Process Optimization of Preparing Molybdic Acid from Ammonium Molybdate Solution via Acid Precipitation Based on Response Surface Method
The response surface method was used to investigate the molybdic acid precipitation process by adding sulfuric acid in the ammonium molybdate solution system,as the existing process suffers from low raw material utilization and poor quality and non-uniform particle size of the product.A optimizated quad-ratic polynomial regression model was established for the three process parameters of acid precipitation temperature A,initial MoO3 concentration B,and end pH value of acid precipitation C and their interac-tions,with the molybdenum direct yield Y as the response value.Based on the one-factor experiments,the optimized regression model was obtained as Y=-125.19+5.96A+0.30B-9.80C+4.63×10-4AB+0.92AC-0.07BC-0.048A2-1.87×10-3B2-24.80C2.The experimental results reveal that the molyb-dic acid precipitation process is controlled by multiple factors and sensitive to the response of individual factors with significant interactions.The order of influence significance of single factor is C>A>B,and the order of influence significance of interaction is AC>BC>AB.The optimized acid precipitation condi-tions are as follows:a stirring intensity of 450 r/min,a acid precipitation temperature of 72℃,an initial MoO3 concentration of 70 g/L,an end pH value of 1.09 controlled by the back-addition method,and a heat preservation time of 180 min.Under the above conditions,the average molybdenum direct yield of 94.53%is achieved with a relative standard deviation of only 0.44%.The obtained molybdic acid is of high purity,good morphology,and relatively uniform particle size.
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