Study On The Phase Composition, Modification And Decolorization Of The Attapulgite Clay

Attapulgite as a kind of rich silicate natural inorganic non-metal clay mineral with layered structure of hydrous magnesium was gotten a wide attention in many fields because of its unique structure and excellent performance. This study is aim at the Gansu Linze attapulgite clay to qualitative and quantitative analysis of the mineral phase, respectively used the chemical purification method, inner standard method, K value method and the Rietveld method; which composition, structure and properties were characterized by differential thermal analysis(TG-DTA), X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM) and Fourier transform infrared spectroscopy(FT-IR) etc. The thermal and salt-acid-thermal modification of the attapulgite clay and the purified attapulgite, researched under the condition of attapulgite of edible oil decolorization, and study the mechanism of adsorption of different modified. The conclusions are as follows:Gansu Linze attapulgite clay is sedimentary dolomitic attapulgite, mainly composed of SiO2, Al2O3, MgO and CaO chemical constituents, the phases of the AT-2 are quartz, dolomite, attapulgite and clinochlore, the AT-4 are quartz, dolomite and attapulgite and the KX-I are quartz, dolomite, attapulgite clay, muscovite, gypsum and kaolinite. Purified the attapulgite clay by using sodium hexametaphosphate, the crystal almost dispersed become single fibrous bundle, most of which remain a long fibrous, length of about 500nm, part of which was broken for short fibres, with a length of about 150nm, a little short fibrous body are in reunion between 20-25nm in diameter.The inner standard method, K-value analysis and Rietveld method of attapulgite samples in AT2-I attapulgite material content was about 40%. The inner standard method can be used to analyze the crystalline phase, also can analyze the content of non crystalline phase; K value method is widely used in mineral quantitative analysis as a quantitative analysis method of standard oil chemical industry; Rietveld method is a new method of quantitative analysis, by the diffraction peak intensity of figure XRD point fitting calculation, cycle through the use of least squares method to adjusting the experimental parameters, structure parameters and peak shape parameters and other factors, so that the computation of the peak fitted with the actual peak maximum match, can be analyzed simultaneously by Rietveld content of all crystalline minerals, including convex attapulgite ore AT2, AT4 and AT6 bar physical analysis using Rietveld method were 70.1%,50.7% and 43.1%, and the addition of inner standard substance analysis results is only 3%, the proportion of the known two components of Rietveld method for verification, the calculation value and actual value is only 3%.The attapulgite was thermally modified at 400℃ for 1h, surface water, crystal water and Zeolite water were eliminated. At a constant temperature of 80℃, the mineral was modified with 6mol·L-1’s hydrochloric acid, crystal water took place within decrystallization bundle aggregates from carbonate minerals of the breakdown and replacement of the octahedral cations and dissolved in a small amount of Si4+, so that the body produces eight vacancy expand the attapulgite loose, played a role in increasing the ratio of surface area, while at the bleaching temperature, carrots and other structures within the oil β-colored impurities dissociation and destruction, so that oil viscosity decreased and caused accelerate the mass transfer rate of absorption, adsorption capacity increases attapulgite, colored impurities from the solution of the colored group is absorbed quickly, making the bleaching effect of edible oil to achieve the best; attapulgite modified through the activation of Al3+, which act as a negatively charged octahedral effect on the balance and bring positive charge, while under the influence of the solvent, the inter layer attapulgite is dispersed within the structure and stripped that has a large internal surface area, low price and has cation and structural cell layer between large radius weak force, so that the interlayer exchangeable cations, making attapulgite both the changeability and a huge surface area, it has a strong adsorption. Attapulgite purification after thermal modification for 1 hour at 400℃,4 mol·L-1’s acid modified to the ratio of 1:40 at 80℃, the adsorption is better. The specific surface area of the largest show attapulgite in edible oil bleaching process, attapulgite plays a leading role, the higher the content of attapulgite phase, the better adsorption affection.