Addition Of Ferric Chloride Research Articles

Bioavailability of Iron-fortified Whey Protein Concentrate in Iron-deficient Rats

An iron-fortified whey protein concentrate (Fe-WPC) was prepared by addition of ferric chloride to concentrated whey. A large part of the iron in the Fe-WPC existed as complexes with proteins such as β-lactoglobulin. The bioavailability of iron from Fe-WPC was evaluated using iron-deficient rats, in comparison with heme iron. Rats were separated into a control group and an iron-deficiency group. Rats in the control group were given the standard diet containing ferrous sulfate as the source of iron throughout the experimental feeding period. Rats in the iron-deficiency group were made anemic by feeding on an Fe-deficient diet without any added iron for 3 wk. After the iron-deficiency period, the iron-deficiency group was separated into an Fe-WPC group and a heme iron group fed Fe-WPC and hemin as the sole source of iron, respectively. The hemoglobin content, iron content in liver, hemoglobin regeneration efficiency (HRE) and apparent iron absorption rate were examined when iron-deficient rats were fed either Fe-WPC or hemin as the sole source of iron for 20 d. Hemoglobin content was significantly higher in the rats fed the Fe-WPC diet than in rats fed the hemin diet. HRE in rats fed the Fe-WPC diet was significantly higher than in rats fed the hemin diet. The apparent iron absorption rate in rats fed the Fe-WPC diet tended to be higher than in rats fed the hemin diet (p = 0.054). The solubility of iron in the small intestine of rats at 2.5 h after ingestion of the Fe-WPC diet was approximately twice that of rats fed the hemin diet. These results indicated that the iron bioavailability of Fe-WPC was higher than that of hemin, which seemed due, in part, to the different iron solubility in the intestine.

Coagulation / flocculation process in the removal of trace metals present in industrial wastewater

Attempts were made in this study to examine the effectiveness of polymer addition to coagulation process during treatment of a beverage industrial wastewater to remove some of its trace metals content such as lead, cadmium, total iron, total chromium, nickel and zinc. Experiments were conducted using the standard Jar test procedure to determine the performance of both ferric chloride and organic polymer (a non-ionic polyacrylamide) individually and ferric chloride-polymer combination. The dosages used for ferric chloride ranged from 0 to 500mg/l, whereas polymer dosages varied between 0 and 100mg/l. The (optimal) removal efficiency for total chromium in the wastewater was obtained at 300mg /l for ferric chloride and 65mg/l for polymer. Whereas for zinc and total iron, the optimal removal efficiencies were obtained at 500mg/l for ferric chloride and 65mg/l for polymer. Addition of ferric chloride resulted in significant removal of the metals reaching up to 91%, 72% and 54% of total chromium, zinc and total iron respectively while addition of polymer achieved 95%, 87% and 88% of total chromium, zinc and total iron respectively. Ferric chloride produced more voluminous and more compacted sludge than polymer. Combinations of ferric chloride and polymer at different ratio achieved better removal efficiencies of the metals in the range 84-97% for total chromium, 69-90% for zinc and 69-92% for total iron, also less sludge was produced. Lead, cadmium and nickel were not detected in the raw wastewater. Journal of Applied Sciences and Environmental Management Vol. 10(3) 2006: 159-162

Disruption of N -Αcyl Homoserine Lactone-Mediated Cell Signaling and Iron Acquisition in Epiphytic Bacteria by Leaf Surface Compounds

