Cr Retention Research Articles

Retention and distribution of Cu, Pb, Cr, and Zn in a full-scale hybrid constructed wetland receiving municipal sewage

This study was conducted to investigate the retention and distribution of Cu, Pb, Cr, and Zn in a hybrid constructed wetland (CW) that consists of both vertical baffled flow wetlands (VBFWs) and horizontal subsurface flow wetlands (HSSFs) with unique flow regimes and oxygen distribution. The heavy metal concentrations in water, sediments, and plant tissues in the hybrid CW were analysed. The removal of heavy metals from the water stream in the monitoring period was not statistically significant. Metal concentrations in the sediments generally decreased along the wastewater treatment process. The reductive anaerobic condition in the VBFW may promote the sulphate reduction and form highly insoluble Cu, Pb, and Zn sulphides, resulting in the higher concentration of the bivalent cations in the VBFW sediments than the corresponding values in the HSSF; however, the aerobic and anoxic environments in the HSSF enhanced the removal of Cr with the co-precipitation of iron and manganese oxides, and their hydroxides. Metal concentrations in plant tissues were not significantly influenced by the concentrations in sediments, while roots contained statistically higher metal concentrations than stems and leaves. The sediments stored 94.01, 86.31, 95.85, and 89.51% of the total Cu, Pb, Cr, and Zn retained in the hybrid CW system, respectively, while only small fractions (<10%) were accumulated in the harvestable macrophyte tissues. It is important to clean not only the accessible sediments in free water surface tank and ponds but also the embedded sediments in vegetated beds for the sustainable removal of heavy metals.

Characterization of Chromium Species in Urban Runoff

Little is known about the presence of the element Cr in its toxic hexavalent form Cr(VI) in stormwater runoff from urban areas. Most studies report only total Cr concentration, i.e., including also the nontoxic Cr(III) molecular form. The objective of this study was to evaluate a field method based on cation-exchange for characterization of Cr species in urban stormwater runoff and soil leachate. We used a 0.05 mol L Na and Ca solution and a soil leachate as matrices and spiked these with Cr(III), Cr(VI), or both in the concentration range of 1 to 100 μg L. We then filtered the test samples through cation-exchange cartridges. In the Na-Ca salt matrix, the Cr(III) was retained 100% and recovery values of Cr(VI) were 86 to 100%. Furthermore, in such a matrix, each cartridge could be reused at least nine times without a drop in retention of Cr(III) or recovery of Cr(VI). In a soil leachate matrix, the method appeared less applicable. Apparently Cr(III) forms complexes with dissolved organic matter, allowing it to bypass the cartridge, resulting in incomplete Cr(III) retention and thus incomplete speciation. The complexes are formed rapidly after spiking, thus changes in the Cr-species distribution are likely to occur within a few hours when fresh samples are stored. Furthermore, we concluded that Cr(III) at neutral pH in pure solution or complexed with dissolved organic C can sorb irreversibly to polyethylene and polypropylene containers. Our findings show that there is still a need for a method that can be applied to urban runoff in the field. Furthermore, cartridge speciation methods should ideally be tested before being applied on solutions containing organic matter.

Decarburization of ferrochrome and high alloy steels with optimized gas and slag phases towards improved Cr retention

Chromium is a high value metal and the retention of the same during the refining of high carbon ferrochrome as well as high alloy steel has significant economic and environmental impacts. The loss of chromium during the decarburization is generally minimized using argon-oxygen mixtures thereby reducing the oxygen partial pressure (PO2) of the oxidant gas. In the current study, experiments were carried out in an induction furnace and CO2 was introduced with the view to partly reduce PO2 and partly as an oxidizer. During these experiments, the decarburization of molten Cr-alloy was conducted using pure O2, pure CO2 or O2+CO2 mixtures. The results demonstrated that the Cr loss can be minimized under CO2 introduction. The kinetic analysis showed that the mass transfer is effective due to the production of 2CO gas molecules from one CO2 molecule during the reaction which will improve the stirring of the bath. Besides, CO2 reacts with carbon in melt is an endothermic reaction, introduction of CO2 could be a cooler during the refining process, hence the temperature could be controlled by controlling the diluting gas amount, in this case, the over heat of bath refractory could be prevented and the lifetime of refractory could be extended.

