Organic acid | Acidolysis reactions | pKa | Complexolysis reactions |
---|---|---|---|
Gluconic |
C6H12O7 → C6H11O−7 + H+ | 3.86 | n[C6H11O−7] + Mn+ → M[C6H11O7]n |
Oxalic |
C2H2O4 → C2HO−4 + H+ C2HO−4 → C2O42− + H+ |
1.25 |
n[C2HO4−] + Mn+ → M[C2HO4]n n[C2O42−] + Mn+ → M2[C2O4]n |
Malic |
C4H6O5 → C4H5O5− + H+ C4H5O5− → C4H4O52− + H+ |
3.40 |
n[C4H5O5−] + Mn+ → M[C4H5O5]n n[C4H5O52−] + Mn+ → M2[C4H4O5]n |
Citric |
C6H8O7 → C6H7O7− + H+ C6H7O7− → C6H6O72− + H+ C6H6O72− → C6H5O73− + H+ |
3.09 |
n[C6H7O7−] + Mn+ → M[C6H7O7]n n[C6H6O72−] + Mn+ → M2[C6H6O7]n n[C6H5O73−] + Mn+ → M3[C6H5O7]n |
Microorganisms | Leaching agent (mg/L) | Temperature (°C) | Time (days) | RPM | Pulp density % (w/v) | Recovery (%) | References |
---|---|---|---|---|---|---|---|
Mixed fungal cultures: |
Oxalic 1022.4 |
30 | 27 | 300 | 8 | 56.1 Cu |
[ |
Citric 8131, 8064 |
Room temperature | 21 | 120 | 0.092 | 98.57 Zn |
[ |
|
Less than 14000 of gluconic acid, less than 4000 of citric and oxalic acid, less than 3000 of malic acid | 30 | 30 | 130 | 1 | 100 Li |
[ |
|
Citric 5237 |
30 | 15 | 130 | 1 | 100 V |
[ |
|
Kombucha-consortium(the bacterium |
Gluconic 25500 |
Room temperature | 14 | 300 | 2.8 | (stationary bioleaching) 5.2 of REE |
[ |
(shaken-mode bioleaching) 7.9 of REE | |||||||
Oxalic 17185 |
60 | 7 | 130 | 9 | 83 V |
[ |
|
Gluconic 2126 |
30 | 30 | 130 | 2 | 69.8 Al |
[ |
Organic acids (OA) | Inorganic acids (IA) | References |
---|---|---|
Less emission of hazardous gases | High emission of sulfur, chloride, and nitrous oxides | [ |
Serve for soil nutrient acquisition, mineral weathering | Can lead to high consumption either of water or chemicals | [ |
Less risky manipulation during the process. | Risky manipulation during the process. | [ |
Biodegradable | Non-biodegradable | [ |
Delay the corrosion of equipment | Cause prompt corrosion of equipment | [ |
Can be used more than once in metal recovery processes | Cannot be reused in metal recovery processes | [ |
Are costlier than IA, but the process is considered cost-effective due to the environmental impact | Have low cost, but the process is not considered cost-effective due to environmental impact | [ |
Solely act as leaching agents; hence, separation nd purification are still needed | Solely act as leaching agents; hence, separation and purification are still needed | [ |
Microorganisms | Leaching agent (mM) | Temperature (°C) | Time (days) | RPM | Pulp density (% w/v) | Recovery (%) | References |
---|---|---|---|---|---|---|---|
Mixture of malic, gluconic and acetic acids < 18 for both direct and indirect bioleaching | 30 | 18 | 120 | 1 | (direct bioleaching) |
[ |
|
2 | (indirect bioleaching) |
||||||
Non-characterized supernatant | 37 | 20 | 150 | 2 | 79 Mn | [ |
Microorganisms | Leaching agent (mM) | Temperature (°C) | Time (days) | RPM | Pulp density (% w/v) | Recovery (%) | References |
---|---|---|---|---|---|---|---|
Gluconic < 30 | 30 | 1 | 150 | 1.5 | RPP |
[ |
|
FCC |
|||||||
Not reported | 30 | 2 | 150 | 1 | 8285.3 mg/kg V |
[ |
|
5 | 29.9 mg/kg As |
||||||
Citric and Gluconic < 98 | 30 | 60 | 130 | 1 | 3% La | [ |
|
3 | 52% La | ||||||
5 | 33% La |