Preparation Of Doped Cobalt Ferrite And Study On Advanced Treatment Of Papermaking Wastewater

With the improvement of wastewater discharge standards in the pulp and paper industry,it is difficult to meet the current emission standards(GB3544-2008)by treating pulp and paper wastewater through conventional biochemical techniques.Therefore,it is very necessary to carry out research on the advanced treatment of papermaking wastewater.In this thesis,nano-CoFe2O4 was prepared by sol-gel method,and nano-CoFe2O4 was doped with trace amounts of Al3+?Cu2+ and In3+,respectively.Then,the heterogeneous UV/Fenton system was used to carry out advanced treatment research on papermaking wastewater,which achieved the discharge of papermaking wastewater and provided a new way for the advanced treatment of papermaking wastewater.By using XRD,SEM,VSM and other characterization methods to analyze the influencing factors of the synthesis of nano-CoFe204,the suitable preparation conditions were obtained:When metal ions and citric acid molar ratio of 1:1.2?pH value 2.0,and at 400 ? calcined 3 hours,the synthesized nano-CoFe2O4 had good purity,high crystallinity,particle dispersion,average particle size of 65.8 nm,nanometer level,saturation magnetization of 55.12 emu·g-1,and good magnetic properties.CoFe2-xMxO4(M=A13+,Cu2+ and In3+)ferrite nanocrystals were synthesized under the optimal preparation conditions,and their ability to adsorb dye Congo red(CR)was compared.The particle size of the sample decreased with the increase of the amount of non-magnetic metal ions doping,indicated that the particle size of the nanoparticles was effectively refined.When the doping ion was Al3+ and the doping amount was 0.15,the average particle size of the sample was the smallest,41.97 im,and the specific surface area was 82.47 m2·g-1,which is 69.5%higher than that of the undoped nano-CoFe2O4;it had the largest adsorption capacity of 286.15 mg-g-1,which was 18%higher than that of undoped nano-CoFe2O4;it had obvious advantages over other types of adsorbents,and the initial reaction rate was also increased by 2 times compared with undoped nano-CoFe2O4.The catalytic performance of CoFe1.85Al0.15O4 with the best adsorption energy was studied by using p-chlorophenol as the model pollutant in papermaking wastewater.The results showed that when the pH 2?the amount of hydrogen peroxide was the theoretical amount?the amount of catalyst 0.05 g·L-1,the degradation rate of 100 mL of 100 mg·L-1 p-chlorophenol can reach more than 96%after 90 min treatment,which was fully removed;At the same time,as the initial concentration increased,the degradation rate of p-chlorophenol decreased.The actual papermaking wastewater was treated by self-made CoFe1.85Al0.15O4 catalyst+H2O2+ultraviolet heterogeneous UV/Fenton system.The results showed that the technology had a good removal effect on organic pollutants in papermaking wastewater.When pH=3.0?hydrogen peroxide dosage 0.08 mL(the concentration of H2O2 was 9.79 mol·L-1)and catalyst dosage 0.1 g,100 mL of papermaking wastewater with a CODcr concentration of 122.92 mol·L-1 achieved the best removal effect after 180 min treatment.The CODcr of wastewater reached the national emission standard when the reaction was less than 60 min.After repeated use of the catalyst for 4 times,it still had a certain catalytic activity,and the dissolution rate of the three metal ions in the catalyst was not more than 2%.