| As the pollution of dye wastewater is increasingly aggravating,biodegradation technology has been gaining widespread attention for its environmental friendliness and low cost.The acceleration of the biological decolorization process by quinone-based mediators has become a hot research topic.However,the single strain of bacteria with high efficiency and broad spectrum of decolorization and tolerance has been rarely investigated.Moreover,the loss of water-soluble quinone with water in practical application leads to higher cost and secondary contamination.A variety of quinone-based mediator immobilization techniques have been developed,but the selection of carrier materials still needs to be explored and optimized.Membrane materials have a large specific surface area and are capable of adsorbing dyes.S ions in thionite（Fe S2）can accelerate the reduction of dyes when microorganisms can use S ions as electron donor.The immobilization of the mediator in the membrane and Fe S2into the biological decolorization system can break through the previous carrier’s single function of carrying the mediator and realize the joint participation of the mediator and carrier in biological decolorization.In light of the above,this paper takes azo dyes as the target pollutant,and firstly,the screening of decolorization bacteria is carried out to enrich the gene pool of the strains and establish the evaluation system.Secondly,the mediator is immobilized on the surface of PVDF membrane by co-modification method and on the surface of Fe S2by UV light curing method to construct quinone-based mediator material.Finally,the catalytic performance and stability of the quinone-based mediator material for the biological decolorization of this strain were discussed,and it provided a theoretical basis and technical support for the practical application of mediator immobilization in dye biological decolorization.A strain YL16 was isolated from the activated sludge of a printing and dyeing plant with the ability to decolorize azo dyes efficiently.And it was determined that YL16 was Klebsiella pneumoniae by gene sequencing.The effects of strain YL16 on the decolorization performance of different concentrations and structures of azo dyes under different initial p H and carbon and nitrogen source conditions are investigated.The results showed that the optimal conditions were:When p H=7,glucose was used as carbon source and glutamic acid was used as nitrogen source,its decolorization rate reached 100%in 42h incubation.The strain YL16 has a strong tolerance to high concentration（1g/L）of azo dyes for 54h to achieve100%decolorization.In addition,it has a broad spectrum of decolorization,showing good decolorization performance for different structure of azo dyes（Congo Red,Methyl Red,Lichon Red S,Methyl Orange）,achieving complete decolorization within 42,46,42 and 43h,respectively.It indicates that strain YL16 has some advantages in the application of treating high concentration of mixed azo dyes in wastewater.The formulation of the light curing agent was optimized.Epoxy acrylate（EA）and polyurethane acrylate（PUA）were chosen for the prepolymer.TPGDA（tripropyleneglycol diacrylate）was chosen as the monomer and TPO was chosen as the photoinitiator.The effects of different prepolymer ratios and contents and photoinitiator contents on the adhesion,hardness,viscosity,thermal stability and curing rate of the light curing agent were investigated.The results show that:When the ratio of prepolymer EA to PUA is 2:4,the prepolymer content is 65%,the monomer TPGDA content is 25%,and the photoinitiator TPO content is 5%,the comprehensive performance of the formulated photocuring agent is excellent and suitable for the preparation of anthraquinone/Fe S2.Theanthraquinones（1-chloroanthraquinone,2-chloroanthraquinone,1,8-dichloroanthraquinone and 1,4,5,8-tetrachloroanthraquinone）with different numbers and positions of substituents were immobilized on the surface of the film and Fe S2,and the successful immobilization of anthraquinone on the carrier material was confirmed by scanning electron microscopy（SEM）and Fourier Transform Infrared Spectroscopy（FTIR）.The addition of quinone-based mediator materials can accelerate the biological decolorization rate by several times.Among them,1,8-dichloro-anthraquinone mediator film increased the decolorization rate of strain YL16 by nearly 3 times.The complete decolorization of Congo red azo dye was completed within 16h.The addition of 1-chloroanthraquinone and Fe S2shortened the time to fully decolorize the azo dye of strain YL16 from 42h to 20h.The quinone-based mesophilic material maintained a stable acceleration of the biodecolorization system after multiple cycles.It suggests that the structure of the quinone-based mesomaterials did not change during the repeated cycling.The quinone-based mediator material is a stable material for actual decolorization of azo dyes with good biocompatible properties and reuse stability. |
