Gallium and Arsenic Recovery from Waste Gallium Arsenide by Wet Refined Methods

2011 ◽  
Vol 194-196 ◽  
pp. 2115-2118 ◽  
Author(s):  
Wei Ting Chen ◽  
Yung Chuan Chu ◽  
Jian Ming Wei ◽  
Lung Chang Tsai ◽  
Fang Chang Tsai ◽  
...  
Keyword(s):  
Gallium Arsenide ◽  
Ferrous Sulfate ◽  
Extraction Efficiency ◽  
Acid Leaching ◽  
Sulfate Heptahydrate ◽  
Nickel Copper ◽  
Leaching Solution ◽  
Semiconductor Fabrication ◽  
Removal Of Arsenic ◽  
Ferrous Sulfate Heptahydrate

This study was focused on the recovery of gallium arsenide (GaAs) from semiconductor fabrication sludge. Wet refined methods were applied to recover gallium (Ga) including acid leaching, purified isolation, electrolysis, and coagulation. The result showed that leaching Ga with nitric acid (HNO3) was more efficient than with sulfuric acid (H2SO4). GaAs could be leached with 4 N HNO3 to obtain 100% Ga+ and arsenic (As—). The pH was adjusted with sodium hydroxide (NaOH). Then, the solution was extracted by di(2-ethylhexyl) phosphoric acid (D2EHPA) and was back extracted by H2SO4. In this way, Ga extraction efficiency was 80%. At the end of the process, electrolysis was applied to recover Ga. The resulting electrolysis efficiency with nickel-copper was only 56% and its purity was 92%. To further increase the recovery of Ga, the leaching solution was adjusted to alkaline solution and was then electrolyzed with platinum-stainless steel. In this way, recovery and purity could be as high as 90% and 94%, respectively. The removal of arsenic was 86% when the leaching solution was added with ferrous sulfate heptahydrate (Fe2(SO4)3‧xH2O) to form iron arsenate (AsFeO4).

scholarly journals Thermal Behavior of Hydrated Iron Sulfate in Various Atmospheres

Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1084 ◽  
Author(s):  
Ndue Kanari ◽  
Nour-Eddine Menad ◽  
Etleva Ostrosi ◽  
Seit Shallari ◽  
Frederic Diot ◽  
...  
Keyword(s):  
Titanium Dioxide ◽  
Ferrous Sulfate ◽  
Room Temperature ◽  
Iron Sulfate ◽  
Huge Amount ◽  
Sulfate Heptahydrate ◽  
Pickling Process ◽  
Significant Temperature ◽  
Ferrous Sulfate Heptahydrate ◽  
Kinetic Features

Iron sulfate, in particular FeSO4·7H2O, is derived from titanium dioxide production and the steel pickling process. Regarding TiO2 manufacturing, the amount of the resultant FeSO4·7H2O can be as high as 6 tons per ton of produced TiO2, leading to a huge amount of ferrous sulfate heptahydrate, which is considered an environmental and economic concern for the titanium dioxide industry in European countries. The present paper focuses on the thermal treatment of ferrous sulfate (heptahydrate and monohydrate) samples under different conditions. Nonisothermal thermogravimetric (TG) analysis was used to study the behavior of iron sulfate samples at temperatures of up to 1000 °C in Cl2 + O2, O2, and N2 atmospheres. Results showed that the dehydration of iron sulfate heptahydrate in nitrogen started at room temperature and resulted in iron sulfate tetrahydrate (FeSO4·4H2O). The ferrous sulfate monohydrate (FeSO4·H2O) was formed at temperatures close to 150 °C, while the anhydrous ferrous sulfate (FeSO4) was obtained when the samples were heated in nitrogen at over 225 °C. The kinetic features of FeSO4 decomposition into Fe2O3 were revealed under isothermal conditions at temperatures ranging from 500 to 575 °C. The decomposition of iron sulfate was characterized by an apparent activation energy of around 250 kJ/mol, indicating a significant temperature effect on the decomposition process. The obtained powder iron oxide could be directed to the agglomeration unit of iron and the steelmaking process.

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