| As plastic products have a wide range of uses in daily life and various industries,they bring convenience to people’s lives.However,with the use of plastic products,phthalates have caused non-negligible pollution of water bodies.As an endocrine disruptor,phthalates threaten human health.In recent decades,with increased awareness of the energy crisis and environmental degradation,the development of green and renewable energy sources has become a hot topic,especially solar energy.Solar-driven semiconductor photocatalysts can decompose aquatic hydrogen,catalyze the degradation of organic pollutants or convert solar energy into other forms of energy for a range of applications.Nevertheless,the photocatalytic efficiency of a single semiconductor photocatalyst is usually not high due to the insufficient utilization of solar energy by the single semiconductor photocatalyst,and subsequently it has been found that strategies can effectively enhance the photocatalytic performance of a single catalyst,such as morphological adjustment,elemental doping,construction of heterojunctions and ion doping.Therefore,the search for a more efficient and green photocatalytic material has gradually become a hot research topic.In this study,a new photocatalytic material Bi/Bi2O2CO3/Bi2S3 was successfully prepared and applied to the removal of the priority control organic pollutant butyl benzyl phthalate(BBP)by modifying bismuth carbonate(Bi2O2CO3)with bismuth sulfide(Bi2S3)heterojunction and noble metal doping.The main contents and conclusions are as follows:(1)A new photocatalyst Bi/Bi2O2CO3/Bi2S3 composite was successfully prepared by a one-step hydrothermal method with simple,easy and time-saving preparation.The morphological characteristics,phase information,elemental distribution,optical properties and charge separation properties of the composite was investigated by means of characterization techniques.The Bi/Bi2O2CO3/Bi2S3 composite was clearly composed of Bi2O2CO3 in flakes and Bi2S3 in rods and Bi by X-ray diffraction(XRD),scanning electron microscopy(SEM)and high-resolution transmission electron microscopy(HRTEM)analysis.The elemental composition,valence and distribution of Bi/Bi2O2CO3/Bi2S3 composite was analyzed by X-ray photoelectron spectroscopy(XPS),and the test results showed that the individual elements of Bi/Bi2O2CO3/Bi2S3 were uniformly distributed.The UV-visible diffuse reflectance(UV-vis)test proved that the Bi/Bi2O2CO3/Bi2S3 composite has a broader range of light absorption.Solid-state fluorescence(PL),photocurrent chemistry test(PEC)and electrochemical ac impedance spectroscopy(EIS)illustrate that the Bi/Bi2O2CO3/Bi2S3 composites have better electron-hole separation efficiency,higher photocurrent response and faster charge transfer rate.(2)The photocatalytic performance of Bi/Bi2O2CO3/Bi2S3 composite was investigated.The effects of pollutant concentration,catalyst concentration and p H on the photocatalytic efficiency were investigated by single-factor experiments.The laws of action of the influencing factors affecting the BBP removal rate and the interaction between different factors were investigated by response surface analysis.The anti-interference performance of the composite was tested by changing the ions in the system,and it was found that sulfate ions promoted the degradation while other ions appeared to be inhibited to a certain extent,but the overall performance showed better anti-interference performance.The composite was recycled to observe the change of degradation efficiency and the XRD and SEM states before and after use,which confirmed the excellent cyclic stability of Bi/Bi2O2CO3/Bi2S3.(3)The mechanism of photocatalytic degradation of BBP by composite materials was analyzed.The energy band structure of Bi/Bi2O2CO3/Bi2S3 was clarified by characterization analysis,and the types of radicals in the photocatalytic process were explored by electron paramagnetic resonance(EPR)and radical trapping experiments,and it was found that hydroxyl radicals,superoxide radicals,singlet state oxygen and photogenerated holes all made different contributions to photocatalysis.A possible S-scheme heterojunction model was proposed to elaborate the degradation mechanism of photocatalysts and clarify the role of free radicals in the photocatalytic process.Combining liquid chromatography-mass spectrometry technique and Fukui function theory calculations,a possible BBP degradation route is proposed,where the fatty chain starts to break under the attack of free radicals and finally generates phthalic acid and benzoic acid,which are then decomposed into small molecules of acids and alcohols and finally mineralized. |
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