| Glyphosate?N-phosphonomethyl-glycine?will continue to play a critical role in ensuring the growth of crop yields by allowing weed control in the foreseeable future.The extensive use of glyphosate in agriculture may pose a threat to human health.In addition,the photocatalytic method has emerged as the one of the most promising technologies due to its low cost,environmental friendliness and operational simplicity.g-C3N4 has been widely regarded as a promising visible-light-responsive photocatalyst,owing to its moderate band gap??2.7 eV?,high physicochemical stability and facile synthesis.Nevertheless,the g-C3N4 based photocatalysis technology presents significant challenges related to insufficient visible light absorption,low surface area and fast recombination of electron-hole pairs.To resolve these problems,we use MoS2 to composite with g-C3N4 since the MoS2 has the potential to adsorb the near infrared light.However,the prepared MoS2/g-C3N4 existed few active sites.Thence the work is related to use cyclodextrin?CD?modified MoS2/g-C3N4 to improve the removal efficiency of glyphosate.Firstly,we constructed an interlayer composite photocatalyst with?-cyclodextrin??-CD?doping-C3N4?O-C3N4?and molybdenum disulfide?MoS2?was successfully constructed for highly photodegradation of glyphosate in this study.And this overcome the issues of lower light adsorbtion edge and prohibit the recombination of the photo-induced electron and hole pairs.The structure and morphology,optical property,photoelectrochemical properties of the prepared photocatalysts were characterized via a series of characterization techniques.And the average fluorescence lifetime of the composite photocatalysts was extended from 6.67 ns to 7.30 ns compared with pristine g-C3N4,indicating the composite photocatalyst enhanced the adsorption of visible light as well as prohibited the recombination of electron and hole pairs.The mass ratio of MoS2 accounted for O-C3N4/MoS2-5 reached the most efficient removal rate under simulated sunlight irradiation,which was almost 2 times higher than pure g-C3N4.Relative species scavenging experiments revealed·O2-was the main species during the processes of photodegradation.Besides,the toxicity test indicated that the glyphosate become lower toxic or nontoxic after photodegradation.Secondly,CDs can form host-guest complexes with lipophilic molecules by their hydrophobic toroidal cavity,and we use?-CD grafted on the surface of the g-C3N4 and MoS2 to maintain the cavacity of?-CD and remove the glyphosate.Meanwhile,to explore the most efficient composite methods,different kinds of compositing order of?-CD,g-C3N4 and MoS2 were used and the prepared materials were noted as MoS2/?-CD/g-C3N4,?-CD/MoS2/g-C3N4 and g-C3N4/?-CD/MoS2.Besides,XRD,TFIR,SEM,UV-Vis,PL were utilized to characterize the prepared photocatalysts.As a result,MoS2 composited with g-C3N4 and then using?-CD grafted on the surface of MoS2/g-C3N4 has the highest removal efficiency for glyphosate alothough MoS2/?-CD/g-C3N4 and g-C3N4/?-CD/MoS2 has a wider light adsorption edge,which was due to the?-CD can hinder the transfer of photo-induced electrons between g-C3N4 and MoS2.Thirdly,a novel material of cyclodextrin?CDs?grafted on MoS2 nanoflowers/alkalinized g-C3N4nanosheet?MoS2/g-C3N4?was constructed via KH560 as a crosslinking agent.And we explored the difference of?-CD,?-CD and?-CD grafted on the surface of MoS2/g-C3N4 for analyzing the role of CDs.and they overcome the issues of fewer active sites and achieve high-performance of the photocatalyst.As a result,all kinds of CD grafted on MoS2/g-C3N4 all showed a higher removal efficiency of glyphosate and Cr?VI?than that of MoS2/g-C3N4.Simultaneously,?-CD grafted on the surface of MoS2/g-C3N4??-CD/MoS2/g-C3N4?has the highest graft amount and possessed the most efficient removal for glyphosate and Cr?VI?reduction although the light adsorption edge become narrower and the specific surface area became smaller compared with MoS2/g-C3N4.Therefore,it may be due to the fact that the?-CD has the highest solubility,the most-OH groups and the largest cavity volume,which can improve the grafting amount and the access to glyphosate and Cr?VI?. |
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