treatment of anionic azo dyes contaminated waters by using polymer inclusion membranes

Dyes usually have synthetic origins and complex aromatic molecular structures. they are highly soluble in water. when these colored effluents enter the rivers or any other surface water systems, they upset biological activity. aromatic azo dyes, with the azo group (n=n) comprise about half of the world dye market. azo dyes are also a major class of organic compounds released by many industries such as textile, paper, plastic, leather, cosmetic, food and pharmaceutical industries. these dyes are released into the environment through industrial effluents which are hazardous to ecological systems and public health. azo dye effluents are highly resistant to microorganisms ]1[. polymer inclusion membranes (pims) are a type of liquid membranes with high potentials, homogeneous, transparent, and flexible for separation metal ions, dyes and organic compounds ]2[. polymer inclusion membranes containing 40 wt% cellulose triacetate (cta) as the polymer matrix, 25 wt% triethylamine (toa) as extractant, and 35 wt% plasticizer modifier tributyl phosphate (tbp), for the extraction of methyl orange (mo) from water solution. the optimized pim was able to efficiently extract methyl orange in 120 min from water solution. it was suggested that the presence, which was the main species extracted via an ion pair mechanism with protonated toa by forming (toah+)(mo-) complex. the selectivity of the pim towards methyl orange was tested in the presence of so42-, cl-, no3- and po42-. this pim were used successfully for selective extraction of methyl orange from a various water samples. the loaded pim could be quantitatively back extracted with 0.5 mol l-1 nh4oh. the developed pim was stable for four extraction/back extraction cycles without loss of its extraction capacity for methyl orange. it is found that addition of 1 drop extractant (toa) and 4 drop plasticizer (tbp) to the pim composition improves the stability so that the newly modified pim can be used for eight extraction/back-extraction cycles. the kinetic and isotherm studies revealed that the sorption of methyl orange by the optimized membrane is a chemisorption process.