Implications For Environmental Remediation Research Articles

Mobility of Zn and Cu in Bentonites: Implications for Environmental Remediation.

The aim of this study was to evaluate the mobility of copper (Cu) and zinc (Zn) and their impact on the properties of bentonites and unfrozen water content. Limited research in this area necessitates further analysis to prevent the negative effects of metal interactions on bentonite effectiveness. Tests involved American (SWy-3, Stx-1b) and Slovak (BSvk) bentonite samples with Zn or Cu ion exchange. Sequential extraction was performed using the Community Bureau of Reference (BCR) method. Elemental content was analyzed via inductively coupled plasma optical emission spectrometry (ICP-OES). Unfrozen water content was measured using nuclear magnetic resonance (1H-NMR) and differential scanning calorimetry (DSC). Results showed a significant influence of the main cation (Zn or Cu) on ion mobility, with toxic metal concentrations increasing mobility and decreasing residual fractions. Mobile Zn fractions increased with larger particle diameters, lower clay content, and shorter interplanar spacing, while the opposite was observed for Cu. Zn likely accumulated in larger clay pores, while Cu was immobilized in the bentonite complex. The stability of Zn or Cu ions increased with higher clay content or specific surface area. Residual Zn or Cu fractions were highest in uncontaminated bentonites with higher unfrozen water content, suggesting the potential formation of concentrated solutions in sub-zero temperatures, posing a threat to the clay-water environment, especially in cold regions.

Photocatalytic Degradation of Lignin using TiO2 from Ilmenite Prepared by Microwave Method

This study investigates the photocatalytic degradation of lignin using TiO2 extracted from ilmenite through a microwave-assisted method. Characterization of the iron sand, which serves as the source of ilmenite, was conducted using X-ray fluorescence spectroscopy (XRF) and Energy Dispersive X-ray Spectroscopy (EDX). The XRF analysis revealed that the iron sand primarily consists of Fe and TiO2, with minor impurities such as Al2O3, MgO, and SiO2. After extraction, the iron mineral content increased significantly, while impurities decreased. EDX analysis confirmed the presence of Fe, O, and Ti elements in the iron sand sample, originating from various iron oxide phases. Subsequent degradation tests on lignin with varying microwave heating durations of ilmenite showed that a 90-minute heating duration achieved the highest lignin degradation percentage of 56.69%. This suggests that the optimum heating time for ilmenite is crucial for maximizing its photocatalytic activity. Overall, the findings highlight the potential of microwave-prepared TiO2 from ilmenite for efficient lignin degradation, with implications for environmental remediation and industrial applications.

Thorium speciation in ilmenite concentrates from the Mandena deposit, Madagascar: Implications for environmental remediation and thorium beneficiation

Placer ilmenite deposits are important sources for titanium dioxide production but are often radioactive due to elevated thorium and uranium contents, posing significant challenges to their upgrading and downstream commercial applications. In this contribution, we have investigated ilmenite concentrates containing 133 ppm Th and 12.8 ppm U from the Mandena deposit, Madagascar, using a wide range of analytical techniques: powder X-ray diffraction, electron microprobe analysis, quantitative evaluation of materials by scanning electron microscopy, inductively coupled plasma mass spectrometry, laser ablation inductively coupled plasma mass spectrometry, synchrotron X-ray absorption spectroscopy, microbeam synchrotron X-ray fluorescence mapping, and microbeam synchrotron Laue X-ray diffraction analysis. Our data show that monazite-(Ce), mainly as discrete grains, accounts for ∼55% of Th in the Mandena ilmenite concentrates. Thorianite hosting the remaining Th at ∼45% is revealed by synchrotron Th LIII edge X-ray absorption near-edge structure and extended X-ray absorption fine structure analyses and is correlated with the degree of ilmenite alteration. These results suggest that thorianite probably formed from the alteration of ilmenite and precipitated on the surface of altered ilmenite. The presence of monazite-(Ce) and thorianite in the Mandena ilmenite concentrates is further supported by principal component analysis of trace elements. Our results suggest that combined magnetic separation and acid leaching are effective for reducing the Th (and U) abundances in the Mandena ilmenite concentrates, via the removal of Th-bearing minerals. These findings have important implications for both Th remediation and beneficiation. Moreover, the precipitation of thorianite on the surface of altered ilmenite is an effective method for attenuating the common radionuclide Th in surficial environments.

