Typical pollutants in bottom ashes from a typical medical waste incinerator

Incineration of medical waste (MW) is an important alternative way for disposal of this type of hazardous waste, especially in China because of the outbreak of severe acute respiratory syndromes (SARs) in 2003. Thus, far, fly ash has received much attention but less attention has been paid to bottom ash. In this study, bottom ash samples were collected from a typical MW incinerator, and typical pollutants including heavy metals and polycyclic aromatic hydrocarbons (PAHs) in the ash were examined. X-ray fluorescence spectroscopy results indicated that CaO, SiO₂ and Al₂O₃ were the main components of the bottom ash. Inductively coupled plasma-optical emission spectroscopy showed that the ash contained large amounts of heavy metals, including Zn, Ti, Ba, Cu, Pb, Mn, Cr, Ni and Sn. Most of the heavy metals (e.g., Ba, Cr, Ni, and Sn) presented in the residual fraction; whereas Mn, Pb and Zn presented in Fe–Mn oxides fraction, and Cu in organic-matter fraction. Toxicity characteristic leaching procedure tests indicated that the leached amounts of heavy metals were well below the limits. The sum of 16 US EPA priority PAHs (ΣPAHs) varied from 10.30 to 38.14 mg kg^?1, and the total amounts of carcinogenic PAHs ranged between 4.09 and 16.95 mg kg^?1, exceeding the limits regulated by several countries. This research provides basic information for the evaluation of the environmental risk of MW incinerator bottom ash.     

Assessment of polycyclic aromatic hydrocarbons (PAHs) in soil of a Natural Reserve (Isola delle Femmine) (Italy) located in front of a plant for the production of cement

Isola delle Femmine Natural Reserve is a very little isle about 15 km from the centre of Palermo, in front of a plant for the production of cement and about 600 m from coast. In the present research, profiles soil PAHs were obtained for 16 sites within the reserve and for 8 stations on the rural soil taken as reference. ∑PAHs, in the soil of investigated area, ranged from 35 to 545 μg/kg. With the aim to find the origin of PAHs in the soil of Isola delle Femmine, we compare the distribution of single analytes in the investigated area with those of the reference rural area (Monte Raffo Rosso), with those of atmospheric urban particulate collected at Palermo along with reported of emissions of some cement plants. The island's investigated area showed a high amount of 4- and 5-rings PAHs, whereas 3-ring PAHs are present mainly in the emission of cement plants (from literature). The percentage of 3-, 4-, 5- and 6-rings PAHs determined in samples of Isola delle Femmine are similar to those of the reference rural soils and to those of urban atmospheric particulate. Cement plant activity has a negligible weight on the presence of PAHs in the soil of Isola delle Femmine.     

Heavy metal pollution of coal mine-affected agricultural soils in the northern part of Bangladesh

Total concentrations of heavy metals in the soils of mine drainage and surrounding agricultural fields in the northern part of Bangladesh were determined to evaluate the level of contamination. The average concentrations of Ti, Mn, Zn, Pb, As, Fe, Rb, Sr, Nb and Zr exceeded the world normal averages and, in some cases, Mn, Zn, As and Pb exceeded the toxic limit of the respective metals. Soil pollution assessment was carried out using enrichment factor (EF), geoaccumulation index (I_geo) and pollution load index (PLI). The soils show significant enrichment with Ti, Mn, Zn, Pb, As, Fe, Sr and Nb, indicating inputs from mining activities. The I_geo values have revealed that Mn (1.24 ± 0.38), Zn (1.49 ± 0.58) and Pb (1.63 ± 0.38) are significantly accumulated in the study area. The PLIs derived from contamination factors indicate that the distal part of the coal mine-affected area is the most polluted (PLI of 4.02). Multivariate statistical analyses, principal component and cluster analyses, suggest that Mn, Zn, Pb and Ti are derived from anthropogenic sources, particularly coal mining activities, and the extreme proximal and distal parts are heavily contaminated with maximum heavy metals.     

Short-time effect of heavy metals upon microbial community activity

Microcalorimetry was applied to assess and compare the toxic effect of heavy metals, such as As, Cu, Cd, Cr, Co, Pb and Zn, on the soil microbial activities and community. About 1.0 g soil spiked 5.0 mg glucose and 5.0 mg ammonium sulfate, the microbial activities were recorded as power–time curves, and their indices, microbial growth rate constant k, total heat evolution Q_T, metabolic enthalpy ΔH_met and mass specific heat rate J_Q/S, were calculated. Comparing these thermodynamic parameters associated with growth yield, a general order of toxicity to the soil was found to be Cr > Pb > As > Co > Zn > Cd > Cu. When soil was exposed to heavy metals, the amount of bacteria and fungi decreased with the incubation time, and the bacterial number diminished sharply. It illustrates that fungi are more tolerant, and bacteria–fungi ratio would be altered under metal stress. To determine the status of the glucose consumed, a glucose biosensor with eggshell membrane was used to measure the remaining glucose in soil sample. Results showed that the time at which glucose was consumed completely was agreed with the microcalorimetric time to a large extent, and depended on the toxicity of heavy metals as well.     

