SULFURIC ACID REGENERATION FROM NICKEL LATERITE PROCESSING: TECHNOLOGIES, PROCESS CHEMISTRY, SCALE-UP CHALLENGES, AND CIRCULAR ECONOMY PERSPECTIVES

Sulfuric acid consumption represents one of the major operational and environmental challenges in nickel laterite hydrometallurgy, particularly in high-pressure acid leaching (HPAL), atmospheric leaching, and integrated purification circuits. Acid regeneration has therefore emerged as a strategic route to reduce reagent costs, minimize waste generation, improve process sustainability, and support the integration of the circular economy. This critical review analyzes the principal sulfuric acid regeneration technologies applied or proposed for nickel laterite processing, including pyrometallurgical decomposition of sulfates, thermal treatment of gypsum and jarosite residues, membrane-based systems, electrodialysis, diffusion dialysis, solvent extraction-assisted recycling, acid recovery from effluents, and hybrid integrated approaches. The review discusses fundamental process chemistry, reaction mechanisms, thermodynamic constraints, impurity behavior, corrosion challenges, energy demand, gas emissions, and integration with downstream hydrometallurgical operations. Particular emphasis is placed on industrial scalability, operational stability, acid purity limitations, residue management, and the gap between laboratory feasibility and commercial implementation. The analysis further examines the role of acid regeneration in reducing environmental liabilities, enabling residue valorization, lowering freshwater and reagent consumption, and improving the long-term sustainability of nickel laterite processing flowsheets within emerging circular economy frameworks.