Vol.:(0123456789) 1 3 Chemical Papers https://doi.org/10.1007/s11696-018-0442-6 ORIGINAL PAPER Polypyrrole‑coated cotton textile as adsorbent of methylene blue dye Mohamad M. Ayad 1,2  · Wael A. Amer 1  · Sawsan Zaghlol 1  · Islam M. Minisy 3,4  · Patrycja Bober 3  · Jaroslav Stejskal 3 Received: 16 October 2017 / Accepted: 1 March 2018 © Institute of Chemistry, Slovak Academy of Sciences 2018 Abstract Pollution caused by organic dyes is of serious environmental and health concern to the population. Dyes are widely used in textile coloring applications. In the present work, cotton textile was coated with a conducting polymer, polypyrrole (PPy), in situ during the oxidative polymerization of pyrrole. The resulting materials were utilized as easily separated and recy- clable adsorbent for the removal of methylene blue (MB) as a model of cationic dyes in alkaline solutions. It showed also some afnity to remove Acid Green 25 as an anionic dye in acidic medium. The adsorption was assessed by monitoring the decrease in dye concentration by UV–Visible absorption spectroscopy. The infuence of various parameters such as initial dye concentration, contact time, pH, temperature, and adsorbent dose on the adsorption process was studied. The pseudo- second-order kinetic model and Freundlich isotherm model were found to describe the adsorption process. The thermody- namic study revealed that the adsorption of MB by PPy was feasible, spontaneous, and exothermic process. Investigation of the substrate regeneration revealed that PPy deposited on cotton textile can be reused for dye adsorption several times with good efciency and it allows for the recovery of MB for recycling purposes. Keywords Methylene blue · Polypyrrole · Cotton textile · Adsorption isotherms · Adsorption kinetics Introduction Conducting polymers (CPs) (Lay et al. 2016), such as polypyrrole (PPy; Scheme 1), and organic dyes share some common features in the molecular structure. They both include the conjugated structure of single and double bonds that is responsible for optical absorption in the visible part of spectra and, consequently, they are colored. They both include benzene or heterocyclic rings. The basic diference lies in the presence of charge carriers (polarons) in CPs, and their absence in dyes, which are therefore virtually electroni- cally non-conducting. CPs and organic dyes are likely to interact. Conducting forms of polyaniline (PANI) (Bober et al. 2016) and PPy (Alekseeva et al. 2015) are organic salts where the polymer backbone is a polycation and its positive charges are bal- anced by counter-ions aforded by acids (Scheme 1). Many organic dyes include anionic sulfonic group that increases dye solubility in aqueous media. The ionic interaction between both species is thus the frst possibility (Wang et al. 2015). Its nature is pH dependent because properties of CPs and many organic dyes are afected by the protonation. This is demonstrated by the salt–base transition between conduct- ing and non-conducting forms of CPs (Blinova et al. 2007) and similar transition in dyes exploited as acid–base indi- cators. The interaction based on ionic interaction does not afect the conjugated system of both components, and the optical and electric properties then would have an additive contribution of both moieties. The interaction of benzene or pyrrole rings in CPs with rings in dyes constitutes another type to be considered. It is expected to be based on π–π or donor–acceptor electron shifts in the electronic structure. If we accept the hypothesis that such interaction of conjugated systems takes place, it This work was presented at the 81st Prague Meeting on Macromolecules held on September 10–14, 2017. * Mohamad M. Ayad mohamad.ayad@ejust.edu.eg 1 Chemistry Department, Faculty of Science, Tanta University, Tanta 31527, Egypt 2 Institute of Basic and Applied Sciences, Egypt-Japan University of Science and Technology, Borg El Arab, Alexandria 21934, Egypt 3 Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, 162 06 Prague 6, Czech Republic 4 Faculty of Science, Charles University, 128 43 Prague 2, Czech Republic