PAHs are largely spread in the aquatic environment, and the drawbacks of conventional remediation techniques as well as the expenditures for alternative disposal of polluted sediments lead to seek ...more effective, environmentally-friendly and sustainable approaches. Therefore, the present review shows a critical overview of the literature evaluated with VOSviewer, focusing on the problem of PAH-contaminated marine sediments and the knowledge of available remediation processes to shed light on what research and technology lack. This review supplies specific information about the key factors affecting biological, physical-chemical and thermal remediation techniques, and carefully examines the drawbacks associated with their employment for remediating PAH-polluted marine sediments by showing adequate alternatives. The technologies thoroughly discussed here are biostimulation, bioaugmentation, sediment washing, carbonaceous adsorbent addition and thermal desorption. The environmental and economic impacts associated with the application of the mentioned remediation technologies have been also taken into account. Finally, this review examines new research directions by showing future recommendations.
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•The main remediation techniques employed for PAH-contaminated sediments are reviewed.•Bioaugmentation and biostimulation represent a booster for bioremediation techniques.•Sediment washing is affected by the extracting agent, solid-to-liquid ratio and time.•The use of carbonaceous adsorbent in sediments is limited by sorbent recovery issues.•Thermal desorption-remediated sediments can alter plants and microbial communities.
This paper presents an innovative procedure for the recovery of SS-ethylenediamine-N,N′-disuccinic acid (EDDS) solution used for soil washing processes. The procedure is derived from that applied for ...the recovery of ethylenediamine-tetraacetic acid (EDTA), modifying and optimizing the choice of the chemical agents used for the protonation of the chelant, the exchange of the metals, and the final precipitation of the unwanted compounds.
To select the reagents and test the proposed approach, an experimental study was conducted on real EDDS spent solutions, obtained washing a Cu and Zn real contaminated soil. According to the results obtained, the precipitation ranges from 30% to more than 90% for both Cu and Zn, depending on the adopted reagent sequence, and on the molar ratio between the salt and the chelant contained in the spent solution. Data were in agreement with chemical equilibrium predicted in ideal conditions. The recovered solutions had a reduced ability to remove the contaminants when applied in a new soil washing cycle (15% less for Cu and 30% less for Zn) because of the high concentration of alkaline metal ions required for the precipitation. At the same time, they were more biodegradable compared to non-treated solutions, confirming that EDDS-metal chelates may represent a threat for biological wastewater processes.
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•Alkaline precipitation is successful in regenerating spent EDDS solutions.•EDDS biodegradability is higher in regenerated solutions than spent solutions.•Regenerated EDDS solutions are less effective in removing Zn and Cu.
The recycling and reuse of solid wastes can be considered important challenges for civil and environmental applications in the frame of a more sustainable model of development and the consumption of ...new resources and energy ...
This paper analyzes the effect of caesium (Cs) concentration on seed germination, seedling growth, root uptake, and leaf uptake of Lactuca sativa to understand the potential transfer of the metal ...from contaminated soil to humans through the food chain.
The results of germination experiments show that seed germination and seedling growth strongly depend on increasing Cs concentration, with a decrease in the number of germinated seeds compared to the control up to 13.6% and a reduction in seedling growth up to 10.3% at the highest Cs tested concentration (15 mM).
Uptake experiments indicate a low transfer of Cs from soil to leaves and roots of the plants, ranging between 0.06% and 2.2%. The transfer is found to be a not-monotone function of soil potassium (K) content, with highest values corresponding to 1–2 mM K2SO4. Increasing concentrations of K lead to lower translocation of Cs from roots to leaves. Values above the average amount applied (20 and 40 mM K2SO4) almost stop the translocation, suggesting the use of a high amount of K2SO4 protects the food chain from Cs contamination.
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•Number of germinated seeds (L. sativa) decreases exponentially increasing Cs amount.•The length of root and shoots of the seedlings is strongly reduced in presence of Cs.•At low-toxic Cs concentration the overall uptake operated by the plants is quite low.•High concentration of K minimizes Cs uptake by Lactuca sativa.•High concentration of K almost stops translocation of Cs from roots to leaves.
The study analyzes the presence and the origin of heavy metals in environmental compartments affected by anthropogenic activities. The paper presents the results of a field study performed on the ...sediments of two of the main small urban creeks of the city of Prague (Czech Republic). The aim of the survey was to verify the presence and bioavailability of heavy metals (Cu, Cr, Ni, Pb, Zn) in the aquatic environment (water as well as bottom sediments), and to assess the source of these pollutants. The results were processed to evaluate the enrichment factor and the partition coefficient, and were statistically analyzed through the analysis of variance and the principal component analysis. Comparison with relevant environmental quality standards showed that measured heavy metal concentrations were always lower than the probable effect concentration (PEC). On the contrary, the threshold effect concentration (TEC) was frequently exceeded. Sequential extraction analysis showed that the bioavailability of studied metals is quite high, suggesting that they could be easily released from the sediment to the aquatic environment. Overall, several sources of pollution, different for the different metals, were identified, all related with anthropogenic factors.
