Synthesis of X-type zeolite and their influence on the filtration of dye effluents

In the present study, a clay-based membrane support (m-S), and X-type zeolite, and a composite clay/zeolite membrane (m-ZX) were prepared. Membrane supports in the form of a flat-disc were prepared by uniaxial pressing of a mixture of clay and starch (12.0%, w/w starch/clay). The results of X-ray diffraction confirms the formation of X-type zeolite. While the scanning electron microscopy analysis shows the formation of fine particles with a crystal size between 1.47 and 2.08 mu m with an octahedral shape. The nitrogen adsorption analysis showed that the specific surface area of the membrane support was 0.7655 m(2)center dot g(-1) with an average pore diameter of 122.2 angstrom. While the specific surface area of X-type zeolite was 316.95 m(2)center dot g(-1) with an average pore diameter of 19.7127 angstrom. The initial water permeation fluxes begin with valued of 1,018 and 380 Lm(-2)center dot h(-1) for the membrane support (m-S) and the composite membrane (m-ZX), respectively. On the other hand, the filtration of the Eriochrome Black T (EBT) dye by m-S and m-ZX showed retention percentages of 38% and 69%, respectively. This clearly demonstrates the significant enhancement of retention of the dye on the m-ZX membrane. The points of zero charge (pzc) of the membrane support and X-type zeolite were pHpzc = 8.77 and pHpzc = 10.2, respectively. Filtration of the EBT dye was carried out at a pH of 8.2. This indicates that the membrane surface was positively charged while the EBT was negatively charged. The mechanism of the dye filtration was dominated by the size of the EBT molecule and that of the membrane pores, and also by the adsorption of the dye on the membrane due to the attraction between the negative charge of EBT and the positive charge on the membrane surface.