Preparation Of Organic Functionalized Graphene Oxides And Their Adsorption Performances For Heavy Metal Ions

With the rapid development of economy,a large number of wastes containing heavy metal ions are directly or indirectly discharged into the ecological environment,bringing heavy metal pollution to the environment.Heavy metal ions are highly toxic,carcinogenic,non-degradable,and bioconcentrated.Heavy metal pollution has brought great harm to human health and the ecological environment.At present,the main methods of heavy metal pollution treatment include chemical precipitation,ion exchange,membrane separation,biotechnology and adsorption.The adsorption method is considered to be the most promising method for the treatment of heavy metal pollution due to its simple operation and cost-effectiveness.Therefore,looking for efficient,economical and environmentally friendly adsorbents has become the key.In this paper,graphene oxide was first prepared by using graphite as the raw material..Then,three kinds of graphene oxide composite materials functionalized with heteroatom-containing organic groups were prepared by a variety of modification methods.The structure of the materials was characterized and its adsorption capacity for typical heavy metal ions were investigated.The main research contents are as follows:（1）Preparation of thiosemicarbazide functionalized graphene oxide composite material and its adsorption performance for Hg（Ⅱ） and Pb（Ⅱ）A novel thiosemicarbazide functionalized graphene oxide composite adsorbent（TSCGO） was synthesized through the silanization reaction between graphene oxide and3-aminopropyltriethoxysilane（APTES）,and the crosslinking between the amino functionalized graphene oxide and thiosemicarbazide with formaldehyde.The structure,morphology and thermostability of TSCGO were characterized by FT-IR、XRD、SEM、TGA、BET and Zeta potentiometric analysis.The characteristic results verified that TSCGO was successfully acquired.The adsorption of TSCGO for Hg²⁺,Pb²⁺,Cd²⁺,Cu²⁺,Zn²⁺ was compared.The results showed that TSCGO owned high uptakes for adsorption of Hg²⁺and Pb²⁺.Main adsorption parameters of TSCGO for Hg²⁺and Pb²⁺ were studied.The adsorption of Hg²⁺and Pb²⁺on TSCGO was better fitted with the pseudo-second-order model and the Langmuir isotherm model,which indicated that the adsorption was a chemical process with monolayer.The maximum uptakes of TSCGO for Hg²⁺ and Pb²⁺ were 1116 and 1012 mg g^-1,respectively,which were much higher than those of some reported adsorbents.TSCGO could be effectively regenerated with EDTA.（2）Preparation of thiosemicarbazide functionalized graphene oxide/chitosan composite material for adsorption of Hg（Ⅱ）A novel thiosemicarbazide functionalized graphene oxide@chitosan composite adsorbent（TSCGC） was firstly prepared through the silanization between graphene oxide and3-aminopropyltriethoxysilane（APTES）,and the crosslinking between the amino functionalized graphene oxide,chitosan and thiosemicarbazide with formaldehyde.Its structures and morphologies were characterized by FT-IR,XRD,SEM,TGA,BET and zeta potential.The adsorption of TSCGC for Hg²⁺、Pb²⁺、Cd²⁺、Zn²⁺和Cu²⁺ was contrasted.The results manifested that TSCGC had high uptake for Hg²⁺.Main parameters of adsorption such as initial pH,contact time,concentration,temperature,adsorbent dosage and coexist ions for Hg²⁺ solution on TSCGC were further explored.The adsorption was fast which could reach equilibrium within 20 min.The pseudo-second-order and the Langmuir isotherm models were better matched with the experimental data,suggested that the adsorption was a chemical process.The maximum adsorption capacity of TSCGC was 1203 mg g^-1.The adsorption was a spontaneous and endothermic process.Temperature rise was favorable for the adsorption.In50 ml of 100 mg L^-1 Hg²⁺solution at 298 K,the removal of Hg²⁺ could achieve 96.5%with100 mg TSCGC.TSCGC could be regenerated with EDTA.（3）One-pot preparation of thiosemicarbazide functionalized graphene oxide/chitosan composite adsorbent and its adsorption performance for Hg（Ⅱ）A thiosemicarbazide functionalized graphene oxide@chitosan composite adsorbent（TGCS） was prepared by the one-pot cross-linking reaction between graphene oxide,chitosan and thiosemicarbazide using glutaraldehyde as a crosslinker.The composition,structure,morphology and thermal stability of TGCS were characterized by FT-IR,XRD,SEM,TGA and Zeta potential.The experiment compared the adsorption of Hg²⁺,Pb²⁺,Cd²⁺,Zn²⁺ and Cu²⁺on TGCS,and the results showed that TGCS had higher adsorption performance for Hg²⁺.The maximum adsorption capacity for Hg²⁺ at 298 K was 1514 mg g^-1.The adsorption processes followed the pseudo-second-order kinetic and Langmuir isotherm models.Thermodynamic experiments showed that the adsorption of Hg²⁺ by TGCS was a spontaneous endothermic process.In 50 ml of 0.0025 mol L^-1 Hg²⁺ solution at 298 K,the removal rate could reach 94.9% with 100 mg TGCS.TGCS could be regenerated with EDTA.