NaCl Brine Solution Research Articles

The inhibition effect of 1, 3-diazole glyoxaline on corrosion of API 5L X52 pipeline steel in oilfield produced water under sweet corrosive conditions

Corrosion induced by aqueous environments containing carbon dioxide (CO2) is a well-documented issue in the oil and gas industries, particularly affecting transportation via steel pipelines. Operational conditions during transportation, including temperature, flow rate, and solution chemistry, significantly influence the corrosion inhibition mechanism. In this study, the corrosion inhibition behavior of API 5L X52 steel in a 3.5 wt% NaCl brine solution saturated with carbon dioxide was investigated using 1, 3-diazole glyoxaline (DG) as an organic inhibitor. Both gravimetric and electrochemical methods were employed to assess corrosion rates and inhibitor efficiency across various temperatures, inhibitor concentrations, and rotational speeds. The outcomes showed that inhibition efficiency increased with inhibitor concentration and temperature. From weight loss measurements, the maximum inhibition efficiency was 98.58 % at 3 × 10−4 M of DG and 60 °C. The polarization investigations showed a reduction in the anodic and cathodic curves in the presence of the inhibitor. This suggested a mixed-type inhibition mechanism. The electrochemical impedance spectroscopy results showed an improvement in charge transfer resistance due to the formation of a protective layer on the metal surface. In addition, AFM, SEM, contact angle, hardness, and roughness measurements proved the enhancement in surface morphology due to the presence of DG.

EFFECT OF CLAY MINERALOGY AND BRINE CONCENTRATION ON THE SWELLING PROPERTIES OF SHALE.

Chemical wellbore instability is mostly attributed to the “unfavorable interaction” between the formation pore fluid, its shale constituents and the drilling fluid, this is mostly experienced in terms of shale swelling that tends to under gauge the drilled well. This study was conducted to examine the impact of brine concentration and mineralogy on the swellability of shale. Sixteen shale samples were obtained from selected wells across two selected fields (OR and OG) in the Niger Delta. X-ray diffraction analysis was carried on the shale samples to determine its mineralogy distribution. A Nacl brine solution was prepared alongside a water based mud formulated using sodium chloride brine of varied concentration. The shale samples were tested for its swellability in both brine solution formulated water based mud for 24 hours and 48 hours. Results obtained showed that there were more clay minerals (56%) across both fields and that Palygorskite was the most abundant clay minerals for both fields. Also, for the swelling test (shale-in-brine and shale-in-mud) that the shale samples swelled in both medium as expected, but to different degrees, mainly as a function of the mineralogy content of the shale and the brine concentration of the fluid in which they are immersed. The import of this goes to buttress the necessity for understanding the place of mineralogy and concentration in the study of wellbore instability caused by chemical interaction.

Atomistic insights into role of low salinity water on montmorillonite-brine interface: Implications for EOR from clay-bearing sandstone reservoirs

Low salinity waterflooding (LSWF) is considered as a potentially promising approach to improve oil production from petroleum reservoirs. Nevertheless, ambiguities about dominant mechanisms and influential factors controlling the wettability alteration on rock surface still remain elusive. To date, the main attention has been given to securitizing the impact of salinity, oil composition, rock surface characteristics, and cationic part of the brine, largely overlooking the impact of anionic components of the brine. However, this is of great importance and interest to clarify how the anionic component of salt can contribute to rock-brine interface characteristics. In this paper, we used Molecular Dynamics (MD) simulation technique to characterize the effect of anionic components of brine solution on intermolecular interactions at the montmorillonite-brine interface. Here, the emphasis was put on NaCl and Na2SO4 brine solution to compare the ionic behavior of Cl- and SO42- in terms of distribution adjacent to the clay surface, potential for ionic aggregation formation, and pairwise interactions over a salinity range of 2000 ppm to 70000 ppm. Results obtained from this research work show that anionic SO42- accumulate nearby the clay surface in the form of ionic aggregations with Na+ cations, compared to the Cl- anions, which are uniformly distribute over the clay surface. The strong propensity of SO42- towards Na+ reduces the possibility of hydration by water molecules, disintegrating the bridging role of Na+ to adsorb oil constituents onto the clay surface. Furthermore, the disparate adsorption of SO42--Na+ aggregation onto the clay slab hinders oil diffusion toward the surface. Finally, besides salinity, anionic components of brine solution have no effect on expansion of the electrical double layer (EDL), casting a shadow on this phenomenon as a driving factor of LSWI-EOR. The results obtained from this research work can further our understanding of clay-brine interaction which is a major mechanism behind low salinity effect in clay-bearing petroleum reservoirs.