Since N-acyl homoserine lactones (AHLs) are key mediators of cell density-dependent regulation of traits involved in virulence and epiphytic fitness in gram-negative bacteria such as Pseudomonas syringae, a variety of plant species were examined to determine their production of leaf surface compounds that could interact with these signaling systems. Leaf washings of 17 of 52 plant species tested stimulated or inhibited AHL-dependent traits in at least one of the bacterial reporter strains used. The active compounds from most plants could be distinguished from known AHLs due to different patterns of mobility during C8 and C18 reverse-phase thin-layer chromatography (TLC) and normal-phase TLC compared to the patterns for authentic bacterial AHLs. All plant extracts were also tested to determine their abilities to sequester iron and trigger bacterial siderophore synthesis on a medium containing abundant iron. Leaf washings from 16 of the 52 plant species, as well as tannic acid solutions, stimulated pyoverdine synthesis in P. syringae in a high-iron medium. These preparations also inhibited the growth of a P. syringae mutant unable to produce pyoverdine siderophores but not the growth of the wild-type bacterium. The stimulation of siderophore production and the growth inhibition by plant extracts and purified tannins were both reversed by addition of ferric chloride to culture media, indicating that iron was made unavailable by the compounds released onto the leaf surface.

Batch kinetics and thermodynamics of chromium ions removal from waste solutions using synthetic adsorbents

Mg(OH) 2 was identified as a component in the magnesia cement being adsorbent for Cr(VI). Modified magnesia cement was prepared by the addition of ferric chloride and humic acid. The equilibrium adsorption of Cr(VI) on magnesia cement adsorbents (MF5-1) and (MF5-2) was investigated as a function of contact time, adsorbent weight, solute concentration and temperature. Tests of different isotherms have shown that the adsorption data fit the Langmiur and Freundlich isotherms at 25 ± 1 °C. The nature of the diffusion process responsible for adsorption of Cr(VI) on (MF5-1) and (MF5-2) adsorbents was discussed. The kinetics and mechanism of diffusion of Cr(VI) into (MF5-1) and (MF5-2) adsorbents from aqueous solution have been studied as a function of Cr(VI) concentrations and reaction temperatures. The adsorption of Cr(VI) on the MF5-1 and MF5-2 adsorbents follows first-order reversible kinetics. The forward and backward constants, k 1 and k 2 have been calculated at different temperatures between 10 and 50 °C. The heat of activation of the adsorption, Δ H * and Δ S * were calculated for Cr(VI) at 25 °C. The values of Δ H * were found 18.1 and 10.7 kJ mol −1 for MF5-1 and MF5-2, respectively, while entropy change, Δ S *, were found −106.8 and −118.6 J mol −1 K −1 for MF5-1 and MF5-2, respectively. The study showed that pore diffusion is the rate-determining step in the adsorption of Cr(VI) ions for MF5-1 and MF5-2. MF5-2 was found more efficient for Cr(VI) adsorption than MF5-1. Also Cr(VI) can be adsorbed on MF5-2, whereas Cr(III) cannot. So, the competitive adsorption of multi-metals onto the MF5-2 adsorbent was studied. The studies showed that this adsorbent can be used as an efficient adsorbent material for the removal of Cr(VI) from water and nuclear power plant coolant water.

Grape Marc Compost Tea Suppressiveness to Plant Pathogenic Fungi: Role of Siderophores

It is important to know about the mechanisms that suppress plant diseases when compost from vegetable residues and/or their liquid extracts (compost tea) are used in order to improve the efficiency of this suppressing effect on pathogens. In this study, we assessed the presence of siderophores in various grape marc aerated compost teas (ACT) and their suppressing effect on nine pathogens: Rhizoctonia solani, Fusarium oxysporum f. sp. radicis-lycopersici, Fusarium oxysporum f. sp. lycopersici race 0, Fusarium oxysporum f. sp. lycopersici race 1, Fusarium oxysporum f. sp. radicis-cucumerinum, Verticillium dahliae, Pythium aphanidermatum, Phytophthora parasitica and the mycopathogen, Verticillium fungicola. Three concentrations (5, 10 and 15%) filtered, microfiltered and sterilized ACT were added to Petri dishes with a PDA medium, and 1 mM of ferric chloride (FeCy. After adding this mixture, a 0.5 cm disc was placed at the center of each dish containing the vegetative and reproductive body of each of the fungi to be tested. All the dishes were incubated at 25°C for seven days, except R. solani y P. aphanidermatum, which developed after 4 days. The addition of 1 mM of FeCl3 deactivated the siderophores present in the ACT, suppressing their inhibition of fungal development. The results obtained with the microfiltered ACT revealed that the microorganisms present in grape marc compost excreted siderophores into the medium which were responsible for inhibiting the growth of the 9 fungi tested. This activity was annulled by the addition of ferric chloride. The same results were achieved with the ACT obtained from filtering. This inhibition was not 100% after adding FeCl3 due to the fact that the microorganisms present in this tea, exhibited other biocontrol mechanisms.

