The adsorption of inorganic arsenic (As) plays an important role in the mobility and transport of As in the river environment. In this work, the adsorption and desorption of arsenite As(III) and ...arsenate As(V) on river sediment were conducted under different pH, initial As concentrations, river water and sediment composition to assess As adsorption behavior and mechanism. Both adsorption kinetics and equilibrium results showed higher adsorption capacity of sediment for As(V) than As(III). Adsorption of As(III) and As(V) on river sediment was favored in acidic to neutral conditions and on finer sediment particles, while sediment organic matter marginally reduced adsorption capacity. In addition, higher adsorption affinity of As(III) and As(V) in river sediment was observed in deionised water than in river water. For the release process, the desorption of both As(III) and As(V) followed nonlinear kinetic models well, showing higher amount of As(III) release from sediment than As(V). Adsorption isotherm was well described by both Langmuir and Freundlich models, demonstrating higher maximum adsorption capacity of As(V) at 298.7 mg/kg than As(III) at 263.3 mg/kg in deionised water, and higher maximum adsorption capacity of As(III) of 234.3 mg/kg than As(V) of 206.2 mg/kg in river water. The XRD showed the changes in the peaks of mineral groups of sediment whilst FTIR results revealed the changes related to surface functional groups before and after adsorption, indicating that Fe–O/Fe–OH, Si(Al)–O, hydroxyl and carboxyl functional groups were predominantly involved in As(III) and As(V) adsorption on sediment surface. XPS analysis evidenced the transformation between these As species in river sediment after adsorption, whilst SEM-EDS revealed higher amount of As(V) in river sediment than As(III) due to the lower signal of Al.
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•Sediment surface functional groups were involved in As adsorption.•There was transformation between As species on sediment.•Adsorption kinetics followed the pseudo first- and second-order models.•Adsorption equilibria were well fitted by the Langmuir and Freundlich isotherms.•Fine sediment fractions significantly enhanced As(III) and As(V) adsorption.
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•Underground PM concentrations were higher than ground level by 2.8 times.•Ground level PM concentrations were affected by ambient background sources.•Main source of underground PM ...was from railway.•Underground PM concentrations exceeded national standards.•Fe was abundant in PM samples with PI value of 19.2 and EF value of 61.3.
Sampling campaign was conducted over six weeks to determine particulate matter (PM) concentrations from Sydney Trains airport line (T2) at both underground and ground levels using DustTrak. Dust samples were collected and analysed for 12 metals (Fe, Ca, Mn, Cr, Zn, Cu, Pb, Al, Co, Ni, Ba and Na) by atomic emission spectroscopy. Average underground PM10 and PM2.5 concentrations from inside the trains were 2.8 and 2.5 times greater than at ground level. Similarly, PM10 and PM2.5 concentrations on underground platforms were 2.7 and 2.5 times greater than ground level platforms. Average underground PM concentrations exceeded the national air quality standards for both PM10 (50 µg/m3) and PM2.5 (25 µg/m3). Correlation analysis showed a strong to moderate association between PM concentrations at ground level and background PM concentrations (r2 from 0.952 to 0.500). The findings suggested that underground PM concentrations were less influenced by the ambient background than at ground level. The metal concentrations decreased in the order of Fe, Cr, Ca, Al, Na, Ba, Mn, Zn, Cu, Ni, Co and Pb. The pollution index (PI) and enrichment factor (EF) values were calculated to identify the levels and sources of contamination in the underground railway microenvironments. PM was remarkably rich in Fe with a mean concentration of 73.51 mg/g and EF of 61.31, followed by Ni and Cr. These results noticeably indicated a high level of metal contamination in the underground environments, with the principal contribution from track abrasion and wear processes.
Developing surfaces with special wettability inspired by biological surfaces has rapidly inspired these field of energy, environment and medical etc. Bioinspired makes natural surfaces have unique ...wetting characteristics. Immersed surface accumulation-based 3D printing to manufacture the microstructure of the superhydrophobic eggbeater with bionic structure. Due to its high degree of design freedom and excellent manufacturing flexibility, additive manufacturing is increasingly indispensable in surface and interface applications. This review additive manufacturing in applying droplet interface developed unique interfacial materials with particularly adaptable wettability, such as super anti-wetting surfaces (superhydrophobic and superoleophobic), innovative switchable surfaces, and water-collecting surfaces, by creating inspiration from natural surfaces and established a dedicated 3D printing material database to realize the development and screening of intelligent materials.
