Research progress on separation and extraction of rhenium from copper waste acid

Rhenium is a strategic metal that plays a crucial role in the military, aerospace, and aviation fields. Its unique properties have become an indispensable material in aerospace engines. Rhenium metal has almost no independent deposits, and its resources are mainly associated with copper, molybdenum, and other metal ores. Rhenium resources in copper ore are enriched into waste sewage acid after the copper smelting process, making copper sewage acid an important rhenium-containing resource. In addition, rhenium volatilizes into the furnace gas as rhenium octoxide during the high-temperature smelting process of copper concentrate. After dust collection, rhenium enters the acid-making system with sulfur dioxide. The rhenium-containing flue gas is enriched as perrhenate after rinsing and purifying copper in acid. Rhenium recovery from copper acid has become an important research topic in rhenium metallurgy. This study reviews the technical difficulties of rhenium extraction from dirty acid as follows: (1) The content of main metal elements is too low, and the content of rhenium in dirty acid is only 5–40 mg·L−1. (2) The acidity of the dirty acid system is high, and the sulfuric acid content can reach 50–150 g·L−1. (3) There are many impurity elements in the dirty acid system, including copper, arsenic, lead, zinc, molybdenum, and other heavy metals, of which the arsenic content is about 8–15 g·L−1. (4) The amount of dirty acid produced is large, and the daily processing capacity of rhenium extraction is high. Taking a domestic copper smelter as an example, the daily production of dirty acid is 1000 m3. Therefore, it is essential that the daily processing amount of rhenium extraction technology cannot be less than the daily output of dirty acid to avoid storing a large amount of liquid, which increases enterprise costs. The existing separation and extraction methods are described and compared, including chemical precipitation, solvent extraction, ion exchange, and adsorption. The existing problems of each technology are analyzed to provide a reference for developing a separation and extraction technology for rhenium in waste acid. In general, owing to the high price of rhenium at this stage, the current technology can still produce greater corporate benefits. However, from the perspective of pure technology, current industrialized technology still has a large space for development. New technologies, such as coated impregnating resins, bio-based adsorption materials, and ion-imprinted materials, have high development potential in the field of rhenium extraction from dirty acid. In the future, the separation and extraction of rhenium in dirty acid should be developed toward green environmental protection, short process, and high selectivity.