Two novel chelating adsorbents are developed for the effective and selective extraction of Hg(ii) and Pb(ii) ions from contaminated water sources.

In this study, the novel adsorbent UIO-66-IT was synthesized to extract mercury and phosphate ions from contaminated water. The synthetic strategy involved the preparation of the metal−organic framework (UIO-66-NH 2 ) followed by post-synthetic modification using the chelating ligand 2-imino-4-thiobiuret to form the UIO-66-IT adsorbent. The structure and the morphology of the adsorbent were investigated by a variety of analytical techniques including Fourier transform infrared, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and Brunauer−Emmett−Teller surface area measurements. The adsorption of mercury and phosphate was optimized by studying the effect of pH, initial concentration, contact time, dose, temperature, and competitive ions. The results revealed exceptionally high adsorption capacities toward mercury and phosphate ions of 580 and 178 mg/g, respectively, at pH = 5.5 and an initial concentration of 1500 and 1000 mg/L. The adsorption isotherms are in excellent agreement with the Langmuir isotherm model, indicating the formation of a monolayer on the surface of UIO-66-IT. The kinetics of adsorption fit well with the pseudo-second-order kinetics model, which suggests the chemical adsorption of mercury ions via the nitrogen and sulfur functional groups of the adsorbent and the physical adsorption of phosphate anions by protonated functional groups on the surface of the UIO-66-IT adsorbent. Selectivity studies showed removal efficiencies of 98.9% Hg(II) from a solution containing a mixture of metal ions at 25 mg/L. Regeneration studies showed that the adsorbent can be recycled several times by using nitric acid for mercury removal and sodium chloride for phosphate removal. Removal efficiencies were higher than 99% for both regenerations. Due to the simple synthetic strategy via cost-effective starting materials, unique chemical structure, rapid adsorption kinetics, and high surface area, which lead to excellent removal efficiency, stability, and excellent regeneration, UIO-66-IT is introduced as a unique adsorbent for the selective removal of mercury and phosphate ions to remediate polluted water.

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Heavy metal ions represent one of the most toxic and environmentally harmful pollutants of water sources. This work reports the development of a novel chelating nitrogen-doped carboxylated porous carbon (ND-CPC) adsorbent for the effective removal of the heavy metal ions Pb(II), Hg(II), and Cr(VI) from contaminated and polluted water sources. The ND-CPC adsorbent is designed to combine four different types of nitrogen functional groups (graphitic, pyrrolic, pyridinic, and pyridine oxide) with the carboxylic acid functional groups within a high surface area of 1135 ± 20 m 2 /g of the porous carbon structure. The ND-CPC adsorbent shows exceptionally high adsorption affinity for Pb(II) with a capacity of 721 ± 14 mg/g in addition to high uptake values of 257 ± 5 and 104 ± 2 mg/g for Hg(II) and Cr(VI), respectively. The high adsorption capacity is also coupled with fast kinetics where the equilibrium time required for the 100% removal of Pb(II) from 50 ppb and 10 ppm concentrations is 30 s and 60 min, respectively. Even with the very high concentration of 700 ppm, 74% uptake of Pb(II) is achieved within 90 min. Removal efficiencies of 100% of Pb(II), 96% of Hg(II), 91% of Cu(II), 82% of Zn(II), 25% of Cd(II), and 13% of Ni(II) are achieved from a solution containing 10 ppm concentrations of these ions, thus demonstrating excellent selectivity for Pb(II), Hg(II), and Cu(II) ions. Regeneration of the ND-CPC adsorbent shows excellent desorption efficiencies of 99 and 95% for Pb(II) and Cr(VI) ions, respectively. Because of the fast adsorption kinetics, high removal capacity and excellent regeneration, stability, and reusability, the ND-CPC is proposed as a highly efficient remediation adsorbent for the solidphase removal of Pb(II), Hg(II), and Cr(VI) from contaminated water.

Polyacrylonitrile nanoparticles grafted on ethylene diamine functionalized partially reduced graphene oxide (PAN-PRGO) was prepared via in situ emulsion polymerization and was further modified to contain amidoxime, amdinoethylene diamine, and carboxylic groups on the surface of the graphene nanosheets via partial hydrolysis of the nitrile groups on the polymer chains of the composite using (4% NaOH, 20 min) (HPAN-PRGO). The properties and morphologies of the prepared composites were compared through FTIR, UV-Vis, Raman spectra, XRD, SEM, TEM, and XPS analysis. The results revealed that polyacrylonitrile nanoparticles were grafted on the surface of the aminated graphene oxide nanosheets via the reaction between the free amino groups of the ethylene diamine modified graphene oxide nanosheets and nitrile groups of acylonitrile (AN). The obtained HPAN-PRGO composite was evaluated for its chelating property with Hg(II) ions. The effect of initial pH, initial concentration of the Hg(II), adsorbent dose, and contact time on the extraction of Hg(II) ions using HPAN-PRGO were investigated. The adsorption experiments indicated that HPAN-PRGO exhibits higher affinity toward Hg(II). The maximum uptake capacity for the extraction of Hg(II) ions on HPAN-PRGO was 324.0 mg/ g at pH 5. The HPAN-PRGO shows a 100% removal of Hg(II) at concentrations up to 50 ppm, and the adsorption is exceptionally rapid showing more than 80.0% removal within 15 min and 100.0% of q e within 1.5 h at 800 ppm concentration. The Langmuir isotherm model and pseudo-second-order kinetic model have showed good fitness with the practical data. The XPS analysis of HPAN-PRGO before and after adsorption revealed the chelation adsorption mechanism between mercury and amine, amide, amidoxime, and carboxylic

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Silver nanoparticles (Ag-NPs) exhibit vast potential in numerous applications, such as wastewater treatment and catalysis. In this study, we report the green synthesis of Ag-NPs using Acacia ehrenbergiana plant cortex extract to reduce cationic Rhodamine B (RhB) dye and for antibacterial and antifungal applications. The green synthesis of Ag-NPs involves three main phases: activation, growth, and termination. The shape and morphologies of the prepared Ag-NPs were studied through different analytical techniques. The results confirmed the successful preparation of Ag-NPs with a particle size distribution ranging from 1 to 40 nm. The Ag-NPs were used as a heterogeneous catalyst to reduce RhB dye from aqueous solutions in the presence of sodium borohydride (NaBH4). The results showed that 96% of catalytic reduction can be accomplished within 32 min using 20 μL of 0.05% Ag-NPs aqueous suspension in 100 μL of 1 mM RhB solution, 2 mL of deionized water, and 1 mL of 10 mM NaBH4 solution. The results followed a zero-order chemical kinetic (R 2 = 0.98) with reaction rate constant k as 0.059 mol L–1 s–1. Furthermore, the Ag-NPs were used as antibacterial and antifungal agents against 16 Gram-positive and Gram-negative bacteria as well as 1 fungus. The green synthesis of Ag-NPs is environmentally friendly and inexpensive, as well as yields highly stabilized nanoparticles by phytochemicals. The substantial results of catalytic reductions and antimicrobial activity reflect the novelty of the prepared Ag-NPs. These nanoparticles entrench the dye and effectively remove the microorganisms from polluted water.