Study On The Technology Of Iron Oxide Red From Pickling Waste Liquor

Pickling is a necessary process of cold-rolling steel production and metal surface treatment. At present, hydrochloric acid pickling process is widely used in industry. Pickling waste liquor of Hydrochloric containing a large number of ferrous chloride and free acid, if we discharge waste liquor directly, it will not only cause pollution and destruction to the environment, but also result in a waste of useful resources. To reasonably use ferrous chloride of waste liquor and eliminate environmental pollution caused by waste acid, It has aroused people’s much concern to the preparation of iron oxide red with pickling waste liquor as raw material. Iron oxide red is the second largest inorganic pigment after titanium dioxide, and it is widely used in the field of building materials, rubber and magnetic materials, etc. At present, much high-quality iron oxide in our country is from foreign country. Therefore, moderately developing high-quality iron oxide product of our country has a very important practical significance for improving the structure of the existing products and enhancing competitiveness.The purpose of the paper is preparing high purity iron oxide red with electroplating pickling waste liquor as raw materials and ammonium bicarbonate as precipitant by air oxidation method, also recycling ammonium chloride. It not only can develop the production process of high purity oxide red and reduce the production cost, but also can use resources effectively and protect the environment. So it will improve the economic benefit and social benefit.The pickling waste liquor in experiment is from electroplating factory in ShenYang. The pickling liquor is mainly used to remove rust of steel before electroplating Zinc and retreat plating of unqualified Zinc products, whose characteristic is with strong acid and a high content of ferrous iron, also a small amount of Zinc, manganese, silicon and other impurities. So this experiment is mainly consist of two parts:the refinement process of pickling waste liquor and the synthetic process of iron oxide red.The refinement process of pickling waste liquor includes neutralizing free acid with iron powder, adjusting the pH value of solution with ammonia, removing Zinc with sodium sulfide and removing Silicon with cationic polyacrylamide. Finally we get refined ferrous chloride solution. In the test, we find the optimum conditions:iron powder is 1.5 times of the theoretical value, water bath temperature is 80℃, the stirring speed is 200 r/min, the reaction time is 3 h, the pH value of removing Zinc is about 3, the optimal hydrolysis pH value before adding PAM is about 5.2, and the volume of PAM (1 g/L) is 3% of that of pickling waste liquor.In the synthesis process of iron oxide red, we take refined ferrous chloride solution as raw material and ammonium bicarbonate as precipitant. The process includes the synthesis and oxidation of precipitation, the drying and calcining of oxidation product. Finally we get high purity iron oxide red. At the same time, we find the optimum technological conditions:The optimum mole ratio of ammonium bicarbonate and ferrous chloride is 2.4:1, the concentration of ferrous chloride is 1.2 mol/L, the temperature of precipitation synthesis is 45℃, the aging time of precipitation is 45 min; The oxidation temperature of precipitation is 45℃, the oxidation time of precipitation is 3 h, the air is bubbled into the precipitation in the form of continuous small bubbles; The calcination temperature of oxidation product is 750℃; The calcination time of oxidation product is about 40 min.The products are confirmed by XRF, XRD, SEM. The experimental results show that the impurity content of iron oxide red is less, the crystal shape of iron oxide red is a-Fe2O3, the surface profile of iron oxide red is similar to the rodlike structure and the particle size of iron oxide red is about 150～180 nm. Meanwhile, we test the main content, the oil absorption value, the colored light and the pH of water extract fluid of iron oxide red. The result shows that the indicators of iron oxide red conform to the national pigment relevant standard.