Equilibrium and kinetics study of Gd(III) and U(VI) adsorption from aqueous solutions by modified Sorrel’s cement

Modified Sorrel’s cement was prepared by the addition of ferric chloride. The modified cement (MF5) was analyzed and characterized by different methods. Adsorption of Gd(III) and U(VI) ions in carbonate solution has been studied separately as a function of pH, contact time, adsorbent weight, carbonate concentration, concentration of Gd(III) and U(VI) and temperature. From equilibrium data obtained, the values of Δ H, Δ S and Δ G were found to equal −30.9 kJ ⋅ mol−1, −85.4 J ⋅ mol−1 ⋅,K−1, and −5.4 KJ ⋅ mol−1, respectively, for Gd(III) and 18.9 kJ ⋅ mol−1, 67.8 J ⋅ mol−1 K−1 and −1.3 KJ ⋅ mol−1, respectively, for U(VI). The equilibrium data obtained have been found to fit both Langmuir and Freundlich adsorption isotherms. The batch kinetic of Gd(III) and U(VI) on modified Sorrel’s cement (MF5) with the thermodynamic parameters from carbonate solution were studied to explain the mechanistic aspects of the adsorption process. Several kinetic models were used to test the experimental rate data and to examine the controlling mechanism of the adsorption process. Various parameters such as effective diffusion coefficient and activation energy of activation were evaluated. The adsorption of Gd(III) and U(VI) on the MF5 adsorbent follows first-order reversible kinetics. The forward and backward constants for adsorption, k 1and k 2 have been calculated at different temperatures between 10 and 60∘C. Form kinetic study, the values of Δ H * and Δ S * were calculated for Gd(III) and U(VI) at 25∘C. It is found that Δ H * equals −14.8 kJmol−1 and 7.2 kJmol−1 for Gd(III) and U(VI), respectively, while Δ S * were found equal −95.7 Jmol−1K−1 and −70.5 Jmol−1K−1 for Gd(III) and U(VI), respectively. The study showed that the pore diffusion is the rate limiting for Gd(III) and (VI).

Full Scale Test on Chemical P Removal during a Step Feed BNR Study at John E. Egan Water Reclamation Plant

A full scale nutrient removal study was conducted at the 30-MGD John E. Egan Water Reclamation Plant with a single-stage nitrification activated sludge process and sand filtration. One quarter of the plant’s secondary treatment capacity was used in the study. Simultaneous nitrogen removal through a step feed BNR process and phosphorus (P) removal by chemical precipitation with ferric chloride (FeCl3) were tested to investigate the potential impact of adding FeCl3 to mixed liquor for P removal on the step feed BNR process and on the operation of other unit processes in the plant. During the P removal tests, which were conducted once in early spring and again in early fall of 2005, solutions containing approximately 33% FeCl3 by weight were injected at two different target rates into mixed liquor at the effluent end of the aeration tank. The average daily FeCl3 concentrations applied with respect to 7.5 MGD inflow to the aeration tank were 32.5 to 44.6 mg/L. The average soluble phosphorus (Sol-P) concentrations in 24-hour composite samples of the secondary effluent during the P removal tests ranged from 0.05 to 0.82 mg/L with an arithmetic mean of 0.27 mg/L. The total nitrogen (TN) removal by the step feed BNR process tested averaged 52% and 54% before and during the chemical P removal test in the spring and 52% and 58% in the fall. This indicates that adding ferric chloride to mixed liquor up to 44.6 mg/L for removing particulate FePO4 in the secondary clarifiers has no adverse impact on the step feed BNR process for biological nitrogen removal. The higher percentage TN removal during the P removal test in the fall was probably attributed to the higher MLVSS in the aeration tank resulting from higher solids content in the returned sludge after ferric chloride addition. The accumulation of ferric particles in WAS during the P removal tests appears to have caused the clogging of cloth belt used in the gravity belt thickeners (GBT) for sludge thickening. The sludge thickening performance of the GBT deteriorated during the chemical P removal tests. The performance was improved after the addition of ferric chloride to mixed liquor stopped.

