Regeneration of metal nitric acid and hydrofluoric acid pickling waste liquid and recovery process of metal elements

Abstract

The invention provides a process of regenerating metal nitric acid and hydrofluoric acid pickling wastewater and recycling metal elements, belonging to the field of steel, metal and mechanical processing. The process comprises the following steps: a sulfuric acid replacing step, a lime neutralizing step and a strong base neutralizing step. According to the process, hydrofluoric acid, nitric acid, calcium sulfate and other metal hydroxides are recycled by virtue of the sulfuric acid replacement, the lime and the sodium hydroxide fractional neutralization and precipitation. The process is low in investment cost, low in operation cost, capable of recycling more resources and capable of being widely applied to the resource recycling industry.

Description

technical field [0001] The invention belongs to the field of iron and steel, metal and mechanical processing, and in particular relates to a process for regenerating metal nitric acid and hydrofluoric acid pickling waste liquid and recovering metal elements. Background technique [0002] Iron and steel enterprises or stainless steel processing industries often use a mixture of nitric acid and hydrofluoric acid to treat stainless steel (chromium and chromium-nickel gold), special-purpose alloys (such as nickel-based alloys), or special metals (such as titanium, zirconium) plates and rods. Pickling is carried out on the surface of metal and other materials to remove the oxide scale on the metal surface and meet the requirements of metal material processing. The waste liquid contains a lot of free HNO3, HF and Fe, Ti, Ni, Cr, Zr and other metal cations. These waste liquids are usually used as follows: [0003] 1) The lime one-step neutralization and precipitation method is us...

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Problems solved by technology

[0003] 1) The lime one-step neutralization and precipitation method is used for waste liquid neutralization and precipitation treatment. After the treatment, a large amount of mixed sludge containing metal hydroxides is produced. These sludges are of extremely low value and are generally used for landfills, which will cause environmental damage. Certain hazards, this method cannot recover compound and free nitric acid and hydrofluoric acid

[0004] 2) Using the spray roasting method, spray roasting at a high temperature of 300-500 ° C to decompose the metal hydroxide at a high temperature, absorb the gas, recover nitric acid and hydrofluoric acid, and recover the iron oxide powder through the bottom of the roasting furnace. This method The recovery rate of nitric acid, hydrofluoric acid and metal elements is high, but the investment is large and the operating cost is high

[0005] 3) By distillation, volatile nitric acid and hydrofluoric acid can be distilled out, but this method can only recover free nitric acid and hydrofluoric acid, and the recovery efficiency is low

[0006] 4) The ion exchange method can only recover free nitric acid and hydrofluoric acid, and the recovery efficiency is low

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