Search Results (1,717)

This work compares two technologies for the remediation of metal-polluted mine tailings based on lab-scale bioleaching experiments performed in (a) conventional agitated slurry-phase reactors and (b) in situ electrokinetic percolation. While ex situ bioleaching in agitated reactors has been widely studied, only a few previous works have studied the in situ option that couples bioleaching and electrokinetics. Real mine tailings from an abandoned sphalerite mine in southern Spain were used. The leaching medium was externally generated in a bioreactor using an autochthonous acidophilic culture and then added to tailings in batch experiments. This medium enabled metal leaching from mine tailings without the stringent operating conditions required by a classic bioleaching process. Metal removal efficiencies and kinetic rate constants after 15 d of treatments were calculated. Additionally, advantages or disadvantages between the two methods were discussed. The results for the innovative EK-percolation method showed rates and efficiencies that were comparable to, and in some cases better than, those achieved with conventional stirred slurry systems. Full article

The escalating issue of phenol-containing wastewater necessitates the development of efficient and sustainable treatment methods. In this context, we present a novel composite photocatalyst comprising ZnFe₂O₄ (ZFO) nanoparticles supported on nanocellulose (NC), aimed at addressing this environmental challenge. The synthesis involved a facile hydrothermal method followed by the impregnation of ZFO nanoparticles onto the NC matrix. The morphology and structure of ZFO, NC, and ZFO/NC were investigated by TEM, SEM-EDX, UV–vis, FT-IR, XRD, and XPS analyses. ZFO, as a weakly magnetic semiconductor catalytic material, was utilized in photocatalytic experiments under magnetic field conditions. By controlling the electron spin states through the magnetic field, electron–hole recombination was suppressed, resulting in improved photocatalytic performance. The results demonstrated that 43% and 76% degradation was achieved after 120 min of irradiation due to ZFO and 0.5ZFO/NC treatment. Furthermore, the composite 0.5ZFO/NC demonstrated the highest photocatalytic efficiency, showing promising recyclability by maintaining its activity after three cycles of use. This study underscores the potential of the ZFO/NC composite for sustainable wastewater treatment, offering a promising avenue for environmental remediation. Full article

A highly versatile Z-scheme heterostructure, Ho₂SmSbO₇/YbDyBiNbO₇ (HYO), was synthesized using an ultrasonic-assisted solvent thermal method. The HYO heterojunction, composed of dual A₂B₂O₇ compounds, exhibits superior separation of photogenerated carriers due to its efficient Z-scheme mechanism. The synergistic properties of Ho₂SmSbO₇ and YbDyBiNbO₇, particularly the excellent visible light absorption, enable HYO to achieve exceptional photocatalytic performance in the degradation of fenitrothion (FNT). Specifically, HYO demonstrated an outstanding removal efficiency of 99.83% for FNT and a mineralization rate of 98.77% for total organic carbon (TOC) during the degradation process. Comparative analyses revealed that HYO significantly outperformed other photocatalysts, including Ho₂SmSbO₇, YbDyBiNbO₇, and N-doped TiO₂, achieving removal rates that were 1.10, 1.20, and 2.97 times higher for FNT, respectively. For TOC mineralization, HYO exhibited even greater enhancements, with rates 1.13, 1.26, and 3.37 times higher than those of the aforementioned catalysts. Additionally, the stability and durability of HYO were systematically evaluated, confirming its potential applicability in practical scenarios. Trapping experiments and electron paramagnetic resonance analyses were conducted to identify the active species generated by HYO, specifically hydroxyl radicals (•OH), superoxide anions (•O₂⁻), and holes (h⁺). This facilitated a comprehensive understanding of the degradation mechanisms and pathways associated with FNT. In conclusion, this study represents a substantial contribution to the advancement of efficient Z-scheme heterostructure and offers critical insights for the development of sustainable remediation approaches aimed at mitigating FNT contamination. Full article

