"Three wastes" treatment in the production of zirconium compounds

Zirconium chemicals production process, the use of acid and alkali processing of zircon sand, produce large amounts of acid gas, acid waste water, waste containing heavy metals and other production practices is an important issue that must be addressed, at present the country has a lot of good Three waste treatment and comprehensive recycling processes and equipment for production practices.

I. Wastewater treatment process

Figure 1 shows two treatment processes for wastewater from zirconium compound production.

The discharged water has a pH of 6～9, SS77mg/L, and a color of 50 times, reaching the national standard.

Fig.1 Two process principle processes for wastewater treatment of zirconium compound production

Second, acid mist treatment process

Figure 2 shows the process flow of workshop acid mist and furnace dust control.

Fig. 2 Principle process of two flue gas treatment processes in zirconium compound production workshop

Third, silicon slag comprehensive utilization process

In the zirconium oxychloride production process, the hydrolyzed and unhydrolyzed sodium zirconate is reacted with hydrochloric acid in an acid conversion step to form a zirconium oxychloride solution. The residual silicon generates a three-dimensional network of silicic acid gel in an acidic medium, which can be removed by filtration. 1t of silicic acid gel waste residue is produced per ton of product, and the waste residue is strongly acidic. If it is not treated, it will pollute the environment. If only acid-base neutralization is used for landfill, the treatment cost is high, and resource waste will be caused. After studying the properties and uses of silicon slag and sampling tests on silicon slag, it is found that silicon slag can be comprehensively utilized. The water immersion liquid of the silicon slag can be used as a high-quality water treatment agent for papermaking, pharmaceutical and other wastewater after a certain treatment, and the insoluble portion can be processed into high-quality silica (white carbon black). In recent years, polysilicic acid and its composite polymerized silica gel iron-aluminum inorganic polymer flocculant made of iron and aluminum copolymer have become a hot spot of research, and this flocculant is characterized by more than traditional iron. The aluminum salt flocculant has better effect and lower price. The flocculant is made of silica gel, which has strong decolorization and removal of organic matter for the black liquor of papermaking.

The silicon slag leachate and the polymer-polymerized aluminum iron silicate formed by adding iron and aluminum salts have good treatment effects on papermaking black liquor and sewage waste liquid. The mechanism of flocculation is the rapid flocculation settlement by the adsorption bridge of polysilicic acid, the sweep adsorption and the charge neutralization of iron and aluminum ions.

After the water immersion, the silica sol is stirred, dissolved and separated by using appropriate tap water and silicon-containing waste liquid, and washed at a certain pH value while filtering, and the filter cake is dried to obtain white carbon black. It has been found in practice that controlling the pH and washing mode of the silica sol has a large effect on the particle size, specific surface area and silica content of the final silica. The recycling process is shown in Figure 3.

Figure 3 Principle process for recovering silica from silicon slag

The quality of white carbon black produced by the recovery of silicon slag is better than the technical index of precipitated silica GB10517-89, see Table 1.

Table 1 Comparison of the quality of silica recovered from silicon slag

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