Effects of Permeable Reactive Composite Electrodes on Hexavalent Chromium in the Electrokinetic Remediation of Contaminated Soil

Electrokinetic transport processes have been shown to have potential for effective removal of heavy metals from soils. However, pH changes near the anode and cathode limit their widespread application in remediation of contaminated soils. Permeable reactive composite electrodes (PRCEs) were constructed by attaching reactive materials such as Fe(0) and zeolite to electrodes, and effects of composite electrodes on pH control, chromium (Cr) removal efficiency, and adjustment of speciation of Cr were studied in the electrokinetic remediation of Cr(VI)-spiked soil. Composite electrodes consisting of permeable reactive materials gave better pH control and Cr removal efficiency compared to application of traditional electrodes, and a reactive layer of Fe(0) and zeolite in the anode exhibited the best performance compared to zeolite or Fe(0) alone. After 5 d of electrokinetic remediation with a DC voltage of 2.0 V/cm, the Fe(0)+zeolite reactive layer buffered pH fluctuation, maintained soil pH in the range of 5.5–8.5, and increased Cr(VI) remediation efficiency up to 97% in each section of soil. Additionally, it resulted in lower Cr(III) residues, enhancement of the amount of Cr retention up to 8× and 1.8×, respectively, and transformation of 98% of the Cr(VI) to lower toxicity Cr(III). After remediation, heavy metal ions were removed from the remediation system simply by unplugging the composite electrodes, which theoretically needed no further treatment—a major advantage over traditional electrokinetic remediation methods. This study provides a theoretical basis for exploitation of PRCEs, which is a practical option for future applications.

Solid phase extraction and determination of Cr(III) by spectrophotometry using cefaclor as a complexing reagent and FAAS

The present study reports on the application of modified groundnut shell as a new, easily prepared, and stable sorbent for the extraction of trace amount of Cr(III) in aqueous solution. 2-Hydroxybenzaldiminoglycine was immobilized on groundnut shells in alkaline medium and then used as a solid phase for the column preconcentration of Cr(III). The elution was carried out with 3 mL of 2 mol L(-1) HCl. The amount of eluted Cr(III) was determined by spectrophotometry using cefaclor as a complexing reagent and by flame atomic absorption spectrometry (FAAS). Different experimental variables such as pH, amount of solid sorbent, volume and concentration of eluent, sample and eluent flow rate, and interference of other metal ions on the retention of Cr(III) were studied. Under the optimized conditions, the calibration curves were found to be linear over the concentration range of 13-104 and 10-75 μg L(-1) with a detection limit of 3.64 and 1.24 μg L(-1) for spectrophotometric method and FAAS, respectively. An enrichment factor of 200 and RSD of ±1.19-1.49 % for five successive determinations of 25 μg L(-1) were achieved. The column preconcentration was successfully applied to the analysis of tap water and underground water samples.

Separation and preconcentration of trace amounts of Cr(III) ions on ion imprinted polymer for atomic absorption determinations in surface water and sewage samples

A new type of Cr(III)-imprinted polymer was prepared from Cr(III)–pyrrolidinedithiocarbamate complex, acrylamide functional monomer and ethylene glycol methacrylate cross-linking agent. The polymer was employed as a selective solid phase extraction material for separation of trace amounts of Cr(III) ions under dynamic conditions. The effects of the conditioning of imprinted polymer, conditions of Cr(III) retention and elution were studied. It was found that Cr(III) ions can be retained on tested sorbent with high efficiency and repeatability (87%, RSD=3.2%) from a solution of pH 3.50–4.75. The quantitative elution of analyte was obtained with 0.2molL−1 nitric acid solution. The retention of Cr(VI) ions on the polymer in the studied pH range (1.0–7.0) was at the level of 10–15%. The selectivity of prepared sorbent towards Cr(III) ions was good in the presence of Cu(II) and Ni(II) ions and worse in the presence of Fe(III) ions at a concentration higher than 0.5μgmL−1. The detection limit for Cr(III) obtained by electrothermal atomic absorption spectrometry (ETAAS) after preconcentration of 40mL of sample on the polymer was 0.018ngmL−1. The developed separation method was successfully applied to the ETAAS determination of trace amounts of Cr(III) in tap and river water and municipal sewage.

