Investigation of the dissolution kinetics of kaolin in HCl solution

Kaolin with a given size distribution was calcined at 1023 K for 2 h. The calcined samples were digested in hydrochloric acid solutions of known concentration at constant temperatures. The samples taken from the solution at various periods of time were analysed using a complexometric method and the amount of aluminium passed into solution was determined. Experimental data showed that the dissolution kinetics follow the unreacted core model for spherical particles of unchanging size. It was also found that the process is chemical reaction controlled at temperatures ranging from 318 to 369 K with the activation energy of 79 kJ/mol. The surface reaction rate constant, independent of solution concentration, was found to be expressed asks=exp(8.55−9500/T)m/swhere T is absolute temperature in K.