REVIEW | doi:10.20944/preprints202301.0330.v1
Subject: Materials Science, Nanotechnology Keywords: applications; biogenic; environment; remediation; silver; soil
Online: 18 January 2023 (09:17:08 CET)
The invention of nanoscience not only brings a revolutionary change in the field of science but also changed the direction of research. Today the whole world is under the trigger of nano and nanoparticles have multidimensional applications in every aspect of life including environmental point of view. Till today a plethora of nanoparticles have been synthesized and have also been applied for multiple purposes and hence grabbed the attention of researchers all over the world. Among the bunch of NPs discovered to date, we have a particular interest in silver nanoparticles (AgNPs) because of their cost-effectiveness and huge abundance in the earth’s crust. With respect to every passing day, due to various kinds of anthropological activities, the quality of the environment such as air, water and soil is depleting which ultimately hampers the human civilization. To encompass the growing environmental issues, many techniques have been adopted. Among the many strategies, tackling the current issues regarding environment through nanoscience is highly worthy as because of its cost-effectiveness, less time consuming and easy handling process. This article reviews the potential of nanoparticles, particularly silver nanoparticles, for a wide range of environmental applications, such as soil, air, and water remediation.
ARTICLE | doi:10.20944/preprints201810.0730.v1
Online: 30 October 2018 (20:35:07 CET)
The BIOTON® biochar, produced by a wood biomass pyrolysis process, usually applied as a soil amendment, was investigated for a novel application, i.e. the adsorption of lead from contaminated solutions. The experimental activity firstly included the physical-chemical characterization of BIOTON®; SEM images were also obtained to highlight its internal structure. The adsorption process was investigated through batch and column experiments. Adsorption kinetics showed a very rapid achievement of the equilibrium conditions, i.e. at 2h and 4h for 50 mg/L and 100 mg/L initial Pb concentration, respectively. Complete removal also occurred within the same time. The Brunauer–Emmett–Teller model better fitted the equilibrium data for both Pb concentrations, whereas the kinetics were best represented by the pseudo second order model. The column tests showed that the addition of biochar as adsorbent media within the bed significantly extended the time of breakthrough and exhaustion, with respect to the column filled with soil only. The adsorption capacities of BIOTON® versus lead solutions was found to be comparable to that reported for commercial adsorbents. Therefore, BIOTON® can be considered a valid option, with the additional benefit to reduce the environmental impact since allows to recover a residue which alternately would need to be disposed of.
REVIEW | doi:10.20944/preprints202207.0010.v3
Subject: Engineering, Other Keywords: beneficiation; slag; flotation; construction material; soil remediation
Online: 12 August 2022 (06:20:08 CEST)
Mining is an important industry, accounting for 6.9% of global GDP. However, global development promotes accelerated demand, resulting in the accumulation of hazardous waste in land, sea, and air environments. It reached 7 billion tonnes of mine tailings generated yearly worldwide, and 19 billion solid tailings will be accumulated by 2025. Adding to this, the legacy of environmental damage from abandoned mines is worrying; in Canada there are around 10,000 abandoned mines, 50,000 in Australia, 6,000 in South Africa, and 9,500 coal mines in China, reaching 15,000 by 2050. In this scenario, restoration techniques from mining tailing have become increasingly discussed among scholars due to their potential to offer benefits towards reducing tailings levels, thereby reducing environmental pressure for the correct management and adding value to previously discarded waste. This review paper explores available literature on the main techniques of mining tailing recycling and reuse and discusses leading technologies, including the benefits and limitations, as well as emerging prospects. The findings of this review serve as a supporting reference for decision-makers concerning the related sustainability issues associated with mining, mineral processing, and solid waste management.