Adsorption kinetics of chromium(III) removal from aqueous solutions using natural red earth

Laboratory-scale-simulated experiments were carried out using Cr(III) solutions to identify the Cr(III) retention behavior of natural red earth (NRE), a natural soil available in the northwestern coastal belt of Sri Lanka. The effects of solution pH, initial Cr(III) concentration and the contact time were examined. The NRE showed almost 100 % Cr(III) adsorption within the first 90 min. [initial [Cr(III)] = 0.0092–0.192 mM; initial pH 4.0–9.0]. At pH 2 (298 K), when particle size ranged from 125 to 180 μm the Cr(III) adsorption data were modeled according to Langmuir convention assuming site homogeneity. The pH-dependent Cr(III) adsorption data were quantified by diffused layer model assuming following reaction stoichiometries: $$ \begin{aligned} 2\, {>}{\text{AlOH}}_{{({\text{s}})}} + {\text{ Cr }}\left( {\text{OH}} \right)_{{ 2\,({\text{aq}})}}^{ + } \, \to \, \left( { {>}{\text{AlO}}} \right)_{ 2} {\text{Cr}}_{{({\text{s}})}}^{ + } + {\text{ 2H}}_{ 2} {\text{O}} \quad {\text{log K 15}}. 5 6\\ 2\, {>}{\text{FeOH}}_{{({\text{s}})}} + {\text{ Cr}}\left( {\text{OH}} \right)_{{ 2\,({\text{aq}})}}^{ + } \, \to \, \left( { {>}{\text{FeO}}} \right)_{ 2} {\text{Cr}}_{{({\text{s}})}}^{ + } + {\text{ 2H}}_{ 2} {\text{O}}\quad {\text{log K 5}}.0 8.\\ \end{aligned} $$ The present data showed that NRE can effectively be used to mitigate Cr(III) from aqueous solutions and this method is found to be simple, effective, economical and environmentally benign.

Cr(VI) retention and transport through Fe(III)-coated natural zeolite

Cr(VI) is a group A chemical based on the weight of evidence of carcinogenicity. Its transport and retention in soils and groundwater have been studied extensively. Zeolite is a major component in deposits originated from volcanic ash and tuff after alteration. In this study, zeolite aggregates with the particle size of 1.4–2.4mm were preloaded with Fe(III). The influence of present Fe(III) on Cr(VI) retention by and transport through zeolite was studied under batch and column experiments. The added Fe(III) resulted in an enhanced Cr(VI) retention by the zeolite with a capacity of 82mg/kg. The Cr(VI) adsorption on Fe(III)-zeolite followed a pseudo-second order kinetically and the Freundlich adsorption isotherm thermodynamically. Fitting the column experimental data to HYDRUS-1D resulted in a retardation factor of 3 in comparison to 5 calculated from batch tests at an initial Cr(VI) concentration of 3mg/L. The results from this study showed that enhanced adsorption and retention of Cr(VI) may happen in soils derived from volcanic ash and tuff that contains significant amounts of zeolite with extensive Fe(III) coating.

Geochemical processes and mobilization of toxic metals and metalloids in an As-rich base metal waste pile in Zimapán, Central Mexico