Experimental investigation of GO-HPAM and SiO2-HPAM composite for cEOR: Rheology, interfacial tension reduction, and wettability alteration

The interest in designing and developing polymeric nanoparticles has grown in recent years. The inclusion of nanoparticles in polymer solutions enhances several properties, such as stability, rheological and shear characteristics, polymer adsorption, wettability alteration, and so on, leading to increased oil recovery. Graphene oxide (GO) nanosheets and Aerosil 300 Silica oxide (SiO2) are the superior nanoparticles because of their robust thermal and mechanical properties. However, a systematic study of the use of GO and SiO2 in hydrolyzed polyacrylamide (HPAM) has not been reported. The present research seeks to improve the stability of nanoparticles, the rheological characteristics of polymeric nanofluids, and to understand the functional interaction of nanoparticles in reducing interfacial tension and altering wettability. The nano polymer composites were characterized by Fourier-transform infrared spectroscopy and scanning electron microscopy. The samples were treated with NaCl (30,000 mg/L) and CaCl2 (1000 mg/L) brine solutions at 25 °C and 80 °C. The findings indicated that the addition of GO and SiO2 into HPAM significantly improves rheological properties, reduced IFT, and decreased contact angle. GO performs better than SiO2 in terms of better rheological properties and the reduction of IFT. However, the use of SiO2 in HPAM resulted in a lower contact angle in comparison to GO-HPAM nano-polymeric solution. The synergetic effect of GO and SiO2 with HPAM showed promising results under harsh reservoir conditions and hence can be considered as a good candidate for the application of chemical enhanced oil recovery.

Produced water softening using high-pH catholyte from brine electrolysis: reducing chemical transportation and environmental footprints

This study evaluates the benefits of using brine electrolysis for generating caustic soda (NaOH) and free chlorine for on-site produced water (PWs11Produced Water) treatment. A two-compartment electrochemical cell was shown to generate NaOH solutions (pH > 12, faradic efficiency 93%) and chlorine (faradic efficiency 32%) from a NaCl brine solution at a current density of 10 mA/cm2. The catholyte was used for softening field-collected PWs. The degree of Mg removal depends mostly on the catholyte/PW mixture pH with pH 11 achieving >90% removal. Ca removal is poor (<10%) due to low bicarbonate alkalinity in the PWs. Soda ash alone at a dose equivalent to the total hardness of the PWs helps CaCO3 precipitation and Ca removal (>90%). The combined treatment of the catholyte and a reduced quantity of soda ash achieves better or comparable Ca removal compared to the full stoichiometric amounts of soda ash alone. Ba and Sr removal patterns closely follow those of Ca, suggesting co-precipitation of these cations as the primary removal mechanism. Organic removal is negligible during chemical softening; however, activated carbon filtration achieves >90% of total organic carbon (TOC) removal in all PWs. A treatment scheme is proposed for field generation of caustic soda and chlorine from PW. The economic analysis demonstrates the significant cost-effectiveness of the approach compared to purchasing the NaOH.

