Preparation Of High-performance PFS Coagulant From Desulfurization Slags By Catalytic Thermal Activation Of Persulfate

Desulfurization slags?DSS?are the main by-product generated from industrial gas desulphurization process.Although DSS contains rich iron and sulfur resources,it still imposes a serious environment safety problem to industrial production and public health due to the special characteristics of self-heating and even spontaneous combustion as well as release of hydrogen sulfide gas in room temperature.Therefore,it is very important and essential to reasonably handle DSS,especially from both the viewpoints of environmental sustainability and effective resource utilization.Herein,we report the usage of DSS as the raw material to synthesize polymeric ferric sulfate?PFS?coagulant by the catalytic thermal activation of persulfate method.First,FeS in DSS was oxidized into Fe₂?SO₄?₃ by Na₂S₂O₈ under heating.The condition optimization was conducted in the term of different weight ratio of Na₂S₂O₈/DSS,temperature,reaction time and stirring speed.Then,PFS was synthesized through the hydrolytic polymerization of Fe₂?SO₄?₃,and subsequently characterized by SEM,XRD,FTIR and TGA.Finally,the coagulation performance of PFS was evaluated via the treatment of kaolin suspensions.Results showed that:?1?The activation efficiency of Na₂S₂O₈ can be significantly improved by DSS.The activation efficiency of Na₂S₂O₈ can be significantly increased by 5.5 times at 60 0C;?2?The leaching rate of iron is up to 93.48% and no hydrogen sulfide releasing under the condition of m?Na₂S₂O₈/DSS?=1.5,70 0C,433 r/min and 5 h reaction time;?3?By adjusting the initial pH of Fe₂?SO₄?₃ mother liquor,reaction temperature and time,the red brown sticky liquid polymeric ferric sulfate was obtained.The optimal condition to obtain high-performance polymeric ferric sulfate flocculant is the initial pH between 2.0-2.5,reaction temperature of 550 C and 2-3 h of reaction time after hydrolytic polymerization.?4?The as-prepared PFS were used as flocculants to treat kaolin suspensions.About 95.47% of kaolin suspensions were removed on the conditions of dosage of 200 mg/L and pH of 9.0.The PFS has high performance of flocculation within pH range of 9.0-11.0.In brief,the hazardous DSS can be successfully transformed into high-performance PFS coagulant through the catalytic thermal activation of persulfate.