The influence of dissolved organic carbon on sorption of heavy metals on urea-treated pine bark

A previous study showed considerably higher metal adsorption by urea-treated pine bark (UTB) compared to non-treated bark (NTB) at metal adsorption from their individual relatively concentrated solutions. Comparison of the sorption characteristics of the two pine barks at low but environmentally relevant metal concentrations, and investigation of the influence of pH and dissolved organic carbon (DOC) on the sorption process are the aims of the present study. Sorption of Cu²⁺, Ni²⁺, Zn²⁺ and Pb²⁺ on pine bark of the species Pinus sylvestris was measured in multi-metal solutions in the presence and absence of DOC. In the absence of DOC, UTB gave lower residual metal concentrations (2–7 μg/l for copper, 1–5 μg/l for nickel, <0.05 μg/l for zinc and lead) in the range of initial concentrations up to 0.7 mg/l, compared to NTB (6–15 μg/l for copper, 2–24 μg/l for nickel, 2–9 μg/l for zinc, 2–3 μg/l for lead). In the presence of DOC, sorption of Zn, Ni and Pb decreased by up to 75% depending on the DOC concentration. Metal sorption on UTB is less sensitive to pH and more adsorbed metal ions are retained compared to NTB. The potential use of urea-treated bark for treatment of waste water containing DOC and low concentrations of metals is discussed.     

Development of a coprecipitation system for the speciation/preconcentration of chromium in tap waters

A method for the speciation of chromium(III), chromium(VI) and determination of total chromium based on coprecipitation of chromium(III) with dysprosium hydroxide has been investigated and applied to tap water samples. Chromium(III) was quantitatively recovered by the presented method, while the recovery values for chromium(VI) was below 10%. The influences of analytical parameters including amount of dysprosium(III), pH, centrifugation speed and sample volume for the quantitative precipitation were examined. No interferic effects were observed from alkali, earth alkali and some transition metals for the analyte ions. The detection limits (k = 3, N = 15) were 0.65 μg/L for chromium(III) and 0.78 μg/L for chromium(VI). The validation of the presented method was checked by the analysis of certified reference materials.     

Antibacterial activity of silver nanoparticles stabilized on tannin-grafted collagen fiber

Bayberry tannin (BT), a typical plant polyphenol, was grafted on collagen fiber (CF) in different mass ratios. Subsequently, the BT-grafted CF (BT-CF) was used as carrier and stabilizer to prepare BT-CF stabilized silver nanoparticles (BT-CF-AgNPs). Scanning Electron Microscopy image of BT-CF-AgNPs showed that the BT-CF-AgNPs was in ordered fibrous state. X-ray Diffraction patterns and Transmission Electron Microscopy images offered evidence that the Ag nanoparticles were well dispersed on BT-CF. Fourier Transform-Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS) investigations revealed that the Ag NPs were stabilized by the phenolic hydroxyls and quinones of BT on CF through electron donation/acception interaction. Antibacterial experiments demonstrated that BT-CF-AgNPs exhibited high antibacterial activity. When cell suspensions of Escherichia coli and Staphylococcus aureus (10⁴–10⁵ cfu/mL) were contacted with BT_0.19-CF-AgNPs (mass ratio of BT to CF = 0.19, conc. of Ag = 8 μg/mL) at 310 K under constant shaking, the number of cells went down to zero within 2 h. In addition, the minimal inhibitory concentration of BT_0.19-CF-AgNPs against Escherichia coli, Staphylococcus aureus, Penicillium glaucum and Saccharomyces cerevisiae was 2 μg/mL, 4 μg/mL, 6 μg/mL and 12 μg/mL Ag, respectively. During recycling use, the antibacterial activity of BT_0.19-CF-AgNPs against Escherichia coli can last for 5 cycles. These facts suggest that BT-CF-AgNPs can be used as a new and effective antibacterial agent.     

