Study On The Optimum Condition For The Decolorization Of Simulated Wastewater Containing Reactive Dyes By Laccase And The Immobilization Of Laccase

Reactive dyes are widely used in printing and dyeing industry, and they havesome characteristics such as high chroma, complicated components, harmful to theenvironment and so on. The high concentration organic matter of printing and dyeingwastewater can be quickly catalyzed oxidation by using the enzymatic method, whichhas high treatment efficiency, mild reaction conditions and other advantages. As a kindof polyphenol oxidases, laccase can quickly remove the high concentration organicmatter of dyeing wastewater, and significantly improve the biodegradability ofwastewater, while making dyes from a complex macromolecular degradation of smallorganic molecules. The immobilization of laccase can increase the use efficiency andreduce the cost, and provide technical basis for the treatment of low-degradableorganic wastewater.The experiment on the decolorization of three reactive dyes by using laccase wascarried out, and the experimental conditions were optimized; then the immobilizedlaccase by the new carrier was studied, and was compared with several otherimmobilized laccase.(1) This research was on the decolorization of reactive brilliant blue BES, reactivered X-3B and reactive violet5R by using laccase secreted by white-rot fungi. Theinfluences of several factors including reaction time, concentration of laccase, pHvalue and others on the experiment were investigated, and at the experimentalconditions were optimized; and the effect of metal ions on the decolorization wereinvestigated.The experimental results showed that: at pH=7, temperature=40℃, enzymeinitial concentration=10g/L, reaction time=60min，the decolorization of ReactiveBrilliant Blue BES (50mg/L) is71.4%. While under the same conditions, thedecolorization of Reactive Red X-3B (50mg/L) and Reactive Violet5R (50mg/L) canreach98.99%and99.32%after10min, respectively. Under certain conditions, severalmetal ions were added in the reaction system. Fe2+had strong inhibition to the decolorization of Reactive Red X-3B and Reactive Violet5R, and had totallyinhibition to the decolorization of Reactive Brilliant Blue BES. Cu2+can significantlypromote the decolorization of Reactive Brilliant Blue BES, while smaller effect onReactive Red X-3B and Reactive Violet5R. The other three metal ions such as Mg2+、Mn2+and Na+have minor effect on the decolorization.(2) The immobilization of laccase by the modified fumed silica was studied, andwas compared with the immobilized laccase by the other three carriers includingcopper alginate, chitosan and chitosan-Cu2+. The modified fumed silica was obtained,and its’ surface structure was analyzed by SEM image; then the immobilization oflaccase by the modified fumed silica and the mechanism of immobilization werestudied. The experimental results showed that the activity of the immobilized laccasewas2132.74U/g, and the recovery of enzyme activity reached30.46%.Meanwhile, theabove immobilized laccase was compared with the other three immobilized laccasesuch as the laccase was immobilized on the copper alginate by the embedding method,the laccase was immobilized on the chitosan by the adsorption and crosslinkingmethod, and the laccase was immobilized on the chitosan-Cu2+by the polymericcoordination method; it was found that the laccase was was immobilized on themodified fumed silica has good effect.