Search Results (52)

Industrial effluents pose a significant concern because they contain a variety of metals and metalloids that have detrimental effects on the environment. Conventional techniques are widely used in effluent treatment plants (ETPs) to remove metallic pollutants; however, they are less effective, are costly, and generate secondary toxic waste. Mycosorbent would be a sustainable and economical alternative to conventional techniques, as it offers numerous advantages. In this study, we shed light on the development of mycosorbent, which could be potentially applicable in the treatment of industrial effluent. In a competitive (i.e., multimetal system) optimisation study, mycosorbent AD2 exhibited a maximum biosorption capacity of 3.7 to 6.20 mg/g at pH 6.0, with an initial metal ion concentration of 25 mg/L, a contact time of 2 h, at 50 ± 2 °C, and a pH_PZC of 5.3. The metal-removal capacity increased up to 1.23-fold after optimisation. The thermodynamic parameters confirmed that the AD2 mycosorbent facilitated an endothermic, feasible, and spontaneous biosorption process. The FT-IR and SEM characterisation analysis confirmed the adsorption of metals on the surface of the mycosorbent from the aqueous system. This study demonstrated that mycosorbent could be an effective tool for combating metallic pollutants in various industrial effluents. Full article

Rapid growth in the alumina industry generates vast amounts of highly alkaline red mud (RM), posing significant environmental risks. However, RM shows great promise as a resource for environmental remediation, particularly through its conversion into effective adsorbents. This research reviews recent advancements in developing RM-based adsorbents for sustainable wastewater treatment, especially targeting heavy metal(loid)s (HMs). We examine key modification mechanisms to enhance RM’s properties, summarize synthesis methods for various RM- based adsorbents, and evaluate their performance in removing HMs from water, guiding the design of subsequent new materials. Crucially, this review highlights studies on adsorbent reusability, HM leaching, and economic feasibility to address economic and safety concerns. Finally, we discuss adsorption mechanisms and prospects for these materials. Full article

The metalloid arsenic (As) and the metals lead (Pb) and mercury (Hg), which together we call the “Toxic Triad”, are among the pollutants of greatest global concern, harming the health of millions of people and contributing to biodiversity loss. The widespread distribution of As, Pb and Hg facilitates the exposure of humans and other species to these elements simultaneously, potentially amplifying their individual toxic effects. While As, Pb and Hg are well established as toxic elements, the mechanisms by which they interact with genetic material and impact the health of various species remain incompletely understood. This is particularly true regarding the combined effects of these three elements. In this context, the objective of this work was to perform a toxicogenomic analysis of As, Pb and Hg to highlight multiple aspects of element-gene interactions, in addition to revisiting information on the genotoxicity and carcinogenicity of the Toxic Triad. By using The Comparative Toxicogenomics Database, it was possible to identify that As interacts with 7666 genes across various species, while Pb influences 3525 genes, and Hg affects 692 genes. Removing duplicate gene names, the three elements interact with 9763 genes across multiple species. Considering the top-20 As/Pb/Hg-interacting genes, catalase (CAT), NFE2 like bZIP transcription factor 2 (NFE2L2), caspase 3 (CASP3), heme oxygenase (HMOX1), tumor necrosis factor (TNF), NAD(P)H quinone dehydrogenase 1 (NQO1) and interleukin 6 (IL6) were the most frequently observed. In total, 172 genes have the potential to interact with the three elements. Gene ontology analysis based on those genes evidenced that the Toxic Triad affects several cellular compartments and molecular functions, highlighting its effect on stimulation of toxic stress mechanisms. These 172 genes are also associated with various diseases, especially those of the urogenital tract, as well as being related to biological pathways involved in infectious diseases caused by viruses, bacteria and parasites. Arsenic was the element with the best-substantiated genotoxic and carcinogenic activity. This article details, through a toxicogenomic approach, the genetic bases that underlie the toxic effects of As, Pb and Hg. Full article

