The gangue sponge: implications for in-situ/heap leaching of chalcopyrite

(Partial) dissolution of reactive aluminosilicate gangue minerals increase the complexity of chalcopyrite leaching by forming an amorphous, porous silica residue that interacts with the leaching solution to form local non-equilibirum microenvironments. Reactive phyllosilicates chamosite and kaolinite minerals berthierine and greenalite sample mineralogy and bulk chemistry is determined by XRD, XRF, Moessbauer Spectroscopy and OES. After leaching, the leaching solution chemistry was analysed via OES and UV-VIS. The leaching residue textures, chemistry and cpy S-oxidation state was analysed using SEM, FIB, uXRF and uXANES. Heterogeneous element distribution in the porous textures and leaching solution, as well as chalcopyrite and pyrite textures reveal incongruent dissolution of reactive gangue minerals that form a porous amorphous silica residue that can entrap and penetrate Cu sulfides. The pores of the ASR form local microreactors with variable non equilibium conditions of the lixiviant, that lead to larger variety and more complex S oxidation states on chalcopyrite grains. Gangue mineral dissolution hence influences chalcopyrite leaching reactions and Cu recovery.

（部分）反应性铝硅酸盐脉石矿物的溶解，会通过生成无定形多孔硅质残渣而提升黄铜矿（chalcopyrite）浸出过程的复杂性：该残渣可与浸出液相互作用，形成局部非平衡微环境。针对反应性页硅酸盐类矿物（包括鲕绿泥石（chamosite）、高岭石（kaolinite）以及粒硅铁石（berthierine）、绿鳞石（greenalite））的样品，采用X射线衍射（X-ray Diffraction, XRD）、X射线荧光光谱（X-ray Fluorescence Spectrometry, XRF）、穆斯堡尔光谱（Mössbauer Spectroscopy）与光电发射光谱（Optical Emission Spectroscopy, OES）对其矿物学组成与整体化学特性进行了表征。浸出完成后，采用OES与紫外-可见分光光度法（UV-VIS）对浸出液的化学组成进行了分析。通过扫描电子显微镜（SEM）、聚焦离子束（FIB）、微区X射线荧光光谱（uXRF）与微区X射线吸收近边结构谱（uXANES），对浸出残渣的形貌、化学组成以及黄铜矿的硫氧化态进行了表征。多孔残渣形貌与浸出液中的元素非均匀分布特征，以及黄铜矿与黄铁矿（pyrite）的形貌特征，揭示了反应性脉石矿物的不一致溶解行为：这类矿物溶解后会生成多孔无定形硅质残渣，该残渣可包裹并侵入铜硫化物矿物。无定形硅质残渣（ASR）的孔隙可形成局部微反应器，其内浸出剂的环境条件呈现显著非均匀性，进而导致黄铜矿颗粒表面的硫氧化态种类更多、更为复杂。因此，脉石矿物的溶解会对黄铜矿浸出反应与铜回收率产生显著影响。