In this work the dissolutive behavior of gold in alkaline medium using thiourea (TU), under different variables, was studied in a theoretical and experimental way, in order to determine the conditions under which it i...In this work the dissolutive behavior of gold in alkaline medium using thiourea (TU), under different variables, was studied in a theoretical and experimental way, in order to determine the conditions under which it is feasible to dissolve gold in thiourea-alkaline medium. A thermodynamic study was conducted by chemical speciation using the method of Ro-jas-Hernández, together with an electrochemical study where the electric potential was swept in the anodic direction. The main results of the thermodynamic study were that formamidine disulfide (FDS) and sulfinic compounds (S.C.) prevail at alkaline pH;by increasing the initial concen-tration of thiourea at alkaline pH, the presence of the gold complex is al-most zero for any initial concentration of thiourea. By including sodium sulfite in the gold-thiourea system, it was possible to obtain the Au(I)-TU complex at alkaline pH, with a presence of 95.13%. Electrochemical tests allowed verifying that in the absence of sodium sulfite the dissolution of gold in an alkaline medium is very slow but adding sodium sulfite im-provements become evident in the dissolution of the metal. Therefore, sodium sulfite catalyzes the gold dissolution process and stabilizes the thiourea. With this study it was possible to establish the feasibility of using thiourea in an alkaline medium for the dissolution of gold, and the conditions under which it is possible to dissolve the gold in that medium. With these fundamentals and conditions, it is now possible to move forward to test this system for minerals and/or concentrates containing gold.展开更多
The study of copper adsorption onto ion exchange resins of anionic type is part of the gold recovery from ammonia-thiosulfate solutions, where copper is the main impurity of the system because it acts as a catalyst of...The study of copper adsorption onto ion exchange resins of anionic type is part of the gold recovery from ammonia-thiosulfate solutions, where copper is the main impurity of the system because it acts as a catalyst of gold dissolution reaction. A study is made of the adsorption and desorption of copper in the form of the complex in an ammonia-thiosulfate media on an ion exchange resin, DOWEX 550A, classified as a strong base, which in its inner structure has a quaternary amine functional group. In the studied pH range copper adsorption increased with increasing pH, while the presence of thiosulfate decreased it, the same as the ammonia content, due to the greater presence of cuprotetramine, . Elution of the copper complexes from the resin was more efficient with sulfite than with perchlorate.展开更多
文摘In this work the dissolutive behavior of gold in alkaline medium using thiourea (TU), under different variables, was studied in a theoretical and experimental way, in order to determine the conditions under which it is feasible to dissolve gold in thiourea-alkaline medium. A thermodynamic study was conducted by chemical speciation using the method of Ro-jas-Hernández, together with an electrochemical study where the electric potential was swept in the anodic direction. The main results of the thermodynamic study were that formamidine disulfide (FDS) and sulfinic compounds (S.C.) prevail at alkaline pH;by increasing the initial concen-tration of thiourea at alkaline pH, the presence of the gold complex is al-most zero for any initial concentration of thiourea. By including sodium sulfite in the gold-thiourea system, it was possible to obtain the Au(I)-TU complex at alkaline pH, with a presence of 95.13%. Electrochemical tests allowed verifying that in the absence of sodium sulfite the dissolution of gold in an alkaline medium is very slow but adding sodium sulfite im-provements become evident in the dissolution of the metal. Therefore, sodium sulfite catalyzes the gold dissolution process and stabilizes the thiourea. With this study it was possible to establish the feasibility of using thiourea in an alkaline medium for the dissolution of gold, and the conditions under which it is possible to dissolve the gold in that medium. With these fundamentals and conditions, it is now possible to move forward to test this system for minerals and/or concentrates containing gold.
文摘The study of copper adsorption onto ion exchange resins of anionic type is part of the gold recovery from ammonia-thiosulfate solutions, where copper is the main impurity of the system because it acts as a catalyst of gold dissolution reaction. A study is made of the adsorption and desorption of copper in the form of the complex in an ammonia-thiosulfate media on an ion exchange resin, DOWEX 550A, classified as a strong base, which in its inner structure has a quaternary amine functional group. In the studied pH range copper adsorption increased with increasing pH, while the presence of thiosulfate decreased it, the same as the ammonia content, due to the greater presence of cuprotetramine, . Elution of the copper complexes from the resin was more efficient with sulfite than with perchlorate.
