Chemical washing of contaminated soils and photocatalytic treatments of spent soil washing effluent

This dissertation has been addressed to study the reclamation of heavy metal contaminated soils by soil washing, and to investigate the feasibility of photocatalytic processes for the treatment of the spent soil washing solution (SSWS). Indeed, the collected SSWS, containing the extracted metals and chelating agents, represents one of the main drawbacks of the washing technique, as it has to be submitted to further treatments for a complete detoxification before being discharged into the environment. The soil washing using EDDS as chelating agent has been demonstrated to be an efficient soil remediation technique to remove Cu and Zn from real polluted soils. Only Cu and Zn present as exchangeable and reducible fractions have been extracted by EDDS. The intra-particle diffusion was the main rate controlling step in the extraction of heavy metals from the solid matrix. Different contributions have been found by applying the Weber and Morris intra-particle diffusion model due to the different roles of superficial and intra-particle diffusive processes. The diffusion coefficients of the Cu/EDDS and Zn/EDDS complexes in real contaminated soils have been estimated using simplified diffusive models. The simultaneous removal of EDDS and metals (Cu, Fe and Zn) from both synthetic solutions and real contaminated soil washing mixtures at neutral pH has been investigated to assess the possibility of applying TiO2 based photocatalytic processes for the treatment of SSWS and identify the sequence of photocatalytic processes required to optimally decontaminate the liquid wastes. The photocatalytic tests have demonstrated that the sequence of treatment constituted by two steps, TiO2-photocatalysis with oxygen followed by TiO2-sacrificial photocatalysis, is required to completely detoxify the SSWS. In particular, the results show that Fe and Zn are mainly removed by precipitation as insoluble hydroxides during the first step whereas the second step is necessary to reduce cupric ions to zero-valent Cu, which precipitates from the solution

Introduction: Greening Italian Science Fiction–New Approaches to a Deep-Rooted Genre

Science fiction's role as a medium for cognitive estrangement aligns closely with environmental concerns. This genre's practice of extrapolating future scenarios from the present intricately intertwines with the anticipation of outcomes arising from human-planet interactions. Science fiction's adeptness in crafting extraterrestrial ecosystems not only stimulates, but also enriches, reimaginings of our known world. Furthermore, the genre persistently confronts anthropocentrism by envisioning potential post-human or post-humanist realities. It achieves this through the depiction of non-human and even inorganic entities, exemplified by alien beings or amalgamations of animal and vegetal life, thereby granting agency to these diverse form

Phytoremediation of PAH- and Cu-Contaminated Soil by Cannabis sativa L.: Preliminary Experiments on a Laboratory Scale

This study proposes the phytoremediation of phenanthrene (PHE)-, pyrene (PYR)-, and copper (Cu)-contaminated soil by Cannabis sativa L. The experimental campaign was conducted in 300 mL volume pots over a 50 d period using different initial polycyclic aromatic hydrocarbon (PAH) concentrations, i.e., 100 (PC1), 200 (PC2), and 300 (PC3) mg ƩPAHs kg−1 dry weight of soil, while maintaining a constant Cu concentration of 350 mg∙kg−1. PHE and PYR removal was 93 and 61%, 98 and 48%, and 97 and 36% in PC1, PC2, and PC3, respectively, in the greenhouse condition. The highest Cu extraction amounted to 58 mg∙kg−1. In general, the growth of C. sativa L. under the PC1, PC2, and PC3 conditions decreased by approximately 25, 65, and 71% (dry biomass), respectively, compared to the uncontaminated control. The present study is aimed at highlighting the phytoremediation potential of C. sativa L. and providing the preliminary results necessary for future field-scale investigations

UV‐Solar Photocatalysis for the Simultaneous Removal of Arsenic and Mercury in Washing Solutions from Polluted Marine Sediments

An environmentally sustainable strategy has been developed for simultaneously removing arsenic and mercury from wastewater, potentially coming from washing of polluted marine sediments. Citric acid (CA), a biodegradable chelating agent, forms stable complexes with both metals, which can be extracted from contaminated sediments through ex situ sediment washing. A solar photocatalytic method has been developed to separate toxic metals from wastewater and degrade CA. Increasing the TiO2 photocatalyst load enhances arsenic adsorption under dark conditions. Total arsenic removal is achieved during photocatalytic decontamination using 1000 ppm of TiO2. Fe(III)–hydroxides formed in the presence of Fe(III) further adsorb arsenic. Nearly total arsenic removal is achieved even under seawater conditions and visible light irradiation only. The removal of arsenic in different oxidation states has been successfully demonstrated. The UV–vis/TiO2/CA photocatalytic system has also proven highly effective for mercury removal from wastewater. Although seawater conditions slightly slow the removal process, complete mercury removal is achieved even under visible light irradiation. Finally, a combined photocatalytic approach has been developed for the removal of both arsenic and mercury, achieving 100% removal within few minutes of light irradiation. The reaction mechanism has been depicted based on intermediates and reaction products detected during the photocatalytic process

