Preparation And Characterization Of Environmental Responsive Inorganic Mineral Microcapsules

Microencapsulation is a technique in which the certain active substances are encapsulated in microcapsules by using polymer or inorganic minerals as semi-permeable materials.The active substances within the microcapsules are isolated from the external environment and can be kept stable.Compared with the conventional reactions in homogeneous solution,the reaction efficiency of the active substances within microcapsules is greatly improved because they are controlled in the small area and the reactants or intermediates have a higher concentration in this limited space.In this paper,montmorillonite,titanium dioxide and tourmaline with special physical structure or environmental responsiveness are used as the wall materialsto construct single or multiple environmental responsive microcapsules with Pickering emulsion method,which provides a new technology for environmental engineering.Thewater-in-water montmorillonite microcapsules,nano-TiO₂@montmorillonite microcapsules?photo responsive?of P25 type,paraffin@montmorillonite microcapsules?thermal responsive?and other microcapsules were constructed with the montmorillonite modified by OTAC?eighteen alkyl three methyl ammonium chloride?as the wall material.The micro structure,morphology and adsorption properties of microcapsules,the thermal properties of paraffin@montmorillonite composite phase change thermal storage microcapsules,the photoresponse of P25 type nano-TiO₂@montmorillonite microcapsules and the photocatalytic degradation of organic dyes methylene blue and rhodamine Bwere characterizedby microscope,spectroscopic and thermal analysis techniques etc.The photoresponsive nano-TiO₂ microcapsules and the thermally responsive tourmaline microcapsules were prepared with the nano-TiO₂ of lipophilic type and the black tourmaline?iron rich?as the wall materials.The microscopic morphology,particle size distribution,UV absorption,fluorescence response and thermal response of the prepared microcapsules were characterized by microscope,spectroscopy and thermal analysis etc.The regulatory mechanism of reduction-oxidation conversion between NAD⁺?nicotinamide adenine dinucleotide?and reduced NADHunder the control of external environment?temperature,light,concentration,pH,etc?was investigated by the encapsulation of ethanol dehydrogenase?ADH?within nano-TiO₂ and tourmaline microcapsulesrespectively.Based on the above relevant experimental research,the following conclusions were drawn.?1?Modified montmorillonite microcapsules.The microcapsules with modified montmorillonite as cyst wall are ellipsoid,the size distribution of microcapsules is large that in the range of 30-200?m,the morphology of the crosslinker remained intactly after crosslinking with ethyl orthosilicate?TEOS?as crosslinking agent.The infrared spectra showed that the peak position of mineral structure of the pepared microcapsules is the same as that of raw materials used.The adsorption process of the microcapsules on organic dye methylene blue and rhodamine Bwas accorded with the first-order kinetics equation when the concentration of microcapsules and pH value of the reaction system were regulated,the mixed dyes showed selective adsorption through the adsorption of microcapsules,the adsorption rate of methylene blue was higher than that of rhodamine B.?2?Paraffin@modifiedmontmorillonite composite phasechangeheat storage microcapsules.The optical microscope and scanning electron microscopecharacterization showed that the paraffin core could be effectively protected by the montmorillonite wallmaterial,after dehydration and drying,the structure and morphology could be kept intactly.The FTIR spectra characterization showed that the infrared group peaks of the prepared microcapsules were the same as those of paraffin,modified montmorillonite and other raw materials.Differential scanning calorimetryanalysis showed that the solid-solid phase transition temperature of the prepared microcapsules was close to that ofparaffin,while the solid-liquid phase transition temperature was slightly lower than that of paraffin,the latent heat of phase change of the prepared microcapsules could be regulated by controlling the paraffin content within the microcapsules.Thermo gravimetric analysis showed that the prepared microcapsules did not undergo thermal decomposition or leakage at the room temperature,which had good thermal stability.?3?Nano TiO₂@modified montmorillonite of P25-type composite microcapsules.The optical microscope and scanning electron microscopy characterizationshowed that the OTAC modified montmorillonite wall material could play a good role in the protection of nano titanium dioxide core material,the integrity of structure and morphology of the microcapsules could be maintained after crosslinking and drying with crosslinking agent.The infrared spectroscopic characterization showed that the structural group peaks of the prepared microcapsules were consistent with the characteristic group peaks of the modified montmorillonite,P25 and other raw materials.UV diffuse reflectance and photoluminescence spectroscopy characterization showed that the prepared P25@modified montmorillonite composite microcapsules had good UV absorption and fluorescence response.The single factor experiments showed that the photocatalytic degradation of organic dyes methylene blue and rhodamine B was superior to that of single P25.For mixed dyes,the catalytic efficiency of methylene blue was higher than that of rhodamine B,the process accorded with the first-order kinetics equation.?4?ADH?nano-TiO₂ microcapsules.The microstructure of the prepared nano-TiO₂ microcapsules was spheroidicity,the particle size distribution ranged from about 10-300?m,after crosslinking and drying by the crosslinking agent,the morphology and structure of the microcapsules could still be remained intactly.The ADH enzyme could be encapsulated well within the prepared microcapsules,which ensured the stability of reaction system during the process of biocatalysis experiments.The infrared spectroscopic characterization showed that the infrared structural groups peaks of microcapsules were consistent with the infrared characteristic peaks of the used raw materials.UV diffuse reflectance and photoluminescence spectroscopy characterization showed that the prepared microcapsules had good visible light absorption and fluorescence response property.The single factor experiment showed that the prepared microcapsules had good catalytic performance for tetramethyl benzidineand the catalytic efficiency was higher than the single factor?illumination,concentration,etc?.The NAD⁺ could be reduced to NADH in the presence of ADH enzyme,while under the illumination condition,the reduced NADH could be oxidized to NAD⁺,the biological cycle of reduction-oxidation reaction between NAD+ and NADH was realized,which had an important significance.?5?ADH@tourmaline microcapsules.Optical microscope and scanning electron microscopy characterization showed that the micro structure of the prepared tourmaline microcapsules was spheroidicity,the surface of the microcapsules was rough.The particle size distribution of the prepared microcapsules ranged from about 20-220?m.After crosslinking and drying by the crosslinking agent,the morphology and structure of the microcapsules could still be remained intactly.The infrared spectroscopic characterization showed thatthe infrared structure group peaks of the prepared microcapsules were consistent with the infrared characteristic peaks of the raw materials.The prepared tourmaline microcapsules had strong thermal sensitivity,it has thermoelectric effect under the heating condition.The tourmaline microcapsules showed good catalytic performance for tetramethyl benzidine in the presence of hydrogen peroxide.The ADH enzyme could be well encapsulated within the tourmaline microcapsules.With the participation of ADH enzyme,the NAD+ in the reaction system could be reduced to NADH,then the reduced NADH could be oxidized to NAD⁺ with the participation of hydrogen peroxide,the biological cycle of reduction-oxidation reaction between NAD⁺ and NADH was realized,which had an important significance.