Migration rule of polyacrylamide residue in mine water treatment

Polyacrylamide (PAM) is widely used as a high-efficiency flocculant in the process of mine water treatment.Acrylamide (AM) monomer exists as a residue of PAM in the mine water treatment process,and AM has been listed as ⅡA carcinogen by the National Cancer Center.In order to reveal the migration rule of PAM residue AM in mine water treatment,mine water treatment units in 10 mines are tested and analyzed,and the impacts of PAM dosage,molecular weight,degree of hydrolysis,pH value and salt content of mine water on AM content and treatment effect were studied through coagulation sedimentation and filtration experiments.The results show that in the mine water treatment of 10 mining areas investigated,80% of the clarifier (sedimentation) effluent AM content is more than 0000 5 mg/L,between 0.001 7 mg/L and 0.087 5 mg/L,and 60% of the filtered effluent AM content is more than 0.000 5 mg/L,between 0.001 1 mg/L and 0.076 7 mg/L,the removal rate of AM in the filtration process is 12.3%-99.1%.It is difficult to ensure that the content of AM in the mine water can meet the drinking water standard in the conventional treatment.The optimization of PAM type selection and dosage should be considered in the reuse of drinking water,or membrane technology such as reverse osmosis should be used.Under the experimental conditions (PAM dosage:0.5-2.5 mg/L,PAM molecular weight:5 million-18 million,PAM hydrolysis degree:5%-30%,poly aluminum chloride dosage:80 mg/L),the content of AM first decreased and then increased with an increasing level of various factors in both precipitation and filtration units.The removal rate of AM is 30.0%-58.3% in filtration unit.When PAM dosage is 1.0 mg/L,molecular weight is 12 million,hydrolysis degree is 22%,pH value of raw water is 7,conductivity is 2 000 μS/cm,AM content of precipitated and filtered water is the lowest,the lowest values in the experiment are 0.002 6 and 0.001 2 mg/L respectively.