Sorption of pentachlorophenol on surficial sediments: the roles of metal oxides and organic materials with co-existed copper present

The sorption characteristics of pentachlorophenol (PCP) in the surficial sediments were investigated using a selective extraction procedure. The results show that the Gamma(max) of PCP sorption decreased from 1.60mumolg(-1) to 0.69mumolg(-1) by approximately 60% after selective removal of organic materials from the sediments. The sorption of PCP in the sediments after selective removal of Mn oxides increased nearly up to 600% (from 1.60mumolg(-1) to 11.11mumolg(-1)) and, to a less degree, the PCP sorption in the sediments after simultaneous removal of Fe/Mn oxides (Gamma(max)=3.53mumolg(-1)). The analysis of the data using an additional model indicates that the contribution of Mn oxides to PCP sorption was negative, and Fe oxides and organic materials both have greater potential for sorption of PCP with less contribution from residues including Mn and Fe oxides in the residual fractions determined by a sequential extraction procedure and clay and silicate minerals. The differences in the decreased degrees of PCP sorption with increasing of Cu suggest that competition between Cu and PCP for sorption sites mainly takes place on Fe oxides.     

A comparative study on metal sorption by brown seaweed

This study compared the sorption of Ag, Cd, Co, Cd, Mn, Ni, Pb and Zn by a Ca-treated Sargassum biomass at pH 5.0, under low and high ionic strength (IS) conditions. The sorption isotherms of As [As(V)] and Cr [Cr(III) and Cr(VI)] were also determined at low IS. The isotherm data for the eight cationic metals and Cr(III) were well fitted by Langmuir equations. Generally, the maximum metal uptake (Umax) followed: Cr(III) > Pb approximately Cu > Ag approximately Zn approximately Cd > Ni approximately Mn approximately Co > Cr(VI) > As(V) at low IS and Pb > Cu > Co > Mn approximately Cd > Zn approximately Ag > Ni at high IS. As(V) did not bind to the seaweed at pH 5.0. The results indicated that sorption of Pb was not affected by the increasing IS, though the percentage of free Pb ions in the water was greatly reduced as predicted by the speciation model. High IS lowered Umax by 10-36% (except Co and Pb), and lowered the affinity constant of the metal by 33-91% for all cationic metals, as compared to low IS. Moreover, the removal efficiency of the cationic metals and Cr decreased exponentially with initial metal concentrations and was lower at high IS. Ion-exchange was the mechanism responsible for the cationic metal sorption onto the seaweed, and Na ion interfered with the cationic metal binding through electrostatic interaction. In conclusion, this study showed the differential binding capacity of the Sargassm biomass for different metals and oxidation states and the differential effects of IS. According to the present results, Sargassum may be considered a good biosorbent for cationic metals (especially Pb) in both low and high-salt containing wastewater.     

Mobility of heavy metals from polluted sediments of a semi-enclosed basin: in situ benthic chamber experiments in Taranto’s Mar Piccolo (Ionian Sea,Southern Italy)

In situ benthic flux experiments were conducted at two stations in the Mar Piccolo of Taranto (Italy), one of the most industrialised and contaminated coastal areas of the Mediterranean. Sediments of the two stations are notably different in their trace metal content, with a station closer to a Navy harbour showing higher mean concentrations of almost all investigated metals (Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, V and Zn). Conversely, both stations are characterised by significant Hg contamination, compared to the local baseline. Results of a sequential extraction scheme on surface sediments suggest a relatively scarce mobility of the examined metals (Zn > Ni > Cr > As > Cu > Pb). A Hg-specific extraction procedure showed that most of the element (93.1 %) occurs in a fraction comprising Hg bound to Fe/Mn oxi-hydroxides. Reduction of these oxides may affect Hg remobilisation and redistribution. Porewater profiles of dissolved trace metals were quite similar in the two sites, although significant differences could be observed for Al, Cu, Fe and Hg. The highest diffusive fluxes were observed for As, Fe and Mn. Mobility rates of several trace elements (Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, V and Zn) were directly measured at the sediment–water interface. Results from benthic in situ incubation experiments showed increasing dissolved metal concentrations with time, resulting in higher fluxes for Cu, Fe, Hg, V and Zn in the most contaminated site. Conversely, fluxes of Mn, Ni and Pb were comparable between the two stations. The estimated flux of Hg (97 μg m^?2 day^?1) was the highest observed among similar experiments conducted in other highly contaminated Mediterranean coastal environments. Benthic fluxes could be partially explained by considering rates of organic matter remineralisation, dissolution of Fe/Mn oxy-hydroxides and metal speciation in sediments. Seasonal and spatial variation of biogeochemical parameters can influence metal remobilisation in the Mar Piccolo area. In particular, metals could be promptly remobilised as a consequence of oxygen depletion, posing a serious concern for the widespread fishing and mussel farming activities in the area.     

