Flotation kinetics of aluminum powders derived from waste crystalline silicon solar cells and its comparison between batch,continuous and column flotation practices

Journal of Material Cycles and Waste Management - In this study, floatability rate of aluminum (Al) powders was analyzed for the purpose of separating valuable resources from residual materials in...     

Determination of PCDD/Fs and dioxin-like PCBs in fish oils for feed ingredients by congener-specific chemical analysis and CALUX bioassay

The present research was intended to determine the suitability of the CALUX assay as a screening method for dioxins in fish oil used as a feed ingredient in Japan. Alteration of TEQ in fish oil according to newly proposed toxic equivalency factors (TEF) is also discussed. In the analysis, polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs) in 41 fish oil samples were determined by using high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS) and CALUX bioassay. The mean TEQ values derived from 1998 WHO-TEF of PCDD/Fs and DL-PCBs were 2.6 and 9.9 pg g(-1) (ww), respectively. The levels of TEQ derived from the recently re-evaluated 2005 WHO-TEF were slightly lower than those of the former in both groups. Notably, the contribution of mono-ortho DL-PCBs to total 2005 WHO-TEQ was considerably decreased compared to the case of 1998 WHO-TEQ, resulting from the reduction in its TEF values, while the non-ortho DL-PCBs contribution was increased. The mean TEQ determined by CALUX assay for PCDD/Fs was approximately three times higher, whereas DL-PCBs was approximately two times lower than WHO-TEQ determined by HRGC/HRMS; the sum of PCDD/Fs and DL-PCBs was very similar by both methods. The correlation coefficients of TEQ between the CALUX assay and HRGC/HRMS analysis were 0.84, 0.89, and 0.90 for PCDD/Fs, DL-PCBs, and the sum, respectively. These results suggest that the CALUX assay is a very useful method for the screening of dioxin-related compounds in fish oils.     

Formation of cyanide ion or cyanogen chloride through the cleavage of aromatic rings by nitrous acid or chlorine. IX. On the reactions of chlorinated, nitrated, carboxylated or methylated benzene derivatives with hypochlorous acid in the presence of ammonium ion

Chlorinated, nitrated, carboxylated or methylated benzenes, phenols and anilines reacted with chloramine to give cyanogen chloride, independently of the positions and the numbers of the substituents. Among these compounds, 2,4,6-trichlorophenol afforded cyanogen chloride in a relatively high yield of 13.3%, and the intermediates in the reaction were 2,6-dichloro-1,4-benzoquinone-4-(N-chloro)imine and 4,6-dichloro-1,2-benzoquinone-2-(N-chloro)-imine, of which the latter was the main intermediate.     

Quantitative determination of Escherichia coli based on the electrochemical measurement of bacterial catalase activity using H2O2-selective organic/inorganic-hybrid sol-gel film-modified Pt electrode

Quantitative determination of Escherichia coli (E. coli) concentration was achieved by measuring the intrinsic catalase activity of E. coli using novel H₂O₂-selective organic/inorganic-hybrid sol-gel film-modified platinum (Pt) wire electrode. This hybrid sol-gel film is composed of three kinds of organosilanes and two biopolymers (i.e., chitosan and bovine serum albumin), and exhibited an excellent permselectivity toward H₂O₂ based on a size-exclusive mechanism. The steady-state anodic current for 100 [xmol/L H₂O₂ at +0.6 V (vs. Ag/AgCl) in 0.1 mol/L phosphate buffer (pH 6.5) solution was apparently diminished by the addition of E. coli samples, due to the decomposition of H₂O₂ by intrinsic catalase activity of E. coli. The time-dependent decrease in current (–AI/At) was significantly dependent on the E. coli concentration. The –AI/At was enhanced by the permeabilization pretreatment of E. coli samples with the mixed solution of polymyxin B and lysozyme. This H₂O₂-selective organic/inorganic-hybrid sol-gel film-modified platinum (Pt) wire electrode allowed quantitative determination of E. coli concentration ranging from 10⁶ to 10⁹ CFU/mL within 30 min. This method required no label and complicated procedure, and allowed rapid, simple and cost-effective quantitative electrochemical determination of catalase-positive bacteria.     

Highly sensitive flow-biosensor for toxic phenolic compounds using tyrosinase and acridine orange-adsorbed carbon felt

Tyrosinase (TYR, EC 1.14.18.1) was physically adsorbed onto a carbon felt (CF) together with acridine orange (AO). Coadsorption of AO was essential to prevent the denaturation of the TYR at the CF surface. The resulting TYR and AO-coadsorbed CF (TYR/AO-CF) was successfully utilized as a detection unit of novel and highly sensitive amperometric flow-biosensor for toxic chlorophenol compounds. Standard solutions of phenolic compounds (200 μL) were injected, and the cathodic peak currents due to the reduction current of o-quinones produced by the TYR-catalyzed oxidation (phenolase activity) were detected at the applied potential of ?50 mV vs. Ag/AgCl. In this reaction, the electrochemically generated catechol compounds from o-quinones are re-oxidized repeatedly by catecholase activity of the TYR, leading to a sufficient amplified signal. The TYR/AO-CF exhibited much higher selectivity toward p-chlorophenol as compared with other chlorophenol compounds. When 0.1 mol/L phosphate buffer (pH 7.0) was used as a carrier at flow rate of 3.0 mL/min, cathodic peaks for p-chlorophenol was linear in the concentration range between 0.1 and 10 [xmol/L (sensitivity: 1.41(mA-L)/mmol) with sampling rate (30 samples/h), and the detection limit ofp-chlorophenol was found to be 2.13 ? 10⁸ mol/L (S/N = 3. The ratio of signal and noise is 3). The TYR/AO-CF kept more than 80% of original activity after the storage in 0.1 mol/L phosphate buffer (pH 7.0) containing 0.2 mmol/L AO at 4°C.     

