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Oxidants

By Bento, Luis San Miguel
Posted on 2006-09-20    Last edited on 2009-12-11


In some factories, oxidants, as ozone and hydrogen peroxide, are applied as decolourizers. In one cane sugar mill in Venezuela, sugar obtained from first boiling of clarified syrup, is melted and decolorized with addition of hydrogen peroxide (Mendoza and Dichie, 2002). With this process colourants are oxidized resulting in colourless compounds that will remain in the liquor.

It was proved that treating liquors with hydrogen peroxide, the performance of decolourization resins use afterwards will improve (Bento, 2004). During oxidation, aldehydes and color compounds with double bonds react forming acids. This fact will decrease colorants molecular weight and will increase colour removal of colour by ion exchange mechanisms. As unsaturated compounds have a high hidrophobicity, they will be preferentially fixed to resins by hydrophobic inter-action. Some of these compounds have an anionic charge and their fixation to the resin is enhanced (Williams, 1992). During resin regeneration these compounds can switch from hydrophobic to ion exchange fixation mechanism (Bento, 1992). This effect will be the cause of resin poisoning and the rapid decrease of decolorization capacity of styrenic divinil-benzenic resins. By oxidation of these compounds, their fixation to resins by ion-exchange mechanism and their removal from resins, during regeneration, will be easier.

Bibliography

Bento L.S.M. (1992) “Organic and Inorganic compounds influence on the sugar colourant-ion-exchange resin
          inter-action” Proc. of S.I.T. Conf., 201-220
Bento L.S.M. (2004) “Decolorization of sugar solutions with oxidants and ion exchange resins” Proc. of S.I.T.
          Conf.,
Mendoza J., Espejo D. (2002) “Updates on the use of hydrogen peroxide at Central El Palmar”, S.P.R.I. Conf.
          William J.C., Bhardwaj C.L. (1988) “The use of HPLC to investigate the mechanism of resin
          decolorization”, Proc. S.P.R.I. Conf., 37-61

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