Interaction of toluidine blue dye with heptamolybdate: UV-visible and ultrafiltration study

摘要

The present work represents the first attempt to apply a polyoxometalates (POMs) type heptamolybdate [Mo_7O_(24)]~(6-) as a complexing agent for the removal of toluidine blue (TB) dye by ultrafiltration. Before ultrafiltration study, the interaction between heptamolybdate and dye was investigated using spectrophotometry UV-visible. It was shown that a metachro-matic complex dye/POMs type 1:6 was formed with a blue shift from 623 to 550 nm indicating the formation of dye H-aggregates. The ultrafiltration process shows that the addition of heptamolybdate to dye solution greatly improved TB retention from 10 to 97%. The heptamolybdate concentration (0-1 mM), NaCl concentration (0.001-1500 mM), CTAB concentration (0.001-10 mM), pH (2-12) and applied pressure △P (2-4 bar) on the dye retention and permeate flux have been investigated. A 25 full factorial design shows that the main influenced factors are CTAB surfactant following by heptamolybdate and salt concentrations.