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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...

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The feasibility of degumming Persian silk with alcalase, savinase, and mixtures of these enzymes with different alcalase/savinase weight ratios (0/1, 0.25/ 0.75, 0.5/0.5, 0.75/0.25, and 1/0 g/L) was investigated. The results were compared with those of soap degumming, which is a common silk degumming process. The effectiveness of parameters such as the treatment time, concentration of enzymes, and liquid ratio on degumming was studied. The enzymatic degumming process was performed at 558C with an operation time of approximately 30 min, whereas the soap degumming process was carried out around the boiling point in 120 min. The evaluation of the data was carried out through the measurement of the weight loss, strength, and elongation of the samples. The optimum amount of sericin removed was 21.52 wt % for alcalase in 30 min, 20.08 wt % for savinase in 60 min, and 22.58 wt % for soap in 120 min. Also, the enzymatic treatment improved properties of the silk yarn such as the strength (33.76 cN/tex for alcalase and 32.03 cN/tex for savinase) and elongation (20.08% for alcalase and 18.42% for savinase). The obtained values were better than the strength (29.90 cN/tex) and elongation (18.59%) from the soap degumming method. Through the use of an enzyme mixture (0.5/0.5 g/L), good weight loss (22.43%), strength (33.22 cN/tex), and elongation (17.74%) were achieved in 30 min. Scanning electron micrographs confirmed and supported the observed data.

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This paper deals with the removal of textile dyes from aqueous solutions by a poly(propylene imine) dendrimer (PPI) as a polymeric nanoarchitecture in single and binary (mixture of dyes) systems. Direct Blue 78 (DB78) and Acid Black 26 (AB26) were used as model dyes. The effects of operational parameters such as dendrimer concentration, contact time, dye concentration, inorganic anions (salts), and pH have been studied on dye removal. Adsorption isotherms (Langmuir, Freundlich, and Tempkin models), adsorption kinetics (pseudofirst order, pseudosecond order, and intraparticle diffusion), and dye desorption were studied in single and binary dye systems. It was found that the isotherm data of DB78 and AB26 in single and binary systems of dyes followed the Langmuir isotherm. Adsorption kinetics of dyes in single and binary dye systems were found to conform to a pseudosecond order model. Desorption tests showed that the maximum dye releases of 93 % for DB78 and 86 % for AB26 in a single system and 90 % for DB78 and 84 % for AB26 in a binary system of dyes were achieved in aqueous solution at pH 12. On the basis of the data of the present study, it can be concluded that the dendrimer as a polymeric nanoarchitecture is an eco-friendly adsorbent with a relatively large adsorption capacity and may be a suitable alternative for elimination of dyes from aqueous media.

Polyvinyl alcohol (PVA)/sodium dodecyl sulphate (SDS)/multi-walled carbon nanotubes (MWCNTs) composite nanofibres with various MWCNT contents (up to 10 wt%) were fabricated by electrospinning process and their microwave absorption properties were evaluated by a vector network analyser in the frequency range of 8-12 GHz (X-band) at room temperature. Scanning electron microscopy analysis of the nanofibre samples revealed that the deformation of the nanofibres increases with increasing MWCNT concentration. Very smooth surfaces of the composite electrospun nanofibres even for nanofibres with concentration of 10 wt% MWCNT have been successfully prepared because of the high stability dispersion of MWCNTs. It was observed that the absorption microwave properties improved by increasing the loading levels of MWCNTs. Finally, the PVA/SDS/MWCNT composite nanofibres sample with 10 wt% content of MWCNT has shown a reflection loss of 15 dB at a frequency of 8 GHz.