Michael Schuster

Quantification of Nanoscale Silver Particles Removal and Release from Municipal Wastewater Treatment Plants in Germany

The majority of pure silver nanoparticles in consumer products are likely released into sewer systems and usually end up in wastewater treatment plants (WWTPs). Research investigating the reduction in nanoscale silver particles (n-Ag-Ps) has focused on the biological treatment process, generally in controlled laboratory experiments. This study, analyzing the field-collected samples from nine municipal WWTPs in Germany, is the first to evaluate the reduction in n-Ag-Ps by mechanical and biological treatments in sequence in WWTPs. Additionally, the concentration of n-Ag-Ps in effluent was determined through two different methods that are presented here: novel ionic exchange resin (IER) and cloud point extraction (CPE) methods. The n-Ag-Ps concentrations in influent were all low (<1.5 μg/L) and decreased (average removal efficiency of ∼35%) significantly after mechanical treatment, indicating that the mechanical treatment contributes to the n-Ag-Ps removal. Afterward, more than 72% of the remaining n-Ag-Ps in the semi-treated wastewater (i.e., wastewater after mechanical treatment) were reduced by biological treatment. Together, these processes reduced 95% of the n-Ag-Ps that entered WWTPs, which resulted in low concentration of n-Ag-Ps in the effluents (<12 ng/L). For a WWTP with 520,000 t/d treatment capacity, we estimated that the daily n-Ag-Ps load in effluent discharge equated to about 4.4 g/d. Obviously, WWTPs are not potential point sources for n-Ag-Ps in the aquatic environment.

Selective determination of palladium by on-line column preconcentration and graphite furnace atomic absorption spectrometry

The present work describes a fully automated on-line column separation and preconcentration system for the determination of trace and ultratrace levels of palladium by graphite furnace atomic absorption spectrometry (GFAAS). Palladium is preconcentrated in a microcolumn which has been reversibly loaded with the selective complexing agent N,N-diethyl-N′-benzoylthiourea (DEBT). The palladium complex is eluted with 60 μl of ethanol and directly introduced into the graphite furnace. Sensitivity enhancements of 40, 70 and 200 can be obtained from sample volumes of 0.80, 1.86 and 4.85 ml, respectively. The corresponding detection limits are 51, 25 and 13 ng l−1, calculated by the calibration graph method (N=10, P=95%). In 6.5% (vv) nitric acid solutions, alkaline, alkaline-earth and base metal ions such as Cu(II), Fe(III), Co(II) and Ni(II) etc. as well as precious metals are tolerated up to concentrations of 10 g l−1 and more. The relative standard deviations of the linear calibration graphs are 1.7-2.9% (N=10, P=95%).

Distribution of platinum group elements (Pt, Pd, Rh) in environmental and clinical matrices: Composition, analytical techniques and scientific outlook: Status report.

Trace concentrations of the platinum group elements (PGE; here: Pt, Pd and Rh) play an important role in environmental analysis and assessment. Their importance is based on 1. their increasing use as active compartments in automobile exhaust catalysts, 2. their use as cancer anti-tumor agents in medicine. Due to their allergenic and cytotoxic potential, it is necessary to improve selectivity and sensitivity during analytical investigation of matrices like soil, grass, urine or blood.This paper summarizes the present knowledge of PGE in the fields of analytical chemistry, automobile emission rates, bioavailibility, toxicology and medicine.

Microwave-assisted digestion procedure for the determination of palladium in road dust

The present publication describes a microwave-assisted digestion procedure for the subsequent trace and ultra-trace analysis of palladium in road dust of varying origin. Digestion reagents are nitric acid, hydrogen peroxide and hydrofluoric acid. Boric acid is used as masking agent for fluoride ions to avoid removal of excess hydrofluoric acid by vaporization. After the three-step digestion procedure, a colorless and residue-free solution is obtained in which the determination of palladium can be directly performed using a recently developed highly selective on-line pre-concentration system, coupled with graphite furnace atomic absorption spectrometry (GF-AAS). Dust samples of varying origin (tunnel dust, road dust, filter dust from Frankfurt, Munich and Japan) and sampling dates (1987–2001) were investigated and characterized in detail with respect to matrix composition and palladium content. Validation of the analytical results was performed by recovery experiments.

Comparison of palladium and platinum in environmental matrices: Palladium pollution by automobile emissions?

A new type of automobile catalyst based on an active Pd/Rh-layer is presently being introduced into the European market. Accordingly, in order to establish baseline information, this work attempts to assess the magnitude of Pd emissions by automobile catalysts to date. Thus, a survey is presented on Pd and Pt levels detected in polluted environmental matrices (grass, soil, dust, sludges) as available from the literature. Additionally, Pd data measured by selective preconcentration/GF-AAS-detection in polluted grass, in a time series of sewage sludge ashes back to 1972, in dust, as well as in urban rain are presented. Since the data basis from the literature is partly inconsistent, the possible impact of different analytical attempts on the data is discussed. The relationship between Pt and Pd concentration from most of the results is between 5 and 10 (Pt/Pd). However, relations down to 0.04 are also reported, thus implying anthropogenic Pd input from additional sources.

