Molybdenum Mobility During Managed Aquifer Recharge in Carbonate Aquifers.

The mobility of molybdenum (Mo) in groundwater systems has received little attention, although a high intake of Mo is known to be detrimental to human and animal health. Here, we used a comprehensive hydrochemical data set collected during a multi-cycle aquifer storage and recovery test to study the mechanisms that control the mobility of Mo under spatially and temporally varying hydrochemical conditions. The model-based interpretation of the data indicated that the initial mobilization of Mo occurs as a sequence of reactions, in which (i) the aerobic injectant induces pyrite oxidation, (ii) the released acidity is partially buffered by the dissolution of dolomite that (iii) leads to the release of Mo with highly soluble sulfurized organic matter prevailing between the intercrystalline spaces of the dolomite matrix or incorporated in dolomite crystals. Once released, Mo mobility was primarily controlled by pH-dependent surface complexation reactions to the sediments and, to a lesser extent, the capture by iron sulfides (FeS). In the studied system, Mo mobilization could be effectively mitigated by reducing or eliminating pyrite oxidation, which decreases the likelihood of dolomite dissolution and associated Mo release.

Removal of cadmium and lead ions from aqueous solutions by novel dolomite-quartz@Fe3O4 nanocomposite fabricated as nanoadsorbent.

The elimination of heavy metal ion contaminants from residual waters is critical to protect humans and the environment. The natural clay (dolomite and quartz) based composite Fe3O4 nanoparticles (DQ@Fe3O4) has been largely explored for this purpose. Experimental variables such as temperature, pH, heavy metal concentration, DQ@Fe3O4 dose, and contact time were optimized in details. The DQ@Fe3O4 nanocomposite was found to achieve maximum removals of 95.02% for Pb2+ and 86.89% for Cd2+, at optimal conditions: pH = 8.5, adsorbent dose = 2.8 g L-1, the temperature = 25 °C, and contact time = 140 min, for 150 mg L-1 heavy metal ion initial concentration. The Co-precipitation of dolomite-quartz by Fe3O4 nanoparticles was evidenced by SEM-EDS, TEM, AFM, FTIR, XRD, and TGA analyses. Further, the comparison to the theoretical predictions, of the adsorption kinetics, and at the equilibrium, of the composite, revealed that they fit, respectively to, the pseudo-second-order kinetic, and Langmuir isotherm. These both models were found to better describe the metal binding onto the DQ@Fe3O4 surface. This suggested a homogenous monolayer sorption dominated by surface complexation. Additionally, thermodynamic data have shown that the adsorption of heavy metal ions is considered a spontaneous and exothermic process. Moreover, Monte Carlo (MC) simulations were performed in order to elucidate the interactions occurring between the heavy metal ions and the DQ@Fe3O4 nanocomposite surface. A good correlation was found between the simulated and the experimental data. Moreover, based on the negative values of the adsorption energy (Eads), the adsorption process was confirmed to be spontaneous. In summary, the as-prepared DQ@Fe3O4 can be considered a low-cost-effective heavy metals adsorbent, and it has a great potential application for wastewater treatment.

Phosphate removal using dolomite modified with ultrasound: mathematical and experimental analysis.

We studied the dolomite modified using an ultrasound bath and its application in phosphate removal. The modification was applied to improve the physicochemical properties of the dolomite and then to enhance its suitability as an adsorbent solid. The settings for analyzing the adsorbent modification were bath temperature and sonication time. The modified dolomite was characterized by electron microscopy, N2 adsorption/desorption, pore size, and X-ray diffraction. To grasp the pollutant's adsorption mechanism more precisely, we used experimental research and mathematical model analysis. Design of Experiments was conducted to determine the ideal circumstances. In addition, the Bayesian method of Markov Chain Monte Carlo was used to estimate the isotherm and kinetic model parameters. A thermodynamic study was done to investigate the adsorption mechanism. Results show that the surface area of the modified dolomite was greater, enhancing its adsorption properties. To remove more than 90% of the phosphate, the optimal operational parameters for the adsorption were pH 9, 1.77 g of adsorbent mass, and 55 minutes of contact time. The pseudo-first-order, Redlich-Peterson and Sips models presented a good fit to the experimental data. Thermodynamics suggested a spontaneous and endothermic process. The mechanism suggested that physisorption and chemisorption could be involved in phosphate removal.

Molybdenum Release Triggered by Dolomite Dissolution: Experimental Evidence and Conceptual Model.

The injection of oxygenated water into anoxic aquifers during managed aquifer recharge (MAR) can cause the mobilization of metal(loid)s. Here, we study the processes controlling MAR-induced molybdenum (Mo) release in dolomitic aquifers. Sequential chemical extractions and energy dispersive X-ray spectroscopy combined with scanning electron microscopy point to an association of Mo with easily soluble sulfurized organic matter present in intercrystalline spaces of dolomites or directly incorporated within dolomite crystals. The easily soluble character was confirmed by a batch experiment that demonstrated the rapid mobilization of Mo, dissolved organic carbon, and sulfur. The type and time of batch solution contact with the sulfurized organic matter impacted the release of Mo, as demonstrated by a 36% increase in Mo concentrations when shaking was intensified. Based on the experimental results, a conceptual model for the release of Mo was formulated, where (i) the injection of oxygenated water causes the oxidation of pyrite in the aquifer matrix, and (ii) the associated release of protons (H+) induces the dissolution of dolomite as a buffering reaction, which (iii) enhances the accessibility of the injectant to intercrystalline and incorporated sulfurized organic matter within dolomite, causing the release of Mo.

