Conversion of chrysotile asbestos to smectite

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Title: Conversion of chrysotile asbestos to smectite
Author: Cheshire, Michael C
Abstract: In the United States , chrysotile asbestos is legally declared a carcinogenic health hazard , which requires the removal of all forms of asbestos in all public places . Upon removal , the chrysotile is disposed in landfills ; thus moving the hazard to another relatively secure location . In this study , we are investigating the possibility of altering chrysotile to a non -hazardous mineral , such as smectite , which potentially may be economically viable . Chrysotile from Thetford Mines in Quebec , Canada was treated first with mild organic acids , such as formic and oxalic acids , at concentrations 0 .5 to 2 .0N at 200‹C in Teflon -lined 12 .0 ml Parr bombs . Examination of the reaction products with X -ray diffraction and Analytical Electron Microscopy indicated a poorly crystalline iron -bearing kerolite -type 2 :1 layer silicate with a thin foily morphology was found to form during the acid pretreatment along with significant amounts of amorphous silica . The magnetite impurity in the initial chrysotile asbestos served as the source of iron in the above reactions . Kerolite seems to form from the following reaction : Mg6Si4O10 (OH )8 (S )+6 .02H+ (aq )+0 .54Fe2+ (aq ) ¨ (chrysotile ) (Mg2 .46Fe2+0 .54 )Si4O10 (OH )2 & #8729 ;nH2O (S )+3 .55Mg2+ (aq ) (kerolite ) Subsequently , kerolite was reacted with 0 .2N NaOH for 48 to 96 hours at 200‹C . A highly crystalline smectite was found to form with the same foily morphology as the kerolite precursor . X -ray spectral analyses of the kerolite precursor and smectite suggest the following reaction to take place : (Mg2 .46Fe2+0 .54 )Si4O10 (OH )2 & #8729 ;nH2O (S )+3 .55Mg2+ (aq ) + 0 .54NaOH (aq ) + 0 .01Fe3+ (aq )¨ Na0 .54 (Mg2 .99Fe2+0 .01 ) (Si3 .46 Fe3+0 .54 )O10 (OH )2 (s )+0 .54Si 4+ (aq ) (saponite ) The reaction products , kerolite and smectite , definitely possess a non -hazardous morphology and has promising economic potential .
URI: http : / /hdl .handle .net /2346 /21549
Date: 2003-12


Conversion of chrysotile asbestos to smectite. Master's thesis, Texas Tech University. Available electronically from http : / /hdl .handle .net /2346 /21549 .

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