ethanol 1.5 M H2SO4 in 50% ethanol 2 M H2SO4 in 50% ethanol

63% 49% 39% 38% 52% 94% 93% 98% 75% 73% 77%

61% 41% 32% 22% 33% 89% 88% 85% 71% 72% 72%

and the last one using low ratios (1.1 and 3). In all the cases the pH was adjusted to 7 with 1 M NaOH. The metal contents of the solutions obtained after the contact and resin removal is also shown in Table 6, as well as the retention capacity of each element (expressed in mg of the element/g of resin). Germanium was quantitatively extracted when high ratios of catechol/germanium and resin/germanium were used (92.5% and 93.5% for IRA-900 and 958, respectively) which agreed with the results obtained with the Ge-standard solutions. The experimental affinities that both resins showed for the elements in solution were (see Table 6) Ge . Ni > Sb > Mo > V > As > Zn > Co

equations and coefficient correlations, and they are shown in Figures 6-8. The Freundlich type isotherm curve is also generally observed in sorbents with a wide pore size distribution range, which confirmed that interaction between resins and germanium-catechol chelate was the result of complex interactions including physical and chemical mechanisms. The values of the Freundlich constants (Fr) in the range of 0-10 (3.69 and 3.15 for IRA900 and IRA-958, respectively) suggested the favorable sorption of germanium-catechol complex with both resins. The smaller value of (1/Fr) for resin IRA-900 indicated a stronger bond between complex and resin. To predict the adsorption efficiency of the adsorption process, the equilibrium dimensionless parameter r was determined by the following equation:29 r)

16.57 (-) 14.67 (-) 15.03 (-)

1 1 + bCo

(17)

where Co is the initial concentration and b is the Langmuir isotherm constant. Values of r < 1 represent favorable adsorption. The r-value for the initial concentration of 50 mg/L was found to be 0.18 and 0.06 for IRA-900 and IRA-958, respectively, at room temperature. These values indicated favorable adsorption for Ge initial contents greater than 1 mg/L for IRA900 and greater than 0.1 mg/L for IRA-958. 3.6. Selectivity. The possibility of a selective sorption of germanium from an aqueous solution containing other elements was also checked using the method described above. An ion exchanger shows preference for highly charged ions, for smaller solvated ions, and for ions which interact more strongly with the matrix.21 To check the selectivity of the proposed method, different resin and catechol amounts were added to real Ge solutions, that is, the leachate obtained by contacting a Ge-rich coal fly ash with water at room temperature. The composition of the original leachate appears in Table 6. Three different tests were performed with each resin, one using high R/Ge and CAT/Ge equivalent and molar ratios (2.5 and 5, respectively), another at intermediate levels (1.8 and 4)

Results of both resins coincided with small deviations. These results can be more or less predictable for those elements normally found in aqueous solutions as oxo-anions, such as Sb, As, Mo, or V. The case of nickel is more unusual. However, this behavior could be due to the formation of stable anionic complexes of nickel with catechol,30,31 which can promote the retention of this metal on both resins. In any case, the selectivity of the method was demonstrated since the retention of the possible interfering elements were on both resins at least 1 order of magnitude less than the germanium retention. 3.7. Germanium Recovery. Some eluting solutions to recover the Ge retained onto the resin were tested. Table 7 shows the tested agents and the yields of elution of germanium reached in each case after previous sorption tests were carried out using standard solutions. The best stripping agent was HCl in 50% ethanol for both resins. Best elution yields were achieved for IRA-900 with 2 M HCl (98%) and for IRA-958 with 1 M HCl (89%). HCl and NaCl solutions have the advantage that they allow the regeneration of the resin, leaving it again in chloride form ready for a new utilization. 4. Conclusions The present paper shows that a selective recovery of germanium from aqueous solutions in the presence of other metals such as arsenic, antimony, cobalt, vanadium, molybdenum, nickel, and zinc, using conventional ion-exchange absorbents (resins) is possible. The selective extraction was achieved by means of the formation of the catechol complex of germanium that is adsorbed onto an anionic resin. Finally, the germanium is eluted (stripped) of the resin using an eluting solution. The utilization of a complexant specific to germanium allowed extraction of the germanium in a selective way using common anionic resins with the consequent economic advantages. The process offers the possibility of choosing different eluent solutions that can be acidic or basic. A rotatable central composite design was applied to study the effect of the initial germanium content, catechol amount,


