Sodium Carbonate Salts Research Articles

Ocean alkalinity enhancement using sodium carbonate salts does not lead to measurable changes in Fe dynamics in a mesocosm experiment

Abstract. The addition of carbonate minerals to seawater through an artificial ocean alkalinity enhancement (OAE) process increases the concentrations of hydroxide, bicarbonate, and carbonate ions. This leads to changes in the pH and the buffering capacity of the seawater. Consequently, OAE could have relevant effects on marine organisms and in the speciation and concentration of trace metals that are essential for their physiology. During September and October 2021, a mesocosm experiment was carried out in the coastal waters of Gran Canaria (Spain), consisting on the controlled variation of total alkalinity (TA). Different concentrations of carbonate salts (NaHCO3 and Na2CO3) previously homogenized were added to each mesocosm to achieve an alkalinity gradient between Δ0 to Δ2400 µmol L−1. The lowest point of the gradient was 2400 µmol kg−1, being the natural alkalinity of the medium, and the highest point was 4800 µmol kg−1. Iron (Fe) speciation was monitored during this experiment to analyse total dissolved iron (TdFe, unfiltered samples), dissolved iron (dFe, filtered through a 0.2 µm pore size filter), soluble iron (sFe, filtered through a 0.02 µm pore size filter), dissolved labile iron (dFe′), iron-binding ligands (LFe), and their conditional stability constants (KFeL′) because of change due to OAE and the experimental conditions in each mesocosm. Observed iron concentrations were within the expected range for coastal waters, with no significant increases due to OAE. However, there were variations in Fe size fractionation during the experiment. This could potentially be due to chemical changes caused by OAE, but such an effect is masked by the stronger biological interactions. In terms of size fractionation, sFe was below 1.0 nmol L−1, dFe concentrations were within 0.5–4.0 nmol L−1, and TdFe was within 1.5–7.5 nmol L−1. Our results show that over 99 % of Fe was complexed, mainly by L1 and L2 ligands with kFe′L′ ranging between 10.92 ± 0.11 and 12.68 ± 0.32, with LFe ranging from 1.51 ± 0.18 to 12.3 ± 1.8 nmol L−1. Our data on iron size fractionation, concentration, and iron-binding ligands substantiate that the introduction of sodium salts in this mesocosm experiment did not modify iron dynamics. As a consequence, phytoplankton remained unaffected by alterations in this crucial element.

Damage of porous building stone by sodium carbonate crystallization and the effect of crystallization modifiers

Salt crystallization is an aggressive weathering mechanism affecting porous building materials. The extensive use of Portland cement, a source of alkalis, in modern buildings and restoration interventions makes sodium carbonate salts important weathering agents. Herein, we study salt damage to a porous stone commonly used in the Andalusian built heritage (Santa Pudia limestone) due to stress generation associated with the precipitation of natron (Na2CO3·10 H2O). We performed cyclic crystallization tests combined with thermodynamic and poromechanical calculations to determine salt crystallization pressure and effective tensile stress suffered by the material. The outcome reveals that in-pore natron crystallization during cooling/evaporation generates stresses exceeding the tensile strength of the wet substrate, leading to extensive damage by fracturing and material loss. Damage is reduced using aminotris(methylenephosphonic) acid (ATMP), a common phosphonate-based crystallization modifier that induces non-damaging efflorescence growth as opposed to damaging subflorescence growth, which takes place in its absence.

Soil dynamics modulation of stress enzymes and secondary metabolites in allium cepa (L.) under salinity stress

