Study On Preparation Of Active Magnesium Oxide By Magnesium Chloride Electrodeposition

Activated magnesium oxide is an important chemical raw material with a large specific surface area and chemical reaction ability.It is specifically manifested in the relaxation of the crystal structure of magnesium oxide,distortion of the crystal lattice,and more defects,and a certain number of groups with different polarities are formed on the surface.The more complete the crystal form of magnesium oxide,the weaker the ability to react with other substances,and the more active low.According to the unique physical and chemical properties of activated magnesium oxide,it has a wide range of applications in adsorption,sterilization,building materials and catalysis.The goal of this thesis is to prepare activated magnesia.First,magnesium hydroxide is prepared by magnesium chloride aqueous solution electrodeposition method,and then activated magnesia is prepared by direct calcination and carbonization and then calcination.The calcination temperature and holding time are adjusted to control the oxidation.Magnesium activity was analyzed and discussed,and the prepared activated magnesium oxide was used as an adsorbent to study the adsorption performance and adsorption mechanism of activated magnesium oxide on heavy metal ions Pb²⁺ in wastewater.The main research contents and results are as follows:In the process of preparing magnesium hydroxide using anhydrous magnesium chloride as the raw material,the addition of a small amount of SO₄^2- to the solution can promote the smooth fall of the magnesium hydroxide from the cathode plate,and the addition of sulfate ions can effectively shorten the hydrogen When the initial shedding time of magnesium oxide is 0.45 g/L,the initial shedding time of magnesium hydroxide is the shortest,about 10minutes.After adding sulfate ions at the same time,crystal dislocations were observed during the growth of magnesium hydroxide,which allowed it to grow with a complete smooth interface growth mechanism.When the active magnesium oxide is prepared by directly calcining magnesium hydroxide,when the calcining temperature is 500℃ and the holding time is controlled at 1h,the prepared magnesium oxide has the highest activity,its maximum iodine absorption value is 127 mg/g,and the citric acid value The minimum is 12.1 s.Magnesium oxide is composed of particles with an average particle size of 27.6 nm and a specific surface area of 51.15 m²/g;when CO₂ is introduced into the magnesium hydroxide slurry to carbonize it into magnesium carbonate,and then calcined to prepare activated magnesium oxide,when When the calcination temperature is 600℃ and the holding time is 0.5 h,the activity of the obtained magnesium oxide is the highest,the maximum iodine absorption value is 139.7 mg/g,the minimum value of citric acid is 32.2 s,and the microscopic morphology can maintain the precursor magnesium carbonate flakes.Like structure,the average particle size is 56.77 nm,the specific surface area is 96.17 m2/g.When the active magnesium oxide prepared by direct calcination of magnesium hydroxide is used as the adsorbent,when the concentration of heavy metal ion lead is 100mg/L,the pH value of the solution system is 6,and the dosage of magnesium oxide is 30 mg,the adsorption equilibrium can be reached within 50 minutes.And the removal efficiency of Pb²⁺ in the heavy metal wastewater solution is the highest,the removal rate of Pb²⁺ can reach 99.21%,and the maximum adsorption capacity is 1633.8 mg/g.Through the isotherm adsorption study,it is found that the adsorption of lead by magnesium oxide is more in line with the Langmuir model,and the calculated theoretical results are similar to the actual experimental results.Through the study of adsorption kinetics,it is found that the adsorption of lead by magnesium oxide is more in line with the quasi-second-order kinetic equation.By characterizing the adsorbed product MgO-Pb,it is found that magnesium oxide can uniformly adsorb heavy metal ion lead,and in the adsorbed product,lead exists in the form of 2PbCO₃·Pb（OH）2 and PbO·PbCO₃·2H₂O.Carbonate comes from the dissolved CO₂ in the solution.Pb（OH）₂ is formed on the surface of the adsorbent after the hydrolysis of magnesium oxide.The formation of PbO is the cation exchange between Pb²⁺ and the adsorbent magnesium oxide.