Plant mediated synthesis of zero valent iron nanoparticles and its chracterisation

Nanoscale zero valent-iron (nZVI) particles represent an important material for diverse environmental applications because of the exceptional electron-donating properties, which can be exploited for applications such as reduction, catalysis, adsorption, and degradation of a broad range of pollutants. The search for “green” strategies leads to the advancement in the plantmediated synthesis of ZVI nanoparticles.Within the framework of this work, the possibility of synthesis of nano zerovalent iron (nZVI) was investigated using extracts of oak, mulberry, green tea, pomelo peel, fresh orange peel and orange peel that was previously dried. Also, the subject of the investigation was the characterization of the obtained nanomaterials

Leachability and Microstructural Analysis of Clay and Lime Stabilized/Solidified Polluted Sediment – Long-Term Performance

The objective of this study is to enable a better understanding of the effectiveness of solidification/stabilization (S/S) technique in treating polluted sediment, and provide the much needed validation of the longevity of the technology. In this research kaolinite and montmorillonite, with a certain proportion of lime, were used for S/S treatment of sediment polluted with metals. Leachability of metals was examined using the toxicity characteristic leaching procedure (TCLP) and the German standard leaching test (DIN 3841-4 S4) prescribed in national legislative. Results indicated successful S/S treatment using both clays and lime, from the aspect of all leached metals even with pH variations over time and slight changes in structural integrity of specimens. X-ray diffraction (XRD), scanning electron microscope (SEM) analyses and porosity measurement were also performed on the prepared monolithic matrices. XRD qualitative and semi-quantitative analysis proved hydration and pozzolanic product formation with increase in their content and finer crystallites formation over time. SEM analysis confirmed the presence of morphologically dense and stable structures while pore size distribution indicated on mesoporous matrices with ongoing compaction over time. Generally, structural microanalysis indicated the formation of hardened matrices over time and hydration process has been fully completed and further carbonation took place. Unconfined compressive strength measurement gave the satisfying results and matured monolite with 30 % of montmorillonite and 10 % of lime can be considered potentially applicable as non-load-bearing material. In summary, all results indicated that this kind of S/S treatment can achieve satisfactory durability and represent reliable and economically feasible technique for long-term remediation of metal polluted sediment

Assessing the possibility of solidification and stabilization of pyrite cinder by using quicklime and fly ash

The aim of this study was to determine the possibility of using two low-cost binders, quicklime and fly ash for the solidification/stabilization (S/S) of pyrite cinder. Pyrite cinder, used in this study, represents a remnant from sulfuric acid production in fertilizer factory IHP “Prahovo” A.D. (Serbia), and has a very high toxic metal content. High contents and leachability of copper, lead and zinc make this waste material hazardous, representing an extraordinary risk to the environment. In order to determine the leaching behavior of the S/S mixtures, four single-step leaching tests were performed, each one having a different sort of leaching fluid (deionized water, inorganic and organic acidic solutions). X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray analyzer (EDS) were implemented to elucidate the mechanisms responsible for immobilization of Cu, Pb and Zn. Overall, the test results indicated that S/S treatment using both quicklime and fly ash was effective in immobilizing these metals, especially when there is a higher share of binder present. Treated waste can be safe for disposal and even considered for “controlled utilization”. Furthermore, the use of fly ash for S/S treatment of pyrite cinder solves the disposal problems of two waste types, as it also represents a secondary industrial product

Assessing the possibility of solidification and stabilization of pyrite cinder by using quicklime and fly ash

The aim of this study was to determine the possibility of using two low-cost binders,quicklime and fly ash for the solidification/stabilization (S/S) of pyrite cinder.Pyrite cinder, used in this study, represents a remnant from sulfuric acid productionin fertilizer factory IHP “Prahovo” A.D. (Serbia), and has a very high toxicmetal content. High contents and leachability of copper, lead and zinc make thiswaste material hazardous, representing an extraordinary risk to the environment.In order to determine the leaching behavior of the S/S mixtures, four single-stepleaching tests were performed, each one having a different sort of leaching fluid(deionized water, inorganic and organic acidic solutions). X-ray diffraction (XRD),scanning electron microscope (SEM) and energy dispersive X-ray analyzer (EDS)were implemented to elucidate the mechanisms responsible for immobilization ofCu, Pb and Zn. Overall, the test results indicated that S/S treatment using bothquicklime and fly ash was effective in immobilizing these metals, especially whenthere is a higher share of binder present. Treated waste can be safe for disposal andeven considered for “controlled utilization”. Furthermore, the use of fly ash for S/Streatment of pyrite cinder solves the disposal problems of two waste types, as it alsorepresents a secondary industrial product

