Controllable Synthesis Of Transition Metal Oxide/carbon Composites With Noval Structure For Removal Of Pollution From Water

There are a variety of pollutants in industrial and municipal wastewater,and the heavy metal ions and persistent organic contaminants are two kinds of common toxic pollutants,which did great harm on aquatic organisms and human health.Metal oxides/carbon composites,combining the individual advantages of metal oxides and carbon,have promising potential in removing contaminants by adsorption or catalysis.This article designed and synthesized three kinds of transition metal oxide/carbon composites with novel structure,and investigated their performance for removing pollutants from water.1、Nano-sized metal oxides can effectively remove heavy mental ions and organic pollutants by adsorption or catalysis,but they still have some defects,such as poor stability,difficult recycle and low activity and so on.It is an effective method to resolve above mentioned problems by combining the metal oxides with graphene nanosheets（GO）.Under the protection of rGO nanosheets,the Mn-based nanofibers（Mn3（NA）2）accompanied with rGO nanosheets synthesized by one step method of nitrilotriacetic acid（NA）,manganese metal salts and GO under the hydrothermal condition,could still maintain the original wire-like morphology after thermal treatment in N2 atmosphere.The as-synthesized rGO-stabilized MnO/N-doped carbon nanofibers named as rGO-MnO/NC not only combine the individual advantages of rGO and MnO,but also contain abundant nitrogen derived from the carbonization of organic crosslinker（NA）,which promote the removal of pollutants.By the comparison of the effect of rGO content in the composites on the adsorption and catalysis performance and a series of characterization results,we conclude that the optimal rGO loading in these composites is 5wt% namely rGO-MnO/NC-2.The adsorption isotherms of Pb（II）ions onto pure MnO/NC and rGO-MnO/NC were well fitted by Langmuir model,and the adsorption kinetic of Pb（II）ions onto rGO-MnO/NC-2 was well described by pseudo-second-order model,which demonstrated the adsorption process is chemical adsorption.The theoretical maximum adsorption capacity of Pb（II）onto rGO-MnO/NC-2 was 222.2mg g-1 at initial pH of 5 and25℃,which is almost twice as high as that of pure MnO/NC.Moreover,rGO-MnO/NC-2exhibits the best catalytic activity for the catalytic degradation of MB.Therefore,the rGO loading in rGO-MnO/NC plays an important role in the performance of removingpollutants,and these materials have great potential to remove heavy metal ions and organic pollutants from wastewater.2、Fe-carbon nanocomposites（FeO_x-C）as heterogeneous Fenton-like catalysts were synthesized by the pyrolysis of iron based mental-organic frameworks（MIL-88-Fe）,and the degradation removal of 4-nitrophenol（4-NP）in aqueous solution was used to evaluate the catalytic activity of FeO_x-C.The results showed 4-NP could be effectively degraded by FeO_x-C in the presence of hydrogen peroxide.Pyrolysis temperature significantly affected the component,structures,and performances of the catalysts,and the as-prepared FeO_x-C-500 exhibited the best catalytic performance.Furthermore,the effects of several reaction conditions,such as,catalyst loading,H₂O₂ dosage,reaction temperature,and initial pH on the catalytic degradation of 4-NP were extensively analyzed for the practical applications of Fe-C-500.At initial circumneutral pH of 6.21,89.0% of 50 mg/L 250 mL of 4-NP solution could be degradated after 75 min by the heterogeneous Fenton-like oxidation on the 20 mg of Fe O_x-C-500 in the presence of 200 μL H₂O₂.The results of activation energy and the reaction kinetics showed FeO_x-C-500 possessed a high catalytic activity in heterogeneous Fenton reaction of 4-NP.3、A series of core-shell ZIF-8@ZIF-67 with different ratio were synthesized by a simple synthesis process.Then,NC@GC composites with core-shell structure were successfully prepared by calcining ZIF-8@ZIF-67 in N2 atmosphere coupled with acidifying with 6M HCl.NC@GC-1 with low GC content shows the highest adsorption capacity of CBZ up to 180.2mg/g.The kinetic adsorption of CBZ on as-prepared composites matches well with pseudo-second-order model,which demonstrated the dominating chemisorption mechanism.The effect of temperature on CBZ adsorption was investigated,and with the increase of temperature,the adsorption capacities of CBZ on NC@GC decreased,which suggests the CBZ adsorption is exothermal.The effects of pH were also investigated,and the results showed that the adsorption capacities CBZ on surface of CBZ were stable at pH=2¹2.