Electrocatalytic Degradation Of Cellulose On Lead Dioxide Anode

Cellulose is one of the most abundant available renewable carbon sources. Cellulose is a highly crystalline polymer of D-anhydroglucopyranose units jointed together in long chains byβ-1,4-glycosidic bonds. As the gradual depletion of oil and coal sources in the world, substitution of fossil energy by renewable resources is necessary, some researchers around world are interested in how to use cellulose effectively. Recently, there has been an increasing interest in the application of electrochemical (EC) methods for the treatment of organic materials in wastewater. In the electrocatalytic oxidation process, there is no any toxic substance produced, and the oxidation is effectively strong. So this method is called a green chemical method. In this paper, efforts have been made to depolymerize cellulose by electrochemical (EC) method at a mild reaction condition. The self - prepared Pb/PbO₂ electrode was token as anode, two copper were cathodes. The experiment of cellulose degradation was performed in H2SO4 solution at 25°C, and the effects of the current density, reaction time as well as cellulose content on cotton cellulose degradation were investigated.Having analyzed the Pb/PbO₂ electrode by XRD and SEM, the performance of Pb/PbO₂ anode was determined by quasi-steady state polarization curves and cyclic voltammograms. The characterization results indicated that the tetragonalβ-PbO₂ predominantly took place in lead surface by electrodeposition, although a small amount of the lead sulfate was also present, lower porosity in the film of Pb/PbO₂ electrode and a layered structure ofβ-PbO₂ could be found on the surface of the anode. The performance testing results indicated that the overpotential produced by Pb/PbO₂ electrode was obviously high and Pb/PbO₂ electrode had significant effect on degrading cellulose.After electrocatalytic depolymerization of cotton cellulose, the solid samples and filtrate were obtained by filtrating electrolysis solution. The average DP of the solid samples after being cleaned by distilled water and dried under vacuum to give partial depolymerization of cotton cellulose was determined by Ubbelohde capillary viscometer and Mark-Houwink equation. The average DP of degradation cellulose was lower.Comparing the FT-IR spectra of cotton cellulose before and after depolymerization, there was no new group generated after electrocatalytic depolymerization of cellulose. The filtrate was collected and the soluble sugar content was directly measured by DNS method. After extracting filtrate with ethyl acetate three times and concentrating, silica gel column chromatography was used to obtain the pure products. NMR spectra and GC-MS analysis confirmed that the main product of electrolytic depolymerization of cellulose was 5-hydroxymethylfurfural (5-HMF). At the same time, there were many other productions.The analytical results of degradation products suggested the Pb/PbO₂ electrode can make cellulose degradate effectively. The suggested mechanism was given for the further study of cellulose degradation by electrochemical method.