| The heavy metal pollution has brought a serious threat to the ecological environment and human survival.In this work,three compounds,such as?-Fe2O3/carbon spheres,Bi2Fe4O9/C and TiO2/GO,were prepared,which were used for removing heavy metals from waste water by adsorption and photocatalytic techniques.The removal mechanism of heavy metal,e.g.chromium and copper,by as-prepared materials were discussed in detail.The work was summaried briefly as follows:?1??-Fe2O3/carbon spheres adsorbent was prepared through hydrothermal method using glucose as the carbon source,?NH4?2Fe?SO4?·6H2O)as the iron source and secondary water as solvent,which could be studied by adsorption of Cr???in aqueous solution.The composition and structure of adsorbents were characterized by SEM,TEM and XRD.It reached adsorption equilibrium in no more 4h and the removal efficiency for Cr???was 88%,which was 2.99 and 4.88 times of that over?-Fe2O3 and carbon spheres.The investigation on adsorption kinetics and isotherm showed that the pseudo-first-order kinetic and Langmuir isotherm models could well fit the experimental adsorption data.The maximum adsorption capacity of?-Fe2O3/carbon spheres for Cr???was found to 18.7 mg·g-1.Adsorption thermodynamics shows that the adsorption process is a spontaneous endothermic reaction.The experimental data show that ?-Fe2O3/carbon spheres adsorbent can be reused.?2?Bi2Fe4O9 nanoplate were prepared by hydrothermal method using Bi?NO3?3·5H2O and Fe?NO3?3·9H2O as raw materials.Bi2Fe4O9/C adsorbent was prepared by Bi2Fe4O9 and pine leaves as raw materials.They were studied by the adsorption of Cu?II?from aqueous solution.The specific surface area of Bi2Fe4O9 and Bi2Fe4O9/C were 13.35 m2·g-1 and 17.51 m2·g-1 respectively.The adsorption of Cu?II?at pH=5 was the best.The investigation on adsorption kinetics showed that the pseudo-second-order kinetic could well fit the experimental adsorption data.Thermodynamic survey on Gibbs free energy??G<0?,enthalpy??H>0?and entropy??S>0?demonstrated that the adsorption process was endothermic and spontaneous.The maximum adsorption capacity of Bi2Fe4O9 and Bi2Fe4O9/C were found to 42.7mg·g-1 and 61.61mg·g-1 respectively.The coexistence of Cl-,NO3-and SO42-has no effect on Cu???adsorption process,but PO43-will play a role in promoting.After recycling five times,the decline of adsorption capacity of product for Cu???was7.2% and 11.5%,which indicated that the adsorbent could be recycled in the removal of Cu???.Therefore,Bi2Fe4O9 nanoplate and Bi2Fe4O9/C might be potentially applied in the removal of heavy metal ions from aqueous solution.?3?The TiO2/GO composite was synthesized by hydrothermal method using Hummers modified graphene and tetrabutyl titanate as raw materials,which was used to remove of Cr???from simulated waste water.The materials were characterized and analyzed by SEM,XRD,BET,DRS and FTIR.The regular TiO2 particles are well-dispersed on the GO sheets and they were effectively combined.The specific surface area of TiO2 and TiO2/GO samples were 179.1 and 149.74mg·g-1,respectively.Under optimal degradation condition?4.0 g·L-1 photocatalyst and the solution pH was 2.0?,the adsorption,photocatalytic degradation and total removal ratio of Cr???over TiO2/GO was 65.7%,33.1% and 98.8% respectively.TiO2/GO photocatalytalyst reduction of Cr???process was achieved mainly through the superoxide radicals O2-and hole h+.Compared with TiO2,the photocatalytic degradation of Cr???by TiO2/GO has been improved effectively. |
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