Abstract
Various vitreous slags including blast furnace slag. convertor slag, coal gasification slag, and synthetic slags were tested to study the effects of alumina on solubilities in M/2 HCL and sodium acetate solution (pH 4.5) and agronomic response of the slags. Alumina in the slags rich in CaO and MgO (O/Si atomic ratio larger than about 3.5) significantly reduced the acetate solubility and SiO_2 uptake by rice plant. On the other hand, the addition of a small amount of alumina to the slags containing less CaO and MgO (O/Si ratio smaller than about 3.2) increased both M/2 HCL and acetate solubilities and tended to improve the agronomic response. Both solubilities and response reached a maximum when the O/Si ratio of the slags was increased to about 3.5 by the addition of alumina. Alumina has been known as an amphoteric oxide. In a slag rich in basic components, alumina may act as an acidic component, combines with silica, and reduces the activity. In acidic slags, alumina may behave as a basic component and thus improves or little reduces the solubilities and agronomic response.
