Influence of operational key parameters on the photocatalytic decolorization of Rhodamine B dye using Fe2+/H2O2/Nb2O5/UV system

The present research deals with the development of a new heterogeneous photocatalysis and Fenton hybrid system for the removal of color from textile dyeing wastewater as Rhodamine B (RhB) solutions by using Fe²⁺/H₂O₂/Nb₂O₅ as a photocatalytic system. The application of this photocatalytic system for the decolorization of dye contaminants is not reported in the literature yet. Different parameters like dye concentration, Nb₂O₅/Fe²⁺ catalyst amount, pH, and H₂O₂ concentration have been studied. The optimum conditions for the decolorization of the dye were initial concentration of 10 mg L^?1 of dye, pH 4, and Nb₂O₅/Fe²⁺ catalyst concentration of 0.5 g L^?1/50 mg L^?1. The optimum value of H₂O₂ concentration for the conditions used in this study was 700 mg L^?1. Moreover, the efficiency of the Nb₂O₅/photo-Fenton hybrid process in comparison to photo-Fenton alone and a dark Fenton process as a control experiment to decolorize the RhB solution has been investigated. The combination of photo-Fenton and Nb₂O₅ catalysts has been proved to be the most effective for the treatment of such type of wastewaters. The results revealed that the RhB dye was decolorized in a higher percent (78 %) by the Nb₂O₅/photo-Fenton hybrid process (Fe²⁺/H₂O₂/Nb₂O₅/UV) than by the photo-Fenton process alone (37 %) and dark Fenton process (14 %) after 120 min of treatment. Moreover, the Nb₂O₅ catalyst as a heterogeneous part of the photocatalytic system was demonstrated to have good stability and reusability.     

Preconcentration of tin in environmental and biological samples by ion exchange using modified Amberlite XAD-2

Utilization of Amberlite XAD-2 surface modified by covalent immobilization of brilliant green through an azo spacer for adsorptive enrichment of Sn(II) from environmental and biological samples was highlighted. The resulting resin was characterized by Fourier transform infrared spectroscopy, elemental analysis, thermogravimetric analysis, and scanning electron microscopy. The resin retained Sn(II) ions at an optimum pH of 9.5 with a sorption capacity of 40 mg g^?1. The modified sorbent could be reused for 10 cycles without significant changes in sorption capacity. The recovery of Sn(II) was 98% when eluted with 0.1 mol L^?1 ethylenediaminetetraacetic acid. Scatchard analysis revealed that binding sites in the modified resin were homogeneous. The equilibrium adsorption data were analyzed using the Langmuir, Freundlich, Temkin, and Redlich–Peterson isotherm models. The method was applied with satisfactory results for determination of Sn(II) ions in human plasma and sea water.     

A new multimodal and asymmetric bivariate circular distribution

Multimodal and asymmetric bivariate circular data arise in several different disciplines and fitting appropriate distribution plays an important role in the analysis of such data. In this paper, we propose a new bivariate circular distribution which can be used to model both asymmetric and multimodal bivariate circular data simultaneously. In fact the proposed density covers unimodality as well as multimodality, symmetry as well as asymmetry of circular bivariate data. A number of properties of the proposed density are presented. A Bayesian approach with MCMC scheme is employed for statistical inference. Three real datasets and a simulation study are provided to illustrate the performance of the proposed model in comparison with alternative models such as finite mixture Cosine model.     

DNA damage in workers exposed to formaldehyde at concentrations below occupational exposure limits

Formaldehyde has been classified in group 1 as a potential source of human carcinogen by the International Agency for Research on Cancer. In this study, we evaluated the DNA damage in workers who were occupationally exposed to formaldehyde during the manufacture of melamine dinnerware.

Age, sex, smoking habits, and socioeconomic status were matched by the controls (n = 34) of workers not occupationally exposed to formaldehyde. The median value of formaldehyde time weighted average exposure in three workshops was 0.086 mg/m³. No significant difference was observed between sex and smoking habit in the assessed workers. Alkaline comet assay of peripheral blood lymphocytes was used to determine the DNA damage in the subjects. Olive moment was significantly higher in the exposed group compared with the control group.

Overall, the results suggest that respiratory exposure to low concentrations of formaldehyde causes DNA damage in peripheral blood lymphocyte. Therefore, exposure to formaldehyde should be reduced to the lowest possible level.     

The potential of biomonitoring of air quality using leaf characteristics of white willow (Salix alba L.)

