Nitrogen-doped porous carbon (NPC) is synthesized through a direct pyrolysis of zeolitic imidazolate framework (ZIF)-8 under N₂ flow followed by acid washing process. It is found that NPC-800 pyrolyzed at 800 °C can inherit the perfect rhombic dodecahedron morphology of ZIF-8 crystals and achieve the considerable nitrogen-doping content of 15.20%. When NPC-800 is applied as the heterogeneous catalyst in peroxymonosulfate (PMS) activation for the degradation of Rhodamine B (RhB) and phenol, NPC-800 will exhibit its better performance than some conventional transition metal-based oxides and common carbon materials. The active sites can be primarily ascribed to nitrogen modification and sp ²-hybridized carbon frameworks. Besides, the influence of several parameters such as the dosage of catalyst, the concentration of oxidant, and reaction temperature is conducted systematically. More importantly, NPC-800 can maintain its considerable degradation in the presence of some anions and natural organic matters, even under some actual water background conditions. Although NPC-800 displays mild deactivation in repeated experiments, its catalytic performance can be easily recovered through heat treatment at 350 °C in air. Radical quenching tests reveal that both sulfate and hydroxyl radicals are responsible for the removal of organic pollutants. This research may provide a new way for the application of novel metal-free carbocatalysts in terms of PMS activation.

The effect of varied concentrations of thermal-treated oyster shells (TOS) on the suppression of cadmium (Cd) and copper (Cu) uptake and translocation into the shoots of maize plants was examined. Maize plants were grown in Cd- and Cu-contaminated Andosol for 70 days. The concentration of mobile Cd (extracted with 1 M NH₄NO₃) decreased with increasing TOS applications, whereas an increase in the concentration of mobile Cu in soil resulted from cumulative TOS additions. The addition of 2% TOS had no prohibitive effects on Cd uptake in maize shoots, but the 4 and 8% TOS treatments decreased Cd accumulation in shoots by 41 and 59%, respectively. The possible mechanisms underlying Cd suppression in maize shoots were the enhanced Cd adsorption caused by pH-induced increases in the negative charge of the soil and the antagonistic effects of Ca resulting from competition for exchange sites at the root surface. Cu accumulation in maize shoots increased by 34, 51, and 53% with the addition of 2, 4, and 8% TOS, respectively, but this increase was not observed for Cd accumulation. These results suggested that, in multi-metal-contaminated soils, attention should be paid to the potential mobility of target metals and the pH of the contaminated soil. From a plant physiological perspective, contaminated soils slightly reduced photosynthetic performance. However, the addition of TOS to the soil at levels higher than 4% substantially decreased photosynthetic performance, indicating that CaO-based suppressants at critical loads might damage the net photosynthetic rates of sensitive maize plants.

The present study investigated the intertissue differences in genotoxicity induction in the fish, Channa punctatus, in response to 4-nonylphenol. The lethal concentration of 50 (LC₅₀) was estimated using a semi-static system. Fish were subjected to three sublethal concentrations of 4-nonylphenol (NP) for 24, 48, 72, and 96 h. Liver, gill, and kidney tissues were analyzed, and the genotoxicity was estimated using the micronucleus test and the comet assay. The frequency of micronucleated cells (MNCs), binucleated cells (BNCs), aberrant cells, and tail moment (TM) increased significantly. The time for maximum induction of genotoxicity for all the parameters considered in the micronucleus assay was 72 h of exposure, whereas the TM was highest at 24 h of exposure followed by a decline. The gill and liver showed higher genotoxicity than kidney tissue demonstrating organ-specific susceptibilities to NP in fish C. punctatus.

To develop highly efficient and conveniently separable iron containing catalysts is crucial to remove recalcitrant organic pollutants in wastewater through a heterogeneous Fenton-like reaction. A maghemite/montmorillonite composite was synthesized by a coprecipitation and calcination method. The physiochemical properties of catalysts were characterized by XRD, TEM, nitrogen physisorption, thermogravimetric analysis/differential scanning calorimetry (TG/DSC), zeta potential, and magnetite susceptibility measurements. The influence of calcination temperatures and reaction parameters was investigated. The calcined composites retain magnetism because the presence of montmorillonite inhibited the growth of γ-Fe₂O₃ nanoparticles, as well as their phase transition. The catalytic activities for phenol degradation were significantly enhanced by calcinations, which strengthen the interaction between iron oxides and aluminosilicate framework and result in more negatively charged surface. The composite (73 m²/g) calcined at 350 °C had the highest catalytic activities, with more than 99 % phenol reduction after only 35 min reaction at pH 3.6. Simultaneously, this catalyst exhibited high stability, low iron leaching, and magnetically separable ability for consecutive usage, making it promising for the removal of recalcitrant organic pollutants in wastewater.

The main aim of this article is to examine empirically the impact of urbanization on carbon dioxide emissions in Singapore from 1970 to 2015. The autoregressive distributed lags (ARDL) approach is applied within the analysis. The main finding reveals a negative and significant impact of urbanization on carbon emissions in Singapore, which means that urban development in Singapore is not a barrier to the improvement of environmental quality. Thus, urbanization enhances environmental quality by reducing carbon emissions in the sample country. The result also highlighted that economic growth has a positive and significant impact on carbon emissions, which suggests that economic growth reduces environmental quality through its direct effect of increasing carbon emissions in the country. Despite the high level of urbanization in Singapore, which shows that 100 % of the populace is living in the urban center, it does not lead to more environmental degradation. Hence, urbanization will not be considered an obstacle when initiating policies that will be used to reduce environmental degradation in the country. Policy makers should consider the country’s level of economic growth instead of urbanization when formulating policies to reduce environmental degradation, due to its direct impact on increasing carbon dioxide emissions.