An experimental evaluation of low salinity water mechanisms in a typical Brazilian sandstone and light crude oil with low acid/basic number

Low salinity water injection (LSWI) is a current and cost-effective method to enhance oil recovery by changing the salinity and composition of the injected water. However, the synergistic effect of chemical composition, concentration and in particular the pH of the brine in oil recovery during LSWI remains not well understood. In addition, there is a lack of low salinity studies in Brazilian sandstone rocks and light paraffinic crude oils of low acid/basic number to date. This paper investigates oil recovery mechanisms and the pH effect in high and low salinity brine solutions using samples from a clastic reservoir in Recôncavo basin, northeastern Brazil. Zeta potential and interfacial tension measurements, oil adsorption analysis using a quartz crystal microbalance with dissipation monitoring, and core flooding experiments were performed using different concentrations and pH values of synthetic formation water (SFW), NaCl and CaCl2 brine solutions. The results indicate that when the reservoir pH changes towards the alkaline conditions driven by ionic exchanges during LSWI, it may approximate the isoelectric point (IEP) of pH-dependent surface charges in oil and rock minerals, weakening the electrostatic attraction between their surfaces, and consequently contributing to increased oil recovery. The findings of this study can help understand oil recovery mechanisms during LSWI according to the type and content of pH-dependent surface charges in sandstone rocks and crude oils. This study also shows how to pre-select potential field candidates in the Recôncavo basin and similar formations for stand-alone and hybrid LSWI applications.

Optimization of Dynamic Interfacial Tension for Crude Oil–Brine System in the Presence of Nonionic Surfactants

AbstractIn this study, interfacial tension (IFT) is measured between brine and crude oil (a sample of heavy oil from an Iranian oil reservoir) in the presence of two nonionic surfactants, KEPS 80 (Tween 80) and Behamid D, at different concentrations in order to optimize the concentrations of the surfactants. The surface response method is used to design the IFT measurement experiments. The experimental design and optimization is performed using the IFT as an objective function and temperature, concentration, and time as independent variables. In addition to the IFT measurement, various experiments such as stability tests of the surfactants in NaCl brine solutions, adsorption experiments on the carbonated rock surface, and phase behavior tests are performed to investigate the behavior of KEPS 80 and Behamid D in the enhanced oil recovery process. At the end, a model using the response surface statistical technique is designed for optimization of the concentrations of the surfactants, and a surfactant molecular migration mechanism is used for explanation of the dynamic IFT variation versus time. In the case of IFT experiments, the effect of surfactant concentration (at 1000, 3000, and 5000 ppm) on the dynamic IFT is investigated. The experiments are performed at four temperatures (25, 40, 50, and 67°C). The results show that the oil–brine IFT values can be reduced to about 4 mN m−1 in the presence of Behamid D and to about 1 mN m−1 in the presence of KEPS 80 at low concentrations.

Use of selected yeast starter cultures in industrial-scale processing of brined Taggiasca black table olives

The aim of this study was to evaluate the effects of six selected yeast starters on natural Taggiasca black table fermentations, in different brine solutions. The olives were subjected to fermentation in 8% (w/v) NaCl, 12% (w/v) NaCl and 12% (w/v) NaCl brine solutions with 0.3% (w/v) citric acid and inoculated with selected yeast starter strains belonging to the following species: Candida adriatica 1985, Candida diddensiae 2011, Cyteromyces matritensis 2005, Nakazawaea molendini-olei 2004, Saccharomyces cerevisiae 2046 and Wickerhamomyces anomalus 1960. Samples of brines and olives were analysed in the initial phase, then again after 30 and 120 days of fermentation. The yeast starters survived differently during the first 30 days of brine fermentation, depending on the NaCl concentration. After 120 days of fermentation N. molendini-olei 2004 and C. matritensis 2005 failed in the brines with 12% NaCl, while the yeast starter cultures C. diddensiae 2011, C. adriatica 1985 and W. anomalus 1960 showed the best performances in terms of survival and competitiveness towards wild yeasts of the brines. The physicochemical and sensorial analysis suggest a potential positive role of these yeasts during the debittering process of the Taggiasca table olives. Considering the combination between yeast starters and the fermentation conditions, the best indication occurred with the brines containing 12% NaCl acidified with citric acid.

