Influence of mechanical activation on the reactivity of natural pyrite in lead (II) removal from aqueous solutions

• The reactivity of pyrite accelerated due to the mechanical activation.
• Structural changes are the main reason for the reactivity enhancement.
• The new surface area is not an effective factor in enhancing the adsorption process.
• Natural pyrite adsorption improved by mechanical activation pretreatment.

Reactivity of mechanically activated natural pyrite in the adsorption of Pb2+ was investigated. The results proved that the exothermic adsorption of Pb2+ onto pyrite changed to an endothermic adsorption onto mechanically activated pyrite. The thermodynamic studies revealed that pyrite reactivity has improved by mechanical activation. Entropy variations verified that the adsorption affinity of Pb2+ onto the mechanically activated pyrite was more than the pyrite. The adsorption isotherm modeling revealed that the Langmuir isotherm fitted well with Pb2+ adsorption onto 20 min mechanically activated pyrite, while the Freundlich isotherm matched Pb2+ adsorption onto natural and mechanically activated pyrite for 100 min.