Kinetics of the dissolution of sand into alkaline solutions: application of a modified shrinking core model

Abstract

The batch dissolution kinetics of sand particles in concentrated alkaline sodium hydroxide solutions was investigated at high temperature and high pressure. The influence of the particle size, the operating temperature (150 -220 jC) and the hydroxide ion molality on the kinetic rate were studied. Experimental data fit well into a developed model based on the shrinking core model approach in which a variable activation energy term was introduced. Kinetic analysis of the experimental results reveals that the associated energy and the rate-controlling mechanism are dependent upon both sample temperature as well as the extent of the reaction.

Physical-chemistry of silica/alkaline silicate interactions during consolidation. Part 1: Effect of cation size

“…For high temperature (150°C), the strong consolidation of materials occurred through dissolution/precipitation reactions. This is consistent with the increase in the solubility of both quartz and amorphous silica as the solution alkalinity and the temperature increase [6][7][8][9][10].…”

A method for phenomenological and chemical kinetics study of autocatalytic reactive dissolution by optical microscopy. The case of uranium dioxide dissolution in nitric acid media

“…Nevertheless, the scale at which these observations were made implies that the conclusions drawn could result from the disturbance of other important phenomena like transport phenomena or bubbling [4]. As fragments dissolve in the absence of these potentially disturbing phenomena, the measurements of dissolution rates in solutions containing various amounts of dissolution products allow to conclude on the existence, or not, of an autocatalyzed mechanism.…”

“…The measured areas are plotted as a function of the sum of the perimeters, according to equation (4). A linear regression, given the time lapse between the images, gives the corresponding dissolution rate.…”

“…Boetker et al [15] studied the concentration gradients and diffusion layer thickness around amlodipine besylate dissolving in water, as well as Østergaard et al [16] for lidocaine dissolution in water and Delwaulle et al [17,18] for copper and uranium dioxide dissolving in nitric acid. Mgaidi et al [4] and Singh et al [19] used it for monitoring the evolution of the morphology of sand and succinic acid crystals during dissolution. The temporal studies vary from the measurement of total dissolution time of sucrose crystals in melted sorbitol by Bhandari et al [2] to more complex studies which used optical microscopy for measuring the dissolution rates of several solids, such as those from Marabi et al [3] for the dissolution rates of pure sucrose spherical particles in water, ethylene glycol, and polyethylene glycol, Forny et al [20] for those of milk powder particles in water, and Dorozhkin [10,21] for single crystals of the natural Khibin (Kola) fluorapatite.…”

“…Dissolution also takes part in many chemical processes in the mining industry [4][5][6][7], batteries [8,9], fertilizer production [10], or the recycling industry [11]. Among these chemical processes, the Purex process is a hydrometallurgical process involving the dissolution of spent nuclear fuels in nitric acid in the head-end steps, before carrying out solvent extraction steps allowing the recovery of uranium and plutonium [12].…”