Removal of tannins and polyhydroxy phenols by electro-chemical techniques

Abstract

The removal of tannins and their basic molecules such as catechol, pyrogallol, phloroglucinol and resorcinol was studied by electro-flotation and electro-oxidation techniques. Iron rods and triple oxide (TaO2/RuO2/IrO2) coated titanium rods were used as electrodes for electro-flotation and electrooxidation respectively. Interaction of tannins and polyhydroxy phenols; with iron oxy-hydroxide formed by anodic dissolution of iron was studied by UV-Visible, FT-IR and zeta-potential measurements. GC-MS was used to identify the intermediate compounds formed during electro-oxidation. Catechol, pyrogallol, phloroglucinol and resorcinol were found to be mineralized in the presence of triple oxide (TaO2/RuO2/IrO2) coated titanium electrodes. Catechol and pyrogallol were found to form insoluble organo-metal complexes while resorcinol and phloroglucinol were found to adsorb on iron oxy-hydroxide. The sludge thus formed was simultaneously separated from the aqueous phase by hydrogen bubbles. It was observed that the power consumption is relatively high for electro-oxidation compared with electroflotation. The effects of pH and reaction time on their removal were also studied and the results are discussed. (c) 2005 Society of Chemical Industry.