Study of Ni sorption onto Tio mine waste rock surfaces

Sorption phenomena are known to play significant roles in metal mobility in mine drainage waters. The present study focuses on sorption phenomena controlling Ni concentrations in contaminated neutral drainage issued from the waste rock piles of the Tio mine, a hematite–ilmenite deposit near Havre-Saint-Pierre, Québec, Canada exploited by Rio Tinto Iron and Titanium. Batch sorption tests were conducted on waste rock samples of different composition and degree of alteration, as well as on the main mineral phases purified from the waste rocks. Sorbed phases were submitted to sequential extractions, XPS and DRIFT studies for further interpretation of sorption phenomena. The results from the present study confirm that sorption phenomena play a significant role in the Tio mine waste rocks, and that the main sorbent phases are the residual ilmenite ore in waste rocks, as well as plagioclase, the main gangue mineral. Sequential extractions suggest that most sorption sites are associated with reducible fractions, and XPS results indicate that Ni is sorbed as the hydroxide Ni(OH)2. The results from the present study provide useful information on sorption phenomena involved in the Tio mine waste rocks and enable further interpretation of Ni geochemistry in contaminated neutral drainage.

Research highlights► The minerals composing the Tio mine waste rocks possess different sorption capacities. ► The plagioclase and ilmenite minerals are the major sorbing phases of the fresh waste rocks. ► Sequential extractions suggest that most sorption sites are associated with reducible fractions. ► XPS studies on sorbed surfaces suggest that Ni is sorbed as the hydroxide, Ni(OH)2. ► The semi-quantitative prediction of sorption capacities of simple mineral assemblages is feasible from the sorption capacities of the individual components.