Abstract The geochemistry and mineralogy of samples collected along depth profiles from an As-rich tailing deposit with abundant calcite was studied to determine the processes that influence the mobility of Fe, Zn, Cu, Ni, Cd, As, Sb, Cr and Tl. In spite of their near neutral pH, almost all of them are acid potential generators. Total concentrations decreased as: Fe > As > Zn > Pb > Cu > Sb > Cd > Cr > Ni > Tl. Soluble contents were lower and followed a slightly different order. Mobility decreased as: Tl > Cd, Zn, Cu, Sb, Ni, As > Fe, Pb > Cr. Higher soluble concentrations of Fe, Cu, Zn, As, Pb, and Ni were found in low-pH samples and of Sb and Tl in near-neutral samples. Sulfide oxidation processes are developing in the tailing’s dam. These processes do not have a trend with depth but occur mainly in acid layers. Near neutral layers formed by primary sulfides and calcite probably correspond to wastes produced from the processing of ore coming mainly from pods within the skarn, and acid layers with abundant secondary minerals from material mined from chimneys and mantos. The presence of calcite influences speciation, neutralizes acid mine drainage (AMD), and decreases the mobility of most toxic metals and metalloids (TMMs). However, a hard-pan layer was not observed in the studied profiles. Retention of TMM within tailings probably occurs through the formation of low solubility metal carbonates and from elevation of pH that promotes Fe hydroxides precipitation that may retain As, Sb and metals. Calcite occurrence promotes As, Cd, Cu, Fe, Zn, Pb, Cd and Cr retention, does not play a role on Tl and Ni mobilization, and increases Sb release.

Post-acquisition repetitive thought in fear conditioning: An experimental investigation of the effect of CS-US-rehearsal

Background and objectivesAlthough repetitive thought (e.g., worry) is generally assumed to be a risk factor for psychopathological disorders such as anxiety disorders, the repetitive thought processes occurring after a conditioning event have not yet received much theoretical attention. However, as repetitive thought can be mimicked by (mental) rehearsal, which is well-known to enhance memory performance, it seems worthwhile to explore the role of rehearsal in conditioning. Therefore, the current study investigates the impact of rehearsing an acquired CS-US-contingency on subsequent conditioned fear responding. MethodsAfter acquiring two CS-US-contingencies with either a human scream or a white noise as US, participants were instructed to rehearse one of these CS-US-pairings during an experimental session as well as during the following week. ResultsFear responding to the CS which was previously paired with the scream persisted in the participants who rehearsed the CS-US(scream)-contingency, but decreased in those participants who rehearsed the CS-US(noise)-contingency. The same pattern emerged in the US-expectancy ratings, but the effect failed to reach significance. For the CS which was paired with the noise-US, no rehearsal effect emerged. LimitationsAs acquisition to the noise-US was less pronounced and less robust as compared to the scream-US, claims regarding the rehearsal effect might be hampered for the CS-US(noise)-contingency. ConclusionsRepetitive post-acquisition activation of a CS-US-contingency impacts CR retention. As the USs were not rated as more intense, aversive or startling after rehearsal compared to post-acquisition, US-inflation is discarded as a possible explanation of this effect.

Chemical Speciation of Chromium(III) and (VI) Using Phosphonium Cation Impregnated Polyurethane Foams Prior to Their Spectrometric Determination

Fast and selective sorptions of Cr(VI) species from aqueous media onto tetraphenylphosphonium bromide (TPP(+) · Br(-)) physically immobilized polyurethane foams (PUFs) sorbent were achieved. Based on the Scatchard model of binding sites of the PUFs and Langmuir and Dubinin-Radushkevich (D-R) adsorption models of Cr(VI) retention onto TPP(+) · Br(-) immobilized PUFs, a dual retention mechanism involving absorption related to "weak-base anion ion exchange" and an added component for "surface adsorption" was proposed. Thus, the TPP(+) · Br(-) loaded PUFs were successfully packed in column mode for preconcentration of trace and ultra trace concentrations of Cr(VI) as halochromates [CrO(3)C](-)(aq) from aqueous HCl media. The retained [CrOCl(3)](-)(aq) species were recovered with NaOH (1.0 mol L(-1)) and analyzed by flame atomic absorption spectrometry. Cr(III) species after oxidation to Cr(VI) with H(2)O(2) in aqueous KOH (1.0 mol L(-1)) were also retained and could be recovered by the proposed method. The limits of detection (LOD) and quantification (LOQ) of Cr(VI) were 0.04 and 0.13 µg L(-1), respectively. The chemical speciation of Cr(III, VI) species in various water samples at trace and ultra trace levels were carried out by TPP(+) · Br(-) loaded PUFs packed column. The enhancement factor and sensitivity factor of [CrO(3)C](-)(aq) sorption were 80.0 and 30.0, respectively.

