Optimization of Fixed-Bed Column for Chlorobenzene Removal from HCl Streams

Inorganic acids are commonly used in the leaching process of end-of-life lithium-ion batteries (LIBs) due to their low cost and high leaching efficiency. Among these, sulfuric acid is the most frequently used. However, in the pursuit of more environmentally friendly approaches, hydrochloric acid (HCl) has emerged as a promising alternative due to its lower environmental impact and potential for recovery and reuse. HCl is also a by-product of polyurethane production, although it is contaminated with chlorobenzene, which makes it unsuitable for direct use in battery recycling. In line with circular economy principles, this project proposes repurposing this waste HCl stream for LIB recycling, provided the chlorobenzene present at approximately 30 ppm can be removed.

Adsorption was selected as the purification method due to its simplicity, low cost, and scalability. This project focuses on developing an adsorption process to remove chlorobenzene from the HCl stream, enabling its reuse in hydrometallurgical treatment of spent LIBs and contributing to sustainability and resource efficiency.

Activated carbon was selected due to its high surface area, chemical resistance and adaptability to functionalization. The materials were modified with nitrogen-containing precursors (dopamine, melamine, polyethylenimine and urea), as well as acid treatments with HCl and nitric acid, and subjected to thermal treatment to enhance adsorption performance through surface chemistry tuning.

The adsorbents were characterized using N₂ adsorption–desorption isotherms at -196 ºC, elemental analysis, thermogravimetric analysis, and point of zero charge measurements.

Fixed-bed column studies were carried out using HCl solutions containing 30 ppm of chlorobenzene under controlled flow and bed height conditions. Adsorption results showed distinct performances depending on carbon type and treatment. The urea-functionalized activated carbon from Sigma exhibited the best performance, achieving 90% removal efficiency and a maximum adsorption capacity of 0.6 mg/g. This study contributes to strategies for chlorobenzene removal from acidic industrial streams.