Recycled wastes as precursor for synthesizing wollastonite

Abstract The application of wollastonite in various industries has attracted the attention of scientists to synthetically produce it. Also, the ecological demands of a healthy and safe environment urged them to utilize the industrial wastes accumulating year after year and threatening the environment. Therefore, three groups of experiments were designed to prepare wollastonite based on the application of natural stone processing wastes and silica fumes as well as pure chemicals. The high degree of fineness of the waste precursors and the presence of impurities in the form of alkali and iron oxides enhanced the formation of wollastonite at 1100 °C. While, the pure precursors failed to give wollastonite even after firing at 1400°C. Different ratios of CaO:SiO 2 comprising 1:1, 1:1.125, 1:1.166 and 1:1.25 were studied. XRD results revealed that the ratio 1:1.125 gives wollastonite as a sole phase. Lower and higher ratios cause the formation of other calcium silicate phases or free cristobalite.