Process for Decolorization and Reuse of Waste Acid

Background Introduction

Waste acid, also known as waste sulfuric acid, is generated in industrial production through processes such as nitration, esterification, sulfonation, alkylation, catalysis, and gas drying of organic matter, or in processes such as titanium dioxide production, steel pickling, and gas drying.

With the advancement of industrialization, the production of industrial waste acid has been increasing year by year. Protecting the environment, achieving comprehensive resource utilization, and controlling the discharge of three wastes have become policy planning and industry development priorities. China's annual production of waste acid reaches about 100 million tons, of which the vast majority is waste sulfuric acid. From 2016 to 2019, the total output of waste acid in China (mainly including sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and hydrofluoric acid) showed an overall downward trend. In 2019, the total output of waste acid in China was 94.79 million tons, a year-on-year decrease of 3.9%. The sources of waste acid production in China are quite extensive, with industries producing over 10 million tons of waste acid including the titanium dioxide industry, non-ferrous metal smelting industry, and steel industry. In addition, the dye industry, acid production industry, lead-acid battery industry and other industries also have a large amount of waste acid emissions. In 2019, the output of waste acid in the titanium dioxide industry was about 26.75 million tons, accounting for 28.2% of the total output of waste acid; The output of waste acid in the non-ferrous metal smelting industry is about 11.63 million tons, accounting for 12.3% of the total output of waste acid. Waste acid recycling, as a more effective way to replace waste acid neutralization, is gradually being promoted in China.

Technical Introduction

Our company has independently developed a special resin based on the characteristics of waste acid, which utilizes the functional groups in the polymer resin structure to adsorb organic matter or metal ions in wastewater, achieving efficient separation of acid and organic matter or metals.

Developing supporting application processes and processing equipment with special resins as the core, the purified acid can be reused in production. After adsorption saturation, appropriate solvents can be used for desorption, and metals can be recovered. For organic matter, incineration treatment can be carried out. Regeneration is achieved after resin detachment, with a long service life.

Figure 1. Process Flow

Application Cases

<1> The organic waste acid from a hazardous waste treatment company in Jiangsu requires colorless and transparent treatment, COD<4000ppm, and acidity loss less than 5%.

Table 1. Raw Water Quality

Water volume (ton/day) Inlet appearance Inlet acidity (sulfuric acid) Inlet COD (mg/L) Outlet appearance Outlet COD (mg/L) Outlet acidity (sulfuric acid)

60 yellow 39.5% 31600 colorless 1600 39.2%

<2> Appearance of treated water

Figure 2. From left to right are the raw water and adsorbed effluent, respectively

Application Fields

1. Metal containing waste acids generated during wet metallurgy, chemical production processes, and metal surface treatment.

2. Removal of organic compounds from waste acid catalysts and purification of various inorganic waste acids.

3. Removal of benzene derivatives and plasma removal of iron, copper, and zinc in by-product hydrochloric acid.