Preparation Of Black Iron Pigment From Pyrite Wastewater

The pyrite wastewater which is produced during or after the iron pyrite exploitation contains lots of iron with low acidity and has a potential harm to environment. The utilization of pyrite wastewater to prepare black iron pigment has important significance. This is not only due to the treatment of the pyrite wastewater and elimination of environmental pollution, but also making wastewater to resource and recovery of iron resource from pyrite wastewater.In our study, the process feasibility and optimal conditions of black iron pigment preparation from pyrite wastewater were explored through precipitation and wet oxidation. The preparation conditions of high tinting strength black iron pigment were discussed via electrolytic removal of copper and addition of dispersants such as citric acid, sodium lauryl sulfate and polyethylene glycol.The result showed that rapidly and equably adding 10% NaOH to pyrite wastewater until the condition of pH 9, stirring rate 200r/min for 3 minuts, no PAM addition and 120 minuts precipitation resulted in the optimal effect, at the same time the wastewater reached the discharge standard.Ferrous hydroxide which got from precipitation was able to make black iron pigment through reacting at 80⁹0℃f or 2.5³h with the origimal pH of 9¹0, stirring at 100²00r/min and drying at 60⁸0℃. Black iron pigment with high quality was obtained at the conditions of origimal pH 9.5,reaction temperature 85℃,reaction time 2.5h, stirring rate 150 r/min and drying temperature 80℃. XRD and SEM analysis showed that the particle size of the prepared black iron pigment was about 60nm,and Fe₃O₄ content was higher than 95%. The product could reach the requirements for the first-grade standard in black iron pigment industry. But in the black iron pigment, there was a little Cu₂O which made the product with some red color. Between the Fe₃O₄ particles, there was visible aggregation.After electrolyzed pyrite wastewater for 30min by 2.0V DC, black iron pigment with high tinting strength could be made through precipitation, wet oxidation and adding 0.75ml 1% citric acid at the beginning of reaction. XRD, SEM and color analysis showed that the high tinting strength black iron pigment had closer color to the standard sample and basicly with no red color in it. The agglomeration was obviously improved, the size of particle was in a little decrease.