In this work, hexavalent chromium adsorption onto LDPE and agave fiber composites coated with chitosan or cellulose was studied in batch experiments. Chemical modifications consisting in cross-linked chitosan, cross-linked chitosan xanthate, and cellulose xanthate were applied to the polysaccharide-coated sorbents in order to increase their stability and adsorption capacity. The sorbents were characterized in terms of morphology by scanning electron microscopy and their chemical composition was evaluated by infrared and nuclear magnetic resonance spectroscopies. The results showed that the adsorption kinetics followed the pseudo-second-order model in all cases (i.e., chemisorption as the rate-limiting step of the adsorption reaction). Moreover, the isotherms evidenced a monolayer adsorption on homogeneous sites described by the Langmuir model. The maximum adsorption capacity of 284.7 mg Cr(VI)/g was obtained for the cross-linked chitosan xanthate sorbent at pH 4 which represents an increase of 43% against the chitosan-coated sorbent (199.1 mg Cr(VI)/g). Besides, functionalized cellulose sorbent also increased its capacity from 84.5 to 106.0 mg Cr(VI)/g cellulose due to the xanthate group. Up to six adsorption-desorption cycles were completed for the case of functionalized chitosan sorbent, confirming that the stability was increased with the cross-linking and the material could be reused several times without losing its adsorption capacity. In the case of cellulose xanthate, only three adsorption cycles were completed. However, improvements were observed in the desorption capacity considering that it decreased below 20% after two cycles in the cellulose-coated sorbent.

Unanticipated increase in the use of silver (Ag) and copper oxide (CuO) nanoparticles (NPs) due to their antimicrobial properties is eliciting environmental health concern because of their coexistence in the aquatic environment. Therefore, we investigated the genetic and systemic toxicity of the individual NPs and their mixture (1:1) using the piscine micronucleus (MN) assay, haematological, histopathological (skin, gills and liver) and hepatic oxidative stress analyses [malondialdehyde (MDA), reduced glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT)] in the African mud catfish, Clarias gariepinus. The fish were exposed to sublethal concentrations (6.25–100.00 mg/L) of each NP and their mixture for 28 days. Both NPs and their mixture induced significant (p < 0.05) increase in MN frequency and other nuclear abnormalities. There was significant decrease in haemoglobin concentration, red and white blood cell counts. Histopathological lesions observed include epidermal skin cells and gill lamellae hyperplasia and necrosis of hepatocytes. The levels of MDA, GSH and activities of SOD and CAT were impacted in C. gariepinus liver following the exposure to the NPs and their mixture. Interaction factor analysis of data indicates antagonistic genotoxicity and oxidative damage of the NPs mixture. These results suggest cytogenotoxic effects of Ag NPs, CuO NPs and their mixture via oxidative stress in Clarias gariepinus.

The application of conventional physicochemical and microbiological techniques for the removal of organic pollutants has limitations for its utilization on wastewaters as landfill leachates because of their high concentration of not easily biodegradable organic compounds. The use of ozone-based technologies is an alternative and complementary treatment for this type of wastewaters. This paper reports the study of the degradation of landfill leachates from different stages of a treatment plant using ozone and ozone + UV. The experimental work included the determination of the temporal evolution of COD, TOC, UV254, and color. Along the experimental runs, the instantaneous off-gas ozone concentration was measured. The reaction kinetics follows a global second order expression with respect to COD and ozone concentrations. A kinetic model which takes into account the gas liquid mass transfer coupled with the chemical reaction was developed, and the corresponding parameters of the reacting system were determined. The mathematical model is able to appropriately simulate COD and ozone concentrations but exhibiting limitations when varying the leachate type. The potential application of ozone was verified, although the estimated efficiencies for COD removal and ozone consumption as well as the effect of UV radiation show variations on their trends. In this sense, it is interesting to note that the relative ozone yield has significant oscillations as the reaction proceeds. Finally, the set of experimental results demonstrates the crucial importance of the selection of process conditions to improve ozone efficiencies. This approach should consider variations in the ozone supply in order to minimize losses as well as the design of exhaustion methods as multiple stage reactors using chemical engineering design tools.