In Allium cepa (L.) cultivation, salinity stress is the most important environmental factor worldwide that affects plant growth, protection as well as yield stability. The present study was carried out to examine the alterations in soil dynamics, antioxidants, biochemical and secondary metabolic profile of A. cepa under alkaline stress. Various parameters of A. cepa were studied under salinity stress by exposing them to different concentrations of sodium carbonate (SC) and sodium bicarbonate (SBC) salts (0, 10 and 100 mM). Treatment of both SC and SBC in A. cepa increases superoxide dismutase, glutathione peroxidase and catalase concentrations. These were attributed to increase in peroxide, lipid peroxides as well as carbonyl groups. The salinity stress was driven by the alterations in the soil dynamics. Of note, the salt stress induces secondary metabolites changes in A. cepa. The compounds like phenol 2 4-bis (1 1-dimethylethyl), hexadecane, 7,9-di‑tert‑butyl‑1-oxaspiro(4,5) deca-6,9-diene-2,8‑dione, 1,2-benzenedicarboxylic acid, butyl octyl ester, 1,2-benzenedicarboxylic acid, diisooctyl ester are elevated. In addition, the level of total proteins is reduced in all the groups except 10 mM and Proline amino acid in the shoot is elevated. Reversing all the parameters tested to achieve control levels in A. cepa indicates that significant cellular mechanism appeared in stress condition that brings back the altered parameters to normal levels. The biochemical and secondary metabolite profile analysis of the petroleum ether extracts of A. cepa under various alkaline stress conditions reveals that the composition of secondary metabolites and their concentration in A. cepa varies depending on the extent of alkaline stress.

Dyeing of soybean protein/flax blended yarns with reactive dyes and subsequent dye-fixation

The dyeing process of soybean protein/flax blended yarns with reactive dyes (containing monofunctional or bifunctional groups) and the method of improving the color fastness of dyed yarns treated with an ecofriendly formaldehyde-free fixing agent were studied. Influence factors such as sodium carbonate concentration, salt concentration, fixation time and temperature were analyzed, the optimum processes to soybean protein/flax blended yarns dyed with the two reactive dyes were determined: the soybean protein/flax blended yarns were dyed with Reactive Yellow K-R at a bath to material ratio of 20:1, dye concentration 2% owf., sodium chloride 40 g/L, sodium carbonate 10 g/L, fixed at 85 °C for 30 min; and dyed with Reactive Yellow B-4RFN at a bath to material ratio of 20:1, dye concentration 2% owf., sodium chloride 50 g/L, sodium carbonate 15 g/L, fixed at 70 °C for 50 min. The application processes of formaldehyde-free fixing agent DM-2158 were also determined. Performance test results indicated that both K-type and B-type reactive dyes had good colorfastness to washing and rubbing, and B-type reactive dyes showed a higher fixing effect than K-type reactive dyes. The application of a formaldehyde-free fixing agent to dyed products improved the colorfastness to washing and rubbing, especially for blended yarns dyed with K-type reactive dyes.

Production and characterisation of sodium and potassium carbonate salts from carbonation alkaline aluminate liquor

ABSTRACT The polythermal crystallization method has been used to extract sodium and potassium carbonate salts as valuable by-products. The salt production was carried out using an alkaline carbonate solution from the Azarshar nepheline syenite pilot plant in Iran. The optimum conditions were obtained by comparison between the results of thermodynamic modelling and experiments. To better understand the properties of the carbonate salts, thermal analysis, chemical analysis, and X-ray diffraction methods were also utilised. The optimum density and temperature for sodium carbonate crystallization were found to be 1.50 g/cm3 and 115–120°C, respectively, and for hydrated potassium carbonate crystallization to be 1.68 g/cm3 and 130°C at the first stage, and 1.70 g/cm3 and 135°C at the second stage, respectively. The thermodynamic modelling showed good agreement with experimental data for the carbonate salts.

Effect of mechanical activation on extraction of vanadium from chromium-containing vanadate solution by calcification and carbonization

