An easy and economic method for preparing completely reduced basalt glass

Abstract Four basalt glass samples were prepared by fusing basalt rock (powder) with different amounts of sulfur in a platinum crucible at 1550 °C for 30 min. Each melt was quenched in air. Sulfur addition to the basalt powder was changed from 0 to 5, 10 and 15 wt%. The prepared glass samples were pulverized for measuring the Mossbauer spectra by the constant acceleration method. The basalt rock spectrum can be analyzed into four peaks; two sites due to Fe 3+ with octahedral (Oh) and tetrahedral (Td) symmetry, and the other two due to Fe 2+ with Oh and Td symmetry. Pure basalt glass (sulfur-free) consists of four doublets; two of them represent Fe 2+ (Oh) sites and the third represents Fe 2+ (Td); while the fourth doublet belongs to Fe 3+ (Td). The sample containing 5 wt% sulfur has four iron sites also, although there is a slight difference in the relative absorption area when compared with sulfur-free sample. The fraction of Fe 3+ in the 5% sulfur sample was estimated to be only 7.1%; i.e., the fraction of Fe 2+ was 92.9%. Three iron sites present in the 10% sulfur sample, two of them represent Fe 2+ with (Oh) symmetry, while the third one represents Fe 2+ (Td) site. Mossbauer spectrum of 15 wt% sulfur sample is essentially the same as that of the sample which contains 10 wt%. It is noteworthy that the sulfur content shows a linear relationship with the Fe 2+ fraction which is calculated from the Mossbauer spectra of basalt glasses. 7.5 wt% of sulfur is large enough to completely reduce the iron in basalt glass. The reduction of glasses could occur easily and economically using sulfur as a reducing agent. This method is a very easy and economic method for the preparation of completely reduced oxide glass.