The Preparation Of Rare Earth Waste Residue Coagulants And Its Application In The Coking Wastewater

Rare Earth residue can react with sodium hydroxide to prepare the coagulant which can be used for treating the coking wastewater. This paper studied the factors of the coagulant preparation through experiment, and got the parameters of the four main factors; then applied the coagulant to treat coking wastewater. Compared the coagulant with other common coagulant and analyzed the difference between rare earth coagulant and common coagulant.The raw material of the coagulant was the Rare Earth residue which was the rest of the choosing iron and smelting Rare Earth treatment. Put the Rare Earth waste residue and sodium hydroxide into the round-bottom flask, then heated the flask to get the high temperature to react, finally, did a water bath to obtain the coagulant. After the single factor experiment, chose four main factors to do the34orthogonal experiment. Then applied the coagulant to coking wastewater, measured the chroma, turbidity and oxygen demand (CODCr). And then analyzed the result by range method，the sequence of the main effective factor were as follows: water bath temperature＞water bath time＞boiling reaction time＞rare earth residue dosage. The best conditions for prepare the coagulant were as follows: Rare Earth residue dosage was8g, the boiling reaction time was3h, water bath time was3h, water bath temperature was80℃. Coagulation experiment showed that the turbidity removal rate was more than93%, up to98.68%, chroma, oxygen demand (CODCr) removal rate were also good.Then studied the coagulant which was used for coking wastewater from a steel company, and the wastewater was under the biochemical treatment. Studied pH, dosage of coagulant, water conditions and other effective factors. The results showed the optimum conditions of the coagulation reaction: pH5-7, the dosage in3-4ml, water conditions were as follows: stirring1minutes in rapid rate at360r/min, stirring10minutes in medium rate at90r/min, stirring10minutes in slow rate at40r/min, settling time was15min. The results showed that the turbidity removal rate of the coagulant was up to98.63%.Then compared the Rare Earth residue coagulant with poly ferric sulfate (PFS), polyaluminium chloride iron (PFAC), M180and LD101in coagulation experiments. Results showed that the removal rate of polymeric ferric sulfate (PFS) and polyaluminium chloride iron (PFAC) for coking wastewater were not reached90%, M108、LD101had good removal rate of turbidity, LD101was better, removal rate can reach92.43%, the removal rate of Rare Earth residue coagulant for coking wastewater was up to98.63%, the effection of Rare Earth residue coagulant for treating coking wastewater was better than the other four kinds of coagulants.The Rare Earth residue can be used for treating coking wastewater, and the effection of the treatment is good. The chroma, turbidity and oxygen demand (CODCr) were improved significantly. It made full use of the solid waste and reached the goal of combining the industrial production with environmental protection.