In-situ acidification of electrosterically dispersed alumina suspensions: Effect of coagulant structure

Abstract

The effect of the acidification arising from the hydrolysis of a range of carboxylic acid derivative compounds on the behaviour of electrosterically dispersed alumina slurries has been studied and it has been demonstrated that they can be successfully coagulated in a time-dependent manner. The inherent coagulation rate is determined by a number of factors, including the precise molecular composition and conformation of the coagulant, as well as its concentration and the suspension temperature. For the cyclic compounds, the size of the ring exhibits a significant influence on the coagulation rate with factors that affect the ground and transition state energies responsible for the observed trends. The nature of the atom bonded to the carbonyl carbon also influences the coagulation rate, with substituent hydroxyl groups accelerating the process. These side group entities can adopt a range of spatial arrangements, however certain conformations result in the formation of hydrogen bonds with the attacking water nucleophile. These favourable interactions stabilise the transition state and hence reduce the activation energy.