High Anion Concentrations Research Articles

Mineralogy, Chemical Composition, and Dissolution of Fresh Ash Eruption: New Potential Source of Nutrients

Unusually huge amounts of fresh ashfall from the eruption of the Merapi volcano (occurring October–November 2010) resulted in severe deposition problems (1–29-cm thickness) on many agricultural lands. The objectives of the study were (i) to determine the mineralogy and elemental compositions of the fresh ash, (ii) to assess solvent-extracted cations and the composition of pristine ash leachates in water, and (iii) to anticipate the possibility of using fresh ash as a new source of nutrients. Mineralogical composition was determined by a polarization microscope and total elemental composition by x-ray fluorescence. Dissolved elements were measured from the solid phase (extracted by NH4AOc) and water from river stream flow and canals. Results showed that the mineralogical composition was relatively uniform and dominated by volcanic glass (49% on average) followed by labradorite (26%) and augite (13%), with trace amounts of bytownite, hypersthene, hornblende, and opaque. This indicates that the fresh ash contains mainly easily weatherable minerals. Total element contents consisted of macronutrients in the order of Ca >> Na > K > Mg > P > S and micronutrients of Zn, Fe, Mn, Cu, and Co. Findings from study of pristine ash leachates from river and canal waters, representing natural conditions, clearly demonstrated the high concentrations of base cations (Ca >> Na >> Mg > K) and anions (SO4 >> Cl > NO3 >> PO4). Base cations extracted by NH4OAc were in the order Ca >> Mg > Na > K and the base saturation was >100% (114–484%), confirming that cations in rivers and canals are from soluble salts. The high amounts of ions released from fresh volcanic ash indicated its potential as a source of nutrients.

Lactic Acidosis: A Short Review of Cases

Lactic acidosis, which is caused by a high anion concentration due to metabolic acidosis, occurs when the plasma lactate concentration exceeds 4 to 5 millimoles/litre (mmol/L) (normal range: 0.5-1.5 mmol/L). Lactate accumulation results from increased metabolism or decreased excretion. Lactic acidosis cases often occurs in intensive care units. In order to carry out effective treatment, the primary aim must be the reversal of the causes underlying the disease. Today, various methods are used to treat lactic acidosis. We have reviewed the occurrence of lactic acidosis in two cases in light of the current literature. Lactic acidosis can have quite serious consequences, and clinicians must be very careful while managing patients with lactic acidosis. (Yogun Bakim Derg 2011; 3: 63-6)

Hydrogeochemical characterization and isotope investigations of a carbonate aquifer of the northern part of the United Arab Emirates

This paper assesses a carbonate aquifer of the Wadi Al Bih area in the northeastern part of UAE using hydrogeochemical and isotope approaches. Analyses of groundwater samples showed that the TDS and high concentrations of major cations and anions were encountered in the lower segment of the Wadi Al Bih area. Most of the groundwater salinity was noticed downstream of the wadi and this may be attributed to the brines that underlie the groundwater and also to the over-pumping of groundwater with mostly very low recharge. Nitrate concentrations observed in the groundwater of the study area may be ascribed to the nature of the karastic aquifer, which could lead to the dominance of dissolved oxygen that makes NO 3 - the dominant form of nitrogen. The presence of sulfate in collected groundwater samples is due to the gypsum-bearing mudstone in the lower segment of the Wadi Al Bih carbonate aquifer. Majority of the groundwater samples showed the presence of NaCl, which indicates the possible influence of the underlying brine. The mixing process of brine water and freshwater was noted in the shift from CaHCO 3 facies to Ca–Cl facies. The Piper plot showed a Ca-rich to Na-rich water type shift, which could be explained by a cation exchange process. The oxygen and hydrogen isotope compositions in the groundwater samples suggest that the main source of precipitation is the Mediterranean Sea with some possible effects of the Arabian Sea. A trend of increasing chloride concentration with enrichment of hydrogen isotope compositions suggests that groundwater originated from evaporated raindrops or evaporated surface water. The similarity of oxygen and hydrogen isotope compositions between the Eastern Gravel Plain, Ophiolite, and the northern carbonate aquifers indicates the presence of a common source of recharge.

