Lithium and cobalt recovery from petroleum produced water using dolomite: impact of pH, temperature, and surface area

Batch reaction experiments were conducted to determine the feasibility and to elucidate the mechanics of lithium and cobalt recovery from petroleum produced water (PW) using dolomite. The results demonstrate that dolomite effectively recovers high concentrations of Li⁺ and Co²⁺ (100 mg/L) from PW even in the presence of several competing metal cations. Additionally, the results support a surface reaction mechanism in which sorbed Co²⁺ and Li⁺ ions onto dolomite surface form carbonate minerals with carbonate ions dissolved from dolomite. The recovery of Co²⁺ (up to 92 %) and Li⁺ (up to 8.5 %) by this reaction mechanism was higher at 50 °C and initial pH 6 using fine dolomite particles (2.5-2.8 μm) than at 25 °C and initial pH 2 using coarse dolomite particles (650-800 μm). The difference in the recovery of Li⁺ and Co²⁺ is due to the different reaction mechanisms controlling Li⁺ and Co²⁺ recovery. Li⁺ recovery is primarily governed by sorption reactions, while Co²⁺ recovery is driven by both sorption and carbonate mineral formation reactions. The results indicate that high temperature promotes the dissolution of dolomite and formation of carbonate minerals on dolomite surface, while high initial pH attenuates the competition of metal cations and H⁺ for the active sites of dolomite. This study demonstrates the critical interplay of dolomite particle size, inter-particle spacing, temperature, and pH in determining the recovery efficiency of Co²⁺ and Li⁺ from PW using dolomite. It reveals a distinct reaction mechanism that diverges from conventional sorption and precipitation pathways associated with the use of inert sorbents and addition of carbonate additives.