The metabolic mechanisms of Cd-induced hormesis in photosynthetic microalgae, Chromochloris zofingiensis

Cadmium, an environmental pollutant, is highly toxic and resistant to degradation. It exhibits toxicity at elevated doses but triggers excitatory effects at low doses, a phenomenon referred to as hormesis. Microalgae, as primary producers in aquatic ecosystems, demonstrate hormesis induced by cadmium, though the specific mechanisms are not yet fully understood. Consequently, we examined the hormesis of cadmium in Chromochloris zofingiensis. A minimal Cd2+ concentration (0.05 mg L−1) prompted cell proliferation, whereas higher concentrations (2.50 mg L−1) inhibited growth. The group exposed to higher doses exhibited increased levels of reactive oxygen species (ROS), malondialdehyde (MDA), glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT). Contrastingly, the group exposed to low doses exhibited a moderate antioxidant response without significantly increasing ROS. This implies that increased levels of antioxidative components counteract excessive ROS, maintaining cellular redox balance and promoting growth under conditions of low Cd2+. Validation experiments have established that NADPH oxidase-derived ROS primarily coordinates the hormesis effect in microalgae. Comparative transcriptome analysis has proved the involvement of antioxidant systems and photosynthesis in regulating hormesis. Notably, Aurora A kinases consistently displayed varying expression levels across all Cd2+ treatments, and their role in microalgal hormesis was confirmed through validation with SNS-314 mesylate. This study unveils the intricate regulatory mechanisms of Cd-induced hormesis in C. zofingiensis, with implications for environmental remediation and industrial microalgae applications.

Detection and sorption of heavy metal ions in aqueous media using Zn-based luminescent metal-organic framework

In this study, we present the synthesis and comprehensive characterisation of a novel, luminescent Metal-Organic Framework (MOF) denoted as PUC7, derived from Zn(NO3)2·6H2O, 1,2-di(4-pyridyl)ethylene, and 2-amino-terephthalic acid through solvothermal method. The PUC7 was successfully characterised using many techniques, including single crystal X-ray diffraction, powder X-ray diffraction, FTIR spectroscopy, BET surface area analysis, FESEM imaging, XPS, UV–visible spectroscopy, and zeta potential measurements. Remarkably, PUC7 exhibited high luminescence properties and water stability. The luminescence properties were utilised for the detection of heavy metal ions. Consequently, PUC7 displayed exceptional selectivity and sensitivity towards W6+ and V5+, with impressively low detection limits of 0.17 μM and 0.22 μM, along with high quenching constant values of 2.5 × 105 M−1 and 1.1 × 105 M−1, respectively. Additionally, we explored PUC7′s proficiency in removing W6+ and V5+ ions from aqueous solution, revealing maximum adsorption efficiencies of 476.2 mg/g and 460.8 mg/g, respectively, fitting well with the Langmuir adsorption model and exhibiting second-order kinetics. Encouragingly, PUC7 demonstrated reusability for up to five cycles in removing W6+ and V5+ ions. Altogether, this research underscores the potential of PUC7 as a versatile and promising tool for efficiently detecting and removing W6+ and V5+ ions from water, with implications for environmental remediation and water purification applications.

Direct Z-scheme g-C3N4/TiO2 heterojunction porous nanotubes: An ingenious synthesis strategy to enhance photocatalytic activity

Photocatalysis has a broad prospect for generating H2 and reactive oxygen species. In this study, porous nanotubular g-C3N4/TiO2 photocatalysts were obtained via electrospinning combined with an innovative vapor deposition approach. The waste foam was used as the precursor material for TiO2 nanotubes, reducing production cost and benefiting resource recovery. The modification of g-C3N4 onto TiO2 nanotubes provided extensive active sites with an increased specific surface area and produced the heterojunction to improve charge separation. The g-C3N4/TiO2 nanotubes displayed remarkable photocatalytic effects in the degradation of organic dye with a removal efficiency of 93.4% and H2 evolution reaction performing at 4122 μmol·g−1·h−1 under simulated sunlight. Photocatalytic activation product analyses and density functional theory (DFT) calculations demonstrated a possible photogenerated carriers transfer pathway. This work provides a way to prepare multifunctional porous nanotubes using a facile synthesis method from abandoned resources with implications for environmental remediation and hydrogen generation.