Interactions between Mitochondrial Lipid Oxidation and Oxymyoglobin Oxidation and the Effects of Vitamin E

Off-flavor and discoloration of meat products result from lipid oxidation and myoglobin (Mb) oxidation, respectively, and these two processes appear to be interrelated. The objective of this study was to investigate their potential interaction in mitochondria and the effects of mitochondrial alpha-tocopherol concentrations on lipid oxidation and metmyoglobin (MetMb) formation in vitro. The addition of ascorbic acid and ferric chloride (AA-Fe(3+)) increased ovine and bovine mitochondrial lipid oxidation when compared with their controls (p < 0.05); MetMb formation also increased with increased lipid oxidation relative to controls (p < 0.05). Reactions containing Mb and mitochondria with greater alpha-tocopherol concentrations demonstrated less lipid oxidation and MetMb formation than mitochondria with lower alpha-tocopherol concentrations. Greater mitochondrial alpha-tocopherol concentration was also correlated with increased mitochondrial oxygen consumption in vitro and with a more pronounced effect at pH 7.2 than at pH 5.6. Relative to controls, succinate addition to bovine mitochondria resulted in increased concentrations of ubiquinol 10 and alpha-tocopherol and decreased lipid and Mb oxidation (p < 0.05). Mitochondrial lipid oxidation was closely related to MetMb formation; both processes were inhibited by alpha-tocopherol in a concentration-dependent manner.

Appropriate combination of physico-chemical methods (coagulation/flocculation and ozonation) for the efficient treatment of landfill leachates

An integrated technique consisted of ozonation and coagulation/flocculation processes was studied, aiming to provide an efficient method for the treatment of stabilized/biologically pre-treated leachates, in order to reduce the organic pollutants’ content to concentration values lower than the corresponding limits, imposed by the legislation. Leachates were collected from a municipal landfill site; samples containing around 1000 mg l −1 COD and BOD 5/COD ratio about 0.17 were treated by using two different processes or combinations between them, i.e. ozonation, coagulation–flocculation, ozonation followed by coagulation/flocculation and coagulation/flocculation followed by ozonation. The application of single ozonation resulted to the efficient removal of color and organic loading, due to the respective oxidation, induced by ozonation; however, COD values lower than 200 mg l −1 could be only achieved after prolonged reaction times and for high ozone production rates. The coagulation of leachate samples was studied by the addition of ferric chloride or poly-aluminum chloride agents at various dosages. Maximum COD removal rates (up to 72%) were achieved by the addition of 7 mM Fe, or of 11 mM Al respectively. However, final COD values higher than 200 mg l −1 were obtained indicating the requirement of an additional treatment step. Pre-ozonation followed by coagulation/flocculation was not found to be an efficient treatment approach for this aim, but coagulation/flocculation followed by ozonation, was proved to be an efficient process for the reduction of COD to lower than 180 mg l −1.