In the present work, we achieved the fabrication of MgO-Fe₂O₃/γ-Al₂O₃ NCs using a deposition–coprecipitation process. XRD, TEM, and SEM with EDX, XPS, FTIR, and PL spectroscopy were applied to examine the physicochemical properties of the samples. XRD analysis confirmed the successful incorporation of γ-Al₂O₃, MgO, and Fe₂O₃ phases. TEM and SEM images indicate that the nanocomposites exhibited an agglomerated morphology with spherical shapes and particle sizes in the range of 6–12 nm. EDX and XPS spectra revealed a composition of MgO-Fe₂O₃/γ-Al₂O₃ NCs. FTIR spectra identified characteristic vibrational bands corresponding to the chemical bonds present in the samples, confirming their successful synthesis. PL analysis showed the reduced recombination rate of electron–hole pairs and enhanced charge separation efficiency, which are important factors for improved photocatalytic activity. Photocatalysis results show that the MgO-Fe₂O₃/γ-Al₂O₃ NCs exhibited significantly higher photocatalysis efficiencies of 87.5% for Rh B and 90.4% for MB after 140 min, compared to γ-Al₂O₃ NPs and Fe₂O₃/γ-Al₂O₃ NPs. In addition, prepared MgO-Fe₂O₃/γ-Al₂O₃ NCs demonstrated superior stability after six runs. Biochemical data showed that the MgO-Fe₂O₃/γ-Al₂O₃ NCs exhibited significant toxicity toward A549 cancer cells while displaying low toxicity toward IMR90 normal cells. The IC₅₀ values (µg/mL ± SD) for γ-Al₂O₃ NPs, Fe₂O₃/γ-Al₂O₃ NPs, and MgO-Fe₂O₃/γ-Al₂O₃ NCs were 16.54 ± 0.8 µg/mL, 14.75 ± 0.4 µg/mL, and 11.40 ± 0.6 µg/mL, respectively. These results suggest that the addition of Fe₂O₃ and MgO to γ-Al₂O₃ not only enhances photocatalytic activity but also improves biocompatibility and anticancer properties. This study highlights that the MgO-Fe₂O₃/γ-Al₂O₃ NCs warrant further exploration of their potential applications in environmental remediation and biomedicine. Full article

At present, contamination due to toxic metals is a global concern. The management of problems caused by heavy metals relies on stabilization/solidification, which is the most effective technique for the control of metal pollution in soil. This study examined the immobilization efficiency of various phosphate-based binders (Na₃PO₄, Na₂HPO₄, NaH₂PO₄), in addition to ordinary Portland cement (OPC), MgO, and CaO, for the stabilization of multi-metal-contaminated soils. Moreover, this study focused on the leachability of copper, nickel, zinc, lead, cadmium, and manganese (Cu, Ni, Zn, Pb, Cd, Mn, respectively) over different time periods and with different concentrations. Batch leaching experiments were conducted to determine the leaching ratios and percentages of the various metal concentrations, along with measuring the pH values of the leachates. Our results indicate that the use of OPC was validated due to its superior immobilization performance across all metals present in the soil, but particularly with regard to metals in high concentrations. This was due to the formation of stable hydroxides and the high pH values, which assisted in abating the metals’ solubility. Additionally, phosphate-based binders, despite being environmentally favorable, were found to be less effective, particularly for Pb and Cu, and the leaching results exceeded non-hazardous waste limits. MgO showed reasonable immobilization results but was less effective compared to OPC; on the other hand, CaO exhibited increased leaching over time. Therefore, the present research serves primarily to highlight that OPC is more suitable for soil remediation at industrial sites and in the construction of infrastructure. Meanwhile, phosphate-based binders are shown to be more appropriate for eco-friendly, non-load-bearing applications. Full article

The management of swine wastewater (SW) presents significant environmental challenges, requiring solutions that combine effective treatment with resource recovery. This study highlights the dual role of microalgae in wastewater remediation and bioenergy production. H. rubescens KNUA214 was cultivated in media containing varying concentrations of diluted swine wastewater (DSW; 0%, 25%, 50%, and 100%). Cultivating with Blue Green-11 (BG-11) medium + 50% DSW maximized biomass growth, the chlorophyll content, and carotenoid production. Nutrient removal efficiency in 100% DSW over 8 days demonstrated reductions of 59.3% in total nitrogen, 67.7% in ammonia nitrogen, and 40.7% in total phosphorus, confirming the species’ capacity for effective wastewater treatment. The carotenoid analysis using HPLC revealed that astaxanthin, lutein, canthaxanthin, and beta-carotene exhibited the highest levels in BG-11 + 50% DSW. Furthermore, the biomass analyses confirmed its potential for bioenergy applications, with high calorific values and significant polyunsaturated fatty acid concentrations, enhancing its utility for bioenergy and biolubricant production. These findings position H. rubescens KNUA214 as an effective resource for integrating SW management with the sustainable production of high-value biochemicals, offering environmental and economic benefits. Full article

