Suspended and polycaprolactone immobilized Ag @TiO 2 /polyaniline nanocomposites for water disinfection and endotoxin de

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RESEARCH ARTICLE

Suspended and polycaprolactone immobilized Ag @TiO2/polyaniline nanocomposites for water disinfection and endotoxin degradation by visible and solar light-mediated photocatalysis Dhanashri Jayant Gadgil 1 & Vidya Shetty Kodialbail 1 Received: 16 April 2020 / Accepted: 9 October 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020

Abstract In the present study, water contaminated with Escherichia coli (E. coli) cells was photocataytically disinfected using Ag coreTiO2 shell/Polyaniline nanocomposite (Ag@TiO2/PANI) under visible light irradiation. Ag@TiO2/PANI containing 13 weight % of Ag@TiO2 was found to offer maximum disinfection activity. Band gap energy of Ag@TiO2/PANI was found to be 2.58 eV. Ag@TiO2/PANI nanocomposites were efficient in water disinfection in their suspended and immobilized form. Rate of disinfection with Ag@TiO2/PANI was faster than that with Ag@TiO2 nanoparticles. Water containing 50 × 108 CFU/mL cells was completely disinfected within 120 min with 1 g/L Ag@TiO2/PANI nanocomposite. Simultaneous disinfection and endotoxins degradation were achieved. The photocatalytic disinfection of water and endotoxin degradation using Ag@TiO2/PANI nanocomposite under visible light irradiation followed second order kinetics. The nanocomposite also exhibited a good solar photocatalytic activity. Keywords Ag@TiO2 . Photocatalytic disinfection . Endotoxin . Polyaniline . Nanocomposites

Introduction The contamination of drinking water sources by microbes, which may lead to outbreak of diseases, is one of the greatest risks to human health (WHO; UNICEF Progress on drinking water and sanitation 2015 update 2015; Adrian 2014; Mthombeni et al. 2012). Physical and chemical processes which include chlorination, reverse osmosis, and ozonation are commonly adopted disinfection processes. However, several health, economic, environmental, or technical issues are involved in these processes. Photolytic disinfection by using UV (Velez-Colmenares et al. 2011; Oguma et al. 2013) or solar light (Hindiyeh and Ali 2010) is widely employed. Water disinfection by photocatalysis using semiconductor oxides and metal doped semiconductor oxides (Alrousan et al. 2009; Sontakke et al. Responsible Editor: Sami Rtimi * Vidya Shetty Kodialbail [email protected]; [email protected] 1

Department of Chemical Engineering, National Institute of Technology Karnataka Surathkal, Srinivasnagar Post, Mangalore 575025, India

2011; Gamage 2014; Wang et al. 2015; Rao et al. 2016) or modified semiconductor oxides (Rokicka-Konieczna et al. 2019; Porley et al. 2020) have been reported to offer potential advantage in terms of enhanced degradation and eventual mineralization of disinfection byproducts and toxic residues (Malato et al. 2009; Sunada et al. 1998). Studies on water disinfection by photocatalysis have been carried out for different microbial populations (Benabbou et al. 2007; Matsunaga et al. 1985; Chang et al. 2012). However, Escherichia coli (E. coli) is often chosen as the biological indicator of safe dr