The cobalt ferrite loaded on multi-walled carbon nanotubes (MWCNTs-CoFe₂O₄) was synthesized and used as a novel catalyst for the degradation of mefenamic acid (MFA) in the presence of peroxymonosulfate (PMS). The results showed that MWCNTs-CoFe₂O₄ has higher catalytic performance in the activation of PMS and degradation of MFA compared with MWCNTs, Co²⁺, Fe²⁺, and CoFe₂O₄. The highest kinetic constant rate (0.0198 min⁻¹) and MFA degradation (97.63%) were obtained at pH = 7, PMS = 4 mM, catalyst = 500 mg/L, MFA = 10 mg/L, and time = 150 min. MFA degradation accelerated with increasing PMS and catalyst dosage but decreased by initial pH. The influence of different anions and water matrix on the catalytic system was investigated, and the results explained a decrease in the MFA rate in the presence of the interfering substances. Scavenging experiments showed that both sulfate radical anion (SO₄•⁻) and hydroxyl radical (•OH) were effective on MFA degradation, but SO₄•⁻ had a greater effect on the degradation of MFA. In addition, the stability and recyclability of MWCNTs-CoFe₂O₄ were evaluated in the consecutive reaction cycle; the MFA degradation rate reached 89.75% after 4 cycles of reaction. The MFA degradation products were identified by gas chromatography-mass spectrometry (GC-MS) and their degradation pathway was suggested. Finally, a comparison was conducted among the methods used for PMS activation, and the results showed that the cobalt ferrite-based catalyst has high degradation efficiency. However, ultrasound, heat, and ultraviolet (UV) processes can be used to improve the degradation rate of the MWCNTs-CoFe₂O₄/PMS system at different reaction times.

The study investigates the correlation of CO₂ absorption performance and electrical properties in a tri-ethanolamine (TEA) aqueous solution compared to the mono-ethanolamine (MEA) and di-ethanolamine (DEA) systems. While the absorption rate of the MEA and DEA systems varies with amine concentration, and the maximum rate is observed at 30.0 and 50.4 wt% amine solution, respectively, the rate of the TEA system according to concentration follows a parabolic curve and the maximum rate is observed at 15.0 wt% solution. The ionic conductivity of carbamic acid in the TEA system is estimated to be the smallest with 37.60 S cm²/mol z and the decreasing ratio of ionic activity coefficient according to the concentration is the largest. The results are mostly attributed to differences in amine molecular structure and the unique reaction mechanism. Finally, based on these values, the correlation equations are obtained to estimate CO₂ absorption capacity by measuring electrical conductivity in situ.

The frequent occurrence of microcystins (MCs) in freshwater poses serious threats to the drinking water safety and health of human beings. Although MCs have been detected in individual fresh waters in China, little is known about their occurrence over a large geographic scale. An investigation of 30 subtropical lakes in eastern China was performed during summer 2018 to determine the MCs concentrations in water and their possible risk via direct water consumption to humans, and to assess the associated environmental factors. MCs were detected in 28 of 30 lakes, and the highest mean MCs concentrations occurred in Lake Chaohu (26.7 μg/L), followed by Lake Taihu (3.11 μg/L). MC-LR was the primary variant observed in our study, and MCs were mainly produced by Microcystis, Anabaena (Dolicospermum), and Oscillatoria in these lakes. Replete nitrogen and phosphorus concentrations, irradiance, and stable water column conditions were critical for dominance of MC-producing cyanobacteria and high MCs production in our study. Hazard quotients indicated that human health risk of MCs in most lakes was at moderate or low levels except Lakes Chaohu and Taihu. Nutrient control management is recommended to decrease the likelihood of high MCs production. Finally, we recommend the regional scale thresholds of total nitrogen and total phosphorus concentrations of 1.19 mg/L and 7.14 × 10⁻² mg/L, respectively, based on the drinking water guideline of MC-LR (1 μg/L) recommended by World Health Organization. These targets for nutrient control will aid water quality managers to reduce human health risks created by exposure to MCs.

