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PubMed2001

Treatment of phosphoric acid plant wastewater using Fenton's reagent and coagulants.

The results of treatability studies viz., Fenton reaction and physico-chemical (coagulation) treatment using lime, alum, Fe salts and polyaluminium chloride (PAC) performed on wastewater generated from a unit manufacturing technical grade phosphoric acid are reported. Due to low biochemical oxygen demand (BOD) chemical oxygen demand (COD) ratio and very low pH, this wastewater is not amenable for biological treatment. The treatability studies indicated that it is possible to remove 75-80% COD using Fenton's reagent at optimum doses of 1.0 g/L FeSO4 and 2 ml of 30% H2O2. Simultaneously, significant quantities of suspended solids, phosphate and fluoride are also removed. Polyaluminium chloride is found to be more effective towards suspended solids (SS), COD, phosphate and fluoride removal, when compared to other coagulants used in the present study. Addition of an anionic polyelectrolyte (Magnafloc 156) to PAC improved the performance further. A treatment scheme that consists of neutralization (pH 4) + Fenton's reagent + neutralization (pH 7.5) + PAC/Magnafloc 156 is found to be effective in treating phosphoric acid plant wastewater to meet marine discharge standards.

Alum Compounds↗
PubMed1992

Effects of high iron and sulfate ion concentrations on dry matter digestion and volatile fatty acid production by ruminal microorganisms.

The inhibitory effects of iron- and sulfate-containing compounds on the in vitro digestion of a balanced forage diet by mixed populations of ruminal microorganisms were examined in batch cultures. Compounds containing ferrous and ferric cations consistently inhibited DM digestion by up to 36% when added Fe concentrations in cultures were between 100 and 1,000 mg/L. Increased sulfate concentrations of up to 200 mg/L or chloride concentrations of up to 635 mg/L were not associated with decreased DM digestion. Ammonium sulfate additions that provided 200 mg/L of added sulfur increased (P less than .05) digestibility by 10%. Sulfate-containing iron salts tended to be less inhibitory than chloride salts and were associated with increased gas production during digestion. Ferric chloride inhibited (P less than .05) microbial activities at lower concentrations than ferrous chloride. Data suggest that excessive iron supplementation or contamination of feeds with iron-containing pollutants may decrease microbial activities in the rumen.

Ammonium Sulfate↗
PubMed2003

[The application of polyferric chloride in micro-flocculation deep bed filtration].

Compared with polyaluminium chloride (PAC), the application efficiency of polyferric chloride (PFC) were investigated by pilot micro-flocculation deep bed filtration. The results show that, under the condition of lower dosage (Fe:Al = 3:5), the headloss cycle of PFC was 63 h, and its output in a cycle was 1504 m3/m2, but PAC headloss cycle was 53 h with its output 1266 m3/m2. It is concluded that PFC was benefit to prolong operation cycle and improve output. The research on particle removal mechanism shows that PFC could enhance the floc growth, and the PFC flocs could be effectively entrapped and dehydrated. Therefore PFC is more suitable for the micro-flocculation deep bed filtration process than PAC.

Aluminum Chloride↗
PubMed1983

Cloning and expression of the fhu genes involved in iron(III)-hydroxamate uptake by Escherichia coli.

Each of the four hydroxamate compounds, ferrichrome, aerobactin, rhodotorulic acid, and coprogen, known to transport ferric iron into Escherichia coli requires a specific outer membrane receptor protein. In addition, common transport functions for all four ferric hydroxamate compounds have been identified in the 3.5-min region of the linkage map and designated fhu. The fhu region was cloned into pBR322. By restriction analysis, Tn5 insertion mutations, and complementation studies between plasmid fragments and chromosomal mutants at least four loci in the order fhuA fhuC fhuD fhuB were found. The genetic products were determined in maxicells and minicells. fhuA codes for the known 78,000-dalton receptor protein and the 81,000-dalton precursor in the outer membrane, fhuC codes for a 30,000-dalton protein, and fhuD encodes a 26,000-dalton protein in the cytoplasmic membrane. No protein(s) could be assigned to the fhuB region. Truncated proteins derived from partial fhuA genes (68,000, 42,000, and 39,000 daltons) and a partial fhuD gene (24,000 daltons) and the strong polar effect on the expression of the genes indicated the direction of transcription to be from fhuA to fhuD.

Bacterial Outer Membrane Proteins↗
PubMed1999

Sodium ferric gluconate complex in sucrose is safe and effective in hemodialysis patients: North American Clinical Trial.