Distribution and Fractionation of Phosphorus,Cadmium, Nickel,and Lead in Calcareous Soils Amended with Composts

Abstract

Composts improve organic carbon content and nutrients of calcareous soils but the accumulation and distribution of phosphorus and heavy metals among various fractions in soil may vary under the south Florida conditions. The accumulation of P, Cd, Ni, and Pb with depth and the distribution of water soluble, exchangeable, carbonate, Fe–Mn oxides, organic and residual forms of each element were investigated in soils amended with municipal solid waste (MSW) compost, co-compost and biosolids compost and inorganic fertilizer (as control). Total concentrations of P, Cd, Ni, and Pb were higher in the 0–22 cm soil layers and decreased considerably in the rock layers. These elements were in the decreasing order of P ? Pb > Ni > Cd. Amounts of water soluble and exchangeable forms of P, Cd, Ni and Pb were negligible at 0–22 cm soil depths except for Cd in the 10–22 cm depth. Amending calcareous soil with either organic or inorganic amendments rendered phosphorus, nickle and lead in the residual form followed by Fe–Mn oxides form in the 0–10 and 10–22 cm soil layers. Cadmium was predominantly in the Fe–Mn oxides fraction followed by the residual and carbonate forms in both soil layers. A significant positive correlation was found between various organic carbon fractions and organic forms of P, Cd and Pb in the surface soil layer. Soil amended with MSW compost had higher concentration of Cd in the organic fraction whereas, co-compost and MSW compost amended soil had higher concentrations of organic Ni fraction in the 0–10 cm soil layer.     

Cadmium speciation and accumulation in periphyton in a small stream with dynamic concentration variations

Accumulation of cadmium in periphyton was investigated under field conditions while Cd concentration and speciation were dynamically varying in a small stream during rain events. Speciation in water was determined in situ by diffusion gradient in thin-films (DGT) and by modeling of complexation with fulvic acids. During the rain events, dissolved Cd concentrations increased from 0.17 nM to 0.27-0.36 nM, and 70-97% were DGT-labile. Cd content in periphyton closely followed Cd concentrations in water, despite higher concentrations of Zn and Mn, and may be controlled by either free or DGT-labile Cd concentrations. Decrease of Cd content in periphyton after the rain events was slower than the decrease of Cd concentration in water. Concentrations of Zn, Mn, Cu, Pb and Fe in periphyton also followed the dynamic variations of metal concentrations in water. Repeated exposure of periphyton to elevated dissolved Cd may lead to Cd accumulation.     

Evaluation of heavy metal concentrations of edible wild-grown mushrooms from China

ABSTRACT

The heavy metal contents (Co, Cu, Fe, Mn, Ni, and Zn) of eight species of wild edible mushrooms from China were determined. The analyses were performed using inductively coupled plasma atomic emission spectrophotometry after microwave digestion. The contents of Co, Cu, Fe, Mn, Ni, and Zn in caps of mushroom samples were 0.7–7.2, 16.2–70.4, 371–1315, 12.5–29.8, 7.1–58.5, and 77.8–187.4 mg kg^?1 dry matter (dm), respectively, while considerable differences were found to be 1.8–25.9, 9.8–36.3, 288–6762, 13.3–103.9, 5.9–78.7, and 38.7–118 mg kg^?1 dm for stipes. The results indicated that higher levels of Co, Fe, and Ni were found in the mushrooms samples analyzed. Zinc and manganese levels were similar to previous reports, whereas Cu was lower than literature values. Correlation analysis suggested that significant correlations were found between the minerals determined and the greatest amount of contamination is associated with Co, Mn, Ni, and Fe. The results of this study indicate that heavy metal contents in mushroom species are mainly related to the mineral resources of sampling sites.     

