• Applied Chemistry for Engineering
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• v.34 no.5
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• pp.556-565
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• 2023

Fast industrial and agricultural expansion result in the production of heavy metal ions (HMIs). These are exceedingly hazardous to both humans and the environment, and the necessity to eliminate them from aqueous systems prompts the development of novel materials. In the present study, a UIO-66 (COOH)₂ metal-organic framework (MOF) containing free carboxylic acid groups was post-synthetically modified with L-glutamic acid via the solid-solid reaction route. Pristine and glutamic acid-treated MOF materials were characterized in detail using several physicochemical techniques. Single-ion batch adsorption studies of Pb(II) and Hg(II) ions were carried out using pristine as well as amino acid-modified MOFs. We further examined parameters that influence removal efficiency, such as the initial concentration and contact time. The bare MOF had a higher ion adsorption capacity for Pb(II) (261.87 mg/g) than for Hg(II) ions (10.54 mg/g) at an initial concentration of 150 ppm. In contrast, an increased Hg(II) ion adsorption capacity was observed for the glutamic acid-modified MOF (80.6 mg/g) as compared to the bare MOF. The Hg(II) ion adsorption capacity increased by almost 87% after modification with glutamic acid. Fitting results of isotherm and kinetic data models indicated that the adsorption of Pb(II) on both pristine and glutamic acid-modified MOFs was due to surface complexation of Pb(II) ions with available -COOH groups (pyromellitic acid). Adsorption of Hg(II) on the glutamic acid-modified MOF was attributed to chelation, in which glutamic acid grafted onto the surface of the MOF formed chelates with Hg(II) ions.

• Applied Chemistry for Engineering
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• v.35 no.4
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• pp.352-359
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• 2024

Environmental pollution from heavy metal ions (HMIs) is a global concern. Recently, biosorption methods using cellulose sorbents have gained popularity. The objective of this study was to assess the removal efficiency of Cu(II), Pb(II), and Hg(II) ions at low concentration levels (100-700 ppb) from aqueous solutions using three different cellulose fiber-based filter media. Sample A was pure cellulose fiber, Sample B was 10% activated carbon-cellulose fiber, and Sample C was cellulose fiber-glass fiber-30% activated carbon-20% amorphous titanium silicate (ATS). The samples were characterized by several physicochemical techniques. The porosity measurements using N₂ sorption isotherms revealed that Samples A and B are nonporous or macroporous materials, whereas the addition of 50% filler materials into the cellulose resulted in a microporous material. The Brunauer-Emmett-Teller (BET) surface area and pore volume of Sample C were found to be 320.34 m²/g and 0.162 cm³/g, respectively. The single ion batch adsorption experiments reveal that at 700 ppb initial metal ion concentration, Sample A had removal efficiencies of 7.5, 11.5, and 13.7% for Cu(II), Pb(II), and Hg(II) ions, respectively. Sample B effectively eliminated 99.6% of Cu(II) ions compared to Pb(II) (14.2%) and Hg(II) (31.9%) ions. Cu(II) (99.37%) and Pb(II) (96.3%) ions are more efficiently removed by Sample C than Hg(II) (68.2%) ions. The X-ray photoelectron spectroscopy (XPS) wild survey spectrum revealed the presence of Cu(II), Pb(II), and Hg(II) ions in HMI-adsorbed filter media. The high-resolution C1s spectra of Samples A and B reveal the presence of -C-OH and -COOH groups on their surface, which are essential for HMIs adsorption via complexation reactions. Additionally, the ATS in Sample C facilitates the adsorption of Pb(II) and Hg(II) ions through ion exchange.