Magnetic Carbon Nanosphere-based Functional Materials For Adsorption Of Quinoline From Coking Wastewater

This research aims at the efficient,selective,non-destructive,deep separation and removal of quinoline in coking wastewater,to alleviate the environmental problems caused by water pollution and realize non-destructive removal and resource recycling of quinoline.To overcome the disadvantages of existing adsorbents used in quinoline removal,such as complicated operation,low adsorption capacity,no selectivity and difficult recovery,this research started off with the type of adsorbents,designed and synthesized magnetic carbon nanosphere-based functional materials,characterized the morphology and structure of different materials,and investigated the adsorption properties of the materials towards quinoline in coking wastewater.This work provides a theoretical and technical basis for the advanced treatment of coking wastewater.The detailed results are as follows:(1)Preparation and adsorption property of solid magnetic carbon nanospheres functional material.Magnetic carbon nanospheres(MCNSs)dotting with Fe₃O₄nanoparticles were synthesized by solvothermal method.Further,KOH activation and HNO₃acidification of MCNSs were carried out to tune surface structure and property of MCNSs for the sake of adsorption improvement.The results show that both MCNSs and modified MCNSs(MCNSs-KH)are magnetic enough for solid-liquid separation,and can be used as adsorbents for rapid separation and reutilization towards quinoline in coking wastewater.After KOH activation and HNO₃acidification,the saturated adsorption capacity of MCNSs-KH is improved to 297.21 mg g^-1,much better than that of MCNSs(99.43 mg g^-1).MCNSs-KH show excellent adsorption performance and good regeneration.According to characterization analyses,KOH activation introduced abundant pore structures,which significantly increased the specific surface area of MCNSs;HNO₃acidification further increased the surface acidity of MCNSs,especially by introducing C=O functional groups,which promoted the acid–base interaction with weakly basic quinoline.From the results of adsorption kinetics,isotherm and thermodynamics,the spontaneous and exothermic adsorption process conformed to pseudo-second-order and Langmuir–Freundlich models better.(2)Preparation and adsorption property of magnetic surface molecularly imprinted functional material.In order to achieve the non-destructive removal and resource recycling of quinoline,and improve the adsorption selectivity of adsorbent,a novel magnetic surface molecularly imprinted polymer(SMIP/MCNSs)was prepared,using MCNSs as carrier,quinoline as template molecule and acrylamide(AAm)as functional monomer.The structure,morphology and adsorption behaviors of SMIP/MCNSs were investigated in detail.All results show that the imprinted layer thickness of SMIP/MCNSs is 9 nm,and SMIP/MCNSs exhibits enough magnetic response to meet the magnetic solid-liquid separation and recovery.The saturated adsorption capacity of SMIP/MCNSs for quinoline at 298 K reaches 131.22 mg g^-1.SMIP/MCNSs shows high selectivity for quinoline and excellent regeneration.The relative selectivity coefficient against phenol and pyridine interferents is 3.58 and 3.32,respectively.Also,SMIP/MCNSs possesses considerably stable adsorption performance for quinoline in neutral and alkaline environments,which is suitable for quinoline removal from real coking wastewater.The adsorption experiments confirm that the adsorption of quinoline by SMIP/MCNSs is similar with that by MCNSs.(3)Preparation and adsorption property of magnetic hollow carbon nanospheres functional material.In order to further solve the problems of complex preparation conditions and high reaction energy consumption of adsorbents,magnetic hollow carbon nanospheres(MHCNSs)with uniform particle size(40 nm)were ultrafast synthesized in 80 s by a novel microwave-assisted solvothermal method.Further,their growth mechanism and adsorption property towards quinoline in coking wastewater were discussed.The results show that surfactant P123acted as a template in the formation of MHCNSs.At 298 K,MHCNSs exhibited a saturated adsorption capacity of 155.23 mg g^-1towards quinoline in coking wastewater.Also,they showed excellent regeneration and magnetic solid-liquid separation advantages.Through investigating the influence of factors including p H,temperature,contact time and initial concentration on adsorption performance,it was found that MHCNSs realized their optimum adsorption capacity at p H=7,and possessed relatively stable adsorption capacity in alkaline aqueous solution.The adsorption kinetics,isotherm and thermodynamics results demonstrate that the pseudo-second-order kinetics and Langmuir–Freundlich model are best suited for quinoline adsorption on MHCNSs,and the adsorption is a spontaneous and exothermic chemisorption process.From above-mentioned study of magnetic carbon nanosphere-based functional materials,it can be found that the type of adsorbents directly determine their adsorption properties.The hollow structure significantly improves the adsorption property of magnetic carbon nanospheres.Activation and acidification greatly promote the adsorption of quinoline by magnetic carbon nanospheres.Therefore,the preferable adsorbent should have abundant pore structure,large specific surface area and suitable surface chemical environment.The magnetic carbon nanosphere-based molecularly imprinted functional material prepared by surface molecular imprinting technology achieves selective adsorption of quinoline,which provides a new way for environmental protection and resource regeneration.