Cr(VI) adsorption from aqueous solutions on peanut husk modified with formaldehyde (PeH-F) and peanut husk modified with formaldehyde and Fe (PeH-FFe) was evaluated as a function of shaking time, initial pH, chromium concentration, and temperature. Results showed that the Cr(VI) is preferentially adsorbed by PeH-FFe at pH 2 than pH 6. It also was found that the chromate equilibrium sorption capacity for PeH-FFe is at least six times higher than for PeH-F. The optimum pH to remove chromium is 2 for both materials; however, PeH-FFe has a higher efficiency for the chromium removal. Finally, Cr(VI) adsorption also depends on chromium concentration and temperature. The adsorption data as a function of concentration obey Linear, Freundlich, and Langmuir isotherms at pH 2 and 6. The Cr(VI) maximum capacity of PeH-FFe at pH 2 was 33.11 mg Cr(VI)/g, slightly higher than that at pH 6 (31.75 mg Cr(VI)/g). The linear isotherm shows that the pH affect the Cr(VI) distribution into the aqueous/solid phases. The negative value of ΔH and positive values of ΔG indicate that the chromium adsorption process is an exothermic and non-spontaneous process. The characterization of the peanut husk modified with formaldehyde and peanut husk modified with formaldehyde and Fe by scanning electron microscopy, Raman, and IR spectroscopies as well as the textural characteristics of the no-living biomasses were also considered in this work. © 2013 Springer Science+Business Media Dordrecht.

The occurrence of 16 pharmaceutical compounds in river sediments from Donana National Park was investigated, as well as the ecotoxicological risk to the ecosystems of this well-known protected zone. Eight of the 16 pharmaceuticals were present in sediments. The highest concentrations in river sediments concern to diclofenac, salicylic acid and caffeine (52.1, 27.2 and 25.4 mu g/kg dm). Naproxen, carbamazepine, propranolol, 17 beta-estradiol and estriol were the other pharmaceutical compounds detected in sediment samples. The relation between the concentration of these pharmaceutical compounds in sediments and river water in contact with was also investigated. While some compounds were detected exclusively in sediment samples (diclofenac, 17 beta-estradiol and estriol), others were detected only in surface waters in contact with (ibuprofen, ketoprofen and gemfibrozil). The outcome analyses of the ecotoxicological risk assessment showed that the presence of all studied pharmaceutical compounds involved a high toxicological risk at short and long term to Donana ecosystem.

A novel immobilized visible light-active photocatalyst (TiO₂/polyvinyl alcohol after thermal treatment (T-PVA)/cordierite honeycomb (CHC)) was successfully prepared by a simple and convenient method combining sol–gel and thermal treatment using tetrabutyl titanate (TBOT) as the titanium source, polyvinyl alcohol (PVA) as the precursor of conjugated polymer, and CHC as the support. The synthesized photocatalyst was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy, and field emission scanning electron microscopy. The results showed that PVA was dehydrated to produce conjugated unsaturated T-PVA. The T-PVA not only extended the response spectrum of TiO₂ to visible light region, but also strengthened the adhesion of TiO₂ to CHC. The TiO₂/T-PVA/CHC showed both outstanding adsorption properties and excellent photocatalytic performance under visible light on the decolorization of Rhodamine B. Over eight cycles, the photocatalyst continued to maintain perfect photocatalytic activity, showing good stability.

