The Preparation Of Efficient Magnetic Polymeric Ferric Sulfate With Recycled Fenton Iron Sludge

In this study, the research object is the iron mud generated from the paper mill wastewater treatment by advanced oxidation period of Fenton process. Properties and composition of Fenton iron mud were analysed; recycle the iron by acid leaching process; take the recovered solution for preparation of highly agglutinative polyferric sulfate coagulant; and at the same time, introduce magnetic nano particles, explore the characteristics of polyferric sulfate and magnetic polymerization iron sulfate coagulant products; explore the effect of the products in coagulation experiment, the conclusions are as follows:(1) Recycle the iron from Fenton iron mud by acid leaching with sulfuric acid. The optimum leaching condition is:take 20:1 liquid-solid ratio with 3mol/L sulfuric acid and dry iron mud, stirring for 50 minutes in 60℃ water bath.At this time, the leaching rate of iron reached more than 95%, and remaining stably. There is a positive correlation between the recovery rate of iron sludge and sludge solids reduction rate. The acid leaching recovery is an effective method to reduce the total amount of sludge.(2) Using the recovered Fenton iron mud leaching solution to prepare polymeric ferric sulfate (PFS) by alkaline method. And mix PFS with magnetic nanoparticles, obtain magnetic polymeric ferric sulfate (MPFS) products. The PFS product, the high aggregation state of iron accounted for 23.6%, in which MPFS accounted for 50.3%. In the characteristic functional groups, polymerization crystal structure, surface structure and other indicators, PFS and MPFS have reached the requirements of the commodity polymeric ferric sulfate. At the same time, it is obvious that the integration of magnetic nanoparticles in MPFS makes the products having the characteristics of magnetic, and show a new structure.(3) The PFS and MPFS performance well in the actual coagulation experiment. They can meet the demand for the treatment of the sewage in different environmental conditions, which are even better than the commercial polymeric ferric sulfate. The results show that the best pH value in the coagulation is 6-8, which is excellent in the range of 10～30℃ as well. The PFS and MPFS products reduced the water turbidity and CODCr effectively. The optimal dosage of 150mg/L, 100mg/L, respectively. The best turbidity removal rate reached 98.86% and 98.61%, respectively, and the best CODcr removal rate was 67.35% and 67.11%, respectively. The removal efficiency were better than the commercial polymeric ferric sulfate. MPFS is far better than both PFS and the commercial polymeric ferric sulfate in the settlement velocity and the density of the sludge, the initial settling velocity was increased ten times, as well as the stability time of the flocculation was accelerated from 20min to 4min, which greatly shortened the processing time of coagulation process.