The main purpose of our research was to assess the chronic exposure of red foxes to Cd, Pb and Zn. We have determined concentrations of these metals in the kidney, liver and muscle of 36 red foxes hunted between December 2002 and March 2003 in differently polluted areas in southern Poland. Tissue concentrations of Pb and Cd in the red foxes significantly co-varied with concentrations of these elements in the soil, and differed between the tissues. We compared concentrations of Pb, Cd, and Zn in red foxes with two rodent species, Apodemus flavicollis and Myodes glareolus, trapped simultaneously in the same area. Concentrations of Pb and Cd appeared significantly higher in the red foxes than in the rodents, but the slopes of the relationship between metal concentrations in tissues and in soil were similar in all species. This indicates that extrapolation from results of monitoring studies conducted on rodents to mammalian carnivores is possible but requires applying an extrapolation factor.

The purpose of this study is to experimentally investigate the effect of unsaturation of the biodiesels obtained from grapeseed oil, wheat germ oil and coconut oil (reference fuel) for compression ignition (CI) engine application. Fatty acid profile analysis and physio-chemical properties were determined by standard test procedures. Engine testing was carried out in a 5.2-kW single-cylinder CI engine and the combustion, performance and emission characteristics were analysed. The effect of fuel property variation and the combustion reaction kinetics due to unsaturation difference have been discussed. The maximum brake thermal efficiency at full load for diesel was found to be 32.3% followed by 31.3%, 30.2% and 27.4 %, respectively, for coconut biodiesel (CBD), grapeseed biodiesel (GSBD) and wheat germ biodiesel (WGBD). Maximum heat release rate as observed for diesel, CBD, GSBD and WGBD are 63.2 J/°CA 60.7 J/°CA and 59 J/°CA and 43.4 J/°CA respectively. The brake-specific NO emission at full load is higher for CBD followed by GSBD, WGBD and diesel having values of 9.23 g/kWh, 8.91 g/kWh, 8.21 g/kWh and 7.6 g/kWh respectively. Conversely, the smoke emission is lower for CBD compared to the other tested fuels.

The objective of this study is to identify the feasibility of using rhamnolipid biosurfactant to remediate heavy metals contained in manganese nodules collected from the Clarion-Clipperton Fracture Zone, Pacific Ocean. Deep-sea manganese nodules may represent one of the most important future natural resources for heavy metals due to the depletion of resources on land. Since international marine environment guidelines for deep-sea mining will be set up by international organisations in the 2020s, remediation technologies are urgently required for deep-sea mining tailings. We show that rhamnolipid biosurfactant is an environmentally friendly substance and can be successfully used for the remediation of heavy metals in deep-sea mining tailings under various reaction conditions. Rhamnolipids therefore represent a useful extracting agent for heavy metals in deep-sea mining tailings. The removal of nickel (Ni), copper (Cu), and cadmium (Cd) would be enhanced in the presence of rhamnolipids with specific reaction times and concentrations. Future actual remediation technologies should be developed using rhamnolipid biosurfactant on the basis of these results.

In this work, coal bottom ash, a residue generated in thermoelectric power plant, was employed as an alternative catalyst in photo-Fenton reaction for the degradation of sunset yellow dye from liquid solution under visible irradiation. The residue was characterized by techniques such as XRD, XRF, N₂ adsorption/desorption isotherms, SEM/EDS, and FT-IR. The influence of reaction parameters such as solution pH, catalyst dosage, and H₂O₂ concentration on dye removal was analyzed by a central composite rotatable design 2³. According to the characterization results, the presence of iron in the material was confirmed by analysis of chemical composition by XRF, presenting 5.5 wt% in terms of iron oxide. Through the response surface methodology, it was possible to adjust the polynomial model and determine the optimum region of dye removal. The regression model was predictive and significant, with a coefficient of determination (R²) equivalent to 91%, showing a good fit between the experimental and theoretical values. The optimum region reaching a color removal of 91% has a pH level of 2.7, catalyst dosage of 0.9 g L⁻¹, and H₂O₂ concentration of 10 mmol L⁻¹. Therefore, coal bottom ash, an abundant residue with low cost, showed to be a potential catalyst in a photo-Fenton process for the removal of organic contaminant from liquid solution.