A new intravenous (i.v.) iron compound, sodium ferric gluconate complex in sucrose (Ferrlecit, R&D Laboratories, Inc, Marina Del Rey, CA), was administered over 8 consecutive dialysis days in equally divided doses to a total of either 0.5 or 1.0 g in a controlled, open, multicenter, randomized clinical study of anemic, iron-deficient hemodialysis patients receiving recombinant human erythropoietin (rHuEPO). Effectiveness was assessed by increase in hemoglobin and hematocrit and changes of iron parameters. Results were compared with historically matched controls on oral iron. High-dose i.v. treatment with 1.0 g sodium ferric gluconate complex in sucrose resulted in significantly greater improvement in hemoglobin, hematocrit, iron saturation, and serum ferritin at all time points, as compared with low-dose i.v. (0.5 g) or oral iron treatment. Despite an initial improvement in mean serum ferritin and transferrin saturation, 500 mg i.v. therapy did not result in a significant improvement in hemoglobin at any time. Eighty-three of 88 patients completed treatment with sodium ferric gluconate complex in sucrose: 44 in the high-dose and 39 in the low-dose group. Two patients discontinued for personal reasons. The other three discontinued because of a rash, nausea and rash, and chest pain with pruritus, respectively. In comparison with 25 matched control patients, adverse events could not be linked to drug therapy, nor was there a dose effect. In conclusion, sodium ferric gluconate complex in sucrose is safe and effective in the management of iron-deficiency anemia in severely iron-deficient and anemic hemodialysis patients receiving rHuEPO. This study confirms the concepts regarding iron therapy expressed in the National Kidney Foundation Dialysis Outcomes Quality Initiative (NKF-DOQI) that hemodialysis patients with serum ferritin below 100 ng/mL or transferrin saturations below 18% need supplementation with parenteral iron in excess of 1.0 g to achieve optimal response in hemoglobin and hematocrit levels.

Adult↗
PubMed1995

Chemiluminescence and EPR studies on the excitation site of ferric-heme-oxo complexes of natural and model heme systems.

Chemiluminescence was detected both in the reaction system of H2O2 plus heme proteins such as methemo- and metmyoglobin and ferric-protoheme complexes used as a model system. The intensity of chemiluminescence was found to be mediated by ligand binding to the sixth coordination site of the ferric-protoheme compounds, e.g. chemiluminescence was not observed with the bisimidazole ferric-protoheme complex. On the other hand the pentacoordinated histidine ferric-protoheme complex exhibited strong light emission. Comparative studies with various ligand-heme compounds elucidated that light emission was inversely correlated with the binding strength of the respective ligand at the sixth coordination site. The basic reaction mechanism causing the establishment of an excited state was studied by monitoring chemiluminescence and EPR signal formation of ligand-modified heme proteins in the presence of different electron donors. External electron donors such as Trolox C, TMPD and ascorbic acid affected a strong reduction in the development of chemiluminescence suggesting the essential involvement of an inner-molecular electron transfer process. Our results allow the conclusion that chemiluminescence is generated from the decay of an excited state of oxo-heme compounds established as a result of a one electron transfer step from a ligand group to heme iron.

Binding Sites↗
PubMed1983

Styrene oxidation to styrene oxide by hydroxyl radicals produced during reaction of xanthine with xanthine oxidase in the presence of Fe3+.

Styrene was oxidized to styrene oxide during reaction of xanthine (X) with xanthine oxidase (XO) in the presence of Fe3+. This reaction showed a dose-dependent requirement of iron and was inhibited by superoxide dismutase (SOD) and catalase, indicating that both the superoxide anion and H2O2 were essential. Styrene oxide production was inhibited by hydroxyl radical scavengers indicating that this reactive oxygen intermediate could be the proximal oxidant involved in styrene oxidation to styrene oxide.

Chemical Phenomena↗
PubMed2006

Characterisation of solid and liquid fractions of dairy manure with regard to their component distribution and methane production.

Dairy manure with a total solids content of 77.2g TS/l was separated by means of screening and coagulation-flocculation treatments, using CaO as coagulant and a cationic polyacrylamide as flocculant, obtaining liquid and solid fractions. The solid fraction separated contained 33.4% of the initial total mass of dairy manure plus chemical solutions, containing also 75.2% of the TS, 80.4% of the VS, 58.5% of the total Kjeldahl nitrogen (TKN) and 87.4% of the total phosphorus (P(T)) present in the initial dairy manure. 83.7% of the liquid fraction chemical oxygen demand (COD) was anaerobically biodegradable (COD(BD)). Methane production for the separated liquid fraction was 0.604l CH4 NCTP/g VS added, being 0.307 and 0.371l CH4 NCTP/g VS added for dairy manure and screened dairy manure, respectively. The characteristics of this liquid fraction would allow its treatment in high loading anaerobic reactors having shorter hydraulic retention times, smaller reactor size and a higher methane volumetric production rate than conventional anaerobic reactors treating either manure or screened manure.

Anaerobiosis↗
PubMed2005

Synergic effect of calcium oxide and iron (III) oxide on the dechlorination of hexachlorobenzene.

Dechlorination of hexachlorobenzene (HCB) was achieved by a mixture of commercial CaO and alpha-Fe2O3 (CaO/alpha-Fe2O3) in closed systems at temperatures of 300 degrees C and 350 degrees C, which exhibited a synergic effect compared to CaO or alpha-Fe2O3 alone, and the dechlorination efficiency was dramatically enhanced. When CaO and alpha-Fe2O3 coexisted, HCB was dechlorinated by about 98% after 0.5 h reaction at 300 degrees C. All TeCB-, TrCB-, and DCB-isomers were detected, showing the presence of more than one dechlorination pathway. The pathway to form 1,2,4-TrCB must be a major pathway because the greatest amount of 1,2,4-TrCB was detected. There existed discrepancy of the material balance between the starting and dechlorinated materials. It implies that besides dechlorination other decomposition processes may be present. The mechanism of synergic effect of calcium and iron oxides was investigated.

