The Technology And Mechanism Of The Preparation Of Nanometer Calcium Carbonate By Using Carbide Slag

Carbide slag is the waste residue of the preparation of acetylene gas from the calcium carbide slag,the main chemical composition is calcium hydroxide.Carbide slag is not only a waste of resources,but also cause serious pollution to the environment.In this paper,using carbide slag as raw materia which froms Shanxi Linfen,nano-calcium carbonate was prepared by using a series of technological studies.The main research contents are as follows:(1)Using calcium carbide slag as raw material and ammonium chloride as the leaching agent,the conversion rate of calcium ions was investigated by changing the concentration,leaching temperature and stirring speed.The optimum extraction conditions were as follows:the initial calcium concentration of the carbide slag slurry was 1.75mol/L;the stirring speed was 900r/min;the leaching time was controlled to40min;the leaching temperature was normal temperature(25?).Under this condition,after the leaching process,the calcium conversion rate can reach more than 88%.(2)The gas-liquid preparation of vaterite shaped calcium carbonate,carbide was studied by orthogonal experiment the CO₂ flow rate,stirring speed,Ca²⁺ion concentration and the effects of carbonization temperature on the calcium carbonate sample size.Best carbonization conditions were the flow rate of CO₂ was 1.5L/h,the stirring speed was 1400r/min,the Ca²⁺ion concentration was 0.25mol/L,and the carbonization temperature was 20 degrees C,the purity of calcium carbonate was97.14%,the average particle size was 50nm-100nm,specific surface area was33.84m²/g and white degree more than 95,under laser particle size analyzer,the data of D₅₀ reached 1.93?m and D₉₀ reached 2.91?m.(3)The cubic calcium carbonate was prepared when triethanolamine was added to 4 percent,and the D₉₀ was 10.61?m.The addition of polyacrylate sodium and magnesium chloride as crystalline control agents,and the spherical calcium carbonate can be prepared that D₅₀was 3.90?m and D₉₀ was 12.68?m.(4)With the EDTA as a crystal control agent,using the orthogonal experiment,the effects of stirring speed,CO₂ flow rate and calcium ion concentration on the particle size of calcium carbonate were discussed.The optimum reaction conditions were as follows:stirring speed was 600r/min,CO₂ flow rate was 2.5L/h,Ca²⁺ion concentration was 1mol/L.The best combination of 232 samples of particle size of D₅₀ reached 2.63?m,D₉₀ reached 4.42?m,by the BET testing,the specific surface area was 27.84m²/g.(5)In this paper,the morphology of the prepared calcium carbonate samples were characterized by XRD,SEM,TEM,IR and laser particle size analyzer.The experimental results showed that the prepared calcium carbonate samples were in accordance with HG/T2226-2010,which provides a theoretical basis and experimental basis for the industrial preparation of calcium carbonate with high added value.