The Recycling of Acid Wastewater with High Concentrations of Organic Matter: Recovery of H₂SO₄ and Preparation of Activated Carbon

Abstract

Little work has been focused on the recycling of hazardous acid waste with high concentrations of organic matter from petroleum refining. This study developed an innovative, effective, and simple method for the recycling of acid waste that can successfully resolve this significant problem in industry. After parameter optimization, the optimal process is as follows. (1) Through heat treatment at 170 °C, liquid acid waste was transformed into solid; (2) by washing the solids, 70% by weight of sulfuric acid was recycled; and (3) the solid residue after washing was activated by alkali (NaOH or KOH) at an alkali and organic carbon ratio of 2:1, at a temperature of 650 °C for 60 min, producing superior-grade activated carbon with a specific surface area of 1378 m2/g, a pore volume of 0.5107 cm2/g, an iodine number of 1800 mg/g, and a methylene blue adsorption capacity of 240 mg/g. Thus, in this way, both waste sulfuric acid and organic impurities are turned into valuable resources, and no hazardous waste gypsum residues are generated. This method both reduces carbon emissions and recycles valuable resources, which is of important environmental and economic significance.

Keywords

• acid waste
• heat treatment
• recycle
• sulfuric acid
• activated carbon