Study On The Pretreatment Of Cyanided Tailings By Catalytic Ozonation

With the rapid development of gold Industry, the gold productionvolume all over the world have increased steadily. A large amount of exploitation of gold mineral resources brings about the foldincrease of cyanided tailings as a by-product, which not only results in tremendous economy loss to the enterprises but also has very bad effects to the peripheral environment. How to effectively use these Secondary Resources becomes an important and urgent problem for all environmental protection staff. As a refractory ore, the choice on the pretreatment method is of vital importance to its developing and utilizing.In this Paper, cyanided tailings from gold smeltery in Sanmenxia. He Nan province were used for test materials. The technological condition and oxidation kinetics of the reaetion Proeess were studied. The main contents are as follows:Pretreatment of cyanided tailings with Potassium Permanganate in acid media was investigated. Effects of reaction time, temperature, solid to liquid ratio, Potassium Permanganate addition and the initial concentrate sulphuric acid on pretreatment were examined. The optimum reacting conditions were determined according to a series of experiments: reaction time(5h), temperature(80℃), solid to liquid ratio(1:20), Potassium Permanganate addition(75g/L), the initial concentrate sulphuric acid(1.3mol/L). The leaching rate of Fe and weight loss reached 92.82% and 47.94% respectively.The method of Manganese-catalysed ozonation for the pre-oxidation of cyanided tailings was also studied. The Mn2+ dosage,initial concentrate of sulphuric acid,ozone volume flow,temperature and agitation speed were examined for the effect of pretreatment. The optimum reacting conditions were determined: slurry density(2.5%),agitation speed(700rpm),temperature(60℃),Mn²⁺ dosage(40g/L),ozone volume flow(80L/h),initial concentrate of sulphuric acid(1mol/L),reaction time(6h). Under such conditions, The leaching rate of Fe and weight loss reached 94.85% and 48.89% respectively.Then the leaching process of cyanided tailings by Mn²⁺ /O₃ was analysed to find out that the leaching of pyrite depends on the synergetic oxidation of high-valent manganese and O₃, thereinto the former plays an important part. The shirinking particle modle was put to use to study the kinetics of the leaching process, through analysis and comparison of testing data, the diffusion of Mn³⁺ from liquid phase to the pyrite surface is the rate-controlling step and the activation engery was found to be 7.76kJ/mol that conforms to the diffusion control.At last, the paper compared the two pretreatment processes. On the basis of the method of Manganese-catalysed ozonation, the plan for reutilization of cyanided tailings was proposed to recycle main valuable elements such as gold,silver and iron. Besides, the feasibility of economy,environmental protection and technology were analysed. These works have greatly broadened the prospects of cyanided tailings utilization.