Estimation of metal uptake efficiencies from precipitation in mosses in Lithuania

The main sources contributing to heavy metal content in mosses in Lithuania were examined by a comparison of heavy metal concentrations in moss and corresponding deposition levels calculated from bulk deposition analysis. Bulk deposition was collected in open areas as well as under the canopy of trees. Uptake efficiencies in moss were calculated for Cd, Cr, Cu, Fe, Mn, Ni, V and Zn. All elements in moss except Pb and Cd appeared to be more or less influenced by sources other than air pollution. The general order of this influence on the heavy metal content in moss was observed as follows: Ni < V < Cr < Zn < Fe < Mn. The contents of Mn and Zn in moss were greatly influenced by leaching from the canopy while Pb was the only element which showed a net metal retention by the canopy. Concentrations of Fe and Cr in moss were dominating due to contribution from soil dust.     

Relationship between heavy metals concentrations in egret species,their environment and food chain differences from two Headworks of Pakistan

Concentration of ten metals (Cd, Cr, Co, Cu, Fe, Li, Mn, Ni, Pb and Zn) were analyzed in the egg contents, prey and soil samples of little egret (Egretta garzetta) and cattle egret (Bubulcus ibis) from two Headworks to determine habitat and species-specific differences; to assess the importance of prey and habitat contamination as an exposure source for heavy metals. Concentration of Cu, Mn, Cr and Pb in egg contents, Fe, Co, Cu, Mn, Zn in prey and Fe, Co, Cu, Ni, Li in surface soils were significantly different (P < 0.05). Mean metal concentrations of Cr, Pb and Cd were relatively higher in little egret whereas Cu and Mn were higher in the egg contents of cattle egret. The mean concentrations of Cu, Mn and Zn were higher in prey samples of cattle egrets and Cr, Cd and Pb in prey samples of little egrets. In soil samples collected from little egret heronries metal concentrations were higher except Cu and Ni. Correlation Analysis and Hierarchical Agglomerative Cluster Analysis (HACA) identified relatively similar associations of metals and their source identification. Metals such as Fe, Cu, Mn, and Li were related with geochemical origin from parent rock material as well as anthropogenic input whereas Cr, Cd, Pb, Ni, Co and Zn were associated mostly with anthropogenic activities. The study suggested that eggs are useful bio-monitor of local heavy metal contamination.     

Distribution and variability of redox zones controlling spatial variability of arsenic in the Mississippi River Valley alluvial aquifer, southeastern Arkansas

Twenty one of 118 irrigation water wells in the shallow (25-30 m thick) Mississippi River Valley alluvial aquifer in the Bayou Bartholomew watershed, southeastern Arkansas had arsenic (As) concentrations (<0.5 to 77 microg/L) exceeding 10 microg/L. Sediment and groundwater samples were collected and analyzed from the sites of the highest, median, and lowest concentrations of As in groundwater in the alluvial aquifers located at Jefferson County, Arkansas. A traditional five-step sequential extraction was performed to differentiate the exchangeable, carbonate, amorphous Fe and Mn oxide, organic, and hot HNO(3)-leachable fraction of As and other compounds in sediments. The Chao reagent (0.25 M hydroxylamine hydrochloride in 0.25 M HCl) removes amorphous Fe and Mn oxides and oxyhydroxides (present as coatings on grains and amorphous minerals) by reductive dissolution and is a measure of reducible Fe and Mn in sediments. The hot HNO(3) extraction removes mostly crystalline metal oxides and all other labile forms of As. Significant total As (20%) is complexed with amorphous Fe and Mn oxides in sediments. Arsenic abundance is not significant in carbonates or organic matter. Significant (40-70 microg/kg) exchangeable As is only present at shallow depth (0-1 m below ground surface). Arsenic is positively correlated to Fe extracted by Chao reagent (r=0.83) and hot HNO(3) (r=0.85). Arsenic extracted by Chao reagent decreases significantly with depth as compared to As extracted by hot HNO(3). Fe (II)/Fe (the ratio of Fe concentration in the extracts of Chao reagent and hot HNO(3)) is positively correlated (r=0.76) to As extracted from Chao reagent. Although Fe (II)/Fe increases with depth, the relative abundance of reducible Fe decreases noticeably with depth. The amount of reducible Fe, as well as As complexed to amorphous Fe and Mn oxides and oxyhydroxides decreases with depth. Possible explanations for the decrease in reducible Fe and its complexed As with depth include historic flushing of As and Fe from hydrous ferric oxides (HFO) by microbially-mediated reductive dissolution and aging of HFO to crystalline phases. Hydrogeochemical data suggests that the groundwater in the area falls in the mildly reducing (suboxic) to relatively highly reducing (anoxic) zone, and points to reductive dissolution of HFO as the dominant As release mechanism. Spatial variability of gypsum solubility and simultaneous SO(4)(2-) reduction with co-precipitation of As and sulfide is an important limiting process controlling the concentration of As in groundwater in the area.     

