|
چکیده
|
ABSTRACT: Three zinc(II) metal-organic frameworks, [Zn2(oba)2(4-bpdb)]·(DMF)x (TMU-4), [Zn(oba)(4-bpdh)0.5]n·(DMF)y (TMU-5) and [Zn(oba)(4-bpmb)0.5]n·(DMF)z (TMU-6), (H2oba = 4,4'-oxybisbenzoic acid, 4-bpdb = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene, 4-bpdh = 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene and 4-bpmb = N1,N4-bis((pyridin-4-yl)methylene)benzene-1,4-diamine), containing azine-functionalized pores have been successfully synthesized via mechanosynthesis as a convenient, rapid, low cost, solventless and green process. These MOFs were studied for removal and extraction of some heavy metal ions from aqueous samples and the effect of basicity and void space of these MOFs on adsorption efficiency were evaluated. The results showed that under trace amounts of metal ions the basicity of N-donor ligands in MOFs determines adsorption efficiency of the metal ions with them. Contrariwise, under high concentrations of metal ions, void space of the MOFs has the main role in adsorption process. The studies conducted revealed that among the three MOFs, TMU-6 has less adsorption efficiency for metal ions compared to the other two MOFs. The result can be attributed to more basicity of azine groups on TMU-4 and TMU-5 pore walls as compared to TMU-6, in which the N-donor ligand has imine groups. Subsequently, TMU-5 was chosen as an efficient sorbent for extraction and preconcentration of trace amounts of some heavy metal ions including Cd(II), Co(II), Cr(III), Cu(II) and Pb(II) followed by their determination via flow injection inductively coupled plasma optical emission spectrometry. Several variables affecting the extraction efficiency of the analytes were investigated and optimized. The optimized methodology exhibits a good linearity between 0.05-100 μg L−1 (R2> 0.9935) and detection limits in the range of 0.01-1.0 μg L−1. The method has enhancement factors between 42 and 225, and relative standard deviations (RSDs%) of 2.9 to 6.2%. Subsequently, the potential applicabili
|