The Solvothermal Preparation Of ZnO Based Light-regenerative Adsorbents And Study On Their Adsorption Property

Water pollution has been regarded as one of the severest challenges for sustainable development in recent decades.It mainly refers to that the concentration of pollutants in water body exceeds a certain concentration to seriously affect the ecological environment and human health,which mainly includes heavy metals and organic dyes contaminants.Recently,adsorption stands out from various water-treatment techniques in view of its affordable cost,quite ease and high safety.And regeneration of adsorbents post adsorption in water treatment is one of the crucial aspects as it determines the feasibility of the system and controls the economy of the technology.Unfortunately,traditional regeneration methods not only lead to the decrement of adsorption capacity due to surface destruction,but also result in the leaching of the pollutants back into the environment causing secondary pollution.A new type of adsorbents is designed by interweaving inorganic ZnO photocatalysts with long-chain organic adsorbents.In which,the organic adsorbents possess high adsorption capacity for the contaminants,while the photocatalysts can break the long chain of these metastable organic adsorbents under light irradiation after adsorption,and hence desorbing pollutants.This new design of adsorbent will shed new light on the development of next generation of adsorbents in water-treatment field.Our main work is as follows:1.In this work,a facile and versatile urea-assisted solvothermal procedure was employed to synthesize a new type of ZnO/zinc alkoxide light-regenerative adsorbents.The zinc alkoxides?[Zn₂C₄H₈O₄]_n?in our design could effectively modulate the bandgap of ZnO from 3.27 to 2.49 eV,and they could be degraded under ultraviolet irradiation with the help of ZnO photocatalyst.The adsorbent demonstrated remarkable dye adsorption capacity(ca.1850 and 640 mg g^-1 for methyl blue and Congo red dyes,respectively)and high selectivity.Its positive surface charge was condutive to the electrostatic attraction with anionic dyes in aqueous solution.Based on the thermodynamic studies,the dye adsorption mechanism on this adsorbent was mainly taken as a hybrid of physisorption and chemisorption.Moreover,this adsorbent could be effectively regenerated via short-time natural sunlight or ultraviolet light irradiation after dye adsorption.More strikingly,these long-chain zinc alkoxides were of superior adsorption capability with a maximum adsorption capacity of 200.3 mg g^-1 and an initial adsorption rate of 3.6 mg g^-1 min^-1 at 25?,due to their abundant surface groups to induce physisorption as well as chemisorption for Cr?VI?species in waste water.After Cr?VI?adsorption,the as-designed adsorbent could be facilely regenerated with ultraviolet irradiation in warm water.2,ZnO/iron oxides/zinc alkoxides light-regenerative adsorbent with hollow spherical morphology was synthesized via solvothermal methods with no aid of template or surfactant.The growth mechanism was analyzed and described as an agglomerate-buttress fusing pathway.Meanwhile,these hollow iron oxide/ZnO microspheres possessed superparamagnetism and quick magnetic responsivity.Subsequently,they were employed to remove Congo red?CR?from water.On the basis of Brunauer-Emmett-Teller isotherms model,the theoretical CR adsorptin capacity were calculated to be 1475.1 mg g^-1 at 25?.After adsorption,they could be effectively regenerated by ultraviolet-light irradiation.Their gram-grade CR adsorption capacities and excellent recyclability were highly desirable in water treatment.