The phytochelatin transporters AtABCC1 and AtABCC2 mediate tolerance to cadmium and mercury.

Heavy metals such as cadmium (Cd) and mercury (Hg) are toxic pollutants that are detrimental to living organisms. Plants employ a two-step mechanism to detoxify toxic ions. First, phytochelatins bind to the toxic ion, and then the metal-phytochelatin complex is sequestered in the vacuole. Two ABCC-type transporters, AtABCC1 and AtABCC2, that play a key role in arsenic detoxification, have recently been identified in Arabidopsis thaliana. However, it is unclear whether these transporters are also implicated in phytochelatin-dependent detoxification of other heavy metals such as Cd(II) and Hg(II). Here, we show that atabcc1 single or atabcc1 atabcc2 double knockout mutants exhibit a hypersensitive phenotype in the presence of Cd(II) and Hg(II). Microscopic analysis using a Cd-sensitive probe revealed that Cd is mostly located in the cytosol of protoplasts of the double mutant, whereas it occurs mainly in the vacuole of wild-type cells. This suggests that the two ABCC transporters are important for vacuolar sequestration of Cd. Heterologous expression of the transporters in Saccharomyces cerevisiae confirmed their role in heavy metal tolerance. Over-expression of AtABCC1 in Arabidopsis resulted in enhanced Cd(II) tolerance and accumulation. Together, these results demonstrate that AtABCC1 and AtABCC2 are important vacuolar transporters that confer tolerance to cadmium and mercury, in addition to their role in arsenic detoxification. These transporters provide useful tools for genetic engineering of plants with enhanced metal tolerance and accumulation, which are desirable characteristics for phytoremediation.

Gas-phase elemental mercury removal in a simulated combustion flue gas using TiO2 with fluorescent light.

UNLABELLED: A previously proposed technology incorporating TiO2 into common household fluorescent lighting was further tested for its Hg0 removal capability in a simulated flue-gas system. The flue gas is simulated by the addition of O2, SO2, HCl, NO, H2O, and Hg0, which are frequently found in combustion facilities such as waste incinerators and coal-fired power plants. In the O2 + N2 + Hg0 environment, a Hg0 removal efficiency (etaHg) greater than 95% was achieved. Despite the tendency for etaHg to decrease with increasing SO2 and HCl, no significant drop was observed at the tested level (SO2: 5-300 ppm, HCl: 30-120 ppm(v)). In terms of NO and moisture, a significant negative effect on etaHg was observed for both factors. NO eliminated the OH radical on the TiO2 surface, whereas water vapor caused either the occupation of active sites available to Hg0 or the reduction of Hg0 by free electron. However, the negative effect of NO was minimized (etaHg > 90%) by increasing the residence time in the photochemical reactor. The moisture effect can be avoided by installing a water trap before the flue gas enters the Hg0 removal system. IMPLICATIONS: This paper reports a novel technology for a removal of gas-phase elemental mercury (Hg0) from a simulated flue gas using TiO2-coated glass beads under a low-cost, easily maintainable household fluorescent light instead of ultraviolet (UV) light. In this study, the effects of individual chemical species (O2, SO2, HCl, NO, and water vapor) on the performance of the proposed technology for Hg0 removal are investigated. The result suggests that the proposed technology can be highly effective, even in real combustion environments such as waste incinerators and coal-fired power plants.

Evaluation of Meibum Lipid Composition According to Tear Interferometric Patterns: RRH: Meibum Composition According to Interferometric Patterns.