Integration of membrane distillation (MD) and solid hollow fiber cooling crystallization (SHFCC) systems for simultaneous production of water and salt crystals

A novel hybrid system of integrating membrane distillation (MD) and solid hollow fiber cooling crystallization (SHFCC) has been successfully developed for simultaneous production of fresh water and inorganic salt crystals from NaCl brine solutions. Porous PVDF hollow fiber membranes consisting of PTFE particles were spun for the MD subsystem, while non-porous PVDF hollow fibers were fabricated as heat exchangers for the SHFCC subsystem. To optimize the operation parameters, the Taguchi's method was utilized for experiment design including three key factors; namely, feed temperature (Tf), distillated amount (Wd) and water amount to wash away the scallant (Ww). Several response factors were experimentally investigated and their signal-to-noise ratios of each response were calculated to identify the optimal settings of control factors. As a result, the best combined parameters to maximize the crystal harvest took place at Wd = 14 g and Tf = 50 °C. Narrowly distributed NaCl crystals with a small mean size of 35–45 µm were successfully generated by the hybrid system, and a relatively long-term MD-SHFCC operation of 15 cycles was conducted to verify the system stability and feasibility. The 15-cycle experiments exhibited an impressive average MD water flux of about 8 kg/m2 h and continuous production of distillate water with a high purity (a NaCl concentration of 0.01 g/L) and NaCl salt crystals with a yield of 64 g per kg feed.

Evolution of Yeast Consortia during the Fermentation of Kalamata Natural Black Olives upon Two Initial Acidification Treatments.

The objective of this study was to elucidate the yeast consortia structure and dynamics during Greek-style processing of Kalamata natural black olives in different brine solutions. Olives were subjected to spontaneous fermentation in 7% (w/v) NaCl brine solution (control treatment) or brine acidified with (a) 0.5% (v/v) vinegar, and (b) 0.1% (v/v) lactic acid at the onset of fermentation. Changes in microbial counts, pH, acidity, organic acids, sugars, and alcohols were analyzed for a period of 187 days. Yeast consortia diversity was evaluated at days 4, 34, 90, 140, and 187 of fermentation. A total of 260 isolates were characterized at sub-species level by rep-PCR genomic fingerprinting with the oligo-nucleotide primer (GTG)5. The characterization of yeast isolates at species level was performed by sequencing of the D1/D2 domain of 26S rRNA gene. Results showed that yeasts dominated the process presenting a relatively broad range of biodiversity composed of 11 genera and 21 species. No lactic acid bacteria (LAB) or Enterobacteriaceae could be enumerated after 20 and 10 days of fermentation, respectively. The dominant yeast species at the beginning were Aureobasidium pullulans for control and vinegar acidification treatments, and Candida naeodendra for lactic acid treatment. Between 34 and 140 days the dominant species were Candida boidinii, Candida molendinolei and Saccharomyces cerevisiae. In the end of fermentation the dominant species in all processes were C. boidinii and C. molendinolei, followed by Pichia manshurica and S. cerevisiae in lactic acid acidification treatment, P. manshurica in vinegar acidification treatment, and Pichia membranifaciens in control fermentation.

Effects of CO2 and H2S on Corrosion of Martensitic Steels in Brines at Low Temperature

Corrosion studies were conducted for martensitic carbon steels in 5 wt% NaCl brine solutions at 4°C and 10 MPa (1,450 psi). These studies simulated different subsurface environments relevant to Arctic drilling. Here, two high-strength martensitic carbon steels, S-135 and UD-165, were studied in three different environments: (1) a CO2-NaCl-H2O solution with a CO2:H2O molar ratio of 0.312 in the whole system, (2) an H2S-NaCl-H2O solution with an H2S:H2O molar ratio of 3.12 × 10−4, and (3) a CO2-H2S-NaCl-H2O solution with the same acid gas to water ratios as environments 1 and 2. Results from the CO2+H2S mixed environment indicated that sour corrosion mechanism was dominant when the CO2:H2S molar ratio was 1,000. This impact of a small amount of H2S on the corrosion mechanism could be attributed to the specific adsorption of H2S on the steel surface. Electrochemical and mass loss measurements showed a distinct drop in the corrosion rate (CR) by more than one order of magnitude when transitioning from sweet to sour corrosion. This inhibiting effect on CR was attributed to the formation of a protective sulfide thin film. Tafel analyses of the anodic reaction showed that the Bockris mechanism was unlikely in the conditions tested. When comparisons were made between modeled and experimental CRs, good agreement was found in the CO2-only and H2S-only environments, but not in the CO2+H2S environment.

