Simultaneous electrodialytic removal of PAH, PCB, TBT and heavy metals from sediments

Feasible synthesis of coal fly ash based porous composites with multiscale pore structure and its application in Congo red adsorption

Facing the great challenge that the increasing solid waste fly ash is difficult to treat and utilize properly, this paper reports a class of novel low-cost fly ash porous materials with high interconnected porosity fabricated by a facile foaming process. On this basis, composites with multiscale pore structures from the nanometer to macroscopic scale were designed and constructed by decorating layered double hydroxide (LDH) onto the inner channel surface. Such porous materials with 3D through-hole structures showed high interconnected porosity (up to 77.61%), suitable compressive strength (up to 23.79 MPa) and significant water permeation flux (549.86 m³∙m^-2∙h^-1 at 0.1 MPa). Moreover, the adsorption effect of dosage, initial concentration, pH, temperature and contact time on Congo red (CR) from simulated wastewater was investigated. The composites exhibited a good adsorption efficiency of ∼100% and adsorption capacities of 45.79 mg/g. The adsorption kinetic can be explained well by the pseudosecond-order kinetic equation and isotherm adsorption followed Langmuir isotherm model. This suggests that low-cost and eco-friendly fly ash composites have potential applications in industrial-scale wastewater treatment. This work also provides a general strategy to design and utilize fly ash porous materials for filtration and adsorption.

Removal of organotin compounds and metals from Swedish marine sediment using Fenton's reagent and electrochemical treatment

Metal and tributyltin (TBT) contaminated sediments are problematic for sediment managers and the environment. This study is the first to compare Fenton's reagent and electrochemical treatment as remediation methods for the removal of TBT and metals using laboratory-scale experiments on contaminated dredged sediment. The costs and the applicability of the developed methods were also compared and discussed. Both methods removed > 98% TBT from TBT-spiked sediment samples, while Fenton's reagent removed 64% of the TBT and electrolysis 58% of the TBT from non-spiked samples. TBT in water phase was effectively degraded in both experiments on spiked water and in leachates during the treatment of the sediment. Positive correlations were observed between TBT removal and the added amount of hydrogen peroxide and current density. Both methods removed metals from the sediment, but Fenton's reagent was identified as the most potent option for effective removal of both metals and TBT, especially from highly metal-contaminated sediment. However, due to risks associated with the required chemicals and low pH level in the sediment residue following the Fenton treatment, electrochemical treatment could be a more sustainable option for treating larger quantities of contaminated sediment.

Integrated cost and environmental impact assessment of management options for dredged sediment

Large quantities of sediment must be dredged regularly to enable marine transport and trade. The sediments are often polluted, with e.g. metals, which limits the management options. The aim of this study has been to assess costs and environmental impacts (impact on climate, marine organisms, etc.) of different management options for polluted dredged sediment, by combining life-cycle assessment (LCA) of the climate impact, scoring of other environmental aspects and a cost evaluation. This approach has been used to study both traditional and new management alternatives for a real port case. The studied options include landfilling, deep-sea disposal, construction of a port area using a stabilization and solidification (S/S) method, and a combination of the aforementioned methods with the innovative option of metal recovery through sediment electrolysis. The LCA showed that deep-sea disposal had the lowest climate impact. The assessment of the other environmental impacts showed that the result varied depending on the pollution level and the time perspective used (short or long-term). Using sediment for construction had the highest climate impact, although other environmental impacts were comparably low. Electrolysis was found to be suitable for highly polluted sediments, as it left the sediment cleaner and enabled recovery of precious metals, however the costs were high. The results highlight the complexity of comparing different environmental impacts and the benefits of using integrated assessments to provide clarity, and to evaluate both the synergetic and counteracting effects associated with the investigated scenarios and may aid early-stage decision making.

