Fabrication Of Nano MOFs/Chitosan Composites With Different Morphology And Their Application In Water Treatment

In this paper,three new adsorbents were designed and prepared,which were used for the adsorption of organic pollutants in water such as dyes,preservative precursors and hydrolysates.The adsorption kinetics,thermodynamics,isothermal model,and adsorption mechanism were studied.This paper mainly includes the following parts.The large specific surface area,high porosity metal organic framework material(ZIF-8)dotted biodegradable chitosan(CS)bulk hybrid material(ZIF-8@CSK)were fabricated via in-situ growth method.The prepared ZIF-8@CSK block composite was used to remove Congo red(CR)dye from wastewater.The adsorption kinetics,isothermal model and adsorption mechanism were studied.The experimental results showed that nano-ZIF-8particles with hexagonal and cubic shapes were loaded on the surface of CS block,and the distribution was dense and uniform.The content of ZIF-8 accounted for about 21.3 wt%.The removal rate of CR by ZIF-8@CSK reached 100%.The adsorption process was a single-layer adsorption and the adsorption was an exothermic process.The adsorption rate was mainly controlled by the chemical adsorption mechanism,and its maximum adsorption capacity was922 mg/g.Even after 5 cycles,the adsorption capacity of ZIF-8@CSK for CR was still higher than 90%.FeMIL101 was prepared from terephthalic acid and ferric chloride hexahydrate.FeMIL101/CS composite sponge was prepared by freeze-drying,and it was used to remove anionic dyes from wastewater.The kinetics,isothermal model and adsorption mechanism of acid red 94(AR)adsorption were studied.Experiments showed that the sponge has the porous structure with a pore size of several tens of microns.Nano-FeMIL101 particles were supported on the surface of the CS sponge or embedded in the sponge.The FeMIL101/CS composite sponge had high adsorption capacity for anionic dye AR,and the maximum adsorption capacity was 4518 mg/g.The removal rate of AR by FeMIL101/CS composite sponge reached 100%.The adsorption process was single-layer adsorption,and the adsorption rate was mainly controlled by the chemical adsorption mechanism.FeMIL101/CS composite sponge can be used as a strainer to remove low concentrations of anionic dyes quickly.Chitosan microspheres(CSM)were prepared by inverse emulsion method,and ZIF-8was loaded on CSM by co-precipitation method to prepare ZIF-8@CSM composite microspheres.The prepared ZIF-8@CSM composite microspheres were used to remove p-hydroxybenzoic acid(the preservative precursor and the hydrolyzed product)in wastewater.The adsorption thermodynamics and isothermal models were investigated.The results showed that the loaded ZIF-8 made the microspheres rough,and the content of ZIF-8 accounted for about 15.3 wt%.The maximum adsorption capacity of ZIF-8@CSM for p-hydroxybenzoic acid reached 176.6 mg/g,and the adsorption process can reach equilibrium in about 30 s,,which can be used as a fast adsorption material.The adsorption was an exothermic process,and the adsorption capacity of ZIF-8@CSM decreased with increasing temperature and was greatly affected by pH.