As one of emerging contaminants, microplastics (MPs) can enter the environment and adsorb toxic metals such as cadmium (Cd), thereby causing potential environmental risks. However, adsorption ...characteristics of MPs are poorly understood. Herein, batch experiments were performed to investigate the adsorption characteristics of Cd onto high-density polyethylene (HDPE) MPs with different particle sizes, that is, 1–2 mm, 0.6–1 mm, and 100–154 μm. The adsorption of Cd was quite rapid initially, and the equilibrium time was approximately 90 min. An increase in the pH of the Cd solution led to an increase in Cd adsorption. MPs with particle size of 100–154 μm had the highest adsorption capacity. Addition of 1, 10, and 100 mg/L NaCl all significantly decreased Cd adsorption. Adsorption kinetics fitted the pseudo-second-order model. Adsorption isotherm followed the Langmuir model and, to a lesser extent, the Freundlich model, with estimated maximum adsorption capacity of 30.5 μg/g. The adsorbed Cd easily desorbed from the MPs. Energy-dispersive X-ray spectroscopy (EDS) analysis confirmed Cd adsorption to and desorption from MPs. Fourier transform infrared (FTIR) spectroscopy analysis showed no new functional groups formed during the adsorption and desorption processes, suggesting physical interaction may dominate the Cd adsorption onto MPs. The present study findings provide evidence that MPs can accumulate Cd, and the adsorbed Cd may be highly available, thus posing risks to the organisms exposed to these MPs.
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•Adsorption of Cd was initially very rapid and then reached equilibrium within 90 min.•Increasing the pH of Cd solution led to an increase in Cd adsorption.•Microplastics with a smaller particle size showed higher adsorption capacity.•Addition of NaCl decreased Cd adsorption by microplastics.•The adsorbed Cd was easily desorbed from the microplastics.
The growing water stress both in terms of water scarcity and quality deterioration promotes the development of reclaimed water as a new water resource use. This paper reviewed wastewater reuse ...practices in China, and the opportunities and challenges of expanding reclaimed water use were analyzed. Rapid urbanization with the increasing of water demand and wastewater discharge provides an opportunity for wastewater reuse. The vast amount of wastewater discharge and low reclaimed water production mean that wastewater reuse still has a great potential in China. Many environmental and economic benefits and successful reclamation technologies also provide opportunities for wastewater reuse. In addition, the overall strategy in China is also encouraging for wastewater reuse. In the beginning stage of wastewater reclamation and reuse, there are many significant challenges to expand wastewater reuse in China including slow pace in adopting urban wastewater reuse programs, the establishment of integrated water resources management framework and guidelines for wastewater reuse programs, incoherent water quality requirements, the limited commercial development of reclaimed water and the strengthening of public awareness and cooperation among stakeholders.
We studied the source, concentration, spatial distribution and health risk of 16 polycyclic aromatic hydrocarbons (PAHs) in urban soils of Beijing. The total mass concentration of 16 PAHs ranged from ...93 to 13 141 μg kg
−1 with a mean of 1228 μg kg
−1. The contour map of soil PAH concentrations showed that the industrial zone, the historical Hutong district and the university district of Beijing have significantly higher concentrations than those in remainder of the city. The results of sources identification suggested that the primary sources of PAHs were vehicle exhaust and coal combustion and the secondary source was the atmospheric deposition of long-range transported PAHs. The incremental lifetime cancer risks (ILCRs) of exposing to PAHs in the urban soils of Beijing for adult were 1.77 × 10
−6 and 2.48 × 10
−5, respectively under normal and extreme conditions. For child, they were 8.87 × 10
−7 and 6.72 × 10
−6, respectively under normal and extreme conditions.
► The primary sources of PAHs in Beijing soil were vehicle exhaust and coal combustion and the secondary source was the atmospheric deposition of long-range transported PAHs. ► Three areas of high PAH concentration soils are identified by Kriging interpolation included the industrial zone, the historical Hutong district and the university district. ► The estimated incremental lifetime cancer risks associated with exposing to soil PAHs in Beijing for both adults and children are acceptable.
A systematic investigation demonstrates the sources, distribution and health risk in Beijing urban soil using mathematical, statistical and geostatistical methods.