The presence of dissolved sulfides in feed seawater causes severe elemental sulfur fouling in the reverse osmosis (RO) process. However, current pretreatment methods suffer from large footprint, high energy consumption, and limitations in effluent quality. In this study, adsorption and microfiltration are merged into a single process for the pretreatment of sulfide-containing seawater. Powdered activated carbon (PAC) was selected for its superior adsorption capacity (14.6-fold) and faster kinetics (3.9-fold) for sulfide removal compared to granular activated carbon. The high surface area and multiple pore structures of PAC facilitate surface and intraparticle diffusion, as well as anion–π conjugation likely occur between PAC and sulfide. Polypropylene microporous membranes, capable of tolerating high PAC dosages, were used in the hybrid process. Long-term pilot tests demonstrated that the effluent (turbidity < 1 NTU and SDI₁₅ ≈ 2.50) met the quality requirements for RO unit feedwater, achieving 100% sulfide removal efficiency over 101 h, with no risk of PAC leakage throughout the entire operation process. The formation of a loose, porous PAC cake layer alleviates membrane fouling and enhances the retention and adsorption of metal(loid)s and sulfide. Moreover, the low permeate flux of the polymeric membranes significantly mitigates filter cake formation. The hybrid system adapts to variations in feedwater quality, making it highly suitable for desalination plants with limited space and budget. These findings offer valuable insights and practical guidance for advancing seawater desalination pretreatment. Full article

This study presents the effectiveness of two vertical subsurface flow (VF) constructed wetlands (CWs), one planted with Juncus effusus (PCW) and the other unplanted (CCW), for the remediation of acid mine drainage (AMD) from the Ouixane abandoned mine site located in Morocco. The VFs were fed with highly acidic AMD (pH < 2.5) and were evaluated over a period of 150 days. The substrate was composed of limestone, as a neutralizing agent, river gravel, and natural peat moss, with the goal of promoting the growth of sulfate-reducing bacteria (SRB) and metals precipitation. The results showed that both VFs successfully neutralized the acidity, with effluent pH values ranging from 3.57 to 8.5, indicating effective alkalinization of the AMD. Significant differences (p < 0.05) were observed between the metal removal rates of the CCW and the PCW, except for Mn. Both types of constructed wetlands (CWs), the planted system (PCW) and the unplanted system (CCW), exhibited similar efficiencies in metal removal from the influent. The rates of metalloid removal were as follows: 99.9% vs. 99% for Cr, 99% vs. 80% for As, 96% vs. 94 for Zn, 99.94% vs. 99% for Fe, and 90% vs. 81% for Al. Microbial sulfate reduction was increased from 43% to 50% by the presence of plants. Sediment analysis revealed that metals were primarily in stable forms: Fe and Zn were mostly associated with Fe-Mn oxides, while Mn and Ni were predominantly present as carbonates. These observations indicate a relative stability of metals in the CWs’ sediment. This study highlights the effectiveness of the studied CWs, particularly those with vegetation, for AMD remediation, emphasizing the importance of neutralizing agents, plants, and organic substrates in the treatment process. Full article

This study focuses on Pb²⁺ and As(V) adsorption on mineral heterostructures based on a mixture of Si, Fe, and Ti oxides (MOHs). Various techniques were performed to analyze the morphological and structural properties of the synthesized metal oxide samples. In addition to the experimental optimization of the parameters determined by the response surface method (RSM), the effects of pH, adsorbent dosage, temperature, and contact duration on the batch and column system adsorption efficiency of single-component and simultaneous lead and arsenate removal were tested. The pseudo-second-order kinetic model and Weber–Morris model were more relevant to the adsorption on the metal(loid)s. The adsorption of Pb²⁺ was related to the Langmuir isotherm model, while the adsorption of As(V) was fitted to the Freundlich isotherm model. The thermodynamic parameters indicate the spontaneity of the adsorption process with a low endothermic character. The MOHs were more effective in removing Pb²⁺ and As(V) in the multi-component system (87.7 and 46.1%, respectively) than in the single-component system (56.3 and 23.4%, respectively). This study demonstrates that mineral heterostructures can be effectively used to remove cations and anions from water systems, and due to their fast kinetics, they can be applied to the needs of rapid interventions after pollution. Full article

