Synthesis Of CMC-MOF Membrane And Its Application In Removal Of Pb(?) In Aqueoes Solution

In recent years,with the rapid development of industry,the problem of heavy metal pollution has become more and more serious.The crops containing heavy metal eaten by human body often comes with a serious of safety problems,and will pose a great threat to human health.In order to solve the problem of heavy metal contaminated drinking water,sodium carboxymethyl cellulose?CMC?was introduced to act as a“molecular bridge”to synthesizecarboxymethylcellulosesodium-metalorganicframework/cloth?CMC-MOF/Cloth?composite membranes material as an adsorbent for heavy metal lead ions in this paper.The structural characterizations and adsorption capacity of the CMC-MOF/Cloth composite membranes were systematically investigated.In details,the results of the study are listed as following:1.Synthesis of CMC-MOF/Cloth composite membranes material by introducing CMC as a"molecular bridge"at room temperature.The morphology and the synthesis process of as-prepared CMC-MOF/Cloth composite membranes were characterized by scanning electron microscopy?SEM?and Fourier transform infrared spectroscopy?FT-IR?,indicating the highly uniform and compact ZnCo-ZIF metal-organic frameworks membrane was successfully synthesized on the surface of cloth fibers,and the average size of the synthesized ZnCo-ZIF crystals was 500-600 nm.Further,the synthesis process of the CMC-MOF/Cloth composite membranes be divided into two steps.First,the hydroxyl in CMC react with the Zn²⁺and Co²⁺,which facilitate the attachment between the cloth substrate and the precursor of the Zn/CoZIF crystals.Then,the divalent cations could react with the imidazole group in2-methylimidazole to form a continuous and uniform layer of Zn/Co-ZIF on the CMC layer.2.To investigate the adsorption properties of the CMC-MOF/Cloth composite membranes,a series of batch adsorption experiments were studied.The adsorption performance of CMC-MOF/Cloth composite membranes on heavy metal lead ions at different pH conditions was tested,and the results showed that the as-synthesized materials have the best adsorption capacity for heavy metal lead ions at pH 5 conditions.The adsorption behavior of the CMC-MOF/Cloth composite membranes was systematically studied using kinetic and equilibrium experiments.It can be concluded that the experimental data are better fitted to the pseudo-second-order model and Langmuir isotherm,suggesting that the chemisorption may be the controlling step in the heavy metal ion adsorption process,the adsorption process between CMC-MOF/Cloth composite membranes and lead ions could be considered as monolayer adsorption and that the distribution of the adsorption sites is homogeneous.The maximum adsorption capacity(q_max)of CMC-MOF/Cloth composite membranes toward lead ions calculated from the Langmuir model is up to 862.44 mg g^-1.What's more,the adsorption mechanism of CMC-MOF/Cloth composite membranes on lead ions was cation exchange by carboxyl,hydroxyl,and amino groups on adsorbent by FT-IR,and XPS analysis of CMC-MOF/Cloth composite membranes before and after lead ions adsorption.The performance of CMC-MOF/Cloth composite membranes towards different heavy metal ions were conducted.It can be concluded from result that the CMC-MOF/Cloth composite membranes possesses a much higher adsorption capacity toward Pb?II?ions than the other metal ions.The regeneration study is performed and the results illuminate that the removal efficiency of CMC-MOF/Cloth composite membranes toward lead ions remained79.12%after reused for five times,which demonstrate its good recycling potential for heavy metal removal.In addition,the CMC-MOF/Cloth composite membranes can rapidly decontaminate the concentration of lead ions with good removal efficiency using a filtration apparatus,and it has a good application prospect in the control of food hazards.