ARTICLE | doi:10.20944/preprints201705.0112.v1
Subject: Chemistry, Physical Chemistry Keywords: adsorption; magadiite; cationic clay; methylene blue; remediation
Online: 15 May 2017 (12:14:05 CEST)
The removal of methylene blue (MB) dye from water was investigated using synthetic nano-clay magadiite (SNCM). SNCM was synthesized by hydrothermal treatment under autogenous pressure. A rosette-shaped single mesoporous magadiite phase with 16.63 nm average crystallite size and 33 m2.g-1 BET-surface area was recorded. The adsorption results indicated the pronounced affinity of the SNCM to the MB dye molecules which reached adsorption uptake of 20.0 mg MB dye/g of SNCM. The elimination of MB dye by the SNCM was kinetically and thermodynamically considered; a pseudo second order kinetic model was attained, and a spontaneous, chemical, and exothermic in nature was verified.
ARTICLE | doi:10.20944/preprints201903.0106.v1
Subject: Physical Sciences, Other Keywords: sterile aggregates; remediation of waste water; peat; biochar
Online: 8 March 2019 (08:57:21 CET)
This paper investigates an alternative use of sterile aggregate materials which may arise from various construction applications in conjunction with other low-cost mineral raw materials to remediate the acid mine drainage phenomenon. This study is based on the combination of unprocessed mineral raw materials as well as on the basic concept of the cyclic economy where the conversion of a waste into a raw material for another application can be achieved. In this way, the value of mineral raw materials can be prolonged for as long as possible, waste generation and exploitation of natural resources are minimized and resources are kept as far as possible within the existing economy. In this study, an electrically continuous flow driven forced device proposed and demonstrated for the remediation of waste water in lab-scale by using certain mixes of mineral raw materials (serpentinite, andesite, magnesite, peat and biochar). Our results focus on the impact of the studied mineral raw materials and especially on their synergy on the water purification potential under continuous water flow operation. Using the proposed 7-day experimental electrically continuous flow driven forced device with the certain mixes of mineral raw materials, the increase of pH values from 3.00 to 6.82 as well as significant removal of Fe, Cu and Zn was achieved.
REVIEW | doi:10.20944/preprints201701.0006.v1
Subject: Engineering, Other Keywords: Fluoride, groundwater, in-situ remediation, pump and treat
Online: 2 January 2017 (13:57:12 CET)
A wide variety of pump and treat methods like chemical precipitation, adsorption, ion exchange and reverse osmosis have been trialled for many decades for fluoride removal from groundwater, but the problem of fluoride contaminated water remains in many parts of the world largely because these processes require constant monitoring, are expensive to implement and maintain at decentralised scale due to lack of reticulation infrastructure, and possess sludge disposal problem. This paper presents an overview of various fluoride removal processes and the limitations associated with each process and the application of in-situ permeable reactive barrier for remediating fluoride contaminated groundwater is explored, which displays the potential to be a cost effective, low maintenance and energy intensive technology.
ARTICLE | doi:10.20944/preprints202007.0236.v1
Subject: Chemistry, Other Keywords: trace metals; mine drainage remediation; zinc; red media; biochar
Online: 11 July 2020 (09:36:40 CEST)
The river Teign in Devon has come under scrutiny for failing to meet Environmental Quality Standards for ecotoxic metals due to past mining operations. A disused mine known as Bridford Barytes mine, has been found to contribute a significant source of Zn, Cd and Pb to the river. Recently, studies have been focused on the remediation of such mine sites using low-cost treatment methods to help reduce metal loads to the river downstream. Red mud is a waste product from the aluminium industry, the utilization of this resource has proven an attractive low-cost treatment method for adsorbing toxic metals. Adsorption kinetics and capacity experiments reveal metal removal efficiencies of up to 70% within the first 2 hours when red mud is applied in pelletized form. Biochar is another effective adsorbent with the potential to remove >90% Zn using agricultural feedstock. Compliance of the Teign has been investigated by analysing dissolved metal concentrations and bioavailable fractions of Zn to assess if levels are of environmental concern. By applying a Real-World Application Model, this study reveals that compressed pellets and agricultural biochar offer an effective, low-cost option to reducing metal concentrations and thus improving the quality of the river Teign.
