Preparation Of Resin-based Magnetic Activated Carbons And Their Application In The Removal Of Typical Pollutants In Source Water

In recent years,chemical and pharmaceutical industries have been developed rapidly,and large amounts of synthetic organic compounds release into source waters.Many compounds can cause cell toxicity and genetic toxicity,which may do great harm to human health and even induce death.They can not be effectively removed during traditional water treatment processes and additional advanced treatment processes are needed.Adsorption by activated carbon is considered as one of the most efifective techniques in the removal of organic pollutants.However,traditional precursors are limited and expensive,and powdered activated carbon is difficult to separate from water,which limit the application of activated carbon in water treatment.Recently,much research has been focused on the preparation of activated carbons from industrial and agricultural wastes and many of them exhibited high surface areas and good adsorption capacities.Ion exchange resins are typical ion exchangers and are widely used in many fields with great demand.Ion exchange resins can be regenerated but become unusable after several cycles of recycling because of their decreasing efficiency.Thus,tons of waste ion exchange resins are discarded every year all over the world.Waste resins are generally burned off,which cost a lot.Ion exchange resins are rich in carbon and hydrogen,and waste resins can be obtained in low price,which make it possible to use waste resins for the preparation of activated carbons.Recently,many ion exchange resins have been used as precursors for the preparation of activated carbons,however,most of them exhibited low surface areas and poor adsorption capacities.Thus,the objective of the work is to develop high-surface-area magnetic activated carbons from waste polystyrene-based ion exchange resins.The main research contents and conclusions are as follows:(1)A magnetic activated carbon was prepared from waste cation exchange resin by NaOH activation with the addition of Fe3+.The pyrolysis process of resin with the addition of iron was analyzed and the effects of synthesis conditions were investigated.The results showed that the pyrolysis process of resin included dehydration and decompositions of sulfonic acid groups and resin matrix with the release of sulfur dioxide,carbon dioxide and water vapor.Iron addition limited the formation of some micropores or blocked them,inducing an increase in average pore size.Activation temperature had a great impact on the pore size distribution,crystal structure and magnetic property of activated carbon.The magnetic property of activated carbon was related to its crystal structure.(2)A magnetic activated carbon was prepared from waste anion exchange resin by NaOH activation with the addition of Fe(?)oxalate complexes.The pyrolysis process of resin with the addition of iron was analyzed and the effects of synthesis conditions were investigated.The results showed that functional group in resin could significantly affect the synthesis process and physical and chemical properties of activated carbon.Methylamine,dimethylamine,carbon dioxide and water vapor released during the pyrolysis process of resin.Magnetic iron oxide(s)appeared after carbonization.The presence of the small amount of zero-valent iron indicated that some of the iron oxide(s)was/were reduced during the activation process.Iron addition induced a decrease in the surface area of activated carbon.However,the pore size distribution remained unchanged.The changes in activation agent dosage and activation temperature affected the surface area and pore size distribution of activated carbon.(3)Two resin-based magnetic activated carbons were prepared under the optimum conditions,the surface areas of which were higher than 17010 m2/g.Then the carbons were used as adsorbents for the removal of diethyl phthalate and bisphenol A.The results showed that resin-based magnetic activated carbons exhibited good dynamic performances and the processes fitted well with the pseudo-second-order equation.More mesopores favored rapid adsorption of diethyl phthalate and bisphenol A at first stage.The adsorption capacities of diethyl phthalate and bisphenol A onto resin-based carbons were much higher than those of commercial activated carbons and all the adsorption processes were spontaneous and exothermic.The solution pH affected the adsorption of bisphenol A by changing its molecular structure and its effect on the adsorption of diethyl phthalate is not significant.Natural organic matter with smaller size easily accessed to and occupied the active sites on carbon,inducing the decrease in the adsorption performance of activated carbon.Spent activated carbon can be effectively regenerated by NaOH solution.(4)Resin-based magnetic activated carbons were used as adsorbents for the purification of source water.The results showed that DOC and UV254 can be effectively removed by activated carbons.Carbon treatment had no significant effect on the molecular weight distribution.of organic matters.Fluorescent humic acid can be effectively removed by ACS-1.The concentrations of many semi-volatile organic compounds,including metribuzin,diclorvos and 1-ethyl-4-nitrobenzene,decreased.Human hepatocellular carcinoma cell line(HepG2)was chosen as a cell model for the investigation of cell toxicity and oxidative damages and the results showed that all of them decreased.