With the development of industry, agriculture, and aquaculture, excessive ammonia nitrogen mainly involving ionic ammonia (NH₄⁺) and molecular ammonia (NH₃) has inevitable access to the aquatic environment, posing a severe threat to water safety. Photocatalytic technology shows great advantages for ammonia nitrogen removal, such as its efficiency, reusability, low cost, and environmental friendliness. In this study, CP (g-C₃N₄/CoP) composite materials, which exhibited high-efficiency ammonia nitrogen removal, were synthesized through a simple self-assembly method. For the optimal CP-10 (10% CoP) samples, the removal rate of ammonia nitrogen reached up to 94.8% within 80 min under visible light illumination. In addition, the nitrogen selectivity $S\left(N_2\right)$ is about 60% for all oxidative products. The high performance of the CP-10 photocatalysts can be ascribed to the effective separation and transmission of electron–hole pairs caused by their heterogeneous structure. This research has significance for the application of photocatalysis for the remediation of ammonia nitrogen wastewater. Full article

The effectiveness of thermal treatment technologies for the remediation of soils contaminated with heavy hydrocarbons has been extensively documented in the scientific literature. In general, high-concentration crude-oil-contaminated soil is treated with high-temperature thermal desorption (HTTD) in order to achieve high remediation efficiency. However, this process has the unintended consequence of destroying soil fertility. Low-temperature thermal desorption (LTTD) represents an alternative approach that has been developed with the objective of remediating heavily crude-oil-contaminated soil in a more rapid and cost-effective manner while simultaneously enhancing soil fertility. The thermal desorption unit (TDU) was employed using both LTTD and HTTD, operating at 300 °C and 500 °C, respectively, with a 30 min residence time in the kiln. The concentration of total petroleum hydrocarbons (TPH) in both the LTTD- and HTTD-treated soils was found to be less than 1% by weight, thereby below regulatory standards. The environmental impacts of both processes were assessed using the OpenLCA software version 2.0. The HTTD process exhibited a total abiotic depletion potential (ADP) impact of 1.63 × 10⁻⁴ MJ and a global warming potential (GWP) of 414 kg CO₂-eq. In contrast, LTTD demonstrated lower impacts, with an ADP of 1.29 × 10⁻⁴ MJ and a GWP of 278 kg CO₂-eq. The transition from HTTD to LTTD resulted in a notable reduction in ADP by 20.5% and in GWP by 32.9%. The application of LTTD-treated soil coated with coke or carbonized residues has been demonstrated to serve as an effective soil amendment, with the capacity to sequester approximately 50% of organic hydrocarbon contaminants. The results of this study illustrate the potential of LTTD for not only economical and rapid soil remediation but also the enhancement of soil quality through beneficial reuse. Full article

This study investigated the potential of biogenic ZnO nanoparticles (ZnO-NPs) to alleviate cadmium (Cd) toxicity in durum wheat plants exposed for 14 days to 25 μM CdSO₄. By applying ZnO-NPs at two different concentrations (25 and 50 mg L⁻¹), we observed increased chlorophyll content, beneficially impacting the photosynthetic efficiency, and enhanced sulfur, zinc, and iron accumulation. Moreover, the ZnO-NP treatment reduced the Cd accumulation in shoots, mitigating leaf chlorosis and oxidative damage. This response was clearly mediated by the increased thiol and phytochelatin production, as well as the enhanced sulfate uptake rate, with TdSultr1.3 as the most responsive gene coding for high-affinity transporter to Cd stress. In conclusion, the application of biogenic ZnO-NPs appears to be a promising approach for reducing the uptake of heavy metals by plants. In addition, it could be successfully used in combination with contamination prevention measures and/or remediation of contaminated sites to remove and mitigate the harmful effects of Cd on the environment and human health. Full article