Residual metal concentrations in soils and leaf accumulations in tobacco a decade following farmland application of municipal sludge

The objectives of this investigation were to examine the long-term residual effects of metal loading through sewage sludge applications on the total vs. diethylene triamine pentacetic acid (DTPA) extractable metal concentrations in soil and leaf accumulations in tobacco. Maryland tobacco (Nicotiana tabacum L.), cv. 'MD 609', was grown in 1983 and 1984 at two sites in Maryland that had been amended in 1972 with dewatered, digested sewage sludge from washington, DC, at rates equal to 0, 56, 112 and 224 mg ha(-1). The metal concentrations in the sludge, in mg kg(-1) dry weight, were: 1300 Zn, 570 Cu, 280 Pb, 45 Ni and 13 Cd. Soil samples collected from the surface horizon and composite leaf samples of cured tobacco were analyzed for total Zn, Cu, Mn, Fe, Pb, Ni and Cd concentrations. The soil samples were also examined for soil pH and DTPA extractable metals. Equations were generated using polynomic and stepwise regression analyses which described the relationships between total vs. DTPA extractable soil metals, and between DTPA soil and soil pH vs. plant metal concentrations, respectively. Significant increases were observed for both total and DTPA extractable metal concentrations for all metals, with all but total Mn and Ni being significant for linear and quadratic effects regarding sludge rates. However, linear relationships were found between DTPA extractable vs. total soil concentrations for all elements except Pb and Ni which were quadratic. Significant increases in plant Zn, Cu, Mn, Ni and Cd and decreases in Fe were observed with increased sludge rates. Plant Pb levels were unaffected by sludge applied Pb. Linear relationships were observed between plant Zn and Cd and DTPA soil metal levels: however, Mn and Cu levels were described by quadratic and cubic relationship, respectively. Relationships between plant Fe and Pb and DTPA extractable concentrations were nonsignificant. Additional safeguards to protect crop contamination from heavy metals such as Cd were discussed.     

具有K2NiF4型结构的稀土复合氧化物对有机胺的催化降解作用研究

采用柠檬酸络合分解法合成了四方晶点、Ｋ２ＮｉＦ４型结构的稀土复合氧人ＬａＳｒＭＯ４（Ｍ＝Ｍｎ，Ｆｅ，Ｃｏ，Ｎｉ）。实验结果，该类氧化物催化剂对恶臭和有毒的有机胺类化合物具有较好的催化降解作用，有机胺的氧降解可达１００％，而氮氧化物的产生率低于１０％，其含量可大大低于排放标准。     

Heavy metal removal by activated sludge: influence of Nocardia amarae.

The goal of this research was to examine the metal binding capacity of Nocardia amarae cells and to assess the influence of Nocardia cells on the overall metal binding capacity of activated sludge. Metal sorption capacities of the pure Nocardia cells and activated sludge biomass containing various levels of added Nocardia pure cultures were determined by a series of batch experiments. Batch sorption isotherms for nickel (Ni), copper (Cu), and cadmium (Cd) showed that the pure culture of N. amarae exhibited significantly higher metal sorption capacity than the activated sludge biomass obtained from Wilmington Wastewater Treatment Plant (Wilmington, DE). Surface area of biomass estimated by a dye technique showed that pure N. amarae cells growing at stationary phase have substantially more specific surface area than that of activated sludge from Wilmington Treatment Plant. A two-fold difference in specific surface area indicated that the higher metal sorption capacity of Nocardia cells may be due to the higher specific surface area. The metal sorption capacity of activated sludge increased proportionally with the amount of Nocardia cells present in the mixed liquor. This increase was attributed to the greater specific surface area of the mixed liquor samples containing greater amounts of Nocardia cells.     