The present study deals with the effect of trace metals on the endangered limpet Cymbula nigra. The Bay of Algeciras (Strait of Gibraltar) was used as the study site. Important industrial activity takes place in the area, including frequent oil spills. However, it is home to important populations of C. nigra. The objective of this work was to determine if these animals were being affected at a subcellular level by the pollutants present in their environment and to analyze the trace metal concentrations in the animal’s soft tissues. To determine the effects of water quality on the antioxidant activity and concentrations through field experimentation, a total of six sites were selected in Algeciras Bay, three located in the inner areas (environmentally degraded sites with higher levels of pollutants) and three in the outermost areas of the Bay. Stress associated to reactive oxygen species formation was assessed on digestive glands and gills as the enzymatic antioxidant activity of catalase (CAT), superoxide dismutase (SOD), and glutathione S-transferase (GST) and as the concentrations of lipid-soluble (α-tocopherol and β-carotene) and the water-soluble antioxidants (reduced and oxidized glutathione (GSH and GSSG)). Gills and digestive glands of those animals located in the inner areas of Algeciras Bay showed higher CAT activity values than those located in the outer areas. As a general pattern, we observed higher antioxidant activities and concentrations in digestive glands that in gills, suggesting the possibility that pollutants are mainly being incorporated by limpets through the food. As a general rule, larger animals showed greater concentrations of these compounds. Iron, zinc, and manganese, in this order, were present in the tissues at the highest concentrations. Chromium and manganese were found in significantly higher concentrations in those animals collected from the inner areas of the Bay. Through the present study, we provide the first data regarding the antioxidant defense levels and metal accumulation capacity of this species, and we reinforce the idea that this endangered species may be, in fact, relatively tolerant to degraded environments.

The fate and transport of emerging contaminants have been major concerns for ecoenvironment and human health. This study presents the adsorption behavior of an endocrine disrupting chemical estrone (E1) and its sulfate conjugate estrone-3-sulfate (E1-3S) that are released to the environment via animal waste in significant amounts and direct exposures in grazed pasture systems. Both compounds have been shown to potentially contribute to endocrine disruption in wildlife, and knowledge about the adsorption behavior of these compounds is necessary for a sound environmental risk assessment. For labile compounds such as E1 and E1-3S, however, the standard protocols might overestimate adsorption by not considering metabolite formation or allowing for equilibration that exceeds the commonly reported half-lives of these compounds. Modified batch adsorption experiments with mediator solution of 0.005 M calcium chloride (CaCl₂) and artificial urine (AU) solution were, therefore, conducted to determine the influence of these mediator solutions on the adsorption of E1 and E1-3S in three agricultural soils from Nasarawa State of Nigeria. Adsorption isotherms of both compounds were nonlinear, and the Freundlich equation was found adequate to describe the isotherms. The calculation of concentration-dependent effective distribution coefficients (K d ᵉᶠᶠ) revealed that for a range of realistic exposure concentrations in a grazed farming system, the common approach of using CaCl₂ would deliver incorrect information for a sound risk assessment.

Petroleum hydrocarbon contamination of soil is an emerging environmental threat on the Earth due to possible toxic impact on different ecological receptors. The present study was mainly carried out to evaluate the phytotoxicity of long-term total petroleum hydrocarbon-contaminated soils by the toxicity end points obtained from three plant species Zea mays, Lactuca sativa L., and Cucumis sativus. The tested soil exerted phytotoxicity for all the evaluated end points of plants with dose-dependent relationship. The determined IC₅₀ indicates inhibition in root elongation as the most sensitive toxicity end point for L. sativa L., while inhibition in cross-section area of meristematic zone as the most susceptible and inhibition in seed germination as the least susceptible end points for both Z. mays and C. sativus. The tested root morphometric parameters confirm their applicability as novel toxicity end points. In addition, microcalorimetric analysis confirmed the applicability of inhibition in metabolic heat emission rate as a toxicity end point. Microcalorimetry can be applied to determine the exerted phytotoxic effect on seedlings. The present combined approach concludes that the phytotoxicity of the tested soil is species-specific and varies as follows: Z. mays < C. sativus < L. sativa L. The findings of this study may have implications in planning comprehensive phytotoxicity assessment for hydrocarbon-contaminated soils or screening plant species for phytoremediation program.