Resuspension and settlement characteristics of lake sediments amended by phosphorus inactivating materials: Implications for environmental remediation

The classical lake internal phosphorus (P) pollution control using P-inactivating materials is typically carried out by reducing the release of soluble P from sediments to overlying water; however, particulate P loading through sediment resuspension could also cause internal P pollution for algae breeding. Therefore, based on lanthanum modified bentonite clay (Phoslock®) and drinking water treatment residues (DWTR), the effect of P inactivating materials on sediment resuspension and settlement were comprehensively investigated to assess the variations in particulate P pollution from sediment. Results showed that both materials could effectively control soluble P pollution from sediment, while both had limited effect on the supplement of particulate P to overlying water. The reason may be that hydrodynamic disturbance was the key factor regulating sediment resuspension and settlement. The disturbance induced the resuspension of different sized sediments, especially <8 μm fractions, while increasing disturbing intensities promoted resuspension of relatively larger sized sediments (e.g., <63 μm). Further analysis suggested that after resuspension and settlement, the efficiencies of reducing bioavailable P by Phoslock® in relatively large sized sediment fraction (e.g., <63 μm) were substantially less than those in relatively small sized sediment (<8 μm). Although the reducing efficacies of DWTR had limited changes in different sized sediments, the remaining bioavailable P were clearly higher in smaller sized sediments with DWTR. The different performances on bioavailable P reduction mainly resulted from the distributions of materials and original P in different sized sediments. These findings indicated the potential supplement of particulate P for algal growth during resuspension and settlement of sediments amended by P inactivating materials. Overall, understanding the sediment P bioavailability and hydraulic properties at different sizes and the lake hydrodynamic conditions is essential to develop appropriate methods to control lake internal P pollution.

Organic matter stabilized Fe in drinking water treatment residue with implications for environmental remediation

Fe-based materials used to adsorb P are commonly considered to be limited by the increased Fe lability, while Fe in drinking water treatment residue (DWTR) shows stable P adsorption abilities. Accordingly, this study aimed to gain insight into Fe lability in DWTR as compared to FeCl3 and Fe2(SO4)3 using Fe fractionation, EXAFS, and high-throughput sequencing technologies. The results showed that compared to Fe2(SO4)3 and FeCl3, Fe was relatively stable in the DWTR under the effects of organic matter, sulfides, and anaerobic conditions. Typically, the addition of FeCl3 and Fe2(SO4)3 enhanced Fe mobility in sediment and overlying water, promoting the formation of Fe-humin acid and ferrous sulfides (FeS and FeS2). However, the addition of DWTR, even at relatively high doses of Fe, has limited impact on Fe mobility. The addition remarkably increased oxidizable Fe in sediment (by approximately 63%), causing Fe to be dominated by oxidizable and residual fractions (like those in raw DWTR); EXAFS analysis also suggested that Fe-humin acid increased substantially with the addition of DWTR, becoming the main Fe species in sediment (with a relative abundance of 50.1%). Importantly, the Fe distributions were stable in sediment with DWTR added, which demonstrated that organic matter stabilized the Fe in the DWTR. Further analysis indicated that all materials promoted the enrichment of bacterial genera potentially related to Fe metabolism (e.g., Bacteroides, Dok59, and Methanosarcina). Fe2O3 in the FeCl3 and Fe2(SO4)3 groups and Fe-HA in the DWTR group were the key species affecting the microbial communities. Overall, the stabilizing effect of organic matter on Fe in DWTR could be used to develop Fe-based materials to enhance Fe stability for environmental remediation.

Probing molecular interactions between humic acid and surface-grafted polyacrylamide using quartz crystal microbalance with dissipation and atomic force microscopy: implications for environmental remediation

