Preparation Of Cellulose Based Adsorbents And Research On Adsorption Of Cadmium Ions

Industrial development discharges a large amount of waste water,which makes the water pollution in the environment more and more serious,among which the cadmium ions（Cd（II））containing wastewater is a common source of water resource pollution.There were many methods had been used to treat Cd（II）in wastewater,among which the adsorption method process is simple,efficient and energy-saving,and is gradually gaining popularity in the field of heavy metal ion removal.However,the key to the adsorption method of adsorption is the choice of adsorbent.Cellulose is a kind of natural macromolecular compound,and its carbon chain is connected with hydroxyl which could been chemically modified.After chemical modification,it can be grafted to prepare adsorbent.The main component of the treated cassava residue was cellulose,and its could be chemically modified to prepare adsorbents,which can greatly reduce the cost of adsorbents.In this paper,the adsorbent was prepared by modifying sodium carboxymethyl cellulose（CMC）and pretreated cassava residue respectively.The main research contents are as follows:（1）.The cellulose-bentonite composite adsorbent(CMC_CV-Bent)was prepared by aqueous solution polymerization with sodium carboxymethyl cellulose（CMC）and treated bentonite（Bent）as raw materials and acrylic acid（AA）as monomer.The SEM could be showed that the surface of the prepared CMC_CV-Bent was rough and uneven,and there were cellulose banded structures among the lamellae,and the surface of the prepared CMC_CV-Bent showed a network structure after amplification;the XRD results could be shown that that the peak value moves to low diffraction angle before and after modification,which indicates that the spacings between bentonite layers ware exfoliated;the FITR shown that the characteristic peaks of CMC,and the internal vibration absorption peaks of silicon oxygen tetrahedron and aluminum oxygen octahedron of Bent appeared in the CMC_CV-Bent adsorbent,indicating that there was a cross-linking between CMC and Bent.The addition amount of CMC is an important factor affecting the adsorption of Cd（II）by CMC_CV-Bent.When the addition amount of CMC is 2 wt%,the adsorbent has the best adsorption effect on Cd（II）,and compared with the adsorbent without CMC,the adsorption capacity for Cd（II）is 17.96 mg·g^-1 increased to 33.58 mg·g^-1.（2）.The cellulose-bentonite composite adsorbent(CMC_MW-Bent)was prepared by microwave-assisted synthesis with sodium carboxymethyl cellulose（CMC）and treated bentonite（Bent）as raw materials and acrylic acid（AA）as monomer.The SEM shown that the surface of CMC_MW-Bent is relatively smooth,and there was unreacted cellulose structure between the lamellae,and the surface of the observation under high magnification shown a neat structure like bamboo shoots;the XRD results could be shown that the CMC_MW-Bent interlamellar spacing changes,and CMC enters into bent interlamellar;the TGA results showed that CMC_MW-Bent showed better thermal stability than CMC and Bent.The p H exhibited one of the main factors affecting the adsorption effect of the adsorbent,that the adsorption effect is the best in p H6-7.Compared with CMC_CV-Bent and CMC_MW-Bent,the adsorption capacity of Cd（II）was increased from 32.65 mg?g^-1to 44.76 mg?g^-1.The adsorption of Cd（II）by CMC_MW-Bent fits Langmuir isotherm model and pseudo-second-order kinetic model,which indicates that the adsorption of Cd（II）by CMC_MW-Bent is a monolayer chemisorption process,and the thermodynamic research has shown that the adsorption process belongs to spontaneous heat absorption process.（3）.This PEI/HMPCR adsorbent was prepared by using the local wastecassava residue from Guangxi was used as raw material,PEG2000 as porogen and insoluble linear PEI modified PCR,and used for the adsorption of Cd（II）in wastewater.The N₂ adsorption desorption analysis showed that the specific surface area increased from 8.08 m2·g^-1 to 17.06 m2·g^-1,that the Cd（II）adsorption increased from 29.62 mg·g^-1 to 36.41 mg·g^-1,when compared with cassava residue without porogenic agent,after the PEI was added,the specific surface area decreased and the pore size was 14.24 nm,indicating that PEI was a mesoporous adsorbent;the XPS results showed that the adsorption process mainly occurred on the-NH and-NH₂ groups on the surface;the SEM results showed that the size of the microspheres was dispersed and the particle size was uniform;the VSM results show that the saturation magnetization of 9.5 emu·g^-1 exhibited super paramagnetism,and it could be adsorbed by an external magnetic field after adsorption of Cd（II）of the PEI/HMPCR rapid magnetic separation.The experiment investigated the influence of the p H of the solution,the amount of PEI,and the amounts of porogen（PEG2000）on the adsorption process of Cd（II）,and the results showed that the maximum adsorption capacity of PEI/HMPCR for Cd（II）was 143.6 mg?g^-1 when the p H=6,amounts of PEG2000 was 20.0 wt%,amounts of PEI was 5.0 wt%.Fitting the adsorption model proves that the fitted adsorption curve of PEI/HMPCR conform to Langmuir isothermal adsorption model and pseudo-second-order kinetic model,indicated that the adsorption process of PEI/HMPCR for Cd（II）in water was mainly controlled by both chemical adsorption and diffusion processes;PEI/HMPCR still had the initial 77.6%effect after five adsorption desorption cycles,indicating that PEI/HMPCR exhibited good recycling performance.