Abstract Previous studies have demonstrated the improved membrane properties of ceramic membranes made from thermally modified clays with cationic manioc starch and eggshell residue as additives. Based on the employment of these membranes, the relationship between thermally modified clays’ structure and cross-flow microfiltration using oil-in-water emulsion was studied (North Sea heavy crude oil). Using raw clay (M1) and thermally pretreated clay (M2), tubular ceramic membranes were prepared by the extrusion method. Critical Flux in different concentrations (250, 500, and 1000 mgL−1), fouling mechanisms, and membrane resistance were analyzed. The initial membrane resistance values for M1 and M2 membranes were 2.23 ± 0.32 × 1012 m−1 and 1.72 ± 0.293 × 1012 m−1, respectively. The membrane resistance was reduced by 22% due to the clay modification, which also decreased the contact angle, increased the pore size, and decreased the membrane roughness. Regarding the total organic carbon removal, the M2 membrane had no loss in separation efficiency despite having a slightly larger pore size. These results indicate that the clay-induced structural changes decreased the membrane resistance and improved the permeate flux but did not decrease the oil-in-water emulsion’s separation efficiency.

RESUMO Membranas de microfiltração em cerâmica tubular foram preparadas por extrusão de misturas de argilas naturais (NC) e argilas tratadas termicamente (TC) em diferentes frações com a adição de amido de mandioca catiônico. Estudos anteriores verificaram que membranas contendo TC possuíam maior permeabilidade hidráulica e fluxo permeado do que aquelas que continham somente NC para a aplicação em filtração tangencial. Entretanto, as membranas TC tinham uma baixa resistencia mecânica. Assim sendo, este estudo teve como objetivo aumentar a resistência mecânica sem afetar adversamente seu fluxo permeado e permeabilidade hidráulica. As características físicas, mineralógicas e morfológicas das membranas foram determinadas. As membranas foram usadas para microfiltração de microalga Acutodesmus obliquus com pressão aplicada de 1 bar com taxa de fluxo volumétrica de 250 L/h em uma temperatura de 10 ± 5°C. A eficiência de cada membrana cerâmica foi avaliada em termos de fluxo permeado para água e microalga e permeabilidade hidráulica. A mistura de 70% de TC, 15% de fração de amido e sinterizado em 1150ºC exibiu ótimo desempenho em resistência mecânica (15.1±0.2 MPa), fluxo permeado de água de 522.4±0.3 Kg•m-2•h-1, fluxo permeado de microalga de 114.8±0.8 Kg•m-2•h-1 e permeabilidade hidráulica de 568.0±0.3 Kg•m-2•h-1•bar.

ABSTRACT Tubular ceramic microfiltration membranes were prepared by extruding thermally treated clay (TC) and raw clay (NC) mixtures in different fractions with the addition of cationic manioc starch. Previous studies have verified that membranes containing TC possess higher hydraulic permeability and permeate flow values than those containing only NC for application in crossflow filtration. However, TC membranes had a low mechanical strength. Therefore, this study aimed to increase the mechanical strength without adversely affecting their permeate flow and hydraulic permeability. The physical, mineralogical, and morphological characteristics of the membranes were determined. The membranes were used for microfiltration of Acutodesmus obliquus microalgae with applied pressure of 1 bar with a volumetric flow rate of 250 L/h at a temperature of 10 ± 5°C. The efficiency of each ceramic membrane was evaluated in terms of the permeate flow for water and microalgae and hydraulic permeability. The mixture of 70% TC, 15% starch fractions and sintered at 1150°C exhibited optimal performance in mechanical strength (15.1±0.2 MPa), water permeate flow of 522.4±0.3 Kg•m-2•h-1, microalgae permeate flow of 114.8±0.8 Kg•m-2•h-1 and hydraulic permeability of 568.0±0.3 Kg•m-2•h-1•bar.