Journal of hazardous materials letters最新文献

In this study, we investigated the benefit of combining Chlorella sorokiniana with manganese-containing ferrite nanoparticles (NPs) for heavy metal removal and cell harvesting. Our results demonstrate that the combination of non-toxic nanoparticles significantly enhances the heavy metal removal capacity of C. sorokiniana without affecting its growth. The microalgae combined with NPs was able to sequester Cr⁶⁺, Co²⁺, and Ni²⁺ from aqueous solutions and could remove these metals at a higher adsorption capacity and within a relatively short time than their individual counterparts, indicating a synergistic effect between the algal cells and the nanomaterials, where bioadsorption and chemisorption were the main players. Both biosorption and chemisorption capacities were found to be the highest for single-metal systems and decreased when coexisting ions were present in the solution. The adsorption of the heavy metals evaluated was better described by the pseudo-second order model than the pseudo-first order model, indicating that chemisorption dominated over physisorption. These characteristics suggest that the combination of biosorbents with nanosorbents is a promising approach for the treatment of water contaminated with heavy metals making this process more efficient, economical, sustainable, and clean.

The separation and recovery of Fe(III) in heavy metal mixtures is a great challenge due to its strong ion exchange property. In this study, we developed a novel cinnamon-like blended fiber (PAN/PEG) using electrostatic spinning and dissolution post-treatment, which exhibited highly selective separation properties and satisfactory adsorption capacity for Fe(III). Owing to the preferential coordination of Fe(III) with both cyanide and hydroxyl groups, PAN/PEG possessed such excellent adsorption capacity as 1.12 mmol/g. Notably, the infinite selective separation coefficient between Fe(III) and other heavy metal ions (HMIs) achieved even from the octa-mixed metal systems. Furthermore, PAN/PEG demonstrated good anti-interference ability against coexisting inorganic salts. In addition, PAN/PEG was highly effective in removing lower concentration Fe(III) from complex PTA wastewater with super-high selectivity, which enabled the subsequent purification of Co(II) and Mn(II). Overall, PAN/PEG could be prepared and recovered facilely, and had great potential in the exclusive separation of Fe(III).

In advanced oxidation processes with metal-containing catalysts, metal dissolution usually leads to reduced efficiency and biotoxicity. Therefore, it is very important to find efficient non-metallic materials. In this work, a metal-free mesoporous tubular g-C₃N₄ was fabricated using melamine and urea mixed according to the mass ratios of 1:12 (TPCN₁₂) by a facile one-step thermal polymerization method. Mesoporous tubular TPCN₁₂ was proved to be successfully synthesized by scanning electron microscope (SEM) and X-ray diffraction (XRD). Then the degradation of carbamazepine (CBZ) by activating peroxymonosulfate (PMS) of TPCN₁₂ under visible light was investigated. It was found that degradation rate constant of CBZ in TPCN₁₂/Vis/PMS system (0.0939 min⁻¹) exhibited great superiority over that in TPCN₁₂/Vis system (0.0149 min⁻¹) and in TPCN₁₂/PMS system, which indicated TPCN₁₂, Vis and PMS had a synergistic effect. The dominant role of the electron transfer and the primary contribution of the holes (h⁺) and •O₂⁻ reactive species were revealed in TPCN₁₂/Vis/ PMS system. Furthermore, the system showed sufficient advantages over a wide pH range and high resistance to inorganic anions. In general, the TPCN₁₂/Vis/PMS system was capable of high stability and recyclability. This metal-free mesoporous tubular catalyst was proposed to achieve efficient and green elimination of pharmaceutical organic pollutants.

Concerns surrounding potential health and environmental impacts of per- and polyfluoroalkyl substances (PFAS) are growing at tremendous rates because adverse health impacts are expected with trace-level exposures. Extreme measures are required to mitigate potential PFAS contamination and minimize exposures. Extensive PFAS use results in the release of diverse PFAS species from domestic, industrial, and municipal effluents to wastewater, which partition to biosolids throughout secondary treatment. Biosolids generated during municipal wastewater treatment are a major environmental source of PFAS due to prevailing disposal practices as fertilizers. Pyrolysis is emerging as a viable, scalable technology for PFAS removal from biosolids while retaining nutrients and generating renewable, raw materials for energy generation. Despite early successes of pyrolysis in PFAS removal, significant unknowns remain about PFAS and transformation product fates in pyrolysis products and emissions. Applicable PFAS sampling methods, analytical workflows, and removal assessments are currently limited to a subset of high-interest analytes and matrices. Further, analysis of exhaust gases, particulate matter, fly ashes, and other pyrolysis end-products remain largely unreported or limited due to cost and sampling limitations. This paper identifies critical knowledge gaps on the pyrolysis of biosolids that must be addressed to assess the effectiveness of PFAS removal during pyrolysis treatment.

