The kinetics of the dissolution of chlorite as a function of pH and at 25°C

Far from equilibrium, quasi-steady state dissolution rates of an iron rich chlorite (Mg2.76Fe2+1.90Fe3+0.07Al0.97)[Si2.48Al1.52O10](OH)8, have been measured as a function of H+ concentration for the pH range 3 to 10.5 and at 25°C. The rates were determined using a single pass flow through cell and with a time frame for observing the steady state condition of between 10 to 50 days. Rates are independent of the buffers used to control the pH, sample preparation, experimental methodology and chlorite composition. The results were collated with literature values allowing the rate to be expressed as a function of H+ as; logR=−[9.79aH0.49+13.00+16.79/aH0.43] where R stands for the dissolution rate in mol m−2 s−1 and ai refers to the activity of the subscripted aqueous species. When the data for the Al3+ concentration at the outlet was incorporated into the analysis it was found that the rate could also be described by the relationship R=10−10.46(aH+3aAl3+)0.27 which suggests the rate controlling complex is formed via a proton attack of the lattice aluminium.