Recent advances in PCB removal from historically contaminated environmental matrices

Despite being drastically restricted in the 1970s, polychlorinated biphenyls (PCBs) still belong among the most hazardous contaminants. The chemical stability and dielectric properties of PCBs made them suitable for a number of applications, which then lead to their ubiquitous presence in the environment. PCBs are highly bioaccumulative and persistent, and their teratogenic, carcinogenic, and endocrine-disrupting features have been widely reported in the literature. This review discusses recent advances in different techniques and approaches to remediate historically contaminated matrices, which are one of the most problematic in regard to decontamination feasibility and efficiency. The current knowledge published in the literature shows that PCBs are not sufficiently removed from the environment by natural processes, and thus, the suitability of some approaches (e.g., natural attenuation) is limited. Physicochemical processes are still the most effective; however, their extensive use is constrained by their high cost and often their destructiveness toward the matrices. Despite their limited reliability, biological methods and their application in combinations with other techniques could be promising. The literature reviewed in this paper documents that a combination of techniques differing in their principles should be a future research direction. Other aspects discussed in this work include the incompleteness of some studies. More attention should be given to the evaluation of toxicity during these processes, particularly in terms of monitoring different modes of toxic action. In addition, decomposition mechanisms and products need to be sufficiently clarified before combined, tailor-made approaches can be employed.

Simultaneous decontamination of multi-pollutants: A promising approach for water remediation

Water remediation techniques have been extensively investigated due to the increasing threats of soluble pollutants posed on the human health, ecology and sustainability. Confronted with the complex composition matrix of wastewater, the simultaneous elimination of coexisting multi-pollutants remains a great challenge due to their different physicochemical properties. By integrating multi-contaminants elimination processes into one unit operation, simultaneous decontamination attracted more and more attention under the consideration of versatile applications and economical benefits. In this review, the state-of-art simultaneous decontamination methods were systematically summarized as chemical precipitation, adsorption, photocatalysis, oxidation-reduction, biological removal and membrane filtration. Their applications, mechanisms, mutual interactions, sustainability and recyclability were outlined and discussed in detail. Finally, the prospects and opportunities for future research were proposed for further development of simultaneous decontamination. This work could provide guidelines for the design and fabrication of well-organized simultaneous decontaminating system.

Distribution, Source and Potential Risk Assessment of Polychlorinated Biphenyls (PCBs) in Sediments from the Liaohe River Protected Area, China

This study aimed to assess the occurrence, distribution, toxicity equivalency and health risks of dl-PCBs (dioxin-like PCBs) from nine sites collected in surface sediments from Liaohe River Protected Area. ∑dl-PCBs concentrations in sediments range from 79.2 to 365.1 pg/g. Sediment profiles showed that pentachlorobiphenyl is the most abundant congener among all sampling sites. The results of principal component analysis and cluster analysis indicated that PCBs were mainly derived from electronic waste and paint additives in the sediments of Liaohe River Protected Area. Toxic equivalent quantity (TEQ) values of the PCBs in the Liaohe River Protected Area sediments are at comparatively lower levels compared with the previously reported data. Hazardous ratio (HR) for human health risk assessment allied to cancer was found to be lower than the non-carcinogenic risk assessment within an acceptable range.

Ultrasonic processes for the advanced remediation of contaminated sediments

Sediments play a fundamental role in the aquatic environment, so that the presence of contaminants poses severe concern for the possible negative effects on both environmental and human health. Sediment remediation is thus necessary to reduce pollutant concentrations and several techniques have been studied so far. A novel approach for sediment remediation is the use of Advanced Oxidation Processes, which include ultrasound (US). This paper focuses on the study of the ultrasonic effects for the simultaneous reduction of both organic and inorganic contaminants from sediments. To this end, the US technology was investigated as a stand-alone treatment as well as in combination with an electro-kinetic (EK) process, known to be effective in the removal of heavy metals from soil and sediments. The US remediation resulted in higher organic compound degradation, with an average 88% removal, but promising desorption yields (47-84%) were achieved for heavy metals as well. The combined EK/US process was found to be particularly effective for lead. Experimental outcomes highlighted the potential of the ultrasonic technology for the remediation of contaminated sediments and addressed some considerations for the possible scale-up.