The effect of mechanical activation on extraction of vanadium from chromium-containing vanadate solution by precipitation with calcium salt and leaching with sodium carbonate salt was investigated. The whole process including selective precipitation of vanadium, alkali leaching of vanadium and cyclic utilization of calcium. Compared with stirring, ball milling is more effective for vanadium precipitation under the same experiment conditions. This is because the calcium vanadate formed on the surface of Ca(OH)2 can be peeled off by mechanical activation, which can also be confirmed by SEM image, EDS spectra and XRD patterns of the precipitation. The effect of temperature ranging from 20 °C to 50 °C on vanadium leaching efficiency was studied with the other reaction conditions fixed as stirring speed of 400 r/min, NaHCO3/V molar ratio of 2.80, L/S ratio of 4:1 ml/g. It is observed that vanadium leaching efficiency exceeding 99% was obtained after only 6 min of reaction as well as leaching temperature had little influence on vanadium leaching efficiency. After filtration, the leach solution was used to prepare crystals of NH4VO3 and the leach residue was calcined to obtain CaO. The precipitation efficiency of V was 99.34% by adding CaO into chromium-containing vanadate solution according to Ca/V molar ratio 1.80 and ball milling for 90 min with 140 rpm at room temperature. Mechanical activation can not only increase the vanadium precipitation efficiency and improve the leaching performance of the precipitate, but also to realize the cyclic utilization of calcium salt and crystallization solution.

Metastable Equilibria of the Quinary System NaCl + Na2CO3 + Na2B4O7 + KCl + K2CO3 + K2B4O7 + H2O at 273.15 K

The metastable phase equilibria of the quinary system NaCl + Na2CO3 + Na2B4O7 + KCl + K2CO3 + K2B4O7 + H2O were studied at 273.15 K using an isothermal evaporation method. The solubilities and densities of the equilibrated solution in this system were determined. On the basis of the experimental data, the stereo metastable phase diagram and the projected phase diagram saturated with the salt Na2B4O7 of the quinary system at 273.15 K were constructed. In the space diagram there are seven crystallization fields corresponding to the crystalline phase regions of KCl, NaCl, K2B4O7·4H2O, Na2B4O7·10H2O, Na2CO3·10H2O, K2CO3·3/2H2O, and K2CO3·Na2CO3·12H2O. The projected phase diagram saturated with sodium borate consists of five crystallization fields, seven univariant curves, and three invariant points. The five crystallization fields correspond to NaCl, KCl, K2B4O7·4H2O, Na2CO3·10H2O, and K2CO3·Na2CO3·12H2O. The forms of sodium and potassium borate are Na2B4O5(OH)4·8H2O and K2B4O5(OH)4·2H2O, respectively. The forms of potassium carbonate, sodium carbonate, and double salt are K2CO3·3/2H2O, Na2CO3·10H2O, and K2CO3·Na2CO3·12H2O; comparing with the phase diagram of the subsystems containing sodium carbonate and potassium carbonate, they have the same crystallization forms.

Chemical characterization of red cells from the black sea urchin Arbacia lixula by X-ray photoelectron spectroscopy.

Red spherula cells (RSC) from sea urchin coelomic fluid have attracted great interest for their specific and intriguing properties, such as for example antimicrobial activities and immune response, that probably tie in with their red characteristic pigments. Although to date different studies have been reported aimed to chemically characterize their pigments extracted from the cells, few data are available about the chemical characterization of the cell surface. In this work, a systematic chemical characterization of the RSC surface by X-ray photoelectron spectroscopy (XPS) analysis is described. The results were compared with data on colorless cells from the same coelomic fluid sample. Our observations evidenced that the two cell types were characterized by the presence of different chemical functional groups. In particular, the colorless cells are dominated by the presence of alkyl, alcohol, amide, and carboxyl groups in accordance with other similar cell types, enriched in Na+ and Cl− ions. Traces of elements like S (sulphonates) and P (phosphates) are also present. On the other hand, the RSC in addition to the alkyl groups show a reduction in the content of amide groups, accompanied by the anomalous presence of keto-enolic groups that probably can be associated with the presence of quinones/hydro-quinones from red pigments. A chemical enrichment in elements such as Cl− and Mg2+ and sulphate groups (–R–O–SO3−), as well as the presence of sulphides and phosphates traces, is evident. The absence of carbonate groups is also observed in both cell populations, confirming the absence of sodium and magnesium carbonate salts. No traces of toxic elements (i.e., heavy metals) have been revealed.