Application of phosphate fertilizer can be a significant contributor of potentially hazardous trace elements such as arsenic, cadmium, and lead in croplands. These trace elements have the potential ...to accumulate in soils and be transferred through the food chain. We articulated the environmental risks of trace elements associated with long-term phosphate fertilizer applications by combining data from the literature and results from model simulations. Results illustrate that under normal cropping practice, the impact of phosphate fertilizers applications on trace element accumulation in receiving soils has been limited and localized. Their plant uptake varied greatly depending on the fertilizer application rates, soil and plant characteristics. This has led to a great deal of uncertainty in characterizing soil distribution coefficients, Kd, and plant uptake factors, PUF, two of the most used parameters in assessing the risks of accumulations. Therefore, the risks may be more appropriately assessed based on the probabilistic distributions of Kd and PUF.
Environmental risks of trace elements associated with long-term phosphate fertilizer applications were articulated by combining data from the literature and results from model simulations.
The modified hydrochar was prepared by a facile one-pot lime-assisted hydrothermal synthesis approach and the modified hydrochar and pristine hydrochar were investigated to immobilize the heavy ...metals (HMs) of Pb and Cd in contaminated soils. The results showed that the modified hydrochar exerted significantly enhanced effectiveness in immobilizing Pb and Cd comparing to pristine hydrochar, resulting from the increased surface functionality and non-crystalline properties, increased pH value and enhanced electronegativity of hydrochar. By introduction with 5% modified hydrochar, the contaminated soils showed the highest value of 34.5% (Pb) and 8.1% (Cd) reductions in leaching toxicity, and significant improvements of 95.1% (Pb) and 64.4% (Cd) were observed. In addition, the concentrations of acid soluble fraction were remarkably reduced by 54.0% (Pb) and 27.0% (Cd), and the reductions were much higher than that of 29.5% (Pb) and 8.3% (Cd) for 5% pristine hydrochar treatment. The enhanced surface complexation, precipitation and cation-π interaction played an important role in the immobilization of HMs in soils. The present study offered a novel and cost-effective approach to prepare soil amendment from waste biomass towards HMs immobilization in contaminated soils.
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•The modified hydrochar was prepared by a facile one-pot lime-assisted hydrothermal method.•Modified hydrochar had increased surface functionality, non-crystalline property and pH value.•Modified hydrochar showed significantly increased capacity for metal immobilization.•Modified hydrochar could be served as a novel cost-effective soil amendment.
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•The pristine hydrochar was modified by H2O2 and ultrasonic synergistic treatment.•The adsorption capacity of modified hydrochar was improved by more than 42 times.•Carboxyl and ...hydroxyl complexation and cation-π interaction were main mechanisms.•The modified hydrochar can be used as a sustainable adsorbent for water cleaning.
A highly efficient modified hydrochar material by H2O2 and ultrasonic synergistic treatment was prepared for Pb2+ removal in aqueous solution. The removal mechanism was investigated by a number of techniques and was provided by quantitative calculation. The maximum adsorption capacity of Pb2+ by the modified hydrochar was calculated to be 92.80 mg g−1 at pH 5.0 and 298 K, which was more than 42 times higher than pristine hydrochar (2.20 mg g−1) and much higher than the other reported modified hydrochar materials. The characterization results showed that H2O2 treatment changed elemental composition, surface charge and increased oxygen-containing functional groups of the hydrochar. The mechanism study indicated that complexation with free carboxyl and hydroxyl and cation-π interaction were main mechanisms responsible for Pb2+ sorption and their corresponding contribution percentage of different mechanisms to the Pb2+ sorption was accounting for 62.12%, 27.14% and 10.74%, respectively.
•The thermal behavior of the hydrochars from co-HTC of SS and SD was investigated.•Kinetic and thermodynamic parameters of hydrochar pyrolysis were studied.•Addition of SD during HTC of SS decreased ...the average E values of the hydrochars.•SS addition during HTC of SD improved pyrolysis reactivity of hydrochar from SD.
The thermal behavior of the hydrochars from co-hydrothermal carbonization (co-HTC) of sawdust (SD) and sewage sludge (SS) was investigated using thermogravimetric analysis. The comprehensive devolatilization index indicated that the devolatilization performance of SS was decreased by HTC, while it was significantly improved 7.38–23.69 times by co-HTC. The kinetic analysis showed that HTC of SS decreased the average activation energy from 308.96 and 314.78 kJ mol−1 to 220.86 and 221.27 kJ mol−1 by Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS), respectively, while it was increased from 182.37 to 207.06 kJ mol−1 and from 181.06 to 207.05 kJ mol−1 with the increasing proportion of SD from 25% to 75% during co-HTC, respectively. The thermodynamic parameters revealed that pyrolysis reactivity of the hydrochar derived from SD was improved by co-HTC of SD and SS. Kinetic and thermodynamic findings were useful for the design of pyrolysis process using hydrochar as solid fuel.
