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Pollution of the environment is a serious issue nowadays, and finding a proper wastewater treatment is only small part of challenges that humans are facing. In order to find innovative ways for wastewater treatment, different techniques are applied, which lead to the production of new materials, such as ones made of polymeric nanofibers and materials with photocatalytic properties. In this study, nanofibers composite, synthetized from polyamide (PA) and UiO-66 Metal Organic Framework (MOF) by electrospinning method was used for degradation of Congo red dye from 10 ppm aqueous solution in batch conditions. Ultra-thin PA nanofiber membranes were produced with different ratios of MOF - 0.5 wt.%, 1 wt.%, 2 wt.% and 10 wt.% and prior the experiments, in order to be easily applied and removed from the solution, cut in the rectangular shape 1cm x 2 cm. FTIR, XRD and SEM are used for characterization of selected composites, prior and after sorption and photocatalytic experiments, while for determination of dye concentration UV-ViS spectrophotometer was used. The best performance in Congo red degradation was shown by membranes which contained 1 wt.% of MOF. FTIR spectra have shown that, upon the introduction of MOF particles into the PA fiber, reduction of all the peaks by the same amount in intensity indicates no interaction between MOF additive and PA matrix. Further, a new peak appeared after sorption at 590 cm-1 and disappeared after dye degradation induced by sun irradiation. XRD analysis has shown that there are no observable microstructural changes in composites upon sorption and cycling. Decreasing of the band gap of composite compared to pure MOF indicated increased photocatalytic activity. Reusability of composite membranes was investigated by performing experiments in multiple cycles, and results have shown that electrospun UiO-66/polyamide membranes have no significant changes in degradation efficiency of Congo red upon 4 cycles.

Metal-organic frameworks (MOFs), an exciting class of porous crystalline materials, are suitable for adsorptive removal of toxic heavy metal-ethylenediaminetetraacetic acid (M-EDTA) complexes from wastewater. In this paper, water-stable UiO-66(Zr) with well-defined morphology was successfully synthesized through a facile microwave-assisted solvothermal method and employed as nanotraps for the efficient capture of the three M-EDTA complexes, Cu-EDTA, Pb-EDTA, and Ni-EDTA. The adsorption behaviors, effects of solution pH and co-existing anions, as well as the eluant and desorption were investigated. The obtained UiO-66(Zr) showed good stability and excellent uptake capacity of M-EDTA in a wide pH range (3.0-10.0). UiO-66(Zr) exhibited a higher removal efficiency of Cu-EDTA (57.56 mg/g), Pb-EDTA (120.6 mg/g), and Ni-EDTA (54.27 mg/g). Based on the overall analysis results, our findings show that EDTA-metal complex ions can be adsorbed inside UiO-66(Zr) mainly through the Lewis-acid/-base interactions and possible anion-πinteraction with strong binding energies. Size-matching EDTA-metal complexes confined in the UiO-66(Zr) with flexible geometry would also contribute to the fast adsorption kinetics as well as the selective adsorption of different M-EDTA complexes. © 2020 Elsevier Ltd.

Development of method for the complete conversion of Cr-containing electroplating sludge (ES) into the black inorganic pigment was presented. Difficulties related to the ES complex, variable composition and inhomogeneity, where the dominant presence of Cr was followed by: Fe, P, Zn, Ni, Cu, etc., can be overcome by determination of the precise amount of Fe2O3 necessary to be added in order to firmly embed all the heavy metals into the pigment structure (i.e. the Fe0.7Cr1.3O3/FePO4 nanocomposite), taking care not only about weight/molar ratios, but also about average particle size, apparent densities, and volume fraction of the starting materials. As a source of Fe2O3, commercial (p.a.) Fe2O3 and two different Fe-wastes were used, thus completely fulfilling the principles of the circular economy. The obtained black inorganic pigments have consistent composition, no leaching of toxic metals, color (CIE L-a-b-values) comparable with those of commercial pigments and thus have the potential commercial large scale application. © 2021 Elsevier Ltd.

The recycling of heavy metals from solid wastes and transforming these metals into useful materials, such as metal oxides, nanocomposites, and metal–organic frameworks (MOFs), are beneficial for both sustainable development and environmental protection. MOFs are promising for adsorptive desulfurization, owing to their extremely high surface areas and tunable structures. In this paper, for the first time, MIL-53(Cr) was successfully fabricated from electroplating sludge (EPS) as a metal source through a facile hydrothermal method with and without HF. Our synthetic method is novel, green, scalable, and time-efficient. The obtained MIL-53(Cr) was employed as an adsorbent for adsorptive dibenzothiophene removal from liquid fuel. MIL-53(Cr) with HF exhibits a higher desulfurization capacity (40.11 mg g–1) than that of MIL-53(Cr) without HF (32.80 mg g–1). The improved adsorption performance of MIL-53(Cr) with HF is attributed to adding a small amount of HF, which produces highly crystalline and relativity pure MIL-53(Cr) microrods with a high surface area and porosity, and is due to a robust metal–sulfur interaction. Furthermore, the regenerated adsorbent can retain 94% of its initial sulfur adsorption capability even after 5 cycles, implying that MIL-53(Cr) prepared from Cr-EPS is an efficient adsorbent for fuel desulfurization. This study provides new insight for the production of high-value-added MOF materials from solid wastes following the principle of “resource reuse”.