Temporary streams are characterised by specific hydrological regimes, which influence ecosystem processes, groundwater and surface water interactions, sediment regime, nutrient delivery, water quality and ecological status. This paper presents a methodology to characterise and classify the regime of a temporary river in Southern Italy based on hydrological indicators (HIs) computed with long-term daily flow records. By using a principal component analysis (PCA), a set of non-redundant indices were identified describing the main characteristics of the hydrological regime in the study area. The indicators identified were the annual maximum 30- and 90-day mean (DH4 and DH5), the number of zero flow days (DL6), flow permanence (MF) and the 6-month seasonal predictability of dry periods (SD6). A methodology was also tested to estimate selected HIs in ungauged river reaches. Watershed characteristics such as catchment area, gauging station elevation, mean watershed slope, mean annual rainfall, land use, soil hydraulic conductivity and available water content were derived for each site. Selected indicators were then linked to the catchment characteristics using a regression analysis. Finally, MF and SD6 were used to classify the river reaches on the basis of their degree of intermittency. The methodology presented in this paper constitutes a useful tool for ecologists and water resource managers in the Water Framework Directive implementation process, which requires a characterisation of the hydrological regime and a ‘river type’ classification for all water bodies.

Parent and aluminum-modified eggshells were prepared and characterized with X-ray diffraction, specific surface area measurements, infrared spectroscopy, zeta potential, and scanning electron microscope, respectively. Besides, phosphorus adsorptions in these two eggshells at different temperatures and solution pH were carried out to study adsorption thermodynamics and kinetics as well as the mechanisms of phosphorus adsorption and diffusion. The results indicated that high temperature was favorable for phosphorus adsorption in parent and aluminum-modified eggshells. Alkaline solution prompted phosphorus adsorption in parent eggshell, while the maximum adsorption amount was achievable at pH 4 in aluminum-modified eggshell. Adsorption isotherms of phosphorus in these eggshells could be well described by Langmuir and Freundlich models. Phosphorus adsorption amounts in aluminum-modified eggshell were markedly higher compared to those in parent eggshell. Adsorption heat indicated that phosphorus adsorption in parent eggshell was a typically physical adsorption process, while chemical adsorption mechanism of ion exchange between phosphorus and hydroxyl groups on the surface of eggshells was dominated in aluminum-modified eggshell. The time-resolved uptake curves showed phosphorus adsorption in aluminum-modified eggshell was significantly faster than that in parent eggshell. Moreover, there existed two clear steps in time-resolved uptake curves of phosphorus in parent eggshell. Based on pseudo-second order kinetic model and intraparticle diffusion model, we inferred more than one process affected phosphorus adsorption. The first process was the diffusion of phosphorus through water to external surface and the opening of pore channel in the eggshells, and the second process was mainly related to intraparticle diffusion.

Solar photocatalytic disinfection efficiency of novel visible light activated (VLA) photocatalysts was evaluated with the aim of assessing inactivation of Escherichia coli as the pathogen indicator organism present in drinking water. Influence of humic acid (HA) on the photocatalytic disinfection efficiency of the specified VLA TiO₂ specimens i.e., N-doped, Se-doped, and Se-N co-doped TiO₂ was also investigated. Photocatalytic disinfection efficiency was assessed by the enumeration of bacteria following selected irradiation periods. Degradation and compositional changes in organic matter (OM) was also tracked by means of UV-vis and advanced fluorescence spectroscopic (EEM features) parameters. Photocatalytic mineralization of the organic matter was followed by dissolved organic carbon contents. Presence of HA as a model organic compound of natural organic matter (NOM) displayed a retardation effect on solar photocatalytic abatement of E. coli. However, no distinctly different effect was observed under solar photolytic conditions due to the presence of HA. Regrowth of E. coli could not be assessed under the specified experimental conditions. A comparison was introduced with respect to the use of undoped TiO₂ P-25 as the photocatalyst.

Emerging contaminants including pharmaceuticals are a class of compounds that are causing great concern due to several environmental problems. Conventional water and wastewater treatments do not achieve high removal efficiencies for many of these drugs. Therefore, the present work investigated the removal of ibuprofen (IBP) by heterogeneous photocatalysis using TiO2 irradiated with artificial UV light or solar radiation. The treated solutions were tested against Daphnia similis and Raphidocelis subcapitata, which are species commonly used as bioindicators of environmental conditions. The results indicated that IBP removal reached 92% after 1 h of treatment using artificial UV and 1000 mg L⁻¹ of TiO₂, which was the optimum catalyst concentration in the range studied (20–1000 mg L⁻¹). TOC removal reached up to 78% after 60 min of treatment using TiO₂/artificial UV. Ecotoxicological bioassays indicated that the treated solutions had acute effects, with 30% immobilization of D. similis and 40% growth inhibition of R. subcapitata.