The significance of interfacial water structure in soluble salt flotation systems

Flotation of soluble salts with dodecyl amine hydrochloride (DAH) and sodiu m dodecyl sulfate (SDS) collectors has demonstrated that the interfacial wa ter structure and hydration states of soluble salt surfaces together with t he precipitation tendency of the corresponding collector salts are of consi derable importance in explaining their flotation behavior. In particular, t he high concentration of ions in these soluble salt brines and their hydrat ion appear to modify the bulk and interfacial structure of water as reveale d by contact angle measurements and this effect is shown to be an important feature in the flotation chemistry of soluble salt minerals including alka li halide and alkali oxyanion salts. Depending on characteristic chemical f eatures (salt type), the salt can serve either as a structure maker, in whi ch intermolecular hydrogen bonding between water molecules is facilitated, or as a structure breaker, in which intermolecular hydrogen bonding between water molecules is disrupted. For structure making salts the brine complet ely wets the salt surface and no contact angle can be measured. For structu re breaking salts the brine does not completely wet the salt surface and a finite contact angle is measured. In this regard it has been found that sol uble salt flotation either with the cationic DAH or anionic SDS collector i s possible only if the salt is a structure breaker. (C) 2001 Academic Press .