Avaliação do efeito de diferentes combustíveis na reação de combustão para preparação de titânia visando o desenvolvimento de membranas cerâmicas assimétricas.

Abstract

The obtainment of ceramic powders with particles size and controlled pores to the preparation of ceramic membranes has leaded to a great impulse on the development of proper chemical synthesis methods to the preparation of the powders. Among the various methods studied on the last decades to the preparation of the powders, the combustion reaction method has stood out as promising to the obtainment of powders with good crystallinity and nanometric. In this method the fuel used plays an important role on the physicochemical characteristics of the obtained powders. Thus, this work has as main objective to study the synthesis by conventional combustion reaction evaluating the effects of different fuels (citric acid, aniline, carbohidrazide, oxalic dihidrazide, glycine and urea) in the physicochemical characteristics of the titania powders (titanium oxide), and, for the development of ceramic membranes asymmetric of TiO2/Al2O3 . The methodology was divides within three stages. Stage I consisted on the preparation of the powders, and it is divided in two steps: synthesis by combustion reaction and the characterization of these powders by XRD, adsorption of N2, SEM and granulometric distribution determination. Stages II consisted in the preparation of the membranes and the Stage III consisted in the characterization. The results concerned to Stage I showed that all fuels, with exception of aniline, leaded to the formation of the rutile phases as major phases and anatase as secondary phases and that the size of the crystallite varied between 26 to 65nm. The curves of adsorption/ dessorption and hysteresis presented isothermals that characterizes as mesopores intered (dimension of the pores between 2-50 nm) and this kind of hysteresis indicates the presence of narrow pores cleft shaped. The temperature of the combustion flame was higher to aniline and glycine (900º and 881º). The infrared spectrum indicated the presence of characteristic vibrations of the O-Ti-O connection. The largest diameter of clusters is equivalent was the due to the citric acid (Dmean = 16.36 μm) and samller oxalic dihidrazide (Dmean = 1.91 μm). The results for the Phase II found that better interaction between support / membrane was with the support calcined at 600 ° C, also the dust that had the best adhesion was obtained with urea. The asymmetric TiO2 ceramic membranes that showed the best result was that prepared with urea, glycine and carbohydrazide. Separation processes in contaminated water with asymmetric TiO2 membranes showed great efficiency in terms of separation, above 95%, and all permeate showed low turbidity, less than 1.49 NTU value allowed for drinking water.