The bio-resource utilization of sewage sludge is presented by preparation of novel waste sludge–doped graphite carbon nitride (g-C₃N₄) photocatalyst. The sludge flocs which constitute bacteria and organic substances served as a pore-forming framework in the catalyst, while the inorganic fractions including those transition metals and crustal metals can function as dopants for sludge-based g-C₃N₄ composite. The physicochemical properties of as-prepared catalyst were well analyzed by multiple characterizations. The composite catalyst showed higher surface area (50 m²/g) and more mesoporous structures (8.9 × 10⁻² cm³/g) as compared with pristine g-C₃N₄ (8.4 m²/g and 6.6 × 10⁻² cm³/g, respectively). The photoelectrochemical results showed that introduced sewage sludge impurities lowered down the photocarriers recombination efficiency and enhanced more efficient electron-hole separation by about 100 times. The photocatalytic activity was tested by degradation of typical dye Eriochrome Black T (EBT). The optimal sample improved removal of EBT by 56% in 90 min under ultraviolet irradiation (λ = 254 nm). According to the results of main metal ion leaching concentration and reuse tests, the composite catalyst exhibited excellent stability and repeatability.

The present study demonstrates the development of polyphenol oxidase (PPO) biosensor for the detection of catechol using strontium copper oxide (SrCuO₂) and polypyrrole nanotubes (PPyNT) matrix. The SrCuO₂ micro-seeds, a perovskite compound, are synthesized by co-precipitation under pH 8.0. The as-synthesized micro-seeds are characterized by scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction spectroscopy (XRD). The proposed sensor is fabricated on pencil graphite (P-Gr) by successive deposition of PPyNT, SrCuO₂, and PPO enzyme. The developed PPO/SrCuO₂/PPyNT/P-Gr sensor is characterized by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) techniques. The PPO/SrCuO₂/PPyNT/P-Gr displayed excellent electrocatalytic activity towards the oxidation and detection of catechol. The as-developed sensor showed sensitive response ascribing to limit of detection (LOD) of 0.15 μM and sensitivity of 15.60 μA μM⁻¹ cm⁻². The fabricated sensor exhibited excellent repeatability and longer shelf life. The proposed biosensor finds its application within the broad linear range of 1–50 μM. Real sample analysis of mineral water, tap water, and domestic wastewater using developed sensor showed acceptable recovery. Hence, the biosensor endeavors its application in environmental monitoring and protection.

The occurrence, seasonal variation, and environmental impact of five widely used parabens, methyl-(MeP), ethyl-(EtP), n-propyl-(n-PrP), n-butyl-(n-BuP), and benzyl-(BzP) parabens, were investigated in a municipal wastewater treatment plant (WWTP) located in Guangzhou, China, for 1 year. The concentrations of ∑₅parabens in the influent and the effluent were 94.2–957 and 0.89–14.7 ng L⁻¹, respectively. The influent paraben concentrations in autumn were significantly lower than in winter, spring, and summer, and the concentrations were generally higher in spring. The removal efficiencies of ∑₅parabens in the dissolved phase were over 96%, with high efficiencies in MeP, EtP, and n-PrP. Risk assessment indicated that parabens in the effluent were not likely to pose an environmental risk to aquatic ecosystems. The present study indicates that the treatment processes employed in full-scale WWTPs are effective at removing parabens and highlights the possibility of utilizing WWTPs for restoring water quality in riverine and coastal regions heavily impacted by paraben contamination.

Bisphenol A (BPA) is considered as xenoestrogen, a crucial component utilized for the manufacturing of plastic products. It has a potential to disrupt the endocrine system and induces endocrine-related metabolic disorders. We aimed to investigate the exposure of BPA in Pakistani population and its association with sociodemographic features, dietary habits, and risk factors of diabetes mellitus (DM). This cross-sectional study was conducted on 400 participants among which 61.75% participants were diabetic and 38.25% were non-diabetic. We developed a structured questionnaire, gathered sociodemographic data, and collected their urine and blood samples for the estimation of BPA and various biomarkers as risk factors of DM, respectively. Pearson correlation coefficient was determined for urinary BPA levels and DM risk factors. Urinary BPA values were adjusted for confounders. Sociodemographic data shown that urinary BPA level was significantly higher (p < 0.05) in obese people (BMI > 27) living in semi-urban and industrial areas. BPA was detectable in 75% of study participants. Urinary BPA level was found to be higher in diabetic participants compared with that of non-diabetics. A significant correlation is observed between BPA exposure and DM risk factors. We found that urinary BPA level was correlated with elevated levels of HbA1c (r = 0.6028), HOMA-IR (r = 0.5356), CRP (r = 0.6946), BUN (r = 0.6077), AST (r = 0.5151), FFA (r = 0.5759), TGs (r = 0.5608), and MDA (r = 0.6908). Hence, our study adds to the growing body of evidence supporting the role of BPA exposure as a risk factor for DM and may be associated with higher glycemic index, increased pro-inflammatory and oxidative stress biomarkers, dyslipidemia, and impaired functioning of the liver and kidney. Heating food in plastic containers and consumption of packed food items are the main sources of BPA exposure which are positively associated with DM.