Palladium and platinum sorption on a thiocarbamoyl‐derivative of chitosan

AbstractImmobilizing thiourea onto chitosan allowed using the polymer for the recovery of platinum groups metals (PGMs) in acidic solutions (up to 1–2M HCl concentrations). At low HCl concentration protonated amine groups may sorb chloroanionic metal species (electrostatic attraction mechanism); however, most of sorption proceeds through chelation on sulfur containing groups (less sensitive to acidic conditions). The bi‐site Langmuir equation was used for fitting sorption isotherms. The sorption of PGMs was weakly affected by the composition of the solution (presence of high concentration of anions and base metals). Maximum sorption capacities for Pd(II) and Pt(IV) ranged between 274 and 330 mg g−1 in 0.25M HCl solutions and decreased to 150–198 mg g−1 in 2M HCl solutions: Pd(II) sorption was systematically higher than Pt(IV) sorption. The pseudo‐second rate equation was used for modeling the uptake kinetics. Agitation speed hardly affected uptake kinetics indicating that external diffusion resistance is not the rate controlling step. Desorption yield higher than 85% were obtained using thiourea in 0.1M HCl solution. The adsorbents could be reused for at least three cycles. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Assessment of the pollution potential of mercury contaminated biosolids

Environmental context. The re-use of biosolids (sewage sludge) is becoming increasingly popular especially for land applications as soil improvers, fertilisers and composts. However, some biosolids are contaminated with toxic heavy metals and mercury is arguably of the highest environmental and public health concern. Studies on mobility, availability and emissions of mercury from biosolids were carried out to assess the biosolids potential for contamination of the environment and to evaluate applicable techniques for a future remediation. Abstract. Biosolids from Melbourne Water’s Western Treatment Plant (WTP) in Australia contain elevated levels of mercury. Consequently, monitoring programs are crucial in order to assess localised impacts to the environment and on humans immediately surrounding the boundaries of the WTP. Dry biosolids were surveyed for Hg, other heavy metals, cations, soluble anions, sulfur and phosphorus. Mercury concentrations were found to vary between 3.5 and 8.4 mg kg–1 Hg, indicating that biosolids from some locations were above the safety level (5 mg kg–1 Hg) for land applications. High concentrations of soluble anions and cations revealed elevated salinity levels. The biosolids with the highest Hg concentration were further studied to assess their potential for Hg remediation. The results obtained by a sequential extraction procedure showed that 59.01% of the total mercury was complexed with organic ligands. In addition, the influence of air temperature, water content and irradiation on the emission of gaseous elemental mercury from biosolids was studied. Light exposure and water addition were the main factors affecting this emission with flux values up to 132 ng m–2 h–1.

Clay dispersion and its relation to surface charge in a paddy soil of the Red River Delta, Vietnam

AbstractDispersion is an important issue for clay leaching in soils. In paddy soils of the Red River Delta (RRD), flooding with fresh water and relatively high leaching rates can accelerate dispersion and the translocation of clay. For the clay fraction of the puddled horizon of a typical paddy soil of the RRD, the effect of various cations and anions as well as humic acid (HA) at different pH values on the surface charge (SC) were quantified and the dispersion properties were determined in test tubes and described by the C50 value.In the <2 µm fraction, dominated by illite, the proportion of 2:1 vs. 1:1 clay minerals is 5:1. The organic‐C content of the clay fraction is 2.2%. Surface charge was found to be highly pH‐dependent. At pH 8 values of –32 and at pH 1 of –8 mmolc kg–1 were obtained. Complete dispersion was observed at pH > 4, where SC is > –18 mmolc kg–1. The flocculation efficiency of Ca strongly depends on the pH. At pH 4, the C50 value is 0.33, 0.66 at pH 5, and 0.90 mmol L–1 at pH 6. At pH 6, close to realistic conditions of paddy soils, the effect of divalent cations on the SC and flocculation decreases in the order: Pb > Cu > Cd > FeII > Zn > Ca > MnII > Mg; FeII was found to have a slightly stronger effect on flocculation than Ca. An increase in concentrations of Ca, MnII, and Mg from 0 to 1 mmol L–1 resulted in a change in SC from –25 to approx. –15 mmolc kg–1. In comparison, the divalent heavy‐metal cations Pb, Cu, Cd, and Zn were found to neutralize the SC more effectively. At a Pb concentration of 1 mmol L–1, the SC is –2 mmolc kg–1. From pH 3 to 5, the dispersion of the clay fraction is facilitated rather by SO$ _4^{2-} $ than by Cl–, which can be explained by the higher affinity of SO$ _4^{2-} $ to the positively charged sites. With an increase of the amount of HA added, the SC continuously shifts to more negative values, and higher concentrations of cations are needed for flocculation. At pH 3, where flocculation is usually observed, the presence of HA at a concentration of 40 mg L–1 resulted in a dispersion of the clay fraction. While high anion concentrations and the presence of HA counteract flocculation by making the SC more negative, FeII and Ca (C50 at pH 6 = 0.8 and 0.9 mmol L–1, respectively) are the main factors for the flocculation of the clay fraction.For FeII and Ca, the most common cations in soil solution, the C50 values were found to be relatively close together at pH 4, 5, and 6, respectively. Depending on the specific mineralogical composition of the clay fraction, SC is a suitable measure for the determination of dispersion properties and for the development of methods to keep clay particles in the soil in the flocculated state.

