Acid recovery from industrial effluents: emerging approaches and challenges

Abstract

In recent times, environmental regulatory bodies worldwide have become increasingly stringent and perceptive about the acceptable levels of wastewater discharged from different industries. The acidity of wastewater discharged from various industries is one of the many critical factors that is closely monitored since acidic discharges could have severe consequences on both the discharge site and the surrounding residential area. Handling massive volumes of acidic wastewater has proven to be a significant challenge for industries in metallurgy and electroplating fields. The wastewater discharged from these industries generally contains different acids like hydrochloric acid (HCl), nitric acid (HNO₃), sulfuric acid (H₂SO₄), phosphoric acid (H₃PO₄), and acetic acid (CH₃COOH). This review provides a comprehensive analysis of the various techniques utilized for acid recovery, including diffusion dialysis (DD), electrodialysis (ED), electro-electrodialysis (EED), membrane distillation (MD), nanofiltration (NF), pyrohydrolysis, and solvent extraction. It also covers the characterization of acidic samples using advanced techniques such as infrared (IR) spectroscopy, ion chromatography (IC), UV-vis spectroscopy, mass spectrometry (MS), and nuclear magnetic resonance (NMR) spectroscopy, along with an evaluation of chemical parameters including chemical oxygen demand (COD), total suspended solids (TSS), and total dissolved solids (TDS). Through detailed descriptions, the operational principles of each technique are expounded, emphasizing their relevance in industrial contexts. Additionally, this review carefully examines the industrial advantages and drawbacks of each acid recovery method, offering useful insights into their strengths and limitations. By combining technical knowledge with real-world applications, it serves as a helpful guide for researchers, engineers, and professionals. It presents a clear overview of effective acid recovery techniques and emphasizes the common goal of promoting a cleaner and more sustainable environment.