Reuse of water purification sludge as raw material in cement production

The feasibility of partial replacement of siliceous raw material for cement production with water purification sludge (WPS) was investigated by X-ray diffraction, free-lime analysis, compressive strength testing and toxicity characteristics leaching procedure (TCLP). It is found that WPS has no negative effects on the consumption of free lime and the formation of clinker minerals. The samples with WPS from 4 to 10 wt.% have higher 3 days and 7 days strengths than the control. After 28 days, however, only WPS replacements <7% increased the strength of samples. It is noteworthy that heavy metals in WPS were almost completely incorporated into the clinkers, and up to 28 days the heavy metals were not detected in the leachates. From the above results of clinker minerals, compressive strength and leaching tests, it can be concluded that WPS has the potential to be utilized as an alternative raw material in cement production.     

Rhizofiltration using sunflower (Helianthus annuus L.) and bean (Phaseolus vulgaris L. var. vulgaris) to remediate uranium contaminated groundwater

The uranium removal efficiencies of rhizofiltration in the remediation of groundwater were investigated in lab-scale experiments. Sunflower (Helianthus annuus L.) and bean (Phaseolus vulgaris L. var. vulgaris) were cultivated and an artificially uranium contaminated solution and three genuine groundwater samples were used in the experiments. More than 80% of the initial uranium in solution and genuine groundwater, respectively, was removed within 24 h by using sunflower and the residual uranium concentration of the treated water was lower than 30 μg/L (USEPA drinking water limit). For bean, the uranium removal efficiency of the rhizofiltration was roughly 60–80%. The maximum uranium removal via rhizofiltration for the two plant cultivars occurred at pH 3–5 of solution and their uranium removal efficiencies exceeded 90%. The lab-scale continuous rhizofiltration clean-up system delivered over 99% uranium removal efficiency, and the results of SEM and EDS analyses indicated that most uranium accumulated in the roots of plants. The present results suggested that the uranium removal capacity of two plants evaluated in the clean-up system was about 25 mg/kg of wet plant mass. Notably, the removal capacity of the root parts only was more than 500 mg/kg.     

Attenuated effects of chitosan-capped gold nanoparticles on LPS-induced toxicity in laboratory rats

The impact of nanoparticles in medicine and biology has increased rapidly in recent years. Gold nanoparticles (AuNP) have advantageous properties such as chemical stability, high electron density and affinity to biomolecules. However, the effects of AuNP on human body after repeated administration are still unclear. Therefore, the purpose of the present study was to evaluate the effects of gold-11.68 nm (AuNP1, 9.8 μg) and gold-22.22 nm (AuNP2, 19.7 μg) nanoparticles capped with chitosan on brain and liver tissue reactivity in male Wistar rats exposed to lipopolysaccharide (LPS from Escherichia coli serotype 0111:B4, 250 μg) upon 8 daily sessions of intraperitoneal administration. Our results suggest that the smaller size of chitosan-capped AuNP shows the protective effects against LPS-induced toxicity, suggesting a very high potential for biomedical applications.     

Influence of EDTA washing on the species and mobility of heavy metals residual in soils

Aiming to estimate the potential risk of ethylenediaminetetraacetic acid (EDTA)-enhanced soil washing, the heavy metal species and their mobility in the washed soil under different combinations were investigated by batch leaching tests and the sequential extraction procedure. Results demonstrate that the metal removal efficiency was rather low (less than 12%), partially due to the significant Ca dissolution and strong bonding between metals and the soil as well as the insufficient EDTA dosage. The washing combination of 0.0005 M EDTA and half-an-hour washing can enhance the instant mobility of Ni, Zn and Pb possibly owing to the slow detachment of EDTA-destabilized metals. Metal fractionation also exhibits the corresponding increase in their labile exchangeable fractions. Therefore, a more concentrated EDTA solution for a longer duration often decreased their mobility. The increase in some fractions of a curtain metal implies the redistribution of this metal during the EDTA soil washing. The pathway of such a redistribution may vary for different metals, but the redistribution to organic matter is often a slow process, while that to carbonates or Fe/Mn oxides is a faster one and even may occur in a half hour washing with 0.0005 M EDTA solution. These redistribution processes may also increase the metal chemical availability. Therefore, we should prudently control the chelating reagent concentration and washing duration to finally minimize the mobility and availability of the remaining heavy metals when designing the soil washing for the remediation of metal-contaminated soils.     

Recycling of carbon fibers from carbon fiber reinforced polymer using electrochemical method

In this research, we proposed an electrochemical method for the recycling of carbon fibers from carbon fiber reinforced polymer (CFRP). Experiments were designed with different solution concentrations (3%, 10%, and 20% NaCl) and various levels of applied current (4 mA, 10 mA, 20 mA, and 25 mA) so as to identify the significant parameters that affect carbon fiber recycling efficiency. The recycled carbon fibers were characterized by using the single fiber tensile strength test, SEM, XRD, and XPS techniques. Test results showed that the maximum tensile strength of the reclaimed carbon fibers was 80% of the virgin carbon fibers (VCF). The increase in electrolyte concentration did not improve the recycling efficiency but resulted in severe oxidation and chlorination on the surface of recycled carbon fibers. From the experimental results, it can be concluded that the recycling of carbon fibers with electrochemical method is simple, effective, and economical.     

