Table 3.

Comparison between HCl and citric acid.

Property	HCl	Citric Acid
Acid Strength	Strong (complete dissociation)	Weak (partial dissociation)
Leaching Efficiency	High, especially for base metals like Ni, Mn	Moderate, effective for some metals (e.g., Mg, Fe)
Leaching Kinetics	Faster leaching due to high acidity	Slower leaching, especially for less soluble metals
Environmental Impact	Higher, requires careful handling and disposal	Lower, biodegradable and safer to handle
Corrosivity	High, requires corrosion-resistant materials	Low, less corrosion to equipment
Selectivity	Less selective, effective for a wide range of metals	Selective for metals that form stable complexes
Suitability for Multi-Stage Leaching	Effective but may require more frequent replenishment	Suitable, especially for more gentle extraction