Control Of Morphology Of Cu-MOFs On Supported Electrode By Electrochemical Synthesisand Adsorption Performance For Mercury

Metal organic framework materials?MOFs?have been widely used in various fields because of their large specific surface area and rich pore structure.The synthesis method of MOFs is one of the current research hotspots.The traditional synthesis method of MOFs requiring high temperature and high pressure,long time,is hard to,while electrochemical synthesis of MOFs has many advantages compared to tradional method.For example,mild reaction conditions,short reaction times,simple equipment,control of the reaction process,etc.What is more,metal ions can be released by anodic oxidation and dissolution,without the addition of metal salts.In this paper,Cu-BDC metal organic framework was synthesized by electrochemical synthesis with copper as the anode,zinc as the cathode,terephthalic acid?H2BDC?as ligand and tetra butyl ammonium bromide?TBAB?as the conductive salt.The mechanism of electrochemical synthesis was deduced by cyclic voltammetry.The effect of TBAB template to the resulting samples was dedermined by EDS,TG,XRD,FTIR and N2 adsorption experiments.The results show that the TBAB is not only a conductive salt in the whole reaction system but also acts as a structural guide agent.The Cu-BDC was prepared by optimizing the reaction time,voltage,template concentration,etc.The result shows that Cu-BDC materials with lattice-like,flower-like and spherical micro-morphology were prepared with the increase of TBAB concentration.With the increase of voltage,Cu-BDC materials with lamellar lattice,flower shape and spherical shape and dense microstructure were prepared,respectively.By changing the type of conductive salt?tetrabutylammonium bromide,1-butyl-3-methylimidazolium bromide and cetyltrimethylammonium bromide?,it is possible to prepare flower-like,leavesand other different morphology of the Cu-BDC material and achieved a controlled preparation morphology of Cu-BDC.In order to solve the problem of heavy metal mercury pollution,especially for the efficient and rapid removal of Hg²⁺ in wastewater,the Cu-BDC metal organic framework synthesized by electrochemical method was modified by functional group mercapto group to prepare SH-Cu-BDC material and the material was used for the adsorption of Hg²⁺ in the wastewater.The results of EDS,FTIR and SEM indicated that the-SH group was successfully modified on the Cu-BDC.The EDS characterization of SH-Cu-BDC material after adsorption of Hg²⁺ shows that SH-Cu-BDC can adsorb Hg²⁺ in water and it has strong adsorption capacity.10 mg SH-Cu-BDC can absorb about 20 ml Hg²⁺ solution(300 mg·L^-1)at p H = 5.The adsorption reaches saturation after 60 min and the maximum capacity?saturated adsorption capacity?is about 585 mg·g^-1.The adsorption of Hg²⁺ on SH-Cu-BDC is monolayer and follows quasi-second-order kinetics and Langmuir adsorption isotherm.The saturated adsorption capacity is588.2 mg·g^-1,which close to the actual 585 mg·g^-1 obtained by Langmuir adsorption isotherm equation.