UV-light emitting diodes (UV-LEDs) was used for the photocatalytic degradation of Rhodamine B (RhB) dye to study the various parameters, effectiveness and feasibility for designing of photocatalytic reactor based on UV-LED irradiation in different conditions. The photocatalytic experiments were conducted using 5 UV-LED lights with same specification and Degussa P-25 TiO2 as a photocatalyst. The effects of operational parameters such as catalysts loading, initial dye concentration, pH, addition of H2O2 and effect of metal ions (Zn2+, Ag+, Fe3+, Cu2+ and Cd2+) were studied for the photocatalytic degradation of RhB. A detailed degradation pathway has been suggested, which was based on the electrospray ionization mass spectrometry (ESI-MS) analysis. It was observed that the degradation of RhB occurred via N-de-ethylation process. N-de-ethylated product was further oxidized into acids and alcohols. The complete mineralization of RhB dye (2.08 x 10(-5) M) was confirmed by chemical oxygen demand (COD), total organic carbon (TOC), total inorganic carbon (TIC) and high pressure liquid chromatography (HPLC) analysis. The optimum conditions for higher percentage degradation of RhB dye obtained with amount of catalyst (1.6 g/L), dye concentration (6.26 x 10(-5) M) and pH = 3.05. Results demonstrated that the UV-LED/TiO2 process can effectively degrade RhB dye with optimum conditions. (C) 2011 Elsevier B.V. All rights reserved.