Green synthesis of iron oxide nanoparticles using Cymbopogon citratus extract and sodium carbonate salt: Nanotoxicological considerations for potential environmental applications

Synthesis of functional and biocompatible nanomaterials, based on the green chemistry paradigm, aims to innovate by using environmentally friendly techniques. Green synthesis using natural extracts instead of chemicals is proving to be an efficient route to prepare metal and metal oxide nanoparticles. In this study, the green synthesis of iron oxide nanoparticles (FeO-NPs) is reported, using a Cymbopogon citratus (C. citratus) extract and sodium carbonate as the reducing and pH stabilizer agents, respectively. FeO-NPs are extensively studied and applied due to the exceptional physicochemical properties, outstanding the superparamagnetism, and the large surface area. These properties are corroborated using different characterization techniques, in which a regular crystal structure and the magnetic response are similar compared with FeO-NPs synthesized via the traditional methods. The presence of magnetite and maghemite (Fe3O4 and γ-Fe2O3) phases are evidenced. A major composition of Fe3O4 allows predominant superparamagnetism. However, surface functionalization reduces the spin coordination avoiding a high saturation magnetization. The presence of phytochemical content in the C. citratus allows the reduction of iron(III) to iron(II) using H+ radicals produced from hydroxyl and carbonyl groups, and the in-situ functionalization using these groups. Additionally, the biocompatibility of the FeO-NPs is evaluated performing a nanotoxicological assessment, in which Caenorhabditis elegans nematodes are used as the biological model. The presence of organic molecules on FeO-NPs promotes no toxicity and low effects on the locomotion, growth, and reproduction, suggesting a low risk using these functional nanoparticles for environmental applications, and outstanding the synthesis route with a green approach.

Evaluation of sodium salt scaling in black liquor evaporators using existing process data

Abstract Scaling caused by sodium carbonate and sodium sulphate salts is a common problem during black liquor evaporation and mills currently have no proper tools to monitor or follow it up. The method proposed enables automatic evaluation of scaling rates and behaviours, together with washing performance, by using measurements that are already available at most mills, such as the boiling point elevation and the overall heat transfer coefficient. The method identified the scaling correctly in most cases, normally >90 %, although fast and sudden scaling proved to be challenging; its performance was also dependent on the quality of the data used. Historical data from three mills was evaluated and it was found that the scaling rate generally increased at higher concentrations of black liquor: one of the mills had almost no scaling below 70 % dry solids content. Another mill, however, deviated from this trend and had significant problems with fast and sudden scaling in one effect at around 60 % dry solids content. The correlation of process parameters revealed that this scaling was triggered, to a large extent, by the absence of tall oil brine, which is a side stream from the production of tall oil that is normally fed to the evaporators.

Evaluation of Self-Healing in Concrete by Means of Analytical Techniques

In the present work, the self-healing process in concrete was evaluated using analytical techniques. For this purpose, two concrete mixes of different composition (one used as control) were prepared with a water-to-binder ratio of 0.45. The self-healing process was triggered by the introduction in the concrete mix of a commercial expansive admixture (calcium sulfo-aluminate), two dicarboxylic acids, and sodium carbonate salt. After 28 days curing in water, the specimens were artificially cracked (crack width ≤ 900 μm) and then again water-cured for further 60 days until self-healing occurred. The progress of self-healing was investigated with a stereomicroscope at 40, 50, and 60 days, after cracking, to identify the quality and the degree of the healing. The efficiency of the self-healing process was also evaluated using micro-Raman spectroscopy and X-ray micro-computed tomography. Significant reduction in the crack width was observed as a result of a calcite filling, generated during the self-healing process. In some cases (crack width < 400 μm), the crack was completely healed. The experimental methodology used provided new insights into the evolution of the self-healing phenomenon in concrete.