Assessment of environmental parameters effect on potentially toxic elements mobility in foreshore sediments to support marine-coastal contamination prediction

Potentially toxic elements (PTEs) presence in marine sediments can significantly affect the environmental quality and negatively influence economy and recreational activities in related areas. Accordingly, contamination monitoring and control in the marine environment is a fundamental task. In this work, four PTEs behavior (i.e. As, Hg, Pb, and Zn) in sandy foreshore sediments (SFSs) was thoroughly investigated at different pH, redox potential and temperature conditions of the marine water. For all the tests, the released As was 2.7-6 times higher than its initial concentration in water. Nonetheless, final mass balances showed that preferential release in the liquid phase occurred for Pb and Hg (up to 10 % and 9.1 %, respectively). Moreover, final Zn and Hg content increase in SFSs labile fractions indicated their higher bioavailability after the tests. The obtained results outline an approach useful to predict the contaminants behavior in marine matrices and support environmental monitoring and preservation strategies

Soil washing optimization, recycling of the solution, and ecotoxicity assessment for the remediation of Pb-contaminated sites using EDDS

This paper presents the results of an experimental study aimed at investigating the applicability of ethylenediamine-N,N′-disuccinic acid (EDDS) as a washing solution for the remediation of Pb-contaminated soil. All aspects of the treatment are analyzed and optimized, including the reuse and the final disposal of the EDDS spent solution. Different molar concentrations of the washing solutions and the efficiencies of varying solid/liquid ratio are tested at different pH values. More than 90% of the mobile Pb fraction is removed in about 24 h at pH 6. Accordingly, soil toxicity strongly decreases as a consequence of the treatment. The regenerated solution exhibits a reduced, but not negligible, extractive capacity. The total extraction of Pb is approximately 50% of the initial value after one regeneration cycle, and almost 20% after a second regeneration cycle. Respirometric tests, conducted using an activated sludge sampled in a municipal wastewater treatment plant, indicate that the spent solutions are not biodegradable, but they do not exert any toxic effect on the biomass. On the contrary, tests on regenerated solutions displayed the same biodegradability as the fresh one

From waste to resource: Hydrogen generation and antimicrobial activity of Ag-based photocatalysts recovered from biomedical waste

Electrocardiogram (ECG) disposable electrodes contain a substantial amount of silver (Ag), which can be extracted and recycled. Most current methods for recovering Ag from waste are expensive and environmentally harmful. This study investigated a sustainable chemical process for extracting Ag from discarded medical electrodes using a simple Cu(II) solution under moderately acidic conditions. Using response surface methodology (RSM) based on a three-level, full-factorial design, the optimized extraction conditions were determined as pH = 4.78, T = 80°C, [Cu(II)]0 = 8.0 × 10−3 M, and [NaCl]0 = 3.72 M. Under these conditions, a process efficiency approaching 100 % was achieved. Moreover, the recovery of metallic silver exceeded 85 %, even when using real matrices. (i.e., discarded ECG electrodes). As a result, the Ag-containing leachate solutions were utilized to synthesize silver-based materials with varying Ag content. These materials demonstrated (i) excellent photocatalytic activity for hydrogen production in aqueous solutions containing organic compounds and (ii) significant antipathogenic properties. In summary, effective Ag/TiO2 photocatalytic materials with high efficiency for hydrogen production and antimicrobial activity were successfully prepared through a novel, sustainable, and cost-effective chemical recovery process of silver from discarded ECG electrodes

Bio-removal of Yttrium (III), Cerium (III), Europium (III) and Terbium (III) from single and quaternary aqueous solutions using the extremophile Galdieria sulphuraria (Galdieriaceae, Rhodophyta)

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 Galdieria sulphuraria 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 Galdieria sulphuraria 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

Galdieria sulphuraria ACUF427 Freeze-Dried Biomass as Novel Biosorbent for Rare Earth Elements

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