Subject: Engineering, Other Keywords: bioelectrochemical systems; in situ treatment; groundwater remediation; bioelectroremediation; denitrification; microbial electrochemical technologies
Online: 17 January 2020 (11:08:18 CET)
Groundwater contamination is an ever-growing environmental issue that has attracted much and undiminished attention for the past half century. Groundwater contamination may originate from both anthropogenic (e.g., hydrocarbons) and natural compounds (e.g., nitrate and arsenic); to tackle the removal of these contaminants, different technologies have been developed and implemented. Recently, bioelectrochemical systems (BES) have emerged as a potential treatment for groundwater contamination, with reported in situ applications that showed promising results. Nitrate and hydrocarbons (toluene, phenanthrene, benzene, BTEX and light PAHs) have been successfully removed, due to the interaction of microbial metabolism with poised electrodes, in addition to physical migration due to the electric field generated in a BES. The selection of proper BESs relies on several factors and problems, such as the complexity of groundwater and subsoil environment, scale-up issues, and energy requirements that need to be accounted for. Modeling efforts could help predict case scenarios and select a proper design and approach, while BES-based biosensing could help monitoring remediation processes. In this review, we critically analyze in situ BES applications for groundwater remediation, focusing in particular on different proposed setups, and we identify and discuss the existing research gaps in the field.
ARTICLE | doi:10.20944/preprints201907.0077.v1
Subject: Biology, Horticulture Keywords: compost; compost quality; soil remediation; urban soil; nutrient leaching
Online: 4 July 2019 (11:36:40 CEST)
Poor soil health is a critical problem in many urban landscapes. Degraded soil restricts plant growth and microorganism activity, limiting the ability of urban landscapes to perform much needed ecosystem services. Incorporation of approximately 33% compost by volume into degraded soil has been proven to improve soil health and structure over time while avoiding the financial and environmental costs of importing soil mixes from elsewhere. However, additions of high volumes of compost could potentially increase the risk of nutrient loss through leaching and runoff. The objective of our study was to consider the effects of different compost amendments on soil health, plant health and susceptibility to nutrient leaching in order to identify ranges of acceptable compost characteristics that could be used for soil remediation in the urban landscape. We conducted a bioassay with Phaseolus vulgaris (Bush Bean) to measure the effect of nine composts from different feedstocks on various plant health parameters. We collected leachate prior to planting to measure nutrient loss from each treatment. We found that all compost amendments improved soil health. Nutrient-rich, manure-based composts produced the greatest plant growth, but also leached high concentrations of nitrate and phosphorus. Some treatments provided sufficient nutrients for plant growth without excess nutrient loss. We concluded, when incorporating as much as 33% compost by volume into a landscape bed, the optimal compost will generally have a C:N ratio of 10-20, P-content <1.0% and a soluble salt content between 1.0 and 3.5 mmhos/cm. These recommendations should ensure optimal plant and soil health and minimize nutrient leaching.
ARTICLE | doi:10.20944/preprints201703.0032.v1
Subject: Chemistry, Applied Chemistry Keywords: organic pollutants; enzymatic remediation; sulforhodamine B; soybean peroxidase; chloroperoxidase
Online: 6 March 2017 (07:45:32 CET)
Enzymatic degradation of organic pollutants is a new and promising remediation approach. Peroxidases are one of the most commonly used classes of enzymes to degrade organic pollutants. However, it is generally assumed that all peroxidases behave similarly and produce similar degradation products. In this study, we conducted detailed studies of the degradation of a model aromatic pollutant, Sulforhodamine B dye (SRB dye), using two peroxidases—soybean peroxidase (SBP) and chloroperoxidase (CPO). Our results show that these two related enzymes had different optimum conditions (pH, temperature, H2O2 concentration...etc.) for efficiently degrading SRB dye. High-performance liquid chromatography and LC-mass spectrometry analyses confirmed that both SBP and CPO transformed the SRB dye into low molecular weight intermediates. While most of the intermediates produced by the two enzymes were the same, the CPO treatment produced at least one different intermediate. Furthermore, toxicological evaluation using lettuce (Lactuca sativa) seeds demonstrated that the SBP-based treatment was able to eliminate the phytotoxicity of SRB dye, but the CPO-based treatment did not. Our results show, for the first time, that while both of these related enzymes can be used to efficiently degrade organic pollutants, they have different optimum reaction conditions and may not be equally efficient in detoxification of organic pollutants.