Sequential flotation of 4 components in silicon-based waste solar cells

Journal of Material Cycles and Waste Management - Si, Al, Cu, and Ag particles’ mixture which mainly composes pulverized silicon-based waste solar cells were individually separated by the...     

Perfluorinated organic compounds in human blood serum and seminal plasma: a study of urban and rural tea worker populations in Sri Lanka

Concentrations and accumulation of 13 fluorinated organic compounds (FOCs) in human sera and seminal plasma were measured in an Asian developing country, Sri Lanka. Six of the FOCs, PFOS (perfluorooctanesulfonate), PFHS (perfluorohexanesulfonate), PFUnA (perfluoroundecanoic acid), PFDA (perfluorodecanoic acid), PFNA (perfluorononanoic acid) and PFOA (perfluorooctanoic acid), were detected in all of the sera samples. Measurable quantities of two main perfluorosulfonates, PFOS and PFHS, were found in all seminal plasma samples. The detection frequency of the predominant perfluoroalkylcarboxylate, PFOA, in seminal plasma was >70%. Accumulation of PFOS in sera was significantly positively correlated with PFOA, PFHS and PFNA. Positive linear regressions were also found between PFNA and PFUnA and PFNA and PFDA suggesting that these compounds may have a similar origin of exposure and accumulation. Significantly positive associations were observed for partitioning of both PFOS and PFNA between sera and seminal plasma. The accumulation of FOCs was not significantly different in sera from Colombo (urban population) and Talawakele (rural conventional tea workers). However, the Haldummulla population (rural organic tea workers) had relatively lower exposure to FOCs compared to the other two groups, urban and rural conventional tea workers. Concentrations of FOCs in Sri Lanka were similar to those reported for industrialized countries suggesting that human exposure to such chemicals is widespread even in developing countries. The novel finding of FOCs in human seminal plasma implies that further studies are needed to determine whether long-term exposure in humans can result in reproductive impairments.     

Physicochemical characteristics of carbonaceous adsorbent for dioxin-like polychlorinated biphenyl adsorption

It has been known that dioxin-like polychlorinated biphenyls (DL-PCBs) are present in almost all types of environments worldwide. Activated carbon treatment has been expected for the removal of DL-PCBs because it is a simple and low-cost removal technology. In the present study, the physicochemical properties of activated carbon were investigated to identify the characteristics of 16 different types of activated carbon on adsorption properties for DL-PCBs. To accomplish this, micropore volume, and pore diameter were calculated by t-plot analysis and the mesopore volume was analyzed by the Barrett-Joyner-Halenda (BJH) method. In addition, the Brunauer-Emmett-Teller (BET) surface area, pH, metal elements, and surface acid functional groups were analyzed. Then, adsorption experiments using DL-PCB in hexane solution were conducted, and the relationship between adsorption and physicochemical properties of activated carbon was investigated. The results showed that activated carbons having a surface area of 700-1200 m² g⁻¹ and micropores with diameters of about 0.7-0.8 nm exhibited high activity for the adsorption of PCBs. The results also clearly showed that the mesopore volume of activated carbon influenced the adsorption rate and the equilibrium adsorption.     

Suppressive effect of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and dioxin-like polychlorinated biphenyls transfer from feed to eggs of laying hens by activated carbon as feed additive

In this study, we investigated the suppressive effect of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (DL-PCBs) transfer from the feed to the eggs of laying hens by using activated carbon as a feed additive. Four groups of six hens (White Leghorn egg-layers; age, 11 weeks) were housed as two control groups and two exposure groups for a period of 20 weeks. Two control groups were fed with either the basal feed “Control” or basal feed additing activated carbon “Control + C”. Another two exposure groups were fed with feed contaminated (about 6 ng TEQ kg⁻¹ feed) by standard solutions of PCDDs/PCDFs and DL-PCBs “Exposure” alone and contaminated feed adding activated carbon “Exposure + C”. There was no significant effect on each groups for the growth rate, biochemical blood components, and egg production: these were around the standard levels for poultry in general. Moreover the results in this study showed the availability of activated carbon as a feed additive owing to the reduction in the risk of food pollution by PCDDs/PCDFs and DL-PCBs. The concentration in the eggs of the Exposure group gradually increased following the start of egg-laying but reached a steady state after about 1 month. In contrast, the concentration for the Exposure + C group was stationary and below the maximum EU level (6 pg TEQ g⁻¹ fat). In comparison to the Exposure group, the Exposure + C group showed a significant decline in the percentage of bioaccumulation into the egg. This reduction due to activated carbon was also observed in the muscle and abdominal fat. The reductions were compound- and congener-dependent for DL-PCBs as follows: PCDDs/PCDFs, non-ortho-PCBs, and mono-ortho-PCBs were more than 90%, 80%, and 50%, respectively, irrespective of the type of tissues. Fat soluble vitamin concentrations in the eggs of the Exposure + C group showed lower trends than the Exposure group. The γ-tocopherol and α-tocopherol concentrations in eggs of Exposure + C group showed a significant reduction of about 40%. However, the addition of activated carbon into animal feed could obviate the remote potential for accidents causing unintentional food pollution with PCDDs/PCDFs and DL-PCBs.