**4. Current and novel recovery processes for germanium**

Several processes have been recommended for Ge recovering based on its content, chemical species, and mineral phases that are present in by-products from Zn, Cu, and Pb ores processing and from coal combustion and gasification. In general, hydrometallurgical processes are favored, because almost all Ge extracted is mainly concentrated by processes based on mass transfer operations. Nevertheless, it is difficult to find extractants which meet the following characteristics: (i) selective, (ii) cost-effective, (iii) eco-friendly, and (iv) commercially available. In the next sections, the authors aboard main extraction methods used for the recovery of Ge from different sources and problems associated.

### **4.1. Recovery of germanium from Zn ore processing**

Nowadays, Zn ore processing is the main source of Ge as Zn ores have large and recoverable quantities of Ge. Zinc refinery residues, which are the typical by-products of hydrometallurgical zinc processes, usually contain between 0.2–0.5 wt% Ge and 0.3–0.4 wt% Ga with Zn, SiO<sup>2</sup> , Cu, Fe, and Pb as the main components [39, 40]. However, on a global scale, as little as 3% of the Ge contained in Zn concentrates is recovered since it can also have a negative impact on Zn recovery, detracting from the core business for refineries [20, 41]. As a consequence, except the Chinese refineries, only two Zn refineries currently extract Ge as part of their operations [36].

Several studies have been conducted on the behavior of Ge for the effectiveness of its recovering from by-products and residues of Zn processing [23, 42–45]. In 1987, a reductive SO<sup>2</sup> leaching process as an alternative for Ga and Ge recovery from Zn leaching residue was investigated [42]. Only 57% of Ge was extracted, which was mainly attributed to the formation of silica-germanium gel; H<sup>4</sup> GeO<sup>4</sup> and H<sup>4</sup> SiO<sup>4</sup> were shown to hydrolyze the mixed polymers [46–48]. A higher yield for Ge was observed with an alkaline process used to treat Zn refinery residues. However, the authors also detected that Si, Pb, and Al hinder the recovery and purification of Ge [44, 49]. Recovery of Ge from zinc refinery residues has more frequently been carried out by leaching with H<sup>2</sup> SO<sup>4</sup> being the resulting solution treated with solvent extraction (SX). Currently, synergistic SX (SSX) has been proved to increase the yield of Ge recovery and purification. Some of SX and SSX processes for Ge recovery studied are summarized in **Table 3** [50–58].

Other SX systems consisting of LIX 63 and D2EHPA, M2EHPA, and OPAP were also devel-

**Extractant Main issues of process Reference**

• High concentration of NaOH required for stripping

Solvent extraction (SX) Kelex 100 • Good separation of Ge from Zn, Cd, Ni, Co, and As

• Selective stripping

G315 • 95% Ge extraction efficiency at a low acidity

H106 • Ga and Ge co-extraction

• Poor phase separation in stripping

• H106 is not commercially available

• G315 is not commercially available

• High concentration of NaOH for stripping

LIX 63 + LIX 26 • Increased Ge extraction by addition of LIX 26 [53]

• Fast degradation of LIX 63 by the acidity of O.P acid

Synergistic solvent extraction (SSX) D2EHPA + TBP • TBP improves extraction efficiency and phase separation

LIX 63 • Good separation of Ge from Zn, Cu, Ni, As, Fe(II), and Cl • Low extraction efficiency • Slow extraction kinetics

Cu2+, and Fe2+ using a multistage counter-current process. In this case, over 95% of Ge4+ was

also proposed [54]. Indium was first separated from the solution using SX with 30% D2EHPA in kerosene, while Ge (97%) and Ga (95%) were co-extracted with the SSX system consisting of 20% D2EHPA and 1% YW100 in kerosene at low pH values. However, the authors found

The D2EHPA extractant was also developed for selective extraction of In3+ and Fe3+ and used

tation residue in a mini pilot plant scale. Recoveries of 91%, 94%, and 93% for In, Ga, and Ge,

The extractant G315 was tested to recover Ga and Ge from solutions containing Zn2+ (22.7 g/L),

phase ratio of 1:2. The extraction of Ge achieved 94.6%, but the structure or type of the extract-

solutions (75 g/L) containing Zn2+, arsenate, Cd2+, Sb (V), In3+,

SO<sup>4</sup>

SO<sup>4</sup>

leach solutions of Zn residue was

[50]

17

Germanium: Current and Novel Recovery Processes http://dx.doi.org/10.5772/intechopen.77997

[52, 53]

[55]

[56]

[57]

[58]

leach solutions of a cemen-

at an aqueous/organic (A/O)

SO<sup>4</sup>

oped to recover Ge4+ from H<sup>2</sup>

O.P: organophosphoric acid. Adapted from [43].

respectively, were achieved [55].

ant was not disclosed [56].