The influence of mixed anionic composition of Mg–Al hydrotalcites on the thermal decomposition mechanism based on in situ study

A series of Mg/Al hydrotalcites with tailored content of carbonate and nitrate anions was prepared using precipitation method. A part of the obtained materials was additionally crystallized in hydrothermal conditions. Different hydrotalcite phases or domains may co-exist within one sample obtained at controlled conditions. Decomposition mechanism studied in situ (DRIFT, XRD) was different for the samples with high concentration of interlayer nitrate anions than for carbonate-containing sample. TG-QMS study of hydrothermally treated samples provided more precise data for quantitative description of decomposition steps of Mg/Al hydrotalcites containing different mixtures of nitrate and carbonate anions.

Thermodynamic Intermediates of the Alkaline III→IV Transition in Ferricytochrome c Probed by 695 nm Charge Transfer Band

The 695 nm band in the spectrum of the native state (III) of ferricytochrome c has recently been shown to be composed of different sub-bands which reflect different conformational substates (CS) of the functional pivotal Fe-M80 linkage. In order to explore the influence of the alkaline III→IV transition on this CSs we measured and analyzed the absorption and CD profile of this band as a function of pH between pH 7 and 10 at high (50mM) and low anion concentration for horse heart (hh) cytochrome c. Additional measurements on yeast cytochrome c were performed at low anion concentrations. The titration curves of the two dominating sub-bands are clearly biphasic at low anion concentrations and reflect effective pK-values of 8.5 and 9.65. On the contrary, the titrations curves obtained at high anion concentrations are monophasic; the effective pK being 9.23. The thermodynamic parameters (i.e. pK and the Hill coefficient as a measure of cooperativity) are slightly different for the two CSs. We fitted the data obtained at low anion concentration with a model, which assigns the two effective pK-values to two different alkaline states IV1 and IV2, in which M80 is replaced by K73 and K79, respectively. This model did not reproduce our data well in contrast to an alternative model which assumes only one species with two protonation sites. This suggests that the state populated upon the pK= 8.5 protonation can be interpreted as a thermodynamic intermediate of the III→IV transition. This notion is consistent with our observation, that the 695 nm titration curves of the y-cytochrome c mutants K79R and K73V are still mostly biphasic at low ionic strength.

Insights into Cytochrome c−Cardiolipin Interaction. Role Played by Ionic Strength

The finding that cytochrome c (cyt c) plays a role in programmed cell death after its release from the mitochondrion has recently renewed interest in this protein. The structural changes in cytochrome c observed at early stages of the apoptotic process have been related to changes occurring in the protein when it forms a complex with phospholipid vesicles. Among the lipids constituting the membrane, cardiolipin is the one thought to bind to cyt c. In this paper, we have investigated the influence exerted by ionic strength on cytochrome c-cardiolipin interaction and found that formation of the cytochrome c-cardiolipin complex occurs via two distinct transitions, implying a high-affinity site and a low-affinity site. Ionic strength significantly influences complex stability; sodium chloride dissociates the complex through two distinct transitions, the second of which occurs at a very high anion concentration. ATP also dissociates the complex, but under the conditions that were investigated, its action is limited to the high-affinity site. The dissociation process is characterized by a very slow kinetic rate constant ( k obs = 4.2 x 10 (-3) s (-1)) and requires several minutes to be completed. We ascribe it to the high activation barrier met by the protein when restoring the native Fe(III)-M80 axial bond. The peroxidase activity shown by cardiolipin-bound cytochrome c is indicative of a less packed protein tertiary conformation in the complex. In line with earlier reports, these data highlight the manifold functions of cytochrome c besides the well-known role it plays in oxidative phosphorylation, shedding more light on the properties of the cytochrome c-cardiolipin complex, involved in the progression of early stages of apoptosis.