Sequential eluent injection technique as a new approach for the on-line enrichment and speciation of Cr(III) and Cr(VI) species on a single column with FAAS detection

This paper introduces a sequential eluent injection (SEI) technique combined with an on-line preconcentration/separation system for a fast and sensitive FAAS determination of trace amounts of Cr(III) and Cr(VI) species. The method is based on the simultaneous retention of Cr(III) and Cr(VI) on a single mini-column packed with a chloromethylated polystyrene functionalized with N,N-bis(naphthylideneimino)diethylenetriamine (PS-NAPdien) at pH 6.7. The retained chromium species was eluted by sequential injection of HCl for desorption of Cr(III), and NH 3 and NH 4NO 3 buffer solutions for desorption of Cr(VI). All the chemical and flow injection variables were optimized for the quantitative preconcentration and speciation of Cr(III) and Cr(VI). Under the optimum conditions, the calibration graph obtained is linear over the concentration range of 2.0–60.0 μg L −1 for Cr(III), and 8.0–180.0 μg L −1 for Cr(VI). The preconcentration factors for Cr(III) and Cr(VI) were 70 and 30, respectively. The 3 σ detection limits were 0.6 μg L −1 and 2.5 μg L −1 for Cr(III) and Cr(VI), respectively. The relative standard deviations were 2.55% and 0.8%, respectively, for 6 replicate determinations of Cr(III) and Cr(VI) at the 40.0 μg L −1 level. The proposed method was applied for determination of Cr(III) and Cr(VI) in different water samples with satisfactory results.

Multifunctional Nano-Coatings for SOFC Interconnects

Chromium evaporation from metallic interconnects in SOFCs is commonly poisoning the cathode of SOFCs. To reduce chromium evaporation, rather thick coatings have been deposited using various coating techniques. In this study a 22% Cr ferritic steel has been coated with multilayered nano coatings. The best coatings combine a Cr retention layer (800nm Co) with a 10nm layer of Ce that reduces the corrosion rate of the metallic interconnect. Such coatings might be a cost efficient way to meet the required lifetime targets for SOFC interconnects. The Cr evaporation measurements are carried out with a recently developed denuder technique which allows time resolved quantification of volatile chromium species. Downstream of the samples a denuder tube is placed which collects any CrO2(OH)2 evaporating from the samples.

Retention of toxic chromium from aqueous phase by H 3PO 4-activated lignin: Effect of salts and desorption studies

In this study, the feasibility of using H 3PO 4-activated lignin for hexavalent chromium adsorption has been investigated. The composite of activated lignin was characterized using FTIR, XRD and SEM with EDAX analysis. It was observed that the pH had a strong effect on the adsorption capacity; adsorption of Cr(VI) was more favorable at acidic pH with maximum uptake at pH 2. The adsorption equilibrium data were best represented by Koble–Corrigan isotherm. The monolayer sorption capacity obtained from the Langmuir model was found to be 77.85 mg/g. Adsorption showed pseudo-second order rate kinetics and the process involving the rate-controlling step is complex as it involves both film and intraparticle diffusion processes. The NaOH desorbing agent was able to release approximately 84% of metal ions. Thermodynamic parameters showed that the sorption process is exothermic and non-spontaneous. The overall Cr(VI) retention on the activated lignin surface perhaps includes both the physical adsorption of Cr(VI) and the consequent reduction of Cr(VI) to Cr(III).

The immobilization of hydrophilic ionic liquid for Cr(vi) retention and chromium speciation