Unprecedented regioselective tosylation studies of 2-ene 4,5,6,7-polyol derived from d-ribose

[DMAPTs]+Cl− was employed as a new facile unprecedented regioselective tosylation procedure for 2-ene 4,5,6,7-polyol derived from d-ribose involving chemoselective ditosylation and regioselective allylic tosyl hydrolysis upon work up with sat. NaCl (brine) solution in a single operation by minimizing the side products obtained under classical regioselective tosylation. The same reagent was also employed for rapid quantitative base free tosylation of aniline, phenol, and 2-naphthol. A tentative mechanism for the afore said regioselective tosylation was also proposed.

The surface interactions of a near-neutral carbon nanoparticle tracer with calcite

A new class of nearly charge-neutral carbon-cored nanoparticle tracers are remarkably non-interactive with solid surfaces and could provide a valuable baseline for diverse hydrological and environmental studies of subsurface flow and particle transport. We investigate the causes of inertness by studying the interactions with calcite of a nanoparticle of this class synthesized from malic acid and ethanolamine (M-dots) dispersed in brine (NaCl, CaCl2, and MgCl2) solutions. None of the M-dots are retained in calcite sand-packed columns when dispersed in DI water. Dispersed in the NaCl and mixed brine solutions, 5.6 % of and 7.3 % of the M-dots are initially retained, but 65 and 13 % of these retained particles are subsequently released when the column is flushed with DI water. When dispersed in the CaCl2 and MgCl2 solutions, 65 and 54 % of the M-dots are initially retained, and 28 and 26 % subsequently released in the DI water flush. The M-dots have a small negative zeta potential in all solutions, but the calcite zeta potential changes from strongly negative to strongly positive across the solution series, and the particle retention tracks this change. Derjaguin–Landau–Verwey–Overbeek (DLVO) modeling of the force between a calcite probe and an M-dot coated surface shows that hydration forces repel the particles in the DI water, NaCl, and mixed solutions, but not in the CaCl2 and MgCl2 solutions. These results show that near-zero charge and strongly hydrophilic decoration are the causes of the remarkable inertness of carbon-cored nanoparticles, and also suggest that nanoparticles could be useful in solute-surface interaction studies.

Effect of Heat Treatment on Galvanic Corrosion of Cu/Al/Cu Clad Soaked in 3.5% NaCl Brine Solution

The galvanic corrosion of Cu/Al/Cu clad in 3.5% NaCl brine solution has been studied. No visible intermetallic compounds were found at the Cu/Al interface after roll-bonding, But Intermetallic layer grew up to 40μm after heat treatment 500°C for 10hours. The galvanic corrosion occurred significantly in the Al region in contact with Cu. The depth of the dissolved Al gradually decreased with distance away from the Cu/Al interface. Both IDR width and IDR depth increased steadily with increase of soaking time. The IDR width and depth of as-roll-bonded Cu/Al/Cu is far greater than those of heat-treated Cu/Al/Cu at 500°C for 10hours, suggesting the presence of intermetallic compounds influences the galvanic corrosion behavior.

Salt- and temperature-stable quantum dot nanoparticles for porous media flow

The transport of colloidal nanoparticles (NPs) through porous media is a well-studied phenomenon at ambient temperature and in low-to-zero salinity water found in aquatic systems. Little is known at much higher temperatures and salinities such as conditions found in petroleum reservoirs, thus limiting the possible use of NPs in downhole oilfield applications. Using 3-nm CdSe quantum dots (QDs) as a model material, we report that NPs can be prepared with excellent colloidal stability at high ionic strengths and elevated temperatures. QDs with an outer coating of a nonionic ethoxylated alcohol surfactant showed little aggregation in synthetic seawater with ionic strength of 0.55M and 1M NaCl brine solution based on dynamic light scattering analysis. They showed colloidal stability up to 70°C, close to the cloud point temperature of the nonionic surfactant. They further showed nearly unimpeded flow behavior when carried in high-salinity water through a packed column of crushed calcite or sandstone mineral at room temperature. QDs were successfully passed through a medium-permeability Berea sandstone core (100mDa) at 17atm, 25°C, and 8mL/h. The preparation strategy for salt- and temperature-stable QDs is applicable to a wide range of particle sizes and compositions, toward the general handling and use of functional NPs in high-salinity environments.

