Understanding interaction mechanisms between polycyclic aromatic hydrocarbons (PAHs) and soil-washing agents can help in choosing efficient agents which are able to desorb and solubilize PAHs. This study investigated interaction mechanisms between pyrene and four washing agents including: two dissolved organic matters (DOM) F-DOM and CRC-DOM, and two commercial bio-based surfactants BBE-1000 and Supersolv using fluorescence spectroscopy combined with multivariate curve resolution alternating regression (MCR-AR). The efficiencies of these washing agents in removing PAHs from the soil were tested in a soil washing experiment. Pyrene showed π-π interactions with F-DOM and no interaction with CRC-DOM. This could be attributed to the more aromatic structures in F-DOM compared to CRC-DOM. The two DOMs were inefficient in soil washing which might be attributed to the relatively weak effect of π-π interactions in releasing PAHs from the soil. Interaction mechanisms between pyrene and the bio-based surfactants were elucidated with MCR-AR, which resolved three spectroscopically active species from pyrene emission spectra as a function of pyrene and bio-based surfactants concentrations. These species resembled pyrene emission in a polar and nonpolar microenvironment, respectively and of an excimer. Concentration profiles retrieved by the model for the three species showed that, below the critical micelle concentration (CMC), Supersolv created more nonpolar interactions with pyrene compared to BBE-1000. In soil washing, Supersolv showed the highest efficiency in extracting PAHs from the soil. This highlighted the importance of nonpolar interactions in desorbing PAHs from soils, which could then be solubilized in micelles. This study demonstrated the potential of fluorescence spectroscopy combined with the MCR-AR model for selecting efficient soil-washing agents.

The highly unbalanced nature of bio-oil composition poses a serious threat in terms of storage and utilization of bio-oil as a viable fuel in engines. So it becomes inevitable to study the variations in physicochemical properties of the bio-oil during storage to value its chemical instability, for designing stabilization methodologies. The present study aims to investigate the effects of storage stability of bio-oil extracted from pyrolyzing Calophyllum inophyllum (CI) deoiled seed cake on the engine operating characteristics. The bio-oil is produced in a fixed bed reactor at 500 °C under the constant heating rate of 30 °C/min. All the stability analysis methods involve an accelerated aging procedure based on standards established by ASTM (D5304 and E2009) and European standard (EN 14112). Gas chromatography-mass spectrometry was employed to analytically characterize the unaged and aged bio-oil samples. The results clearly depict that stabilizing Calophyllum inophyllum bio-oil with 10% (w/w) methanol improved its stability than that of the unstabilized sample thereby reducing the aging rate of bio-oil to 0.04 and 0.13 cst/h for thermal and oxidative aging respectively. Engine testing of the bio-oil sample revealed that aged bio-oil samples deteriorated engine performance and increased emission levels at the exhaust. The oxidatively aged sample showed the lowest BTE (24.41%), the highest BSEC (20.14 MJ/kWh), CO (1.51%), HC (132 ppm), NOx (1098 ppm) and smoke opacity (34.8%).

Removal of intracellular water in microbial cells remains a key issue for sludge disposal, and here, a novel method of enzymatic treatment with two enzymes, lysozyme and protease, was employed. Total internal reflection fluorescence microscope (TIRF) was applied to image the bacteria in sludge and quantify the evolution of sludge bacteria for the first time. The ratio of dead/live bacterial cells was always higher in the presence of lysozyme than in the presence of protease, indicating that lysozyme has higher activity in inducing bacterial cell degradation and releasing intracellular water. The compositions of extracellular polymeric substances (EPS) were further measured, and the results show that the dewatering performance of sludge is correlated both to the release of cell contents and the variations in EPS composition during cell degradation. Moreover, kinetic analysis demonstrated that the enzyme-catalyzed reaction was substantially completed within 1 h, i.e., the reaction was quite rapid during the first 1 h, and thereafter, it gradually reduced to stability. The mechanism of enzymatic treatment of sludge explored in this study thus not only enhanced the understanding of sludge deep dewatering but also provided significant methodological clues for the disposal of sludge.