Degradation-resistant chemical contaminants of health concern such as dichlorodiphenyltrichloroethane (DDT) pesticides and polychlorinated biphenyls (PCBs) in the environment are redistributed between different environmental compartments, where they partition between biotic heterotrophic routes and abiotic features (water and immobile soil components). Their fate and the potential risk they pose is a function of translocation, interaction, environmental behavior, and bio-translation/activities. In this study, the partitioning, translocation, bio-translation pathways of 3-DDT and 6-PCB congeners in dosed soils cultured root and leaf vegetables were investigated to predict their soil–vegetable mobility, depuration, and exposure risk. Results showed that PCB_110 and PCB_180 were the least and highest PCBs concentrated in both the leaf and root vegetables. The variations in the 3-DDT and 6-PCB concentrations in the leaf and root vegetables may be attributed to differences in their solubility and partitioning. Total residual mass fraction 3-DDT taken up by the leaf and root vegetables indicated time-dependent preferentiality in pesticide-type vascular tissue translocation to the vegetables. Mann–Whitney non-parametric test showed evidence of spatial variations in levels of the 3-DDT and 6-PCBs across the farmland; however, the variations in the distribution were not significant (PFML₁–FML₆ <<Pₛₜₐₜ). Risk factors for 3-PCBs and 3-DDT tend to 1(f < 1.0), while that for PCBs_149, 153, and _180 were far less than 0.4 (<1.0). It is therefore uncertain that any immediate health risks could arise from exposure to vegetables containing such congener levels. Continuous exposure to an extrapolated estimate of 25% vegetable population has a 20 ± 10% probability of leading to undesirable chronic effects.

The evaluation of the concentration of pesticides in drinking water presents a real concern. In this study, a simple and rapid method based on solid-phase microextraction (SPME) followed by gas chromatography–mass spectrometry and electron capture detectors was developed aiming at multiclass determination of 23 pesticides regulated by the Brazilian legislation. The extraction was carried out by direct immersion mode (DI-SPME) using DVB/Car/PDMS fiber coating. In order to improve the extraction efficiency, parameters such as temperature, salting-out effect, and extraction time were optimized. The method was evaluated using drinking water samples spiked with the analytes at different concentrations, and it showed good linearity in the range studied. The values obtained for limits of quantification (LOQ) were below the limits established by Brazilian regulations. Accuracy and precision of the method exhibited satisfactory results, providing relative recoveries from 70 to 123.34% at three spiked levels, and the relative standard deviations ranged from 0.53 to 24.8%. The method was applied in 20 drinking water samples from 13 cities in the State of Santa Catarina, Brazil.

Carbon nano-onions (CNOs) are fascinating zero-dimensional carbon materials owning distinct multi-shell architecture. Their physicochemical properties are highly related to the parent material selected and the synthesis protocol involved. In the present work, we report for the first time novel CNO structures encompassing discrete carbon allotropes, namely, H₁₈ carbon, Rh6 carbon, and n-diamond. These structures were cost-effectively synthesized in gram scale by facile flame pyrolysis of paraffinum liquidum, a highly refined mineral oil. The as-synthesized and chemically refashioned CNOs are quasi-spherical self-assembled mesopores, manifesting remarkable stability and hydrophilicity. The CNO structures exhibit excellent dye adsorption characteristics with high removal capacity of 1397.35 mg/g and rapid adsorption kinetics with a minimal adsorbent dosage of 10 mg/L, for a low concentration of 20 mg/L methylene blue dye. The novel CNOs assure potential implementation in the remediation of low concentration and high volume of dye-contaminated wastewater.Graphical abstract

Remanufacturing and energy performance contracting (EPC) have attracted much attention recently because of their potential to reduce energy consumption and achieve sustainable production. In this paper, taking carbon emission trading (CET) into consideration, we discussed how EPC affected manufacturer production decision-making. We constructed an optimal production model and analyzed the manufacturer’s production decision-making, parameter sensitivity, and economic and environmental effects. Our findings included (1) the implementation of EPC increased the output of new products and the manufacturer’s profits. However, EPC did not effectively stimulate remanufacturing, and could increase carbon emissions; (2) CET could alleviate the adverse effect of EPC on remanufacturing and decrease carbon emissions, but may also decrease the total output; and (3) under certain conditions, CET combined with EPC could reduce carbon emissions while increasing the output of remanufactured products and manufacturer’s profits. The conclusions of this paper could help the manufacturer to make rational operational decisions and achieve sustainable production.