and resin dosage on sorption yield, and the value of the correlation factors (R2 ) 0.9333 and 0.9763) confirmed the effectiveness of the models. Equilibrium studies were performed and results were fitted using Langmuir, Freundlich, and Dubinin-Radushkevich models. The Freundlich isotherm provided the best correlation, so a heterogeneous distribution of sites was suggested. The value obtained for the Freundlich constant Fr showed the favorable sorption of the germanium-catechol complex, with both resins and the r-value indicating favorable adsorption for Ge initial contents greater than 1 mg/L for IRA-900 and greater than 0.1 mg/L for IRA-958. The selectivity sorption of germanium was also tested, and the following order of affinities was found: Ge . Ni > Sb > Mo > V > As > Zn > Co. Several eluting solutions were tested, but HCl in 50% ethanol was found to be the best agent for both resins. Elution yields were 98% for IRA-900 with 2 M HCl and 89% for IRA-958 with 1 M HCl. Further studies related to the recovery of germanium from coal fly ash leachates by this method, especially in relation to the elution step and resins regeneration, are currently being performed. Literature Cited (1) Adams, J. H. Germanium and Germanium Compounds. Metals Handbook, 10th ed.; ASM International: Materials Park, OH, 1990. (2) Moskalyk, R. R. Review of germanium processing worldwide. Miner. Eng. 2004, 17, 393. (3) Jandova, J.; Vu, H. Processing of germanium-bearing fly ash. Metall., Refract. EnViron. 2001, 107. (4) Hernandez-Exposito, A.; Chimenos, J. M.; Fernandez, A. I.; Font, O.; Querol, X.; Coca, P.; Garcia Pena, F. Ion flotation of germanium from fly ash aqueous leachates. Chem. Eng. J. 2006, 118, 69. (5) Matis, K. A.; Mavros, P. Recovery of metals by ion flotation from dilute aqueous solutions and foam/froth flotation: Part II. Removal of particulate matter. Sep. Purif. Methods 1991, 20, 1. (6) Marco Lozar, J. P.; Cazorla Amoro´s, D.; Linares Solano, A. Procedimiento para la recuperacioń de germanio en disolucioń mediante carboń activo (Procedure for the recovery of germanium in solution using activated carbon). Patent ES2257181, 2006. (7) Marco-Lozar, J. P.; Cazorla-Amoro´s, D.; Linares-Solano, A. A new strategy for germanium adsorption on activated carbon by complex formation. Carbon 2007, 45, 2519. (8) Arroyo, F.; Font, O.; Fernańdez-Pereira, C.; Querol, X.; Juan, R.; Ruiz, C.; Coca, P. Germanium recovery from gasification fly ash: Evaluation of end-products obtained by precipitation methods. J. Hazard. Mater. 2009, 167, 582. (9) Arroyo, F.; Fernańdez-Pereira, C. Hydrometallurgical recovery of germanium from coal gasification fly ash. Solvent extraction method. Ind. Eng. Chem. Res. 2008, 47, 3186. (10) Arroyo, F.; Fernańdez-Pereira, C.; Querol, X.; Font, O.; Coca, P.; Chimenos, J. M.; Fernandez, A. I. Method for the recovery of germanium form IGCC fly ash. Patent WO2008/003808A1, 2008.