Magnetite (Fe₃O₄) nanoparticle-encapsulated mesoporous carbon nanocomposite was fabricated from Fe-based metal–organic framework (MOF) (MIL-102) through carbonization. It was found that Fe-based MOF (MIL-102) is a potential precursor for the fabrication of hexagonal mesoporous carbon nanodisk functionalized with Fe₃O₄ nanoparticles. The obtained nanocomposite was characterized by XRD, FT-IR, N₂ adsorption and desorption, FE-SEM and HRTEM techniques. As a Fenton-like solid catalyst for phenol degradation, Fe₃O₄ nanoparticle-encapsulated mesoporous carbon showed greater catalytic activity for the production of hydroxyl radical from the decomposition of H₂O₂ and it accomplished 100% phenol and 82% total organic carbon (TOC) conversion, within 120 min of reaction. This enhanced catalytic performance was due to confined access for the pollutant to the iron oxide nanoparticles provided by mesopores in carbon shell. Bare Fe₃O₄ nanodisk shows poor catalytic performance in the degradation of phenol, and it obviously reveals the significance of the mesoporous carbon support for iron oxide nanoparticles.

A novel magnetic heavy metal adsorbent was prepared via diethylenetriamine (DETA) modification on magnetic hydrothermal carbon, with glucose and sugar-containing waste water as the carbon source. The prepared materials were characterized by FT-IR, SEM, TEM, EDXRF, TGA, elemental analysis, XPS, and magnetic moment determination. In this paper, the adsorption mechanism of the modified and unmodified adsorbents was well discussed. Four kinds of waste water (watermelon juice, expired sprite, sugar-pressing waste water, and confectionary waste water) were employed to produce heavy metal ion adsorbents; the chemical properties of hydrothermal carbon derived from the proposed sources were analyzed as well. The maximum uptake capacity for Cu²⁺, Pb²⁺, and Cd²⁺ of the adsorbent produced from glucose was 26.88, 103.09, and 25.38 mg g⁻¹, respectively. After 5 cycles, the adsorption ability was still well preserved. This work represents an efficient new direction for the treatment of heavy metal ions in water and the reuse of sugar-containing waste water. Graphical abstract The schemetic of DETA-modified magnetic carbon preparing from sugar-containing wastewater

The aquatic risk assessment of pesticides in tropical areas has often been disputed to rely on toxicity data generated from tests performed with temperate species. Given the differences in ecosystem structure between temperate and tropical ecosystems, test species other than those used in temperate regions have been proposed as surrogates for tropical aquatic effect assessments. Freshwater shrimps, for example are important components of tropical freshwater ecosystems, both in terms of their role in ecosystem functioning and their economic value. In the present study, available toxicity data of (tropical and sub-tropical) freshwater shrimps for insecticides and fungicides were compiled and compared with those available for Daphnia magna and other aquatic invertebrates. Freshwater shrimps appeared to be especially sensitive to GABA-gated chloride channel antagonist and sodium channel modulator insecticides. However, shrimp taxa showed a moderate and low sensitivity to acetylcholinesterase inhibiting insecticides and fungicides respectively. Implications for the use of freshwater shrimps in tropical pesticide effect assessments and research needs are discussed.

