Study On The Solubility And Growth Rate Of AlCl₃·6H₂O In AlCl₃-FeCl₃-CaCl₂-HCl-H₂O System

AlCl₃?6H₂O can be used in wastewater treatment,it is also the raw material or intermediate product of producing poly aluminum chloride flocculant,and have widely application in catalyst preparation and precision casting industry.For the AlCl₃?6H₂O preparation craft separating aluminum from the acid leaching solution by the hydrochloric acid method from fly ash,considering the complicated component of fly ash,its acid leaching solution contains many components,including Al3 +?Fe3 +?Ca2 +?Cl – and so on,which cause salt entrainment during crystal separation process of acid leaching solution and the reduction of the final product purity.So the separation of aluminum salt from the fly ash pickling solution is one of bottleneck problem for the industrial application of aluminium salt extraction process from fly ash.Based on crystallization thermodynamics and crystallization kinetics knowledge,combined with the composition of hydrochloric acid leaching solution,this study selected the AlCl₃-FeCl₃-HCl-H₂ O and AlCl₃-CaCl₂-HCl-H₂ O system,adopt the way of combining experimental measurement and numerical simulation,studied the solubility and growth rate of AlCl₃?6H₂O in the AlCl₃-FeCl₃-HCl-H₂ O and AlCl₃-CaCl₂-HCl-H₂ O system at different conditions?temperature?the degree of supersaturation?hydrochloric acid concentration?,which provide theoretical support for the optimization and design of actual process.?1?The solubility of AlCl₃?6H₂O in the FeCl₃-HCl-H₂ O and CaCl₂-HCl-H₂ O system was studied,and the effect of temperature?25-60oC??degree of supersaturation?0-2.5 mol ? kg-1?and hydrochloric acid concentration?1 mol ? kg-1 and 9.9 mol ? kg-1?on the solubility were investigated.The solubility of AlCl₃?6H₂O in FeCl₃-HCl-H₂ O and CaCl₂-HCl-H₂ O systems was determined by static method.Meanwhile,the solubility of AlCl₃?6H₂O in FeCl₃-HCl-H₂ O and CaCl₂-HCl-H₂ O systems was simulated on the OLI platform imbedded bromley-zemaitis activity coefficient model.The results showed that the temperature had no significant effect on the solubility of AlCl₃?6H₂O in FeCl₃-HCl-H₂ O and CaCl₂-HCl-H₂ O systems.The degree of supersaturation has a significant effect on the solubility,with the increase of the concentration of Fe3+ or Ca2+,the solubility of AlCl₃?6H₂O decreases significantly.The hydrochloric acid concentration also has a significant effect on the solubility of AlCl₃?6H₂O,with the increase of hydrochloric acid concentration of the leaching solution,the solubility of AlCl₃?6H₂O also decreases significantly.By comparing the measured and simulated values,the relative error between these values are less than 5%,which verified the applicability of the model in simulating the solubility.?2?The growth rate of AlCl₃?6H₂O in the AlCl₃-FeCl₃-HCl-H₂ O and AlCl₃-CaCl₂-HCl-H₂ O system was studied,and the effect of temperature?25-60oC??degree of supersaturation?0-0.6 mol?kg-1?on the solubility were investigated.The crystallization of AlCl₃?6H₂O was obtained by seed crystallization.Temperature has little effect on the growth rate of AlCl₃?6H₂O.The degree of Supersaturation has a significant effect on the crystal growth rate,with the increase of the concentration of Fe3+ or Ca2+,the growth rate of AlCl₃?6H₂O increases gradually.Meanwhile,the growth rates of AlCl₃?6H₂O in the AlCl₃-FeCl₃-HCl-H₂ O and AlCl₃-CaCl₂-HCl-H₂ O system were simulated by OLI software imbedded MSE electrolyte model.The simulation results trend was consistent with the experimental results trend,but the measured and simulated values of crystal growth rates have any deviation.