A comprehensive study on the development of ceramic membranes from natural Kashmir clay and its application in pH-mediated removal of Indigo carmine dye

This work reports the comprehensive fabrication, characterization, and application of ceramic membranes prepared from natural and pure Kashmir clay. The membranes were prepared from different raw material sizes (-60, -80, -120, and -200 ASTM mesh), compaction pressures (50–200 MPa), and sintering temperatures (800–950℃), to determine the effect of fabrication conditions on membrane properties. FESEM, XRD, porosity, water permeation, and chemical stability tests were performed for the characterization of the membranes. Depending on the fabrication conditions, the membranes ranged in porosity from 14.45 to 57.05%, pore sizes between 13.05 to 189.96 nm, and water permeability between 0.22 to 37.7 × 10^–8 m³/m².s.kPa. Furthermore, one of the membranes S₃P₄T₁ with a porosity of 28.21%, pore size of 13.05 nm and water permeability of 0.22 × 10^–8 m³/m².s.kPa was used for the removal of an anionic dye, Indigo carmine. The effect of pH (1–11), applied pressure (1–4 bar) and initial concentration of dye (5–100 ppm) was studied on the permeate flux and rejection. The membrane achieved the highest rejection of 98.54% for a dye concentration of 100 ppm, applied pressure of 2 bars and pH 1, revealing the significant influence of pH on dye removal efficiency. Also, the application of Hermia's models identified cake filtration as the main cause of flux decline. These results confirm the suitability of the Kashmir clay membranes for filtration applications.