Ruthenium(II) 2,2′-Bibenzimidazole Complex as a Second-Sphere Receptor for Anions Interaction and Colorimeter

A ruthenium(II) complex [Ru(bpy) 2(H 2bbim)](PF 6) 2 ( 1) as anions receptor has been exploited, where Ru(II)-bpy moiety acts as a chromophore and the H 2bbim ligand as an anion binding site. A systematic study suggests that 1 interacts with the Cl (-), Br (-), I (-), NO 3 (-), HSO 4 (-), and H 2PO 4 (-) anions via the formation of hydrogen bonds. Whereas 1 undergoes a stepwise process with the addition of F (-) and OAc (-) anions: formation of the monodeprotonated complex [Ru(bpy) 2(Hbbim)] with a low anion concentration, followed by the double-deprotonated complex [Ru(bpy) 2(bbim)], in the presence of a high anion concentration. These stepwise processes concomitant with the changes of vivid colors from yellow to orange brown and then to violet can be used for probing the F (-) and OAc (-) anions by naked eye. The deprotonation processes are not only determined by the basicity of the anion but also related to the strength of hydrogen bonding, as well as the stability of the formed compounds. Moreover, a double-deprotonated complex [Ru(bpy) 2(bbim)].CH 3OH.H 2O ( 3) has been synthesized, and the structural changes induced by the deprotonation has also been investigated. In addition, complexes [Ru(bpy) 2(Hbbim)] 2(HOAc) 3Cl 2.12H 2O ( 2), [Ru(bpy) 2(Hbbim)](HCCl 3CO 2)(CCl 3CO 2).2H 2O ( 4), and [Ru(bpy) 2(H 2bbim)](CF 3CO 2) 2.4H 2O ( 5) have been synthesized to observe the second sphere coordination between the Ru(II)-H 2bbim moiety and carboxylate groups via hydrogen bonds in the solid state.

Equilibrium-based approach for prediction of matrix-related interferences in anion chromatography

The retention behavior of low-concentration inorganic anions was studied systematically as a function of changing high matrix anion concentration. Stoichiometric retention model was developed for interpretation and prediction of matrix effects in ion chromatography. The model was tested and utilized for separation of low concentration (1–5 mg/l) bromate, bromide, chloride, nitrate, ethanesulfonate, and pentanesulfonate ions with carbonate buffer and hydroxide eluent in relatively wide ranges of sulfate matrix ( > 2000 mg/l). Equilibrium-based approach effectively characterizes the selectivity of the complex system through differences in ion-exchange constants of analyte, eluent and matrix ions. Selectivity data were determined from the experimental retention data by iterative calculations using the derived equations. The predicted and observed retention data are in rather good agreement. The method describes precisely the retention shift of trace anions in the high level of ionic matrices. The results in quantitative three-dimensional retention surfaces ( k, matrix and eluent concentration) together with species distribution graphs are also presented.

Biomass, growth, and diet of fish in forest lakes affected by alkaline mining water in NW Russia

Waste water from the mining industry has altered the water chemistry of naturally oligotrophic lakes in the Kostomuksha area of NW Russia, resulting in high alkalinity and high concentrations of certain anions. Two such lakes, Poppalijarvi and Kento, and one reference lake, Upper Kuito, were sampled for fish using multimesh gillnets in three successive years, 2000-2002. The total CPUE (g gillnet -1 night -1 ) was 2.5 times higher in the affected lakes than in the reference lake. Perch and roach, the predominant species, grew well in all the lakes presumably due to an abundant supply of high quality macroinvertebrate food in their benthic habitats. The proportion of large piscivorous perch was notably high, especially in Lake Kento, probably as a result of low fishing pressure and the abundance of fish prey. Although detailed studies have revealed differences in the structure and function of fish gills and liver between the affected lakes and the reference lake, the environment in Lake Poppalijarvi and Lake Kento enables fast growth of the fish and promotes the existence of a high fish biomass.

