| Sulfuric acid residue known as pyrite slag, which is a kind of chemical waste residue produced during the manufacture process of sulfuric acid or sulfurous acid using pyrite. The compounds of iron and oxygen are the main compostion in a pyrite slag, in which the content of iron is generally between30%-60%, much higher than the average grade (33%) of the proved reserves of iron ore in our country. In addition, most of the sulfuric acid residues contain many precious metals and heavy metals, as well as some harmful elements such as arsenic, copper, sulfur, lead, zinc, gold, silver, cadmium etc. In China, the sulfuric acid residue commonly contains higher impurity content and a various impurity species. Especially, the presence of arsenic in the sulfuric acid residue will result the sulfuric acid residue cannot be recycled as iron concentrate. At the same time, China’s sulfuric acid residue has continued to be increased at about16million tons/year of production, which not only cause a waste of iron resources, but also pollute natural environments in the role of weathering and water-soluble. Therefore, removal of the harmful impurities in the sulfuric acid residue and recycling of the iron resources not only eliminates the impact on the environment, but also gets a certain degree of economic and social benefits.In this thesis, a sulfur sulfuric acid residue, containing arsenic, zinc, copper, etc, from a chemical enterprise in Yunnan were studied. In the sulfuric acid residue, Fe grade reached57.61%, mainly in the form of hematite and limonite. However, the content of as was as high as2.78%. Some other impurities such as Cu, Zn and S were also about0.5%. Some crystal of gangue and minerals were wrapped parceled and adhered with each other, resulting in a complex intergrowth structure. The surface edge of the sulfuric acid residue was eliminated, and presented in vaious structures, such as disseminated structures, Honeycomb structure, parcel structure and loose surface structure. Elements of Fe, As, Cu, Zn and S distribute uniformly on the surface. A phenomenon of crystalline substitution and isomorphism take place at the surface of the residue, which results in the combination with each other and formation of the complex compounds.Experimental Study based on the mineral properties, analyzed sulfuric acid leaching process and sulfuric acid leaching-reduction roasting-magnetic separation process feasibility of impurity removal. Experimental results of sulfuric acid leaching impurity process showed that: following optimum conditions, the content of arsenic down to0.19%, removal rate of arsenic reached96.04%, the content of sulfur reduced to0.11%and Removal rate of Cu and Zn around50%, but the grade of Cu in iron concentrate is still exceeded. Although sulfuric acid leaching process is simple and well removal the impurities arsenic and sulfur, the content of As is still high in the sulfuric acid residue and removal effect of Cu and Zn is also poorly, cannot achieve satisfactory removal effect for impurity in sulfuric acid residue.Order to further improves the effect of arsenic removal and cleaning for sulfuric acid residue, using "sulfuric acid leaching-reduction roasting-magnetic separation" combined process to treatment the Sulfuric acid residue. By carrying out the relevant single factor test investigated for various factors affecting, obtained the optimum test parameters. Ultimately, Obtaining iron ore concentrates with copper:Grade of Fe reached69%, content of As and S down to0.1%, content of Zn is about0.1%, content of Cu around0.35%, reached the removal of arsenic and cleaning purposes.Meanwhile, we explored and studied the treatment and utilization for arsenic containing waste acid in the paper. And, the thermodynamic properties of the relevant tests were simulated calculation:Gibbs free energy of the leaching process, Ellingham diagram of the roasting process, pH-Eh diagram of the process of arsenic sedimentation. |
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