RESEARCH OF THE PROCESS OF DEFORMATION OF EXTRACTIONAL PHOSPHORIC ACID FROM PHOSPHORITES OF CENTRAL KYZYLKUM

The purpose of this research was to determine the optimal technological parameters for the purification of extraction phosphoric acid based on phosphorites of Central Kyzylkum from fluorine by precipitation with sodium salts. The influence of the norm of sodium silicate and the total norm of sodium carbonate and sodium metasilicate salts on the chemical composition and degree of precipitation of sodium silicofluoride was research. It is shown that the optimal norm of sodium metasilicate is the stoichiometric norm for binding fluorine present in the extraction phosphoric acid to silicofluoride and the total norm of sodium salts is 120-140%, the temperature is 70°C. Separation of the liquid and solid phases by settling is preferably carried out at a temperature of 30°C and a process duration of 120 minutes.

Effects of Sodium Carbonate on Striga hermonthica Del. Infestation and Agro-morphological Parameters of Sorghum bicolor (L.) Moench in the Sudano-Sahelian Zone of Cameroun

Sorghum bicolor is the main food widely used to feed millions of people in Central and West Africa. Sorghum production in Sub-Saharan Africa is limited by biotic factors including the parasitic witchweed Striga hermonthica. In Northern Cameroon chemical and organic fertilizers, biological methods and cultivation practices were used by farmers to control Striga hermonthica in field. Some farmers spread sodium carbonate salt (locally named natron or kilbou) in high rates in fields to reduce parasite infestation but in high rate. This salt plays an important role in soil pH buffering. This study was conducted to evaluate effects of different rates of natron on striga emergence and on agro-morphological parameters of sorghum using a susceptible genotype GD-MP04. Field experiments have been conducted from 2017 to 2018 at Touboro, Mayo-Rey Division in the North Region located between longitude 13°34’; 12°07’ East and latitude 7°21’; 15°01’North. The experimental design was a complete randomized bloc with pots (11 m × 11 m) filled with soil naturally infected by striga seeds and different rates of sodium carbonate (0 g, 2 g, 4 g, 6 g, 8 g, 10 g and 12 g per 5 dm3 of soil) were employed. The numbers of emerged striga and sorghum parameters were evaluated. Results showed that striga-infestation and agro-morphological parameters of sorghum varied significantly (p <0.05) with rates of sodium carbonate. The mean number of emerged striga plants per pot varied from 0.08 in pot of 2 g of salt to 5.4 in the control. The number of sorghum leaves per plant, stem diameter, sorghum height, panicle weight and sorghum kernel yield varied significantly (p <0.05) with natron application rate. The application of 2 g of sodium carbonate per pot was the optimal rate to control Striga hermonthica and improve the main agro-morphological parameters of sorghum with 78.27% increase in g of kernel yield and simultaneously inhibited striga infestation by 98.62%. Application of 2 g of sodium carbonate in area naturally infested by striga for improving sorghum yield is required.

Online Novel Techniques for Selective Simultaneous Determination of Alkalinity/Bicarbonate and Hardness in Drinking Water by Skalar San++ Segmented Flow Analysis.

The procedures of the current novel automated technique for the determination of hardness, Carbonate, bicarbonate and alkalinity in drinking water have been modified from both classical batch titration and the method of the flow analysis Skalar San++ method (classical scalar current). The forms of standards in the current methods have been modified. The calcium chloride used previously in the current method for the determination of both calcium and total hardness was replaced by a mixed standard that contains calcium and magnesium carbonate in an aqueous solution. Likewise, calcium carbonate and sodium bicarbonate standards currently used in determination of alkalinity and bicarbonate respectively were replaced by using only one standard of calcium, sodium carbonate salt, and the required bicarbonate concentrations were derived from the same calcium carbonate formula mathematically in the stoichiometry equation. The new approach method was validated and applied successfully for analysis of drinking water and proficiency tests samples (PTS).The technique is used for an automatic online analysis of total, calcium hardness, total alkalinity and bicarbonate in drinking water covering a range of 10 - 100 ppm for total hardness and calcium hardness and a range of 5-100 ppm for alkalinity and bicarbonate mg/L as CaCO3. The method gave a distinct merit over the manual titration method and the current skalar method, with enhanced detection limit, high precision (RSD) which was found to be less than 1%) and accuracy of ( ± 1-2%), as well as a high spectral peak resolution and sample throughput.. Moreover, additional merits of the proposed method over the classical skalar one, other than being economic in use, as there is some chemical cut off, is the feasibility of the automatic determination of carbonate ions concentrations in the same run, which could not be achieved automatically by the classical skalarc method, as it always needs mathematical subtraction of bicarbonate concentration from alkalinity concentrations from multi runs. The latter approach is tedious, involved lots of reagents and procedures, time consuming, and could impact the overall method precision and accuracy. The methoddemonstrated selectivity as online automated approach for selective determination of total hardness and calcium hardness in one run and determination of total alkalinity and bicarbonate from the same standard in the second run, when keeping all of the four chemistry reagents aspirated automatically. Sole analysis for every parameter as in the current method was achieved demonstrating simultaneous analysis without discernment, the recovery was found to be comparable with the novel proposed method, but the latter gave a marked enhancement in precision and peak resolution.. Analysis for drinking water samples gave quantitative results with Z score of less than ± 1.2. Accuracy of the automated analysis was investigated by multiple techniques including recovery by standard addition method, run of CRM and t test statistical analysis. The merit of the accuracy for this proposed method has been demonstrated successfully through applications to real samples.