Conventional chemical soil amendments and novel material biochars have been widely reported for the immobilisation of cadmium (Cd) and lead (Pb) in polluted soil. However, information regarding their comparative effectiveness is poor. In the present study, rice husk biochar (RHB) was compared with two chemical soil amendments including hydroxyapatite (HAP) and hydrated lime (HDL) for their effectiveness to enhance plant growth and the reduction of Cd uptake and translocation by Triticum aestivum L. grown in heavy-metal-polluted soil. Compared with control and two chemical soil amendments, RHB rapidly improved wheat growth. The HAP, HDL, and RHB treated plants retained Cd and Pb in roots and restricted their translocation. The RHB treatment had the best effect on growth, yield promotion and the reduction of Cd and Pb in wheat grain. Furthermore, the soils treated with RHB and HAP showed lower DTPA-extracted Cd concentrations, and the maximum reduction was observed in HAP-amended soil. However, the DTPA-extracted Pb concentration was not significantly decreased after the application of two chemical soil amendments for 40 days; the maximum reduction was found in soil treated with RHB for 80 days. In all treatments, Cd in post-harvest soil was mainly present in exchangeable, carbonate bound, and Fe-Mn oxide Cd, while the dominant chemical form of Pb was Fe-Mn oxide Pb. Three soil amendments application decreased exchangeable and organic bound- Cd and Pb levels. HAP and RHB displayed significantly immobilisation for soil Cd and reduced translocation of heavy metal as well as its availability in soil, but the HAP had significant inhibition on growth of wheat in contaminated soil. Therefore, RHB shows a promising potential for the reduction of Cd and Pb bioaccumulation in grains from wheat grown on heavy-metal-polluted soils.

Río Tercero Reservoir (RTR) is the largest artificial reservoir in the province of Córdoba (Argentina). Water, sediment, plankton, shrimp (Palaemonetes argentinus), and fish (Odontesthes bonariensis) were collected during the wet season (WS) and dry season (DS) from this reservoir. Concentrations of Ag, Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, P, Pb, Se, U, and Zn were determined to investigate their respective bioaccumulation pattern and trophic transfer in the food chain. Results showed that their concentrations in water were rather low except Pb, which exceed the limits considered as hazardous for aquatic life. The enrichment factor (EF) in sediments showed that most of the element were derived from anthropogenic sources. Furthermore, the bioaccumulation factor (BAF) determined that the elements undergo bioaccumulation, especially in organisms such as plankton. The invertebrates were characterized by the highest BAF for Cu, P, and Zn in both seasons; Ag, As, and Hg during WS; and Se during DS. Fish muscle registered the highest BAF for Hg (DS) and Se (WS). A significant decrease in Al, As, Cd, Cr, Cu (DS) Fe, Mn, Ni, Pb, Se, U, and Zn (DS) concentrations through the trophic chain was observed, indicating biodilution. Some notable exceptions were found as Cu (WS), Hg (DS), and P (both season) that showed biomagnification. Further studies are needed to establish differential behavior with different species and pollutant, particularly when the potential transfer is to edible organisms.

In this study, graphene oxide (GO) was prepared using modified Hummer’s method and doped with Fe-Ni nanoparticles. Morphological characterization of the Fe-Ni nanoparticles showed flake-like structure correlating to taenite phase, while Raman spectroscopy suggested that graphene oxide was multi-layered. Batch adsorption experiments were performed to determine the effect of solution pH, initial uranium (VI) concentration, adsorbent dosage, contact time, and specific anions (SO₄²⁻ and NO₃²⁻) on the adsorption of U (VI). Solution pH had significant effect on U (VI) sorption on Fe-Ni/GO, with maximum removal of 98.4% at pH 4, while it was 98% at pH 8 for GO. Sorption kinetics revealed fast adsorption within 15 min. The kinetic and equilibrium data was evaluated using pseudo-first-order, pseudo-second-order, Elovich, Langmuir, Freundlich, and Temkin models. The mechanism of U (VI) sorption appeared to be a combination of chemisorption and possible pore diffusion of the U (VI) moieties to the porous structure of GO and Fe-Ni/GO. Overall, Fe-Ni/GO was a better adsorbent than GO with higher sorption capacities. U (VI) sorption on GO and Fe-Ni/GO followed pseudo-second-order reaction kinetics (R² > 0.99). Good fit to Langmuir isotherm model (R² > 0.98) suggested favorable monolayer adsorption, with a maximum U (VI) adsorption capacity on Fe-Ni/GO to be 25.64 mg/g. Moderate to insignificant effect of specific anions even at high concentrations on U (VI) removal capacities makes Fe-Ni/GO an excellent candidate.