Preparation Of An Inorganic Composite Flocculant And Its Effect On Dye Wastewater Treatment

The problem of water resources was still a major issue in the textile printing and dyeing industry,The improper treatment of dye wastewater would have a very adverse effect on the human body.The flocculation sedimentation was a simple and easy method for physical treatment of dye wastewater,which occupied an important position in dye wastewater treatment.However,in the course of research,it was found that magnesium salt flocculants had a short range of pH,large amounts of sludge and other shortcomings during use.The iron salt and zinc salt flocculants had wider pH application range than the magnesium salt flocculant and denser flocs so it could reduce the sludge volume in the flocculation process.Therefore,iron and zinc ions were introduced on the basis of poly-silicate magnesium in order to made a new type of efficient poly-silicate ferric zinc magnesium flocculant.First of all,the preparation conditions of the poly-silicate ferric zinc magnesium were explored and its structure was characterized.The treatment effect of poly-silicate ferric zinc magnesium flocculant on Congo red dye wastewater and the change of sludge volume during flocculation were also studied and compared with the poly-silicate magnesium.The results showed that in order to make the polysilicic acid solution have a suitable stable existence time,the initial concentration of the SiO2 solution was 0.4 mol/L when the silicic acid solution was prepared at room temperature,and the initial pH value was 5.5,which was a suitable operation.In this case,the stable time for the polysilicic acid was about 8 minutes.The molar ratio of of iron,zinc,magnesium and silicon was 1:4:1:2 and the result was got by orthogonal experiments.The structural characterization of the poly-silicate ferric zinc magnesium and the poly-silicate magnesium were performed.The results showed that poly-silicate ferric zinc magnesium was an amorphous high molecular polymer,and poly-silicate magnesium had crystal structure.The surface of the poly-silicate magnesium had irregular streaks,while the surface of the poly-silicate ferric zinc magnesium had a lot of irregular attachments.This was due to amorphous substances generated by the chelation of silicon and metal ions,which increased the surface area and flocculation ability.The poly-silicate ferric zinc magnesium contains more hydroxyl groups than poly-silicate magnesium,so that The poly-silicate ferric zinc magnesium had better adsorption performance.The decolorization experiments of Congo red by poly-silicate magnesium and poly-silicate ferric zinc magnesium were conducted.Firstly,the applicable pH range of the poly-silicate ferric zinc magnesium was wider,and the decolorization rate was above 90%when the pH changed from 9.0 to 13.0.However,the poly-silicate magnesium had good decolorization effect only when the pH value changed from 12.0 to 13.0.Secondly,the poly-silicate ferric zinc magnesium had better decolorization effect and less volume of sludge,which was closely related to the addition of iron and zinc ions.Therefore,compared with poly-silicate magnesium,the poly-silicate ferric zinc magnesium improved the disadvantage of its narrow pH application and the large volume of the sludge.