This article compares chemical coagulation with electrocoagulation, two popular methods for the primary treatment of wastewater generated in the process of underground coal gasification (UCG). The primary aim was to determine which method is more effective in the removal of cyanide and sulphide ions, metals and metalloids, as well as organic compounds. In both cases, experiments were conducted in batch 1 dm³ reactors and using iron ions. Four types of coagulants were tested during the chemical coagulation study: FeCl₂, FeSO₄, Fe₂(SO₄)₃, and FeCl₃. In the electrocoagulation experiments, pure iron Armco steel was used to manufacture the sacrificial iron anode. Both processes were tested under a wide range of operating conditions (pH, time, Fe dose) to determine their maximum efficiency for treating UCG wastewater. It was found that, through electrocoagulation, a dose as low as 60 mg Fe/dm³ leads to >60% cyanide reduction and >98% sulphide removal efficiency, while for chemical coagulation, even a dose of 307 mg Fe/dm³ did not achieve more than 24% cyanide ion removal. Moreover, industrial chemical coagulants, especially when used in very high doses, can be a substantial source of cross-contamination with trace elements. Full article

The mangrove ecosystems of the Department of Atlántico (Colombian Caribbean) are seriously threatened by problems of hypersalinization and contamination, especially by heavy metals from the Magdalena River. The mangrove plants have developed various mechanisms to adapt to these stressful conditions, as well as the associated microbial populations that favor their growth. In the present work, the tolerance and detoxification capacity to heavy metals, especially to mercury, of a halotolerant endophytic bacterium isolated from the species Avicennia germinans located in the Balboa Swamp in the Department of Atlántico was characterized. Diverse microorganisms were isolated from superficially sterilized A. germinans leaves. Tolerance to NaCl was evaluated for each of the obtained isolates, and the most resistant was selected to assess its tolerance to Pb²⁺, Cu²⁺, Hg²⁺, Cr³⁺, Co²⁺, Ni²⁺, Zn²⁺, and Cd²⁺, many of which have been detected in high concentrations in the area of study. According to the ANI and AAI percentages, the most halotolerant strain was identified as Priestia flexa, named P. flexa 7BS3110, which was able to tolerate up to 12.5% (w/v) NaCl and presented a minimum inhibitory concentrations (MICs) of 0.25 mM for Hg, 10 mM for Pb, and 15 mM for Cr³⁺. The annotation of the P. flexa 7BS3110 genome revealed the presence of protein sequences associated with exopolysaccharide (EPS) production, thiol biosynthesis, specific proteins for chrome efflux, non-specific proteins for lead efflux, and processes associated with sulfur and iron homeostasis. Scanning electron microscopy (SEM) analysis showed morphological cellular changes and the transmission electron microscopy (TEM) showed an electrodense extracellular layer when exposed to 0.25 mM Hg²⁺. Due to the high tolerance of P. flexa 7BS3110 to Hg²⁺ and NaCl, its ability to grow when exposed to both stressors was tested, and it was able to thrive in the presence of 5% (w/v) NaCl and 0.25 mM of Hg²⁺. In addition, it was able to remove 98% of Hg²⁺ from the medium when exposed to a concentration of 14 mg/L of this metalloid. P. flexa 7BS3110 has the potential to bioremediate Hg²⁺ halophilic contaminated ecosystems. Full article

