In this research, a proficient method for the synthesis of TiO2/PPy and TiO2/PPy/GO nanocomposites is explored. These nanocomposites were prepared by one-step in situ deposition oxidative polymerization of pyrrole hydrochloride using Ammonium persulfate (APS) as an oxidant in the presence of TiO2 nanoparticles cooled in an ice bath. The obtained nanocomposites were characterized by XRD, TEM, SEM, UV-Vis, and FTIR techniques. The obtained results showed that TiO2 nanoparticles have been encapsulated by PPy with a strong effect on the morphology of TiO2/PPy and TiO2/PPy/GO nanocomposites. The photocatalytic degradation of rose Bengal, and Victoria blue dye was done under different conditions regarding concentration of dye, time of illumination, pH, and dose of the photocatalyst. The maximum photodegradation was found at 7 pH, 20 ppm concentration of VB and 25 ppm of RB dye solution, 800 mg/L for VB and 1600 mg/L for RB amount of photocatalyst, and 120 min irradiation of visible light. Kinetics of photodegradation were investigated for Victoria blue and rose Bengal dye and found first order kinetics.
TopIntroduction
The industrial wastewater containing the various dyes are responsible for water pollution, due to their carcinogenic behaviour. Lots of investigations reported that 10-12% of dyes are used every year in textile industries such as Rose Bengal, Victoria blue, Thymol blue, Caramine, Indigo Red, Red 120, Rhodamine B, Methylene Blue, Eriochrome Black-T (EBT) (Kaur & Singhal 2014; Fox & Duxbury 1993; Mai et al., 2008; Azmi, et al., 1998) of which are major portion (20%) lost during synthesis and processing operations, which enter into water through effluents. The wastewater released from industries contains highly hazardous and coloured pigments which causes serious ill effect on aquatic life and also human beings. Rose bengal is a significant xanthene dye used in textile and photochemical industries whose molecular structure as shown in Figure 1(a). It has severe toxic effects on the human health (Konstantinou & Albanis, 2004; Deng et al., 2013; Xu et al., 2010) and become dangerous contact with skin and causing itchiness, irritation, reddening and blistering. It also affects to eyes causing inflammation, eye redness, itching etc (Wang et al., 2008). Victoria blue is another triphenylmethane derivatized dye which is extensively used in the textile industry. It has been extensively used as textile dyes for silk, wool, and cotton, in the preparation of inks and in the surface-coating and dyeing of paper (Park et al., 2010; Liang et al., 2009; Ferreira & Li, 2001) as colorants in foods, drugs, cosmetics (Saquib & Muneer, 2003), as biological stains, and as anti-infective, antimicrobial, and anthelmintic agents (Li et al., 1999). The photocytotoxicity of triphenylmethane dyes, based on the production of the reactive oxygen species, is tested extensively with the regard to their photodynamic treatment (Deng et al., 2012). In the past, several physical techniques like photodegradation, coagulation, flocculation, reverse osmosis, adsorption on the activated carbon, ion exchange method ultra-filtration and chemical methods like photosensitized oxidation, adsorption (Chen et al., 2007), have been used to reduce the toxic dye effluents from wastewater (Okano et al., 1987; Wang et al., 2012; Wang et al., 2008). These methods are fairly effective in removing pollutants. However, the main drawback of these techniques is formation of secondary waste product which cannot be treated again and dumped as such (Sedlačík et al., 2012)
Titanium dioxide (TiO2) Nanoparticles (NPs) have many excellent properties, such as low cost, simple preparation, good stability, non-toxicity, and better photodegradation ability (Chen et al., 2007), making it a good prospect for application in solar cells (Linsebigler et al., 1995) photocatalysis (Tai et al., 2007), and photocatalytic hydrogen production (Arenas et al., 2013). The wide band gap of pure TiO2 nanoparticles have low sunlight energy conversion efficiency but also a high rate of photogenerated hole and electron recombination. Therefore, improvement of the photocatalytic properties of TiO2 is essential.