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.
In order to reuse the tailings of beneficiation, a novel method which mixes and foams cement, micronized tailings powder, calcium stearate, polycarboxylic acid superplasticizer, early strength superplasticizer, HPMC and hydrogen peroxide under certain conditions is proposed in this work. The results showed that the best ratio is as follows: water temperature 50°C, hydrogen peroxide content 6.5%, water to material ratio 0.5, early strength water reducing agent 1.5%, HPMC4/10000, polycarboxylic acid superplasticizer 0.1%, calcium stearate 1.6%, 17% of tailings fine powder. The foamed cement compressive strength is 0.71MPa, dry density less than 260 kg/m3, and no collapse phenomenon, which guarantees good performance.
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