RESEARCH ARTICLE Immobilized Fe (III)-doped titanium dioxide for photodegradation of dissolved organic compounds in water Isaac W. Mwangi & J. Catherine Ngila & Patrick Ndungu & Titus A. M. Msagati & Joseph N. Kamau Received: 1 November 2012 / Accepted: 25 February 2013 / Published online: 26 March 2013 # Springer-Verlag Berlin Heidelberg 2013 Abstract Photocatalytic degradation of dissolved organic carbon (DOC) by utilizing Fe(III)-doped TiO 2 at the visible radiation range is hereby reported. The photocatalyst was immobilized on sintered glass frits with the coating done by wet method, calcinated at 500 °C and then applied in a photodegradation reactor. The addition of a transition metal dopant, Fe(III), initiated the red shift which was confirmed by UV–Vis spectroscopy, and the photocatalyst was activat- ed by visible radiation. X-ray diffraction patterns showed that Fe(III) doping had an effect on the crystallinity of the photocatalysts. Mixtures of DOC and associated coloured solutions were degraded in first-order kinetics, showing that the degradation process was not dependent on intermediates or other species in solution. A reactor with a catalyst coating area of 12.57 cm 2 was able to degrade 0.623 mg of the dissolved material per minute. Exposure of the reactor to hostile acidic conditions and repeated use did not compro- mise its efficiency. It was observed that the reactor regener- ates itself in the presence of visible light, and therefore, it can be re-used for more than 100 runs before the perfor- mance dropped to <95 %. The results obtained indicate that the photocatalyst reactor has a great potential of application for use in tandem with biosorbent cartridges to complement water purification methods for domestic consumption. Keywords Immobilized photocatalyst . Doped titanium dioxide . Dissolved organic compounds . Photodegradation . Spectrophotometric red shift . Kinetics Introduction The presence of dissolved organic matter derived from pharmaceutical, natural or synthetic sources is an emerging water pollutant that is of concern to hydrogeologists and environmental scientists. Dissolved organics pose a problem because they provide a carbon source for bacterial growth, generate odour and cause biofouling on the surface of items used. They are not easily removed in biological wastewater treatment process; thus, there is a need for a treatment process to remove these contaminants from natural and wastewaters (Kochanyt and Bolton 1992). Several methods have been employed for removal of dis- solved organic carbon (DOCs) in water which include adsorp- tion, membrane filtration, cloud point extraction, solvent extraction, co-precipitation, chemical oxidation and complex- ation with some specific metal ions (Yıldız et al. 2011). It has been reported that some of the complex compounds formed are more toxic in nature than the DOCs themselves; hence, such complex formation methods are not appropriate (Ekpete and Horsfall 2011). Among these techniques, solid phase extraction (SPE) which uses of a sorbent that retains the analyte is the most attractive (Chen et al. 2009). SPE is a simple 78technique with numerous advantages as several analytes can be enriched and separated simultaneously (Chen et al. 2009). The SPE material should possess qualities such as high surface area, high purity and good sorption properties including porosity, durability and uniform pore Responsible editor: Philippe Garrigues I. W. Mwangi : J. C. Ngila (*) : T. A. M. Msagati : J. N. Kamau Department of Applied Chemistry, University of Johannesburg, Doornfontein Campus, Doornfontein, P.O Box 17011, 2028, Johannesburg, South Africa e-mail: jcngila@uj.ac.za P. Ndungu School of Chemistry & Physics, University of KwaZulu-Natal, Westville, P/Bag X45001, Durban 4000, South Africa I. W. Mwangi Chemistry Department, Kenyatta University, P.O Box 43844, Nairobi 00100, Kenya Environ Sci Pollut Res (2013) 20:6028–6038 DOI 10.1007/s11356-013-1600-6