Laboratory and Pilot-scale Phosphate and Ammonium Removal by Controlled Struvite Precipitation Following Coagulation and Flocculation of Swine Wastewater

To reduce the suspended solids load to a trickling filter installation, raw swine effluent was pre-treated with ferric chloride and a cationically charged polyacrylamide coagulant resulting in unexpected struvite accumulation downstream of this post-separation process. Using this pre-treated swine manure, struvite precipitation studies were carried out as a function of pH at laboratory and pilot batch and continuously operated scales. An optimal reaction time of 30 min was established for struvite precipitation in the pre-treated swine wastewater at pH 8.5, minimizing the co-precipitation of interfering minerals. Ferric chloride addition resulted in magnesium solubilization, such that no external additional source of magnesium was required for struvite formation. Aeration alone did not result in significant pH increases, so base addition was required for pH adjustment. X-ray diffraction revealed that the only crystalline phase produced was struvite. Removal of phosphate and ammonium attained 98% and 17% respectively in laboratory scale experiments. At the pilot-scale, removal attained 99% and 15% of phosphate and ammonium in both batch and continuously (HRT=1h) operated reactors.

Long-term Changes in Iron and Phosphorus Sedimentation in Vadnais Lake, Minnesota, Resulting from Ferric Chloride Addition and Hypolimnetic Aeration

Changes in iron (Fe) and phosphorus (P) cycling in Vadnais Lake, Minnesota, resulting from ferric chloride addition and hypolimnetic aeration are evaluated by repeat sampling of bottom sediments over a 13-year period: in 1985 (pre-treatment), and in 1990 and 1998 (post-treatment). Lead-210 derived accumulation rates for Fe, Mn, total-P, and P-fractions are combined with input/output monitoring to construct chemical mass-balances for each of the three time periods. Iron injections/aeration caused large and sustained reductions in water-column total-P by increasing phosphorus removal to the sediments and preventing its recycling during stratification. Annual whole-lake phosphorus sedimentation rose from 1.26 to 1.52 t between 1985 and 1990, equivalent to a doubling of in-lake retention of external P loads (from 19% to 38%). Most of the increase is represented in the labile Fe-bound fraction. The measured sedimentary fluxes for 1985 and 1990 are similar to those calculated by difference from inflow/outflow data, whereas measured P sedimentation in 1998 (2.43 t·yr−1) is three times higher than that estimated from input/output calculations. These results suggest surface enrichment by upward P diffusion within the sediment column. Present-day Fe accumulation rates (24 t·yr−1) are 33% greater than those immediately preceding treatment and 14% greater than pre-settlement fluxes (21 t·yr−1). The 6 t·yr−1 increase in Fe accumulation between 1985 and 1998 is roughly equal to the rate of iron injection to Vadnais Lake. Fifty-four tons of iron addition to the Lambert Creek tributary between 1990 and 1998 have also enriched littoral sediments in Fe, P, and Mn near the creek's outfall. These engineering solutions have substantially improved water quality in Vadnais Lake, but continued hypolimnetic aeration will be required to prevent internal phosphorus loading from the large reservoir of labile sedimentary P that has accumulated since treatment began.

Remediation of arsenic-contaminated soils and washing effluents

Laboratory experiments were conducted to determine the distribution of various arsenic species in tailings and soils. Other specific goal of the tests were to evaluate the extraction efficiency of arsenic using alkaline or acid washing, to determine optimum operational parameters of alkaline washing, and to evaluate the arsenic precipitation of washing effluents by pH adjustment or ferric chloride addition. Alkaline washing using sodium hydroxide was found to be favorable in removing arsenic from tailings or soils having a higher portion of arsenic in the operationally defined crystalline mineral fraction of crystalline oxide and amorphous aluminosilicates. This is due to the ligand displacement reaction of hydroxyl ions with arsenic species and high pH conditions that can prevent readsorption of arsenic because predominant negatively charged crystalline oxides do not attract the negatively charged oxyanions. For tailings, sodium hydroxide had 10–20 times higher extraction efficiencies than hydrochloric- or citric acid. The optimum concentration of sodium hydroxide for soil washing was determined to be 200 mM for all samples, while the optimum ratios were 10:1 and 5:1 for tailings and field/river sedimentary soils, respectively. The washing effluent of river soil was effectively treated by adjusting pH to 5–6 with hydrochloric acid, resulting in arsenic concentrations of <50 μg l −1. In the case of field soil effluent, an addition of ferric chloride with a minimum mass ratio of 11 (Fe/As) was needed to reduce the arsenic below 50 μg l −1.