ARTICLE | doi:10.20944/preprints202301.0002.v1
Subject: Materials Science, Other Keywords: Graphene; copper oxide nanoparticles; nanohybrid; trichloroethylene; Rhodamine B; water remediation.
Online: 3 January 2023 (04:30:54 CET)
In this work Cu2O nanoparticles (NPs) were created in-situ on graphene functionalized with Thermomyces lanuginosus lipase (G@TLL) where site-oriented supported TLL acted as template and binder in the presence of copper salt by tailorable synthesis under mild conditions, producing a heterogeneous catalyst. Cu2O NPs was confirmed by XRD and XPS. The TEM microscopy showed that the nanoparticles were homogeneously distributed over the G@TLL surface with sizes of 53 nm and 165nm. This G@TLL-Cu2O hybrid was successfully used in the degradation of toxic organic compounds such as trichloroethylene (TCE) and Rhodamine B (RhB). In the case of TCE, the hybrid presented a high catalytic capacity, degrading 60 ppm of product in 60 min in aqueous solution and room temperature without the formation of other toxic subproducts. In addition, a TOF value of 7.5 times higher than the unsupported counterpart (TLL-Cu2O) was obtained, demonstrating the improved catalytic efficiency of the system in the solid-phase. The hybrid also presented an excellent catalytic performance for the degradation of Rhodamine B (RhB) obtaining a complete degradation (48ppm) in 50 min in in aqueous solution and room temperature and with the presence of a green oxidant as H2O2.
ARTICLE | doi:10.20944/preprints202111.0149.v1
Subject: Chemistry, Applied Chemistry Keywords: Alginate; polyvinyl alcohol; bentonite clay; nanocomposites hydrogel; cationic dyes; water remediation.
Online: 8 November 2021 (14:30:34 CET)
Hazardous chemicals like toxic organic dyes are very harmful to the environment and their removal is quite challenging. Therefore there is a necessity to develop techniques, which are environment friendly, cost-effective and easily available in nature for water purification and re-mediation. The present research work is focused on the development` and characterization of the ecofriendly polyvinyl alcohol (PVA) and alginate (Alg) hydrogel beads incorporating natural bentonite (Bent) clay as beneficial adsorbents for removal of toxic methylene blue (MB) from industrial water. PVA−Alg/Bent nanocomposite hydrogel beads with different Bent content (0, 10, 20, and 30 wt%) were synthesized via external ionic gelation method. The designed porous and steady structure beads were characterized by the use of Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM). The performance of the beads as MB adsorbents was investigated by treating batch aqueous solutions. The experimental results indicated that the incorporation of Bent (30 w%) in the nanocomposite formulation sustained porous structure, preserved water uptake, and increased MB removal effi-ciency by 230 % compared to empty beads. Designed beads possessed higher aﬃnity to MB at high pH 8, 30 °C, and ﬁtted well to pseudo-second-order kinetic model a high correlation coeﬃcient. Moreover, designed beads had a good stability and reusability as they exhibited excellent removal eﬃciency (90%) after six consecutive adsorption-desorption cycles. Adsorption process was found be combination of both monolayer adsorption on homogeneous surface and multilayer adsorption on heterogeneous surface. The maximum adsorption capacity of the designed beads system as calculated by Langmuir isotherm was found to be 51.34 mg/g, which is in good agreement with the reported clay-related adsorbents. The designed PVA−Alg/Bent nanocomposite hydrogel beads demonstrated good adsorbent properties and could be potentially used for MB removal from polluted water.
