Zinc Hydrometallurgy Red Iron Slag Preparation Of Transparent Iron Oxide Pigments

The comprehensive utilization of hydrometallurgy zinc hematite residues can not only reclaim the resources but also control the cinders pollution. Transparent iron oxide pigments have been made from high quality FeSO₄·7H₂O . This can open up a new way of the comprehensive utilization of hydrometallurgy zinc hematite residues.In this study, hydrometallurgy zinc hematite residues is used as raw materials, FeSO₂·7H₂O is made through the process of sulfuric acid pickling, purifying, reduction and crystallizing. Transparent iron oxide pigments which have been made by air oxidation method achieve the quality requirements. In this study use the direct oxidation to get transparent iron oxide, without the need for preparation of the seed and secondary oxidation,which is different from traditional methods. Therefore, the necessary equipment and processes have been simplified, easy to be applied in industry, and the cost has been reduced.The key two parts of the preparation of copperas from hydrometallurgy zinc hematite residues are sulfuric acid pickling and purifying. In sulfuric acid pickling stage, use the E-pH diagram of major metals (Fe, Zn, Pb) to determine the conditions of sulfuric acid pickling. In purifying stage, use the difference of precipitation pH of the metals (Fe, Zn, Mn, Mg, Cu) to remove the impurities, so as to obtain copperas. The results show that the optimum conditions are as follows: sulfuric acid pickling stage,reaction temperature: 80℃,reaction time: 2.5h,vitriol excess coefficient: 1.20; purifying stage, keeping the pH at 4.1 can make Fe³⁺ precipitate out, and separated from other ions.The key of preparation of transparent yellow iron oxide is divided into two parts, iron precipitation and oxidation. In the stage of iron precipitation, studied NaOH as the precipitant,at the same time, blowned nitrogen to prepare Fe(OH)₂,and explored the effects of Fe²⁺ initial concentration, alkali ratio, the amount of additives and temperature on the products. In the oxidation stage, explored the effects of oxidation temperature and oxidation time, mixing speed on the products. The results show that,the optimum conditions are:initial concentration of Fe is C₂ mol/L, alkali ratio is 1.5, the quantity of dispersant Y_B is 0.16% of FeSO₄.7H₂O amount;iron precipitation stage: temperature 22-25℃, stirring speed 250r/min, FeSO₄ solution dropping to NaOH solution at the speed of 3.3ml/min; oxidation stage: temperature 28-30℃, stirring speed 750r/min, flow velocity of oxygen 3.5L/min, oxidation time 1.5h ;surface treatment stage: quantity of A is 20%-30% of transparent iron oxide pigments amount, at room temperature for the temperature, reaction time 1h.Transparent yellow iron oxide calcined at 350℃can get transparent red iron oxide.The pigment in this research is the shape of the spindle, major axis is about 95nm, minor axis is about 26nm, axis ratio is about 3.7, which achieve the quality requirements.