Surface Functionalization Of Hydrogen Titanate Nanomaterials And Their Adsorption Properties For Dyes

With the rapid development of chemical industries such as polymers,textiles,refineries,leather and plastics,dye pollution becomes an increasingly serious problem in modern society.Once the untreated dye wastewater is discharged into water,it will certainly bring about many environmental problems and threaten the health and life of human beings,animals and plants.In the traditional treatment of dye wastewater,adsorption is considered to be one of the most widely used methods because of its low cost,simple operation and small impact on the environment.However,there are some disadvantages such as insufficient adsorption capacity,poor long-term stability and unsatisfactory recoverability in practical application for most of the adsorbents.So,hydrogen titanate nanowires with excellent chemical stability are used as raw materials to prepare a new adsorbent with high adsorption efficiency,excellent stability and easy recovery by functionalizing their surfaces.The main results obtained in this paper are as follows:1.Chitosan modified hydrogen titanate nanowires are prepared by simple soaking-filtration method for removel of anionic dyes.After modification,the hydrogen titanate nanowires are coated with chitosan to form a coating layer with a thickness of 7 nm.The modification of chitosan improves the mechanical strength of hydrogen titanate nanowires from 0.4 MPa to 11.1 MPa.Congo red is selected as the model dye to study the adsorption behavior of chitosan modified hydrogen titanate nanowires.The adsorption kinetics data show that the adsorption process conforms to pseudo-second-order kinetic model.The Freundlich isotherm model is most suitable for simulating the adsorption process.Thermodynamic analysis shows that the adsorption is a spontaneous process.The adsorption capacity and removal rate of chitosan modified hydrogen titanate nanowires for congo red reach 374.4 mg g^-1 and99.5%,respectively.Chitosan modified hydrogen titanate nanowires exhibit good adsorption performance in the p H range of 2.5-12.5.Meanwhile,after 15 cycles of adsorption and desorption,the removal rate of congo red remain above 98.7%.2.Hydrogen titanate nanowires with high specific surface area and polydopamine with rich functional groups are used to prepare polydopamine coated hydrogen titanate nanowires(PDA-HTN)via dopamine self-polymerization.The obtained adsorbent can be used selectively adsorb and separate methylene blue.The adsorption characteristics of PDA-HTN are studied by kinetics,isotherm and thermodynamics.The results show that the adsorption conforms to pseudo-second-order kinetic model and the Freundlich isotherm model,and is a spontaneous adsorption process.At the same time,the adsorption capacity of PDA-HTN for methylene blue can reach 617.3 mg g^-1.PDA-HTN can be used selectively adsorb methylene blue from mixed dye solutions.In addition,PDA-HTN can be used adsorb methylene blue in Na Cl solution with ionic concentration up to 0.5mol L^-1,and the increase of ionic concentration in Na Cl solution will improve the adsorption performance of PDA-HTN for methylene blue.The adsorption of methylene blue by PDA-HTN is the synergistic effects of?-?interaction,electrostatic interaction,hydrogen bonding and 1,4-Michael addition reaction.Meanwhile,PDA-HTN has good cyclic adsorption property,the removal rate of methylene blue remains above 97.7%after 12 cycles of adsorption-desorption.