Designing new engineered materials derived from waste is essential for effective environmental remediation and reducing anthropogenic pollution in our economy. This study introduces an innovative method for remediating metal-contaminated water, using two distinct waste types: one biowaste (eggshell) and one industrial waste (fly ash). We synthesized three novel, cost-effective nanoadsorbent types, including two new tertiary composites and two biopolymer-based composites (specifically k-carrageenan and chitosan), which targeted chromium removal from aqueous solutions. SEM analysis reveals that in the first composite, EMZ, zeolite, and magnetite nanoparticles are successfully integrated into the porous structure of the eggshell. In the second composite (FMZ), fly ash and magnetite particles are similarly loaded within the zeolite pores. Each biopolymer-based composite is derived by incorporating the corresponding tertiary composite (FMZ or EMZ) into the biopolymer framework. Structural modifications of the eggshell, zeolite, chitosan, and k-carrageenan resulted in notable increases in specific surface area, as confirmed by BET analysis. These enhancements significantly improve chromium adsorption efficiency for each adsorbent type developed. The adsorption performances achieved are as follows: EMZ (89.76%), FMZ (84.83%), EMZCa (96.64%), FMZCa (94.87%), EMZC (99.64%), and FMZC (97.67%). The findings indicate that chromium adsorption across all adsorbent types occurs via a multimolecular layer mechanism, which is characterized as spontaneous and endothermic. Desorption studies further demonstrate the high reusability of these nanomaterials. Overall, this research underscores the potential of utilizing waste materials for new performant engineered low-cost composites and biocomposites for environmental bioremediation applications. Full article

The quest for cleaner and sustainable energy sources is crucial, considering the current scenario of a steep rise in energy consumption and the fuel crisis, exacerbated by diminishing fossil fuel reserves and rising pollutants. In particular, the bioaccumulation of hazardous substances like trivalent chromium has not only disrupted the fragile equilibrium of the ecological system but also poses significant health hazards to humans. Microalgae emerged as a promising solution for achieving sustainability due to their ability to remediate contaminants and produce greener alternatives such as biofuels. This integrated approach provides an ambitious strategy to address global concerns pertaining to economic stability, environmental degradation, and the energy crisis. This study investigates the intricate defense mechanisms deployed by freshwater microalgae Chlorella minutissima in response to Cr (III) toxicity. The microalga achieved an impressive 92% removal efficiency with an IC₅₀ value of 200 ppm, illustrating its extraordinary resilience towards chromium-induced stress. Furthermore, this research embarked on thorough explorations encompassing morphological, pigment-centric, and biochemical analyses, aimed at revealing the adaptive strategies associated with Cr (III) resilience, as well as the dynamics of carbon pool flow that contribute to enhanced lipid and extracellular polysaccharide (EPS) synthesis. The FAME profile of the biodiesel produced complies with the benchmark established by American and European fuel regulations, emphasizing its suitability as a high-quality vehicular fuel. Elevated levels of ROS, TBARS, and osmolytes (such as glycine-betaine), along with the increased activity of antioxidant enzymes (CAT, GR, and SOD), reveal the activation of robust defense mechanisms against oxidative stress caused by Cr (III). The finding of this investigation presents an effective framework for an algal-based biorefinery approach, integrating pollutant detoxification with the generation of vehicular-quality biodiesel and additional value-added compounds vital for achieving sustainability under the concept of a circular economy. Full article

Nanofine zero−valent iron (nZVI) is a new, eco−friendly material with strong reducing and adsorbent properties that can be used to clean up heavy metal−affected soils. Herein, nZVI encapsulated with carboxymethyl cellulose (CMC−nZVI) is synthesized via an aqueous−phase reduction technique and subsequently deployed to evaluate its effectiveness in Cr(VI) soil remediation. The characterization analysis used SEM−EDS, XRD, XPS, and LSV to determine the relevant properties of the material. The results show that at an initial Cr(VI) concentration of 169.5 mg·kg⁻¹, 93.2% of Cr(VI) was removed from the soil after 10 h of treatment with CMC−nZVI at pH 3.3. The kinetic analysis showed that CMC−nZVI had the maximum equilibrium adsorption capacity for removing Cr(VI) from soil at 105.3 mg·g⁻¹. This followed a pseudo−second−order kinetic model. The study shows that CMC−nZVI converts Cr(VI) to Cr(III), which forms complexes with Fe(III) ions in the presence of hydroxide ions (OH⁻) to form a highly stable compound that eventually adsorbs into the nanomaterial’s surface for efficient removal. Full article