An overview of reclaimed water reuse in China Yi, Lili; Jiao, Wentao; Chen, Xiaoning ...
Journal of environmental sciences (China),
01/2011, Letnik:
23, Številka:
10
Journal Article
Recenzirano
China is facing severe water problems including scarcity and pollution which are now becoming key factors restricting developments. Creating an alternative water resource and reducing effluent ...discharges, water reuse has been recognized as an integral part of water and wastewater management scheme in China. The government has launched nationwide efforts to optimize the benefits of utilizing reclaimed water. This article reviewed the water reuse activities in China, including: (1) application history and current status; (2) potentials of reclaimed water reuse; (3) laws, policies and regulations governing reclaimed water reuse; (4) risks associated with reclaimed water reuse; (5) issues in reclaimed water reuse. Reclaimed water in Beijing and Tianjin were given as examples. Suggestions for improving the efficiencies of reusing urban wastewater were advanced. Being the largest user of reclaimed wastewater in the world, China's experience can benefit the development of water reuse in other regions.
Abstract
Artificial photosynthesis is a promising strategy for efficient hydrogen peroxide production, but the poor directional charge transfer from bulk to active sites restricts the overall ...photocatalytic efficiency. To address this, a new process of dipole field-driven spontaneous polarization in nitrogen-rich triazole-based carbon nitride (C
3
N
5
) to harness photogenerated charge kinetics for hydrogen peroxide production is constructed. Here, C
3
N
5
achieves a hydrogen peroxide photosynthesis rate of 3809.5 µmol g
−1
h
−1
and a 2e
−
transfer selectivity of 92% under simulated sunlight and ultrasonic forces. This high performance is attributed to the introduction of rich nitrogen active sites of the triazole ring in C
3
N
5
, which brings a dipole field. This dipole field induces a spontaneous polarization field to accelerate a rapid directional electron transfer process to nitrogen active sites and therefore induces Pauling-type adsorption of oxygen through an indirect 2e
−
transfer pathway to form hydrogen peroxide. This innovative concept using a dipole field to harness the migration and transport of photogenerated carriers provides a new route to improve photosynthesis efficiency via structural engineering.
The cleaning-up of viscous oil spilled in ocean is a global challenge, especially in Bohai, due to its slow current movement and poor self-purification capacity. Frequent oil-spill accidents not only ...cause severe and long-term damages to marine ecosystems, but also lead to a great loss of valuable resources. To eliminate the environmental pollution of oil spills, an efficient and environment-friendly oil-recovery approach is necessary. In this study,1expanded graphite (EG) modified by CTAB-KBr/H3PO4 was synthesized via composite intercalation agents of CTAB-KBr and natural flake graphite, followed by the activation of phosphoric acid at low temperature. The resultant modified expanded graphite (M-EG) obtained an interconnected and continuous open microstructure with lower polarity surface, more and larger pores, and increased surface hydrophobicity. Due to these characteristics, M-EG exhibited a superior adsorption capacity towards marine oil. The saturated adsorption capacities of M-EG were as large as 7.44 g/g for engine oil, 6.12 g/g for crude oil, 5.34 g/g for diesel oil and 4.10 g/g for gasoline oil in 120min, exceeding the capacity of pristine EG. Furthermore, M-EG maintained good removal efficiency under different adsorption conditions, such as temperature, oil types, and sodium salt concentration. In addition, oils sorbed into M-EG could be recovered either by a simple compression or filtration-drying treatment with a recovery ratio of 58–83%. However, filtration-drying treatment shows better performance in preserving microstructures of M-EG, which ensures the adsorbents can be recycled several times. High removal capability, fast adsorption efficiency, excellent stability and good recycling performance make M-EG an ideal candidate for treating marine oil pollution in practical application.
Expanded graphite modified by CTAB-KBr/H3PO4 was synthesized via composite intercalation agent of CTAB-KBr and natural flake graphite, followed by the activation of phosphoric acid at low temperature. High removal capability, fast adsorption efficiency, excellent stability and good recycling performance make M-EG an ideal candidate for treating marine oil pollution in practical application. Display omitted
•The modified Expanded graphite was successfully synthesized via an Energy saving method.•The resultant obtained an interconnected microstructure with lower polarity surface and increased surface hydrophobicity.•The resultant exhibited a superior adsorption capacity towards different oil with good recyclability.