The escalating generation of biosolids and increasing regulations regarding their safe handling and disposal have created a great environmental challenge. Recently, biosolids have been incorporated into the hydrolysis step of a two-step thermal lipid conversion process to act as water replacement in the production of renewable chemicals and fuels. Here, the hexane extract recovered from hydrolysis of biosolids, lipids from brown grease hydrolyzed using either water (control) or biosolids as a water replacement, was pyrolyzed at 410–450 °C for 2 h. The product distribution and composition were not significantly different when biosolids were used to hydrolyze brown grease instead of water. The liquid product consisted mainly of alkanes, alkenes, aromatics, and cyclic compounds similar to those in petroleum-derived liquid fuels. However, the use of biosolids as a water substitute resulted in a significant increase in sulphur content of the pyrolysate, which will necessitate processes to reduce the sulphur content before or after pyrolysis. Nevertheless, the pathways proposed in this paper are considered as potentially economically viable approaches to not only resolve the issues associated with disposal of biosolids but also to produce renewable hydrocarbons for fuel and chemical applications. Graphical abstract

Low-cost bioadsorbent such as shrimp shell chitin was used for the removal of polyphenols and COD from olive mill wastewater (OMW). In order to achieve a high polyphenols and chemical oxygen demand (COD) removal efficiency and to reduce the number of experiments, two levels of fractional 2⁴ factorial design experiments were carried out. The influence of different experimental parameters such as solution pH, adsorbent concentration, contact time, stirring speed, and their interactions during polyphenols and COD removal were investigated. Optimized values of pH, adsorbent concentration, contact time, and stirring speed were found equal to 12, 10 g/L, 24 h, and 420 rpm/min, respectively. The maximum polyphenol uptake under these experimental conditions reached 69.47%. Whereas the maximum removal of COD achieve 43% in 10 g/L, 12, 24 h, and 80 rpm/min for adsorbent concentration, pH, contact time, and stirring speed as optimal conditions, respectively. The experimental equilibrium data were tested using the Freundlich and Langmuir isotherm models. It was found that adsorption of polyphenols on shrimp shell chitin is well fitted both models. Kinetics of the adsorption process was studied by investigating the pseudo-first-order, pseudo-second-order kinetics, and intraparticle diffusion mechanism and showed that the pseudo-second-order kinetic model provided a better correlation for the experimental data studied in comparison to the pseudo-first-order model and intraparticle diffusion. These results revealed that shrimp shell chitin can be used as an effective and low-cost adsorbent to remove polyphenols and COD from OMW.

Macroscopic utilization of nanomaterial provides a new idea for the research and development of novel adsorbent, which can enhance efficiency in the adsorption and elution process. In this paper, nano-polypyrrole (PPy) was dispersed into two inexpensive and renewable biomass materials, gelatin (Gel) and chitosan (CS), to fabricate a novel photo/electric-sensitive hydrogel, Gel/CS/PPy. The micro-network of Gel/CS/PPy shows a high adsorption rate of 94.2% for acid fuchsine (AF). Furthermore, with the addition of polypyrrole, Gel/CS/PPy has the characteristic of photo/electric response, which can improve the elution efficiency of AF from the adsorbent. The results showed that the elution efficiency could be increased by 4 times with photo-assistance, and about 2 times with electro-assistance. Predictably, using the methods described in this article, high-quality adsorbents can be designed for more organic pollutants. Graphical abstract

