Green Synthesis of Silver Nanoparticles Using Acacia ehrenbergiana Plant Cortex Extract for Efficient Removal of Rhodamine B Cationic Dye from Wastewater and the Evaluation of Antimicrobial Activity.

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 (R2 = 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.

Highly fluorescent hematoporphyrin modified graphene oxide for selective detection of copper ions in aqueous solutions.

Here, a highly sensitive and selective copper ion (Cu2+) fluorescence sensor is reported. The Hematoporphyrin functionalized Graphene Oxide (HP-GO) fluorescence sensor were synthesized via esterification reaction between Graphene Oxide and Hematoporphyrin (HP). The HP-GO sensor was fully characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Scanning Electrom Microscopy (SEM), UV-Vis spectroscopy, Transmission Electron Microscopy (TEM), Fluor meter spectroscopy, X-Ray photoelectron spectroscopy(XPS), and Raman spectroscopy measurements. The HP-GO sensor advertised two linear regions over the range of 0-1.18 × 103 nM and 3.93 × 103 to 47.27 nM of copper (II) with detection limit of 54 nM in the aqueous solution. The selectivity of HP-GO for Cu2+ is much higher than that of other metal ions due to the presence of aza macrocyclic ring on the surface of HP-GO which has a high binding affinity with Cu2+. Additionally, the HP-GO shows wide pH viable range (pH 6-10). The effect of other metal ions on the fluorescence intensity of the HP-GO was also studied and other metal ions show a low interference response in the detection of Cu2+. HP-GO sensor manifests advantages of high reproducibility (The quenched fluorescence of HP/GO-Cu can be recovered by EDTA), attractive long term fluorescence stability (>21 days) in water, also remarkable selectivity regarding number of metal ions (Na+, K+, Ca2+, Fe3+, Fe2+, Al3+, Pb2+, Mn2+, Mg2+, Co2+, Ni2+, Cr6+, Cd2+, Hg2+, and Zn2+), low toxicity and can detect Cu2+ in real water samples which acquire well for its promising in environmental applications.

Melamine-based functionalized graphene oxide and zirconium phosphate for high performance removal of mercury and lead ions from water.

Heavy metal ions are highly toxic and widely spread as environmental pollutants. This work reports the development of two novel chelating adsorbents, based on the chemical modifications of graphene oxide and zirconium phosphate by functionalization with melamine-based chelating ligands for the effective and selective extraction of Hg(ii) and Pb(ii) from contaminated water sources. The first adsorbent melamine, thiourea-partially reduced graphene oxide (MT-PRGO) combines the heavier donor atom sulfur with the amine and triazine nitrogen's functional groups attached to the partially reduced GO nanosheets to effectively capture Hg(ii) ions from water. The MT-PRGO adsorbent shows high efficiency for the extraction of Hg(ii) with a capacity of 651 mg g-1 and very fast kinetics resulting in a 100% removal of Hg(ii) from 500 ppb and 50 ppm concentrations in 15 second and 30 min, respectively. The second adsorbent, melamine zirconium phosphate (M-ZrP), is designed to combine the amine and triazine nitrogen's functional groups of melamine with the hydroxyl active sites of zirconium phosphate to effectively capture Pb(ii) ions from water. The M-ZrP adsorbent shows exceptionally high adsorption affinity for Pb(ii) with a capacity of 681 mg g-1 and 1000 mg g-1 using an adsorbent dose of 1 g L-1 and 2 g L-1, respectively. The high adsorption capacity is also coupled with fast kinetics where the equilibrium time required for the 100% removal of Pb(ii) from 1 ppm, 100 ppm and 1000 ppm concentrations is 40 seconds, 5 min and 30 min, respectively using an adsorbent dose of 1 g L-1. In a mixture of six heavy metal ions at a concentration of 10 ppm, the removal efficiency is 100% for Pb(ii), 99% for Hg(ii), Cd(ii) and Zn(ii), 94% for Cu(ii), and 90% for Ni(ii) while at a higher concentration of 250 ppm the removal efficiency for Pb(ii) is 95% compared to 23% for Hg(ii) and less than 10% for the other ions. Because of the fast adsorption kinetics, high removal capacity, excellent regeneration, stability and reusability, the MT-PRGO and M-ZrP are proposed as top performing remediation adsorbents for the solid phase extraction of Hg(ii) and Pb(ii), respectively from contaminated water.

Multifunctional Binding Sites on Nitrogen-Doped Carboxylated Porous Carbon for Highly Efficient Adsorption of Pb(II), Hg(II), and Cr(VI) Ions.

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 m2/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 solid-phase removal of Pb(II), Hg(II), and Cr(VI) from contaminated water.