Ciminelli and Osseo-Asare, 1995; Lowson, 1982). Anderson (1951) reported 26 kJ/mol in the study of oxidation kinetics of galena (PbS) while Stenhouse and Armstrong (1952) reported an activation energy of 20 kJ/mol for the alkaline oxidation of pyrite. Koslides and Ciminelli (1992) suggested that during alkaline oxidation of sulphides, there is a change from chemical (activation energy > 40 kJ/mol) to diffusion (activation energy < 40 kJ/mol) control as the rate determining step when temperature is above 100°C This led them to conclude that the oxidation is a mixed controlled reaction.
Alkaline oxidation of arsenic bearing minerals
Arsenopyrite (FeAsS) is the most abundant arsenic containing sulphide mineral. As such, it will be the focal point …show more content…
Leaching of enargitite concentrate using sodium sulphide (Baláž et al., 2000). Alkaline leaching of enargitite using sodium hypochlorite under oxidizing conditions (Viñals et al., 2003).
Ruiz et al. (2014) used the former to investigate the selective leaching of arsenic from enargitite by alkaline digestion. The process consisted of alkaline digestion with concentrated Na2S-NaOH followed by water leaching. The dissolution of arsenic was observed to increase with an increase in both the temperature and caustic concentration. Yu et al. (2014) also reported similar effects of temperature and caustic concentration during extraction of arsenic from arsenic-containing cobalt and nickel …show more content…
(2013) conducted investigations of copper and selenium recovery from copper anode slimes. The process consisted of two hydrometallurgical steps; decopperization in sulphuric acid media and dissolution of selenium in caustic solution. Temperature caustic concentration, oxygen partial pressure and reaction time were all found to increase selenium dissolution. The caustic concentration was varied between 0.36 and 5 mol/L. Maximum selenium extraction was obtained with 4 mol/L caustic concentration. The maximum temperature of 90°C used in the investigation yielded the maximum selenium dissolution. The following reactions were proposed for the dissolution of selenium (Kilic et al.,
Alkaline oxidation of arsenic bearing minerals
Arsenopyrite (FeAsS) is the most abundant arsenic containing sulphide mineral. As such, it will be the focal point …show more content…
Leaching of enargitite concentrate using sodium sulphide (Baláž et al., 2000). Alkaline leaching of enargitite using sodium hypochlorite under oxidizing conditions (Viñals et al., 2003).
Ruiz et al. (2014) used the former to investigate the selective leaching of arsenic from enargitite by alkaline digestion. The process consisted of alkaline digestion with concentrated Na2S-NaOH followed by water leaching. The dissolution of arsenic was observed to increase with an increase in both the temperature and caustic concentration. Yu et al. (2014) also reported similar effects of temperature and caustic concentration during extraction of arsenic from arsenic-containing cobalt and nickel …show more content…
(2013) conducted investigations of copper and selenium recovery from copper anode slimes. The process consisted of two hydrometallurgical steps; decopperization in sulphuric acid media and dissolution of selenium in caustic solution. Temperature caustic concentration, oxygen partial pressure and reaction time were all found to increase selenium dissolution. The caustic concentration was varied between 0.36 and 5 mol/L. Maximum selenium extraction was obtained with 4 mol/L caustic concentration. The maximum temperature of 90°C used in the investigation yielded the maximum selenium dissolution. The following reactions were proposed for the dissolution of selenium (Kilic et al.,