Study On New Technology And Fundamental Theory Of Polyferric Sulfate And Phosphorous Polyferric Sulfate Prepared From Pyrite Cinders

Pyrite cinders are the solid waste of sulfuric acid industry. The comprehensive utilization of pyrite cinders is very important because the comprehensive utilization can not only control the cinders pollution, but also recover the resource. Ferrous sulfate, polyferric sulfate and phosphoric polyferric sulfate have been prepared from pyrite cinders.The maturation method has been adopted to treat the cinders in order to raise the recovery rate of iron. The rate of iron recovery is up to 91% by means of maturating the cinders. The suitable factors of maturation are as follows, that maturation temperature is 200-300 C , maturation time is l~2h, H2SO4 concentration is 65-85% and cost coefficient of H2SO4 is 1-1.2.The recovery rate of iron is also up to 90% by leaching cinders with sulfuric acid .There are suitable factors of leaching that reaction temperature is 95-115 C, reaction time is 3~4h, H2SO4 concentration is 40-50% and cost coefficient of H2SO4 is 0.9-1.1. The leaching technology is simpler than the maturation technology.XRD proves first time that FeH(SO4) 4H2O is produced after mixing cinders with H2SO4 and maturating the mixture of cinders and H2SO4. SEM demonstrats that the globular cinders become crystal grains after maturation. Fe3O4 is more reactive than Fe2O3 when cinders react with H2SO4. The reaction between Fe2O3 and H2SO4 is controlled by diffusion and the reaction is applicable to the shrinking core model. Theleaching kinetics equation was 1-(1-xB)2/3 =kt. k = 8.33x104e-6.936/RT. the activeenergy Eo is 6.936kJ/mol.Fe3+ is completely reduced to Fe2+ after putting iron sheet into the leaching liquid and reacting for 4h When reaction temperature is above 50C and Fe3+ concentration is below 2mol/L. FeSO4 7H2O is crystallized from Fe2+ solution by cooling at 9C-17C. PFS solution has been prepared first by dispersing Fe (OH) 3 colloid in the leaching liquid or by oxidizing FeSO4 in the leaching liquid with NaClO3. Phosphoric polyferric sulfate has been obtained by putting Na3pO4 in the PFS solution. Solid PFS has been produced by drying and stirring at 60~80C for 7h after concentrating PFS solution. Solid PPFS has been also prepared in this way.TG-DTA tests show there are tow TG weight loss peaks and tow DTA exothermic peaks in the TG-DTA curves. The temperature ranges of the peaks are respectively 27-160C and 170~290C. Fe4.67(SO4)6(OH)2 20H2O in the solid PFS and PPFS has been discovered by XRD tests. Fe4.67(SO4)6(OH)2 2OH2O disappears after heating above 130C. The first loss weight occurs and the second loss weight is resulted because of losing free water by heating and losing crystal water and Fe4.67(SO4)6(OH)2 2OH2O decommission .FTIR spectroscopy shows that absorption bands at 3400cm-1 and 1635 cm-1 arise from OH and absorption bands at 998cm-1 came from Fe-OH in the solid PFS and PPFS.PFS and PPFS react with HCl rapidly and pH value of the solution is not dependent on the time. The species percentage of Fe(a), Fe(b) and Fe(c) of the same PFS andPPFS are up in order. The percentages Fe(b) and Fe(c) increase and The percentage of Fe(a) decreases as alkali degree and the mole ratio of P and Fe increase. The ratios of Fe(b) and Fe(c) increase from solid PFS, liquid PPFS to liquid PFS. The highest Fe(a) ratios of solid PFS, liquid PPFS and liquid PFS are 56.76%,76.99% and 79.57%.The highest Fe(b) ratios of them are 27.81%,21.82% and 18.71%,.The highest Fe(c) ratios of them are 21.71%,13.76% and 13.77% respectively. Charge neutralization effects increase in the same order as solid PFS, liquid PPFS and liquid PFS. When solid PFS, liquid PPFS and liquid PFS flocculate dialomile suspensions and municipal wastewater the ranges of zeta potentials are from -60mV to +30mV and from -30mV to +12mV respectively.The effects of COD and turbidity removal are such as the order of charge neutralization and the species ratios. These coagulants have highest rates of COD and turbidity removal when alkali degree of solid PFS is 14.40%, alkali degree and mole ratio P/Fe of liquid PPFS are 9.33%...