Micellization behavior of cationic and anionic surfactant mixtures at different temperatures: Effect of sodium carbonate and sodium phosphate salts

AbstractHerein, we applied the conductivity measurement technique in order to estimate the critical micelle concentration (cmc) of pure sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) as well as their mixed systems in attendance of different salts at five various temperatures. The micellization of SDS + CTAB mixed systems was found to take place at intermediate cmc values of the two pure surfactants. The values of cmc dwindle with the enhancement of the mole fraction of CTAB. The cmc values follow different trend in different salts. The degree of the interaction between SDS and CTAB in occurrence of salt was estimated from the experimentally estimated value of cmc and their ideal values (cmcid). The observed cmc of individual surfactants along with their mixed systems dwindles in the occurrence of the electrolyte. The values of micellar mole fraction, X1, of CTAB at different stoichiometric mole fractions of CTAB was determined on the basis of different proposed models mentioned in the literature. Different thermodynamics parameters were estimated from the magnitudes of the degree of counterion dissociation and cmc at different temperatures. The magnitudes of free energy of micellization ( ), interaction parameter (β), and excess free energy (∆Gex) estimated for the studied systems were obtained to be negative in absence/attendance of electrolyte at all temperatures. The values of activity coefficients (f1 and f2) were also determined on the basis of different proposed models. All of the estimated results signify the strong interaction between the studied amphiphiles.

Origin and chemical and isotopic evolution of dissolved inorganic carbon (DIC) in groundwater of the Okavango Delta, Botswana

ABSTRACTThe origin and the chemical and isotopic evolution of dissolved inorganic carbon (DIC) in groundwater of the Okavango Delta in semi-arid Botswana were investigated using DIC and major ion concentrations and stable oxygen, hydrogen and carbon isotopes (δD, δ18O and δ13CDIC). The δD and δ18O indicated that groundwater was recharged by evaporated river water and unevaporated rain. The river water and shallow (<10 m) groundwater are Ca–Na–HCO3 type and the deep (≥10 m) groundwater is Na–K–HCO3 to HCO3–Cl–SO4 to Cl–SO4–HCO3. Compared to river water, the mean DIC concentrations were 2 times higher in shallow groundwater, 7 times higher in deep groundwater and 24 times higher in island groundwater. The δ13CDIC indicate that DIC production in groundwater is from organic matter oxidation and in island groundwater from organic matter oxidation and dissolution of sodium carbonate salts. The ionic and isotopic evolution of the groundwater relative to evaporated river water indicates two independent pools of DIC.