In this study, we assess the potential of white willow (Salix alba L.) as bioindicator for monitoring of air quality. Therefore, shoot biomass, specific leaf area, stomatal density, stomatal pore surface, and stomatal resistance were assessed from leaves of stem cuttings. The stem cuttings were introduced in two regions in Belgium with a relatively high and a relatively low level of air pollution, i.e., Antwerp city and Zoersel, respectively. In each of these regions, nine sampling points were selected. At each sampling point, three stem cuttings of white willow were planted in potting soil. Shoot biomass and specific leaf area were not significantly different between Antwerp city and Zoersel. Microclimatic differences between the sampling points may have been more important to plant growth than differences in air quality. However, stomatal pore surface and stomatal resistance of white willow were significantly different between Zoersel and Antwerp city. Stomatal pore surface was 20% lower in Antwerp city due to a significant reduction in both stomatal length (?11%) and stomatal width (?14%). Stomatal resistance at the adaxial leaf surface was 17% higher in Antwerp city because of the reduction in stomatal pore surface. Based on these results, we conclude that stomatal characteristics of white willow are potentially useful indicators for air quality.     

Water pinch analysis for water and wastewater minimization in Tehran oil refinery considering three contaminants

This study aims to find an appropriate way to minimize water utility in the petrochemical and petroleum industries due to high rate of water consumption. For this purpose, Tehran oil refinery has been well studied. In this research, three key contaminants including suspended solid, hardness as well as COD have been considered to analyze the water network. In addition, the potential of water reuse was studied for all methods. These key contaminants once were analyzed separately as a single contaminant and the amount of required freshwater was calculated for them. In this stage, amount of freshwater was reduced to about 60.9 (17%), 203 (59.7%) and 143 m³/h (42.5%) in terms of suspended solids, hardness, and COD, respectively. Water minimization within operations for suspended solids is less than two others. Therefore, this is a limiting contaminant and can be selected as a key contaminant. In the next stage, three contaminants were analyzed two by two based on their mass transfer. Results show that, in the targeting for minimization based on the suspended solids and hardness, the amount of required water is reduced to 142.74 m³/h or 42%. This amount for suspended solids and COD is equal to 86.3 m³/h (26%) and for COD and hardness is 124 m³/h (37%). Analyzing the methods shows that the method based on the double contaminant gives more precise results rather than single contaminant.     

Investigation on diazinon and oxydemeton-methyl residues in cucumbers grown in Kerman greenhouses

Pesticides are considered as the most polluting substances. The residue of pesticides in agricultural crops, especially in greenhouse harvests, has been reported critical. Cucumber, considered as a vegetable, is an agricultural product which is commonly found in the Iranian food basket. The current study aims to assess the level of diazinon and oxydemeton-methyl existing in cucumbers sampled from Kerman greenhouses. The pesticide residue was extracted by acetone and dichloromethane. The extracts were cleaned up according to the solid-phase extraction method. The pesticide residues were then determined by capillary gas chromatography with nitrogen-phosphorus detection. The recoveries were 83 and 85 %, the limit of detection was 0.028 and 0.034 mg/kg, and the limits of qualification were 0.093 and 0.113 mg/kg for diazinon and oxydemeton-methyl in cucumber samples, respectively. The median of diazinon residue was detected 0.582 mg/kg, which was 11.64 times the national maximum residue limit (MRL) (0.05 mg/kg), and the median for oxydemeton-methyl was 1.910 mg/kg, being 1.91 times the MRL (1 mg/kg).     

Evaluating the short-term cost of low-level local air pollution: a life satisfaction approach

Environmental Economics and Policy Studies - To estimate the impact of air pollution on well-being, we combine a set of repeated cross-sectional surveys of individuals with high-resolution...     

Lemon Balm (Melissa officinalis) Stalk: Chemical Composition and Fiber Morphology

This work investigates the potentials of lemon balm (Melissa officinalis L.) stalk (LBS), a massive waste part of medicinal plant, for pulp and papermaking by assessing its fiber characteristics and chemical composition. In addition, LBS properties were compared with some important agro-residues such as bagasse stalk (BS), cotton stalk (CS) and tobacco stalk (TS). There is no information about suitability of the LBS in the open literature. Chemically, LBS fibers contain a relatively high percentage of alpha-cellulose (32.7%), but a low percentage of lignin (25%), which benefits pulping and bleaching. The hemicelluloses in LBS are mainly glucose and xylose. Ash content was about 6%, superior to the average value corresponding to woods, which makes pulping difficult. It was verified that the chemical compositions of the studied agro-residues vary significantly. Morphologically, the LBS fibers are comparable to those of hardwoods. Rather a significant amount of parenchyma cells was found in LBS. The TS has the highest average fiber length, while the LBS has the least, and the lengths of BS and CS fibers fall in between. In general, based on the results of this study, some propositions can be made about the possible applications of LBS as a non-wood renewable source of natural products for use in the production of pulp and paper.