Preparation And Adsorption Performance Of PVA/NFC Porous Gel Spheres

With the development of social industry,heavy metals and organic wastewater have become one of the most harmful water pollution problems.The main causes of water pollution are the arbitrary discharge of industrial wastewater from electric mosaic,papermaking,mining,unreasonable use of agricultural pesticides and domestic sewage.Because of the biological enrichment effect,pollutants can enter the human body through the food chain and enrich,thus damaging human organs and tissues,seriously threatening people’s health and safety.How to develop green bag,economic and efficient methods to control water pollution is the focus of many researchers.In recent years,chemical precipitation,abdominal separation,ion exchange,electrochemical method,biomass method,flocculation method and adsorption method have been reported and applied to water pollution control.The above methods have certain effects on the removal of heavy metal ions and organic wastewater,but they also have many disadvantages,such as high cost,easy to cause secondary pollution,complex preparation methods and processes,poor selectivity and so on.Adsorption method has attracted wide attention due to its advantages of wide material sources,simple process,high removal efficiency,fast speed and good recyclability.NFC was prepared from softwood pulp by carboxylation modification in TEMPO/NaClO/NaBr oxidation system under high pressure homogenization.PVA/NFC porous hydrogel spheres were prepared by crosslinking NFC with PVA using glutaraldehyde as crosslinking agent and suspension spheroidization method.The properties of PVA/NFC porous hydrogel spheres for phenol,aniline and heavy metals were characterized by infrared spectroscopy,scanning electron microscopy,thermogravimetric analysis,moisture content and compression modulus.The adsorption mechanism of PVA/NFC porous hydrogel spheres for heavy metals was studied.The conclusions are as follows:Infrared spectroscopy,scanning electron microscopy and thermogravimetric analysis showed that PVA and NFC crosslinked successfully,and the hydrogel gels showed porous three-dimensional network structure.Langmuir isotherm fits the description of the adsorption process of PVA/NFC composite hydrogel on Cu2+,phenol and aniline adsorbents.It is proved that the adsorption process belongs to monolayer molecular adsorption.The PVA/NFC porous hydrogel spheres with 2%crosslinking degree have the best adsorption effect on Cu2+,phenol and aniline.The maximum adsorption amounts are 2.77 mmol/g,2.94 mmol/g,respectively.The PVA/NFC porous hydrogel spheres with 3%crosslinking degree have the best adsorption effect on aniline.The maximum adsorption amount is 512.01 mg/g.The second-order kinetics equation fitted well with the kinetic fitting results describing the adsorption of Cu2+,phenol and aniline on PVA/NFC composite hydrogels.The best adsorption value of gel beads for Cu2+,phenol and aniline was 6,7 and 4,respectively.The above results show that PVA and NFC have excellent adsorption properties for Cu2+,phenol and aniline on the gel beads prepared by chemical crosslinking,and the preparation process is simple.It not only extends the application scope of nanocellulose derivatives in water treatment industry,but also provides a new idea for the design and preparation of new adsorption materials.