Design Synthesis Of Zns Nanotube Based Materials And Their Superior Adsorption Performance For Organic Dyes

A major portion of the drinking water sources worldwide are found to be contaminated with various toxins and pathogenic microbes.Therefore,the proper treatment of wastewater prior to its release is very important for protecting our ecosystem.Among various pollutants,organic toxic dyes are presently one of the major contributors to water pollution.Adsorption technique is considered to be a promising and an efficient way to remove organic dyes in water due to flexibility and simplicity of design,and high efficiency.Up to now,as the core of the adsorption technique,various types of absorbents have been prepared toward removal of organic dyes from water.But,no one specific absorbent seems to be able to completely remove all types of dyes at low cost.As a nontoxic and environmentally friendly material,ZnS and its composites have been widely studied in photocatalytic degradation of organic dyes.But,there is little study of ZnS nanomaterial as an adsorbent in removal organic dye.To our best knowledge,there are no reports on the adsorption study of ZnS nanotubes as an adsorbent in removal organic dye.It is generally known that hollow nanotube with a large surface area may provide more active sites to absorb dye molecule,the as-formed ZnS nanotubes are expected to be a promising adsorbent.Actually,all these approaches for the fabrication of ZnS nanotubes required surfactants or specific processes such as high pressure,elevated temperature and so on.This is the main reason that limits ZnS nanotubes’ promising applications in adsorption.Therefore,it is highly desirable to explore a simple and mild route for the synthesis of high quality ZnS nanotubes with high removal efficiency and good selectivity towards certain dyes.Based on the research background,ZnS nanotubes and ZnS nanotubes based materials were designed and fabricated.The main research contents are listed as follow:In chapter 2,ZnS nanotubes are successfully fabricated only using three raw materials(Zn(CH3COO)2,NaHCO3 and Na2S)through a simple two step synthetic route at ambient temperature.It is worth noting that the process is economical and environmentally friendly without need of high pressure or elevated temperature conditions.Furthermore,the as-prepared ZnS nanotubes as an adsorbent are exploited in the adsorption of organic dyes.The adsorption experiments indicate that the resultant products display superior selective adsorption ability for the anionic dyes with amine(-NH2/NH)functional groups through the synergistic effect of hydrogen bonding and electrostatic attraction between the dye molecules and the adsorbent.Taking CR dye as an example,the maximum adsorption capacity for the removal of congo red reaches 724.6 mg g-1 in water,much higher than many composite adsorbents reported in literatures.The present study provided a environmentally friendly adsorbent in organic dye separation technologies or dye removal.Notably,these results also could offer important clues for designing ZnS nanostructures with good selectivity for specific organic dyes by tuning defect-related surface state.In chapter 3,we successfully achieved a new method for preparing ZnS nanotubes/CdS hollow sphere composite inspired by our first work.Zn(CH3COO)2 · 2H20、Na2C03、Na2S·9H2O and Cd(CH3COO)2 ·2H2O were used as raw materials.First,Zn-rod/CdCO3 particles composite precursors were fabricated.Then,the composite precursors were transformed to ZnS nanotubes/CdS hollow sphere composite through a simple precipitation conversion route at ambient temperature without need of high pressure or elevated temperature conditions.The composites were used as adsorbent on removal of organic dyes.The adsorption experiment show that ZnS nanotubes/CdS hollow sphere compositepossess a higher adsorption effiency for the anionic dyes with amine(-NH2/NH)functional groups compared to ZnS nanotubes and CdS hollow sphere.Taking CR dye as an example,the maximum adsorption capacity for the removal of congo red reaches 724.6 mg g-1 in water.Therefore,the present study not only presents a promising strategy for fabrication of hollow composite material but also indicates their great potential application as environmentally friendly adsorbents in organic dye separation technologies or dye removal.