Preparation And Cr(Ⅵ) Removal Performance Of Functionalization Cellulose Adsorption Materials

The treatment of water ecological environment is the emphasis of the China 14 th Five-Year Plan,in which heavy metal ions have been listed as one of the major indicators of water purification due to the harm to biology and bioaccumulation.There are many methods to purify the heavy metal ions in water,among which adsorption method is widely concerned because of its easy process,high removal rate and small cost.However,activated carbon materials commonly used in the adsorption method not only consume a lot of energy in the preparation process,but also are not easy to recover.Therefore,the development of adsorbents with simple technology,high adsorption efficiency and wide source is the major in the adsorbent research of heavy metal ion.In this paper,using cotton pulp and carboxymethyl cellulose as raw materials,functionalized cellulose-based adsorption materials PEI-PAM-CF and functionalized carboxymethyl cellulose adsorption materials PEI-PAM-CMC were fabricated respectively.The materials were characterized by scanning electron microscopy(SEM)and Fourier transform infrared spectroscopy(FTIR).The effects of p H,adsorbent action time,solution temperature,adsorbent dosage and initial hexavalent chromium concentration on the removal rate were systematically investigated.The macro adsorption mechanism was explored by adsorption kinetics,adsorption thermodynamics and adsorption isotherm model,and its practical performance was studied by recycling performance and adsorption anti-interference performance.The possible adsorption sites and the micro adsorption mechanism are discussed by the calculation based on the quantum chemical.(1)Preparation and Cr(Ⅵ)removal performance of functionalized cellulose based adsorption materials PEI-PAM-CF.Using PEI and PAM as cellulose modifier and ECH as crosslinking agent,functionalized cellulose-based adsorption material PEI-PAM CF was successfully prepared.The characterization results showed that PEI and PAM were successfully introduced into the structure of the material.The adsorption of low concentration Cr(Ⅵ)by PEI-PAM-CF was greatly affected by p H value,and the removal rate reached the highest when p H value of the solution was 3.The removal rate decreased with the increase of temperature and initial concentration,and increased with the increase of PEI-PAM-CF dosage and adsorption time of Cr(Ⅵ)on PEI-PAM-CF.When the PEI-PAM-CF dosage was 0.05 g and adsorption time was 20 min,the adsorption effect was better.The adsorption process was spontaneous and conformed to the pseudo-first-order kinetics and Langmuir adsorption isotherm model.(2)Preparation and Cr(Ⅵ)removal performance of functionalized carboxymethyl cellulose adsorption materials PEI-PAM-CMC.PEI and PAM as modifiers were introduced into the framework of carboxymethyl cellulose relying on the bridging effect of ECH,and functional cellulose-based adsorption material PEI-PAM-CF was successfully prepared.The characterization results showed that PEI and PAM were successfully introduced into the structure of the material.The adsorption of Cr(Ⅵ)by PEI-PAM-CMC was affected by the protonation degree of materials.The higher the protonation degree of materials,the better the adsorption effect.When PEI-PAM-CMC was protonated in HCl with p H= 2,the removal rate of Cr(Ⅵ)was the highest.With the increase of temperature,the removal rate of Cr(Ⅵ)on PEI-PAM CMC decreased.With the increase of adsorption time of Cr(Ⅵ)on PEI-PAM-CF and the dosage of PEI-PAM-CMC,the removal rate increased.The adsorption capacity increased with the increase of initial Cr(Ⅵ)concentration.The adsorption process was spontaneous and conforms to the pseudo-second-order kinetic model and the Freundlich adsorption isotherm model.(3)Quantum chemistry calculation is used to analyze the micro adsorption mechanism.The weak interaction forces between hexavalent chromium with cellulose(CS),CMC and PEI were analyzed by method of Symmetry-Adapted Perturbation Theory and the physical adsorption sites of Cr(Ⅵ)on PEI-PAM-CF were studied by using the electrostatic potential(ESP),and the chemical adsorption sites of Cr(Ⅵ)on PEI-PAM-CMC were studied by using the average local ionization energy(ALIE)and orbital weighted dual descriptor(OW＿DD).The results showed that the addition of PEI played an important role in the two adsorbents.In PEI-PAM-CF system,the addition of PEI provided a large number of electrostatic adsorption sites.In PEI-PAM-CMC system,amino groups in PEI were the main chemical adsorption sites...