Chalcopyrite leaching by hydrogen peroxide in acid media

U disertaciji su prikazani rezultati luženja halkopirita vodonik−peroksidom u rastvoru hlorovodonične i sumporne kiseline. Ispitan je uticaj brzine agitacije, odnosa čvrsto:tečno, koncentracije kiseline i oksidansa, reakcione temperature, kao i uticaj polarnih organskih rastvarača (metanol i 2-propanol) na izluženje bakra i gvožđa iz halkopiritnog koncentrata. Ustanovljeno je da se u sistemu HCl−H2O2 intenzivna oksidacija halkopirita odigrava u prvih 60 minuta reakcije, nakon čega se brzina reakcije znatno smanjuje usled brzog katalitičkog razlaganja vodonik−peroksida. Utvrđeno je da brzina mešanja i reakciona temperatura imaju neznatan uticaj na rastvaranje halkopirita dok je odnos čvrsto:tečno značajno uticao na izluženje bakra i gvožđa. Porast koncentracije hlorovodonične kiseline (0,1–3,0 mol/dm3) i vodonik-peroksida (0,5–3,0 mol/dm3) u rastvorima ima pozitivan uticaj na oksidaciono luženje halkopirita. Određen je red reakcije od 0,30 u odnosu na koncentraciju kiseline, odnosno 0,53 u odnosu na koncentraciju vodonik-peroksida. Poredeći rezultate ispitivanja u sistemu HCl−H2O2 sa ostvarenim rezultatima u sistemu H2SO4-H2O2, utvrđeno je da je sistem H2SO4−H2O2 pogodniji sistem za luženje halkopirita u pogledu dobijenih stepena izluženja metala. Reakciona temperatura ima uticaja na brzinu rastvaranja halkopirita u početnom stadijumu luženja, dok odnos čvrsto:tečno i u ovom sistemu značajno utiče na izluženje bakra i gvožđa. Porast koncentracije sumporne kiseline (0,3–3,0 mol/dm3) i vodonik-peroksida (0,5–3,0 mol/dm3) ima uticaja na oksidaciono luženje halkopirita (red reakcije 0,10 odnosno 0,24 u odnosu na koncentraciju kiseline i oksidansa, respektivno). Kinetika rastvaranja halkopirita u oba ispitana sistema se uspešno opisuje jednačinom kinetike prvog reda X=Xm(1−e−kt). Vrednosti energije aktivacije u hloridnim rastvorima iznose 19,6 kJ/mol (preko Cu), odnosno 17,1 kJ/mol (preko Fe), dok su u sulfatnim rastvorima dobijene veće vrednosti energije aktivacije koje iznose ~40 kJ/mol (preko Cu i preko Fe) što ukazuje na to da difuzija kroz sloj proizvoda limitira brzinu procesa...The dissertation presents the results of leaching of chalcopyrite with hydrogen peroxide in a solution of hydrochloric and sulfuric acid. The effect of agitation rate, solid to liquid ratio, acid and oxidant concentration, reaction temperature, as well as the effect of polar organic solvents (methanol and 2-propanol) on the copper and iron extraction from the chalcopyrite concentrate, have been examined. It has been found that an intensive chalcopyrite oxidation occurs in the HCl−H2O2 system in the first 60 minutes of reaction, after which the reaction rate significantly decreases due to the rapid catalytic decomposition of hydrogen peroxide. The stirring speed and reaction temperature have a slight effect on chalcopyrite dissolution, while the solid to liquid ratio has a significant effect on copper and iron extraction. The increase in the concentrations of hydrochloric acid (0.1–3.0 mol/dm3) and hydrogen-peroxide (0.5–3.0 mol/dm3) in solutions has a positive effect on the oxidative leaching of chalcopyrite. A reaction order of 0.30 was determined in relation to the acid concentration, that is, 0.53 in relation to the hydrogen peroxide concentration. Comparing the results of the HCl−H2O2 system with the results obtained in the H2SO4−H2O2 system, it has been established that the H2SO4−H2O2 system is more suitable system for the chalcopyrite leaching with respect to the obtained metal extraction degrees. The reaction temperature has an effect on the rate of chalcopyrite dissolution at the initial stage of the leaching, while the solid to liquid ratio significantly affects the extraction of copper and iron in this system as well. The increase in the sulfuric acid concentration (0.3-3.0 mol/dm3) and hydrogen-peroxide concentration (0.5-3.0 mol/dm3) has an effect on the oxidative leaching of chalcopyrite (reaction order of 0.10 and 0.24 in relation to the concentration of acid and oxidant, respectively). The kinetics of chalcopyrite dissolution in both examined systems is successfully described by the first-order kinetics equation X=Xm(1−e−kt). The activation energy values in the chloride solutions are 19.6 kJ/mol (over Cu) and 17.1 kJ/mol (over Fe), while the higher activation energy values are obtained in the sulphate solutions, ~40 kJ/mol (over Cu and over Fe), indicating that the diffusion through a product layer limits the reaction rate..