PURPOSE: To determine the relationship between tear film interferometric patterns and properties of lipid, including rheological properties. DESIGN: Prospective, cross-sectional laboratory investigation. METHOD: This study included 105 subjects (94 dry eye patients and 11 normal participants). The subjects were divided into 3 categories (group 1, normal; group 2, thin; and group 3, irregular) according to interferometric patterns. According to tear interferometric patterns, ultra-performance liquid chromatography (LC) quadrupole-linear ion trap/mass spectrometry (MS)-based analysis was used to investigate lipid profiling of meibum. Rheological properties were examined by using a Langmuir-Blodgett trough with saline solution. RESULTS: Normal subjects showed Pearl-like patterns, and dry eye patients showed either irregular or thin patterns. Group 2 tended to be the evaporative type, and group 3 tended to be the aqueous-deficient type. Lipid profiling using LC-MS identified 280 lipid species of 25 lipid classes. In the meibum of the patient groups, the content of cholesteryl esters and nonpolar lipids was lower than that in the normal group. However, the content of polar lipids such as sphingolipids and phospholipids in the patient groups was higher than that in the normal group. Rheological properties showed that the lift-off areas were comparable among the 3 groups and the surface tension was the highest in group 1, followed by group 3 and group 2. CONCLUSIONS: The findings of this study suggest that tear interferometric patterns are associated with lipid profiling of meibum and its rheological properties. These results may contribute toward the development of new treatment modalities.

Stabilization and solidification of elemental mercury for safe disposal and/or long-term storage.

A simple and highly effective stabilization/solidification (S/S) technology of elemental mercury using only sulfur with paraffin is introduced. First, elemental mercury is mixed with an excess of sulfur powder and heated to 60 degrees C for 30 min until elemental mercury is converted into mercuric sulfide (HgS black, metacinnabar) (Step 1). Then, metacinnabar with additional sulfur is poured into liquid paraffin (Step 2). Finally, the mixture is melted at 140 degrees C and settles to the bottom of the vessel where it cools and solidifies under the layer of liquid paraffin (Step 3). The proposed S/S method with sodium sulfide nonahydrate (Na2S x 9H2O) as an additive is also tested for comparison. The average toxicity characteristic leaching procedure test values are 6.72 microg/L (no additive) and 3.18 microg/L (with additive). Theses concentrations are well below the Universal Treatment Standard (25 microg/L). Effective diffusion coefficient evaluated from accelerated leach test and average headspace concentration of Hg vapor after 18 hr are 3.62 x 10(-15) cm2/sec, 0.55 mg/m3 (no additive) and 5.86 x 10(-13) cm2/sec, 0.25 mg/m3 (with additive).

A novel method for extraction, quantification, and identification of microplastics in CreamType of cosmetic products.

The objective of this study was to develop an accessible and accurate analysis method for microplastics that have been unintentionally added to cream cosmetic products. An experiment was performed on three cleansing creams in rich and viscous formulations. A spiked sample was prepared by adding polyethylene (PE) microspheres to the cleansing creams. After removing cosmetic ingredients from the creams using chemical digestion, damage to the PE microspheres was identified using Fourier transform infrared (FT-IR) spectroscopy. Field emission scanning electron microscopy (FE-SEM) images were obtained before and after digestion and used to characterize the morphology of the PE microspheres. The highest digestion efficiency was obtained using a chemical digestion method consisting of heating and stirring a sample in a 10 wt% KOH solution at 55 °C and 300 rpm for 5 days and did not damage the PE microspheres. The Nile red (9-diethylamino-5H-benzo[α]phenoxazine-5-one) staining method was effective in identifying small microplastics (< 106 µm). The optimal staining conditions are 5 µg/ml Nile red in n-hexane for green wavelengths.

Evaluation of optimal conditions for anionic surfactant removal in wastewater.

