Preparation of dense, ultra-thin MIEC ceramic membranes by atmospheric spray-pyrolysis technique

Indium and its compounds exhibit excellent semiconductor properties however they are suspected carcinogenic to human beings. For the first time, we applied nanofiltration (NF) technology to the separation of indium from a synthetic wastewater as a literature review revealed little information on the treatment of such a waste. In this research, three types of nanofiltration membranes, NTR7450, ES10 and ES10C, were employed to compare their performances under various operating conditions. With increasing indium concentration in the feed solution, the rejection rates decreased in all the membranes, which could be ascribed to concentration polarization and ion-shielding effects. The changes of indium concentration in the permeate (Cp) were then correlated to the concentration factor (CF) during nanofiltration of the feed solution. The experimental results were well predicted by the theoretical analysis. Increase of operating pressure enhanced their rejection rates of indium, which might be attributed to the “dilute effect”. The real rejection (fr) of indium by nanofiltration was found permeate flux dependent. Based on the results obtained, the nanofiltration mechanisms of multivalent cations such as In3+ were delineated and discussed. It was found that most of the models developed from nanofiltration of univalent and divalent cations were still valid for the nanofiltration process of trivalent cations. However, the strong chemical potential of trivalent cations to form complexes in the solution around neutral pH exerted a significant impact on indium rejection rates of the NF membranes. The experimental results suggest a stable performance ofDense ceramic mixed ionic and electronic conducting membranes have been deposited by atmospheric spray-pyrolysis technique onto porous ceramic substrates. Perovskite oxide layers, i.e. manganites La1−xSrxMnO3, ferrites La1−xSrxFe1−y(Co,Ni)yO3, gallates La1−xSrxGa1−y(Co,Ni,Fe)yO3, cobaltites La1−xSrxCoO3 and related perovskites such as lanthanum nickelate La2NiO4 layers have been prepared. The structure, morphology and composition of the layers were characterised by XRD, SEM and WDS, respectively. Density and gas tightness of the layers were studied as a function of deposition process parameters, film thickness (from ∼0.5 to ∼3 μm) and preparation procedure. The presence of cracks and defects due to thermo-mechanical stresses applied during or after the preparation process were correlated with the membrane composition and the corresponding thermal expansion coefficient differences between substrates and membranes. nanofiltration when applied to the semiconductor wastewater, however, acidic conditions should be avoided.