Effects of Lime and Ferric Chloride Addition on Volatile Organic Sulfur Compounds Production in Biosolids

Effects of Lime and Ferric Chloride Addition on Volatile Organic Sulfur Compounds Production in Biosolids

Simultaneous Nitrification-Denitrification and Clarification in a Pseudoliquified Activated Sludge System

This paper describes results from a pilot study of a novel wastewater treatment technology, which incorporates nutrient removal and solids separation to a single step. The pseudoliquified activated sludge process pilot system was tested on grit removal effluent at flowrates of 29.4 to 54.7 m3/d, three different solid residence times (SRT) (15, 37, and 57 days), and over a temperature range of 12 to 28 degrees C. Despite wide fluctuations in the influent characteristics, the system performed reliably and consistently with respect to organics and total suspended solids (TSS) removals, achieving biochemical oxygen demand (BOD) and TSS reductions of > 96% and approximately 90%, respectively, with BOD5 and TSS concentrations as low as 3 mg/L. Although the system achieved average effluent ammonia concentrations of 2.7 to 3.2 mg/L, nitrification efficiency appeared to be hampered at low temperatures (< 15 degrees C). The system achieved tertiary effluent quality with denitrification efficiencies of 90 and 91% total nitrogen removal efficiency at a total hydraulic retention time of 4.8 hours and an SRT of 12 to 17 days. With ferric chloride addition, effluent phosphorous concentrations of 0.5 to 0.8 mg/L were achieved. Furthermore, because of operation at high biomass concentrations and relatively long biological SRTs, sludge yields were over 50% below typical values for activated sludge plants. The process was modeled using activated sludge model No. 2, as a two-stage system comprised an aerobic activated sludge system followed by an anoxic system. Model predictions for soluble BOD, ammonia, nitrates, and orthophosphates agreed well with experimental data.

Harnessing Anionic Rearrangements on the Benzenoid Ring of Quinoline for the Synthesis of 6,6‘-Disubstituted 7,7‘-Dihydroxy-8,8‘-biquinolyls

7,7'-Bis(((dimethylamino)carbonyl)oxy)-8,8'-biquinolyl (5) was prepared in 71% yield by regioselective directed ortho metalation (DoM) of N,N-dimethyl O-quinol-7-yl carbamate (2) with LDA followed by oxidation with anhydrous ferric chloride. DoM of 5 with excess LDA induced double anionic ortho-Fries rearrangement and gave 6,6'-bis((dimethylamino)carbonyl)-7,7'-dihydroxy-8,8'-biquinolyl (8). Treatment of N,N-diethyl O-(8-iodoquinol-7-yl) carbamate (16) with LDA in THF solvent at -78 degrees C, followed by addition of anhydrous ferric chloride, resulted in an efficient tandem halogen-dance dimerization process which afforded 7,7'-bis(((diethylamino)carbonyl)oxy)-6,6'-diiodo-8,8'-biquinolyl (17) directly in 54% yield.

