Process for recycling aluminum hydroxide from acid wastewater containing aluminum ions

Abstract

The invention discloses a process for recycling aluminum hydroxide from acid wastewater containing aluminum ions. The process comprises the following steps of: (1) pre-treating the acid wastewater containing the aluminum ions firstly; and (2) neutralizing to completely convert the aluminum ions to insoluble aluminum hydroxide, stirring at slow speed at a neutralization temperature, separating solid and liquid, discharging the wastewater which reaches a standard level, and recycling insoluble aluminum hydroxide sludge. The insoluble aluminum hydroxide sludge has lower moisture content and higher purity than that of the other method, and provides a premise for further producing a product with high added value. The invention not only solves the problem of difficult separation of aluminum hydroxide suspension, and the recycled aluminum hydroxide has high purity and narrow size distribution, and can be taken as a raw material of the products, such as pseudoboehmite, nano-alumina and the like with high added value.

Description

technical field [0001] The invention belongs to the technical field of waste water treatment, and in particular relates to a process for recovering aluminum hydroxide from acid waste water containing aluminum ions. Background technique [0002] There are roughly three types of hydroxide precipitates formed by metal ions: ① crystalline precipitates, large particles, compact structure, and easy separation; ② amorphous precipitates, disordered ion arrangement inside the precipitate, loose structure, and small particle size; ③ curd precipitates, the The size and shape are between the first two. In aluminum-containing acidic wastewater, the content of aluminum ions is often low, and an amorphous precipitate or even a colloidal state is formed during neutralization, which makes separation extremely difficult. To improve the separation efficiency, it is necessary to add a filter aid, but this causes the aluminum in it to have no recovery value due to the high content of impurities...

AI Technical Summary

Problems solved by technology

In aluminum-containing acidic wastewater, the content of aluminum ions is often low, and an amorphous precipitate or even a colloidal state is formed during neutralization, which makes separation extremely difficult

In order to improve the separation efficiency, it is necessary to add filter aids, but this will cause the aluminum in it to have no recovery value due to the high content of impurities.

If no filter aid is added, not only will the separation effect be poor, but also the recovered aluminum hydroxide sludge will have a large water content, many soluble impurities, and a wide particle size distribution, which will bring great trouble to further utilization

For example, in the aluminum-containing acid wastewater of an enterprise, the content of aluminum ions is between 4-10g / L, and the amount of acid wastewater produced every day is 300m 3 Above, take soluble alkali to neutralize, and form milky white aluminum hydroxide colloidal emulsion after neutralization, once tried to separate with a decanter centrifuge, the result proved that about 10% of the aluminum hydroxide could not be recovered, and the waste water was not up to standard; Plate and frame filter press, because the aluminum hydroxide particles are too fine, it is still difficult to separate, and it is easy to separate when adding filter aids, but because of the large impurities, the aluminum hydroxide has no recycling value

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