In this work, we developed a method based on ultrasound-assisted emulsification microextraction (USAEME) for the determination of nickel by flame atomic absorption spectrometry (FAAS). The method is based on the use of the organic solvent trichloroethylene and 2,2′-thiazolylazo-p-cresol (TAC) as a chelating reagent in a solution containing nickel ions. After ultrasonic emulsification, the mixture is centrifuged to separate the phases. Subsequently, the supernatant is discarded, and the enriched phase is diluted with nitric acid. The nickel content in this new mixture is quantified by FAAS. The following variables were optimized: type of solvent (trichloroethylene), type of chelating reagent (TAC), volume of extraction solvent (100 mL), concentration of chelating reagent (0.015 % w/v), pH (8.0), time of sonication (5.0 min), and time of centrifugation (4.0 min). The limits of detection and quantification were calculated under optimum conditions (0.23 and 0.77 μg L⁻¹, respectively). The enrichment factor obtained was 190. The relative standard deviation (RSD%) of the method (10.0 μg L⁻¹) was 2.3–4.1 %. The proposed method is simple, economical, fast, and efficient for the determination of nickel by FAAS. The procedure was applied to the determination of nickel in certified reference material (BCR-713, wastewater) and water samples.

In this work, metal sorption onto grape stalks waste structural compounds and extractives has been studied for determining their role in Cr(VI), Cu(II) and Ni(II) metal sorption. For this purpose, a sequential extraction of extractives and other compounds from the lignocellulosic material has been carried out. The resulting solid samples obtained in the different extraction processes were used as sorbents of Cr(VI), Cu(II) and Ni(II). Sorption results were discussed taking into account the elemental composition and polarity of the solid extracts. Results indicated that tannins and polyphenols are involved in chromium reduction and sorption. Lignin and celluloses are involved in chromium, Cu(II) and Ni(II) sorption. FTIR analysis confirmed the involvement of lignin moieties in the studied metal ions sorption by grape stalks waste. This study presents a new approach on metal sorption field as the knowledge of the role of the sorbent chemical compounds is essential to determine the key sorbent compounds in the sorption process.

A serial enrichment culture has been grown in an alkaline Fe(III)-citrate-containing medium from an initial inoculum from a soil layer beneath a chromium ore processing residue (COPR) disposal site where Cr(III) is accumulating from Cr(VI) containing leachate. This culture is dominated by two bacterial genera in the order Clostridiales, Tissierella, and an unnamed Clostridium XI subgroup. This paper investigates the growth characteristics of the culture when Cr(VI) is added to the growth medium and when aquifer sand is substituted for Fe(III)-citrate. The aim is to determine how the availability and chemical form of Fe(III) affects the growth of the bacterial consortium, to determine the impact of Cr(VI) on growth, and thus attempt to understand the factors that are controlling Cr(III) accumulation beneath the COPR site. The culture can grow fermentatively at pH 9.2, but growth is stronger when it is associated with Fe(III) reduction. It can withstand Cr(VI) in the medium, but growth only occurs once Cr(VI) is removed from solution. Cr(VI) reduced the abundance of Tissierella sp. in the culture, whereas the Clostridium XI sp. was Cr(VI) tolerant. In contrast, growth with solid phase Fe(III)-oxyhydroxides (present as coatings on aquifer sand) favoured the Tissierella C sp., possibly because it produces riboflavin as an extracellular electron shuttling compound allowing more efficient electron transfer to solid Fe(III) phases. Thus, it is suggested that bacterially mediated Cr(III) reduction in the soil beneath the COPR site is dependent on Fe(III) reduction to sustain the bacterial community.

In this study, the samples of the spatial soil and organs of the grapevine (Vitis vinifera) cultivar Tamjanika were collected from the selected zones near the Mining and Smelting Complex Bor (East Serbia). They were analyzed by ICP-OES to determine the content of Cu, Zn, Pb, As, Cd, and Ni with the aim of ascertaining if these data may help in the assessment and improvement of the quality of environment in polluted areas such as Bor and its surrounding area. The results obtained from the calculated biological and enrichment factors, as well as from the Pearson correlation study and hierarchical cluster analysis confirmed that very useful information is recorded in plant organs: root, stem, leaves, and fruit. Yet, when the atmospheric pollution is the sphere of interest, the most informative data are found in unwashed leaves. The results of this study indicated also that the investigated plant species has some highly effective strategies involved in tolerance to the stress induced by heavy metals, which makes it an excellent candidate for phytostabilization purposes. Planting of this grapevine cultivar can be recommended in all areas that are severely polluted with heavy metals.

SrCO₃ was formed and added as a carrier into copper-based catalyst (CuZnAl catalyst) prepared by hydrothermal method before the catalyst incorporates with HZSM-5. The CuZnAlSr catalyst was characterized by SEM, BET, XRD, IR, and activity-evaluation system in a fixed-bed tubular reactor equipped with chromatograph (GC). The conversion of CO₂ reaches 30.30 %, and the overall yield of methanol and dimethyl ether is 27.80 %. Catalytic property as to CO₂ conversion has only slight decrease even up to 150 h of reaction time. The addition of SrCO₃ enhanced the activity of the catalyst through providing a tridimensional frame and electron transfer bridge.