Understanding the interactions among biochar, plants, soils, and microbial communities is essential for developing effective and eco-friendly soil remediation strategies. This study investigates the role of cystamine-modified biochar (Cys-BC) in alleviating cadmium (Cd) toxicity in lettuce, comparing its effects to those of raw biochar. Lettuce plants were exposed to Cd stress (1–5 mg kg⁻¹), and the effects of Cys-BC were assessed by measuring plant biomass, photosynthetic efficiency, antioxidant activity, Cd bioavailability, and soil microbial diversity. Cys-BC significantly enhanced plant biomass, with increases in above-ground growth (40.54–44.95%) and root biomass (37.54–47.44%) compared to Cd-stressed controls. Photosynthetic parameters improved by up to 91.02% for chlorophyll-a content and 37.93% for the net photosynthetic rate. Cys-BC mitigated oxidative stress, increasing antioxidant activities by 73.83% to 99.39%. Additionally, Cys-BC reduced available Cd levels in the soil, primarily through enhanced cation exchange rather than changes in pH. Plant responses to Cd stress included increased glutathione reductase activity and elevated cysteine levels, which further contributed to Cd passivation. Microbial diversity in the soil increased, particularly among sulfur- and nitrogen-cycling bacteria such as Deltaproteobacteria and Nitrospira, suggesting their role in mitigating Cd stress. These findings highlight the potential of Cys-BC as an effective agent for the remediation of Cd-contaminated soils. Full article

Significant efforts have been made to develop environmentally friendly remediation methods to restore petroleum-damaged ecosystems. One such approach is cultivating plant species that exhibit high resistance to contamination. This study aimed to assess the impact of petroleum-derived soil pollutants on the photosynthetic performance of selected plant species used in green infrastructure development. A pot experiment was conducted using both contaminated and uncontaminated soils to grow six plant species under controlled conditions. Biometric parameters and chlorophyll a fluorescence measurements were taken, followed by statistical analyses to compare plant responses under stress and control conditions. This study is the first to simultaneously analyze PF, DF, and MR₈₂₀ signals in plant species exposed to petroleum contamination stress. The results demonstrated that petroleum exposure reduced the activity of both PSII and PSI, likely due to increased nonradiative energy dissipation in PSII antenna chlorophylls, decreased antenna size, and/or damage to the photosynthetic apparatus. Additionally, petroleum contamination affected the electron transport chain efficiency, limiting electron flow between PSII and PSI. The most resistant species to petroleum-induced stress were Lolium perenne, Poa pratensis, and Trifolium repens. Full article

This study investigates the pollution characteristics and environmental risks of crushed microplastics (MPs) generated during plastic recycling, emphasizing their adsorption capacity for heavy metals, particularly lead (Pb). SEM-EDS analysis revealed that crushed MPs exhibit significantly higher adsorption capacity than primary MPs due to their larger surface area and more available adsorption sites, including oxygen-containing functional groups. The adsorption behavior of MPs was influenced by key factors such as MP size, MP quantity, pH, salinity, and biofilm formation. Smaller MPs demonstrated higher adsorption efficiency, while elevated pH enhanced Pb adsorption. Conversely, increased salinity reduced adsorption due to competition for adsorption sites. Increasing MP concentrations improved Pb removal efficiency, but higher MP quantities led to a decrease in maximum adsorption capacity, demonstrating a trade-off between removal efficiency and adsorption capacity. Isothermal adsorption experiments revealed that Pb adsorption on MPs follows a multi-layer mechanism, best characterized by the Freundlich model. The adsorption capacity increased nonlinearly with Pb concentration and stabilized as surface sites became saturated. The formation of biofilms on MPs further enhanced their adsorption capacity by providing additional functional groups and facilitating multi-layer adsorption, increasing ecological risks. Adsorption kinetics were best described by pseudo-second-order and intra-particle diffusion models, indicating chemical adsorption and boundary layer diffusion as dominant mechanisms. Magnetic Fe₃O₄ nanoparticles demonstrated a high recovery efficiency of 99.3% for MPs, highlighting their potential for environmental remediation. However, the presence of adsorbed Pb slightly reduced recovery performance, emphasizing the need to optimize recovery conditions for maximum efficiency. These findings underscore the dual threat posed by crushed MPs: their capacity to adsorb and concentrate harmful substances, increasing ecological toxicity, and the challenges associated with their recovery. This research provides critical insights into mitigating MP pollution and developing effective recovery strategies under realistic environmental conditions. Full article