The immobilization of N-methylimidazolium (Nmim) onto PVC surface forms bonded hydrophilic ionic liquid 1-chlorovinyl-3-methylimidazolium chloride (PVC-NmimCl), which entails anion exchange nature and positively charged surface, facilitating favorable retention of Cr(VI) with a retention capacity of 23.2 mg g−1 for Cr(VI) at pH 5.6. A novel on-line solid phase extraction approach for the separation and preconcentration of Cr(VI) is developed in a sequential injection system with a PVC-NmimCl mini-column, and an extra mini-column of strong acidic styrene type cation exchange resin is incorporated for pre-eliminating Cr(III) in sample solution before entering the PVC-NmimCl mini-column. The retained Cr(VI) is effectively recovered with elution by 0.2 mol l−1 NH4NO3 solution, and the eluate is quantified by electrothermal atomic absorption spectrometry (ETAAS) and inductively coupled plasma mass spectrometry (ICP-MS). With a sample volume of 2000 μl, a complete retention of Cr(VI) is obtained, giving rise to an enrichment factor of 23.4 and a sampling frequency of 9 h−1. A linear range of 0.01–1.0 μg l−1 for Cr(VI), along with a detection limit of 3 ng l−1 and a RSD of 2.9% at 0.5 μg l−1 is obtained. Total chromium in a certified reference material of reverine water (GBW08608) is determined after oxidation, which results in good agreement between the certified and the found values. The procedure is further demonstrated for chromium speciation in tap water and snow water samples.

REMOVAL OF CHROMIUM HEXAVALENT IONS FROM AQUEOUS SOLUTION BY RETENTION ONTO IRON PHOSPHATE

Iron phosphate was synthesized and characterized for the removal of Cr(VI) ions from aqueous solution. Batch type experiments were conducted to study the effects of contact time, pH of the solution, chromium concentration and temperature. The experimental data were analyzed with the adsorption isotherms models of Freundlich, Langmuir and Dubinin Radushkevich (D-R). Results showed that Cr(VI) retention is dependent on pH and temperature. The thermodynamic parameters of the retention system were determined in a temperature interval from 293-323 K. The obtained values of thermodynamic parameters show that the Cr(VI) ions retention on iron phosphate is endothermic and spontaneous type. The results suggest that iron phosphate could be used as an effective adsorbent for the retention of Cr(VI) ions from aqueous solution.

FACTORS AFFECTING RETENTION OF RENNET IN CURD

The residual of calf (CR) and microbial rennet (MR) in curd playing a role in cheese ripening, depending on quantity of residual rennet retained in the curd – The effect of CaCl2, NaCl, pH and rennet concentration on retention of rennet was studies. The results indicated that: 1)-Increasing of CaCl2 concentrations up to 0.05% showed increasing of residual CR and MR in the curd and decreasing for whey except that of CR in the curd from buffaloe’s milk. 2)-Increasing of NaCl concentrations showed a reduction of residual CR and MR in the curd and whey from buffaloe’s and cow’s milk. 3)-Reducing pH of milk showed an increase in retention of CR and MR in the curd from buffaloe’s and cow’s milk, and reduced the retention rennet in the whey from both buffaloe’s and cow’s milk. 4)-Increasing CR and MR concentrations as a percent appeared significant differences in the residual rennet between treatments except curd from cow’s milk. Also the increasing of CR and MR concentrations as a mount of rennet unit showed increasing of residual rennet in the curd and whey from buffaloe’s and cow’s milk.

Retention of Cr(VI) and Pb(II) on a loamy sand soil: Kinetics, equilibria and breakthrough

Illegal discharges are of great concern among industry activities, since they occur under uncontrolled conditions. In most cases, effluents are acidic and the concentrations of heavy metals are very high. With this in mind, the main goal of this study was to evaluate the sorption on a soil of two of the most toxic heavy metals, Cr(VI) and Pb(II), in those conditions. A loamy sand soil was collected in Oporto, Portugal. Batch equilibrium and sorption kinetics were evaluated using both metals solutions, with concentrations ranging from 50 mg L −1 to 200 mg L −1, at pH 2 and 5, between 2 h and 288 h. To evaluate the sorption equilibrium, eight isotherm models were fitted to experimental data. The best adjustments were observed for the Redlich–Peterson and Khan models for the adsorption of chromium ( R 2 = 0.99), and of lead ( R 2 = 0.99), respectively. The sorption kinetics was evaluated using three models – Elovich, pseudo first order and an empirical power function. The retention of lead was almost instantaneous and the empirical power function described better the sorption kinetics of chromium (0.89 < R 2 < 0.99). In addition, flow experiments were performed with effluents of both metals (50 mg L −1) at pH 2 and 5, for about 90 h. Results revealed a high retention of chromium and a weak retention of lead, for low pH values. FTIR analyses to the column samples revealed that clay minerals have an important role in the retention of both metals.

