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.

The sorption behaviors of brilliant blue FCF dye by natural clay and modified with iron chloride were determined. The materials were characterized by X-ray diffraction and scanning electron microscopy, and the zero point charges were also determined. The effects of pH, contact time, dye concentration, and temperature were considered. The results showed that clay does not suffer any important change in its structure after the chemical treatments. The pH influences the sorption of the dye in the unmodified clay, but this effect was not observed in the iron-modified clay. The equilibrium time and the sorption capacity for the unmodified clay were 48 h and 6.16 mg/g, while for the iron-modified clay, 24 h and 14.22 mg/g, respectively. The sorption kinetics results were best adjusted to the pseudo-first-order and pseudo-second-order models. Sorption isotherms were best adjusted to the Langmuir model, indicating that both clays have a homogeneous surface. Thermodynamic parameters (E, ΔS, ΔG and ΔH) were calculated for the natural clay from the data of the sorption kinetics at temperatures between 20 and 50 °C, indicating that the sorption process is exothermic. For the case of the iron-modified clay, it was not possible to calculate these thermodynamic parameters because the sorption capacities were similar in the temperature range selected.

In Asturias (north of Spain), mercury mining has been identified as a potential source of trace elements such as As, Sb, Pb, and Hg. In particular, at Los Rueldos mine site, some of these contaminants are dissolved in acidic mine drainage (AMD). Here we treated this leachate by means of nanofiltration to remove some of its pollutants. In order to improve our understanding of the geochemical factors involved in nanofiltration, we analyzed sediment geochemistry and the origin of acidic waters. In coherence with the observation of similar behaviors of As, Fe, and Al in the nanofiltration tests, a clear geochemical association between As, Sb, S, and Fe both in sediments and in the occurrence of AMD was detected. The FILMTEC™ NF-2540 membrane used in this study proved to be highly suitable for the treatment and concentration of the metallic and semimetallic contaminants in the acidic water, even at low pH and moderate pressures.

Electrokinetic extraction, which is an emerging technology, can be used for in situ removal of contaminants by the application of a direct current (DC) electric field across the contaminated subsurface soil. In this study, a kaolinite spiked with Pb (720 mg kg-1) was used to investigate the removal of Pb through electrokinetic extraction in the presence or absence of a cation selective membrane (CSM). The contaminated kaolinite was subjected to a constant DC voltage (2 V cm-1) for 4 days. A low DC voltage applied in absence of CSM developed a high pH interface within the electrokinetic cell. The mobility of Pb thus decreased due to the remarkable rise in the pH values. The inclusion of a CSM improved the removal efficiency but could not achieve the critical surface pH (<pH 3.5). The removal efficiency increased in the presence of Ca(NO3)2, such that 95 % of the spiked Pb was extracted from kaolinite, with 88 % of the Pb being recovered from the cathode chambers. In contrast, only 24 % of the spiked Pb was removed in the presence of ethylenediaminetetraacetic acid (EDTA). Moreover, Pb was detected in the anode chamber solution and 60 % of the spiked Pb accumulated at the anode. In the presence of both EDTA and Ca(NO3)2, Pb migrated and accumulated at the anode, thus indicating that Ca has a negligible effect in the presence of EDTA. © 2013 Springer Science+Business Media Dordrecht.

Enzymatic precipitation provides a novel cost-effective and eco-friendly method for remediation of heavy metals from different industrial effluents such as tannery, electroplating, dye industries, and many more. This study has paid attention to bacterial alkaline phosphatase (BAP) from Eschericia coli C90 which catalyzes para-nitrophenyl phosphate (pNPP) and produces inorganic phosphate (Pi) that helps in the precipitation of heavy metals as metalphosphates. The kinetic behavior of BAP with pNPP in Tris-HCl was studied for pH regimes 8, 8.5, 9, 9.5, 10, 10.5, and 11 in detail. The results showed that the maximum activity of the enzyme was at pH 8.5 with an incubation period of 300 min at 37 C. Based on the kinetic data, experiments were performed at pH 8.5 and pH 10 to precipitate Cr3+, Cr6+, Cd2+, Ni2+, and Co2+ from single-ion solutions (250 and 1,000 ppm concentrations) as well as industrial effluents, and the amount of metal precipitated as metalphosphate was derived by determining the amount of metal reduced in the supernatant of the reactions employing atomic absorption spectrophotometer. The precipitation of metals from single-ion solutions at pH 8.5 for 300 min incubation period followed the order Cd2+ > Ni2+ > Cr3+ > Cr6+ > Co2+. In the experiments involving effluents from tannery and electroplating industries, precipitation of 35.1 % of Cr6+, 77.80 % of Ni 2+, and 57.42 % of Cd2+ was achieved from initial concentrations of 621, 97, and 122 ppm, respectively. © 2013 Springer Science+Business Media Dordrecht.