Hyperchloremia is the dominant cause of metabolic acidosis in the postresuscitation phase of pediatric meningococcal sepsis*

Metabolic acidosis is common in septic shock, yet few data exist on its etiological temporal profile during resuscitation; this is partly due to limitations in bedside monitoring tools (base excess, anion gap). Accurate identification of the type of acidosis is vital, as many therapies used in resuscitation can themselves produce metabolic acidosis. Retrospective, cohort study. Multidisciplinary pediatric intensive care unit with 20 beds. A total of 81 children with meningococcal septic shock. None. Acid-base data were collected retrospectively on 81 children with meningococcal septic shock (mortality, 7.4%) for the 48 hrs after presentation to the hospital. Base excess was partitioned using abridged Stewart equations, thereby quantifying the three predominant influences on acid-base balance: sodium chloride, albumin, and unmeasured anions (including lactate). Metabolic acidosis was common at presentation (mean base excess, -9.7 mmol/L) and persisted for 48 hrs. However, the pathophysiology changed dramatically from one of unmeasured anions at admission (mean unmeasured anion base excess, -9.2 mmol/L) to predominant hyperchloremia by 8-12 hrs (mean sodium-chloride base excess, -10.0 mmol/L). Development of hyperchloremic acidosis was associated with the amount of chloride received during intravenous fluid resuscitation (r = .44), with the base excess changing, on average, by -0.4 mmol/L for each millimole per kilogram of chloride administered. Hyperchloremic acidosis resolved faster in patients who 1) manifested larger (more negative) sodium chloride-partitioned base excess, 2) maintained a greater urine output, and 3) received furosemide; and slower in those with high blood concentrations of unmeasured anions (all, p < .05). Hyperchloremic acidosis is common and substantial after resuscitation for meningococcal septic shock. Recognition of this entity may prevent unnecessary and potentially harmful prolonged resuscitation.

Features of pulmonary haemodynamics and endothelium function in children with asthma

Asthma patients (n = 79, 7 to 17 years of age) were divided into 3 groups according to asthma severity: mild (n = 23), moderate (n = 24), and severe asthma (n = 32). Asthma was diagnosed according to GINA (2002). Echocardiography, ultrasound evaluation of endothelium vasomotor function and measurement of nitrite anion concentration in exhaled breathe condensate (EBC) were performed in the all patients. Right ventricle dilatation and increase in the total pulmonary vascular resistance were revealed only in patients with severe asthma compared to the control group. Increase in pulmonary artery systolic pressure was significantly higher in the severe asthma patients compared both to the control group and mild asthma patients. Increased right ventricle pressure was accompanied by endothelium dysfunction in 48.1 % (38 patients). High EBC nitrite anion concentration (12.11 ± 1.72 μmol/L) was revealed in asthmatic children compared to control group (3,34 ± 1,58 μmol/L). The results suggest that childhood asthma is associated with morphological and functional abnormalities of pulmonary hemodynamics and endothelium function depending on severity of the disease.

Probing Receptor–Anion Interactions by Ratiometric Chemosensors Containing Pyrrolecarboxamide Interacting Sites

AbstractWe have designed and synthesized a series of molecular probes integrating both an amide and a pyrrole functionality for anion‐recognition and ‐sensing. The interactions between these probe molecules and various anions have been investigated to elucidate the influence of electronic effects on the anion‐recognition site. Changes in the UV/Vis and fluorescence spectra in the presence of anions reveal that probes 1–5 typically display a strong response to cyanide. Moreover, the appearance of the ratiometric phenomenon upon interaction with anions further enhances spectral differentiation for anion‐sensing. The mechanism for the reaction between the probe molecules and the anions has been further explored by 1H NMR titration experiments. Anions strongly interacting with probes and producing large changes in the UV/Vis and fluorescence spectra during the titration usually result in deprotonation of the amide group, whereas weakly interacting anions initially form hydrogen bonds with amide and pyrrole NH groups followed by deprotonation at higher anion concentrations. The weakest anions, however, form only two or four hydrogen bonds with the amide and pyrrole N–H groups during the titrations. Moreover, both probes 2 and 3 are able to recognize cyanide in a semi‐aqueous environment with extremely high selectivity. The formation of covalently bonded cyanohydrin derivatives from cyanide addition to an electron‐deficient amide carbonyl center is attributed to the effectiveness of probes 2 and 3 in a semi‐aqueous environment.(© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2007)

MgO(111) Nanosheets with Unusual Surface Activity

MgO(111) nanosheets can be prepared via a facile wet chemical process. The MgO(111) nanosheets possessing the exposed (111) plane as a main surface have a thickness typically between 3 and 5 nm. Study of MgO(111) nanosheets by in situ diffuse reflectance Fourier transform (DRIFT) spectroscopy suggests that hydroxyl groups, oxygen vacancies, and surface oxygen anions exist on the surface and the (111) surface may be stabilized by hydroxyl groups. DRIFTS and temperature-programmed desorption (TPD) studies of CO2 adsorption reveal that there are large amounts of medium basic sites which can be attributed to the high concentration of surface O2- Lewis basic sites. DRIFTS and temperature-programmed reaction studies (TPRS) of methanol have demonstrated that, in contrast to commercial MgO, MgO(111) nanosheets are highly reactive toward the decomposition of methanol. Methanol can be decomposed and the surface CO species formed can be oxidized readily at low temperature by the high concentration of oxygen anions o...