Contribution of T lymphocytes to rat renal ischemia/reperfusion injury

This study aimed to elucidate the early involvement of T lymphocytes in renal ischemia/reperfusion injury. Athymic nude rats (F344/N_Jcl-nu) and control F344/Jcl were subjected to 45 min unilateral renal ischemia. To determine whether the observed differences might be derived from the T lymphocyte presence, T lymphocytes from the spleens of F344/Jcl were injected into F344/N_Jcl-nu via tail vein at the initiation of reperfusion. Immunohistochemical analysis was performed for CD3, the proliferative cell nuclear antigen (PCNA), vimentin, and E-cadherin. T lymphocytes were obtained from the green fluorescent protein transgenic (GFP) rats, and transplanted to F344/N_Jcl-nu 10 min before reperfusion. The animals were euthanized 15 min after reperfusion. F344/N_Jcl-nu showed less retention of both Cr and BUN at 24 and 48 h after reperfusion, compared with F344/Jcl. F344/N_Jcl-nu received T lymphocyte transplantation showed significantly higher retention of both Cr and BUN 24, 48, and 72 h after reperfusion than those without T lymphocyte. A rapid infiltration of T lymphocytes into proximal tubular epithelial cells and tubular lumen was observed using T lymphocytes with green fluorescent protein. In contrast, T lymphocytes were observed with much less frequency 24 h after ischemia. The number of PCNA-positive proximal tubular cells 24 h after the initiation of reperfusion was significantly smaller in the T lymphocyte transplantation group compared with the non-transplantation group. The vimentin positivity and cytoplasmic staining of E-cadherin were also more prominent in the transplantation group. These findings demonstrate a rapid renal T lymphocyte infiltration, which propagate renal functional deterioration.

Flow injection solid phase extraction electrothermal atomic absorption spectrometry for the determination of Cr(VI) by selective separation and preconcentration on a lab-made hybrid mesoporous solid microcolumn

A lab-made hybrid mesoporous solid was employed in a flow injection solid phase extraction electrothermal atomic absorption spectrometric (FI–SPE–ETAAS) system for the selective retention of Cr(VI). The solid was prepared by co-condensation of sodium tetraethylortosilicate and 3-aminopropyltriethoxysilane by sol–gel methodology and one-pot synthesis and characterized by Fourier transform infrared spectroscopy, X ray diffraction spectroscopy, and scanning electronic microscopy. Adsorption capacities at different pH values of both, Cr(VI) and Cr(III), were also measured in order to obtain the optimum retention for Cr(VI) with no interference of Cr(III). The maximum capacity of adsorption (4.35 mmol g − 1) was observed for pH values between 2–3, whilst Cr(III) was found to remain in solution (adsorption capacity = 0.007 mmol g − 1). Then, a microcolumn (bed volume: 7.9 µL) was filled with the solid and inserted in the FI–ETAAS system for analytical purposes. Since the analyte was strongly retained by the filling in the anionic form, 0.1 mol L − 1 hydroxylammonium chloride in 1 mol L − 1 hydrochloric acid was selected as eluent due to its redox characteristics. In this way, the sorbed Cr(VI) was easily released in the cationic form. The enrichment factor (EF) was found as a compromise between sensitivity and sample throughput and a value of 27 was obtained under optimized conditions: pH 2, sample loading 2 mL min − 1 (60 s), elution flow rate 0.5 ml min − 1 (eluent volume: 75 μL). Under optimized conditions the limit of detection for Cr(VI) was 1.2 ng L − 1, the precision, expressed as RSD was 2.5%, the sample throughput 21/h, and the microcolumn lifetime was over 300 adsorption/desorption cycles. Cr(III) determination was also performed by simply measuring its concentration at the end of the column and after Cr(VI) retention by the mesoporous solid. Applications of the methodology to the determination of Cr(VI) in deionized, osmosis, mineral, effluent and river waters showed very good results. Validation was performed by means of recovery studies as no certified materials were available for Cr(VI). Total chromium determinations, obtained by the sum of Cr(III) and Cr(VI) concentrations, were validated using NIST, SRM 1643e certificate reference material (Trace Element in Natural Water).