Removal of Pb(II) and Cd(II) ions from water by Fe and Ag nanoparticles prepared using electro-exploding wire technique

Purpose

This work aimed at investigating the adsorption of lead and cadmium onto Fe and Ag nanoparticles for use as a water contaminant removal agent as a function of particle type, sorbent concentration, and contact time.

Methods

Fe and Ag spherical nanoparticles were prepared in water by the lab-made electro-exploding wire (EEW) system and were investigated for their structure properties. Adsorption experiments were carried out at room temperature and pH 8.3 water solutions.

Results

The removal/adsorption of both Pb(II) and Cd(II) ions was found to be dependent on adsorbent dosage and contact time. Pb(II) adsorption onto Fe and Ag nanoparticles showed more or less similar efficiency and behavior. The kinetic data for the adsorption process obeyed pseudo second-order rate equations. The calculated equilibrium adsorption capacities (q _e) were 813 and 800 mg/g for Pb sorption onto Fe and Ag nanoparticles, respectively. Cd(II) ion adsorption onto Fe nanoparticles obeyed pseudo second-order rate equations with q _e equal to 242 mg/g, while their adsorption onto Ag nanoparticles obeyed pseudo first-order rate equations with q _e of 794 mg/g. The calculated q _es are in quite agreement with the experimental values. The removal/uptake mechanisms of metal ions involved interaction between the metal ion and the oxide/hydroxyl layer around the spherical metallic core of the nanoparticle in water medium.

Conclusion

Fe and Ag nanoparticles prepared using the EEW technique exhibited high potentials for the removal of metal ions from water with very high adsorption capacities, suggesting that the EEW technique can be enlarged to generate nanoparticles with large quantities for field or site water purification.     

Impediments to River Rehabilitation

Rehabilitation of river ecosystems is generally initiated when a river is no longer able to provide benefits to humans and other living beings. The major purposes of river rehabilitation projects are improving water quality, conserving nature, rehabilitating fisheries and riparian habitats, flood mitigation, and creating recreational opportunities. For a river rehabilitation project to be successful, it must have specific and clearly explained objectives, although these objectives will vary for each project depending upon factors such as economics, public demand, ecosystem benefits, and the like. In this article, we provide a critical analysis of the purposes that drive river rehabilitation projects and we identify and discuss impediments that can cause a project to deviate from its intended goals. We also discuss major constraints on rehabilitation efforts that can result in failed projects.     

Benchmarking Optical/Thermal Satellite Imagery for Estimating Evapotranspiration and Soil Moisture in Decision Support Tools

Generally, one expects evapotranspiration (ET) maps derived from optical/thermal Landsat and MODIS satellite imagery to improve decision support tools and lead to superior decisions regarding water resources management. However, there is lack of supportive evidence to accept or reject this expectation. We “benchmark” three existing hydrologic decision support tools with the following benchmarks: annual ET for the ET Toolbox developed by the United States Bureau of Reclamation, predicted rainfall‐runoff hydrographs for the Gridded Surface/Subsurface Hydrologic Analysis model developed by the U.S. Army Corps of Engineers, and the average annual groundwater recharge for the Distributed Parameter Watershed Model used by Daniel B. Stephens & Associates. The conclusion of this benchmark study is that the use of NASA/USGS optical/thermal satellite imagery can considerably improve hydrologic decision support tools compared to their traditional implementations. The benefits of improved decision making, resulting from more accurate results of hydrologic support systems using optical/thermal satellite imagery, should substantially exceed the costs for acquiring such imagery and implementing the remote sensing algorithms. In fact, the value of reduced error in estimating average annual groundwater recharge in the San Gabriel Mountains, California alone, in terms of value of water, may be as large as $1 billion, more than sufficient to pay for one new Landsat satellite.     