This study aims to investigate the long-run and causal effects of energy consumption, economic growth, urbanization, and trade openness on CO₂ emissions in Turkey using newly developed econometric techniques. To our best knowledge, there has been no study examining the relationship between CO₂ emissions, energy consumption, trade openness, urbanization, and economic growth in Turkey. Therefore, this study proposes to fill this gap in the literature. In this study, we use time series data covering the years between 1960 and 2015. To capture long-run effects, we used ARDL, FMOLS, and DOLS estimators, while wavelet coherence technique is used to explore causal effects among the variables. Our results reveal that (i) there is a long-run equilibrium relationship between CO₂ emissions and energy consumption, economic growth, urbanization, and trade openness; (ii) in the long-run, CO₂ emission in Turkey is significantly triggered by energy consumption, economic growth, and urbanization; and (iii) the results of the wavelet coherence–based causality test provide supportive evidence to the long-run estimations of this study.

Ammonia is one of the most common aquatic pollutants. To analyze the effect of ammonia exposure on the glutathione redox system, we investigated the levels of hydrogen peroxide (H₂O₂) and glutathione, and transcription and activities of glutathione-related enzymes in liver and gills of FFRC strain common carp (Cyprinus carpio L.) exposed to 0, 10, 20, and 30 mg/L of ammonia. The results showed that H₂O₂ content reached a maximum level at 48 h of exposure in the liver of fish. In gills, H₂O₂ increased rapidly at 6 h and reached to maximum levels at 24 h of exposure, indicating that gills experienced oxidative stress earlier than the liver of fish exposed to ammonia. Reduced glutathione (GSH) content and reduced glutathione/oxidized glutathione (GSH/GSSG) ratio increased significantly within 24 h of exposure. Meanwhile, the transcription and activities of glutathione S-transferase (GST) and glutathione reductase (GR) increased significantly in the liver, and glutathione peroxidase (GSH-Px) and GST increased in the gills of fish exposed to ammonia. Malondialdehyde (MDA) content kept at a low level after exposure to low concentration of ammonia, but increased significantly after exposure to 30 mg/L ammonia for 48 h along with a decrease in GSH content and GSH/GSSG ratio. These data showed that the glutathione redox system played an important role in protection against ammonia-induced oxidative stress in the liver and gills of FFRC strain common carp, though the defense capacity was not able to completely prevent oxidative damage occurring after exposure to higher concentration of ammonia. This research systematically studied the response of the glutathione redox system to ammonia stress and would provide novel information for a better understanding of the adaptive mechanisms of fish to environmental stress.

A challenge in side-stream treatment of anaerobic digester supernatant is that the effluent does not meet discharge standards. To address this challenge, this study tested tubular multichannel ceramic microfiltration (MF) and ultrafiltration (UF) membranes for the post-treatment of anaerobic digester supernatant. Pollutant rejection (total suspended solids (TSS), COD, total nitrogen (TN), and total phosphorus (TP)), color removal, and membrane susceptibility to fouling were determined at various transmembrane pressures (TMPs) (0.2, 0.3, 0.4, 0.5 MPa). Both methods completely removed TSS. In MF, COD was removed with 48–76% efficiency at 0.2–0.4 MPa. In UF, COD removal efficiency was slightly higher, reaching 83.7% at 0.4 MPa. With both methods, pollutant removal did not increase at TMP of 0.5 MPa. With both MF and UF, color was reduced by 54–100%, irrespective of the TMP. At 0.2–0.4 MPa, membrane resistance was lower and permeate flux was much higher with MF than UF. At 0.5 MPa, the methods differed only slightly from each other. Due to the larger cut-off, flux decline was slower in MF (0.7 h⁻¹) than in UF (1.1 h⁻¹), as the larger pore-size favors less foulant deposition. Thus, taking into account rejection efficiency, capacity, washing frequency, and cost (pressure), these results indicate that MF at 0.4 MPa is the most effective variant for post-treatment of anaerobic digester supernatant. With this variant, the almost colorless permeate contained 25 mg COD/L, no TSS, 55 mg TN/L (75% in the form of nitrites and nitrates), and 8.5 mg TP/L, thus meeting criteria for water to be used in irrigation or algae cultivation.