Abstract
This paper discusses the preparation of an asymmetric microfiltration carbon membrane made of mineral coal powder and phenolic resin. Tubular supports were obtained via extrusion of a paste prepared by mixing a carbon powder, a solution of phenolic resin and organic additives. The green tubes were cured then carbonized at 700 °C under nitrogen flow. Porous supports with an average pore diameter of 9 μm and 38% porous volume were achieved. The material presents high chemical and mechanical resistances. Experimental data showed that the particle size and homogeneity of the carbon powder are directly responsible of the average pore size and distribution of the final material. Phenolic resin acts as binder, carbon precursor and porosity agent with a constant 25% contribution to the total porous volume. The microfiltration layer was coated by means of the slip casting process, using a suspension of finely ground carbon powder dispersed in a phenolic resin alcoholic solution. Carbonization at 700 °C was necessary to obtain a defect-free layer with an average pore diameter of 0.5 and 25 μm thickness. The membrane material displayed a hydrophobic character. To increase its hydrophilic character, the membrane was oxidized under air at 350 °C for 30 min then tested for industrial wastewater filtration. The membrane’s behavior complied with the Darcy’s law even after oxidation. Nevertheless, the oxidation step changed the hydrophobic character of the membrane to a hydrophilic one. In fact, this treatment had a direct impact on the permeability of the membrane and on the filtration flux of industrial wastewater. The latter increased by a factor of 2.5 to 5. In addition, a total retention in turbidity was achieved with 47% of the organic matter retained by the membrane. Due to a complexation between the organic elements Ca2+ and Mg2+, the retention of these divalent ions was also important.