Airborne heavy metal pollution and its effects on foliar elemental composition of Empetrum hermaphroditum and Vaccinium myrtillus in Sør-Varanger, northern Norway

Uptake of Al, Cu, Fe, Mn, Ni, Ca, K, Mg, P, and S in Empetrum nigrum L. ssp. hermaphroditum Hagerup and Vaccinium myrtillus L. from Ni, Cu and SO2 contaminated sites in S?r-Varanger, northern Norway, were investigated. The primary objective was to study the effect of airborne heavy metal pollution on foliar element composition of these two dwarf shrubs. Ni distribution and availability in soils clearly indicate atmospheric deposition of Ni particulates in S?r-Varanger. Foliar Ni concentrations in E. hermaphroditum and V. myrtillus increased in relation to plant available Ni in corresponding soils. Leaves of E. hermaphroditum generally contained higher concentrations of Ni than leaves of V. myrtillus. Emissions influenced some features of leaf elemental composition of the two species in very different ways. In leaves of V. myrtillus, S increased in proportion to Ni and Cu, while levels of Mn decreased. In leaves of E. hermaphroditum, Fe increased in proportion to Ni and Cu, while levels of Ca decreased.     

Grit ingestion as a source of metal exposure in the spruce grouse, Dendragapus canadensis

The objective of this study was to determine if ingestion of grit was a source of metal exposure to the spruce grouse, Dendragapus canadensis. A secondary objective was to assess whether grit could provide a supplemental source of essential minerals to their diet. Ca, P, Mg, S, Zn, Cu, Ni, Co, Cr, Fe, Mn, Al, Pb and Cd of liver (adult, yearling, chicks), crop and gizzard contents (adults) were determined for grouse collected from a relatively pristine boreal forest region of north-central Ontario, Canada. With the exception of Cd liver, concentrations were independent of age [one-way analysis of variance (ANOVA); p>0.004). Zn liver concentrations tended to be greater in adults than yearlings and chicks (one-way ANOVA; p=0.02). Liver concentrations of Cd increased with age (r=0.99; p<0.001). The contribution of crop items to total gizzard elemental content was element specific; crop contents contributed 90-100% of Mn and Zn, 70% for P and Ca, 60% for Pb, 50% for S, and 0-25% for Cu, Mg, Ni, Al, Fe, Co, Cr and Cd to the total elemental concentration of gizzard contents (crop plus grit). Incorporation of grit by grouse could, therefore, constitute an important source of essential macro-(Ca, P, Mg, S) and trace elements (Cu, Fe) but not for Mn or Zn. However, in addition to providing nutrients to the bird, ingestion of grit results in exposure to toxic trace metals such as Cd which in turn is accumulating in the liver. Research directed at determining grit turnover time, and hence metal exposure rates, in bird species which ingest grit to aid in food digestion is required. The toxicological significance of Cd exposure to grit-ingesting birds needs attention.     

Effect of pre-treatment and supporting media on Ni(II), Cu(II), Al(III) and Fe(III) sorption by plant root material

In this work Paspalum notatum root material was used to elucidate the influence of acid leaching pre-treatment and of sorption medium on metal adsorption. Ground P. notatum root was leached with 0.14M HNO(3). Leached root material (LRM) and non-leached root material (NLRM) were employed to flow sorption of Ni(II), Cu(II), Al(III) and Fe(III) in 0.5M CH(3)COONH(4) medium at pH 6.5. For LRM the sorption was also studied in 0.5M KNO(3) medium. The acid pre-treatment increased the sorption capacity (SC) for all ions studied. For the KNO(3) medium, Cu(II) and Fe(III) sorption was higher than in CH(3)COONH(4) and the type of the Ni(II) isotherm's model changed. The Freundlich model was the most representative isotherm model to describe metallic ions sorption. The (1)H NMR spectra showed differences between LRM and NLRM and the acid-basic potentiometric titration elucidated that acid-leaching procedure affected the root material sorption sites once only two predominant sorption sites were found for LRM (phenolic and amine, both able cations sorption) and five sorption sites (two carboxylic, amine and two phenolic) were founded for NLRM.     

Changes in elemental uptake and arbuscular mycorrhizal colonisation during the life cycle of Thlaspi praecox Wulfen

Elemental uptake and arbuscular mycorrhizal (AM) colonisation were studied during the life cycle of field collected Cd/Zn hyperaccumulating Thlaspi praecox (Brassicaceae). Plant biomass and tissue concentrations of Cd, Pb, Zn, Fe and Ni were found to vary during development, while no variation in P, K, Ca, Mn and Cu tissue concentrations were observed. The lowest Cd bioaccumulation in rosette leaves (BAF(RL)) observed during seeding was partially attributed to lower translocation from roots to rosette leaves and partially to high translocation to stalks, indicating a high Cd mobility to reproductive tissues, in line with our previous studies. The highest intensity of AM colonisation (M%) was observed in the flowering phase and was accompanied by increased root Cd, Zn, Pb and Fe contents. In addition, a positive correlation between AM colonisation and Fe contents in rosette leaves was found. The results indicate developmental dependence of AM formation, accompanied by selective changes in nutrient acquisition in T. praecox that are related to increased plant needs, and the protective role of AM colonisation on metal polluted sites during the reproductive period.     

