Research On The Process Of Solution Flocculation-particle Adsorption-membrane Filtration To Remove Anion And Cation Dyes In Water

Most organic dyes are teratogenic,carcinogenic and mutagenic to human health and aquatic life due to the presence of aromatic rings in their structure.Therefore,it is extremely important for environImental safety and clear production to remove of various dyes from industrial dye wastewater before discharging into natural water.Flocculation and adsorption have been considered to be the most effective method for removing dye from wastewater because of its low cost,simple operation and remarkable effect.Chitosan(CS)has been widely studied because of its low price,abundant source,and a large number of active functional groups such as amino and hydroxyl groups.So far,here are various forms for CS,such as CS powder,CS sponge,CS microsphere,CS membranes and other CS-based hybrid materials for flocculation/adsorption removal of dyes.CS in these forms of have the disadvantage of low group utilization and difficulty in regeneration during use.In this study,considering the good compatibility of C.S solution with dye solution,CS solution was used to flocculate the anionic dye directly to make full use of the active groups on the CS molecular chain.The CS-dye particles formed under specific conditions were directly used for the re-adsorption of cationic dyes to reduce the regeneration process,process pollution and improve process efficiency.In addition,the separation of the dye solution after flocculated/adsorbed by membrane filtration was investigated.Specific research work includes the following:In the first part,the flocculation separation of anionic dye Congo red(CR)by CS solution and the formation conditions of CS-CR particles were studied.The effects of the amount of CS solution,time and initial dye concentration oin dye removal efficiency were investigated.The results suggested that the processes were fast and efficient.The removal rate of CR was up to 99.90%with an adsorption capacity of 14971.70 mg·g-1 within 1 min at 30 mL dye solution of 500 mg·L-1 and 0.1 g 1 wt%CS solution.Further,CS-CR particles with a large amount of negative charge on the surface were formed under these conditions and formed gel-like substance under other conditions.Ultrahigh adsorption capacity reached 44956.20 mg·g-1 when the initial concentration was 2000 mg·L-1,which is much higher than other values reported to date.In the second part,the adsorption and separation of cationic dyes methylene blue(MB)and rhodamine B(RhB)by CS-CR particles were studied.The effects of CS-CR particle dosage,contact time and initial dye concentration on dye removal were investigated.The results show that the maximum adsorption capacity of 1457.10 mg·g-1 for MB and 990.00 mg·g-1 for RhB were achieved,which were superior to other CS-based adsorbent.The adsorption process can be better described by the Langmuir model and the pseudo-second order kinetic model.In the third part,the separation of dye solution after solution flocculation or particle adsorption treatment by membrane filtration was studied.The results show that membrane filtration was effective for the separation of the flocculated/adsorbed dye solution.The CS-CR particle filter cake layer formed during the membrane separation process can be further used to separate CR and MB in the solution,the removal rates are respectively 69.87%and 82.14%,thereby realizing the reuse of the filter cake layer.