This study was conducted to find the optimal conditions for removing anionic surfactants in wastewater using the coagulant-flocculant method. Optimal conditions must be found to minimize the amount of metal materials that can cause secondary contamination and to improve performance. Five parameters were selected to investigate their influence on surfactant removal. The ranges of the independent variables were 0.5-5% for coagulant concentration, 0.1-1% for flocculant concentration, and 20-650 mg/L for surfactant concentration; the coagulant type was FeCl3·6H2O or Ca(OH)2; and the pH ranged from 2 to 10. The experimental results were analyzed with Minitab 19.1 to find the optimal conditions to maximize the removal rate of surfactant. In this study, a total of 20 experiments were carried out using a half fractional factorial design (FFD) including two center points with a resolution of 5 and a pseudo-center point. The results demonstrated that coagulant concentration, flocculant concentration, and pH were significant independent variables with respect to surfactant removal. The fitted regression equation confirmed that the surfactant removal rate was maximized when the coagulant concentration was 5%, the flocculant concentration was 0.1%, and the pH was 10.

Functionalized cellulose to remove surfactants from cosmetic products in wastewater.

A flocculant composed of paper mulberry dicarboxylic cellulose (PM-DCC) made from using paper mulberry (Broussonetia kazinoki Siebold and Zucc.) has been developed to reduce the amount of inorganic coagulants needed to remove surfactants in wastewater. The characteristics of PM and soda pulp were determined according to the degree of polymerization, α-cellulose, lignin, free sugar, and extract contents. FTIR, XRD, the aldehyde content, the carboxyl content and coagulant-flocculation experiments were conducted to confirm the properties of PM-DCC and paper mulberry dialdehyde cellulose (PM-DAC). A dramatic removal efficiency (95.62 %) was revealed when 0.3 % PM-DCC was added into a linear alkylbenzene sulfonate (LAS) solution with 1% FeCl3·6H2O at pH 2. This means that PM-DCC contributes to both a lower amount of inorganic coagulant needed and a reduction of water pollution by an ecofriendly method.

Removal of Pb(II) ions from aqueous solutions using functionalized cryogels.

In this study, a poly(allylamine-co-methacrylamide-co-acrylic acid) (p(AA-co-MA-co-AAc)) cryogel containing amine and carboxyl groups was prepared and subsequently functionalized with thiourea using methyl isothiocyanate. The functionalized p(AA-co-MA-co-AAc) cryogel was then applied to the adsorption of lead (Pb) ions from aqueous solution, and the amount of Pb adsorption was measured. The functionalized p(AA-co-MA-co-AAc) cryogel was analyzed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), and its chemical structure, pore shape, pore distribution and specific surface area were confirmed. To determine the effect of the solution pH and initial concentration on Pb adsorption by the functionalized p(AA-co-MA-co-AAc) cryogel, Pb adsorption tests were performed. The functionalized p(AA-co-MA-co-AAc) cryogel exhibited the highest adsorption amount at pH 7 and 400 mg L-1. The Pb adsorption process was determined to occur through chemical adsorption because the experimental data were fit well by a pseudo-second-order model. In addition, the equilibrium isotherm data fit the Langmuir isotherm better than the Freundlich model, indicating that the functionalized p(AA-co-MA-co-AAc) cryogel surfaces were uniform and that a lead adsorbate monolayer formed at equilibrium.

Photocatalytic oxidation of gas-phase elemental mercury by nanotitanosilicate fibers.

Photocatalytic fibers were generated from the continuous evaporation of titanium tetraisopropoxide with tetraethyl orthosilicate through a flame burner. The morphology, the crystal form, and the components of the nanotitanosilicate fibers were analyzed by Raman spectroscopy, Field emission-scanning electron microscope, X-ray diffraction, and Brunauer-Emmett-Teller surface area analysis. The nanotitanosilicates prepared by three different carrier gases (air, N(2), and Ar) were tested for their photocatalytic ability to remove/oxidize gas-phase elemental mercury. Under UV black light, the Hg(0) capture efficiencies were 78%, 86%, and 85% for air, N(2), and Ar, respectively. For air, the value was close to 90%, even under household fluorescent light. The Hg(0) capture efficiency by nanotitanosilcate was measured under fluorescent light, UV black light, and sunlight.

A simultaneous stabilization and solidification of the top five most toxic heavy metals (Hg, Pb, As, Cr, and Cd).