Species selective preconcentration and quantification of gold nanoparticles using cloud point extraction and electrothermal atomic absorption spectrometry

The determination of metallic nanoparticles in environmental samples requires sample pretreatment that ideally combines pre-concentration and species selectivity. With cloud point extraction (CPE) using the surfactant Triton X-114 we present a simple and cost effective separation technique that meets both criteria. Effective separation of ionic gold species and Au nanoparticles (Au-NPs) is achieved by using sodium thiosulphate as a complexing agent. The extraction efficiency for Au-NP ranged from 1.01 ± 0.06 (particle size 2 nm) to 0.52 ± 0.16 (particle size 150 nm). An enrichment factor of 80 and a low limit of detection of 5 ng L(-1) is achieved using electrothermal atomic absorption spectrometry (ET-AAS) for quantification. TEM measurements showed that the particle size is not affected by the CPE process. Natural organic matter (NOM) is tolerated up to a concentration of 10 mg L(-1). The precision of the method expressed as the standard deviation of 12 replicates at an Au-NP concentration of 100 ng L(-1) is 9.5%. A relation between particle concentration and the extraction efficiency was not observed. Spiking experiments showed a recovery higher than 91% for environmental water samples.

Palladium exposure of barley: uptake and effects.

Motor vehicles are now equipped with exhaust gas catalytic converters containing rare metals, such as palladium (Pd), platinum and rhodium, as catalytic active materials, leading to significantly increased emission of these metals. Compared with platinum and rhodium, low concentrations of Pd have been shown to have more serious effects on cells and organisms. In the present study, uptake of Pd by barley and behaviour of Pd nanoparticles in nutrient solutions used to grow plants were observed in order to develop a model of Pd exposure of plant systems. Pd determination was performed using a selective separation and pre-concentration procedure, which was further developed for this study, and coupled to graphite furnace atomic absorption spectrometry. The results show that uptake of Pd depends on Pd particle diameter. Compared to other toxic metals, like mercury, Pd causes stress effects in leaves at lower concentrations in nutrient solutions. Furthermore, Pd particles are dissolved at different rates, depending on size, in the nutrient solution during plant growth.

Ultra-trace determination of silver nanoparticles in water samples using cloud point extraction and ETAAS

The continuing boom of nanotechnology leads to the question of the environmental fate of engineered nanoparticles. In this study an improved method for the quantification of silver nanoparticles (Ag-NPs) in environmental samples in the nanogram per litre range by means of cloud point extraction (CPE) and electrothermal atomic absorption spectrometry (ETAAS) is presented. Separation of nanoparticles from ionic silver species is achieved by addition of the ligand EDTA. A limit of detection (LoD) as low as 0.7 ng L−1 was obtained by optimizing the extraction conditions, the enrichment factor, and the ETAAS measurement conditions. In comparison to previously published studies the LoD for silver nanoparticles after CPE is improved by a factor of 10 because ETAAS detection requires no additional sample digestion after extraction. Samples of different complexity such as river water, treated and untreated municipal wastewater and synthetic solutions containing dissolved and particulate organic matter with a total organic carbon (TOC) content up to 10 mg L−1 were spiked with different concentrations of Ag-NPs and a high recovery (>80%) was found in all cases. Due to the low LoD and high tolerance levels for other particulate matter, TOC and ionic species, selective determination of Ag-NPs in municipal wastewater and also in the effluent of sewage treatment plants is now possible.

Long-term study of palladium in road tunnel dust and sewage sludge ash

The present work summarizes data about palladium contents of road tunnel dust from 1994 to 2007 and sewage sludge ash from 1972 to 2006. Since palladium is emitted from automotive catalytic converters as elemental particles, road dust is quiet useful to study traffic-related Pd emissions. Very high Pd values of up to 516 microg Pd kg(-1) were found in the road dust samples collected in 2007. Heavy metals of all urban emissions, also dental practice effluent, are enriched in sewage sludge ash and thus this matrix is useful for the documentation of palladium emission caused by the use of Pd alloys in dental medicine. In sewage sludge ash highest Pd contents of maximum 460 microg Pd kg(-1) were found in the years 1986-1997. In both matrices correlations of Pd content to Pd demand of industry are discussed.

Effective and selective extraction of noble metal nanoparticles from environmental water through a noncovalent reversible reaction on an ionic exchange resin

Capable of preserving the size and shape of nanoparticles, a novel method to effectively and selectively extract noble metal nanoparticles even at the 80 ng L(-1) level from real environmental water was designed and performed using a noncovalent reversible adsorption onto an ionic exchange resin.