Insights into Ceres's evolution from surface composition

AbstractInspired by the recent results of the Dawn mission, thermodynamic models of rock alteration and brine evaporation have been used to help understand the conditions under which water–rock interaction took place within the dwarf planet Ceres. This analysis constrains Ceres's early history and offers a framework within which future observations may be interpreted. A broad range of alteration conditions have been simulated using the Geochemist's Workbench and PHREEQC software, associated with the FREZCHEM model that constrains the consequences of freezing the liquid phase in equilibrium with the observed mineralogical assemblage. Comparison of the modeling results with observed surface mineralogy at Ceres indicates advanced alteration under a relatively high fugacity of hydrogen, a conclusion that is consistent with predictions for, and observations of, large ice‐rich bodies. The simulations suggest production of methane that could help regulate the redox environment and possibly form clathrate hydrates upon freezing of the early ocean. The detection of localized occurrences of natrite (sodium carbonate) at the surface of Ceres provides key constraints on the composition of fluids that are necessarily alkaline. In addition, the combined hydrothermal and freezing simulations suggest that hydrohalite may be abundant in Ceres's subsurface, similar to Earth's polar regions. The global homogeneity of Ceres's surface, made of material formed at depth, suggests a large‐scale formation mechanism, while local heterogeneities associated with impact craters and landslides suggest that some form of sodium carbonate and other salts are accessible in the shallow subsurface.

A Possible Brine Reservoir Beneath Occator Crater: Thermal and Compositional Evolution and Formation of the Cerealia Dome and Vinalia Faculae

The Dawn spacecraft has imaged several putative cryovolcanic features on Ceres, and several lines of evidence point to past cryovolcanic activity at Occator crater. It is therefore possible that cryovolcanism played a key role in delivering sodium carbonate- and chloride-enriched brines to Ceres’ surface in recent geological times. The detection of a 200 km×200 km negative Bouguer anomaly beneath Occator suggests the presence of a low-density region beneath the crater. If this region is a residual, partially crystallized, cryomagma chamber, excess pressures caused by its gradual freezing, or stresses produced by the Occator-forming impact, could have facilitated the delivery of cryolavas to the surface in the geologically recent past. Here, the progressive solidification of a cryomagma chamber beneath Occator and implications for the delivery of cryolavas to the surface has been explored. Models for the behavior of cryolavas at Ceres’ surface, and for the formation of the Cerealia Dome and Vinalia Faculae, are also presented. Minimal crystallization of a subsurface fluid reservoir located at the crust-mantle boundary could have driven cryolavas enriched in chloride salts and NH3 to Ceres’ surface. However, cryolavas enriched in sodium carbonates would have had to have existed at shallower levels in the crust in order to be delivered to the surface via pressure-driven ascent. Depending on the size of the reservoir, cryolavas could have been driven to Ceres’ surface for tens to hundreds of millions of years after cooling of the cryomagma chamber commenced. The mineralogy at Occator is suggestive of subsurface cryomagma reservoirs enriched in sodium carbonate and chloride salts. Aqueous solutions enriched in chloride salts and/or ammonia would have arrived at the surface at warm enough temperatures to erupt if transported in propagating fractures that traveled at least 10−5 m/s. Additionally, if the Cerealia Dome was formed from viscous cryolava extrusions, bulk kinematic lava viscosities may have been between 106–108 m2/s at the onset of relaxation. Plausible relaxation times to form the dome, which are linked to bulk cryolava rheology, are found to have ranged from 2.5 to 273 days. Moreover, the low volatile content necessary to drive explosive eruptions on Ceres supports the possibility that Cerealia and Vinalia Faculae were emplaced as a consequence of ballistic eruptions. The enigmatic geology of Occator crater is consistent with a diversity of exchange processes operating on Ceres in the geologically recent past. Further, the processes that have occurred at Occator could shed light on the changing geology associated with a relic ocean world. Future studies of Occator and Ceres should be undertaken with these results in mind.

