Hydrate-Based Method to Remove Cr(III) and Ni(II) in Chromium Hydroxide Sulfate and Nickel Sulfate Hexahydrate Solutions

The hydrate-based method provides a potential method to remove heavy metal ions. In this work, the phase equilibrium conditions of methane hydrate in chromium hydroxide sulfate solutions and nickel sulfate hexahydrate solutions were first measured. The results suggested that the addition of both chromium hydroxide sulfate and nickel sulfate hexahydrate inhibited methane hydrate formation and acted as thermodynamic inhibitors. In addition, the removal efficiencies of both chromium hydroxide sulfate and nickel sulfate hexahydrate were also measured by forming methane hydrate at different hydration time. The results suggested that the chromium hydroxide sulfate removal efficiency reached 82.1% with a 23.7% yield of melting water at 274.2 K with a hydration time of 1 h, while nickel sulfate hexahydrate removal efficiency reached 67.5% with 68% yield of melting water at 274.2 K.

Automated summary

The hydrate-based method is a potential way to remove heavy metal ions. Both chromium hydroxide sulfate and nickel sulfate hexahydrate were found to inhibit methane hydrate formation, with chromium hydroxide sulfate showing a higher removal efficiency.