The beneficial reuse of contaminated sediment: Long-term assessment of fly ash and lime-based mixtures

In recent decades, sediment has been recognised as a problematic resource due to its potentially harmful effects and the large quantities present in water bodies. There is a need to properly manage large quantities of dredged sediments so that they can be used as a resource and not necessarily treated as a waste product. This research investigates the effects of ageing and maturation of solidified/stabilized mixtures of contaminated sediment with fly ash and lime. The effects of ageing on the microstructural properties and chemical integrity of mixtures were studied for 7 days, 28 days, and 7 years using scanning electron microscopy and energy dispersive spectroscopy (SEM/EDS), X-ray diffraction analysis (XRD), and DIN (German Standard Procedure for Water, Wastewater and Sediment Testing (Group S)) and TCLP (Toxicity Characteristic Leaching Procedure) leaching tests. The results of the microstructure and strength analysis showed that the use of fly ash and lime as binders promoted the permanent structural integrity of the sediment. The treated sediment with 20 wt% fly ash and 10 wt% lime (F20L10) achieved higher overall strength compared to the mixture containing only 30 wt% fly ash (F30). The speciation and redistribution of metals and As in the treated sediment mixtures during the long-term evaluation indicate a strong reduction in their mobility. This material can be considered environmentally friendly and can be used as a fill material in road construction. The investment and operating costs are justified in this solution for sediment management. However, it is important to monitor the produced material over time to ensure that it remains effective and sustainable in the long term

“Green” nZVI-Biochar as Fenton Catalyst: Perspective of Closing-the-Loop in Wastewater Treatment

In the framework of wastewater treatment plants, sewage sludge can be directed to biochar production, which when coupled with an external iron source has the potential to be used as a carbon–iron composite material for treating various organic pollutants in advanced oxidation processes. In this research, “green” synthesized nano zero-valent iron (nZVI) supported on sewage sludge-based biochar (BC)–nZVI-BC was used in the Fenton process for the degradation of the recalcitrant organic molecule. In this way, the circular economy principles were supported within wastewater treatment with immediate loop closing; unlike previous papers, where only the water treatment was assessed, the authors proposed a new approach to wastewater treatment, combining solutions for both water and sludge. The following phases were implemented: synthesis and characterization of nano zero-valent iron supported on sewage sludge-based biochar (nZVI-BC); optimization of organic pollutant removal (Reactive Blue 4 as the model pollutant) by nZVI-BC in the Fenton process, using a Definitive Screening Design (DSD) model; reuse of the obtained Fenton sludge, as an additional catalytic material, under previously optimized conditions; and assessment of the exhausted Fenton sludge’s ability to be used as a source of nutrients. nZVI-BC was used in the Fenton treatment for the degradation of Reactive Blue 4—a model substance containing a complex and stable anthraquinone structure. The DSD model proposes a high dye-removal efficiency of 95.02% under the following optimal conditions: [RB4] = 50 mg/L, [nZVI] = 200 mg/L, [H2O2] = 10 mM. pH correction was not performed (pH = 3.2). Afterwards, the remaining Fenton sludge, which was thermally treated (named FStreated), was applied as a heterogeneous catalyst under the same optimal conditions with a near-complete organic molecule degradation (99.56% ± 0.15). It could be clearly noticed that the cumulative amount of released nutrients significantly increased with the number of leaching experiments. The highest cumulative amounts of released K, Ca, Mg, Na, and P were therefore observed at the fifth leaching cycle (6.40, 1.66, 1.12, 0.62, 0.48 and 58.2 mg/g, respectively). According to the nutrient release and toxic metal content, FStreated proved to be viable for agricultural applications; these findings illustrated that the “green” synthesis of nZVI-BC not only provides innovative and efficient Fenton catalysts, but also constitutes a novel approach for the utilization of sewage sludge, supporting overall process sustainability

“Green” nZVI-Biochar as Fenton Catalyst: Perspective of Closing-the-Loop in Wastewater Treatment

