OPTIMIZATION OF SOLIDIFICATION STABILIZATION TREATMENT OF FERROALLOY WASTE PRODUCTS THROUGH FACTORIAL DESIGN/

Fine solid precipitates from lime neutralisation of liquid effluent st reams from surface finishing operations in stainless-steel processing are treated by cement-based solidification. This process is examined u sing a modified factorial design technique, the Central Composite Rota tional Design. The performance of these solidification/stabilization p roducts was explored in terms of the effect of operational variables s uch as water-to-solids ratio, cement content and curing time which are deemed to be relevant in terms of engineering design practice. In par ticular, an attempt was made to quantify the interactions between thos e critical operational variables which dictate the suitability of the solidification method, Success criteria included leach resistance (for certain metal species) and mechanical strength of the composite produ cts. It has been shown that the CCRD provides a rigorous account of so lidified product behaviour and does so with a reduced requirement for a priori experimental testing. With the aid of this experimental desig n we have also shown an inverse relationship between strength and leac h resistance of the critical constituents,here represented by chromium . (C) 1997 Elsevier Science B.V.