Polycyclic aromatic hydrocarbons and trace metals in mosque’s carpet dust of Riyadh,Saudi Arabia,and their health risk implications

The main objectives of this work were to identify and determine the concentrations of polycyclic aromatic hydrocarbons (PAHs) and trace metals in carpet dust samples from various mosques of the city of Riyadh and to assess the health risks associated with the exposure to these pollutants. Therefore, 31 samples of mosque’s carpet dust from Riyadh were collected. The results showed that 14 PAHs were present in the dust samples with concentrations ranged from 90 to 22,146 ng g^?1 (mean = 4096 ± 4277 ng g^?1) where low molecular weight compounds were dominant. The presence of PAHs were in the order of naphthalene > chrysene and benzo(b)fluoranthene > benzo(a)pyrene > acenaphthene and benzo(k)fluoranthene > pyrene and the absence of indeno(1,2,3-cd)pyrene and dibenz(a,h)anthracene. The diagnostic ratio coupled with principle component analysis (PCA) revealed mix sources of petrogenic from traffic, stack emission, and pyrogenic inputs from essence and perfumed wood burning. Trace metals were significant in the dust samples, and their concentrations decrease in the order of Zn, Mn, Cu, Cr, Pb, Ni, and V where Zn being the highest (94.4 ± 91.5 μg g^?1) and indium was the lowest (1.9 ± 9.3 μg g^?1). The trace metals were major in southern and central parts of Riyadh and followed the order of central Riyadh > southern Riyadh > western Riyadh > eastern Riyadh > northern Riyadh. Estimated risk based on the total PAHs was found to be 4.30 × 10^?11 for adult and 1.56 × 10^?11 for children. Elemental non-cancer risk for adults ranged from 7.9 × 10^?4 for Co to 7.58 × 10^?1 for Li and for children ranged from 3.70 × 10^?3 for Co to 3.54 for Li. Policy implication and mitigations of PAHs in Riyadh and Saudi Arabia were highlighted.     

Sorption of alkylphenols on Ebro River sediments: comparing isotherms with field observations in river water and sediments

This study reports sorption isotherms of the endocrine disruptors nonylphenol (NP) and octylphenol (OP) in three sediment samples from the Ebro River basin (NE Spain), with organic carbon fractions (f_OC) ranging from 0.0035 to 0.082 g_OC g⁻¹. All isotherms were fitted to the Freundlich model with slightly nonlinear exponents ranging from 0.80 to 0.94. The solubility of the compounds as well as the organic carbon (OC) content had the strongest influences on the sorption behavior of these compounds. Comparison of the laboratory-spiked samples with the native contamination of NP of 45 water and concurrent sediment samples resulted in reasonable matches between both data sets, even though the lowest concentrations in the field were not completely reached in laboratory tests. This good agreement indicates that sorption laboratory data can be extrapolated to environmental levels and therefore the distribution of nonylphenol between sediments and water can be predicted with a precision of one order of magnitude. Furthermore, laboratory experiments with simultaneous loading of NP and OP revealed negligible competition for sorption sites at low concentrations.     

Multi-criteria evaluation technique for SFI site identification of NORMS and oil industry waste disposal – Possibilities in Kuwait

Waste generation and accumulating quantities of oil field waste are a matter of environmental concern. This study proposes the Slurry Fracture Injection (SFI) technique as an alternative waste disposal method. The slurried solids injection waste disposal method is environmentally secure and permanent, leaving no future liabilities that must be risk-evaluated or priced. An entire waste stream comprising ground solids and waste water can be injected into deep and hydraulically secure target strata with no contamination of potable water-bearing formations or formations outside the target zone that may contain resources (gas and oil). The slurry injection method can be used to clean and reclaim landfills, oil pits and granular waste dumps. This article proposes a two-tier screening method for evaluating the feasibility of this technique and the identification of suitable target zones. A stringent environmental and process control monitoring program should complement the planning and operational period to ensure environmental protection, waste containment, and regulatory HSE compliance.     

Assessment of metal enrichments in tsunamigenic sediments of Pichavaram mangroves, southeast coast of India

The 26 December 2004-Tsunami has deposited sediments in the Pichavaram mangrove ecosystem, east coast of India. Ten surface and three core sediment samples were collected within thirty days of the event. High concentrations of Cd, Cu, Cr, Pb, and Ni were observed in the tsunamigenic sediments. With respect to Fe, Zn, and Mn, there was little variation as compared to pre-tsunami values. The geo-accumulation index was calculated in order to assess the contamination of heavy metals in the sediments. The sediments were extremely contaminated with respect to Cd and they showed moderate to strong contamination with respect to Cr, Pb and Ni. The study highlighted the future risk of enhanced metal pollution in near future in this mangrove ecosystem.     