In the framework of wastewater treatment plants, sewage sludge can be directed to biochar production, which when coupled with an external iron source has the potential to be used as a carbon–iron composite material for treating various organic pollutants in advanced oxidation processes. In this research, “green” synthesized nano zero-valent iron (nZVI) supported on sewage sludge-based biochar (BC)–nZVI-BC was used in the Fenton process for the degradation of the recalcitrant organic molecule. In this way, the circular economy principles were supported within wastewater treatment with immediate loop closing; unlike previous papers, where only the water treatment was assessed, the authors proposed a new approach to wastewater treatment, combining solutions for both water and sludge. The following phases were implemented: synthesis and characterization of nano zero-valent iron supported on sewage sludge-based biochar (nZVI-BC); optimization of organic pollutant removal (Reactive Blue 4 as the model pollutant) by nZVI-BC in the Fenton process, using a Definitive Screening Design (DSD) model; reuse of the obtained Fenton sludge, as an additional catalytic material, under previously optimized conditions; and assessment of the exhausted Fenton sludge’s ability to be used as a source of nutrients. nZVI-BC was used in the Fenton treatment for the degradation of Reactive Blue 4—a model substance containing a complex and stable anthraquinone structure. The DSD model proposes a high dye-removal efficiency of 95.02% under the following optimal conditions: [RB4] = 50 mg/L, [nZVI] = 200 mg/L, [H2O2] = 10 mM. pH correction was not performed (pH = 3.2). Afterwards, the remaining Fenton sludge, which was thermally treated (named FStreated), was applied as a heterogeneous catalyst under the same optimal conditions with a near-complete organic molecule degradation (99.56% ± 0.15). It could be clearly noticed that the cumulative amount of released nutrients significantly increased with the number of leaching experiments. The highest cumulative amounts of released K, Ca, Mg, Na, and P were therefore observed at the fifth leaching cycle (6.40, 1.66, 1.12, 0.62, 0.48 and 58.2 mg/g, respectively). According to the nutrient release and toxic metal content, FStreated proved to be viable for agricultural applications; these findings illustrated that the “green” synthesis of nZVI-BC not only provides innovative and efficient Fenton catalysts, but also constitutes a novel approach for the utilization of sewage sludge, supporting overall process sustainability

The Impact of Public Policy Measures during the COVID-19 Pandemic on the Characteristics of Urban Wastewater in the Republic of Serbia

The change in the way of life caused by the introduction of social restriction measures (closures, the restriction of working hours, and restriction of movement) by governments and thus, the resulting changes in people’s behavior, have affected all aspects of life, i.e., social activities, business, the environment and the performance of the infrastructure of the water supply system. Social distancing policies around the world in response to the pandemic have led to spatio-temporal variations in water consumption and therefore, to changes in the flow of wastewater, creating potential problems in the infrastructure, operation and quality of services. The goal of this work was to examine how these changes and how the pandemic itself affected the characteristics of municipal wastewater. Data on the quantity and quality of municipal wastewater in four settlements of different sizes in the Republic of Serbia in the period from 2015 to 2022 were collected. The data indicated an increase in the amount of wastewater generated in 2020, which may be a consequence of excessive water use. An increase in the mean concentrations of most parameters in 2020 compared to the previous five-year average was also observed. The most significant changes were observed concerning the concentrations of organic matter (2–124%), nitrogen (6–80%), phosphorus (14–91%), suspended matter (8–308%), fats and oils (97–218%) and surfactants (12–110%). Changes in terms of increasing concentrations were also noticed after the peak of the pandemic, i.e., in the period from 2021 to 2022. In addition, an increase in the COD/BOD ratio from around 2 to around 4 in the year 2020 was also observed (COD—Chemical Oxygen Demand; BOD—Biological Oxygen Demand). This is very important and should be taken into account in wastewater treatment procedures in order to achieve high efficiency in the operation of the plant itself

Removal of As(III) from Water Using “Green” Synthetized Zero Valent Iron in the Presence of Competing Phosphate Ions

Nanoscale zero valent iron (nZVI) has been widely investigated for treatment of environmental contaminants. Various technologies are currently available to remove As(III) and phosphate from aqueous environment, but among them, adsorption is most common because its simplicity, treatment stability and cost effectiveness. This study is focused on the removal efficiency of As(III) in the presence of competing phosphate ions by nZVI synthesized using polyphenols from oak and mulberry leaf extracts producing OAK-nZVI and M-nZVI, respectively. The highest removal efficiency of As(III) was obtained for M-nZVI (up to 91% at all nZVI doses). 87% removal was obtained for OAK-nZVI. The same conclusion could be retrieved in the case of PO43− removal (the highest removal, up to 78% at all nZVI doses for M-nZVI). Concerning OAK-nZVI, removal efficiencies increased with increasing nZVI doses (21–76% for doses 2–16 mL). Adsorption of As(III) in the presence of competing PO43− ions on M-nZVI, decreased from 91% to 79%. On OAK-nZVI material, significant changes could not be observed. One can conclude that the presence of PO43− ions in arsenic aqueous solutions would reduce effectiveness of the M-nZVI for As(III) remediation. This conclusion was supported by the fact that M-nZVI particles had a greater antioxidative capacity in comparison to OAK-nZVI which directly influenced nanoparticles synthesis and stability