The objective of this study was to impregnate the surface of palm coconut activated carbon with nanoparticles of iron compounds using Moringa oleifera leaf extracts and pomegranate leaf by a green synthesis method and to evaluate its adsorption capacity for sodium diclofenac. The adsorbent material was characterized by zeta potential, X-ray diffraction (XRD), N₂ adsorption/desorption (BET method), transmission electronic microscopy (TEM), and scanning electronic microscopy (SEM) coupled to dispersive energy spectrometry X-ray (EDX) methods. To evaluate the adsorption capacity of sodium diclofenac, the influence of pH, kinetics, isotherms, and thermodynamic properties were analysed. The impregnated adsorbents showed efficiency in the adsorption of sodium diclofenac. The kinetic model that best fit the experimental data was the pseudo-second-order model, and the equilibrium model was the Langmuir model. As for the thermodynamic study, it was verified that the adsorption reaction for all adsorbents occurs in a spontaneous, favourable way, and it is endothermic by physisorption. Therefore, this process is promising because it is a clean and non-toxic method when compared with chemical methods for the synthesis of nanoparticles.

Metal organic frameworks (MOFs) are excellent adsorbents that provide abundant specific surface area, adjustable pore structure, and rich active sites. The purpose of this study was to prepare composites with hydrophobic and high microporous specific surface area and to adsorb toluene gas in moist ambience. An ethanol activation-assisted hydrothermal method was proposed to synthesize copper-benzene-1,3,5-tricarboxylic acid (Cu-BTC) metal-organic framework, Cu-BTC, and ZSM-5 molecular sieve composites (Cu-BTC@ZSM-5). The dynamic adsorption process of toluene on different adsorbents was investigated, and the results showed that the toluene adsorption capacity of Cu-BTC@ZSM-5 (158.6 mg/g) was 2.53 times higher than Cu-BTC (62.7 mg/g), when the ZSM-5 content is 5% and the humidity is 30%RH. Compared with other factors, the humidity inhibited the adsorption of toluene on Cu-BTC@ZSM-5. Langmuir model and the pseudo-second kinetics model can better describe the adsorption behavior of Cu-BTC@ZSM-5. The thermodynamic results showed the adsorption process was a spontaneous exothermic process at low temperature and mainly physical adsorption. The relative regenerability can still up to 80.4% after six cycles. The adsorption mechanisms of Cu-BTC@ZSM-5 were pore-filling adsorption, π-π interaction, cation-π bonding, and hydrophobic interactions. This study will help to design a systematic route to evaluate the adsorption performance of Cu-BTC@ZSM-5 for toluene.

How to reasonably manage and reutilize the waste expired liquid medicines has always been a puzzling public concern. For this reason, the waste expired medicine of donkey-hide gelatin pulp was recycled by hydrothermal carbonization and hard template for N/S co-doped hard carbon material, and its electrochemical Na-storage performances were also evaluated. The results showed that the resultant N/S co-doped hard carbon material manifested the morphology of hollow nano-spheres with the mean diameter of about 242.3 nm and the shell thickness of about 15 nm; N and S elements evenly distributed in carbon structure by in situ co-doping. Furthermore, N/S co-doped hard carbon also delivered the satisfactory electrochemical Na-storage capacities due to the synergistic effect of the unique hollow nano-spheres with thin shell and N/S co-doping. No doubt, the results would promote the circular economy mode of waste expired medicines.

The purpose of this study is to examine the role of economic structure of European countries into testing the Environmental Kuznets Curve (EKC) hypothesis for European countries for the period 1980 to 2014. This study is inspired by the work of Lin et al. (J Clean Prod 133:712–724, 2016), which made the first effort to investigate the phenomenon looking only at African countries. The main finding of the study is that the overall economic growth is the factor with which CO₂ emissions exhibit an inverted U-shaped relationship in the studied country group. On the contrary, when using their industrial share as a proxy to capture the countries’ economic structure, the EKC hypothesis is not confirmed – but a U-shaped relationship is confirmed. The industrial share decreases emissions through the development and absorption of technologies that are energy efficient and environmental friendly. The EKC hypothesis is confirmed when the aggregate GDP growth is considered, taking into account the improvement of the overall economic conditions of the countries regardless of the economic structure and role of industrialization.

In the process of electrokinetic (EK) remediation of uranium-contaminated soil, the existence form of uranium in soil pore fluid will affect on its migration behavior. In this paper, a novel type of electrolyte (citric acid + ferric chloride, CA+ FeCl₃) has been investigated for the EK remediation of uranium-contaminated red soil. The effects of different electrolyte and the concentrations of FeCl₃ on migration behavior of U(VI) and environmental risks were investigated after EK remediation. The result showed that the optimum concentration was 0.1 mol/L CA mixed with 0.03 mol/L FeCl₃ in this study. At this time, the removal efficiency of uranium was about 61.55 ± 0.41%, and the cumulative energy consumption was 0.2559 kWh. Compared with deionized water and single CA, combined CA with FeCl₃ has the advantages of high removal efficiency, low leaching toxicity, and less damage to the soil after the electrokinetic remediation treatment.