The intensive pig production has been causing huge amounts of pig slurry with high content of potential pollutants. However, there is a lack of information on the efficiency of combined techniques applied to pig slurry purification. The objective of this research was to assess the pollutant removal efficiency and pathogenic microorganism decrease using mechanical treatments, phytoextraction, and microalgae bioremediation. The purification system was located in the southeast of Spain. Physico-chemical and microbiological parameters were studied in each module of treatment. We observed significant declines for total suspended solids (89 %), settleable solids (100 %), chemical oxygen demand (91 %), biochemical oxygen demand (90 %), total phosphorus (97 %), copper (96 %), zinc (92 %), total nitrogen (89 %), total coliforms (78 %), fecal coliforms (70 %), fecal streptococcus (75 %), Salmonella, Shigella, and Escherichia coli (100 %) in the final effluent of the combined purification system. This survey pointed out the effectiveness of phytoextraction and bioremediation treatments. The results indicated the high efficiency of the purification system, minimizing environmental and human risks.

Glyphosate applied in association with atrazine provides the best cost/benefit for weed control for genetically modified corn. Therefore, the aim of this work was to evaluate the effects of applying glyphosate in mixture with atrazine on soil microbial population and on herbicides fate in a representative Oxisol from Brazil. The treatments consisted in applying the recommended field rate of glyphosate in association with 0, 1, and 2 times the recommended field rate of atrazine (and vice versa), plus the control (without herbicides application). The presence of atrazine temporarily (21 days) decreased soil microbial biomass (SMB) and increased soil carbon mineralization (SCₘᵢₙ, up to 13 times) and microbial metabolic quotient (qCO₂) due to the stresses caused by its toxicity. When the mixture was applied independent of the rates, SMB was recovered and the amounts of extractable and non-extractable¹⁴C-residues were the same for both herbicides at 63 days. These results suggest that glyphosate may mitigate atrazine’s temporary impact on soil microbes by supplying them nutrients during their adaptation.

Chelating reagents impregnated or incorporated into solid sorbents have been widely used in the preconcentration of metal species. In this work, polystyrene-divinylbenzene functionalized with 2-hydroxyacetophenone was used for the preconcentration and determination of cadmium, cobalt, and nickel in sediment samples by flame atomic absorption spectrometry. The sorbent was characterized by infrared spectroscopy and scanning electron microscopy. The influence of variables on the extraction of the metal ions was studied. Under optimized conditions, the method showed enrichment factors of 20 (Cd), 37 (Co), and 32 (Ni) and detection limits of 0.1 (Cd), 0.8 (Co), and 0.6 μg L⁻¹(Ni). The accuracy of the method was tested by analysis of a certified reference material composed of inorganics in marine sediment (NIST 2702). The method was applied to the determination of cadmium, cobalt, and nickel in real sediment samples. Cadmium and cobalt were not found in the sediment samples. Nickel was found in two samples (5.2 and 8.2 μg g⁻¹).

The sorption behavior of cobalt by a sodium-modified zeolite-rich tuff was investigated using cobalt solutions prepared with water from the cooling system of a nuclear reactor. The sorption kinetics shows that the equilibrium was reached in less than 20 h. The isotherms showed that the sorption capacity of the sodium-modified zeolite-rich tuff for cobalt was 20.73 mg/g at 60 °C. The pH affects the sorption capacity of the sodium-modified zeolite-rich tuff for cobalt. The sorption capacity of the sodium-modified zeolite-rich tuff for cobalt was higher using nuclear purity water than water from other aqueous matrices.

Several laccases from different sources have been used in dye decolourization processes. However, only in a reduced number of studies have efforts been done to identify the metabolites produced by the enzymatic treatment as well as to evaluate the toxicity of degradation products. Taking these gaps into account, the objective of this work was to use a laccase from Ganoderma lucidum in the decolourization of the synthetic dye Congo red (C.I. No. 22120, Direct Red 28), largely used in the textile industry. After 6 h of treatment at pH 4.0 and 40 °C, the enzyme was able to decolourize 80 % of Congo red. Fourier transform infrared spectroscopy (FTIR), photoacoustic spectroscopy (PAS) and mass spectrometry allow concluding that laccase effectively changed the structure of Congo red, reducing the colour by modifying the chromophore groups and other parts of the molecule. Several degradation products with m/z ⁺ ranging from 298 to 745 were identified. It is proposed that the first degradation step could be an asymmetric cleavage of the azo bond present in the Congo red structure forming the intermediate with m/z ⁺ 298. The results also suggest a reduction in the toxicity of Congo red after laccase treatment, as indicated by the lettuce seed germination model. In conclusion, G. lucidum laccase could be used in a novel azo dye bioremediation strategy.