Study On The Preparation And Adsorption Properties Of Low-cost Adsorbent For Heavy Metal Ion

Heavy metal is a kind pollutant with high toxicity in ecological environment. Somedissolved heavy metal ions can be enriched in aquatic food chains, enter into humanbodies through aquatic products, and thus brings about serious poisoning to humanbeings.With the development of the composite materials, the requirement of themodified inorganic composite materials was increased rapidly. Because of itsadvantages of abundant reserves, low prices and the stability of the physical andchemical properties, the different composite materials prepared from clays attractedextensive attention. After being modified by organic materials, the different organicfunctional groups can be introduced into the surface of the clay, these functionalgroups can form metal complexing compound with metal ions and improve theadsorption capacity of metal ions, so that clay has been more widely used.Nanoscale zero-valent iron (nZVI) has shown good potential to remove metalsand other aqueous pollutants. Its physicochemical properties and reductive capacitycan facilitate rapid decontamination of polluted water. However, the effectiveness ofnanoscale zero-valent iron (nZVI) to remove heavy metals from water is reduced byits low durability, poor mechanical strength, and tendency to form aggregates. Toovercome these problems and shows good potential to remove metal ions from water.The dissertation included following contents:1. The natural palygorskite modified by γ-Aminopropyl triethoxysilane andpolyethlenimine was used to investigate the adsorption behavior of Pb(II) ions fromaqueous solutions, and the adsorbent was characterized by the methods of FT-IR、SEM、TG and EA. The effects of pH, the amount of the adsorbent, contact time andtemperature on the removal of f Pb(II) were investigated. The results had indicatedthat the best conditions followed: the temperature was313K, the adsorbent amountwas10mg and the pH was4, contact time was180min, the maximum adsorptioncapacity was588.2mg·g-1. Adsorption isotherm was well described by Langmuirmodel. The kinetic data indicated that the adsorption fitted well with thepseudo-first-order kinetic model as well as pseudo-second-order kinetic model.2. The natural palygorskite modified by Hydroxy aluminium and nanoscalezero-valent iron was used to investigate the adsorption behavior of Cu(II) and Ni(II) ions from aqueous solutions, and the adsorbent was characterized by the methods ofFT-IR、TEM、and XRD. The changes of the parameters of pH, contact time andtemperature were tested in the adsorption experiments. The results had indicated thatthe pH was4, contact time was60min and the amount of the adsorbent was10mg,the maximum adsorption capacity was787.4mg·g-1、701.4mg·g-1, respectively.Adsorption isotherm was well described by Langmuir model. The kinetic datasindicated that the adsorption fitted well with the pseudo-second-order kinetic model.Thermodynamic parameters, such as Gibbs energy free (△G°), enthalpy (△H°) andentropy (△S°), were estimated. Results suggested that the adsorption process was aspontaneous and endothermic process with positive enthalpy. The adsorptionmechanism of Cu(II) is reduction, Ni(II) removal mechanism is: the surfaceadsorption-reduction mechanism.3. The composite materials of the walnut shell podwer support nanoscalezero-valent iron were prepared to adsorb Pb(II), Cu(II), and Ni(II)of the industrialwastewater and it was characterized by the methods of FT-IR、TEM and XRD. Theeffects of pH, contact time, temperatute and selectivity of different metal ions wereinvestigated. For Pb(II), Cu(II) and Ni(II), the thermodynamic curves fitted theLangmuir model, The kinetic datas indicated that the adsorption fitted well with thepseudo-second-order kinetic model. The adsorption mechanism of Pb(II) isreduction, Cu(II) and Ni(II) removal mechanism are: the surfaceadsorption-complexation mechanism.