Experimental design of Fenton and photo-Fenton reactions for the treatment of cellulose bleaching effluents Francesc Torrades a , Montserrat P erez a ,H ector D. Mansilla b , Jos  e Peral c, * a Departament d’Enginyeria Qu  ımica, E.T.S.E.I. de Terrassa, Universitat Polit  ecnica de Catalunya, c/Colom 11, 08222 Terrassa (Barcelona), Spain b Laboratorio de Recursos Renovables, Departamento de Qu  ımica Org anica, Facultad de Ciencias Qu  ımicas, Universidad de Concepci on, Casilla 160-C, Concepci on, Chile c Departament de Qu  ımica, Universitat Aut  onoma de Barcelona, Edifici Cn, 08193 Bellaterra, (Cerdanyola del Vall  es), Spain Received 4 November 2002; received in revised form 4 March 2003; accepted 11 June 2003 Abstract Multivariate experimental design was applied to the treatment of a cellulose conventional bleaching effluent in order to evaluate the use of the Fenton reagent under solar light irradiation. The effluent was characterised by the general parameters total organic carbon (TOC), chemical oxygen demand and color, and it was analysed for chlorinated low molecular weight compounds using GC–MS. The main parameters that govern the complex reactive system: Fe(II) and H 2 O 2 initial concentration, and temperature were simultaneously studied. Factorial experimental design allowed to assign the weight of each variable in the TOC removal after 15 min of reaction. Temperature had an important effect in the organic matter degradation, especially when the ratio of Fenton reagents was not properly chosen. Fenton reagent under solar irradiation proved to be highly effective for these types of wastewaters. A 90% TOC reduction was achieved in only 15 min of treatment. In addition, the GC–MS analysis showed the elimination of the chlorinated organic compounds initially detected in the studied bleaching effluents. Ó 2003 Elsevier Ltd. All rights reserved. Keywords: Cellulose bleaching effluent; Chlorinated phenols; Experimental design; Fenton; Solar irradiation 1. Introduction Wastewaters generated by the bleaching of paper pulp contain large concentrations of organic matter. The chlorinated phenols and polyphenolic compounds pre- sent in these types of effluents have been a source of environmental concern due to their toxicity, bio-accu- mulation and carcinogenic potential (Cernakova et al., 1993). This carcinogenic potential increases with the number of chlorine atoms per molecule (Voss et al., 1980). World-wide Kraft mill industry uses two approaches to comply with increasingly strict pollution control regulations. The first approach employs in-plant process modifications such as extended delignification and sub- stitution of elemental chlorine in the bleaching stage. When molecular chlorine is replaced by chlorine dioxide in the elemental chlorine free (ECF) bleaching process, the amount of chlorinated phenols formed decreases. However, small amounts of chlorinated phenols remain in solution even in an chlorine dioxide ECF bleaching sequence. The second approach involves the treatment of wastewaters by physical–chemical processes including chemical oxidation (e.g., ozone). Also, both aerobic and Chemosphere 53 (2003) 1211–1220 www.elsevier.com/locate/chemosphere * Corresponding author. Tel.: +34-93-581-2772; fax: +34-93- 581-2920. E-mail address: jose.peral@uab.es (J. Peral). 0045-6535/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0045-6535(03)00579-4