A novel chemically bonded phosphate ceramic (CBPC) binder was developed for the simultaneous treatment of the top five most toxic heavy metals (Hg, Pb, As, Cr, and Cd). Various CBPC binders were synthesized and tested, and their toxicity characteristic leaching procedure (TCLP) values were obtained. A magnesium/calcium-potassium phosphate ceramic binder with FeCl2 (M/C-KP-FeCl2) simultaneously stabilized multiple heavy metals. The TCLP value of the final product for industrial waste (IW) treatment using the M/C-KP-FeCl2 technology was well below the Universal Treatment Standard (UTS). Additionally, the compressive strength of the final product was below the US Nuclear Regulatory Commission Standard.

Mercury recovery from mercury-containing wastes using a vacuum thermal desorption system.

Mercury (Hg)-containing waste from various industrial facilities is commonly treated by incineration or stabilization/solidification and retained in a landfill at a managed site. However, when highly concentrated Hg waste is treated using these methods, Hg is released into the atmosphere and soil environment. To eliminate these risks, Hg recovery technology using thermal treatment has been developed and commercialized to recover Hg from Hg-containing waste for safe disposal. Therefore, we developed Hg recovery equipment to treat Hg-containing waste under a vacuum of 6.67kPa (abs) at 400°C and recover the Hg. In addition, the dust generated from the waste was separated by controlling the temperature of the dust filtration unit to 230°C. Additionally, water and Hg vapors were condensed in a condensation unit. The Hg removal rate after waste treatment was 96.75%, and the Hg recovery rate as elemental Hg was 75.23%.

Structural effect of the in situ generated titania on its ability to oxidize and capture the gas-phase elemental mercury.

Structural effect of the in situ generated TiO(2) sorbent particle was examined for its ability to capture elemental mercury under UV irradiation in a simulated combustion flue gas. Titania particles were prepared by thermal gas-phase oxidation of Titanium (IV) isopropoxide (TTIP) using a high temperature electric furnace reactor. The structural characteristics of the in situ generated TiO(2) at various synthesis temperatures were investigated; size distribution and the geometric mean diameter were measured using a scanning mobility particle sizer, while fractal dimension and radius of gyration were evaluated from the transmission electron microscopy images. Results from the Hg(0) capture experiment show that with increasing titania synthesis temperature, the overall aggregate size increases and the morphology becomes more open-structured to gas-phase Hg(0) and UV light, resulting in the improved mercury removal capability.

Preparation of gold- and chlorine-impregnated bead-type activated carbon for a mercury sorbent trap.

This study aimed to develop a mercury (Hg) adsorption trap, which can be used to measure the concentration of elemental Hg in emissions from a Hg discharge facility, and evaluate its adsorption efficiency. The Hg spiking efficiency was compared by impregnating metallic and halogen materials that have high affinity for Hg into activated carbon (AC) to determine an accurate spiking method for Hg on AC. The Hg spiking efficiency was compared according to the type and content of the impregnated substances. AC impregnated with Cl and Au had a 15-20% higher Hg spiking efficiency compared to virgin AC. For Au impregnation at weight ratios of 0-20 wt% of adsorbent, spiking efficiencies of over 97% were observed under certain conditions. The Hg adsorption properties of the above adsorbent were determined experimentally, and the results were used to test the adsorption performance of Hg adsorption traps.

Application of a sorbent trap system to gas-phase elemental and oxidized mercury analysis.