Cluster models of aqueous Na+ and Cl− in sea water/ice

In this article, we present finite cluster models of aqueous solutes [NaCl(H2O)10, NaCl(H2O)5, and (H2O)6] in terms of molecular geometry and vibrational spectra for interpretation of experimental infrared spectra of NaCl brine solutions. The quantum chemistry program GAMESS is used to optimize the model clusters to a local minimum energy gradient of less than 5.0d-6 hartrees/bohr with B3LYP in a gaussian basis of 6-31G(d,p). Harmonic frequencies are computed for comparison with the infrared spectra measured by attenuated total reflection of a temperature-controlled Ge plate under a layer of cold brine solution. The motivation for this research is to understand the mechanism by which freezing seawater excludes halide ions (mainly Cl−) and why the O–H stretching region of the spectra changes with temperature. Frost flowers, sea ice, and snow in marine environments contain concentrated halides in liquid brine at their surfaces which lead to catalytic destruction of low-altitude ozone in the polar regions of the Earth.

Viscosity and yield stresses of ice slurries formed in water-in-oil emulsions

Molecular inclusion compounds called clathrate hydrates are a common concern in oil and gas pipelines, as they cause disruption to production. These crystalline compounds are over 80 mol% water and are often only stable at high pressures and low temperatures. As a means to understand the rheology of clathrate hydrates, we investigated ice slurries, in crude oil, as a simple analogy to clathrate hydrates. A series of water-in-oil emulsions were prepared at different volume fractions of water, ranging from 0.10 to 0.70. Water used in the samples was deionized watger or a 3.5 wt% NaCl brine solution. The emulsions were cooled to - 10 ° C and the viscosity and yield stress were analyzed as a function of time after nucleation. No yield stresses were observed at volume fractions below 0.2 for fresh water and 0.3 for brine solution. In the fresh water system, the yield stress varied with increasing volume fraction. Between volume fractions of 0.25–0.55, yield stresses were on the order of 300 Pa, and at larger volumer fractions (0.6–0.7) yield stress quickly increased to an unmeasurable value (greater than 3000 Pa, the instrument’s limit). In the brine system, yield stress increased with volume fraction of water. After formation of ice, flow was stopped and the system was “annealed”. During the “annealing” period, the magnitude of complex viscosity of the fresh water system reached a peak value after two hours, decreased for approximately four hours, and then changed little for the next forty hours. The yield stress during “annealing” mimicked the trend of the magnitude of complex viscosity. In the brine system, the magnitude of complex viscosity increased over the first three hours, then changed little. However, the yield stress decreased as the “annealing” time increased. Following the measurements of yield stress, the slurry was conditioned at 500 s - 1 and the apparent viscosity was analyzed as a function of shear rate. At volume fractions greater than 0.10 the slurry was found to be shear thinning and exhibited a viscosity increase compared to the initial emulsion.

Efficacy of natamycin to control fungal growth in natural black olive fermentation

The effect of natamycin as a fungal control agent in natural black olive fermentation according to the traditional anaerobic system was studied. Black Conservolea olives were subjected to spontaneous fermentation in 8% (w/v) NaCl brine solution (control treatment) or brine supplemented with 0.01% (w/v) natamycin (active compound) for an overall period of 60 days. The changes in the microbial association (lactic acid bacteria, yeasts, Enterobacteriaceae), pH, titratable acidity, organic acids, and volatile compounds were monitored throughout fermentation. The initial microbiota consisted of lactic acid bacteria, yeasts, and Enterobacteriaceae. The addition of natamycin in the brine inhibited the growth of yeasts, without affecting the population dynamics of bacteria, resulting in a more vigorous fermentation with higher titratable acidity compared to spontaneous control process. Moreover, the presence of natamycin inhibited mould spoilage caused by the development of fungal mycelium on the surface of the brine during the traditional anaerobic fermentation system employed widely in Greece in natural black olive processing. Natamycin could be an important component of a processing system to control fungal growth in natural black olive fermentation and at the same time it has the potential to enhance the process by favouring the growth of the indigenous population of lactic acid bacteria against other competing microorganisms.

