Enhanced The Inactivation Chlorella Efficiency Of ZnWO₄ By Conjugated Structure Materials

The exotic invasive species from the ballast water in the ship will bring about serious damages to ecosystem.The hydroxyl radicals generated in photocatalysis can inactivate the marine microorganisms effectively,which may be used in the process of ballast water discharge.ZnWO4 as a photocatalytic material has a wide application prospect in bactericidal effects due to its high oxygen evolution potential.Hydroxyl radicals can be generated on its valence band.In addition,it has the advantage of stable chemical properties.So far,the applications of ZnWO4 in the photocatalysis have been greatly limited due to the low efficiencies resulted from the easy recombination of photogenerated charge carriers.This work focus on enhance the photocatalytic and photoelectrocatalytic inactivation efficiency of ZnWO4 by the conjugate structure material.The main results are as follows:1.The experimental results show that ZnWO4 can inactivate marine chlorella in photocatalysis.Then the photocatalytic activities of ZnWO4 were improved by g-C3N4.When the mount of g-C3N4 were 5%,g-C3N4/ZnWO4 exhibited the highest photocatalytic activities.However,the enhancement effect on inactivation chlorella is not obvious due to the low hydroxyl radical yield.2.Under external bias,the deactivation efficiency will be greatly improved because the recombination efficiency of carrier greatly declined.At 3 V bias potential,the deactivation ratio can reach 100%in 10 min,which increase to 3 times as a photocatalytic process.The adsorption energy of OH-on different crystal facts is different.Hydroxyl radical preferred forming on the surface with high OH-adsorption energy.ZnWO4 with exposure of(011)facets exhibited better photocatalytic and photoelectrocatalytic activities than(010)facets.3.The inactivation performance of ZnWO4 electrode was greatly enhanced by GO modification at a low voltage.When the potential greater than 2V,large amounts chlorine evolution in photoelectrocatalysis.In order to avoid this phenomenon,the voltage should not exceed 2V.Chlorella were deactivated by GO/ZnWO4 electrodes at 2 V bias in 8 min under ultraviolet light irradiation,and this duration was economically half the time of deactivation performed by ZnWO4 electrodes.4.In this work,g-C3N4 was selected as cathode electrodes to improve the deactivation efficiency.At 0.7V bias potential,the oxygen reduce reaction(ORR)of g-C3N4 in seawater is two electron reactions and the product is H2O2,which resulted in high inactivation efficiency under ultraviolet irradiation.This work shows that searching an efficient 2e-ORR catalyst is of great importance in improving the ballast water treatment.