Study On The Controllable Preparation Of Functional Materials Derived From Two Typical Marine Biomass And Their Performance For Organic Pollutants Removal

The ocean is a rich blue breadbasket and the resources of marine organism are exploited in a variety of ways.Fishery fishing is one of the most direct manners for aquatic economic plants and animals with food value.However,there are still lots of low-value biomass which have not been fully and effectively excavated since no direct economic value,including shellfish shells,a by-product of shellfish aquaculture and Enteromorpha prolifera,a kind of green tide algae,etc.They are mostly disposed as biomass waste in landfills currently,which is not only a huge waste of resources,but also occupies land space and even causes environmental pollution.In fact,shells and Enteromorpha prolifera have broad application prospects as high-quality,cheap and renewable calcium carbonate resources and carbon sources,respectively.This study focuses on transforming mussel shells and Enteromorpha prolifera precursors to derive environmental functional materials through modification.Combined with photocatalytic technology,selecting antibiotics and dyes as model organic pollutants,to verify the performance and mechanism of photocatalytic degradation for organic pollutants by the two marine biomass-based functional materials.The main works are as follows:（1）The calcium carbonate skeleton from mussel shell powders（MSPs）with the treatment of ball milling and calcination was used as the carbonate source and template.The external silver source and MSPs were mixed by ball milling to obtain a series of mussel shell-based photocatalysts via in-situ ion exchange and phase conversion strategy.Various products were derived from distinct MSPs as the difference of alkalinity.Based on numerous the results of characterization methods,compared with the corresponding products synthesized with inorganic reagents,the MSPs-derived products possessed similar purity and crystallinity while owned larger specific surface area and wider response range of visible light.Besides,more active sites existed in the MSPs-derived products through in situ self-doping since retaining trace metal elements of the MSPs precursors,which facilitated visible light absorption and photogenerated carrier separation.The performance for the degradation of organic pollutants under visible light of the silver-based photocatalysts derived from MSPs precursors was more excellent and more stable than those of samples synthesized by inorganic reagents.Among them,Ag₂O/Ag₂CO₃-M exhibited the most prominent degradation efficiency.The complete degradation of 10 mg/L sulfadiazine（SDZ）and methylene blue（MB）solutions were achieved within 40 min and 90 min,respectively.Moreover,compared with Ag₂O/Ag₂CO₃-I which was synthesized by the inorganic reagent,Ag₂O/Ag₂CO₃-M had better stability and reusability according to the result of experiments carried out six cycles of degradation for SDZ.Finally,the presence of oxygen vacancies（OVs）in Ag₂O/Ag₂CO₃-M was confirmed by radical trapping experiments,electron spin resonance（ESR）spectroscopy and density functional theory（DFT）calculations,and the construction of a Z-type heterojunction between the two phases with a built-in electric field at the interface,which is the key to a more efficient photogenerated carrier separation efficiency and thus a more efficient degradation efficiency.Finally,the energy band structure was used to explain the major role of reactive species such as superoxide radical（·O₂^-）and photogenerated hole（h⁺）in the photocatalytic degradation of SDZ.This work provides new insights into the application of waste shells in environmental pollution treatment.Finally,based on the results of tests such as radical capture experiments,electron spin resonance（ESR）spectroscopy and density functional theory calculations（DFT）,and combined with the energy band structure,it was confirmed that the presence of oxygen vacancies（OVs）in Ag₂O/Ag₂CO₃-M and the establishment of built-in electric field at the heterojunction interface,which were the keys to possess more efficient photogenerated carrier separation efficiency,and thus performed more efficient photocatalytic degradation for SDZ.Superoxide radicals（·O₂^-）and photogenerated holes（h⁺）play a vital role in the process of photocatalytic degradation for SDZ.This work provides new insights into the application of waste shells in environmental pollution treatment.（2）Enteromorpha prolifera and polyvinyl chloride（PVC）as carbon sources were carried out co-hydrothermal carbonization of to promote PVC dechlorination.Meanwhile,the hydrothermal carbon-based photocatalysts（EPHBC）with dual activities of adsorption coupled with photocatalysis were controllably constructed by using the co-hydrothermal products as precursors with an additional bismuth source.Various characterization methods were applied to certify the superiority of EPHBC,Firstly,the hydrothermal filtrate-derived photocatalyst（Bi OCl-P）owned larger specific surface area,stronger visible light absorption ability and more superior photogenerated carrier separation efficiency.In addition,compared with the material（Bi OCl-H）prepared by inorganic chlorine source（hydrochloric acid）,OVs defects existed in Bi OCl-P.Moreover,for EPHBC,the introduction of co-hydrothermal carbon（EPHC）developed more abundant OVs and oxygen-containing functional groups on the surface,which is more favorable for the adsorption of pollutants.Various characterisation results confirmed that there was the obvious interaction between the two components of Bi OCl and EPHC in EPHBC,which facilitated the separation of photogenerated carriers.As a result,EPHBC acted superior adsorption and photocatalytic performance compared to both hydrothermal carbon and Bi OCl-P,achieving complete degradation of 10 mg/L of tetracycline（TC）and rhodamine B（Rh B）solutions within 150 min and 120 min,respectively.Furthermore,EPHBC has good stability and reusability.The efficiency of pollutant removal was maintained at around 80%after six cycles experiments of degradation for TC.According to the results of free radical capture experiments and ESR spectra,combined with the energy band structure,confirmed that the reaction process in the photocatalytic degradation of TC by EPHBC contained the dual pathway of free radicals（O₂^-played a dominant role）and non-radicals（¹O₂played a crucial role）.This work provides a new idea for the high-value recycling of Enteromorpha prolifera and waste plastic PVC.