The use of simultaneous chemical precipitation in modified activated sludge systems exhibiting biological excess phosphate removal: Part 7: Application of the IAWQ model

The IAWQ Activated Sludge Model (ASM) No. 2 is a kinetic-based model and incorporates two simple processes for chemical precipitation and redissolution that are readily integrated with biological processes for carbon, nitrogen and phosphorus remov al. This model was applied to experimental data collected as part of this study from parallel pilot-scale 3-stage Phoredox systems with and without simultaneous dosing of chemical precipitant. The precipitants tested were alum, ferric chloride and ferrous-ferric chloride. The model was calibrated to the control unit (without precipitant addition) in order to match effluent phosphate (P) predictions (and hence P removal) as closely as possible. The same calibration was then applied to modelling the test unit (wit h precipitant addition). It was found that the default model input stoichiometry for the precipitation reaction (ideal 1:1 molar ratio of metal ion (Me) to P) was suitable for ferric chloride addition at a 20 d sludge age, but did not accurately reflect the test sy stem behaviour for all experimental periods. A lower stoichiometry (0.60 to 0.75) was required for alum at a 20 d sludge age, and fo r a blend of predominantly ferrous chloride at a 10 d sludge age. The input stoichiometry was further decreased under P-limiting conditions. A simple approach to, and possible reasons for, the manipulation of the model stoichiometry are discussed in the li ght of observed stoichiometry from system P removal and fractionation data collected as part of this study. Furthermore, an alterna tive approach based on manipulation of the precipitation (and hence redissolution) kinetic constant is suggested and evaluated using available experimental data. Model predictions and observed data in respect of polyphosphate (polyP) and suspended solids are a lso compared and discussed. It is concluded that the ASM No. 2 model provides a useful basis for modelling simultaneous P precipitation, provided certain minor modifications are made. Further investigation into the kinetics of the precipitation process(es) is recommended, particularly in relation to the effect of system sludge age. The model lends itself to further enha ncement by incorporating additional physico-chemical processes.

Degradation of nonylphenol by anaerobic microorganisms from river sediment

We investigated the degradation of nonylphenol monoethoxylate (NP1EO) and nonylphenol (NP) by anaerobic microbes in sediment samples collected at four sites along the Erren River in southern Taiwan. Anaerobic degradation rate constants ( k 1) and half-lives ( t 1/2) for NP (2 μg/g) ranged from 0.010 to 0.015 1/day and 46.2 to 69.3 days respectively. For NP1EO (2 μg/g), the ranges were 0.009–0.014 1/day and 49.5–77.0 days respectively. Degradation rates for NP and NP1EO were enhanced by increasing temperature and inhibited by the addition of acetate, pyruvate, lactate, manganese dioxide, ferric chloride, sodium chloride, heavy metals, and phthalic acid esters. Degradation was also measured under three anaerobic conditions. Results show the high-to-low order of degradation rates to be sulfate-reducing conditions > methanogenic conditions > nitrate-reducing conditions. The results show that sulfate-reducing bacteria, methanogen, and eubacteria are involved in the degradation of NP and NP1EO, with sulfate-reducing bacteria being a major component of the river sediment.

Tensile Bond Strength of 4-META/MMA-TBB Resin to Ground Bovine Enamel Using a Self-etching Primer

The purpose of this study was to examine the effectiveness of self-etching primer in adhering 4-META/MMA-TBB resin to bovine enamel. In this study, we designed an original self-etching primer which contained an aqueous mixture of 4-MET, 35 wt% HEMA, and ferric chloride. The polished bovine enamel surface was treated with self-etching primer for 30 seconds. Tensile bond strength of 4-META/MMA-TBB resin to enamel was measured after 1-day immersion in water at 37 degrees C. The self-etching primer containing 30 wt% 4-MET and 35 wt% HEMA (4MET30) gave a significantly higher bond strength of 11.2+/-2.8 MPa than other self-etching primers. The addition of ferric chloride into 4MET30 primer significantly decreased tensile bond strength. SEM observation revealed that 4MET30 treatment produced no distinct dissolution on enamel. When compared with phosphoric acid etching, the self-etching primer containing 30 wt% 4-MET and 35 wt% HEMA was more superior in adhering 4-META/MMA-TBB resin to enamel.

