Preparation Of Organomodified Magnetite And Graphene Oxide And Their Removal Performance For Cr（Ⅵ）,Cu（Ⅱ） And Bisphenol A

Heavy metal and organic pollutants in water seriously endanger the ecological environment and human health.Adsorption technique for advanced treatment of such pollutants is simple to operate,low cost and high efficiency,but adsorbents would be saturated.Therefore,the key of adsorption technique is that adsorbents not only can effectively remove pollutants,but also can be easily separated from water,desorbed,regenerated and reused.Magnetite nanoparticles are easy to be separated from water,but their adsorption capacity is limited.Graphene oxide has strong adsorption capacity for heavy metal cations,but it is difficult to be separated from water.The purpose of this paper is to develop nanoadsorbents,which not only can remove heavy metals and bisphenol A effectively,but also can be easily separated from water.Organic compounds were used to modify magnetite nanoparticles and graphene oxide.The two adsorbents prepared in this study are monolayer of silane on magnetite nanoparticles(MSMNPs)and graphene oxide/hexadecyltrimethylammonium Bromide aerogels(GO/HDTMA).The adsorption properties of these two absorbents were studied on the basis of characterization.The results showed that when the equilibrium concentration of silane was below 300 mg/L,the monolayer silane could be loaded on the surface of magnetite nanoparticles(MNPs)in aqueous solution,and the monolayer silane could cover 100% of the surface of MNPs when the temperature was above 90 ℃ or the ionic strength was above 0.1 mol/L Na Cl.TEM confirmed that MSMNPs were existed in the form of nanoparticles;XPS spectra and Soxhlet extractor experiments showed that silane was loaded in the form of chemical bonds;the saturation magnetization of MSMNPs was not significantly affected after loading silane.MSMNPs had good adsorption performance for Cr(VI).The results showed that the adsorption rate of MSMNPs for Cr(VI)was very fast and MSMNPs reached saturation within 1 minute.The maximum adsorption amount of MSMNPs for Cr(VI)was 7.94 mg/g.When the concentration of Cr(VI)was lower than 5 mg/L,the removal rate of Cr(VI)by MSMNPs could reach more than 95%.MSMNPs had good selectivity for Cr(VI),but high p H was not conducive to the adsorption and removal of Cr(VI).MSMNPs were desorbed with 1 mol/L Na OH solution and regenerated with 0.05 mol/L HCl solution.The results showed that the adsorption amount of MSMNPs for Cr(VI)could still be maintained above 75% after five cycles of adsorption-desorption-regeneration,indicating that MSMNPs could be reused.The results showed that GO/HDTMA aerogels could be prepared by using HDTMA to modify GO.When the content of HDTMA was between6.4%～11.5%,GO/HDTMA hydrogels and stable aerogels could be formed.The XRD spectra showed that the appropriate ratio of gravity and repulsion between GO sheets and the random loose arrangement were the key to the formation of hydrogels and stable aerogels.SEM confirmed the threedimensional porous structure of GO/HDTMA aerogels.FTIR and XPS patterns confirmed the successful loading of HDTMA.GO/HDTMA aerogels had good adsorption performance for Cu(II)and BPA.The results showed that the maximum adsorption amount of GO/HDTMA for Cu(II)was 59.88mg/g,and the adsorption equilibrium time was 1h.The maximum adsorption amount for BPA was 140.85mg/g,and the adsorption equilibrium time was 2h.The adsorption processes of Cu(II)and BPA by GO/HDTMA were both spontaneous and exothermic.The increase of p H promoted the adsorption of Cu(II)and BPA.Improving ionic strength inhibited the adsorption of Cu(II),but promoted the adsorption of BPA.GO/HDTMA aerogels were desorbed with 1mol/L HCl,and regenerated by adjusting p H.The results showed that the adsorption amount of GO/HDTMA for Cu(II)and BPA could still be maintained above80% after five cycles of adsorption-desorption-regeneration,indicating that GO/HDTMA had good desorption and regeneration performance,and could be reused.The three-dimensional structure of GO/HDTMA filter column was stable,which played an important role in adsorption and filtration of simulated wastewater containing Cu(II)prepared from Huangpu River water.In conclusion,two kinds of nano-adsorbents which could be easily separated and reused were successfully prepared by modification with organic compounds.MSMNPs had good removal performance for anionic heavy metal pollutants.MSMNPs could be rapidly separated from water by external magnetic field.GO/HDTMA aerogels had good removal performance for cationic heavy metal pollutants and phenolic compounds.GO/HDTMA aerogels could be made into filter column because of their good porosity and permeability.The filter column could discharge tail water while retaining pollutants.