Micro-regulation For Novel Silver (Bismuth)-Based Nanomaterials In Environmental Applications And Their Structure-function Relationship

In this study,three typical novel silver?bismuth?-based nanomaterials,such as AgVO₃,BiVO₄ and AgBr,were selected and applied to environmental water pollution control field through the appropriate micro-control means.The application of the modified nanomaterials was evaluated by nano-photocatalysis and nano-adsorption in water pollution treatment.First,single crystalline,non-toxicity,and long-term stability graphene quantum dots?GQDs?were modified onto the AgVO₃ nanoribbons by a facile hydrothermal and sintering technique which constructs a unique heterojunction photocatalyst.Characterization results indicate that GQDs are well dispersed on the surface of AgVO₃ nanoribbons and GQD/AgVO₃ heterojunctions are formed,which can greatly promote the separation efficiency of photogenerated electron-hole pairs under visible light irradiation.By taking advantage of this feature,the GQD/AgVO₃ heterojunctions exhibit considerable improvement on the photocatalytic activities for the degradation of ibuprofen?IBP?under visible light irradiation as compared to pure AgVO₃.The photocatalytic activity of GQD/AgVO₃ heterojunctions is relevant with GQD ratio and the optimal activity is obtained at 3 wt%with the highest separation efficiency of photogenerated electron-hole pairs.Integrating the physicochemical and photocatalytic properties,the factor scontrolling the photocatalytic activity of GQD/AgVO₃ heterojunctions are discussed in detail.Moreover,potential photocatalytic degradation mechanisms of IBP via GQD/AgVO₃ heterojunctions under visiblelight are proposed.Our present work provides a new insight on developing GQD basedheterojunction photocatalysts with effective charge separation forthe efficient photodegradation of organic pollutants from wastewater.On the basis of the successful synthesis of GQDs/AgVO₃ heterojunction photocatalyst,solar-driven GQDs loaded BiVO₄ heterostructure catalysts were fabricated and employed to degradate carbamazepine?CBZ?under simulated solar light.The as-prepared ternary catalysts?GQD/m-BiVO₄/t-BiVO₄?were thoroughly characterized by TEM,HRTEM,XRD,XPS,UV-vis,Raman and PL.The characterization results demonstrated that GQDs are well-dispersed on binary BiVO₄support,and the optical properties of the composites are improved with GQDs loaded.The photocatalytic activities of the novel composite catalysts were significantly increased by incorporation of GQDs on original BiVO₄ semiconductor.In particular,the 1.0 wt%GQD loaded catalysts exhibited the highest photocatalytic activity for CBZ,and the mineralization degree of CBZ with the catalysts could achieve more than 95%.In addition,the transformation products?TPs?of CBZ during the catalysis processes were tentatively identified,and hydroxyl radicals were regarded as the predominant active species.From the results of density functional theory?DFT?calculations and evolution of TPs,hydroxylation and cleavage of amide group on the heterocycle may be the main initial photocatalytic degradation channels for CBZ under the catalysis of GQD/BiVO₄.Finally,in order to investigate the adsorption properties of AgBr-based nanomaterials,a novel adsorbent of AgBr-AgBr/CTAB nanomaterials,which was synthesized via Tollen's reagent with the aid of hexadecyltrimethy ammonium bromide?CTAB?,showed an excellent high affinity to anions and was used for removal of organic dyes in aqueous solutions.The synthesized AgBr-AgBr/CTAB was thoroughly characterized by XRD,SEM,TEM,XPS,FTIR,TGA,DLS as well as zeta potential measurements.The adsorption property and capacity of AgBr-AgBr/CTAB for organic dyes were evaluated using methylene blue?MB?,rhodamine B?RhB?,acid red 18?AR-18?,orange G?OG?,indigo carmine?IC?,and methyl orange?MO?as models.The adsorption capacity of AgBr-AgBr/CTAB complex toward four anionic dyes OG,AR-18,IC,and MO solutions was 87.43±2.03 mg g^-1,205.89±2.12 mg g^-1,140.42±2.13 mg g^-1,and 104.6±1.59 mg g^-1,respectively.On the other hand,this adsorbent exhibited little adsorption ability toward two cationic dyes,MB(2.99±0.40 mg g^-1)and RhB(2.96±0.60 mg g^-1).Interestingly,AgBr-AgBr/CTAB could be applied to efficiently adsorb anionic dyes from binary cationic-anionic dye systems with a high separation factor,and such adsorbent could be reused at least 5 times with adsorption capacities above 95%.The removal of anionic dyes followed pseudo-first-order kinetics and Langmuir isotherm model,indicating that anionic dyes were monolayerly adsorbed on our as-prepared materials.To further elucidate the adsorption mechanism,the theoretical calculation based on first-principles was also provided.The results suggested R-SO^3-groups were the active sites and electrostatic attraction was the dominating contribution for the adsorption of anionic dyes.From the view of environmental impact,AgBr-AgBr/CTAB could be used for the removal of anionic dyes in wastewater under convenient condition,as well as preconcentration of anionic dyes in dye recovery procedure and environmental remediation.More importantly,materials constructed with nanoparticle cores and surfactant cover may provide a new way to environmental applications.