| With the rapid development of Science technology,nanomaterials have been widely applied in many fields due to their excellent physicochemical properties.However,it is inevitable that nanomaterials are released into ecosystem and may cause serious environmental pollution as a contaminant during production,transport,use,and disposal processes.Nanomaterials can cause high accumulation and long-term retention in the air,water,and soil,which are threatening the ecological environment.Different from traditional pollutant,nanomaterials have many typical characteristics such as small size effect,quantum tunnelling effect,and so on.Nanomaterials enter into the organism may cause special biological effects,which can damage gene,cell,and organ.At present,the study of the biological safety for nanomaterials is in the initial stage and the cognition of biological toxicity is still quite limited.So far,although nanomaterials have not resulted in massive pollution yet,there are still many potential risks.In this study,graphene oxide(GO)was selected as the representative of nanomaterials and a variety of methods were used to study the coagulation behavior and interaction mechanism of GO in aqueous solutions.The rapid and efficient removal of GO can effectively avoid the possible environmental pollution and other potential risks,which was significant to its large-scale applications.Herein,we adopted different methods to prepare a variety of materials that were applied to the coagulation of GO in different environmental conditions.The material properties including structure and characteristic were investigated in detail.Furthemore,many different environmental factors such as time,temperature,pH,and ionic strength were also studied to explore the coagulation behavior of GO.Based on the characterization analysis and combined with the batch experiments,the interaction mechanisms were proposed.The main research findings and innovative points are listed as follows:(1)The experimental results showed that Mg/Al-LDHs,Mg/Al/La-LDHs,Mg/Al/La-CLDHs,MgO,CS-MgO,C@La-TiO2,and C@Ce-TiO2 showed excellent removal effect for GO.The maximum removal capacities of GO can reach 565.8 mg/g on Mg/Al/La-CLDHs and 435.5 mg/g on CS-MgO,respectively.The coagulation process was an endothermic process,indicating that high temperature was advantageous to GO removal.However,the random motion of nanoparticles increased when the temperature was too high,which reduced the system stability and led to the slightly decrease of GO removal.Compared to monovalent cations,divalent and trivalent cations can effectively improve the removal of GO.More importantly,the coagulation process would not cause secondary pollution in practical applications.(2)The coagulation of GO on Mg/Al-LDHs,Mg/Al/La-LDHs,and Mg/Al/La-CLDHs was dependent on pH and almost unaffected by ionic strength.The analysis results proved that the coagulation of GO only occurred at the surface and did not destroy the main structure of materials.Moreover,these materials had a good reusability for the removal of GO from aqueous solutions,which can effectively reduce the use cost.(3)The coagulation of GO on MgO and CS-MgO was influenced by pH.The kinetics study showed that the coagulation of GO on MgO reached the equilibrium state in 20 min,revealing a good application prospect.Based on density functional theory calculation,characterization analysis,and batch experiments,it can be concluded that the coagulation of GO was mainly dominated by electrostatic attraction and hydrogen bond.(4)The removal of GO and Cr(VI)on C@La-TiO2 and C@Ce-TiO2 demonstrated that these materials can be used for other environmental pollutants removal again after GO coagulation,which can improve the removal efficiency of pollutants and avoid wasting.In conclusion,we revealed the coagulation behavior and interaction mechanism of GO in different water environment system,which can provide new insights into the physicochemical behavior and ecological effect of GO in the complex environment system. |
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