Journal of Chemical Technology and Biotechnology J Chem Technol Biotechnol 83:1353–1363 (2008) Oxidation of 4-nitrophenol in water over Fe(III), Co(II), and Ni(II) impregnated MCM41 catalysts Suranjana Chaliha, 1 Krishna Gopal Bhattacharyya 1∗ and Parimal Paul 2 1 Department of Chemistry, Gauhati University, Guwahati 781014, Assam, India 2 Analytical Science Division, Central Salt and Marine Chemicals Research Institute, Bhavnagar 364002, Gujarat, India Abstract BACKGROUND: Nitrophenols are toxic constituents of the effluents of petroleum, textile, dye, iron and steel, foundries, pharmaceutical and electrical manufacturing industries. Aromatic nitro compounds are particularly resistant to normal chemical or biological oxidation making them environmentally persistent. Advanced oxidation using appropriate catalysts mineralize these organics to harmless final products. In this work, MCM41-based catalysts incorporating Fe(III)-, Co(II)- and Ni(II)- cations were used for oxidizing 4-nitrophenol in water under variable conditions of reaction time, pH, mole ratio of the reactant and the oxidant, catalyst load, feed concentration, and temperature. RESULTS: The catalysts prepared were characterized with X-ray diffraction (XRD) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), cation exchange capacity (CEC) and atomic absorption spectrometry (AAS) measurements. In typical reaction conditions of temperature 353 K, time 300 min, catalyst load 2 g L −1 and 10 −3 mol L −1 4-nitrophenol, the oxidation was 48.7, 52.2 and 55.2% with H 2 O 2 and 42.5, 56.6 and 60.2% without H 2 O 2 for Fe(III)-, Co(II)- and Ni(II)-MCM41, respectively. Pseudo-first-order kinetics with kinetic constant of 2.0 × 10 −3 to 5.5 × 10 −3 Lg −1 min −1 was proposed along with a possible mechanism. 4-nitrocatechol, 4-nitropyrogallol, 1,2,4-trihydroxybenzene, hydroquinone, acrylic acid, malonic acid, and oxalic acid were identified in the oxidation products. CONCLUSION: Introduction of Fe(III)-, Co(II)- and Ni(II)- into MCM-41 by impregnation produced effective catalysts for wet oxidation of 4-nitrophenol. The catalysts were able to oxidize 4-NP even without the presence of an oxidizing agent. The results suggest that the transition metal loaded MCM41 brings about a more effective interaction between 4-NP molecules and OH radicals.  2008 Society of Chemical Industry Keywords: 4-nitrophenol; Fe(III)-MCM41; Co(II)-MCM41; Ni(II)-MCM41; kinetics; oxidation INTRODUCTION Nitrophenols such as 2-nitrophenol and 4-nitrophenol enter surface water through the effluents from the tex- tile and dyeing industry, iron and steel manufacturing plants, foundries, pharmaceutical manufacturing and electrical/electronic components production factories. 2-nitrophenol and 4-nitrophenol are common con- stituents of the wastewater from a petroleum refinery. 1 Nitrophenols have been identified in primary and sec- ondary effluents of municipal wastewater treatment plants. The general population may be exposed to nitrophenols through the inhalation of ambient air and ingestion of contaminated foods and drinking water. Phenol and its derivatives are known to be toxic and persistent, and a potential threat to the environment. It is precisely for this reason that these compounds have been studied widely in recent years in order to design an efficient degradation pathway for them. 2 Aromatic nitro compounds are particularly resistant to normal chemical or biological oxidation and to hydrolysis because of the electron-withdrawing nitro group, which makes them environmentally persistent. The favoured process is advanced oxidation using appropriate catalysts, which mineralizes organics to harmless final products. 3–6 Transition metal complexes are well-known oxidiz- ing agents for organic compounds in homogeneous processes. However, the main limitation of the appli- cation of these complexes to oxidation reactions is the difficult recovery of the complexes and their short life- times. Immobilization of transition metal complexes in different types of matrices and supports such as char- coal, polymers, zeolites and layered structures (pillared clays and hydrotalcites) either by direct intercalation, ion exchange or encapsulation, has also been inves- tigated. The mesoporous material MCM41 is well ∗ Correspondence to: Krishna Gopal Bhattacharyya, Department of Chemistry, Gauhati University, Guwahati 781014, Assam, India E-mail: krishna2604@sify.com (Received 17 November 2007; revised version received 16 January 2008; accepted 5 February 2008) Published online 22 March 2008; DOI: 10.1002/jctb.1934  2008 Society of Chemical Industry. J Chem Technol Biotechnol 0268–2575/2008/$30.00