ARTICLE | doi:10.20944/preprints202009.0447.v1
Subject: Materials Science, Nanotechnology Keywords: nano- and micro-sized TiO2; photocatalytic efficiency; photoelectrochemical characterization; environmental remediation
Online: 19 September 2020 (05:11:43 CEST)
The size of TiO2 (either nanometric or micrometric) can significantly affect both its photocatalytic and photoelectrochemical properties, thus altering the photooxidation of organic pollutants in air or water. The purpose of this work is to give an account of the photoelectrochemical and photocatalytic features of some nano- and micro-sized TiO2 commercial powders towards a model reaction, the photooxidation of acetone. Cyclic voltammograms (CV) of TiO2 particulated electrodes under UV illumination experiments were carried out in either saturated O2 or N2 solutions for a direct correlation with the photocatalytic process. In addition, the effect of different reaction conditions on the photocatalytic efficiency under UV light in both aqueous and gaseous phases was also investigated. CV curves with the addition of acetone under UV light showed a negative shift of the photocurrent onset, confirming the efficient transfer of photoproduced reactive oxygen species (ROSs), e.g., hydroxyl radicals, or holes to acetone molecules. The photocatalytic experiments showed that the two nano-sized samples exhibit the best photocatalytic performance. The different photoactivity of the micro-sized samples is probably attributed to their morphological differences, affecting both the amount and distribution of free ROSs involved in the photooxidation reaction.
ARTICLE | doi:10.20944/preprints201810.0044.v1
Subject: Keywords: environmental impact assessment, remediation, petroleum-contaminated sites, environment, health, capacity building
Online: 3 October 2018 (12:01:44 CEST)
Human-generated, natural occurrences and other actions connected with the petroleum industry have contributed expansively to the contamination of numerous areas of human habitant, thus effecting overwhelming challenges and constraints to sustainable human health, development and the biosphere. The sites commonly associated include derelict pits, hydrocarbon onshore release sites, and places to where oil slicks exuding from offshore releases are blown onshore. In diverse cases, remediation is pertinent to restore the affected ambient. This is required despite the complexity and intricate pore structure and fluid trafficking trajectories of soil which are not easily amenable to remediation. Due to the complex assemblage of contaminated soil, it is necessary to conduct an encompassing site assessment by considering the potential impact of the environment and human health prior to proper selecting and implementing of a desirable remediation process. There are extant remediation methodologies which are effective and efficient for the clean up of contaminated shorelines and other petroleum-contaminated sites involving inter alia agricultural activities. There are salient variations in the techniques to expunge contaminants regarding spatiotemporal and pecuniary costs or considerations due to the gross environmental hazards entailed. This study provides for the opportunity to harness and sustain the capacity for the mitigation of untoward impacts, and induce the latitude for an enabling condition in sustainable human health, environment and development in the petroleum industry and other anthropogenic activities.
ARTICLE | doi:10.20944/preprints202301.0082.v2
Subject: Social Sciences, Education Studies Keywords: at-risk readers; elementary reading; reading remediation; orthographic mapping; reading fluency; reading comprehension; accelerated learning
Online: 6 January 2023 (09:39:03 CET)
Reading proficiency is requisite in our read-to-learn educational system, yet two-thirds of American students are not proficient readers. Assuring educational equity means supporting all learners with multiple component reading interventions that individually scaffold students while remediating weak literacy skills and providing intensive and sustainable intervention early. This study (N = 855) measured the efficacy of two different multiple component reading programs for students in grades three, four, and five. Grade levels of students were assigned to either the treatment intervention or the typical practice condition; and all students were pre-and post-tested using EasyCBM Reading Benchmarks. Students scoring at/below the 30th percentile on either benchmark were also assessed with the WRMT-3 Passage Reading Comprehension and Oral Reading Fluency measures. Students in the treatment condition received Readable English and students in typical practice condition continued to receive Amplify CKLA during their regular ELA times for 45—60 hours. Students receiving Readable English significantly outperformed students in the typical practice condition on measures of oral reading fluency, reading rate, accuracy, and passage comprehension. Raw scores, growth scale values, and grade equivalents are reported, and implications for practice are discussed. In a school year fraught with pandemic instructional interruptions and learning loss, elementary students in the intervention condition averaged a year’s worth of growth in reading fluency and nine months of growth in reading comprehension compared to three- and five-months fluency and comprehension growth in the typical practice condition. Students in the Readable English condition experienced meaningful gains in reading rate and accuracy that will give exponential word reading volume dividends to students able to read text faster and more accurately going forward. This study adds to accumulating evidence that multiple component reading programs designed to reinforce fluency skills also support reading comprehension gains for all students.