The aim of this work was to investigate the susceptibility of the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) to biodegradation in a range of soils and to identify RDX-degrading organisms using stable isotope probing (SIP). RDX degradation was examined in ten soils, primarily from agricultural areas. RDX biodegradation was observed in six samples and only when the microcosms were not aerated. For one soil, 15N-and 13C-based DNA SIP was used to identify the microorganisms responsible for RDX degradation. Two RDX concentrations were examined (10 and 20 mg/L), however, only the higher concentration resulted in a significant SIP signal. In these ultracentrifugation fractions, one terminal restriction fragment length polymorphism (TRFLP) fragment (260 bp) showed a reliable trend of label uptake. This fragment was of higher relative abundance in the heavier fractions from labeled samples compared with the heavier fractions from the unlabeled control samples, indicating that the organism producing this fragment was responsible for label uptake (hence RDX degradation). Partial 16S rRNA gene sequencing indicated the organisms represented by fragment 260 bp belonged to either Sphingobacteria (phylum Bacteroidetes) or the phylum Acidobacteria. To date, these organisms have not previously been directly linked to RDX degradation. The 16S rRNA sequences were compared with the NCBI database and, in all cases, were most similar to uncultured bacteria. The results suggest SIP is a viable method for discovering novel, previously uncultured, RDX degraders. © Springer Science+Business Media Dordrecht 2013.

The growth of white-rot fungus Pleurotus eryngii F032 in a suitable medium can degrade an azo dye Reactive Black 5 (RB5), because of its ability to produce ligninolytic enzymes such as lignin peroxidase (LiP), manganese peroxidase (MnP), and laccase that able to degrade and transform the complex structure of the dye into a less toxic compound. The effect of environmental factors such as initial concentration of Reactive Black 5, pH, temperature of growth medium, surfactant (Tween 80), and agitation were also investigated. The productions of ligninolytic enzymes were enhanced by increasing the white-rot fungi growth in optimum conditions. The decolorization of Reactive Black 5 were analyzed by using UV–vis spectrophotometer at the maximum absorbance of 596 nm. The white-rot fungus, P. eryngii F032 culture exhibited 93.56 % decolorization of 10 mg/L RB5 within 72 h of incubation in dark condition with agitation. The optimum pH and temperature for the decolorizing activity was recorded at pH 3 and 40 °C, respectively. The addition of surfactant (Tween 80) increased the decolorization to 93.57 % and agitation of growth medium at 120 rpm enhanced the distribution of nutrients to the fungus thus optimized the enzymatic reaction that resulted maximum decolorization of RB5 which was 93.57 %. The molecular docking studies were performed using Chimera visualization software as to analyze the decolorization mechanism of RB5 at molecular level.

The effectiveness of activated carbon sample (Carbonₑₓₚ) prepared by KOH chemical activation in hampering oligomerization of multicomponent adsorption was systematically examined. Anoxic (absence of molecular oxygen) and oxic (presence of molecular oxygen) adsorption isotherms of single-solute (2,4-dimethylphenol), binary solute (2-methylphenol/2,4-dimethylphenol), and ternary solute (phenol/2-methylphenol/2,4-dimethylphenol) were studied, using Carbonₑₓₚ and commercial granular activated carbon F400. Both binary solute adsorption and ternary solute adsorption on Carbonₑₓₚ indicated no impact of the presence of molecular oxygen on the adsorptive capacity. No significant differences between oxic and anoxic environment were noticed for any multicomponent adsorption systems, which indicated the effectiveness of Carbonₑₓₚ in hampering the oligomerization of phenolic compounds. On the other hand, in F400, which has lower microporosity and acidic functional groups, significant increases in the adsorptive capacity had been observed when molecular oxygen was present.

The adsorption mechanism of Ni(II) and Zn(II) onto activated carbon fiber (ACF) cloth and felt plain and oxidized was investigated in this work. The adsorption equilibrium data were obtained in a batch adsorber. The concentration of acidic and basic sites on the ACFS was determined by an acid-base titration method. The experimental adsorption equilibrium data were interpreted with the Redlich-Peterson isotherm, which fitted the data reasonably well. The ACF was oxidized with HNO3 solution and the concentration of acidic sites increased during oxidation, whereas that of the basic sites diminished. The adsorption capacity of the oxidized ACF was higher than that of the plain ACF because the oxidation of ACF formed more acidic sites on the surface where the metal cations can be adsorbed. The adsorption capacity of the plain and oxidized ACFs was linearly dependent upon the concentration of carboxylic sites. The adsorption of Ni(II) and Zn(II) on the ACFs was due to both electrostatic interactions and cation-π interactions. The contribution of ion exchange to the overall adsorption of Zn(II) and Ni(II) on ACFs was less than 3.3 % and can be considered negligible. © 2013 Springer Science+Business Media Dordrecht.