Recovery of boric acid from boronic wastes by leaching with water, carbon dioxide- or sulfur dioxide-saturated water and leaching kinetics

B2O3 was recovered from waste samples such as borogypsum, reactor waste, boronic sludges, waste mud and concentrator waste by leaching processes using distilled water, sulfur dioxide- and carbon dioxide-saturated water. In the leaching processes, temperature, stirring time and solid-to-liquid ratio were taken as parameters. The amount of B2O3 leached increased with increasing temperature and stirring time and it also increased with decreasing solid-to-liquid ratio, but the increase was less than that recorded for the leaching temperature and the stirring time. SO2 saturated water is a more effective leaching solvent than CO2 saturated water for boronic wastes. By the end of the experiments, more than 90% of B2O3 recovery was found as boric acid. In the leaching of boric acid from boronic wastes in water saturated with sulfur dioxide, it was observed that the leaching rate increases with increasing temperature and leaching time. The overall average values of the kinetic parameters were: apparent activation energy (E) 33.2 kJ mol(-1), pre-exponential factor (A) 8.2 x 10(9) min(-1), reaction order (n) 0.97 and rate constant (k) 3.37 x 10(3) min(-1) for the leaching processes of the boronic wastes. (C) 2000 Elsevier Science B.V. All rights reserved.