Remediation and recycling of inorganic acids and their green alternatives for sustainable industrial chemical processes

The uses of inorganic acids as a solvent, leachant, and lixiviant are widespread in many commercially important industrial processes, including mining, metallurgy, metal-processing, nuclear fuel reprocessing, pickling, cleaning, leaching, etching, electroplating, metal-refining, and many others. Unchecked disposal of acidic waste into the environment poses serious threats to the flora and fauna as well as results in corrosion of metallic structures, undesired changes to the pH of soil and water, and many other problems. Because of their potentially harmful effects on the environment, acid recovery from acidic waste solutions is a crucial problem in addition to the resource preservation. Therefore, greener solvent based chemical processes have been gaining increasing attention in recent years. However, it is unclear whether the greener solvent will replace the inorganic acids in the foreseeable future. At present, developing efficient and sustainable methods for recovering and recycling inorganic acids from industrial effluents offers a co-operative approach to lessen the serious ecological disturbances, over exploitations of resources, and financial effects. The recovery and recycling of acids from acidic waste solutions has been proposed using a variety of methods such as solvent extraction, ion exchange resin, membrane technology, or hyphenated technologies which is a combination of two or more integrated technologies. The membrane technology is one option for recovering and recycling of inorganic acids that is easy to use, affordable, and environmentally benign. This is due to the small and straightforward equipment needed, better throughput, and lack of chemical requirements or secondary waste production during the acid recovery process. It is important to note that hyphenated technologies are very effective for zero waste discharge, do not require any further post-processing or chemical agents, along with other advantages inherent to the selected methods. The many procedures for recovering acids and water from waste solutions documented in the literature will be examined in this review, along with their benefits and drawbacks, as well as any problems that need to be fixed before they can be used on an industrial scale.