Browsing by Author "Silvestri, Daniele"
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- ItemA new method for assessment of the sludge disintegration degree with the use of differential centrifugal sedimentation(TAYLOR & FRANCIS LTD, 2-4 PARK SQUARE, MILTON PARK, ABINGDON OR14 4RN, OXON, ENGLAND, 2019-01-01) Silvestri, Daniele; Waclawek, Stanislaw; Goncukova, Zuzanna; Thekkae Padil, Vinod Vellora; Grubel, Klaudiusz; Černík, MiroslavA novel method for assessing the disintegration degree (DD) of waste activated sludge (WAS) with the use of differential centrifugal sedimentation method (DCS) was shown herein. The method was validated for a WAS sample at four levels of disintegration in the range of 14.4-82.6% corresponding to the median particle size range of 8.5-1.6 mu m. From the several sludge disintegration methods used (i.e. microwave, alkalization, ultrasounds and peroxydisulfate activated by ultrasounds), the activated peroxydisulfate disintegration resulted in the greatest DD 83% and the smallest median particle size of WAS. Particle size distribution of pretreated sludge, measured by DCS, was in a negative correlation with the DD, determined from soluble chemical oxygen demand (SCOD; determination coefficient of 0.995). Based on the obtained results, it may be concluded that the DCS analysis can approximate the WAS disintegration degree.
- ItemA Polymeric Composite Material (rGO/PANI) for Acid Blue 129 Adsorption(MDPI, 2020-05-03) Kukulski, Tomasz; Wacławek, Stanisław; Silvestri, Daniele; Krawczyk, Kamil; Padil, Vinod V. T.; Fryczkowski, Ryszard; Janicki, Jarosław; Černík, MiroslavOver the years, polyaniline (PANI) has received enormous attention due to its unique properties. Herein, it was chosen to develop a new polymeric composite material: reduced graphene oxide/polyaniline (rGO/PANI). The composite was prepared by a simple and cost-effective fabrication method of formation by mixing and sonication in various conditions. The obtained materials were characterized and identified using various techniques such as scanning electron microscopy (SEM), Raman and ATR–FTIR spectroscopy, and X-ray diffraction (XRD). The objective of the paper was to confirm its applicability for the removal of contaminants from water. Water could be contaminated by various types of pollutants, e.g., inorganics, heavy metals, and many other industrial compounds, including dyes. We confirmed that the Acid Blue 129 dyes can be substantially removed through adsorption on prepared rGO/PANI. The adsorption kinetic data were modeled using the pseudo-first-order and pseudo-second-order models and the adsorption isotherm model was identified.
- ItemChemical oxidation and reduction of hexachlorocyclohexanes: A review(2019-01-01) Waclawek, Stanislaw; Silvestri, Daniele; Hrabák, Pavel; Padil, Vinod V. T.; Torres-Mendieta, Rafael; Waclawek, Maria; Černík, Miroslav; Dionysiou, Dionysios D.Lindane (gamma-hexachlorocyclohexane) and its isomers (HCH) are some of the most common and most easily detected organochlorine pesticides in the environment. The widespread distribution of lindane is due to its use as an insecticide, accompanied by its persistence and bioaccumulation, whereas HCH were disposed of as waste in unmanaged landfills. Unfortunately, certain HCH (especially the most reactive ones: gamma- and alpha-HCH) are harmful to the central nervous system and to reproductive and endocrine systems, therefore development of suitable remediation methods is needed to remove them from contaminated soil and water. This paper provides a short history of the use of lindane and a description of the properties of HCH, as well as their determination methods. The main focus of the paper, however, is a review of oxidative and reductive treatment methods. Although these methods of HCH remediation are popular, there are no review papers summarising their principles, history, advantages and disadvantages. Furthermore, recent advances in the chemical treatment of HCH are discussed and risks concerning these processes are given.
- ItemDisintegration of Wastewater Activated Sludge (WAS) for Improved Biogas Production(MDPI, 2019-12-21) Wacławek, Stanisław; Grübel, Klaudiusz; Silvestri, Daniele; Padil, Vinod V. T; Wacławek, Maria; Černík, Miroslav; Varma, Rajender SDue to rapid urbanization, the number of wastewater treatment plants (WWTP) has increased, and so has the associated waste generated by them. Sustainable management of this waste can lead to the creation of energy-rich biogas via fermentation processes. This review presents recent advances in the anaerobic digestion processes that have led to greater biogas production. Disintegration techniques for enhancing the fermentation of waste activated sludge can be apportioned into biological, physical and chemical means, which are included in this review; they were mainly compared and contrasted in terms of the ensuing biogas yield. It was found that ultrasonic- and microwave-assisted disintegration provides the highest biogas yield (>500%) although they tend to be the most energy demanding processes (>10,000 kJ kg−1 total solids).
