Preparration Of Iron-based Coagulant And Application In Wastewater Treatment

With the rapid development of iron and steel,machinery and chemical industry in recent years,the acid is required to acid picking and rust removing to improve the quality of the metal surfaces.However,in the process of acid pickling,a large quantity of acid pickling waste liquid will be produced.The acid pickling waste liquid will not only pollute the environment but also cause a waste of resources available if discharged directly without treatment.So it is particularly important to study the realization of the pickling liquid waste resource utilization.The waste acids produced from the three most representative companies of galvanizing plant,steel cord plant,strip plant,were studied in this paper.The waste acids were numbered consecutively waste acid A,waste acid B,and waste acid C.The composite ferric coagulant prepared directly from the three waste acids were named as type I.The standard ferric chloride coagulant prepared from the waste acids in which the concentration of ferric was adjusted were named as type â…¡.The poly ferric chloride coagulant prepared directly were named as type â…¢.The poly ferric chloride coagulant prepared from the waste acids in which the concentration of ferric was adjusted were named as type â…£.The application test of this coagulant was conducted on the raw water of municipal sewage treatment plant and waster water from the aquatic products processing industry,with the CODcr and TP as the assessment indicators.The best preparation programme of the coagulant was determined according to the test.The application of coagulant in the treatment of the corresponding wastewater was preliminary studied.The results of study are as follows:(1)For the four types of coagulant prepared from waste acid A,when they were used for the raw water of municipal sewage treatment plant:the composite ferric coagulant(A-â… type) in which the ferric chloride content was 22.3% performed best. The standard ferric chloride coagulant(A-â…¡type) in which the ferric chloride content was 38% performed best.The poly ferric chloride coagulant(A-â…¢ type) with basicity of 4.9% performed best.The poly ferric chloride coagulant(A-â…£ type) with basicity of 9.0% performed best.When they were used for the wastewater of the aquatic products processing industry:the composite ferric coagulant(A-â… type) in which the ferric chloride content was 22.3% performed best.The standard ferric chloride coagulant(A-â…¡type) in which the ferric chloride content was 38% performed best. The polyferric chloride coagulant(A-â…¢ type) with basicity of 3.6% performed best. The poly ferric chloride coagulant(A-â…£ type) with basicity of 4.4% performed best.(2)For the four types of coagulant prepared from waste acid B,when they were used for the raw water of municipal sewage treatment plant:the composite ferric coagulant(B-â… type) in which the ferric chloride content was 25.2% performed best. The standard ferric chloride coagulant(B-â…¡type) in which the ferric chloride content was 38% performed best.The poly ferric chloride coagulant(B-â…¢ type) with basicity of 5.6% performed best.The poly ferric chloride coagulant(B-â…£ type) with basicity of 9.3% performed best.When they were used for the wastewater of the aquatic products processing industry:the composite ferric coagulant(B-â… type) in which the ferric chloride content was 27.8% performed best.The standard ferric chloride coagulant(B-â…¡type) in which the ferric chloride content was 38% performed best. The poly ferric chloride coagulant(B-â…¢ type) with basicity of 4.3% performed best. The poly ferric chloride coagulant(B-â…£ type) with basicity of 2.9% performed best.(3)For the three types of coagulant prepared from waste acid C,when they were used for the raw water of municipal sewage treatment plant:the composite ferric coagulant(C-â… type) in which the ferric chloride content was 34.4% performed best. The standard ferric chloride coagulant(C-â…¡type) in which the ferric chloride content was 38% performed best.The poly ferric chloride coagulant(C-â…¢ type) with basicity of 6.6% performed best.When they were used for the wastewater of the aquatic products processing industry:the composite ferric coagulant(C-â… type) in which the ferric chloride content was 32.3% performed best.The standard ferric chloride coagulant(C-â…¡type) in which the ferric chloride content was 38% performed best. The poly ferric chloride coagulant(C-â…¢ type) with basicity of 7.9% performed best.(4) For the four types of coagulant made from waste acid A and B,the poly ferric chloride coagulant(â…£ type) were most suitable for the raw water of the municipal sewage treatment plant and the wastewater of the aquatic products processing industry.The removal rates of CODcr and TP for(A-â…£ type) when it was used for the raw water of municipal sewage treatment plant,respectively were 82.5% and 97.1%.The removal rates CODcr and TP for(A-â…£ type) when it was used for the wastewater of the aquatic products processing industry respectively were 68.2% and 98.7%.The removal rates of CODcr and TP for(B-â…£ type) when it was used for the raw water of municipal sewage treatment plant,respectively were 80.6% and 95.7%. The removal rates CODcr and TP for(B-â…£type) when it was used for the wastewater of the aquatic products processing industry respectively were 66.6% and 97.3%.For the four types of coagulant prepared from waste acid C,the poly ferric chloride coagulant(C-III type) was most suitable for the raw water of the municipal sewage treatment plant.The removal rates of CODcr and TP respectively were 82.7% and 97.3%.The poly ferric chloride coagulant(C-II type) was most suitable for the wastewater of the aquatic products processing industry,The removal rates of CODcr and TP respectively were 69.1% and 98.0%.In conclusion,the iron-based coagulants developed in this study not only make resource reutilization of waste acid,but also exhibit good coagulation effect.They have good application prospects.