Arsenic (As) is a heavy metal that causes widespread contamination and toxicity in the soil environment. This article reviewed the levels of As contamination in soils worldwide, and evaluated how ...soil properties (pH, clay mineral, organic matter, texture) and environmental conditions (ionic strength, anions, bacteria) affected the adsorption of As species on soils. The application of the adsorption isotherm models for estimating the adsorption capacities of As(III) and As(V) on soils was assessed. The results indicated that As concentrations in contaminated soil varying significantly from 1 mg/kg to 116,000 mg/kg, with the highest concentrations being reported in Mexico with mining being the dominating source. Regarding the controlling factors of As adsorption, soil pH, clay mineral and texture had demonstrated the most significant impacts. Both Langmuir and Freundlich isotherm models can be well fitted with As(III) and As(V) adsorption on soils. The Langmuir adsorption capacity varied in the range of 22–42400 mg/kg for As(V), which is greater than 45–8901 mg/kg for As(III). The research findings have enhanced our knowledge of As contamination in soil and its underlying controls, which are critical for the effective management and remediation of As-contaminated soil.
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•Mining caused the most serious pollution of As in soils.•Physisorption is the dominating adsorption mechanism of As(III).•Chemisorption is the major adsorption mechanism of As(V).•As adsorption is well modelled by the Langmuir and Freundlich isotherms.•Soil management should be targeted at key soil properties and As speciation.
Photocatalysis is widely researched in water and wastewater treatment processes owing to its unique capacity in the potential mineralization of organic pollutants. Suspended nanoparticles provide ...high specific surface area, but their practical application has been very limited due to drawbacks such as catalyst agglomeration during treatment and difficulty of catalyst reuse after treatment. It is therefore of paramount importance to immobilize catalysts to realize continuous photocatalysis operations towards commercial scale, and surface engineering provides an ideal strategy to overcome the problems associated with using suspended nanoparticles. Of different semiconductors used for the photocatalytic degradation of organic pollutants, TiO2 is considered a benchmark photocatalyst with ZnO as a potential alternative. Hence, the scope of this research is to review the application of several surface engineering methods including physical vapor deposition, dip coating, spin coating, spray coating, and electrophoretic deposition in the immobilization of TiO2 and ZnO. Overall, electrophoretic deposition is considered very promising for the successful immobilization of photocatalysts, and sintering particularly is recommended to improve the adhesion strength of the as-deposited films, expediting the practical applications of photocatalysis through electrophoretic deposition.
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•Main techniques for the immobilization of TiO2 and ZnO coatings are reviewed.•Physical vapor deposition is suitable for the deposition of thin films.•Electrophoretic deposition is suitable for the deposition of thick and thin films.•Electrophoretic deposition is the most promising industrial method for coatings.•Sintering is necessary to increase the adhesion strength of deposited films.
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•PFASs removal efficacy and mechanism through advanced technologies are reviewed.•Electrochemical degradation was successful for removing PFASs.•Defluorination, thermal and ...non-thermal degradation systems show promising results.•Limitations include process costs and toxic gas by product formation.•New electrode materials and new processes need to apply for PFASs degradation.
The increasing occurrence of chemically resistant per- and poly-fluoroalkyl substances (PFASs) in the natural environment, animal tissues and even the human body poses a significant health risk. Temporal trend studies on water, sediments, bird, fish, marine mammal and the human show that the exposure of PFAS has significantly increased over the last 20–30 years. Different physical, biological and chemical treatment processes have been investigated for PFAS removal from water. However, there is a lack of detailed understating of the mechanism of removal by different methods, especially by different advanced chemical treatment processes. This article reviews PFASs removal efficacy and mechanism by the advanced chemical treatment methods from aqueous solution. Review shows that several advanced oxidation processes (e.g., electrochemical oxidation, activated persulfate oxidation, photocatalysis, UV-induced oxidation) are successful in degrading PFASs. Moreover, defluorination treatment, some thermal and non-thermal degradation processes are also found to be prominent for the degradation of PFASs with some limitations including process costs over physical treatment (e.g., sorption), production of toxic by-products and greenhouse gases. Finally, knowledge gaps concerning the advanced chemical treatment of PFASs are discussed.
Wastewater phosphorus (P) released into natural water bodies such as lakes and rivers, can cause water pollution as a result of eutrophication. If this P is effectively removed from wastewaters and ...economically recovered for use as fertilisers, not only can the water pollution be controlled, but also reduce the anticipated global shortage of P. This scarcity will result from the natural phosphate rock reserve being exhausted. Three experiments were conducted using membrane-bioreactor effluent (MBR, 35 mg PO4/L) and reverse osmosis concentrate (ROC, 10 mg PO4/L) waters to supply phosphate, and sea water (1530 mg Mg/L) to supply Mg for the production of struvite. The phosphate in the MBR and ROC was concentrated approximately 15 times by adsorption onto an ion exchange resin column followed by desorption. Struvite was precipitated by mixing the desorbed solution with seawater and NH4Cl. The chemical composition and mineral structure of the precipitates agreed with those of the reference struvite. When Ca in seawater (300 mg Ca/L) was removed before mixing the water with MBR or ROC, the purity of the struvite improved.