Combining Chemometrics and Sensors: Toward New Applications in Monitoring and Environmental Analysis

For many years, an extensive array of chemometric methods have provided a platform upon which a quantitative description of environmental conditions can be obtained. Applying chemometric methods to environmental data allows us to identify and describe the interrelations between certain environmental drivers. They also provide an insight into the interrelationships between these drivers and afford us a greater understanding of the potential impact that these drivers can place upon the environment. However, an effective marriage of these two systems has not been performed. Therefore, it is the aim of this review to highlight the advantages of using chemometrics and sensors to identify hidden trends in environmental parameters, which allow the state of the environment to be effectively monitored. Despite the combination of chemometrics and sensors, to capture new developments and applications in the field of environmental sciences, these methods have not been extensively used. Importantly, although different parameters and monitoring procedures are required for different environments (e.g., air, water, soil), they are not distinct, separate entities. Contemporary developments in the use of chemometrics afford us the ability to predict changes in different aspects of the environment using instrumental methods. This review also provides an insight into the prevailing trends and the future of environmental sensing, highlighting that chemometrics can be used to enhance our ability to monitor the environment. This enhanced ability to monitor environmental conditions and to predict trends would be beneficial to government and research agencies in their ability to develop environmental policies and analysis procedures.

Assessing the Efficacy of a Sediment Remediation Program Using Benthic and Pelagic Copepod Bioassays

Tributyltin is an organotin chemical that has been commonly used in ship antifouling paints. Despite the global total prohibition of tributyltin-based paint in 2008, tributyltin continues to be found at toxic levels in areas of high maritime traffic such as ports and harbors. A remediation program was conducted at a New Zealand port to reduce tributyltin and copper concentrations to acceptable values. The present study assessed the efficacy of the program using a combination of chemical analyses and copepod bioassays. Sediment and water samples were collected at 3 locations along a spatial gradient within the port, and concentrations of various organotin compounds and trace metal levels were measured pre- and postremediation. The toxicity of sediment and elutriate samples was estimated by benthic and pelagic copepod bioassays. Although acute toxicity in sediment samples was reduced following remediation, reproductive success was still affected for the benthic copepod. This approach combining chemical analysis and bioassays is promising for assessing the efficacy of remediation processes at contaminated marine sites. Environ Toxicol Chem 2020;39:492-499. © 2019 SETAC.

Utilization of nanomaterials for in-situ remediation of heavy metal(loid) contaminated sediments: A review

Heavy metal(loid)s are toxic and non-biodegradable environmental pollutants. The contamination of sediments with heavy metal(loid)s has attracted increasing attention due to the negative environmental effects of heavy metal(loid)s and the development of new remediation techniques for metal(loid) contaminated sediments. As a result of rapid nanotechnology development, nanomaterials are also being increasingly utilized for the remediation of contaminated sediments due to their excellent capacity of immobilizing/adsorbing metal(loid) ions. This review summarizes recent studies that have used various nanomaterials such as nanoscale zero-valent iron (nZVI), stabilizer-modified nZVI, nano apatite based-materials including nano-hydroxyapatite particles (nHAp) and stabilized nano-chlorapatite (nCLAP), carbon nanotubes (CNTs), and titanium dioxide nanoparticles (TiO₂ NPs) for the remediation of heavy metal(loid) contaminated sediments. We also review the analysis of potential mechanisms involved in the interaction of nanomaterials with metal(loid) ions. Subsequently, we discuss the factors affecting the nanoparticle-heavy metal(loid)s interaction, the environmental impacts resulting from the application of nanomaterials, the knowledge gaps, and potential future research.

Enhancement of Detoxification of Petroleum Hydrocarbons and Heavy Metals in Oil-Contaminated Soil by Using Glycine-β-Cyclodextrin

Soil contamination with petroleum hydrocarbons and heavy metals is a widespread environmental problem. In recent years, cyclodextrin has attracted research interest because of its special hole structure that can form inclusion complexes with certain small molecules. However, the solubility of β-cyclodextrin (β-CD) in water is low and it crystallizes easily, leading to its low utilization in practice. In this experiment, we connected β-CD with glycine under alkaline conditions to prepare glycine-β-cyclodextrin (G-β-CD), which is water soluble, has stronger coordinating ability with heavy metals, and is more suitable for treating oil-contaminated soil. The results show that G-β-CD provides better desorption of petroleum hydrocarbons and heavy metals in soils with low organic matter content (1%) and NaNO₃ of 0.25 mol/L at 70 g/L G-β-CD under mildly acidic (pH 5⁻6) conditions. The results indicate that petroleum hydrocarbons and heavy metals were removed simultaneously by means of pretreatment with G-β-CD, and the results can provide a theoretical basis for remediation of petroleum-contaminated soil.