Environmental contextPolyacrylamide and its derivatives may enter the natural environment as a consequence of their wide use in various industrial applications. This study demonstrates the application of a quartz crystal microbalance and atomic force microscopy to study the molecular interactions between polyacrylamides and humic acids under various solution chemistries. The knowledge obtained can be used to understand and predict the environmental behaviour of polyacrylamides. AbstractA fundamental understanding of the environmental behaviour of polyacrylamide (PAM) is of importance for guiding environmental remediation. We create a framework for understanding the molecular interactions between PAM and a major constituent present in all natural waters and soil, humic acid (HA), using a quartz crystal microbalance with dissipation (QCM-D) and an atomic force microscope (AFM). A thin film of PAM was grafted on a silica surface silanised with 3-(trimethoxysilyl)propyl methacrylate and the resulting surface was characterised by X-ray photoelectron spectroscopy for the chemical bonds and composition, secondary ion mass spectrometry for the composition and molecular weight, water contact angle measurements for the hydrophilicity, AFM for the morphology, and ellipsometry for the thickness. Surface-grafted PAM was used to study its interactions with HA in aqueous solutions at different pH (2, 7, and 10) and NaCl salt concentrations (1, 10, and 100 mM, within the range of salt concentrations of fresh water) using QCM-D. QCM-D measurements showed that compared with bare silica, the adsorption of HA by PAM-coated silica was greatly reduced at all pHs and salt concentrations, and the adsorption of HA on PAM-coated silica depended on the solution chemistry including solution pH and salt concentration. Hydrogen bonding between PAM and HA is the major driving force for HA to adsorb on PAM. AFM force measurements showed that adhesion between PAM and HA was observed only at acidic conditions. The knowledge obtained from this study will benefit the prediction of the environmental behaviour of PAMs under different conditions in natural/engineered environments and provide guidance for the design of remediation technologies for water and soil.

Mycorrhizae: Implications for Environmental Remediation and Resource Conservation

ENH-1086, a 5-page fact sheet by J. Sharma, A.V. Ogram, and A. Al-Agely, describes the symbiotic relationships between plant roots and fungi and how the resulting rhizosphere activity can lead to transformation and removal of polluting compounds from the soil, reduce the need for fertilizer in commercial nurseries, and improve soil structure and health. Includes references. Published by the UF Department of Environmental Horticulture, November 2007.

Protection of mesopore-adsorbed organic matter from enzymatic degradation.

Synthetic mesoporous alumina and silica minerals with uniform pore geometries, and their nonporous analogues, were used to test the role of mineral mesopores (2-50 nm diameter) in protecting organic matter from enzymatic degradation in soils and sediments. Dihydroxyphenylalanine (L-DOPA), a model humic compound, was irreversibly sorbed to both mineral types. The surface area-normalized adsorption capacity was greater for the mesoporous minerals relative to their nonporous analogues. The degradation kinetics of free and mineral-sorbed L-DOPA by the enzyme laccase was monitored in a closed cell via oxygen electrode. Relative to freely dissolved L-DOPA, nonporous alumina-sorbed substrate was degraded, on average, 90% more slowly and to a lesser extent (93%), likely due to laccase adsorption to alumina. In contrast, relative to free L-DOPA, degradation of nonporous silica-sorbed L-DOPA was enhanced by 20% on average. In the case of mesoporous alumina and silica-sorbed L-DOPA, the enzyme activity was 3-40 times lower than that observed for externally sorbed substrate (i.e., L-DOPA sorbed to nonporous minerals). These results provide strong evidence to support the viability of the mesopore protection mechanism for sequestration and preservation of sedimentary organic matter and organic contaminants. Nanopore adsorption/desorption phenomena may aid in explaining the slow degradation of organic contaminants in certain soils and sediments and may have implications for environmental remediation and biotechnological applications.

Acid Sulfate Wetlands in the NSW Coast, Australia: Chemical Characteristics and Their Implications for Environmental Remediation

Acid Sulfate Wetlands in the NSW Coast, Australia: Chemical Characteristics and Their Implications for Environmental Remediation

Titania-based heterogeneous photocatalysis. Materials, mechanistic issues, and implications for environmental remediation

Abstract Using hexavalent chromium [Cr(VI)] and methylene blue (MB) as model substrates, we discuss three aspects of TiO2-based heterogeneous photocatalysis. We show first that a given TiO2 sample may not be simultaneously optimal for photocatalytically driving the reduction of Cr(VI) and the oxidation of MB. We further show that a TiO2 sample that strongly adsorbs either of these substrates in the dark is not optimal as a photocatalyst. The other two aspects concern circumventing the rather poor surface catalytic properties and visible light photoresponse of TiO2, respectively. Strategies revolving around the visible light photoexcitation of the substrate itself and metal-modification of the TiO2 surface, are described as possible solutions.

Great Lakes toxic sediments and climate change: Implications for environmental remediation

Toxic sediments remediation represents a potentially long-term environmental programme in the Great Lakes Basin. The prospect of declining take levels due to global climate change in coming decades presents challenges to environmental policy makers concerned with choosing appropriate toxics clean-up methods and timing. It is important to integrate the possibility of declining Iake levels into Great Lakes toxic sediments remediation in order to ensure that long-term environmental policy is not in conflict with the potential regional hydrological impacts of climate change.