Study On Modifying Polymerized Ferric Sulphate With Fly Ash

Coagulation is widely used for wastewater treatment.Coagulant is the key to the efficient of coagulation,and environment scientists have seeked for efficient and low-cost coagulants. Fly ash is a kind of solid waste from thermal power plant(burning coal) which contain metal oxide and silicon.The storage of fly ash directly needs large areas of lands,and it leads to environmental pollution.So the study of utilizing fly ash is hot these years.In this paper,the preservation time of coagulant of polymerized ferric sulphate(PFS) is very short,and PFS is not very ideal to treat the wastewater.So we want to utilize the metal ions and silicon of fly ash to modify PFS.Three parts are carded out three parts in this paper. In the first part,fly ash is dipped in hydrochloric acid solution(HC1),then the mixture is centrifugalized by centrifuge.The supernatant solution is acid dipping solution.Then acid dipping solution which solubilized fly ash by hydrochloric acid was investigated for modifying PFS to prepare a composite coagulant F-PFS.The F-PFS was attained at the condition of ratio of acid dipping solution to PFS of Fe³⁺:1.934 mol·L^-1:0.001 mol·L^-1,mixing speed of 400 r·min^-1.In the second part fly ash was dipped in NaOH solution,then the centrifugal extraction of sodium hydroxide impregnating solution is for preparing of FF-PFS. Then the solution which were rich in silicon were used to compound polymeric ferric sulfate (PFS) and got compounded polymerized ferric sulphate(FF-PFS),The best ratio of dissolved silicon was attained at the condition of 4 mol·L^-1NaOH solution,120℃for 4 hour. The coagulant FF-PFS was attained at the condition of Fe³⁺/Si molar ratio of 1:0.2 and slaking time of 2 h.The third part is that fly ash which is dipped in HC1 and NaOH solution is used to be a kind of sorbent to treat with PNP(100 mg·L^-1).The experiment of fly ash dipped in HCI(A ash) is 30℃,10 g of A ash,the mixing speed of 30 r·min^-1,the mixing time of 24 h; The experiment of fly ash dipped in NaOH(B ash) is 30℃,8 g of A ash,the mixing speed of 30 r·min^-1,the mixing time of 24 h;We use F-PFS and FF-PFS to treat with domestic wastewater,removal efficiencies of COD and turbidity by F-PFS reached 84.99%and 89.7%respectively and removal efficiencies of COD and turbidity reached 93.3%and 96.07%.In this paper,F-PFS and FF-PFS are prepared under normal temperature,using PFS and fly ash.This raw materials cheap and easy to get,lower cost and green environment protection.