State of the art and future challenges for polycyclic aromatic hydrocarbons is sediments: sources, fate, bioavailability and remediation techniques

Polycyclic aromatic hydrocarbons (PAHs) are amongst the most abundant contaminants found in the aquatic environment. Due to their toxicity and carcinogenicity, their sources, fate, behaviour, and cleanup techniques have been widely investigated in the last several decades. When entering the sediment-water system, PAH fate is determined by particular PAH and sediment physico-chemical properties. Most of the PAHs will be associated with fine-grained, organic-rich, sediment material. This makes sediment an ultimate sink for these pollutants. This association results in sediment contamination, and in this manner, sediments represent a permanent source of water pollution from which benthic organisms may accumulate toxic compounds, predominantly in lipid-rich tissues. A tendency for biomagnification can result in critical body burdens in higher trophic species. In recent years, researchers have developed numerous methods for measuring bioavailable fractions (chemical methods, non-exhaustive extraction, and biomimetic methods), as valuable tools in a risk-based approach for remediation or management of contaminated sites. Contaminated sediments pose challenging cleanup and management problems, as conventional environmental dredging techniques are invasive, expensive, and sometimes ineffective or hard to apply to large and diverse sediment sites. Recent studies have shown that a combination of strategies including in situ approaches is likely to provide the most effective long-term solution for dealing with contaminated sediments. Such in situ approaches include, but are not limited to: bioaugmentation, biostimulation, phytoremediation, electrokinetic remediation, surfactant addition and application of different sorbent amendments (carbon-rich such as activated carbon and biochar) that can reduce exposure and limit the redistribution of contaminants in the environment.

Techno-economic analysis of the scale-up process of electrochemically-assisted soil remediation

This work presents a techno-economic study of the scaling-up of the electrochemically-assisted soil remediation (EASR) process of polluted soil. Four scales have been selected for the study: laboratory, bench, pilot and prototype, with a capacity of treating a volume of soil of 1 × 10^-4, 2 × 10^-3, 0.11 and 21.76 m³, respectively. This study analyses the technical information produced by studies carried out at each scale, and informs about the fixed costs (construction of the electrokinetic remediation reactor, installation of auxiliary services and purchase of analytical equipment) and variable costs (start-up, operation and dismantling of the test) derived from running a test at each of the evaluated scales. The information discussed in based on the experience gained with many evaluations carried out over the last decade at these scales. This information can provide useful guidance for developing a scaling-up of the EASR for many researchers starting on the evaluation of this important environmental remediation technology.

Effects of Complex Pollution of Pb and B[a]P on the Growth and Physiological and Biochemical Indexes of Ryegrass

Effects of complex pollution of Pb and B[a]P on the growth and physiological and biochemical indexes of ryegrass were investigated in a potted soil. The results showed that under single Pb treatment condition, low-concentration (0-100 mg kg^-1) Pb stimulated the increase of ryegrass biomass while high-concentration (200-400 mg kg^-1) Pb obviously inhibited ryegrass growth. Under single B[a]P pollution condition, low-concentration (0-30 mg kg^-1) B[a]P facilitated the growth of ryegrass while high-concentration (50-100 mg kg^-1) B[a]P had toxic effect on ryegrass. Under joint impacts of Pb and B[a]P at low concentrations, biomass, chlorophyll content and carotenoid content as well as POD and CAT activities of ryegrass presented firstly rising and then descending trends, SOD accumulation increased slightly and MDA didn't experience obvious change. Under co-existence of Pb and B[a]P, Pb was the main toxic factor for ryegrass growth and it controlled the variation trend of whole growth cycle of ryegrass.