Characterization and reactivity of sodium aluminoborosilicate glass fiber surfaces

Multicomponent complex oxides, such as sodium aluminoborosilicate glass fibers, are important materials used for thermal insulation in buildings and homes. Although the surface properties of single oxides, such as silica, have been extensively studied, less is known about the distribution of reactive sites at the surface of multicomponent oxides. Here, we investigated the reactivity of sodium aluminoborosilicate glass fiber surfaces for better understanding of their interface chemistry and bonding with acrylic polymers. Acetic acid (with and without a 13C enrichment) was used as a probe representative of the carboxylic functional groups in many acrylic polymers and adhesives. Inverse gas chromatography coupled to a mass spectrometer (IGC–MS), and solid state nuclear magnetic resonance (NMR), were used to characterize the fiber surface reactions and surface chemical structure. In this way, we discovered that both sodium ions in the glass surface, as well as sodium carbonate salts that formed on the surface due to the intrinsic reactivity of this glass in humid air, are primary sites of interaction with the carboxylic acid. Surface analysis by X-ray photoelectron spectroscopy (XPS) confirmed the presence of sodium carbonates on these surfaces. Computer simulations of the interactions between the reactive sites on the glass fiber surface with acetic acid were performed to evaluate energetically favorable reactions. The adsorption reactions with sodium in the glass structure provide adhesive bonding sites, whereas the reaction with the sodium carbonate consumes the acid to form sodium-carboxylate, H2O and CO2 without any contribution to chemical bonding at the interface.

Simultaneous Electricity Generation and Microbially-Assisted Electrosynthesis in MFCs

Microbial Fuel Cells (MFCs) are bio-electrochemical transducers that generate electricity as a direct result of microbial metabolism, when breaking down organic matter for continuous growth and maintenance. On the other hand, Microbial Electrolysis Cells (MECs) consume electricity to drive chemical reactions and recover hydrogen or other high value chemicals, at the cathode half-cell [1]. In MFCs, electric current is generated when for every electron donated to the electrode surface, a proton is transferred from the anode to the cathode. Other cations such as Na+ or K+ may be present in significantly higher concentrations and are more likely to be transferred through a cation exchange membrane [2]. This normally results in electro-osmotically dragged water from the anode to the cathode, and often results in a phenomenon known as cathode flooding, which is a problem for MFCs and other chemical fuel cells. To this day, bio-electrosynthesis has not been reported for energy-generating MFCs, since it is associated with energy-consuming MECs. The main aim of this work was therefore to investigate the effects on MFC performance of low-cost catalyst-free electrode materials, in conjunction with cation and water transport to the cathode half-cell, in the context of beneficial water accumulation and recovery of valuable resources. Materials and Methods Twelve dual–chamber MFCs were tested in triplicate groups assembled with carbon veil anode electrodes. Half-cell chambers were 25mL each and activated sewage sludge (Wessex Water) was used as the inoculum. The cathode chambers contained carbon based electrodes mechanically pressed against the CEM separator. The tested cathode electrodes included: Microporous Layer on carbon cloth (MPL), carbon fibre veil (CV), MPL on carbon fibre veil (CV MPL) and activated carbon (AC). Results and Discussion Results showed that the range of Pt-free cathodes including plain carbon fibre veil, activated carbon, and microporous layer (MPL) in dual-chamber MFCs generated electric current with simultaneous catholyte generation in the cathode chamber.During MFC operation, the production of catholyte on the surface of the cathode electrode was a direct result of electricity generation, and power output has been correlated with catholyte volume. Moreover, the pH of the formed catholyte (>13) and conductivity, showed gradual increase with current generation. The MFC system fed with real wastewater supplemented with sodium acetate showed sodium recovery on the cathode in the form of sodium carbonate salts. Similarly, when the anode feedstock was supplemented with potassium acetate, KOH was formed on the cathode half-cell with additional crystallisation of potassium salts.This paper demonstrates an innovative and energy-efficient system that exploits microbially assisted electrosynthesis for the recovery of valuable elements from wastewater, in the form of chemicals (NaOH, KOH) and electricity. Conclusions This approach leads to carbon capture through wet caustic scrubbing on the cathode, which locks the carbon dioxide into carbonate salts. Acknowledgements This work has been supported by the Bill & Melinda Gates Foundation, grant no. OPP1094890, and the UK EPSRC, grant numbers EP/I004653/1 and EP/L002132/1.