Preparation Of Cobalt Based DSA Anode And Its Application For Decomposing Molybdenum Middlings By Electro-Oxidation Method

Nowadays, the noble metal become less and less as the widely use of DSAanode. In order to prepare a low-cost DSA anode with high electro-catalytic activity,the systemic studies on the effects caused by doping cobalt into the traditionalRu3Ti7/Ti anode were carried out in this paper. The deactivation mechanism of theanode was also studied. Then the optimal anode was used to decompose theMolybdenum Middlings by electro-oxidation method. The kinetics of decompositionreaction of molybdenum middlings and its technical and economic analysis were alsodiscussed. The main results were as follows:(1) The Ru(1-x)CoxTi2/Ti coating were sole rutile-type ternary solid solutionaccording to the XRD analysis, CV analysis showed that the voltammetric charge q*of the coating increase compared with the conventional Ru3Ti7/Ti anode. Steady-statepolarization curves and the potential of chlorine evolution (E200Cl2), oxygen evolution(E200O2) test showed that the optimum anode was Ru0.5Co0.5Ti2/Ti coated anode, it hasthe lowest (E200Cl2) and polarizability, the biggest diference between the potential ofchlorine evolution and oxygen evolution(△E2). The accelerated life tests(ALT) alsoindicated that this coated anode possessed the longest ALT time.(2) Compared with the traditional Ru3Ti7/Ti coating, the content of noble metalRu in Ru0.5Co0.5Ti2/Ti anode reduce by half. Meanwhile, the Cl2evolution potentialdidn’t change as the O2evolution potential increased. As the result, the selectivity ofchlorine evolution increased, and the ALT time increased almost by150%.(3) The performance of the anode varied greatly in different preparation technics.With the thermal oxidation temperature of450℃, Ru0.5Co0.5Ti2/Ti anode possessedthe best selectivity of Cl2evolution and ALT time. Under the same brush time, the Cl2evolution potential decreased and the ALT time increased with the concentration ofcoating solution increased. The ALT time of per coating weight was the longest andthe utilization ratio of noble metals was highest when the solution concentration is0.50mol/L. According to the analysis of deactivation mechanism, the anodedeactivated was mainly due to the spalling of the coating, the dissolution of the activecomponent and the oxidation of the substrates. The rutile-type solid solution phasewas damaged after the deactivation, no new inert phases appeared in the coating. (4) The optimal process conditions of hydrometallurgical process ofelectro-oxidation for molybdenum middlings were: temperature of40℃, slurryconcentration of50g/L~75g/L (S/L), current density of1000A/m2, electrolyteconcentration CNaClof100g/L，pH value of10. in90min under these processconditions, both the Mo leaching rate and the current efficiency could reach96.1%and50.7%.(5) Cycle experiments confirmed that it is possible in NaCl medium to electrolyzemolybdenum middling circularly. The decomposition rate constant of molybdenummiddling by electro-oxidation method increases with temperature increase within15℃~45℃according to the kinetic analysis. The reaction is a kinetic model with theapparent activation energy of Ea=16.55kJ/mol. By electrolyzing90min under theoptimum conditions, with the slurry concentration of50g/L and75g/L, the powerconsumption were31.69and33.08KWh/kgMo respectively according to thetechnical and economic analysis.