Regulation Of Ions On The Degradation Of Reactive Brilliant Blue By Two Laccase Systems

Reactive brilliant blue KN-R is a typical anthraquinones which conventionally applied in dyeing processes,and its effluent is characterized with high COD,strong color and above-mentioned drawbacks.Finding a way to effectively remove reactive brilliant blue has become a top priority,but its effluent contains a variety of salts and metal ions,increasing the difficulty of degradation.Enzyme based degradation of contaminants in wastewater is now emerging.The enzyme associated with dye decolorization is laccase,which contains four copper atoms,is widely present in organisms such as animals,plants,bacteria and fungi.In this paper,the laccase produced by the white rot fungus Trametes versicolor with high redox potential was selected to degrade reactive brilliant blue.Besides,the optimum conditions for degradation of laccase,the regulation of ions on the degradation of free laccase and laccase-VA system and the regulation of other ions on the degradation of laccase-ion systems were investigated.1.Exploring the enzymatic properties of laccase and finding out that the laccase selected in this experiment can withstand high temperature and acidic environments.Find the optimium conditions for laccase degradation of reactive brilliant blue by changing the ambient temperature(30-70 ?),pH(3.5-7),mediator type(VA,HBT,TEMPO,CA and ABTS),reaction time(30-180 min)and the substrate concentration(25-250 mg/L).The experimental results show that when the ambient temperature is 30?,the pH is adjusted to 3.5,the mediator selects violuric acid(VA),and the initial activity of laccase is set to 1 U/mL,the degradation rate of laccase to reactive brilliant blue is highest.With the extend of reaction time,the degradation rate of reactive brilliant blue by laccase inproved different degrees,but the reaction rate decreased gradually.Considering the most efficient use of energy and time,the reaction time of 90 min was selected as the follow-up experiment.In addition,the lower the initial concentration of reactive brilliant blue,the stronger the degradation effect of laccase.In order to explore the degradation ability of laccase on reactive brilliant blue at higher concentrations,the concentration of reactive brilliant blue was set to 100mg/L in subsequent experiments2.Many dyes are complexes formed by organic moieties and metal ions.The effluent also contains a large amount of ions.The presence of ions poses a challenge to laccase degradation dyes.Therefore,it is particularly important to explore the effect of ions on the degradation of reactive brilliant blue by laccase.Herein,we selected seven salts of Na+(SO32-,CO32-,HCO3-,H2PO4-,HPO42-,NO3-,NO2-and Cl-)and eight metal ion sulfates(K+,Mg2+,Mn2+,Cu2+,Zn2+,Fe2+ and Fe3+)for the experiments.The effect of ions on the degradation of reactive brilliant blue by free laccase and laccase-VA system was investigated in the range of 0-10 mmol/L ion concentration.The results show that most of the ions have no significant effect on the laccase degradation of reactive brilliant blue,but a few will promote or inhibit.The additions of Cl-,Fe2+ and Fe3+ at low dosage significantly inhibited degradation rates of reactive brilliant blue decomposed by laccase.The minimum inhibitory concentrations of Fe2+ and SO32-were 5 mmol/L and 0.5 mmol/L,respectively.In addition,we selected five redox-mediating compounds which follow distinct oxidation pathways during the degradation duration of RBBR.There was the highest degradation rate of reactive brilliant blue in laccase-VA system,which was about10%higher than in pure laccase system.The results showed that Mn2+,Cu2+,Zn2+ and NO2+ could promote the degradation rates of reactive brilliant blue decomposed by laccase.So we select these four ions for the subsequent experiments.3.The ions which promoted the degradation of reactive brilliant blue by laccase were selected to synergize with laccase to explore the effect of other ions on the laccase-ion synergistic system.Construct a laccase-Cu2+/Mn2+/Zn2+/NO2-synergistic system,adding seven salts of Na+ in water(SO32-,CO32-,HCO3-,H2PO4-,HPO42-,NO3-,NO2-and Cl-)and eight metal ion sulfates(K+,Mg2+,Mn2+,Cu2+,Zn2+,Fe2+and Fe3+)and CuCl2 and MnCl2.The results showed that the degradation of reactive brilliant blue by laccase and four ions was similar to that of VA,which could significantly improve the degradation rate of laccase to reactive brilliant blue.The overall trend of laccase-ions system after adding other ions is the same as that of laccase-VA system:most ions have no significant difference in the degradation of reactive brilliant blue by laccase-ion synergistic system.The additions of CuCl2,MnCl2,Fe2+ and Fe3+ has a significant inhibitory effect on the degradation.It has less inhibitory effect on the laccase-NO2-synergistic system.In summary,this study shows that the laccase produced by T.versicolor has a wide tolerance range for temperature and pH.Several ions have an inhibitory effect on the degradation of reactive brilliant blue by laccase.When the enzyme and the mediator act synergistically,it will increase its tolerance to inhibitory ions,while the Cu2+,Mn2+,Zn2+ and NO2-ions can significantly promote the degradation of reactive brilliant blue by laccase.And the laccase-ion synergistic system can also increase the resistance of laccase to other ions.These results suggest that in the actual wastewater treatment process,the pH of the water body can be adjusted,and the inhibitory ions can be removed by chelation,so that the laccase can function better.In addition,it can also be considered that using the native Cu2+,Mn2+,/Zn2+ and NO2-ions in the water as mediators to synergize with laccase,which provides a theoretical basis for the commercial application of laccase.