Thus far, members of the genus Dehalococcoides are the only microorganisms known to dehalogenate chlorinated ethenes to ethene and thereby detoxify these common groundwater pollutants. Therefore, it is important to characterize the taxonomic and functional diversity of these key microorganisms and their reductive dehalogenase (RDase) genes in contaminated aquifers for assessing the natural attenuation potential. Little is known about the diversity of RDase genes under field conditions or in laboratory systems under selective pressure during dechlorination activities. Here, we evaluate the diversity of Dehalococcoides sp. and three RDase genes in groundwater as well as in water from a constructed wetland and microcosms setup with contaminated groundwater from the same field site in Bitterfeld (Saxony-Anhalt, Germany). The presence and relative abundance of Pinellas and Cornell subgroups of Dehalococcoides was evaluated by a novel direct sequencing method, which revealed that all sequences were identical and affiliated to the Pinellas subgroup. Contrarily, our results showed remarkable differences at the functional gene level between the systems. Of the vinyl chloride reductase genes, vcrA was detected in samples from the groundwater, wetland, and microcosms, whereas bvcA was only found in wetland and microcosm samples. The trichloroethene dehalogenase gene, tceA could not be detected at all, although complete dehalogenation activity of higher chlorinated ethenes was observed. Our study demonstrates that although the Dehalococcoides 16S rRNA gene sequences retrieved from the investigated systems were identical, the RDase gene diversity varied among the systems, according to the spectrum of the chlorinated ethenes present.

Apart from the generation of fly ash, brine (hyper-saline wastewater) is also a waste material generated in South African power stations as a result of water re-use. These waste materials contain major species such as Al, Si, Na, K, Ca, Mg, Cl and SO₄. The co-disposal of fly ash and brine has been practiced by some power stations in South Africa with the aim of utilizing the fly ash to capture the salts in brine. The effect of the chemical interaction of the species contained in both fly ash and brine, when co-disposed, on the mobility of species in the fly ash–brine systems is the focus of this study. The up-flow percolation test was employed to determine the mobility of some major species in the fly ash–brine systems. The results of the analysed eluates from the up-flow percolation tests revealed that some species such as Al, Ca and Na were leached from the fly ash into the brine solution while some species such as Mg, Cl and SO₄ were removed to some extent from the brine solution during the interaction with fly ash. The pH of the up-flow percolation systems was observed to play a significant role on the mobility of major species from the fly ash–brine systems. The study showed that some major species such as Mg, Cl and SO₄ could be removed from brine solution using fly ash when certain amount of brine percolates through the ash.

A new analytical methodology based on ultra high performance liquid chromatography (UHPLC) after microwave assisted extraction, followed by a clean-up and preconcentration step with solid phase extraction (MAE-SPE) has been developed for the simultaneous determination of 11 endocrine-disrupting compounds (EDCs), including alkylphenolic compounds, bisphenol A, and various synthetic and natural steroidal hormones, in sewage sludge samples. The effects of different variables on MAE-SPE were studied and optimised. The recoveries obtained were higher than 77 %, whereas the relative standard deviations were less than 9 %. The detection limits ranged between 0.1 and 0.7 ng g -1. The developed methodology was successfully applied to the assessment of the presence of EDCs to sewage sludge samples that were collected bimonthly during 1 year and a half from two wastewater treatment plants (WWTPs) located in Las Palmas de Gran Canaria (Canary Islands, Spain). All compounds were consistently found in all the samples under study. © 2013 Springer Science+Business Media Dordrecht.

Accumulation of metals in aquatic organisms is influenced by several factors, including the presence of other metals; therefore, there is a need to study the effects of mixtures of other metals on the accumulation of a particular metal on the organisms. In this study, the capacity for nickel (Ni) regulation by the juvenile decapod crustacean Penaeus vannamei was analyzed. The effects of both solely Ni exposure and in the presence of other metals such as zinc (Zn), lead (Pb), and cadmium (Cd) in a mixture were analyzed to determine any possible synergism. A previous study revealed that a metal mixture of Zn, Cd, and Pb without Ni induces a higher metal uptake in P. vannamei for all three metals, but in this study, no effect was observed for Ni. The results showed no change in the regulatory capacitance for Ni, even in the presence of other metals. The observed capacity of P. vannamei to regulate body concentrations of nickel prevents its use as a suitable biomonitor for this metal.