Synthesis,Characterization and Application of α, β, and γ Cyclodextrin-Conjugated Graphene Oxide for Removing Cadmium Ions from Aqueous Media

In this study, a novel and facile route for the synthesis of cyclodextrin-conjugated graphene oxide (CDs–GO) nanocomposites by esterification reaction in the presence of EDC/DMAP as catalyst, was developed. The formation of CDs–GO was successfully approved by FT-IR, SEM, TEM, TGA and BET analyses. Then competitive adsorption capacity of cadmium ion by CDs–GO composites and the impact of different empirical parameters like contact time, initial metal ion concentration, and initial pH on the adsorption process were studied. The results showed that β-CD–GO at pH 7 is suitable for removing Cd(II) with 90?% removal efficiency. Also, the adsorption capacity experiment at constant concentration of 50 ppm of Cd(II) showed that more than 50?% of Cd(II) ions could be adsorbed by γ-CD–GO reaching an equilibrium within 2 h. Therefore, the γ-CD–GO and α-CD–GO showed high adsorption capacity toward Cd²⁺ (222.22 mg/g) which were pointedly more than that of β-CD–GO (208.33 mg/g). Furthermore, adsorption kinetics, isotherm studies, and thermodynamic analyses were evaluated. The adsorption data exhibited excellent fit to the pseudo-second-order (R²?>?0.99) and Freundlich isotherm models.

     

Management of landfill leachate in Iran: valorization,characteristics, and environmental approaches

Environmental Chemistry Letters - The quantity and quality of leachate generated in a landfill are very important when it comes to waste management. Sanitary landfill is still being considered as...     

Mid-depth oil concentration due to vertical oil dispersion in a regular wave field

An experimental program is organized to investigate the vertical oil dispersion of surface oil spills in a regular wave field. Various waves characteristics and different volumes of oil spills are tested to assess the oil concentration variations at two sampling stations. It is found that the oil concentration due to vertical oil dispersion follows an ascending diagram to reach a maximum and then decreases while oil slick passes the location. The maximum mid-depth oil concentration (C_max) at the farther sampling station is 30–50 % less than the concentration at the closer sampling station to the spill location. A 50 % increase in oil spill volume causes 30–60 % growth in oil concentrations. The relations between oil concentration and important parameters such as wave characteristics, amount of spilled oil and the distance of sampling stations from the spill location are indicated and also oil concentration variations are quantified. Two equations are derived through statistical analysis of the obtained experimental data, which estimate the magnitude and time of maximum oil concentration.     

Geological sources of fluoride and acceptable intake of fluoride in an endemic fluorosis area, southern Iran

The present study is the first attempt to put forward possible source(s) of fluoride in the Dashtestan area, Bushehr Province, southern Iran. In response to reports on the high incidence of dental fluorosis, 35 surface and groundwater samples were collected and analysed for fluoride. The results indicate that dissolved fluoride in the study area is above the maximum permissible limit recommended by the World Health Organization (WHO). An additional 35 soil and rock samples were also collected and analysed for fluoride, and rock samples were subjected to petrographic investigations and X-ray diffraction. The results of these analyses show that the most likely source for fluoride in the groundwater is from clay minerals (chlorite) and micas (muscovite, sericite, and biotite) in the soils and rocks in the area. We also note that due to the high average temperatures all year round and excessive water consumption in the area, the optimum fluoride dose level should be lower than that recommended by the WHO.     

Determination of hemoglobin adduct of a musk xylene metabolite in trout as biomarker of exposure by gas chromatography mass spectrometry

Introduction Nitromusksarewidelyusedassyntheticfragranceingredientsinformulationofsoaps,laundrydetergents,lotions,andbody careproducts,andsoon.Thecommercial anddomesticuseanddischargeofthesecompoundsfrommunicipalsewagesystemshaveledtotheirubiquitousoccurr…     

Extraction of arsenic species in soils using microwave-assisted extraction detected by ion chromatography coupled to inductively coupled plasma mass spectrometry

We have developed a novel microwave-assisted extraction method for determining the arsenic (As) speciation in soils that is based on extraction with phosphate solutions, including orthophosphoric acid, ammonium dihydrogen orthophosphate, and ammonium hydrogen orthophosphate. The highest extracting efficiency was obtained with 1 M ortho-phosphoric acid solution as the extractant, and this efficiency is associated with the pH of the extractant. Total As content and As species in the soil extracts were determined by inductively coupled plasma mass spectrometry (ICP-MS) alone and by the combined ion chromatography (IC) with ICP-MS, respectively. The proposed extraction procedure was applied to National Institute of Standards and Technology (NIST) standard reference material (SRM) 2711 (Montana soil) as well as to environmental soil samples collected from the agricultural lands of Bangladesh. As(V) was detected in all the soil samples, and As(III) was detected in nine soils of the 20. These results of extractable As testing indicate that the extraction of As species mainly depends on the composition of the soils. The As speciation results also indicate that As adsorption is highly dependent on the iron, aluminum, and manganese concentrations in the soil. The stability of As species in the extracts was also studied.     

Arsenic contamination in groundwater in the Southeast Asia region

The adverse impact of groundwater contaminated with arsenic (As) on humans has been reported worldwide, particularly in Asian countries. In this study, we present an overview of the As crisis in the Southeast Asian region where groundwater is contaminated with naturally occurring As and where contamination has become more widespread in recent years. In this region more than 100 million people are estimated to be at risk from groundwater As contamination, and some 700,000 people are known so far to have been affected by As-related diseases. Despite investments exceeding many millions of dollars, there are still substantial knowledge gaps about the prevalence and impact of As, notably in its epidemiology, temporal variations, social factors, patient identification, treatment, etc. Arsenic-affected people in the affected regions also face serious social problems. Of major concern is the fact that many researchers from different countries have been conducting research in SE Asia region but with a lack of coordination, thus duplicating their work. There is an urgent need to coordinate these various studies to ensure better delivery of research outcomes. Further research is needed to improve field testing and monitoring of drinking water sources, and to develop new treatments for chronic As toxicity and new sources of safe drinking water.     

Large eddy simulation of dispersion around an isolated cubic building: evaluation of localized dynamic k_\mathrm{SGS}-equation sub-grid scale model

In the present study, the prediction accuracy of a dynamic one-equation sub-grid scale model for the large eddy simulation of dispersion around an isolated cubic building is investigated. For this purpose, the localized dynamic $k_\mathrm{SGS} $ -equation model (LDKM) is employed and the results are compared with the available experimental data and two other classic sub-grid scale models, namely, standard Smagorinsky–Lilly model (SSLM) and dynamic Smagorinsky–Lilly model (DSLM). It is shown that the three SGS models give results in good agreement with experiment. However, near the ground level of the leeward wall, dimensionless time-averaged concentration, $\langle K\rangle $ , profile is not quite similar to the experimental data. It is also demonstrated that the LDKM predicts the values of $\langle K\rangle $ on the roof, leeward and side walls more acceptably than the SSLM and DSLM. Whereas, the streamwise elongation of time-averaged structures of the plume shape is more over-estimated with the LDKM than with the other two SGS models. In terms of numerical difficulty, the LDKM is found to be stable and computationally reasonable. In addition, it does not suffer from a flow dependent constant such as the Smagorinsky coefficient employed in the SSLM model.