Yeast heterogeneity during spontaneous fermentation of black Conservolea olives in different brine solutions

To assess the yeast community structure and dynamics during Greek-style processing of natural black Conservolea olives in different brine solutions. Black olives were subjected to spontaneous fermentation in 6% (w/v) NaCl brine solution or brine supplemented with (i) 0.5% (w/v) glucose, (ii) 0.2% (v/v) lactic acid and (iii) both glucose and lactic acid. Yeast species diversity was evaluated at the early (2 days), middle (17 days) and final (35 days) stages of fermentation by restriction fragment length polymorphism and sequence analyses of the 5.8S internal transcribed spacer and the D1/D2 ribosomal DNA (rDNA) regions of isolates. Analysis revealed a relatively broad range of biodiversity composed of 10 genera and 17 species. In all treatments, yeasts were the main micro-organisms involved in fermentation together with lactic acid bacteria that coexisted throughout the processes. Metschnikowia pulcherrima was the dominant yeast species at the onset of fermentation, followed by Debaryomyces hansenii and Aureobasidium pullulans. Species heterogeneity changed as fermentations proceeded and Pichia membranifaciens along with Pichia anomala evolved as the main yeasts of olive elaboration, prevailing at 17 and 35 days of the process. Molecular techniques allowed for the identification of five yeast species, namely A. pullulans, Candida sp., Candida silvae, Cystofilobasidium capitatum and M. pulcherrima, which have not been reported previously in black olive fermentation. By using molecular techniques, a rich yeast community was identified from Conservolea black olive fermentations. Metschnikowia pulcherrima was reported for the first time to dominate in different brines at the onset of fermentation, whereas Pichia anomala and P. membranifaciens evolved during the course. The addition of glucose and/or lactic acid perturbed yeast succession and dominance during fermentation. Yeasts have an important role in black olive fermentation and contribute to the development of the organoleptic characteristics of the final product. At the same time, certain species can cause significant spoilage. The present study adds to a better knowledge of yeast communities residing in olive fermentations towards a well-controlled process with minimization of product's losses.

Succinate-bonded cellulose: A regenerable and powerful sorbent for cadmium-removal from spiked high-hardness groundwater

The primary objective of this work was to evaluate a chemically modified cellulose for the sorption efficiency and selectivity to remove cadmium from spiked high-hardness groundwater. Heterogeneous esterification of cellulose with succinic anhydride in toluene under basic conditions has proceeded very efficiently to yield the succinylated cellulose (SC) with fairly high DS value, as confirmed by FTIR and solid-state MAS 13C NMR spectroscopies. Deprotonation of the free carboxylic acid group was achieved by alkaline treatment of SC with saturated NaHCO 3 aqueous solution. Batch experiments were carried out on the resulting sodic material (NaSC) to examine its cadmium-removing capability in both distilled water (DW) and spiked groundwater (GW). The results obtained from the sorption characteristics (kinetics, isotherms and pH effect) have revealed that NaSC material is particularly effective in removing cadmium from both DW and GW solutions, with a maximum uptake of 185.2 and 178.6 mg g −1, respectively. These comparable sorption capacities strongly suggest that NaSC sorbent is highly selective to heavy metal over alkaline earth cations (Ca 2+ and Mg 2+) and therefore less susceptible to interference from background ions, naturally present in groundwater. On the other hand, cadmium sorption is shown to decrease with a decrease in pH which is indubitably inherent to the competing proton during the ion-exchange process. Furthermore, the material has proven to be efficiently regenerable by using a NaCl brine solution. Thus, the use of the sorbent sequentially to the first regeneration led to nearly no attenuation in the material's capacity for cadmium-removal. Finally, the sorption effectiveness of NaSC is compared to those of other low-cost sorbents so far reported in the literature.