Equilibria and Kinetics of Flotation Chemical Sorption Reactions in Tailings-Seawater Systems

摘要

Submarine tailings placements (STPs) is a viable alternative to land-based waste disposal. The potential environmental impacts of STPs are the results of oceanographic, biochemical, ecological conditions of the site, while the technical conditions of mineral processing has the incredible importance. In order to justify the application of STPs it is crucial to evaluate the tailings as non-toxic materials at the point of disposal. The properties of the tailings are affected by comminution and separation processes, but there is a considerable potential for improving these characteristics through novel approaches to dewatering and flocculation, as well as the recycling of process water and process chemicals. When collector molecules bound to a mineral surface by physical adsorption and exposed to seawater with its much higher ionic strength, significant desorption can occur. By investigating the desorption characteristics of the adsorbed collectors, important information regarding their mobility could be obtained and facilitate improved solutions for chemical recycling or immobilization. By using a second thickening step, a significant amount of the dissolved collector could be concentrated in a relatively small volume. In process plants where both flotation tailings and 'chemically unpolluted' tailings are available, the latter might be used a solid reagent to immobilize the chemicals desorbed from the former. In the present study the equilibria and kinetics of flotation chemical sorption reactions in tailings-seawater systems, as series of adsorption/desorption have been performed for the esterquats-containing collector FLOT 2015 and the calcite-silicates mineral systems. As part of this work, simple and robust analysis procedures have been developed based on a UV spectroscopy. Combined with techniques for direct characterisation of surface adsorbed species, this methodology offers new insight into the faith of flotation chemicals when the tailings are exposed to seawater.