In situ laboratory X-ray powder diffraction study of wollastonite carbonation using a high-pressure stage

A high-pressure gas stage, recently developed for in-situ X-ray powder diffraction studies of polymer crystallization under CO(2), has been used to observe the carbonation of wollastonite under various temperature/pressure conditions despite the fact that the stage was not designed for use with moisture-containing samples. The rate of carbonation of wollastonite at 60 degrees C was found to be pressure-independent. Additional experiments at 34.5 bar between 43 and 73 degrees C enabled an activation energy of 53 kJ mol(-1) to be determined for the rate-limiting step. This value agrees very well with a published value for the leaching of Ca from wollastonite in acidic conditions and suggests that Ca leaching is the rate-limiting step in wollastonite carbonation at these temperatures. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.