Preparation and filtration testing of diatomite filtering layer by acid leaching

Ceramic membrane filter consisting of the filtration layer obtained from natural diatomite particles (finer than 50 μm) by coating onto a large porosity support made of quartz-based materials was fabricated. The coating was achieved by pressure filtration at 5 bar and later sintering applied at 600 °C. The sintered product was leached by the hot acid solution (5 M HCl; 75 °C) for 1 h. The characteristic skeletal structure of diatomite (fine microscopic pores) could be obtained without deforming the structural integrity of coating. Filtration response of the filter was tested in dead-end and periodic pressure filtration modes. The filtered particles were of calcite (finer than 1.5 μm) obtained from a marble factory wastewater stream. The diatomite leaching increased the filtration capacity of the filter media more than two times. The filtrate has high clarity (0.1 NTU turbidity). The coating maintained structural stability during a filtration process performed at 5 bar and backflushing of 4 bar.