Development of Composite TiO2 Nanofibers for Treatment of Textile WWT Effluent for Reuse
Textile industry in West Java Indonesia produces large quantity of wastewater with complex pollutants such as dyes and surfactants. Considering the water resources problems such as surface water pollution and decline of groundwater level, advanced treatment for reuse of textile wastewater treatment (WWT) effluent need to be applied. Photocatalytic treatment of UV/TiO2 shows the effectiveness for degradation of organic dye substances, especially with suspended TiO2 catalyst. As for practical reason, catalyst immobilization and nanoscaling were studied intensively in photocatalytic researches instead of suspended catalyst. Due to more catalytic surface area and specific structure, nanofiber based TiO2 photocatalyst considered to be more effective in process performance and practical aspects. Photocatalytic degradation performance of TiO2 nanofibers based catalysts for decolorization of textile dye pollutants were studied in this research.
TiO2 nanofibers was made by electrospinning, with the mixture solution of titanium tetraisopropoxide (1 g), ethanol (4 mL), polyvinyl acetate (1 g) and acetic acid (1 g). Nanofibers was collected in several glass substrates (25 mm x 65 mm). Operational condition adjustment: electrical potential (15 – 25 kV), flow rate (1 – 4 – 8 mL/hr) and tip – collector gap (10 – 15 – 20 cm). TiO2 nanoparticle was synthesized with sol gel method then dip-coated on the glass substrate form a thin film layers. TiO2 nanofibers – nanoparticle composite was made by repeating dip coating method to the nanofiber covered glass. All catalysts were covered by silicon rubber and annealed at temperature 500oC for 30 minutes.
Laboratory batch photocatalytic experiment was carried out by using 1 L photoreactor with 3 x 15 watt UV-C lamps (Vilbert and Lourmat) by 365 nm wavelength (Figure. 1). Glass substrates covered with catalyst were arranged horizontally in 400mm x 100mm x 25mm compartment containing dye aqueous solution as artificial textile wastewater. Reactive black 5 azo dyes (Sigma Aldrich) was used as dye stuff.
Surface morphologies and structures of TiO2 nanofibers, nanoparticle films and composite were investigated by Scanning Electron Microscope/SEM (JEOL, JSM 6360 LA). Composition and distribution of composite TiO2 nanofibers was determined by Energy Dispersive X-ray Spectroscopy/EDXS (JEOL, JSM 6360 LA). Degradation of dye concentration during photocatalytic treatment was measured by UV – vis spectrophotometer (Milton Roy 21-D).
Results and Discussion
Continous TiO2 nanofibers was obtained by adjusting electric potential, flowrate and spinnerete – collector gap in optimum condition: 20 kV, 4 ml/hr and 15 cm, respectively. Figure. 1 shows the SEM images of annealled TiO2 nanofibers, TiO2 nanoparticle film and composite (nanofibers – nanoparticle). As-spun TiO2 nanofibers was formed in diameter range of 400 – 1000 nm and after annealing was decreased into diameter range of 200 – 500 nm due to the removal of organic fraction.
Figure. 1. (a) TiO2 nanoparticle; (b) TiO2 nanoparticle film; (c) compositeFigure. 1c shows SEM image of composite TiO2, developed by coating TiO2 nanoparticle on TiO2 nanofibers in order to increase the effective photocatalytic surface area and to enhance the photocatalytic activity. Annealed TiO2 nanofibers was covered by TiO2 nanoparticle film with particle diameter less than 50 nm.
Figure. 2 Photocatalytic dye degradation: (a) artificial; (b) WWT effluent
Figure. 2a shows photocatalytic dye degradation of artificial dyeing wastewater as the function of UV irradiation time, with initial dye concentration 10 mg/L and pH 11 (optimum). Dye degradation percentage obtained by composite TiO2 was 94.4% after 1 hr of treatment, higher than that of TiO2 nanofiber (75.5%), nanoparticle (74.1%) and bare glass ( 29.4%) After 2 hrs of UV irradiation, the entire catalyst show significant dye degradation more than 95% (99.1% for composite TiO2). Photocatalytic dye degradation activity of composite TiO2 nanofibers – nanoparticle to the textile WWT effluents is shown in Figure. 2b. Significant dye degradation efficiencies were shown, 94,9% (industry A) and 84,2% (industry B) after 2 hours of treatment.
Photocatalytic dye degradation are electron photoexcitation in semiconductor, followed by formation of electron holes pairs on catalyst surface. Very oxidative holes then able to oxidize dyes . H2O decomposition and holes reaction with OH‾ are also play a role in formation of hydroxil radicals, which very powerful in degrading organic dye substances. Radicals formation is affected by many aspects including adsorption capacity of catalysts. SEM images shows that nanofibers own a macropores structure, in other side nanoparticles own a nanopores structure. Macropores cause the faster adsorption of dye molecules in shorter time, then for longer time dye molecules diffused furthermore into nanopores. Nanofiber – nanoparticle composite has both of macropores and nanopores, causing a higher dye adsorption compared to others.
TiO2 nanofibers was well developed by electrospinning at optimized conditions obtained at electrical potential 20 kV, flow rate 4 mL/hr and tip – collector gap 15 cm. Diameter range of annealed TiO2 nanofibers was from 200nm – 500 nm and found effective as photocatalyst material for decolorization of textile dye pollutants. Composite TiO2 nanofibers – nanoparticle was found enhance dye degradation efficiency than that of TiO2 nanofibers and TiO2 nanoparticle film in photocatalytic process, treating artificial dye wastewater as well as real textile WWT effluent
LIST OF RESEARCH OUTPUT
- Development of TiO2 nanofibers for photocatalytic treatment of textile dye pollutants, Doni Sugiyana, Marisa Handajani, Suprihanto Notodarmojo, Proceeding of Seminar 5th AOTULE International Postgraduate Students Conference on Engineering, Bandung 1 – 2 November 2010
- Degradation of Reactive Black 5 and Acid Red 4 by Photocatalytic Treatment by Using TiO2 photocatalyst, Bambang R. Sunoko, Master Thesis at Environmental Engineering ITB
HEAD OF RESEARCH TEAM: Prof. Ir. Suprihanto Notodarmojo Ph.D
TEAM MEMBERS: Dr-Ing. Ir. Marisa Handajani, ST.
OFFICIAL ADDRESS: Program Study Environmental Engineering, Faculty of Civil and Environmental Engineering, Institut Teknologi Bandung