A sorbent trap that utilizes activated carbon (AC) as the solid trapping medium is a new technology for measuring total mercury (Hg) emissions from combustion facilities. In this study, sorbent trap technology was further developed, improved and evaluated at the laboratory scale. AC was impregnated with 5% aqua regia to enhance its Hg adsorption capacity. Sorbent traps spiked with an Hg standard solution were found to be reproducibly prepared and highly stable. The effect of the Hg concentration on the spiking efficiency was further investigated. The adsorption of elemental and oxidized Hg by the sorbent trap was studied under various experimental conditions (temperature, flow rate and inlet Hg concentration). The Hg concentration of the flue gas effluent from the sorbent trap was measured. In addition, the concentration of Hg adsorbed on the AC was determined by digesting the used AC with an acid according to US EPA method 3052 and then analyzing it with cold vapor atomic absorption spectrometry. Furthermore, the gas-phase Hg emissions from a combustion source were measured using the sorbent trap according to US EPA method 30B. The results showed that the sorbent trap could be used for Hg concentrations between 10.0 and 40.0 µg m(-3) and flow rates between 0.5 and 1.0 lpm with adsorption efficiencies greater than 90%.

Controlled release of lidocaine hydrochloride from the surfactant-doped hybrid xerogels.

We investigate the controlled release of lidocaine hydrochloride from the doped silica-based xerogels. In the xerogel preparation, tetraethoxysilane (TEOS), methyltriethoxysilane (MTES), and propyltriethoxysilane (PTES) are used as precursors, and a nonionic surfactant Igepal CO 720 is used as a dopant. The experimental results suggest that the release of lidocaine hydrochloride can be easily controlled by partially substituting TEOS with the organosilanes, and/or by adding the dopant. Adding the organosilane precursors lowers the release of both the drug and the surfactant in the order of TEOS, MTES/TEOS, and PTES/TEOS xerogels. The release from the PTES/TEOS xerogels is much lower than that from the other xerogels. The release of lidocaine hydrochloride is obviously suppressed by the addition of Igepal CO 720, while the release of Igepal CO 720 is slightly promoted by the addition of the drug. The overall release process is found to be diffusion-controlled, and the release behaviors can be well explained by considering the effects of the textual properties of the xerogels and the interactions among the drug, the surfactant, and the xerogel matrices.

Enzymatic esterification of beta-methylglucoside with acrylic/methacrylic acid in organic solvents.

The enzymatic esterifications of beta-methylglucoside with acrylic acid/methacrylic acid were carried out using Novozym 435. t-Butanol indicating the highest conversion value was determined as an optimal solvent. The molar ratio (beta-methylglucoside:acids) of 1:15 was most favorable to the esterification. The enzyme concentration of 5% (w/v), and the temperature (50 degrees C for beta-methylglucoside:acrylic acid, 45 degrees C for beta-methylglucoside:methacrylic acid) resulted in the highest final conversion. Beta-methylglucoside of 60gl(-1) was found to be most effective in terms of short reaction time as well as product concentrations. Under these conditions, the maximum conversions for the esterification of beta-methylglucoside with acrylic acid and beta-methylglucoside with methacrylic acid were 59.3% after 12h and 71.3% after 72h, respectively. The structural analysis of the products was performed by FT-IR spectroscopy and (1)H NMR.

Chemoenzymatic synthesis of sugar-containing biocompatible hydrogels: crosslinked poly(beta-methylglucoside acrylate) and poly(beta-methylglucoside methacrylate).

Sugar-containing biocompatible hydrogels were synthesized chemoenzymatically by the following two steps: 1. lipase-catalyzed esterification of beta-methylglucoside with acrylic acid/methacrylic acid/vinyl acrylate/vinyl methacrylate in solvent as well as solvent-free process for the formation of sugar-containing monomers; and 2. polymerization process by free-radical polymerization with and without a crosslinker, ethylene glycol dimethacrylate (EGDMA). The solvent-free process resulted in an initial reaction rate approximately 1.5-2 times faster than that of the solvent process along with a complete consumption of beta-methylglucoside during the alcoholysis. The presence of pendant vinyl groups in beta-methylglucoside acrylate (MGAA) and beta-methylglucoside methacrylate (MGMAA) was confirmed by (1)H/(13)C NMR analysis, whereas the successful polymerization with the consumption of the vinyl groups was confirmed by Fourier transform infrared spectroscopy and (13)C NMR spectra. The surfaces of both poly(MGAA) and poly(MGMAA) were analyzed using scanning electron microscopy. The increased contents of EGDMA resulted in a higher tensile strength as well as a reduced swelling ratio of poly(MGAA) and poly(MGMAA). The swelling exponents were within the range of 0.53 and 0.98. In vitro cytotoxicity tests by MTT assay exhibited >90% cell viability in the poly(MGAA) and poly(MGMAA) without EGDMA, whereas a significantly decreased cell viability was observed for those with EGDMA.

