Application Of Modified Cellulose Based Adsorbents In Water Treatment

With advances in science and technology,global industrialization,agriculture and family activities pose serious threats to the environment and human health.In order to improve the quality of water used for human production and to protect aquatic life,there is an urgent need to develop more cost-effective water treatment models.Among them,adsorption method due to its simple operation,low cost,easy to recover and reuse adsorbents and other advantages have been widely noticed and applied.Based on two adsorbents:cellulose nanocrystalline and cotton fiber,the chemical reactivity of hydroxyl group in cellulose structure is studied by physical and chemical modification.The research work of this paper is mainly divided into the following three parts:(1)Preparation and properties of anionic modified nanocellulose adsorbentThe adsorbent CNC-g-PAA was prepared using bamboo fiber nanocellulose as the substrate and acrylic acid(AA)as the monomer under the initiation of ceric ammonium nitrate(CAN).The chemical structure and morphology of the adsorbent were characterized.The results showed that AA was successfully grafted onto bamboo cellulose nanocrystals with a grafting rate of 16.93%.The rich carboxylic groups improved the adsorption performance of heavy metal ions Pb and Hg through electrostatic or hydrogen bond adsorption,particularly,it exhibits excellent adsorption capacity for Hg ions.As the temperature increases,the adsorption amount of CNC-g-PAA for Hg ions gradually decreases whereas for Pb ions,the adsorption amount increases.The dynamic adsorption process of CNC-g-PAA for Pb and Hg ions is most consistent with the Dose-Response model.(2)Preparation and properties of cationic modified nanocellulose adsorbentBased on the above bamboo fiber nanocrystals,using methacryloxyethyl trimethylammonium chloride(METAC)as a monomer and cerium ammonium nitrate(CAN)as an initiator,quaternary ammonium salt cationic groups were introduced onto the surface of the nanocrystals,and effective adsorption of the dye Congo red(CR)and the antibiotic tetracycline(TC)was achieved.With the increase of p H value,the adsorption capacity of the adsorbent for CR first increased and then decreased,reaching a maximum value at p H=5.The adsorption capacity of the adsorbent for TC also reaches its maximum at p H=5.Langmuir adsorption isotherm model can describe the adsorption of CNC-gPMETAC for the above pollutants,with the maximum adsorption capacity of306.3mg/g and 126.5mg/g,respectively.The dynamic adsorption process of TC and CR by CNC-g-PMETAC is most consistent with Thomas model.(3)Study on Preparation and Adsorption Properties of Modified Cotton FiberCotton fibers have inherent adsorption properties,which can be further enhanced after modification.Mathematical model fitting was performed on adsorption data under different initial concentrations,flow rates,and thicknesses,and it was found that all the data were consistent with Yoon Nelson and Thomas models.According to the results,it was found that a composite membrane with a diameter of 25 mm and a thickness of 0.65 mm could treat wastewater containing Cr.The adsorption kinetics conforms to the pseudo second order kinetic model and Langmuir isotherm model.Temperature rise has a positive impact on the capture of Cr(VI)on the adsorbent.Adjust the p H value to the optimal value of 2,and as the p H value increases,the saturated adsorption decreases sharply,reaching 23.57 mg/g at p H=8.It exhibits strong p H dependence.The composite membrane has a good adsorption capacity for hexavalent chromium Cr ions,and still has a high adsorption capacity after repeated regeneration and adsorption,indicating that this composite material has a certain application potential for adsorption and filtration of heavy metal ions Cr.