Concentrations of the major ions (Ca²⁺, Mg²⁺, Na⁺, K⁺, NH₄⁺, Cl⁻, HCO₃⁻, SO₄²⁻ and NO₃⁻), pH and electrical conductivity (EC) values in the rainwater (RW) samples at 16 stations in Syria were determined for characterizing the principal factors affecting the chemical composition of precipitation (P) in this country. Collection of the RW samples was made on a monthly basis during the period (1989–2006). The volume-weighted mean (VWM) values calculated for the different parameters at all stations show VWM values of 6.84 and 96 μS/cm for pH and EC, respectively. The ionic trend of the VWM concentrations (μeq/L) in the RW samples of entire dataset follows the descending order: Ca²⁺ ≥ HCO₃⁻ > SO₄²⁻ > Mg²⁺ > Cl⁻ > Na⁺ > NO₃⁻ > K⁺ > NH₄⁺. The lowest pH and EC values were found for the southern mountainous stations, while the highest were reported for the interior inland stations, depending on the amount of carbonate dust present in the atmosphere. The major part of the RW salinity (> 70%) was due to Ca²⁺, HCO₃⁻ and SO₄²⁻ concentrations. The highest concentrations of Na⁺ and Cl⁻ were found for the Tartous coastal station, where the Na⁺/Cl⁻ ratio (0.84 ± 0.16) was remarkably very close to that of the Mediterranean Sea (MS) value (0.86), implying thus the sea spray effect. The highest NO₃⁻ concentrations (≈ 8–9 mg/L), with relatively high SO₄²⁻/NO₃⁻ ratios (> 2 ± 1), were found for the major cities (Damascus, Homs and Aleppo), implying hence the influence of intensive traffics and urban pollutions. The pH parameter was moderately linked with Ca²⁺ and HCO₃⁻ (R² ≈ 0.36), while EC was correlated with all ions, except NH₄⁺. This later ion was weakly correlated with NO₃⁻ (R² ≈ 0.23). Strong correlations were found between Ca²⁺ and SO₄²⁻ (R² ≈ 0.80) and between Cl⁻ and Na⁺ (R² ≈ 0.95). Ca²⁺ and Mg²⁺ ions were the most responsible for neutralizing the RW acidity. The role of K⁺ and NH₄⁺ as acidity neutralizers was small. By using the principal component analysis (PCA), five major factors, explaining ≈ 87% of the total variance, were suggested for the possible sources affecting the chemical composition of RW in this country. The factors are (1) crustal natural materials, (2) sea salts, (3) fossil fuel combustion, (4) rural activity, and (5) biomass burning.

The general toxicity assays for evaluating the risk of aquatic environment were commonly based on single-species test organism models. Thus, the lack and conflict of the different responses among species had hindered researchers to assess the real toxicity of a target toxicant. Therefore, the difference between the test species and their corresponding methodologies was investigated in this work and three species, Escherichia coli, Saccharomyces cerevisiae and Misgurnus anguillicaudatus (a fish), were chosen as the test organism for typical prokaryotes, eukaryotes, and vertebrates, respectively. More specifically, we investigated (i) the individual and combined toxicity of Cu²⁺ and Zn²⁺ by the three test organisms; (ii) the different evaluation manners for the test organisms, including IC₅₀ and toxic unit (TU) model for microorganisms by respiratory toxicity assay and enzyme-substrate assay, while survival time for fish; and (iii) the states of test organism, including suspended and immobilized states for microorganisms. The combined effects, including synergistic (Vt < Vp), antagonistic (Vt > Vp) and additive effects for the three species, were complex as that they were usually dose-dependent and could be changed by the different evaluation manners. The present work was useful for enriching of the associated theory and the insights from this work could open the way for further practical risk assessments.

Using the quantile GARCH model estimators to gauge the bidirectional risk magnitude and the Granger causality test in risk distributions to detect the existence of risk spillovers, this paper explores the extreme risk spillovers of China’s regional carbon markets to local listed firm’s stock returns. From the perspectives of macro region level and micro firm level, the findings are outlined as follows. First, among the top three active carbon trading pilots (Hubei, Guangdong, and Shenzhen), Hubei pilot exhibits significant “low risk and high profit” features. Second, the predominant risk spillover effects to local listed firms are heterogeneous across pilots. Specifically, Hubei pilot is dominated by “up-to-down” effect, and Guangdong pilot is dominated by “down-to-down” effect, while Shenzhen pilot has no predominant effect. The heterogeneous risk spillover performance may be caused by the regional divergence in economic development, industry structure, and cap setting concerning each pilot. Third, the risk transmission performance from carbon allowance price to local listed firm’s stock returns depends on the firm’s belonging sector. That is, environment-related firms, either environment-friendly firms or pollution-intensive firms, are more susceptible to carbon markets’ risks compared with environment-unrelated firms. This paper supplies novel information on the risk transmission from carbon markets to local economic entities, which proves valuable not only for firms to improve risk aversion ability but also for policy-makers to perfect carbon markets’ mechanism.