•Membrane bioreactor effluent is a good phosphate source for fertiliser production.•Struvite magnesium and phosphate supplied by seawater and wastewater, respectively.•Chemical composition and structure of struvite products matched standard struvite.•Pre-treatment involving calcium removal from seawater improved struvite quality.
Pharmaceuticals are widely used and often discharged without metabolism into the aquatic systems. The photocatalytic degradation of pharmaceutical compounds propranolol, mebeverine, and carbamazepine ...was studied using different titanium dioxide nanostructures suspended in water under UV and UV-visible irradiation. Among three different photocatalysts, the degradation was most effective by using Degussa P25 TiO
, followed by Hombikat UV100 and Aldrich TiO
. The photocatalytic performance was dependent on photocatalyst dosage, with an optimum concentration of 150 mg L
. The natural aquatic colloids were shown to enhance the extent of photocatalysis, and the effect was correlated with their aromatic carbon content. In addition, the photocatalysis of pharmaceuticals was enhanced by the presence of nitrate, but inhibited by the presence of 2-propanol, indicating the importance of hydroxyl radicals. Under optimum conditions, the pharmaceuticals were rapidly degraded, with a half-life of 1.9 min, 2.1 min, and 3.2 min for propranolol, mebeverine, and carbamazepine, respectively. In treating sewage effluent samples, the photocatalytic rate constants for propranolol (0.28 min
), mebeverine (0.21 min
), and carbamazepine (0.15 min
) were similar to those in water samples, demonstrating the potential of photocatalysis as a clean technology for the effective removal of pharmaceuticals from sewage effluent.
Pharmaceuticals are widely used and often discharged without metabolism into the aquatic systems. The photocatalytic degradation of pharmaceutical compounds propranolol, mebeverine, and carbamazepine ...was studied using different titanium dioxide nanostructures suspended in water under UV and UV-visible irradiation. Among three different photocatalysts, the degradation was most effective by using Degussa P25 TiOsub.2 , followed by Hombikat UV100 and Aldrich TiOsub.2 . The photocatalytic performance was dependent on photocatalyst dosage, with an optimum concentration of 150 mg Lsup.−1 . The natural aquatic colloids were shown to enhance the extent of photocatalysis, and the effect was correlated with their aromatic carbon content. In addition, the photocatalysis of pharmaceuticals was enhanced by the presence of nitrate, but inhibited by the presence of 2-propanol, indicating the importance of hydroxyl radicals. Under optimum conditions, the pharmaceuticals were rapidly degraded, with a half-life of 1.9 min, 2.1 min, and 3.2 min for propranolol, mebeverine, and carbamazepine, respectively. In treating sewage effluent samples, the photocatalytic rate constants for propranolol (0.28 minsup.−1 ), mebeverine (0.21 minsup.−1 ), and carbamazepine (0.15 minsup.−1 ) were similar to those in water samples, demonstrating the potential of photocatalysis as a clean technology for the effective removal of pharmaceuticals from sewage effluent.
In this study, response surface methodology (RSM) based on Box-Behnken design (BBD) was employed to optimize the aqueous extraction of crude polysaccharides from Tunisian cyanobacteria Phormidium ...versicolor (NCC 466). The optimal extraction conditions with an extraction yield of 21.56±0.92% were as follows: extraction temperature at 81.05°C, extraction time of 3.99h, and water to raw material ratio of 21.52mLg−1. Crude Phormidium versicolor polysaccharides (CPv-PS) are found to be a hetero-sulfated-anionic polysaccharides that contained carbohydrate (79.37±1.58%), protein (0.45±0.11%), uronic acids (4.37±0.19%) and sulfate (6.83±0.28%). The carbohydrate fraction was composed of arabinose, xylose, ribose, rhamnose, N-acetyl glucosamine, galactose, glucose, mannose, glucuronic acid and saccharose with corresponding mole percentages of 2.41, 14.58, 2.18, 6.23, 7.04, 28.21, 26.04, 3.02, 0.86 and 5.07, respectively. Evaluation of the antioxidant activity in vitro suggested that CPv-PS strongly scavenged radicals, prevented bleaching of β-carotene and reduced activity. Furthermore, the CPv-PS exhibited effective antimicrobial properties.
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