Decolorization and mineralization of reactive brilliant orange X-GN was investigated under visible light irradiation (lambda>or=420 nm) by using Fe-Mt/H(2)O(2) as the heterogeneous photo-Fenton reagent. The characterization results (XRD, FTIR, XRF, BET, XPS, UV-vis diffuse spectra) of Fe-Mt suggested that small-sized hydrolyzed iron successfully intercalated into the interlayer spaces of the clay via pillaring. The stability of the Fe-Mt catalyst was evaluated according to the decolorization efficiency for X-GN with used catalyst from previous runs and the concentration of iron ions leached from the solid structure into the reaction solution. The catalytic results showed that at a reaction temperature of 30 degrees C, pH 3.0, 4.9 mmol/L H(2)O(2) and 0.6g/L catalyst dosage, 98.6% discoloration and 52.9% TOC removal of X-GN were achieved under visible irradiation after 140 min treatment. Furthermore, the maximum concentration of dissolved iron ions was 1.26% of the total iron content in the Fe-Mt catalyst after photocatalysis. A halogen lamp as light source has demonstrated that visible radiation can be successfully used for a heterogeneous photo-Fenton process.