Research On Resource Utilization Of Metal Ion From Spent Steel Pickling Wastewater

Stainless steel pickling wastewater usually consists of high concentration of nitric acid,hydrofluoric acid,and many other metal ions,such as Fe3+,Cr3+,Ni2+.A large amount of metal crystal salts were produced after recycling nitric acid and hydrofluoric acid from stainless steel pickling wastewater with the method of vacuum evaporation.In this paper,the heavy mental ions were recycled from pickling waste water of the heavy metal salt pulp process with fractional precipitation method,and Ni-Zn ferrites synthetized by metal precipitation can be used as raw materials.The crystal growth kinetics in Ni-Zn ferrite sintering process,and the effects of temperature and sintering time on the soft magnetic properties of Ni-Zn ferrites were investigated in this work.The conclusions were as follow:(1)Ferric ions were recycled with sodium jarosite method,Cr3+ and Ni2+ were recycled with neutralization precipitation method.Results showed that [Fe3+] could be reduced from 30 g/L to 1.59 g/L in the mother liquor,and the loss of Cr3+ and Ni2+ were 27.14 % and 13.72 %,respectively,when the reaction temperature was 90℃,the initial value of pH was 1.5,the amount of seed was 10 g/L and the reaction time was 3.5 h.Cr3+ and Ni2+ were recycled with fractional precipitation method,and the recovery rate of Cr3+ and Ni2+ were 72.86 % and 63.38 %,respectively.(2)The pretreatment of dolomine was carried out by calcination and oxidation leaching.Results showed that the crystal structure of jarosite was destroyed when the calcination temperature was at 550℃,and the leaching rate of Cr3+ was more than 99.1 % under the conditions of the temperature of 60℃,solid liquid ratio of 1:3 and reaction time for 60 min.(3)The crystal growth kinetics of Ni-Zn ferrite sintering process was studied according to kuchinsky sintering model.Results show that the decrease of the pore surface energy of the green body in the sintering process is the driving force of the crystal growth.During the grain growth process,the intergranular pores continued to shrink into the grain boundary,the grain boundary was expanding by the driving force,the grain boundary size was larger than the grain diameter,and then the grains merged.(4)The properties of Ni-Zn ferrite were characterized by VSM.Results showed that with the increase of sintering temperature and sintering time,the remanent magnetic induction(Br)and coercivity(Hc)were decreased,and the saturation magnetic induction intensity(Bs)was increased significantly.After the calcination at 1200℃ for 4 h,Bs=87.75 A·m2·kg-1;Br=1.078A·m2·kg-1;Hc=0.595 kA·m-1,while the value of Hc=0.595 kA·m-1was close to high frequency Ni-Zn ferrite named NXO-10 in the market(Hc=0.79 kA·m-1).