Starting with the 2007–2008 cycle, the National Health and Nutrition Examination Survey (NHANES) also oversampled Hispanics other than Mexicans (OHISP) making it possible to treat OHISP as a separate demographic group along with Mexican Americans (MAs), non-Hispanic whites (NHWs), and non-Hispanic blacks (NHBs). Yet, more often than not, OHISP have been merged with MA to form an all-Hispanic demographic group (HISP) thus limiting comparisons between NHW, NHB, and HISP. Consequently, for the first time, this study was undertaken to evaluate differences in the observed levels of selected environmental contaminants between MA and OHISP from five groups of environmental contaminants, namely, polycyclic aromatic hydrocarbons (PAHs), iodine uptake inhibitors (IUIs), environmental phenols (EPHs), priority pesticides (PPs), and perfluoroalkyl acids (PFAAs). Data for 2007–2010 from NHANES were used to conduct this study. OHISP children born in USA had higher levels of selected PAH metabolites than USA-born MA, and Mexican-born MA adolescents had higher levels of selected PAH metabolites than USA-born MA adolescents. USA-born adolescent MA had higher levels of selected parabens than USA-born adolescent OHISP, and OHISP adults born in another Spanish-speaking country had higher levels of selected parabens than USA-born OHISP adults. USA-born MA adults and seniors had higher levels of selected dichlorophenols than Mexico-born MA adults and seniors, respectively. Females had higher levels of selected PAH metabolites, EPHs, and PPs than males among children, adolescents, adults, and seniors, but the reverse was true for the levels of selected IUIs and PFAAs among adolescents and seniors. Smokers had higher levels of almost all PAH metabolites than non-smokers for adolescents, adults, and seniors. The same was true for urinary thiocynate for adolescents, adults, and seniors. OHISP is a multiracial multiethnic demographic group substantially different from MA with possibly different smoking behavior and with possibly differential levels of exposure to certain environmental contaminants and as such should be treated as a demographic group by itself.

A novel chitosan/ceria/iron oxide (CS/ceria/Fe₃O₄) nano-composite adsorbent was synthesized for removal of Cr(VI) and Co(II) ions from aqueous systems in a batch system. The adsorbents were characterized by field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), and Brunauer- Emmett-Teller (BET) analyses. The behavior of swelling kinetics was also studied. The effect of several adsorption parameters including CeO₂ and Fe₃O₄ contents, initial pH, contact time, initial Cr(VI) and Co(II) concentration, and temperature on the adsorption capacity was studied. The double exponential model revealed a better fit with the kinetic data of Cr(VI) and Co(II) ions. The Cr(VI) and Co(II) adsorption process well fitted the Langmuir model. The maximum adsorption capacities estimated from Langmuir isotherm model were 315.4 and 260.6 mg/g for Cr(VI) and Co(II) ions, respectively. Also, thermodynamic parameters were used to distinguish the nature of Cr(VI) and Co(II) adsorption. The reusability of CS/ceria/Fe₃O₄ nano-composite was evaluated with stripping agents of 0.1 M NaOH and 0.1 M HNO₃. Finally, the evaluation of Cr(VI)-Co(II) coexisting system confirmed that the presence of Co(II) ions played an inhibitor role on the Cr(VI) adsorption.

In this work, a new norm descriptor is proposed based on atomic properties. A quantitative structure-activity relationship (QSAR) model for predicting the toxicity of organic compounds to fathead minnow is further developed by norm descriptors. Results indicate that this new model based on the norm descriptors has satisfactory predictive results with the squared correlation coefficient (R²) and squared relation coefficient of the cross validation (Q²) of 0.8174 and 0.7923, respectively. Combining with Y-randomization test, applicability domain test, and comparison with other references, calculation results indicate that the QSAR model performs well both in the stability and the accuracy with wide application domain, which might be further used effectively for the safe and risk assessment of various organics.

In wastewater treatment, oxygen effective diffusion coefficient (D ₑff) is a key parameter in the study of oxygen diffusion-reaction process and mechanism in biofilms. Almost all the reported methods for estimating the D ₑff rely on other biokinetic parameters, such as substrate consumption rate and reaction rate constant. Then, the estimation was complex. In this study, a method independent of other biokinetic parameters was proposed for estimating the dissolved oxygen (DO) D ₑff in biofilms. It was based on the dynamic DO microdistribution in a non-steady-state inactive biofilm, which was measured by the oxygen transfer modeling device (OTMD) combining with an oxygen microelectrode system. A pure DO diffusion model was employed, and the expression of the DO D ₑff was obtained by applying the analytical solution of the model to a selected critical DO concentration. DO D ₑff in the biofilm from the bioreactor was calculated as (1.054 ± 0.041) × 10⁻⁹ m²/s, and it was in the same order of magnitude with the reported results. Therefore, the method proposed in this study was effective and feasible. Without measurement of any other biokinetic parameters, this method was convenient and will benefit the study of oxygen transport-reaction process in biofilms and other biofouling deposits. Graphical abstract ᅟ