REVIEW | doi:10.20944/preprints202105.0257.v1
Subject: Life Sciences, Other Keywords: Schizophrenia, cognitive dysfunction, neural plasticity, inflammation, cognitive biomarker, pharmacological treatment, cognitive remediation, aerobic exercise, brain stimulation
Online: 12 May 2021 (07:26:36 CEST)
Pervasive and wide-ranging cognitive deficits are a core feature of schizophrenia and an important determinant of long-term functional outcome. The lack of sufficiently effective treatments for cognitive impairment associated with schizophrenia (CIAS) represents a major unmet need and a central roadblock towards recovery. This is partly due to the current therapeutic focus on clinical symptoms, and the relative neglect of cognitive impairments despite their functionally disabling effects. Furthermore, effective treatment is impeded by our limited knowledge of the complex pathophysiology, which gives rise to perturbed information processing. Here, we review mechanisms and effectiveness of available pharmacological and non-pharmacological treatments for CIAS. Current evidence indicates, that while techniques which broadly enhance neural plasticity show the greatest therapeutic potential, effect sizes are at best moderate. Among other reasons, this is due to a considerable heterogeneity of responses to individual interventions. Furthermore, we discuss how recent conceptual advances in operationalizing cognitive impairments based on cognitive neuroscience have the potential to address these issues and facilitate the development of novel treatment strategies for CIAS. This includes more clearly elucidating pathophysiological mechanisms in both humans and animal models, identifying new treatment targets as well as establishing biomarkers for a better prediction of treatment responses.
REVIEW | doi:10.20944/preprints201802.0070.v1
Subject: Earth Sciences, Environmental Sciences Keywords: microbial sulphide oxidation, corrosion, mine waste and water remediation, biofilm development, inhibition of Acid mine and rock draiange
Online: 8 February 2018 (15:35:56 CET)
Abstract: Measures to counteract AMD generation need to start at the mineral surface, inhibiting mineral-oxidizing, acidophilic microbes. Laboratory and long-term field tests with pyrite-containing mining wastes, where Carbonaceous Phosphate Mining Waste (CPMW) was added, resulted in low acidity, and near neutral drainage. The effect was reproducible, nd confirmed by several independent research groups. This was shown to involve an organic coating, likely a biofilm. The biofilm formation was confirmed when CPMW was added to lignite coal waste with an initial pH of 1. Forty five days after the addition, the coal waste was dominated by heterotrophic microorganisms in biofilms. A review of the scientific literature supports that CPMW has physical and chemical characteristics which are capable of inducing a strong inhibitory effect on sulphide oxidation by forming an organic coating over the mineral surface. CPMW characteristics appear to provide the cornerstone of a new technology for the reduction of sulphide oxidation in mine wastes. An hypothesis for testing this technology is presented which could result in an economical and sustainable approach to mine waste and water management.
ARTICLE | doi:10.20944/preprints201703.0073.v1
Subject: Earth Sciences, Environmental Sciences Keywords: gaseous elemental mercury; hg-mining areas; abbadia san salvatore; central italy; total and leached mercury; building material; remediation
Online: 14 March 2017 (07:57:35 CET)
Mercury has a strong environmental impact since both its organic and inorganic forms are toxic and it represents a pollutant of global concern. Liquid Hg is highly volatile and it can be released during natural and anthropogenic processes in the hydrosphere, biosphere and atmosphere. In this study the distribution of Gaseous Elemental Mercury (GEM) and the total and leached mercury concentrations on paints, plasters, roof tiles, concretes, metals, dust and wood structures were determined in the main buildings and structures of the former Hg-mining area of Abbadia San Salvatore (Siena, Central Italy). The mining complex (divided into 7 units) covers a surface of about 65 ha and contains mining structures and managers and workers buildings. In this work, nine surveys of GEM measurements were carried out from July 2011 to August 2015 for the buildings and structures located in the units 2, 3 and 6. Moreover, detailed measurements were performed in February, April, July, September and December 2016 in the edifices and mining structures of Unit 6. GEM concentrations showed a strong variability in terms of space and time mostly depending on the distance from the building hosting driers, furnaces and condensers and ambient temperature, respectively. In the Unit 2 surveys carried out in the hotter period (from June to September) showed GEM concentrations up to 27,500 ng m−3, while in the Unit 6 they were on average much higher and occasionally they saturated the GEM measurement device (>50,000 ng m−3). Concentrations of total (in mg kg−1) and leached (in μg L−1) mercury measured in different building materials (up to 46,580 mg kg−1 and 4,470 mg L−1 for total and leached mercury, respectively) showed for the same type of material highly variable values in dependence on the edifice or mining structure from which they were collected. The results obtained in this study are of relevant interest for the operational cleanings to be carried out during the reclamation activities.