Mercury removal from incineration flue gas by organic and inorganic adsorbents.

Experiments were performed to investigate various adsorbents for their mercury removal capabilities from incineration flue gases. Four different materials were tested; Zeolite, Bentonite, activated carbon (AC), and wood char. Real incineration off-gas and in-lab simulated combustion flue gases (N2 + Hg) were used. Three cylindrical-shaped sorbent columns with 5 cm in diameter and 20 cm in length were used. The gas flow rate was fixed at 660 l/h at all times. Concentrations of NO, CO, O2, CO2, SO2, H2O, HCl, and mercury were continuously monitored. Mercury removal efficiencies of natural Zeolite and Bentonite were found to be much lower than those of the referenced AC. Amount of Hg removed were 9.2 and 7.4 microg/g of Zeolite and Bentonite, respectively. Removal efficiencies of each layer consisted of inorganic adsorbents were no higher than 7%. No significant improvement was observed with sulfur impregnation onto the inorganic adsorbents. Organic adsorbents (wood char and AC) showed much higher mercury removal efficiencies than those of inorganic ones (Zeolite and Bentonite). Mercury removal efficiency of wood char reached over 95% in the first layer, showing almost same effectiveness as AC which currently may be the most effective adsorbents for mercury. Amount of mercury captured by wood char was approximately 0.6 mg/g of wood char, close to the amount captured by AC tested in this study. Hence, wood char, made from the waste woods through a gasification process, should be considered as a possible alternative to relatively expensive AC.

Hg reactions in the presence of chlorine species: homogeneous gas phase and heterogeneous gas-solid phase.

The kinetics of Hg chlorination (with HCl) was studied using a flow reactor system with an online Hg analyzer, and speciation sampling using a set of impingers. Kinetic parameters, such as reaction order (alpha), overall rate constant (k'), and activation energy (Ea), were estimated based on the simple overall reaction pathway. The reaction order with respect to C(Hg), k', and Ea were found to be 1.55, 5.07 x 10(-2) exp(-1939.68/T) [(microg/m3)(-055)(s)(-1)]. and 16.13 [kJ/ mol], respectively. The effect of chlorine species (HCl, CH2Cl2) on the in situ Hg capture method previously developed (28) was also investigated. The efficiency of capture of Hg by this in situ method was higher than 98% in the presence of chlorine species. Furthermore, under certain conditions, the presence of chlorine enhanced the removal of elemental Hg by additional gas-phase oxidation.

A mechanistic model for mercury capture with in situ-generated titania particles: role of water vapor.

A mechanistic model to predict the capture of gas-phase mercury (Hg) species using in situ-generated titania nanosize particles activated by UV irradiation is developed. The model is an extension of a recently reported model for photochemical reactions by Almquist and Biswas that accounts for the rates of electron-hole pair generation, the adsorption of the compound to be oxidized, and the adsorption of water vapor. The role of water vapor in the removal efficiency of Hg was investigated to evaluate the rates of Hg oxidation at different water vapor concentrations. As the water vapor concentration is increased, more hydroxy radical species are generated on the surface of the titania particle, increasing the number of active sites for the photooxidation and capture of Hg. At very high water vapor concentrations, competitive adsorption is expected to be important and reduce the number of sites available for photooxidation of Hg. The predictions of the developed phenomenological model agreed well with the measured Hg oxidation rates in this study and with the data on oxidation of organic compounds reported in the literature.