The lanthanides are among the rare earth elements (REEs), which are indispensable constituents of modern technologies and are often challenging to acquire from natural resources. The demand for REEs ...is so high that there is a clear need to develop efficient and environmentally-friendly recycling methods. In the present study, living cells of the extremophile
were used to remove four REEs, Yttrium, Cerium, Europium, and Terbium, from single- and quaternary-metal aqueous solutions. Two different strains, SAG 107.79 and ACUF 427, were exposed to solutions buffered at pH 2.5, 3.5, 4.5, and 5.5. Our data demonstrated that the removal performances were strain and pH dependent for all metal ions. At lower pH, ACUF 427 outperformed SAG 107.79 considerably. By increasing the pH of the solutions, there was a significant surge in the aqueous removal performance of both strains. The same trend was highlighted using quaternary-metal solutions, even if the quantities of metal removed were significantly lower. The present study provided the first insight into the comparative removal capacity of the
strains. The choice of the appropriate operational conditions such as the pH of the metal solutions is an essential step in developing efficient, rapid, and straightforward biological methods for recycling REEs.
Several studies have shown that combining TiO2 and Cu2O enhances the photocatalytic activity of the material by generating a heterojunction capable of extending the light absorption in the visible ...and reducing the electron-hole recombination rate. Ball milling has been chosen as an alternative methodology for photocatalyst preparation, among the several techniques documented in the literature review. The results of a previously reported investigation enabled the identification of the most effective photocatalyst that can be prepared for hydrogen generation by combining Cu2O and TiO2 (i.e., 1%wt. Cu2O in TiO2 photocatalyst prepared by ball-milling method at 200 rpm and 1 min milling time). To optimize photocatalytic hydrogen generation in the presence of the greatest photocatalyst, the effects of (i) sacrificial species and their concentration, (ii) temperature, and (iii) pH of the system are taken into account, resulting in a light-to-chemical energy efficiency of 8% under the best-tested conditions. Last but not least, the possibility of using the present photocatalytic system under direct solar light irradiation is evaluated: the results indicate that nearly 60% of the hydrogen production recorded under sunlight can be attributed to the visible component of the solar spectrum, while the remaining 40% can be attributed to the UV component.
A porous waste glass (RWPG = recycled waste porous glass) was used in wastewater treatments for the removal of lead ions from single, binary, and ternary metal solutions (with cadmium and nickel ...ions). Experiments were performed in columns (30 cm³, 10 g) filled with 0.5⁻1 mm beads till complete glass exhaustion (breakthrough). In the case of single and binary solutions, the columns were percolated at 0.2 Lh
(2 mg Me
L
); in the case of ternary solutions, the columns were percolated at 0.15⁻0.4 Lh
(2 mg Me
L
) and with 2⁻5 mg Me
L
influent concentration (0.2 Lh
). Lead ions were removed mainly by ion exchange and also by adsorption. From a kinetic point of view, the rate controlling step of the process was the interdiffusion of the lead ions in the Nernst stationary liquid film around the sorbent. The uptake of the metals and the glass selectivity were confirmed by Energy Dispersive X-ray spectroscopy (EDX) analysis. After lead retention process, glass beads were reused as lightweight aggregates for thermal insulating and environmental safe mortars.
Rare earth elements (REEs) are essential components of modern technologies and are often challenging to acquire from natural resources. The demand for REEs is so high that there is a clear need to ...develop efficient and environmentally-friendly recycling methods. In the present study, freeze-dried cells of the extremophile Galdieria sulphuraria were employed to recover yttrium, cerium, europium, and terbium from quaternary-metal aqueous solutions. The biosorption capacity of G. sulphuraria freeze-dried algal biomass was tested at different pHs, contact times, and biosorbent dosages. All rare earths were biosorbed in a more efficient way by the lowest dose of biosorbent, at pH 4.5, within 30 min; the highest removal rate of cerium was recorded at acidic pH (2.5) and after a longer contact time, i.e., 360 min. This study confirms the potential of freeze-dried cells of G. sulphuraria as innovative ecological biosorbents in technological applications for sustainable recycling of metals from e-waste and wastewater.
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