- ItemGum Kondagogu/Reduced Graphene Oxide Framed Platinum Nanoparticles and Their Catalytic Role(MDPI, 2019-10-01) Venkateshaiah, Abhilash; Silvestri, Daniele; Ramakrishnan, Rohith K; Wacławek, Stanislaw; Padil, Vinod V. T; Černík, Miroslav; Varma, Rajender S.This study investigates an environmentally benign approach to generate platinum nanoparticles (Pt NP) supported on the reduced graphene oxide (RGO) by non-edible gum waste of gum kondagogu (GK). The reaction adheres to the green chemistry approach by using an aqueous medium and a nontoxic natural reductant-GK-whose abundant hydroxyl groups facilitate in the reduction process of platinum salt and helps as well in the homogenous distribution of ensued Pt NP on RGO sheets. Scanning Electron Microscopy (SEM) confirmed the formation of kondagogu gum/reduced graphene oxide framed spherical platinum nanoparticles (RGO-Pt) with an average particle size of 3.3 ± 0.6 nm, as affirmed by Transmission Electron Microscopy (TEM). X-ray Diffraction (XRD) results indicated that the Pt NPs formed are crystalline with a face-centered cubic structure, while morphological analysis by XRD and Raman spectroscopy revealed a simultaneous reduction of GO and Pt. The hydrogenation of 4-nitrophenol could be accomplished in the superior catalytic performance of RGO-Pt. The current strategy emphasizes a simple, fast and environmentally benign technique to generate low-cost gum waste supported nanoparticles with a commendable catalytic activity that can be exploited in environmental applications.
- ItemProduction of electrospun nanofibers based on graphene oxide/gum Arabic(ELSEVIER SCIENCE BV, PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS, 2019-03-01) Silvestri, Daniele; Mikšíček, Jiří; Waclawek, Stanislaw; Torres-Mendieta, Rafael; Padil, Vinod V. T.; Černík, MiroslavOver the last few years, the electrospinning technique has attracted significant attention for the production of novel nanofibrous materials. At the same time, the use of graphene oxide and the natural products extracted from plants and/or trees have become very popular in various fields of science. In this work, a new method for the production of nanofibers based on a combination of Gum Arabic (GA), as a natural tree gum exudate, PVA, as an environmentally-friendly stabilizer, and graphene oxide (GO) has been developed and characterized. SEM analysis showed fundamental differences on the surface of bare nanofibers with and without GO, and also significantly smaller fiber diameters in the case of the presence of GO (fibers <100 nm present). Raman spectroscopy confirmed and TGA analysis approximated the content of GO in the nanofibers. Adsorption of methylene blue on the produced nanofibrous membrane was about 50% higher in the presence of GO, which opens the possibility to use GO/GA/PVA fibers in several applications, for example for the removal of dyes.
- ItemSynthesis of Ag nanoparticles by a chitosan-poly(3-hydroxybutyrate) polymer conjugate and their superb catalytic activity(Elsevier Ltd, 2020-01-01) Silvestri, Daniele; Wacławek, Stanisław; Venkateshaiah, Abhilash; Krawczyk, Kamil; Sobel, Bartłomiej; Padil, Vinod V.T.; Černík, Miroslav; Varma, Rajender S.This work describes an eco-friendly and sustainable technique for the synthesis of silver nanoparticles (nAg), where chitosan-poly(3-hydroxybutyrate) polymer conjugate (Chit-PHB) acts as a reducing and stabilizing material. The ensuing nanoparticles show an exceptional catalytic activity in the reduction of 4-nitrophenol to 4-aminophenol. nAg were characterized by several techniques, i.e. SEM and TEM-EDX, to confirm their production, size and morphology. Furthermore, infrared spectroscopy analysis proved the presence of a Chit-PHB coating on the nAg. The excellent catalytic properties of the nAg-Chit-PHB was discernible when the activity parameter (κc) normalized by the specific surface area (SSA) of the nanoparticles was taken into consideration; normalization of κc by the SSA is a vital parameter for the assessment of the accessibility to the surface area of particles. Herein synthesized Ag nanoparticles, as far as we know, exhibited the fastest reaction kinetics of 4-nitrophenol reduction compared to the silver nanoparticles reported in the literature
- ItemUV-Catalyzed Persulfate Oxidation of an Anthraquinone Based Dye(MDPI, 2020-01-01) Krawczyk,Kamil; Wacławek, Stanisław; Kudlek, Edyta; Silvestri, Daniele; Kukulski, Tomasz; Grübel, Klaudiusz; Padil, Vinod V. T.; Černík, MiroslavWastewater from the textile industry has a substantial impact on water quality. Synthetic dyes used in the textile production process are often discharged into water bodies as residues. Highly colored wastewater causes various of problems for the aquatic environment such as: reducing light penetration, inhibiting photosynthesis and being toxic to certain organisms. Since most dyes are resistant to biodegradation and are not completely removed by conventional methods (adsorption, coagulation-flocculation, activated sludge, membrane filtration) they persist in the environment. Advanced oxidation processes (AOPs) based on hydrogen peroxide (H2O2) have been proven to decolorize only some of the dyes from wastewater by photocatalysis. In this article, we compared two very different photocatalytic systems (UV/peroxydisulfate and UV/H2O2). Photocatalyzed activation of peroxydisulfate (PDS) generated sulfate radicals (SO4•−), which reacted with the selected anthraquinone dye of concern, Acid Blue 129 (AB129). Various conditions, such as pH and concentration of PDS were applied, in order to obtain an effective decolorization effect, which was significantly better than in the case of hydroxyl radicals. The kinetics of the reaction followed a pseudo-first order model. The main reaction pathway was also proposed based on quantum chemical analysis. Moreover, the toxicity of the solution after treatment was evaluated using Daphnia magna and Lemna minor, and was found to be significantly lower compared to the toxicity of the initial dye.