The genus Artemia sp. has been accepted as a reliable model organism for aquatic toxicity and nanotoxicity experiments, as far as the ISO TS 20787 has recently been published to standardize nanotoxicity test with this organism. Experimental and environmental conditions may affect the toxicity of nanomaterials on aquatic organisms including Artemia sp. nauplii. In this study, acute toxicity effects of silver nanoparticles (AgNPs) on the nauplii of Artemia salina was investigated under various conditions (e.g. different lights, salinities, temperatures, volume and agitation of exposure media and instar stages of nauplii). The EC values were calculated using Probit program and all data were analyzed statistically by SPSS software. At all test conditions, the immobilization rate of Artemia nauplii increased in a concentration-dependent manner (P < 0.05). The sensitivity of instar stage II to different concentrations of AgNPs was significantly higher than instar I (P < 0.05). The toxicity effect of AgNPs was affected by alteration of environmental conditions, so that the effective concentration (EC) values for instar I of A. salina decreased with increasing water temperature, decreasing water salinity and in continuous darkness condition. The EC50 value of AgNPs was significantly lower in 100 mL beakers (21.35 ± 5.67 mg L−1) than 10 mL well plates (42.44 ± 11.30 mg L−1). Agitation of exposure media did not affect the toxicity of AgNPs. The results indicated that the experimental and environmental conditions influence on the toxicity of AgNPs in the nauplii of A. salina.

In this study, methodological factors influencing the dissolution of metal(loid)s in simulated lung fluid (SLF) was assessed in order to develop a standardised method for the assessment of inhalation bioaccessibility in PM2.5. To achieve this aim, the effects of solid to liquid (S/L) ratio (1:100 to 1:5000), agitation (magnetic agitation, occasional shaking, orbital and end-over-end rotation), composition of SLF (artificial lysosomal fluid: ALF; phagolysosomal simulant fluid: PSF) and extraction time (1–120 h) on metal(loid) bioaccessibility were investigated using PM2.5 from three Australian mining/smelting impacted soils and a certified reference material. The results highlighted that SLF composition significantly (p < 0.001) influenced metal(loid) bioaccessibility and that when a S/L ratio of 1:5000 and end-over-end rotation was used, metal(loid) solubility plateaued after approximately 24 h. Additionally, in order to assess the exposure of metal(loid)s via incidental ingestion of surface dust, PM2.5 was subjected to simulated gastro-intestinal tract (GIT) solutions and the results were compared to extraction using SLF. Although As bioaccessibility in SLF (24 h) was significantly lower than in simulated GIT solutions (p < 0.05), Pb bioaccessibility was equal to or significantly higher than that extracted using simulated GIT solutions (p < 0.05).

More than 40% of the crystalline silicon has been wasted as silicon cutting waste (SCW) during the wafer production process. This waste not only leads to resource wastage but also causes environmental burden. In this paper, SCW produced by the diamond-wire sawing process was recycled by Al-Si alloying process. Cryolite was introduced to the reaction system to dissolve the SiO₂ layer existed on the surface of the Si particles in SCW. Alloys with 12.02 wt% of Si were prepared and the mechanism of the alloying process was investigated in detail. The Si-Al-cryolite system and SiO₂-Al-cryolite system were studied individually to analyze the reaction process and transferring behavior of Si and SiO₂ in SCW. The SiO₂ shell was firstly transformed into Si-O-F ions. Then the Si-O-F ions diffused to the reaction interface by the effect of the concentration gradient and were reduced to Si by the aluminothermic reduction reaction: 4Al (l) + 3SiO₂ (dissolved in the melt) = 3Si (Al)+ 2Al₂O₃ (dissolved in the melt). Then the internal Si particles were released into cryolite after the dissolution of SiO₂ and transferred to the reaction interface by the effect of gravity. The influences of the mass ratio of Al/SCW and agitation modes on the Si content of the alloys and the Si recovery ratio in SCW were investigated. With the increase of the mass ratio of Al/SCW from 2.2 to 6.5, the Si recovery ratio in SCW increased from 44.08% to 69.05%, but the silicon content of the alloys decreased from 16.06 wt% to 8.83 wt%. Agitation can effectively improve the smelting effect during smelting by which the silicon content of the alloys and the Si recovery ratio in SCW increased from 12.02 wt% and 64.25% to 13.17 wt% and 69.46%, respectively.

