Degradation Of Lignin In Papermaking Wastewater By Ferrocene Catalyzed Heterogeneous Fenton Reaction

Lignin is a major cause of leading to pulping black liquor pollution, reducing the content of lignin in black liquor is the main way to reduce the pollution load. Advanced oxidation technology is using a highly active hydroxyl radicals (HO·) to degrade pollutants in waste water. HO·has a strong oxidation performance to oxidize cellulose, hemicellulose, and lignin in pulp and paper effluent. At present, in the field of advanced treatment of paper effluent, Fenton oxidation technology is the most prevailing advanced oxidation technology. In this paper by using of ferrocene (Fc) heterogeneous Fenton reagent to degrade lignin in the effluent, and to research the best degradation conditions of lignin and the major influence factors and reaction mechanism.Selecting guaiacol as the target pollutant, and by means of selecting single variable factor in order to find the best degradation conditions, the results showing that:(1) the influence of pH value. It has a rapid degradation rate once the pH value is less than5. The more acid is in the solution, the faster of the degradation rate. But the change is not obvious when the reaction time is over60min. The time gap decreased small at the degradation rate of90%. As a result that pH value of5is determined;(2) the effect of H2O2concentration. Degradation rate was increased with the concentration of H2O2, and at the concentration of39.18mM/L which was fastest rate It was only need about80min to achieve85%degradation rate. Once exceeding this concentration the degradation rate will be slow down gradually;(3) the influence of the concentration of2,3-DHBA. The comparison of degradation time in different concentrations was:T0.325>T0.163>T0.650. The degradation time of0.325mM/L was faster than the0.163mM/L about30min;(4) the effect of adding quantity of Fc. The degradation rate increased with the adding of Fc dosing quantity. When the quantity was more than0.4g/L, the degradation rate was slow down gradually. But considering the overall situation of degradation, the time gap was only about10min at dosing quantity of0.2g/L,0.3g/L and0.4g/L. So quantity of0.2g/L was determined.Selecting3,4-dimethoxy benzylalcohol (VA) as the target pollutant, under the optimal conditions of degradation experiment, the results was found that it has certain differences of the degradation process between VA and guaiacol. In addition to the longer time relatively, the degradation progress of VA is only "fast-slow" which deferent from the guaiacol process of "slow-fast-slow". The system of2,3-DHBA/Fc/H2O2can effectively improve the degradation rate of VA, under the best degradation condition, the reagent rate is twice with2,3-DHBA/Fe (Ⅲ)/H2O2system.By using of cyclic voltammetry to research the degradation mechanism of Fc heterogeneous Fenton reagent, the results showing that2,3-DHBA can react with Fc+, and Fc+was VAT as Fc, simultaneity generated semiquinone radicals and quinone to effectively promote the Fc heterogeneous Fenton reaction. In the case of no target pollutant, HO· produced by Fc/H2O2or2,3-DHBA/Fc/H2O2system is possible to oxidize Fc, and make the Fc redox peaks disappear.