| Dyes are widely used in the textile,rubber,plastics and leather industries,but there are residual dyes contaminating the water during the dyeing process.Among other technology,adsorption is an effective method.It has been found that three-dimensional(3D)hierarchical porous nanostructures have attracted much attention in many fields because of their high specific surface area,various structure,unique morphology,and wide pore size range.Borates are widely used in flame retardant,fluorescence,nonlinear optics,battery,adsorption and other fields,which are multifunctional materials.Porous borates have the advantages of good thermal stability,non-toxicity,low cost and renewable,and can be used as an organic dye wastewater treatment.Moreover,it is of great significance for development and utilization of China's abundant boron and magnesium resources in salt lake.Therefore,how to design and develop cheap,high-performance,well-dispersed new adsorbent materials is the key to wastewater treatment.However,there are few reports on 3D hierarchical borate nanostructures,and the synthesis methods are mainly solvothermal and surfactant-assisted hydrothermal synthesis process.In order to broaden the new method for the preparation of 3D borate nanostructures,and to make full use of the abundant boron and magnesium resources and further study the effect of preparation conditions on morphology,structure and adsorption performance,it is of great theoretical significance and application value to carry out the preparation and adsorption properties of novel magnesium borate materials with hierarchical porous structure.In this paper,three kinds of magnesium borates with hierarchical porous nanostructure materials,2MgO·B2O3·H2O,7Mg0·2B2O3·7H2O and 3MgO·B2O3,were prepared by template-free hydrothermal method,phase transformation method and thermal conversion method,respectively.The samples have been characterized by XRD,TGA,FT-IR,EDS,FESEM and FTEM,and their absorption properties of the dye in simulated water were also studied.The specific contents are as follows:(1)The hierarchical porous 2MgO·B2O3·H2O(MBO)microspheres were prepared by a template-free hydrothermal method with Mg(NO3)2·6H2O and NH4B508·4H2O as raw materials.Several groups of controlled experiments were conducted to investigate the effects of boron and magnesium ratio,temperature,solvent and their ratios on the morphology and size of 2MgO·B2O3·H2O magnesium borate.And the crystal growth mechanism was proposed through the effect of time on its morphology.The specific surface area of the microsphere was 93.64 m2/g,and its adsorption properties for Congo red were studied.The results showed that the maximum adsorption capacity of Congo red was 183.15 mg/g,which was well fitted with the pseudo-second-order rate equation and Langmuir adsorption model.Therefore,MBO microspheres can be considered as a promising candidate for wastewater treatment.(2)The active MgO,MgCl2·6H2O and H3BO3 were used as raw materials to crystallize at room temperature to obtain the precursor of Chloramphetite(CP).Then,using CP as raw material,7MgO·2B2O3·7H2O microsphere constructed by flower-like nanostructures was controllably prepared under hydrothermal conditions.In addition,the effects of raw materials,concentration of solution,ultrasonic,surfactants and solvents on the morphology and size of 7Mg0·2B2O3·7H2O were also investigated.The 3MgO·B2O3 hierarchical porous nanostructure was obtained by thermal conversion at 700 ? for 3.5 h.The specific surface area of the hierarchical porous of 7MgO·2B2O3·7H2O and 3MgO·B2O3 were 103.62 m2/g and 46.10 m2/g,respectively.(3)Based on the characterization,the adsorption kinetics,thermodynamics and adsorption mechanism of two kinds of 7Mg0 2B2O3·7H2O and 3MgO·B2O3 flower-like microspheres for CR simulated wastewater were studied.The results showed that the pseudo-second-order kinetic and the Langmuir models are fitted with the adsorption process.The adsorption performance of 7MgO·2B2O3·7H2O is better than that of 3MgO·B2O3,and the maximum adsorption capacity of CR was 202.84 and 170.07 mg/g,respectively.The thermodynamic parameters of adsorption indicate that the adsorption process is prone to spontaneous endothermic process. |
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