Benzene, toluene and xylene (BTX) belong to an important group of aromatic volatile organic compounds (VOCs) that are usually emitted from various sources. BTX play a vital role in the tropospheric chemistry as well as pose health hazard to human beings. Thus, an investigation of ambient benzene, toluene and xylene (BTX) was conducted at urban and rural sites of Gorakhpur for a span of one year in order to ascertain the contamination levels. The sampling of BTX was performed by using a low-flow SKC Model 220 sampling pump equipped with activated coconut shell charcoal tubes with a flow rate of 250 ml/min for 20–24 h. The analysis was in accordance with NIOSH method 1501. The efficiency of pump was checked weekly using regulated rotameters with an accuracy of ±1%. The samples were extracted with CS₂ with occasional agitation and analyzed by GC-FID. The total BTX concentration ranged from 3.4 μg m⁻³ to 45.4 μg m⁻³ with mean value 30.95 μg m⁻³ and median 24.8 μg m⁻³. The mean concentration of total BTX was maximum during winter (39.3 μg m⁻³), followed by summer (28.4 μg m⁻³) and monsoon season (25.1 μg m⁻³). The mean concentration of BTX at urban site (11.8 μg m⁻³) was higher than that at rural site (8.8 μg m⁻³). At both the sites, T/B and X/B ratios were highest in monsoon and lowest in winters. Toluene against benzene plot shows R² value of 0.96 and 0.49 at urban and rural sites respectively. Higher R² value at urban site clearly indicates similar sources of emission for benzene and toluene. At both the sites, the estimated integrated lifetime cancer risk (ILTCR) for benzene exceeded the threshold value of 1E-06 whereas the individual hazard quotients (HQ) for BTX did not exceed unity at any of the sites.

A fast (16min) procedure to assess the bioaccessible metallic fraction of Cd, Cr, Cu, Ni, Pb and Zn simultaneously extracted (SEM) from marine sediments plus an indirect approach to determine acid volatile sulfides (AVS) are presented. For the extraction process magnetic agitation was compared with ultrasonic stirring (using a bath and a probe), and several stirring times were assayed. The proposed SEM procedure uses an ultrasonic probe and 1mL of HCl. It dramatically minimizes the turnaround time and the residues. AVS were evaluated as the difference between the amounts of sulphur in the solid residue after the extraction and total sulphur in the original sample. These procedures are fast, easy to implement and cost-effective to assess the potential risk posed by metals in marine sediments. They were tested using several CRMs and applied to sediments from two Galician Rias (NW Spain); their SEM-AVS differences indicated no biological risk.

Desulfurization of liquid fuels mitigates the amount of noxious sulfur oxides and particulates released during fuel combustion. Existing literature on oxidative-adsorptive desulfurization technologies focus on sulfur-in-fuel removal by various materials, but very little information is presented about their desorption kinetics and thermodynamics. Herein, we report for the first time, the mechanism of sulfur desorption from neutral activated alumina saturated with dibenzothiophene sulfone. Batch experiments were conducted to examine the effects of agitation rate, desorption temperature, sulfur content, and eluent type on sulfur desorption efficiencies. Results show enhanced desorption capacities at higher agitation rate, desorption temperature, and initial sulfur content. Desorption efficiency and capacity of acetone were found to be remarkably superior to ethanol, acetone:ethanol (1:1), and acetone:isopropanol (1:1). Desorption kinetics reveal excellent fit of the nonlinear pseudo-second-order equation on desorption data, indicating chemisorption as the rate-determining step. Results of the thermodynamics study show the spontaneous (ΔG° ≤ −2.08 kJ mol⁻¹) and endothermic (ΔH° = 32.35 kJ mol⁻¹) nature of sulfur desorption using acetone as eluent. Maximum regeneration efficiency was attained at 93% after washing the spent adsorbent with acetone followed by oven-drying. Scanning electron microscopy, Fourier transform infrared, and X-ray diffraction spectroscopy analyses reveal the intact and undamaged structure of neutral activated alumina even after adsorbent regeneration. Overall, the present work demonstrates the viability of neutral activated alumina as an efficient and reusable adsorbent for the removal of sulfur compounds from liquid fossil fuels.