Mining and industrial operations are often associated with metalloid and heavy metal contamination of terrestrial and aquatic ecosystems. Heavy metals can weaken the soil’s purification ability to remediate and can accumulate in the human body through crops grown in contaminated soil. In this study, a stabilization method was applied for the remediation of arsenic (As) and heavy metal (Pb and Zn) contaminated soil. Scallop shells (SLS) and starfish (Asterias amurensis, ASF), commonly regarded as waste resource materials, are selected as stabilizers. Proper recycling/reuse measures are required to limit uncontrolled disposal of SLS and ASF, prevent environmental degradation of coastal areas, and take advantage of their high calcium carbonate contents. The stabilizers were processed through −#10 mesh (0.2 mm) and −#20 mesh (0.85 mm) sieves. In addition, calcined stabilizers were produced by calcining SLS and ASF at 900 °C to compare stabilization efficiency based on the presence/absence of high-temperature heat treatment. Each of the three types of processed stabilizers was added to contaminated soil at 2 to 10 wt.%, and the mixtures were subjected to wet curing for 28 days. Extraction with 0.1 N HCl was applied for stabilization efficiency assessment. Crops were cultivated in the stabilized soil to evaluate As and heavy metal immobilization capacity. Analysis by X-ray diffraction (XRD) established that calcite (CaCO₃) was observed in the natural materials and quicklime (CaO) in the calcined materials. The stabilization efficiency assessment results showed that treatment with SLS and ASF effectively reduced the elution of Pb and Zn. SLS was effective in immobilizing As, but the application of natural ASF increased the leachability of As due to the presence of organic matter. However, applying calcined ASF effectively immobilized As because the organic matter was removed at high temperatures. When the transition of As and heavy metals to crops was evaluated, Pb concentrations that exceeded the criterion for leafy vegetables were detected in the lettuce grown in contaminated soil. However, Pb was not detected in the lettuce grown in SLS- and ASF-treated soil, confirming the stability of heavy metal immobilization. Scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM-EDX) analysis showed that the pozzolanic reaction is related to heavy metal immobilization, and Ca–As precipitation is related to the immobilization of As. The results of this study verified that SLS and ASF effectively immobilize As and heavy metals (Pb and Zn) around mines and that they can be used safely in agricultural soil. Full article

Metal contamination in drinking water is well known; however, detailed insights into the metals/metalloids in finished water and their health effects are lacking. Water samples collected over four seasons from August 2022 to April 2023 from three locations in the Yangtze River basin in Nanjing were analyzed using inductively coupled plasma mass spectrometry to detect 33 metal/metalloid types. This study assessed seasonal and spatial variations and evaluated the removal efficiencies of advanced treatment processes. Health risks from metal/metalloid ingestion were calculated using a risk assessment model from the United States Environmental Protection Agency (USEPA). No significant regional differences in total metal/metalloid concentrations were found between the source and finished waters. Metals such as Cr, Ga, Hg, Pb, and Rb varied seasonally, peaking in winter. The advanced treatment process outperformed the conventional process for As removal. However, the removal efficiencies were lower for Mn, Cd, Hg, Se, and Zn than those of the conventional process. Positive correlations were observed among several metals, suggesting that metals may have similar sources of contamination. The main carcinogenic risk exceeded the acceptable levels in children according to the USEPA. Non-carcinogenic risks were below the threshold values, but As, Tl, and V were highlighted as key risk elements. Seasonal changes markedly influenced metal/metalloid concentrations and distributions in water, necessitating risk management focused on arsenic. Full article

The development of simple, effective, economical, and environmentally friendly methods for removing hazardous substances of anthropogenic origin from aquatic systems is currently one of the greatest challenges, among others, due to the variety of pollutants and the transformations they may undergo in the environment. In recent years, there has been an increased interest in adsorption methods based on the use of natural polymers, including non-toxic chitosan (CS), which is characterized by good coating properties, biocompatibility, and biodegradability. This review concerns the latest developments (since 2019) in the application of novel chitosan-based materials for the removal of hazardous substances (e.g., metal and metalloid ions, synthetic dyes, pharmaceuticals) from aqueous solutions, with particular emphasis on their most important advantages and limitations, as well as their potential impact on sustainability. Full article

Approximately 95% of urban solid waste worldwide is disposed of in landfills. About 14 million metric tonnes of this municipal solid waste are disposed of in landfills every year in Malaysia, illustrating the importance of landfills. Landfill leachate is a liquid that is generated when precipitation percolates through waste disposed of in a landfill. High concentrations of heavy metal(loid)s, organic matter that has been dissolved and/or suspended, and inorganic substances, including phosphorus, ammonium, and sulphate, are present in landfill leachate. Globally, there is an urgent need for efficient remediation strategies for leachate-metal-contaminated soils. The present study expatiates on the physicochemical conditions and heavy metal(loid)s’ concentrations present in leachate samples obtained from four landfills in Malaysia, namely, Air Hitam Sanitary Landfill, Jeram Sanitary landfill, Bukit Beruntung landfill, and Taman Beringin Landfill, and explores bioaugmentation for the remediation of leachate-metal-contaminated soil. Leachate samples (replicates) were taken from all four landfills. Heavy metal(loids) in the collected leachate samples were quantified using inductively coupled plasma mass spectrometry. The microbial strains used for bioaugmentation were isolated from the soil sample collected from Taman Beringin Landfill. X-ray fluorescence spectrometry was used to analyze heavy metal(loid)s in the soil, prior to the isolation of microbes. The results of the present study show that the treatments inoculated with the isolated bacteria had greater potential for bioremediation than the control experiment. Of the nine isolated microbial strains, the treatment regimen involving only three strains (all Gram-positive bacteria) exhibited the highest removal efficiency for heavy metal(loid)s, as observed from most of the results. With regard to new findings, a significant outcome from the present study is that selectively blended microbial species are more effective in the remediation of leachate-metal-contaminated soil, in comparison to a treatment containing a higher number of microbial species and therefore increased diversity. Although the leachate and soil samples were collected from Malaysia, there is a global appeal for the bioremediation strategy applied in this study. Full article