Tannery sludge (TS) contains high levels of organic matter and chemical elements, mainly chromium (Cr). This can increase its toxicity, rendering it unsuitable for application to soil. However, composting has been proposed as an alternative method for detoxifying TS before its addition to soil. Thus, the aim of this study was to evaluate the phytotoxic and cytogenotoxic potential of untreated (TS) and composted (CTS) tannery sludge in solid and solubilized samples. Seed germination and root growth bioassays were performed with Lactuca sativa, while chromosomal aberrations were assessed using the Allium cepa bioassay. In solid samples, the L. sativa bioassay showed that TS adversely affected germination and root growth, while CTS had a negative affect only on root growth. In solubilized samples, only TS showed significant adverse effects on seed germination and root growth. In both solid and solubilized samples, TS and CTS showed cytotoxic, genotoxic, and mutagenic effects on A. cepa. Thus, results demonstrated that the composting of TS does not result in its complete detoxification. For this reason, TS and CTS cannot be recommended for agricultural use, since they may increase the risk of environmental contamination and crop damage.

This study uses a combined data envelopment analysis and logarithmic mean Divisia index (DEA-LMDI) method to decompose affecting factors for PM₂.₅ emissions into effects related to the potential emission intensity (PEI), environmental efficiency and technology, production efficiency and technology, regional economic structure, and national economic growth, and investigates differences in the effects on PM₂.₅ emissions, considering the diversity among different areas and periods in China. This study provides a new insight in the decomposition method, which can decompose the emissions into new effects compared with the exiting studies. This study reveals that the regional environmental-based technology (EBT) effect is the key curbing factor for PM₂.₅ emissions, followed by the regional PEI effect. The curbing effect of regional EBT on PM₂.₅ emissions is strong in East China and weak in Northeast China. The environment-oriented scale efficiency (ESE), environment-oriented management efficiency (EME), production-oriented scale efficiency (PSE), production-oriented management efficiency (PME), and production-based technology (PBT) had relatively small effects on PM₂.₅ emissions on the whole. The effects differ among different areas and periods in China. The emission reduction potential of these efficiency effects has not been realized. The national economic growth greatly promotes PM₂.₅ emissions. The regional economic structure effect slightly increases PM₂.₅ emissions because of the unbalanced development of regional economy. The relative policy suggestions are put forward based on the findings of this study.

Pyroligneous acids can be used in herbicides, but the dosage used often more than 1000 kg ha⁻¹. Five treatments including the application of bamboo, wood, straw vinegar, acetic acid and sulphuric acid at high dosages sprayed once every 6 days, for a total of 3 times. We then continuously monitored the changes in soil pH, moisture content and the activities of three soil hydrolase enzymes involving in urease, protease and sucrase. We found that after 1~3 days of spraying with all 5 kinds of acid, the soil pH was not immediately reduced, but from 3 days after application onward it was reduced by a maximum of 1.54~1.75, which showed that the soil had some buffering capacity. Over time, the pH began to return to the water control pH value, which showed that the soil also had good restorative capacity. After the second and third times of spraying, the pH change measured showed no cumulative effect, which demonstrated that the soil had adaptive capacity. We accidentally found that bamboo vinegar could improve the soil pH by a maximum of 0.65~1.02, while the other four acids reduced its pH. Bamboo vinegar was found to contain the 6 compounds while wood and straw vinegar contained none of these compounds. These compounds may be a new potential reagent(s) for improving the pH. Three soil sample processing methods tested for determining pH, including the moist soil test, oven-dry soil test and air-dried soil test, all produced extremely and significantly different pH values. Five acids were unable to significantly improve the water holding capacity of the soil; they had adverse effects on the activity of the urease enzymes while beneficial effects on the protease and sucrase enzymes. Therefore, pyroligneous acid and acetic acid have no effects on soil health as herbicides.

Occupational and environmental exposures to carbon-based materials in nano- and micro-size have been reported. There is incomplete information on the impact of size on the toxicity of carbon-based materials. The objective of this study is to compare the toxicity of graphite, short multi-walled carbon nanotubes (S-MWCNTs), and long multi-walled carbon nanotubes (L-MWCNTs) in lung cells (A 549). The physicochemical properties of MWCNTs were determined using analytical instruments. The fibers of MWCNTs were dispersed in the sterile-filtered 0.05% bovine serum albumin in MilliQ water. Cytotoxicity of graphite and MWCNTs were assessed using the cell viability, reactive oxygen species (ROS), and lipid peroxidation experiments. Results showed that MWCNTs induced cytotoxicity through the generation of oxidative stress in the exposed lung cells. Mean cytotoxicity of S-MWCNTs was statistically more than that of L-MWCNTs. The graphite induced cytotoxicity only at high concentrations. The mean cytotoxicity of both S-MWCNTs and L-MWCNTs was statistically more than that of graphite. The results also indicated that oxidative stress was the probable toxicity mechanism of carbon-based materials. The decreasing size of carbon-based materials could increase their toxicity. Because of the toxicity of MWCNTs, it is imperative to consider health and safety issues in working with nanomaterials.

The discussers wish to thank the authors of the original paper for investigating the comparing accuracy of artificial intelligence techniques trained to predict chlorophyll-a in US lakes. In the original paper (Luo et al., Environ Sci Pollut Res 26: 30524–30532, 2019), four data-driven models were established to estimate the chlorophyll-a (CHLA) values in natural and man-made lakes. Three of these models are adaptive neuro-fuzzy inference system (ANFIS)-based, while one is (artificial neural network) ANN-based. The authors used total phosphorus (TP), total nitrogen (TN), turbidity (TB), and the Secchi depth (SD) as independent variables in order to predict CHLA. They stated that ANFIS with subtractive clustering method (ANFIS_SC) models and multilayer perceptron neural network (MLPNN) models gives higher accuracy in the prediction of CHLA values for natural lakes and man-made lakes, respectively. In this letter, some of the missing points in the original publication, which is important for the estimation and comparison of CHLA values in two different lake sets that differ according to the type of formation, are highlighted. In addition, several points are mentioned in order to make these points more clarified for potential readers.