Phenol and its derivatives behave as mutagens, teratogens and carcinogens inducing adverse physiological effects and are considered environmental hazards. The present study focuses on high concentration phenol utilization by Aspergillus niger FP7 under various physicochemical parameters. The soil remediation potential of the culture for reducing phenol toxicity against Vigna radiata L. seed germination was also evaluated along with the extent of phenol utilization using high-performance liquid chromatography. Aspergillus niger FP7 showed phenol tolerance up to 1000 mg/l, beyond which there was a sharp reduction in phenol utilization. Supplementation of the mineral salt medium with glucose and peptone and application of a 100 rpm agitation rate enhanced phenol utilization (up to 88.3%). Phenol utilization efficiency decreased (up to 29.6%) when cadmium and mercury salts were present, but the same improved (59.4–75.5%) by the incorporation of cobalt, copper and zinc salts. Vigna radiata L. seeds sown in the non-augmented soil revealed a 3.27% germination index, and with fungal augmentation, the germination index improved (97.3%). The non-augmented soil demonstrated 3.1% phenol utilization, while for the augmented soil, the utilization was 79.3%. Based on the phytotoxicity study and chromatographic analysis, it could be inferred that Aspergillus niger FP7 significantly enhanced phenol utilization in soil. In the future, Aspergillus niger FP7 could be of potential use in bioremediation of sites polluted with high concentrations of phenol.

Biochemical methane potential (BMP) and specific methanogenic activity (SMA) tests are performed to assess sludges’ ability to degrade substrates anaerobically. Traditionally, the Modified Gompertz model is applied to estimate methane production and to describe methanization kinetics. However, technical literature reports other models that can be used for these purposes and may be equally or much suitable. This work aimed to determine the BMP and SMA of four types of anaerobic sludges, conduct a kinetic study of methane production, apply six mathematical models in BMP assays, and evaluate which one best describes the methanization bioprocess. The tests were carried out in batch reactors (50 mL reaction volume) maintained at mesophilic temperature (35 °C) and under agitation (150 rpm). Glucose and a volatile fatty acids solution were used as substrates. As inoculants, sanitary sludge, brewery sludge, and two sludges from the swine wastewater treatment (SWS) were used, one of which was previously adapted to microaerobic conditions. SWS degraded the substrates more quickly and returned the highest BMP, SMA, and methane concentration values in the biogas. Thus, in studies of methane production and energy recovery, the application of SWS can be advantageous. Mathematical models that describe exponential functions, mainly the Fitzhugh model, were the most adequate to describe methane production kinetics from readily biodegradable substrates.

This work proposes a novel approach for the coupling of ozonation and Fenton processes using a new prototype of a high rotation bubble reactor (HRBR), which improves utilization of the ozone and hydrogen peroxide through bubble generation and axial and radial dispersion of the flow. The HRBR integrates the rotor and the diffuser in the same device facilitating the generation and dispersion of the ozone bubbles inside the reaction tank. Thus, the mass transfer to the liquid phase is enhanced. Most of the experiments were carried out under neutral pH and 1580 rpm of agitation during the 20 min of reaction. Total ibuprofen degradation was achieved within 20 min of operation for most of the couplings and individual processes evaluated. It was successfully demonstrated that the HRBR can be used as a reactive system for heterogeneous Fenton and ozonation coupling because it presents a high synergy. For the ozonation process, the reactor also displayed a good performance because the residual ozone in the gas is lower than 0.4 mg/L, which indicates that there is a suitable ozone utilization. Ibuprofen degradation by other processes like oxidation direct by H₂O₂ and heterogeneous Fenton was 28.0% and 73.1%, respectively. It was determined that the reaction rate, synergy, OUI (ozone utilized index), and consumption of electrical energy (EE/O) of the coupled processes could be improved by using the HRBR depending on the experimental conditions.