Treatment of titanium white waste acid using ceramic microfiltration membrane

The aim of the research was to study the clarification of titanium white waste acid by ceramic microfiltration membrane. The main focus was the effect of high concentration FeSO₄ and flocculant of polyacrylamide (PAA) on the filtration. The influence of operating parameters such as transmembrane pressure, cross-flow velocity, concentration and temperature on filtration process was also investigated. The results showed that hydrated TiO₂ in waste acid can be successfully recovered by ceramic membrane microfiltration and an excellent clarification effect was achieved. The high concentration of FeSO₄ in waste acid complicates the effect of temperature on the filtration process. When the temperature decreased to less than 293 K, crystallization of FeSO₄ may occur in the membrane pores, hence it is difficult to regenerate the membrane. Flocculation by modified PAA, of which the concentration was less than 5 ppm, slightly increased the membrane flux. Further addition of flocculants might cause adsorption fouling of the membrane and resulted in decrease of flux. The membrane flux was also affected by other parameters. Analyses of filtration resistances indicated that the cake resistance was the main component of the fouling resistance and was 68-80% of the total resistance. The analyses gave more quantitative understanding into the effects of the operating parameters on the filtration.