RESUMO
The public health and environment are currently facing significant risks due to the discharge of industrial wastewater, which contains harmful heavy metals and other contaminants. Therefore, there is a pressing need for sustainable and innovative technologies to treat wastewater. The main objective of this research was to develop novel composites known as chitosan, Padina pavonica, Fe(III), and nano MgO incorporated onto pomegranate peel with the specific purpose of removing Cd (II) and Cu (II) ions from aqueous solutions. The characterization of these nanocomposites involved the utilization of several analytical methods, including Fourier-transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, thermal gravimetric analysis, and X-ray photoelectron spectroscopy. The efficiency of these nanocomposites was evaluated through batch mode experiments, investigating the impact of factors such as pH, initial concentration, contact time, and adsorbent dose on the adsorption of Cu(II) ions. The optimum conditions for the removal of ions were pH = 5 for Cu (II) and 6 for Cd (II), contact time: 120 min, adsorbent dosage: 0.2 g, initial metal ion concentration: 50 mg/L for each metal ion for the present study. The MgO@Pp demonstrated the highest removal efficiencies for Cu(II) and Cd(II) at 98.2% and 96.4%, respectively. In contrast, the CS@Fe-PA achieved removal efficiencies of 97.2% for Cu(II) and 89.2% for Cd(II). The modified MgO@Pp exhibited significantly higher total adsorption capacities for Cu(II) and Cd(II) at 333.3 and 200 mg/g, respectively, compared to CS@Fe-PA, which had capacities of 250 and 142 mg/g, respectively. The adsorption of Cd (II) and Cu (II) ions by MgO@Pp was found to be a spontaneous process. The R2 values obtained using the Freundlich and Redlich-Peterson models were the highest for the MgO@Pp composite, with values of 0.99, 0.988, 0.987, and 0.994, respectively, for Cu (II) and Cd (II). The pseudo-second-order equation was determined to be the best-fit kinetic model for this process. Reusability experiments confirmed that the adsorbents can be utilized for up to four regeneration cycles. Based on the findings of this study, MgO @ Pp is the most promising alternative and could be instrumental in developing strategies to address existing environmental pollution through adsorption.
RESUMO
Faujasite zeolites with a regular micropore and mesopore structure have been considered desirable scaffolds to stabilize luminescent silver nanoclusters (Ag CLs), while turning of the emission properties of the confined Ag CLs is still under investigation. In this study, the desilicated and dealuminated faujasite zeolites were first prepared to modify the zeolite framework and Si/Al ratio before Ag+ loading. With thermal treatment on the thereafter Ag+-exchanged zeolites, the Ag CLs formatted inside the D6r cages showed red-shifted emission in the desilicated zeolites and blue-shifted emission in the dealuminated zeolites, so that a tunable emission in the wavelength range of 482-528 nm could be obtained. Meanwhile, the full width at half maximum of the emission spectra is also closely related with framework modification, which monotonously increases with enhancing Si/Al ratio of host zeolite. The XRD, XPS, and spectral measurements indicated that the tunable luminescence properties of Ag CLs result from the controlling of local crystal field and coupling between host lattice and luminescent center. This paper proposes an effective strategy to manipulate the emission properties of Ag CLs confined inside zeolites and may benefit the applications of noble metal clusters activated phosphors in imaging and tunable emission.
RESUMO
A method for the synthesis of pharmacologically prospective arabinogalactan (AG) imidazole- and benzimidazole derivatives in a yield of up to 97 % via Au(III)-catalyzed hydroamination of AG propargyl ethers has been developed. It is found that in the presence of 5 mol% HAuC14 and 10-fold excess imidazole relative to the propargyl groups, the hydroamination successfully competes with cross-linking processes to afford products soluble in DMSO and aqueous HC1 solutions (degree of substitution of imidazolylpropenyl fragments 0.5-1.8, yield 62-97 %). It is established that under the conditions of hydroamination Au(III) is reduced to give mainly Au(0) and minor amounts of Au(I), which are contained in AG imidazole derivatives as particles of 190-640 nm in size. Hydrochlorides of Au-containing AG imidazole derivatives show high bacteriostatic activity with respect to test gram-positive microorganisms and thus confirming their prospects as new AG-derived bioactive agents.
RESUMO
In order to synthesize adsorbent that can effectively absorb heavy metals in a simple and economical way, this study described the fabrication of adsorbents based on cellulose acetate (CA). CA modified first by polyethyleneimine grafting (CAP) and then by ethylenediamine (CAPE) for enhancing Cu(II) and Pb(II) removal from water. The physico-chemical properties of the modified celluloses were analyzed. It was found that the adsorption functional groups (amino groups) were successfully grafted on cellulose and CAP converted from semi-crystalline to cellulose II after enhancement of ethylenediamine (EDA). Adsorption isotherm results showed that the Cu(II) and Pb(II) removal efficiency by CAPE was significantly higher than that by CAP, and CAP showed a higher adsorption capacity of Cu(II) and Pb(II) than CA, of which the adsorption isotherm modeled with Langmuir isotherms well. The adsorption capacity can significantly be affected by ionic strength and humic acid. Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) results demonstrated the complexation between amino groups and Cu(II)/Pb(II) played an important role for adsorption onto CAPE.