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(11) Menendez, F. J. S.; Menendez, F. M. S.; de La Cuadra Herrera, A.; Tamargo, R. M.; Lorenzo, L. P.; Valcarcel, M. R.; Fernandez, V. A. Process for the recovery of germanium from solutions that contain it. Patent US4886648, 1989. (12) Harada, A.; Tarutani, T.; Yoshimura, K. Spectrophotometric determination of germanium in rocks after selective adsorption on sephadex gel. Anal. Chim. Acta 1988, 209, 333. (13) Schilde, U.; Uhlemann, E. Separation of several oxoanions with a special chelating resin containing methylamino-glucitol groups. React. Polym. 1993, 20, 181. (14) Pokrovski, G.; Martıń, F.; Hazemann, J. L.; Schott, J. An X-ray absorption fine structure spectroscopy study of germanium-organic ligand complexes in aqueous solution. Chem. Geol. 2000, 163, 151. (15) Inukai, Y.; Chinen, T.; Matsuda, T.; Kaida, Y.; Yasuda, S. Selective separation of germanium(IV) by 2,3-dihydroxypropyl chitosan resin. Anal. Chim. Acta 1988, 2, 187. (16) Antikainen, P. J.; Malkonen, P. J. Chelation of germanic acid with some o-diphenols in aqueous solution. Suom. Kemistil. 1959, 32B, 179. (17) Hayashi, H.; Sound, H. I.; Kogyo, G. Method for recovering germanium from germanium-containing rock, Patent US 4525332, 1985. (18) Kunio, S., Akira, T., Hiroyuk, Y. Masahide, H. Shiyouzou, T. Kouzou, K. Method of recovery of germanium. Patent JP 60166225, 1985. (19) Ziegenbalg, G.; Scheffer, T. Process for the recovery of germanium values, Patent GB 933563, 1963. (20) Everest, D. A.; Popiel, W. J. Ion-exchange studies of solutions of tellurates. J. Inorg. Nucl. Chem. 1958, 6, 153. (21) Habashi, F. Handbook of ExtractiVe Metallurgy; Wiley-VCH: New York, 1997. (22) Diamond, W. J. Practical experiment designs for engineers and scientists; Lifetime Learning Publications: Belmont, CA, 1981. (23) Montgomery, D. C. Design and analysis of experiments, 6th ed.; John Wiley and Sons, 2005. (24) Tan, I. A. W.; Ahmad, A. L.; Hameed, B. H. Optimization of preparation conditions for activated carbons from coconut huso using response surface methodology. Chem. Eng. J. 2008, 137, 462. (25) Gode, F.; Pelhivan, E. A. Comparative study of two chelating ionexchange resins for the removal of chromium(III) from aqueous solution. J. Hazard. Mater. 2003, B1000, 231. (26) Arroyo, F.; Fernańdez-Pereira, C. Method for the recovery of germanium in solution by means of complexing and use of ion-exchange resins, Patent WO2009106660, 2009. (27) Vassilis, J. I.; Stavros, G. P. Adsorption, Ion Exchange, and Catalysis Design of Operations and EnVironmental Applications; Elsevier B.V.: Amsterdam, The Netherlands, 2006. (28) Dubinin, M. M. Generalization of the theory of volume filling of micropores to nonhomogeneous microporous structures. Carbon 1985, 23, 373. (29) Bouguerra, W.; Ben Sik Ali, M.; Hamrouni, B.; Dhahbi, M. Equilibrium and kinetic studies of adsorption of silica onto activated alumina. Desalination 2007, 206, 141. (30) Burriel, F.; Lucena, F.; Arribas, S.; Hernańdez, J. Quı´mica Analı´tica CualitatiVa; Paraninfo: Madrid, 1983. (31) Jameson, R. F.; Wilson, M. F. Thermodynamics of the interactions of catechol with transition metals. Part 11.1 Copper and nickel complexes of catechol. J. Chem. Soc., Dalton Trans. 1972, 23, 2614.

ReceiVed for reView June 29, 2009 ReVised manuscript receiVed March 16, 2010 Accepted March 28, 2010 IE901020F

Recovery of Germanium from Aqueous Solutions by Ion-Exchange

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