A comparison of Cu, Pb, As, Cd, Zn, Fe, Ni and Mn determined by acid extraction/ICP-OES and ex situ field portable X-ray fluorescence analyses

Total concentrations of Cu, Pb, As, Cd, Zn, Fe, Ni and Mn were determined for 81 soil samples using two types of field portable X-ray fluorescence (FPXRF) system; dual isotope and X-ray tube. FPXRF metal concentrations were statistically compared with analytical results from aqua regia extractions followed by Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) analysis. The ability of each FPXRF instrument to produce analytical results comparable to the reference method was assessed by linear regression. A high degree of linearity was found for Fe and Pb with the X-ray tube instrument and for Fe, Cu, Pb, Zn, Cd and Mn with the dual source instrument. FPXRF analyser performance improved with increased analysis time for Cu, Mn and Pb, whilst Fe, Zn, Cd, Ni and As showed no significant improvement. Particle size did not influence FPXRF analyser performance. Both the dual isotope and the X-ray tube FPXRF instruments are effective tools for rapid, quantitative assessment of soil metal contamination and for monitoring the efficacy of remediation strategies.     

Heavy metal monitoring of marine algae from the Turkish Coast of the Black Sea, 1998-2000

Concentrations of Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn were determined in macroalgae samples collected from the Turkish Coast of the Black Sea. Certain algae species were chosen among the green, brown and red algae species at Sile and Sinop sampling stations from 1998 to 2000. In general, as regards the influence of the collection sites on the whole metal accumulation, Sinop is considered to be more polluted than Sile. The concentrations of the heavy metals in Cystoseira barbata algae are compared with previous studies in the same stations. The results showed that all metal levels have gradually decreased during past years. At the same time, Cd, Co, Cr, Cu, Fe, Ni and Pb levels in the present study are lower than in Bosphorus and Marmara Sea algae. However, Mn and Zn concentrations are higher than Bosphorus but lower than at Marmara. According to these findings the heavy metal pollution decreased in Turkish Coast of the Black Sea during the years investigated.     

Biogenic Mn oxides for effective adsorption of Cd from aquatic environment

Biogenic Mn oxides exert important controls on trace metal cycling in aquatic and soil environments. A Mn-oxidizing bacterium Bacillus sp. WH4 was isolated from Fe–Mn nodules of an agrudalf in central China. The biogenic Mn oxides formed by mediation of this Mn oxidizing microorganism were identified as short-ranged and nano-sized Mn oxides. Cd adsorption isotherms, pH effect on adsorption and kinetics were investigated in comparison with an abiotic Mn oxide todorokite. Maximum adsorption of Cd to the biogenic Mn oxides and todorokite was 2.04 and 0.69 mmol g^?1 sorbent, respectively. Thus, the biogenic Mn oxides were more effective Cd adsorbents than the abiotic Mn oxide in the aquatic environment. The findings could improve our knowledge of biogenic Mn oxides formation in the environment and their important roles in the biogeochemical cycles of heavy metals.     

Removal of trichloroethylene from water by cellulose acetate supported bimetallic Ni/Fe nanoparticles

In this study, cellulose acetate (CA) supported Ni/Fe nanoparticles were prepared and the ability of these nanoparticles to remove trichloroethylene (TCE) from water was studied. The effects of TCE reduction by the nanoparticles and sorption by the CA support were accounted for separately in the model. CA supported post-coated Ni/Fe nanoparticles were used to investigate the effect of metal particle composition on the observed reduction rate constant. The results show that the metal mass normalized observed reduction rate constant was proportional to the Ni content in the post-coated Ni/Fe nanoparticles in the range of 0-14.3 wt.%. This constant reached a maximum between 14.3 and 21.4 wt.% and decreased with further increase in Ni content. CA supported co-reduced Ni/Fe bimetallic nanoparticles gave poorer performance compared to CA supported post-coated Ni/Fe bimetallic nanoparticles at the same Ni content in Ni/Fe nanoparticles.