Total metal levels in crayfish Astacus leptodactylus (Eschscholtz, 1823), and surface sediments in Lake Terkos, Turkey

The aim of this study was to determine the total metal accumulation (aluminium, copper, manganese, lead, cadmium and iron) in different organs and eggs of Astacus leptodactylus (Eschscholtz, 1823) and sediments total metal contents (aluminium, copper, manganese, lead, cadmium, iron, zinc, chromium, nickel) in Lake Terkos. Water and sediment samples were collected from two stations at two different depths (1 and 2 m) of Lake Terkos in May 2008. Crayfish samples were collected by trammel net at the same region. Primary hydrographic conditions, such as temperature (13.6–19.4°C), salinity (0.27–0.34‰), dissolved oxygen (7.04–12.30 mg l^???1) and pH (7.42–8.51), were recorded for each sampling point. Moreover, the total organic carbon (1.65–5.44%) and the total calcium carbonate contents (19.44–41.16%) of sediment samples were determined. According to the Turkish Food Codex (J Zool 26:283–288, 2002), the maximum allowable Pb and Cd levels in crayfish are 0.5 mg/kg wet weight. Accordingly, the Pb and Cd levels determined in A. leptodactylus samples are below this limit. However, when compared with the acceptable metal limits defined by WHO, Australian National Health and Medical Research Council and Ministry of Agriculture in United Kingdom (UK), it is clear that the Cu level is at the limit and the Cd results exceed the limit. When the metal contents in sediment samples from Lake Terkos are examined, it is seen that the Al, Fe, Mn, Ni and Cu contents are lower while Zn, Cr, Cd and Pb contents are higher than the crustal average values. The high values draw attention to the land-based domestic and industrial inputs. Lake Terkos sediments have high enrichment factors (EF) of Zn, Cr, Cd and Pb metals which corroborate this result. The low EFs of Fe, Ni and Cu are due to the natural (terrigeneous) inputs. Additionally, there is no Al, Fe, Ni and Cu metal enrichment in these lake sediments because of the low contamination factor (CF) values. However, it is moderately contaminated by Zn, Cr and Pb, and heavily contaminated by Cd.     

Agricultural reuse of reclaimed water and uptake of organic compounds: pilot study at Mutah University wastewater treatment plant, Jordan

The residues of polynuclear aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), chlorinated benzenes (CBs) and phenols were investigated for soil, wastewater, groundwater and plants. The uptake concentration of these compounds was comparatively determined using various plant types: Zea mays L., Helianthus annus L., Capsicum annum L., Abelmoschus esculentus L., Solanum melongena L. and Lycopersicon esculentum L. which were grown in a pilot site established at Mutah University wastewater treatment plant, Jordan. Soil, wastewater, groundwater and various plant parts (roots, leaves and fruits) samples were extracted in duplicate, cleaned up by open-column chromatography and analyzed by a multi-residue analytical methods using gas chromatography equipped with either mass selective detector (GC/MS), electron capture detector (GC/ECD), or flame ionization detector (FID). Environmentally relevant concentrations of targeted compounds were detected for wastewater much higher than for groundwater. The overall distribution profiles of PAHs and PCBs appeared similar for groundwater and wastewater indicating common potential pollution sources. The concentrations of PAHs, PCBs and phenols for different soils ranged from 169.34 to 673.20 microg kg(-1), 0.04 to 73.86 microg kg(-1) and 73.83 to 8724.42 microg kg(-1), respectively. However, much lower concentrations were detected for reference soil. CBs were detected in very low concentrations. Furthermore, it was found that different plants have different uptake and translocation behavior. As a consequence, there are some difficulties in evaluating the translocation of PAHs, CBs, PCBs and phenols from soil-roots-plant system. The uptake concentrations of various compounds from soil, in which plants grown, were dependent on plant variety and plant part, and they showed different uptake concentrations. Among the different plant parts, roots were found to be the most contaminated and fruits the least contaminated.