Calcium Compounds↗
PubMed2004

Removal of direct red 12B and methylene blue from water by adsorption onto Fe (III)/Cr (III) hydroxide, an industrial solid waste.

Removal of direct red 12B and methylene blue by adsorption onto Fe (III)/Cr (III) hydroxide was studied using various parameters such as agitation time, dye concentration, adsorbent dose and pH. Equilibrium adsorption data followed both Langmuir and Freundlich isotherms. Adsorption followed second-order rate kinetics. The Langmuir adsorption capacity (Qo) was found to be 5.0 and 22.8 mg dye per g of the adsorbent for direct red 12B and methylene blue, respectively. Acidic pH was favorable for the adsorption of direct red 12B and basic pH for methylene blue. Desorption studies showed that chemisorption seems to be the major mode of adsorption.

Adsorption↗
PubMed2001

An on-belt elemental analyser for the cement industry.

On-line control of raw mill feed composition is a key factor in the improved control of cement plants. A new and improved on-conveyor belt elemental analyser for cement raw mill feed based on neutron inelastic scatter and capture techniques has been developed and tested successfully in Adelaide Brighton's Birkenhead cement plant on highly segregated material with a depth range of 100 to 180 mm. Dynamic tests in the plant have shown analyser RMS total errors of 0.49, 0.52, 0.38 and 0.23 wt% (on a loss free basis) for CaO, SiO2, Al2O3 and Fe2O3 respectively, when 10-minute counting periods are used.

Aluminum Oxide↗
PubMed2003

Immobilization mechanisms of arsenate in iron hydroxide sludge stabilized with cement.

Leaching tests, Fourier transform infrared spectroscopy (FTIR), extended X-ray absorption fine structure (EXAFS) spectroscopy, and thermodynamic modeling were performed to investigate arsenate [As(V)] immobilization mechanisms in iron hydroxide sludge stabilized with cement. The sludge from a groundwater remediation site in Tacoma, WA was mixed and immobilized with premixed cement to reach cement-to-sludge ratios of 2.5, 3.3, 5, 10, and 20 (wt premixed cement/wt dry sludge). The EXAFS analysis determined that As(V) formed bidentate mononuclear complexes on the iron hydroxide surface in the sludge. The adsorbed As(V) had a characteristic FTIR band at 830 cm(-1). Cement treatment converted the adsorbed As(V) to calcium arsenate precipitate with a FTIR peak at 860 cm(-1). The chemical forms of the As(V) were incorporated in an adsorption triple layer model (TLM) to describe the leaching behavior of As(V) in a pH range between 3 and 12. Cement treatment significantly reduced arsenic mobility because of the formation of the sparingly soluble calcium arsenate.

Arsenates↗
PubMed2006

Optoelectronic switches based on wide band gap semiconductors.

Switching of photocurrent direction in semiconducting systems upon changes of the electrode potential or incident light wavelength was realized by a series of photoelectrodes covered with titania modified with pentacyanoferrate complexes, [Fe(CN)(5)L](n)(-) (L = NH(3), thiodiethanol, thiodipropanol). These materials were characterized by optical spectroscopy and electrochemistry. The structure of the surface complexes was modeled using simple quantum-chemical models. The electrodes described in this paper enable control of the photocurrent direction by two stimuli: Changing the wavelength or the photoelectrode potential easily switches the direction of photocurrent. The materials are different from those of similar characteristics studied by other authors: They are not composites comprising of two types of semiconductors but rather engineered uniform materials. The photocurrent switching phenomenon is an intrinsic feature resulting from a specific electronic structure of the surface-modified semiconductor.

Ammonia↗
PubMed2004

Domain-wall superconductivity in superconductor-ferromagnet hybrids.

Superconductivity and magnetism are two antagonistic cooperative phenomena, and the intriguing problem of their coexistence has been studied for several decades. Recently, artificial hybrid superconductor-ferromagnet systems have been commonly used as model systems to reveal the interplay between competing superconducting and magnetic order parameters, and to verify the existence of new physical phenomena, including the predicted domain-wall superconductivity (DWS). Here we report the experimental observation of DWS in superconductor-ferromagnet hybrids using a niobium film on a BaFe(12)O(19) single crystal. We found that the critical temperature T(c) of the superconductivity nucleation in niobium increases with increasing field until it reaches the saturation field of BaFe(12)O(19). In accordance with the field-shift of the maximum value of T(c), pronounced hysteresis effects have been found in resistive transitions. We argue that the compensation of the applied field by the stray fields of the magnetic domains as well as the change in the domain structure is responsible for the appearance of the DWS and the coexistence of superconductivity and magnetism in the superconductor-ferromagnet hybrids.

Barium Compounds↗