REVIEW | doi:10.20944/preprints202212.0192.v1
Subject: Chemistry, Applied Chemistry Keywords: aerogels; environmental remediation; uranium adsorption; environmental water decontamination; adsorption thermodynamics and kinetics; extraordinary adsorption capacity; qmax values; competitive ions; material recycling; uranium recovery
Online: 12 December 2022 (04:06:36 CET)
Aerogel-based adsorbents present extraordinary sorption capacity for hexavalent uranium that can be as high as 8.8 mol kg–1 (2088 g kg–1). The adsorption data follow generally the Langmuir isotherm model and the kinetic data are better described by the pseudo-second-order kinetic model, which is associated with chemisorption. Evaluation of the thermodynamic data reveals that the adsorption is generally an endothermic, entropy-driven process (ΔHo, ΔSo > 0). Spectroscopic studies (e.g., FTIR, XPS) indicate that the adsorption is based on the formation of in-ner-sphere complexes between surface active moieties and the uranyl cation. Regeneration and uranium recovery by acidification and complexation using carbonate or chelating ligands (e.g., EDTA) have been found to be successful. The application of aerogel-based adsorbents to uranium removal from industrial processes and uranium-contaminated waste waters was also successful, assuming that these materials could be very attractive as adsorbents in water treatment and uranium recovery technologies. However, the selectivity of the studied materials towards hexavalent uranium is limited suggesting further development of aerogel materials which could be modified by surface derivatization with chelating agents (e.g., salophen, iminodiacetate) presenting high selectivity for uranyl moieties.
ARTICLE | doi:10.20944/preprints202009.0475.v1
Subject: Biology, Other Keywords: Nile tilapia; Oreochromis niloticus; liver; duckweed; Lemna minor; Cu; Zn; Glutathione Peroxidase; GPx; Glutathione-S-Transferase; GST; Superoxide dismutase; SOD; Catalase; CAT; remediation assessment
Online: 20 September 2020 (14:41:41 CEST)
A two-fold integrated research study was conducted; firstly, to understand effects of copper (Cu) and zinc (Zn) on the growth and oxidative stress in Nile tilapia, Oreochromis niloticus; secondly, to study the beneficial effects of the duckweed Lemna minor L. as a heavy metal remover from wastewater. Experiments were conducted in mesocosms with and without duckweed. Tilapia fingerlings were exposed to Cu (0.004 and 0.02 mg/L) and Zn (0.5 and 1.5 mg/L) and fish fed for four weeks. We evaluated the fish growth performance, the hepatic DNA structure using comet assay, the expression of antioxidative genes (superoxide dismutase, SOD; catalase, CAT; glutathione peroxidase, GPx and glutathione-S-transferase, GST) and GPx and GST enzymatic activity. The results showed that Zn exhibited more pronounced toxic effects than Cu. Low dose of Cu did not influence the growth whereas higher doses of Cu and Zn significantly reduced the growth rate of tilapia compared to control, but addition of duckweed prevented weight loss. Further, in the presence of a high dose of Cu and Zn, DNA damage decreased, antioxidant gene expressions and enzymatic activities increased. In conclusion, results suggest that duckweed and Nile tilapia can be suitable candidates in metal remediation wastewater assessment programs.