Activation And Phase Transformation Of Palygorskite-natural Nano Mineral In Different Reaction Condition

Palygorskite is a chain-layer magnesium-aluminum silicate.Since it was discovered in the 19^th century.It's particles possesses special crystal structure such as one dimension pore structure,special physical-chemical properties such as strong absorbability,colloidal properties,reinforcement in rubber and plastics materials etc.,special crystal morphology such as natural nano-fibre material and special cause of formation,e.g.precipitation in droughty and semi-droughty lake which was related to eruption of tertiary basalts in east China.The study on properties and modification mechanism of palygorskite is important for its performance and prospect in industry.The objectives of the thesis are that explain the transformation of structure and component in different active conditions,investigate the influence of different acid treatment methods on crystal lattice's reconstruction and effect of various metal cations on crystal lattice's reconstruction,compare properties of cation adsorption and removal by three different clay minerals and prepare zeolite using palygorskite as raw material.These study would extend the applied field in nano-material science and increase the economic values of palygorskite.Using palygorskite with dolomite from Xuyi,Jiangsu Province as raw material,after purified,treated in different conditions separately.Then do cation adsorption and removal experiment using acid-activated product.The variation of structure with different activated condition was characterized using X-ray diffraction(XRD),scanning electron microscope(SEM) and thermo gravimetric analysis(TGA),and the componential variation of ions in solution was obtained by atomic absorption spectrometry(AAS) measurement.Main achievements of the thesis is as follows:1) In lower temperature(commonly less than 60℃),the structure of palygorskite is destroyed faintly by hydrochloric acid within 3mol/L concentration.When the temperature increase(commonly more than 70℃),the breakage of structure would strengthen and accelerate distinctly.2) Palygorskite's structure can't be restored when the structure was destroyed completely.This time,most of octahedral cations leached and configuration supported by SiO₄ tetrahedron collapsed.When palygorskite's structure was destroyed partly,that was H⁺ partly substituted for octahedral cations and SiO₄ tetrahedron still retained special construction,the crystal lattice of palygorskite had tendency to be reconstructed.3) The effect of crystal lattice's reconstruction is related to hydrothermal heat of metal cations.The higher hydrothermal heat's value is,the better the effect of crystal lattice's reconstruction is.4) The mechanism of adsorption of cations by montmorillonite,zeolite and palygorskite is various,so there removal ratios vary in certainty salinity solution. The removal ratio of palygorskite is lower than montmorillonite and zeolite's.5) There are two kinds of processes in the reaction between alkali solution and palygorskite.One is shear stress of OH^- on Si-O-Si bond,another is substitution of Na⁺ for octahedral cations and substitution sequence is Al³⁺＞Fe³⁺ (Fe²⁺)＞Mg²⁺.Palygorskite would transform into montmorillonite and analcime.The higher alkali concentration is favorable for emergence of montmorillonite,while the higher temperature is favorable for emergence of analcime.