Electrochemical synthesis of ferrate using boron doped diamond anodes

This work is focussed on the electrosynthesis of ferrates using boron doped diamond (BDD) anodes. Results show that this type of electrodes leads to efficient processes only limited by the availability of oxidizable-iron species. The hydroxyl ion concentration, the current density and the iron raw material were found to influence greatly on the results. Thus, the efficiencies of the process were increased using high current densities and high concentration of hydroxyl anions. Likewise, the use of an iron-powder bed (not directly on the surface of the diamond but separated by means of a very thin plastic mesh) as a raw material allows obtaining higher ferrates concentration than the use of solutions saturated with iron hydroxide.

Arsenate removal by zero valent iron: Batch and column tests

This study investigates the efficiency of zero valent iron (ZVI) to remove arsenate from water. Batch experiments were carried out to study the removal kinetics of arsenate under different pH values and in the presence of low and high concentrations of various anions (chloride, carbonate, nitrate, phosphate, sulphate and borate), manganese and dissolved organic matter. Borate and organic matter, particularly at higher concentrations, inhibited the removal of arsenic. Column tests were carried out to investigate the removal of arsenate from tap water under dynamic conditions. The concentrations of arsenic and iron as well as the pH and Eh were measured in treated water. Efficient removal of arsenate was observed resulting at concentrations below the limit of 10 μg/L in treated waters.

Organic and minerogenic acidity in Finnish rivers in relation to land use and deposition

The role of organic and minerogenic acidity in controlling pH levels in Finnish rivers was studied by measuring total organic carbon (TOC) and non-marine sulphate (*SO(4)) concentrations in river water of the main river basins and their sub-basins. The basins are located along a latitudinal gradient (60 degrees N to 69 degrees N) and cover 297,322 km(2), 88% of the total area of Finland. The basins are predominately covered by coniferous forests and peatlands, and are located in areas with low sulphate deposition (80-430 mg S m(-2) a(-1)). The proportion of the basin covered by forests on mineral soils ranges from 29 to 64% and the proportion of peatlands from 3 to 60%. The percentage of peatland is highest in northern Finland (28-60%), whereas the proportion of forests on mineral soils increases towards the south. The majority of the agricultural land is located in southern and western Finland. *SO(4) concentrations were positively correlated with the proportion of agricultural land in the basin. Moreover, the percentage of peatlands had a positive correlation with the concentrations of TOC and organic anion. High peatland proportion and high TOC and organic anion concentrations decreased pH values in the river water, whereas no correlation between *SO(4) concentrations and pH was observed. The average organic anion concentration exceeded the average *SO(4) concentration in river water in 17 basins out of the 86 studied basins. The organic anion-dominated areas were situated in northern basins, reflecting the high extent of peatlands in these areas. *SO(4) dominated in southern Finland and in western coastal areas, where the extent of agricultural land, acid sulphate soils and the deposition of sulphate is highest.

Functionalities of a Nanoporous Crystal 12CaO·7Al2O3 Originating from the Incorporation of Active Anions

Abstract A cage structure formed in a positively charged lattice framework of 12CaO·7Al2O3 (C12A7) is utilized to incorporate and release chemically unstable anions, imparting chemical and electronic activities to this material. High concentrations of oxygen radical anions, i.e. O− and O2−, are formed efficiently in these cages under a high oxygen activity condition. The O− ion, which is the strongest oxidant among all the reactive oxygen species, can be extracted from the cages into an external vacuum by applying an electric field with thermal assistance. In contrast, hydrogen-reduction processes allow the formation of hydride (H−) ions in the cage. H− ion-incorporated C12A7 exhibits a persistent insulator–conductor conversion upon irradiation with ultraviolet-light or electron-beam. The irradiation-induced conversion mechanism and electronic transport characteristics are discussed on the basis of experimental evidence and first-principle theoretical calculations. Electrons released from the H− ions are trapped by the cages and subsequent inter-cage hopping of the electrons is responsible for the electrical conduction. Furthermore, a severe reducing environment enables us to substitute electrons almost completely for anions in the cages, forming a stable inorganic electride. Finally, the formation of these active anions in this material is examined in terms of electronic structures, thermodynamics, and structural features of the cage.