Reduction of arsenic content in a complex galena concentrate by Acidithiobacillus ferrooxidans

BackgroundBioleaching is a process that has been used in the past in mineral pretreatment of refractory sulfides, mainly in the gold, copper and uranium benefit. This technology has been proved to be cheaper, more efficient and environmentally friendly than roasting and high pressure moisture heating processes. So far the most studied microorganism in bioleaching is Acidithiobacillus ferrooxidans. There are a few studies about the benefit of metals of low value through bioleaching. From all of these, there are almost no studies dealing with complex minerals containing arsenopyrite (FeAsS). Reduction and/or elimination of arsenic in these ores increase their value and allows the exploitation of a vast variety of minerals that today are being underexploited.ResultsArsenopyrite was totally oxidized. The sum of arsenic remaining in solution and removed by sampling represents from 22 to 33% in weight (yield) of the original content in the mineral. The rest of the biooxidized arsenic form amorphous compounds that precipitate. Galena (PbS) was totally oxidized too, anglesite (PbSO4) formed is virtually insoluble and remains in the solids. The influence of seven factors in a batch process was studied. The maximum rate of arsenic dissolution in the concentrate was found using the following levels of factors: small surface area of particle exposure, low pulp density, injecting air and adding 9 K medium to the system. It was also found that ferric chloride and carbon dioxide decreased the arsenic dissolution rate. Bioleaching kinetic data of arsenic solubilization were used to estimate the dilution rate for a continuous culture. Calculated dilution rates were relatively small (0.088–0.103 day-1).ConclusionProper conditions of solubilization of arsenic during bioleaching are key features to improve the percentage (22 to 33% in weight) of arsenic removal. Further studies are needed to determine other factors that influence specifically the solubilization of arsenic in the bioleaching system such as: pH, dissolved oxygen concentration, redox potentials, nature of concentrate and temperature among others. At. ferrooxidans was able to completely oxidize the minerals present during the arsenic bioleaching. Other elements present originally in the concentrate such as Zn, Sb, and Cu were also solubilized. The process of bioleaching is expected to be influenced by mechanisms that still need to be established due to the diversity of the minerals involved and by the presence of traces of metals in the concentrate. The increase in pulp density generates a decrease in the dissolved arsenic concentration. This decrease is greater in runs where air was not injected to the system. The maximum rate of arsenic dissolution in the concentrate was found using; small surface area of particle exposure, low pulp density, injecting air and adding 9 K medium to the system. The effect of addition of ferric chloride during the arsenic bioleaching resulted in a decrease of the solubilized arsenic in the system. The presence of CO2 is associated to the decrease in arsenic dissolution.

Effect of ferric chloride addition on the removal of Cu and Zn complexes with EDTA during municipal wastewater treatment

The presence of the synthetic chelating agent ethylenediaminetetraacetic acid (EDTA) in municipal wastewater has a significant impact on the efficacy of wastewater treatment plants because pollutant metal–EDTA complexes are difficult to remove. To understand the potential of FeCl 3 addition during primary treatment to improve metal removal, laboratory experiments and a full-scale study were conducted. Results of laboratory experiments designed to simulate primary and secondary wastewater treatment indicate that a portion of pollutant metal–EDTA species can be converted into FeEDTA − by addition of FeCl 3 during simulated primary treatment. Addition of FeCl 3 also resulted in improved metal removal by adsorption. The combination of these two processes improved removal of Cu and Zn by 20% during simulated primary treatment. During full-scale treatment, a slight increase in the concentration of FeEDTA − in secondary effluent was observed when FeCl 3 was added during primary treatment. However, FeCl 3 addition had no observable effect on metal concentrations in the wastewater effluent. The most noticeable change in EDTA speciation at full scale occurred during primary treatment, where most of the pollutant metal–EDTA complexes were converted into FeEDTA −, irrespective of whether or not FeCl 3 was added. The formation of FeEDTA − during primary treatment plays a potentially important role in metal removal and should be considered in future evaluations of wastewater treatment plant performance.