Novel,simple and reproducible method for preparation of composite hierarchal porous structure scaffolds

Demand to develop a simple and adaptable method for preparation the hierarchical porous scaffolds for bone tissue regeneration is ever increasing. This study presents a novel and reproducible method for preparing the scaffolds with pores structure spanning from nano, micro to macro scale. A macroporous Sr-Hardystonite (Sr–Ca₂ZnSi₂O₇, Sr–HT) scaffold with the average pore size of ~ 1200 μm and porosity of ~ 95% was prepared using polymer sponge method. The struts of the scaffold were coated with a viscous paste consisted of salt (NaCl) particles and polycaprolactone (PCL) to provide a layer with thickness of ~ 300–800 μm. A hierarchical porous scaffold was obtained with macro, micro and nanopores in the range of 400–900 μm, 1–120 μm and 40–290 nm, after salt leaching process. These scales could be easily adjusted based on the starting foam physical characteristics, salt particle size, viscosity of the paste and salt/PCL weight ratio.     

SAFARI engineering model 50 mK cooler

SAFARI is an infrared instrument developed by a European based consortium to be flown in SPICA, a Japanese led mission. The SAFARI detectors are transition edge sensors (TES) and require temperatures down to 50 mK for their operation. For that purpose we have developed a hybrid architecture based on the combination of a 300 mK sorption stage and a small adiabatic demagnetization stage. An engineering model has been designed to provide net heat lifts of 0.4 and 14 μW respectively at 50 and 300 mK, with an overall cycle duration of 48 h and a duty cycle objective of over 75%. The cooler is self-contained, fits in a volume of 156 × 312 × 182 mm and is expected to weigh 5.1 kg. It has been designed to withstand static loads of 120 g and a random vibration level of 21 g RMS.     

A novel ionic liquid/micro-volume back extraction procedure combined with flame atomic absorption spectrometry for determination of trace nickel in samples of nutritional interest

A simple, highly sensitive and environment-friendly method for the determination of trace amount of nickel ion in different matrices is proposed. In the preconcentration step, the nickel from 10 mL of an aqueous solution was extracted into 500 μL of ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate [C₄MIM][PF₆], containing PAN as complexing agent. Subsequently, the PAN complex was back-extracted into 250 μL of nitric acid solution, and 100 μL of it was analyzed by flow injection flame atomic absorption spectrometry (FI-FAAS). The main parameter influencing the extraction and determination of nickel, such as pH, concentration of PAN, extraction time and temperature, ionic strength, and concentration of stripping acid solution, were optimized. An enhancement factor of 40.2 was achieved with 25 mL sample. The limit of detection (LOD) and quantification obtained under the optimum conditions were 12.5 and 41.0 μg L^?1, respectively. To validate the proposed methods two certified reference materials 681-I and BCR No. 288 were analyzed and the results were in good agreement with the certified values. The proposed method was successfully applied to determination of nickel in water samples, rice flour and black tea.     

Characterization of native microalgal strains for their chromium bioaccumulation potential: Phytoplankton response in polluted habitats

Due to its various uses, Cr contamination has become widespread in a diverse array of environments. The present study was carried out during 2007–2008 to investigate the accumulation potential of metals (Cr, Cu, Fe, Mn, Ni and Zn) and metalloid (As) by green (GA) and blue green (BGA) microalgae growing naturally in selected Cr-contaminated sites in districts Unnao and Kanpur (Uttar Pradesh, India). This investigation is a preliminary work to identify suitable native microalgae for biomonitoring and phytoremediation purposes. A total of 22 GA and 11 BGA were encountered in three seasons (summer, rainy and winter). Among these, the accumulation potential was evaluated in high biomass producing strains of BGA (three) and GA (nine). The maximum accumulation of Cr was shown by Phormedium bohneri (8550 μg g^?1 dw) followed by Oscillatoria tenuis (7354 μg g^?1 dw), Chlamydomonas angulosa (5325 μg g^?1 dw), Ulothrix tenuissima (4564 μg g^?1 dw), and Oscillatoria nigra (1862 μg g^?1 dw); all of which demonstrated a transfer factor of >10% for Cr. The results also indicate that the phytoplankton diversity was modified by Cr pollution. BGA represented the dominant community where Cr concentration was higher (11.84 and 2.27 mg L^?1) (r = 0.695), whereas GA showed negative correlation with respect to Cr concentration (r = ?0.567). In conclusion, different algal species were able to grow in Cr-contaminated sites and to accumulate significant amounts of Cr with a high transfer factor.     

