| Boron slurry is the solid waste generated from boron industry, 30 wt.%-40 wt.% of which are magnesium compounds. Looking for a suitable method for recycling magnesium not only gain economic benefit, but also reduce the production of wastes. Boron slurry is carbonated to afford magnesium bicarbonate liquor. Magnesium oxide obtained after crystallized and calcination cannot meet the industrial demand because the magnesium bicarbonate solution contains a high concentration of boron. In addition, WHO has strict requirements for waste water containing boron. The technology for separation of magnesium and boron in heavy magnesium liquid and boron removal from wastewater of the tailings are two key problems restricting the development of boron mud comprehensive utilization and boron industry.As a nontoxic and environmentally friendly material, microstructure MgO with special shape, large specific surface area, high activity, has been widely used in water treatment, catalysis, medicine, etc. especially suitable for separating magnesium and boron because of its low costs, no introduction of other impurity. Thus, the morphology control of MgO is very meaningful not only for basic research but also for practical application. Three parts of work are done in this research: synthesis of MgO with different morphologies based on chemical precipitation、magnesium oxide adsorption kinetics and thermodynamics properties and the actual application of magnesium bicarbonate liquor and wastewater solution.In the first part, We using magnesium nitrate and potassium carbonate as raw materials to preparing rod-like、lamellar-like and MgO nanoflakes. XRD result reveal that all diffraction peaks of these three samples can be readily indexed to be magnesium oxide. The SBET values of rod-like and lamellar-like are 53.406 m2·g-1 and 79.391 m2·g-1, what’s more, the rod-like MgO had well mesoporous structure. BET results suggest that the specific surface area of MgO nanosheets is 168 m2·g-1 after treated by sonication. Follow-on studys researched in depth to see the influence of ultrasonic power and the mechanism of synthetic MgO nanoflakes the possible synthetic mechanism of MgO nanoflakes was proposed.In the second part, the adsorption performance of different morphologies MgO samples for boron were tested. The best range of pH for boron adsorption is about 10. The reaction rate increases apparently with rising temperature. The pseudo-second-order model is appropriate to represent the adsorption kinetics of boron ions by the MgO. It indicates that the adsorption mechanism might be a chemisorptions process. Isotherm studies suggesting the adsorption process can be well described by Langmuir equation. After calculation, MgO nanosheets exhibited excellent adsorption performance with a maximum sorption capacity of c.a. 87 mg·g-1.In the third part. We try to using MgO nanosheets to save these two problems: separation of magnesium and boron in heavy magnesium liquid. Simulating and real solutions are studied in the paper respectively. In the study of separation of magnesium and boron, MgO nanosheets can remove more than 90% of boron in heavy magnesium liquid after extracting boron and retains most magnesium ion. In the study of boron removal from waste water, the amount of boron in waste water reduce 80%-90% by introducing appropriate amount of MgO nanosheets, The concentration of boron meets the national primary standard after coupled with other post-treatment process. |