SO<sup>4</sup>

LIX 63 + O.P • Good selective Ge extraction and high efficiency

A technology for In3+, Ge4+, and Ga3+ recovery from a H<sup>2</sup>

**Table 3.** Summary of investigated SX or SSX systems for Ge recovery.

extracted using a mixture of 25% LIX 63 and 75% D2EHPA [52].

H106 for co-extraction of Ga3+ and Ge4+ from a solution from H<sup>2</sup>

Ge4+ (0.1 g/L), Ga3+ (0.3 g/L), and Fe3+ (2.2 g/L), in 40 g/L H<sup>2</sup>

that YW100 is not commercially available and the process is not eco-friendly.

Chelating extractant Kelex 100 was primarily used for the separation of Ge4+ from Zn, reaching Ge extraction 98% in a solution of 156 g/L H<sup>2</sup> SO<sup>4</sup> [50]. However, slow-phase disengagement and a high concentration of NaOH were required to strip the Ge4+ from the loaded organic solution.

Moreover, two studies achieved a good separation of Ge from Cu, Ni, As, Cl, and Fe2+ with a H<sup>2</sup> SO<sup>4</sup> solution of 100 g/L by the use of LIX 63 [51, 52]. In 1984, a SX system, consisting of LIX 63 and LIX 26, was used for the extraction of Ge from a solution containing Ge4+ (3.5 g/L), arsenite (0.8 g/L), and Fe3+ (1.5 g/L) [53]. Over 99% of Ge4+ was extracted with 99% (v/v) LIX 63 and 1% (v/v) LIX 26 in four stages at lower acidity (50 g/L H<sup>2</sup> SO<sup>4</sup> ) compared with using LIX 63 alone (>90 g/L H<sup>2</sup> SO<sup>4</sup> ).


**Table 3.** Summary of investigated SX or SSX systems for Ge recovery.

**4. Current and novel recovery processes for germanium**

of Ge from different sources and problems associated.

16 Advanced Material and Device Applications with Germanium

**4.1. Recovery of germanium from Zn ore processing**

GeO<sup>4</sup>

SO<sup>4</sup>

and 1% (v/v) LIX 26 in four stages at lower acidity (50 g/L H<sup>2</sup>

ing Ge extraction 98% in a solution of 156 g/L H<sup>2</sup>

SO<sup>4</sup> ). and H<sup>4</sup>

Zn, SiO<sup>2</sup>

their operations [36].

of silica-germanium gel; H<sup>4</sup>

carried out by leaching with H<sup>2</sup>

**Table 3** [50–58].

organic solution.

63 alone (>90 g/L H<sup>2</sup>

a H<sup>2</sup> SO<sup>4</sup>

Several processes have been recommended for Ge recovering based on its content, chemical species, and mineral phases that are present in by-products from Zn, Cu, and Pb ores processing and from coal combustion and gasification. In general, hydrometallurgical processes are favored, because almost all Ge extracted is mainly concentrated by processes based on mass transfer operations. Nevertheless, it is difficult to find extractants which meet the following characteristics: (i) selective, (ii) cost-effective, (iii) eco-friendly, and (iv) commercially available. In the next sections, the authors aboard main extraction methods used for the recovery

Nowadays, Zn ore processing is the main source of Ge as Zn ores have large and recoverable quantities of Ge. Zinc refinery residues, which are the typical by-products of hydrometallurgical zinc processes, usually contain between 0.2–0.5 wt% Ge and 0.3–0.4 wt% Ga with

as 3% of the Ge contained in Zn concentrates is recovered since it can also have a negative impact on Zn recovery, detracting from the core business for refineries [20, 41]. As a consequence, except the Chinese refineries, only two Zn refineries currently extract Ge as part of

Several studies have been conducted on the behavior of Ge for the effectiveness of its recovering from by-products and residues of Zn processing [23, 42–45]. In 1987, a reductive SO<sup>2</sup> leaching process as an alternative for Ga and Ge recovery from Zn leaching residue was investigated [42]. Only 57% of Ge was extracted, which was mainly attributed to the formation

