Research On The Preparation And Property Of Coated-stable Potassium Ferrate

Potassium ferrate (K2FeO4) is a very strong oxidant, which has a wide range of applications, especially in the field of wastewater treatment. However it has low effect on dealing with wastewater because of its poor stability, so coating agents were used to improve the stability of potassium ferrate by molten condensation and stirring method in this study. The coated potassium ferrate is treated with water samples taken from Yangtze River, Nanjing, China in order to explore its performance and applications in water treatment.20%(W/W) of purchased potassium ferrate was firstly carried out by recrystallization. The optimum conditions of purification included 5mol/L KOH solution of dissolving solid potassium ferrate,25℃ of recrystallization temperature,20min of recrystallization time, 40ml cyclohexane of washing dosage and 65℃ of drying temperature for one hour. The whole process is done in triplicate to obtain 97.96% potassium ferrate and the product recrystallized was proved to be potassium ferrate by IR, XRD and SEM.Secondly, three different waxes, polyethylene wax (PEW), grain wax and sliced paraffin wax were selected as coating agents. Potassium ferrate was coated by molten condensation and stirring method. By analyzing the coating rate, moisture absorption and release rate, PEW was considered to be better than others and was finally chosen as the coating agent. On the basis of the over research, the factors affecting the stability of PEW-type K2FeO4 and rule of relese in water were futher study. The results showed that the optimum conditions of preparating stable potassium ferrate included 100±1℃ of magnetic stirring temperature,500 r/min of stirring speed,40 min of stirring time, PEW/K2FeO4=8:1, encapsulation ratio could be about 90% on such conditions by orthogonal experiments. According to the analysis of IR, SEM and XRD, the active component of potassium ferrate remained unbroken during the coating process. The release kinetics of K2FeO4 from the PEW-type K.2FeO4 was in good agreement with Q=ktn(R2>0.97) model, the constant k with increasing the ratio of PEW/ K2FeO4 is reduced, so we can change the property of release by adjusting the ratio of PEW/ K2Fe04.Finally:we treated the water of Yangtze River by using 8:1 PEW-type K2FeO4. Different factors that influence removal ratio of turbidity, CODMn and ammonia nitrogen were studied. Our findings concluded that at the dosage of encapsulation-type, K2FeO4=75-125 mg/L (based on the concentration of K2FeO4), pH= 5-9, reaction time of 20 min and stirring speed of 400r/min, the removal ratio of turbidity, CODMn and ammonia nitrogen respectively reached 97.46%、63.69%、36.54% and it was also found that the effect of the removal radio of turbidity, CODMn and ammonia nitrogen was better by combining with PFS.