Sulfuric acid method titanium dioxide water washing and water circulation membrane treatment process

0 Preface

Titanium dioxide has a wide range of applications, including the plastics industry, paint industry, daily chemical industry, etc.

1 Traditional washing technology of sulfuric acid titanium dioxide

1.

After the titanium dioxide is hydrolyzed, under normal circumstances, the metatitanic acid slurry is H2SO422%-30%, TiO2160～180g/L, FeSO4·7H2O200～250g/L, and the slurry needs to be washed with water.

1.

After the metatitanic acid in the hydrolyzed material is washed for the first time, although it can remove the soluble impurity ions, it cannot be completely removed.

1.

Solid-liquid separation is the process of filter cake washing, so in the metatitanic acid washing process, the indispensable equipment is solid-liquid separation equipment

2 Water washing and water circulation membrane treatment technology

2.

In the water washing process, the tubular microfiltration membrane is the main component, and its filtration method is shown in Figure 2
.
During operation, the pressure will drive the metatitanic acid slurry flowing on the surface of the tubular microfiltration membrane tube, and its water-soluble impurity ions will seep out of the tube together with sulfuric acid and water, and the metatitanic acid solid will be intercepted.
Circulatory movement in the membrane tube
.
Subsequently, fresh water is continuously added in the tube membrane, and washing water is continuously produced, which can effectively remove soluble impurity ions
.
In addition, the "cross-flow" filtration of the tubular microfiltration membrane is closely related to the recycling of washing water, so reverse osmosis technology can be applied to it, which can effectively separate low-valent ions from high-valent ions
.
FeSO4 and H2SO4 are the main components of washing water.
After they are separated by selective reverse osmosis membrane elements, Fe2+-free acidic water and high-concentration FeSO4 concentrated water can be obtained.
This acidic water is used as metatitanic acid for the second time.
Washing water can not only greatly reduce the amount of fresh desalinated water, but also can effectively maintain the acidic environment of the washing system, so as to ensure that Fe2+ will not be oxidized during the washing process
.

2.
2 Process flow

Membrane separation system, membrane washing system, and powder recovery system are the main components of the process flow.
The details are shown in Figure 3
.
In this process, the entire system needs to introduce a small amount of desalinated water to maintain the water balance, and the metatitanic acid slurry will all be converted into qualified washing materials
.
In addition, the system will not discharge waste water, and at the same time, it is more convenient for the advanced processing of the clean waste acid extracted
.

2.
2.
1 Powder recovery system

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2.
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2.
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3

The acidic water in the membrane separation inlet tank will be sent to the beating tank and the membrane separation system.
The pus produced by the membrane separation system will be pre-washed in the plate and frame system, and then the clear liquid produced will be sent to the second washing membrane The washing device is then used for the second washing of metatitanic acid
.
After the washing water is processed by the membrane separation device, its recycling can reduce the consumption of fresh desalinated water
.
At the same time, the acidity of the washing water can be effectively maintained, so as to ensure that the metatitanic acid is always in an acidic environment during the washing process, and no additional sulfuric acid adjustment system is required to adjust the acidity
.

3 Conclusion

In short, the sulfuric acid process titanium dioxide industry applies washing and washing water circulating membrane treatment processes, which can not only realize the recycling of washing water
.
At the same time, it can also reduce the consumption of fresh desalinated water, and greatly alleviate the burden of wastewater treatment, so this technology has important practical significance
.