BACKGROUNDAzo and anthraquinone dyes have been successfully decolorized using enzymatic and biomimetic homogeneous systems.(1,2) Hematin, a horseradish peroxidase (HRP) biomimetic, immobilized on chitosan via glutaraldehyde coupling was able to decolorize Alizarin Red S and Orange II solutions. A Doehlert experimental design and response surface analysis was applied to determine conditions for optimal mass of catalyst and catalytic efficiency of the immobilization procedure. RESULTSThe catalysts with supported hematin showed 33% activity (relative to homogeneous hematin as 100%) in decolorization reactions. After six reuses the catalytic activity was maintained at 60% of the initial one. Hematin anchoring to chitosan without alteration of the iron-porphyrin ring was confirmed by ICP, FTIR and UV/visible spectrophotometric methods. In addition, the effect on hematin activity in the decolorization of aminopropyltriethoxysilane (APTS) as a spacer arm' between hematin-glutaraldehyde and chitosan was studied. CONCLUSIONSAn economical heterogeneous catalyst alternative to HRP has been obtained. The spacer arm improves the catalyst's performance with activities as high as 57% relative to homogeneous hematin. These results support the notion that the activity loss of supported hematin is caused by the restricted access to Fe of the bulky phenolic dyes. (c) 2014 Society of Chemical Industry