This article explores recent advancements and innovative strategies in biosorption technology, with a particular focus on the removal of heavy metals, such as Cu(II), Pb(II), Cr(III), Cr(VI), Zn(II), and Ni(II), and a metalloid, As(V), from various sources. Detailed information on biosorbents, including their composition, structure, and performance metrics in heavy metal sorption, is presented. Specific attention is given to the numerical values of the adsorption capacities for each metal, showcasing the efficacy of biosorbents in removing Cu (up to 96.4%), Pb (up to 95%), Cr (up to 99.9%), Zn (up to 99%), Ni (up to 93.8%), and As (up to 92.9%) from wastewater and industrial effluents. In addition, the issue of biosorbent deactivation and failure over time is highlighted as it is crucial for the successful implementation of adsorption in practical applications. Such phenomena as blockage by other cations or chemical decomposition are reported, and chemical, thermal, and microwave treatments are indicated as effective regeneration techniques. Ongoing research should focus on the development of more resilient biosorbent materials, optimizing regeneration techniques, and exploring innovative approaches to improve the long-term performance and sustainability of biosorption technologies. The analysis showed that biosorption emerges as a promising strategy for alleviating pollutants in wastewater and industrial effluents, offering a sustainable and environmentally friendly approach to addressing water pollution challenges. Full article

Mining waste represents a global issue due to its potential of generating acidic or alkaline leachate with high concentrations of metals and metalloids (metal(loid)s). Microbial-induced calcium carbonate precipitation (MICP) is an engineering tool used for remediation. MICP, induced via biological activity, aims to precipitate calcium carbonate (CaCO₃) or co-precipitate other metal carbonates (MCO₃). MICP is a bio-geochemical remediation method that aims to immobilize or remove metal(loid)s via enzyme, redox, or photosynthetic metabolic pathways. Contaminants are removed directly through immobilization as mineral precipitates (CaCO₃ or MCO₃), or indirectly (via sorption, complexes, or inclusion into the crystal structure). Further, CaCO₃ precipitates deposited on the surface or within the pore spaces of a solid matrix create a clogging effect to reduce contaminant leachate. Experimental research on MICP has shown its promise as a bioremediation technique for mining waste. Additional research is required to evaluate the long-term feasibility and potential by-products of MICP-treated/stabilized waste. Full article

(1) Background: The frequency and intensity of war-like activities (war, military training, and shooting ranges) worldwide cause soil pollution by metals, metalloids, explosives, radionuclides, and herbicides. Despite this environmentally worrying scenario, soil decontamination in former war zones almost always involves incineration. Nevertheless, this practice is expensive, and its efficiency is suitable only for organic pollutants. Therefore, treating soils polluted by wars requires efficient and economically viable alternatives. In this sense, this manuscript reviews the status and knowledge gaps of mycoremediation. (2) Methods: The literature review consisted of searches on ScienceDirect and Web of Science for articles (1980 to 2023) on the mycoremediation of soils containing pollutants derived from war-like activities. (3) Results: This review highlighted that mycoremediation has many successful applications for removing all pollutants of war-like activities. However, the mycoremediation of soils in former war zones and those impacted by military training and shooting ranges is still very incipient, with most applications emphasizing explosives. (4) Conclusion: The mycoremediation of soils from conflict zones is an entirely open field of research, and the main challenge is to optimize experimental conditions on a field scale. Full article