Dye Removal from Colored Textile Wastewater by Poly(propylene imine) Dendrimer: Operational Parameters and Isotherm StudiesThis paper deals with the removal of textile dyes from aqueous solutions by poly (propylene imine) dendrimer (PPI). Direct red 80 (DR80), Acid Green 25 (AG25), Acid Blue 7 (AB7), and Direct Red 23 (DR23) were used as model dyes. The effects of operational parameters on dye removal such as dendrimer concentration, dye concentration, salt (inorganic anions), and pH have been studied at 258C. The Langmuir and Freundlich isotherm models were investigated. In addition, dye desorption of dendrimer was studied. The results indicated that acidic pH supported the adsorption of dyes by dendrimer. Furthermore studies of dye concentration and salt effects exhibited that dye removal percentage by dendrimer was decreased. It was found that the isotherm data of DR80, AG25, and DR23 followed Langmuir isotherm and isotherm data of AB7 followed Freundlich isotherm models. Desorption tests showed that maximum dye releasing of 76.5% for DR80, 84.5% for AG25, 87% for AB7, and 93% for DR23 were achieved in aqueous solution at pH 12. Based on the data of present study, one could conclude that the dendrimer being an environmentally friendly adsorbent with relatively large adsorption capacity might be a suitable alternative for elimination of dyes from colored textile wastewater.
IntroductionDyes make our world beautiful, but they bring pollution. Synthetic dyes are present in many spheres of our everyday life and their application is continuously growing. Organic synthetic dyes have been widely used as colorants in different industries such as textile, paper, color photography, pharmaceutical, food, cosmetic, etc. [1]. More than 0.7 million tons of organic synthetic dyes are produced annually worldwide. In addition, over 10 000 different dyes and pigments have been applied in those industries. Studies indicated that approximately 15% of produced synthetic dyes per year have been lost during manufacturing and processing operations that involve the production and handling with many organic compounds hazardous to living organisms [2][3][4][5][6][7][8][9][10][11][12][13] Dendrimers are a class of macromolecules characterized by a highly branched structure of great regularity, a compact shape, a large number of (reactive) end groups, and room between the branches for taking up guest molecules. In dendrimers synthesis many chemical pathways can be followed, but there are two general strategies. In divergent route [20] the dendrimers is built up from a central polyfunctional core. In a repeated reaction cycle, the building blocks are added layer by layer. Each next cycle led to a higher generation of dendrimer. In the convergent synthesis [21] first complete wedges (dendrons) are prepared, which are subsequently coupled to a central core. Dendrimers have low toxicity and immunogenicity [22]. Some properties of dendrimers provide a wide range of biological applications, e.g., as carriers for cytostatic agents, gene therapy...