Novel Ag@TiO2 nanocomposite synthesized by electrochemically active biofilm for nonenzymatic hydrogen peroxide sensor

A novel nonenzymatic sensor for H₂O₂ was developed based on an Ag@TiO₂ nanocomposite synthesized using a simple and cost effective approach with an electrochemically active biofilm. The optical, structural, morphological and electrochemical properties of the as-prepared Ag@TiO₂ nanocomposite were examined by UV–vis spectroscopy, X-ray diffraction, transmission electron microscopy and cyclic voltammetry (CV). The Ag@TiO₂ nanocomposite was fabricated on a glassy carbon electrode (GCE) and their electrochemical performance was analyzed by CV, differential pulse voltammetry and electrochemical impedance spectroscopy. The Ag@TiO₂ nanocomposite modified GCE (Ag@TiO₂/GCE) displayed excellent performance towards H₂O₂ sensing at ? 0.73 V in the linear response range from 0.83 μM to 43.3 μM, within a detection limit and sensitivity of 0.83 μM and ~ 65.2328 ± 0.01 μAμM^? 1 cm^? 2, respectively. In addition, Ag@TiO₂/GCE exhibited good operational reproducibility and long term stability.     

Sensitive detection of mercury (II) ion using water-soluble captopril-stabilized fluorescent gold nanoparticles

In our work, a simple, facile, and green method was developed for the synthesis of water-soluble and well-dispersed fluorescent gold nanoparticles (Au NPs) within 5 min, using captopril as a capping agent. The as-prepared Au NPs showed strong emission at 414 nm, with a quantum yield of 5.5%. The fluorescence of the Au NPs can be strongly quenched by mercury (II) ion (Hg^2 +) due to the stronger interactions between thiolates (RS^?) and Hg^2 +. It was applied to the detection of Hg^2 + in water samples in the linear ranges of 0.033–0.133 μM and 0.167–2.500 μM, with a detection limit of 0.017 μM. Therefore, the as-prepared Au NPs can meet the requirement for monitoring Hg^2 + in environmental samples.     

Spot friction stir welding of low carbon steel plates preheated by high frequency induction

In this study, high frequency induction heating assisted spot friction stir welding was applied to 1.6 mm thick S12C low carbon steel plates. With the same welding parameter including an applied load of 2500 kg, rotation speed of 800 rpm and dwell time of 2 s, the average grain size in the stir zone slightly increased from 12.9 μm for the welds without preheating to 14.8 μm when 10 s preheating was used. However, larger joint interface was formed within the stir zone of the welds with preheating and therefore the bonding strength can be significantly increased. As a result, the shear tensile load of the joint increased from 8 kN to12.4 kN with preheating and the joint fractured through the plug failure mode rather than interfacial failure mode. It was revealed that the frictional heat generated between the rotating tool and the work-piece can be reduced to obtain sound welds by means of high frequency induction preheating.     

Experimental investigation of heat transfer through porous media in superfluid helium

An experimental investigation of heat transfer through porous media in superfluid helium has been conducted in the framework of the development of porous electrical insulations for superconducting magnet cables cooled by superfluid helium. Several types of porous media with different characteristics were tested and, in particular, samples with pore size diameters of 0.1 μm, 1 μm, 2 μm, 10 μm and 20 μm. Temperature and pressure were measured between an insulating inner bath and the cryostat bath, communicating only through the porous medium. The cryostat bath is held constant all along the measurement and, for each sample, the tests are performed for bath temperature from 1.4 K to 2.1 K with 0.1 K increment. Depending on the porous medium average pore size diameter, different flow regimes are observed: for porous media with a pore diameter of 0.1 and 1 μm, only the Landau regime is observed whereas for porous media with a pore diameter of 2 μm, we observed the Landau regime and the Gorter-Mellink regime. For samples with a pore diameter of 10 and 20 μm, measurements only permitted to detect the Gorter-Mellink regime. In the laminar regime, the permeability of the samples was determined and it was found that the permeability is constant for bath temperature above 1.9 K whereas it increases as the bath temperature decreases from 1.8 K to 1.4 K. For samples with a pore size diameter of 10 and 20 μm, measurement permits only to observe the turbulent regime and the analysis exhibits a constant average tortuosity for each samples, independently of the bath temperature.