[46–48]. A higher yield for Ge was observed with an alkaline process used to treat Zn refinery residues. However, the authors also detected that Si, Pb, and Al hinder the recovery and purification of Ge [44, 49]. Recovery of Ge from zinc refinery residues has more frequently been

(SX). Currently, synergistic SX (SSX) has been proved to increase the yield of Ge recovery and purification. Some of SX and SSX processes for Ge recovery studied are summarized in

Chelating extractant Kelex 100 was primarily used for the separation of Ge4+ from Zn, reach-

ment and a high concentration of NaOH were required to strip the Ge4+ from the loaded

Moreover, two studies achieved a good separation of Ge from Cu, Ni, As, Cl, and Fe2+ with

LIX 63 and LIX 26, was used for the extraction of Ge from a solution containing Ge4+ (3.5 g/L), arsenite (0.8 g/L), and Fe3+ (1.5 g/L) [53]. Over 99% of Ge4+ was extracted with 99% (v/v) LIX 63

SO<sup>4</sup>

solution of 100 g/L by the use of LIX 63 [51, 52]. In 1984, a SX system, consisting of

SiO<sup>4</sup>

, Cu, Fe, and Pb as the main components [39, 40]. However, on a global scale, as little

were shown to hydrolyze the mixed polymers

[50]. However, slow-phase disengage-

) compared with using LIX

being the resulting solution treated with solvent extraction

SO<sup>4</sup>

Other SX systems consisting of LIX 63 and D2EHPA, M2EHPA, and OPAP were also developed to recover Ge4+ from H<sup>2</sup> SO<sup>4</sup> solutions (75 g/L) containing Zn2+, arsenate, Cd2+, Sb (V), In3+, Cu2+, and Fe2+ using a multistage counter-current process. In this case, over 95% of Ge4+ was extracted using a mixture of 25% LIX 63 and 75% D2EHPA [52].

A technology for In3+, Ge4+, and Ga3+ recovery from a H<sup>2</sup> SO<sup>4</sup> leach solutions of Zn residue was also proposed [54]. Indium was first separated from the solution using SX with 30% D2EHPA in kerosene, while Ge (97%) and Ga (95%) were co-extracted with the SSX system consisting of 20% D2EHPA and 1% YW100 in kerosene at low pH values. However, the authors found that YW100 is not commercially available and the process is not eco-friendly.

The D2EHPA extractant was also developed for selective extraction of In3+ and Fe3+ and used H106 for co-extraction of Ga3+ and Ge4+ from a solution from H<sup>2</sup> SO<sup>4</sup> leach solutions of a cementation residue in a mini pilot plant scale. Recoveries of 91%, 94%, and 93% for In, Ga, and Ge, respectively, were achieved [55].

The extractant G315 was tested to recover Ga and Ge from solutions containing Zn2+ (22.7 g/L), Ge4+ (0.1 g/L), Ga3+ (0.3 g/L), and Fe3+ (2.2 g/L), in 40 g/L H<sup>2</sup> SO<sup>4</sup> at an aqueous/organic (A/O) phase ratio of 1:2. The extraction of Ge achieved 94.6%, but the structure or type of the extractant was not disclosed [56].

For the separation of Ge4+ from Zn2+, Ga3+, and Fe3+ in solutions with a high acidity (80 g/L H2 SO<sup>4</sup> ), a SSX system was also used [57]. The process consisted of 30% (v/v) D2EHPA and 15% (v/v) TBP. The extraction efficiency was 94.3% in two stages, and the strip efficiency was almost 100% using 250 g/L NaOH at an A/O phase ratio of 1:2.

A single contact system consisting of 10% LIX 63 and 2% Ionquest 801 to recover Ge from a synthetic leach solution of Zn refinery cementation residues was used [43]. Over 68% Ge4+ was extracted at a low pH at an A/O ratio of 1:1 and 40°C. Almost 73% Ge4+ was stripped with 0.5 M NaOH and 1.0 M Na<sup>2</sup> SO<sup>4</sup> .

A common disadvantage of the above SX or SSX processes for Ge4+ extraction is the use, for instance, of strong NaOH for stripping and of some reagents that are not commercially available. Therefore, more efficient and effective SX or SSX systems for the recovery of Ge are required using commercially available reagents.