Many environmental factors affect the breakdown of plastics in aquatic environments, including exposure to ultraviolet (UV) irradiation and elevated environmental temperatures. More studies are needed to understand how these stressors contribute to plastic degradation, resulting in the release of smaller plastic particles. We studied the impact of environmentally relevant UV and temperature (37 °C) weathering of four high-production volume plastics (polystyrene, polypropylene, low-density polyethylene, and high-density polyethylene) suspended in water. Particle release was detected, characterized by scanning electron microscopy (SEM), and nanoparticles were quantified by nanoparticle tracking analysis (NTA). Weathering resulted in the release of micro- and nanoparticles that exhibited a plastic signature corresponding to the parent microplastic. Nanoparticle release is broadly correlated with an increase in the carbonyl index of the parent microplastic. Aged microplastics were characterized for physical and chemical changes. The impact of weathering on microplastic surface hardness and polymer oxidation depended on material type and environmental factors. Few to no particles were observed in controls, including controls that contained microplastics at 4 °C in dark conditions, highlighting the importance of weathering stimuli in particle release. These results show that plastic degradation needs to consider both the parent microplastic and the smaller particles that are formed.

Per and polyfluoroalkyl substances (PFAS) have been shown to be ubiquitous in the environment, and one issue of critical concern is the leaching of PFAS from soil to groundwater. The risk posed by contaminants present in soil is often assessed in terms of the anticipated impact to groundwater through the determination of soil screening levels (SSLs). The U.S. Environmental Protection Agency (EPA) established a soil screening model for determining SSLs. However, the model does not consider the unique retention properties of PFAS and, consequently, the SSLs established with the model may not represent the actual levels that are protective of groundwater quality. The objective of this work is to revise the standard EPA SSL model to reflect the unique properties and associated retention behavior of PFAS. Specifically, the distribution parameter used to convert soil porewater concentrations to soil concentrations is revised to account for adsorption at the air-water interface. Example calculations conducted for PFOS and PFOA illustrate the contrasting SSLs obtained with the revised and standard models. A comparison of distribution parameters calculated for a series of PFAS of different chain length shows that the significance of air-water interfacial adsorption can vary greatly as a function of the specific PFAS. Therefore, the difference between SSLs calculated with the revised versus standard models will vary as a function of the specific PFAS, with greater differences typically observed for longer-chain PFAS. It is anticipated that this revised model will be useful for developing improved SSLs that can be used to enhance site investigations and management for PFAS-impacted sites.

Synopsis

The widely used EPA SSL model is revised for PFAS applications to account for adsorption at the air-water interface.

Globally, large quantities of oily sludge are produced in petroleum refineries as wastes from petroleum refining processes. Petroleum refinery oily sludge (PROS) is a major by-product of the processes and a major contributor to pollution in the oil and gas industry. In this study, Response Surface Methodology (RSM) was used for optimising and modelling experimental work. Thermally treated PROS replaced fly ash (FA) at 5–20 % in geopolymer mortar mixes at a fixed combination of sodium silicate (Na₂SiO₃) and sodium hydroxide (NaOH). The visual observations and effects of PROS on the density and compressive strength of PROS geopolymer mortar (PGM) were studied. PGM with 10 % replacement of PROS had the maximum compressive strength of 38.17 MPa after 28 days. P-values obtained from the quadratic models developed for the synergistic effect of FA-PROS on density and compressive strength were less than 0.005. Optimisation of the synergistic effect of FA-PROS binder produced an optimal combination of both materials for maximum compressive strength and density of 2200 kg/m³ with desirability factor of 0.981. This investigation shows that replacing PROS with FA in geopolymer mortar can result in a new supply chain for greener binder materials in geopolymer mortar.

Background

Increasing use prevalence of waterpipe tobacco products raises concerns about environmental impacts from waterpipe waste disposal. The U.S. Food and Drug Administration (FDA) is required to assess the environmental impact of its tobacco regulatory actions per the National Environmental Policy Act. This study builds on FDA’s efforts characterizing the aquatic toxicity of waterpipe wastewater chemicals.

Methods

We compiled a comprehensive list of waterpipe wastewater chemical concentrations from literature. We then selected chemicals for risk assessment by estimating persistence, bioaccumulation, and aquatic toxicity (PBT) characteristics (U.S. Environmental Protection Agency), and hazardous concentration values (concentration affecting specific proportion of species).

Results

Of 38 chemicals in waterpipe wastewater with concentration data, 20 are listed as harmful or potentially harmful constituents (HPHCs) in tobacco smoke and tobacco products by FDA, and 15 are hazardous waste per U. S. Environmental Protection Agency. Among metals, six (cadmium, chromium, lead, mercury, nickel and selenium) are included in both HPHC and hazardous waste lists and were selected for future risk assessments. Among non-metals, nicotine, and 4-methylnitrosamino-1-(3-pyridyl)− 1-butanone (NNK) were shortlisted, as they are classified as persistent and toxic. Further, N-nitrosonornicotine (NNN), with a low hazardous concentration value (HC₅₀; concentration affecting 50 % of aquatic species) for chronic aquatic toxicity, had high aquatic toxicity concern and is selected.

Conclusions

The presence of multiple hazardous compounds in waterpipe wastewater highlights the importance of awareness on the proper disposal of waterpipe wastewater in residential and retail settings. Future studies can build on the hazard characterization provided in this study through fate and transport modeling, exposure characterization and risk assessments of waterpipe wastewater chemicals.