Strategies towards Producing Non-Polar Dolomite Nanoparticles as Nanofiller for Copolymer Nanocomposite.

Poly (ethylene-co-vinyl acetate) (PEVAc) is a copolymer endowed with high elasticity and resilient properties, potentially utilized in various applications. However, the tensile strength of this copolymer is insufficient for use in certain applications that require enough strength to tolerate high external tension or stress. In this study, dolomite was proposed as a nanofiller to reinforce the PEVAc. Raw dolomite was physically and chemically modified in order to improve its mix ability and interfacial adhesion between the PEVAc and dolomite. Initially, the size of dolomite was reduced by combining the ball-milling and tip-sonication methods. SEM, TEM, and XRD were used to characterize the morphology/structure of the raw dolomite and the size-reduced dolomite. Then, a particle size analysis was performed to confirm the average particle size. Our results show that the particle size of dolomite was reduced from 150 µm to 441.4 nm by the physical modification process (size reduction). Based on the TEM analysis, the Feret diameter (df) of the dolomite particles was also reduced from ~112.78 µm to ~139.58 nm only. This physically modified dolomite is referred as dolomite nanoparticles (DNPs), since one or more of its dimensions is less than 100 nm (e.g., thickness and width). To further improve the dolomite and PEVAc matrix interactions, chemical modification of the DNPs were performed by treating the DNPs with stearic acid, forming non-polar dolomite nanoparticles (NP-DNPs). The presence of stearic acid in dolomite was confirmed through FTIR and contact angle analyses. A PEVAc nanocomposite film with NP-NPDs as a nanofiller appeared more homogeneous and exhibited the highest increment in tensile strength and elongation at break. These findings indicated that the combination of ball milling and tip sonication is an efficient method for producing very fine dolomite particles up to the nano-size range, whereas chemical surface modifications improved the compatibility between the dolomite and the copolymer. The combination of these physical and chemical modifications helped to develop a homogeneous copolymer nanocomposite system with improved tensile properties.

Investigations on Potential Applications of CaMg(CO3)2 Nanoparticles.

Calcium magnesium carbonate nanoparticles (CaMg(CO3)2 NPs), well-known as dolomite, are formed by the replacement of half of the calcite minerals of limestone. The dolomite (CaMg(CO3)2) nanoparticles are composed of calcite (CaCO3) and magnesium carbonate (MgCO3), both of which offer promising strategies for maintaining growth and development in mammals and agricultural plants. A grounded mixture of dolomite limestone was prepared via colloidal precipitates for the synthesis of CaMg(CO3)2 NPs, and their characteristics were examined using XRD, particle size analysis by DLS, and surface morphology by SEM and TEM. X-ray photoelectron spectroscopy was used to investigate the binding energy of each element of the dolomite NPs. Spectroscopy revealed that colloidal precipitation is the ideal method for producing NPs. We assessed the numerous beneficial impacts of CaMg(CO3)2 NPs in diverse sectors such as agriculture, cancer treatment, and microbiology in this study. Furthermore, an in vivo study was also carried out on chickens to observe the effects of CaMg(CO3)2 NPs. The obtained results showed that the treated group with CaMg(CO3)2 NPs maintained a more uniform calcium absorption rate than the control group did. The findings of this study suggest that CaMg(CO3)2 NPs operate as a stimulant for plants and as an inhibitory agent for bacteria and cancer cells.

Investigation of differential levels of phosphorus fixation in dolomite and calcium carbonate amended red soil.

BACKGROUND: The pH adjustment of acidic red soils with lime materials is beneficial for the reduction of phosphorus (P) fixation. However, the reasons for varying levels of P activation after adding different lime materials have not been fully investigated. Therefore, this study examined changes in soil labile P and P forms after phosphate application to calcium carbonate (CaCO3 ) and dolomite amended red soil during a 120-day incubation period. Also change of P sorption properties in the amended soil samples from day 120 were examined through a sorption-desorption experiment. RESULTS: The increase of soil H2 O-P and NaHCO3 -P in the CaCO3 and dolomite amended soil treatments was mainly ascribed to the decline of the NaOH-P. However, when compared with the control treatment after 120 days, soil Olsen-P significantly increased by 34% and 66% in the CaCO3 and dolomite treatments. The Hedley P fractionation results demonstrated that the CaCO3 application caused a notable increase of HCl-P (stable Ca-P), which was 88.4% higher than that in the dolomite treatment. However, the formation of stable P was strongly suppressed in the dolomite treatment due to the presence of magnesium (Mg), which was identified by the negative relationship between M3-Mg and HCl-P. In line with these findings, P sorption-desorption work showed weaker P binding energy in the dolomite treatment relative to the CaCO3 treatment. CONCLUSION: In terms of increasing P availability in red soil, this study suggests that dolomite should be used to substitute CaCO3 in order to reduce the soil P fixation. © 2021 Society of Chemical Industry.

High Magnesium Calcite and Dolomite composition carbonate in Amphiroa (Lithophyllaceae, Corallinales, Rhodophyta): further documentation of elevated Mg in Corallinales with climate change implications.

Species of the calcified, articulate coralline Amphiroa are key components of many shallow marine ecosystems. Understanding their mineral composition is important as their susceptibility to dissolution, due to ocean acidification, may vary with mineral composition. We studied the distribution of Mg-calcite, very high magnesium calcite (VHMC), and dolomite within Amphiroa species to elucidate their mineral properties and susceptibility to dissolution. Results revealed that the asymmetrical X-ray diffraction (XRD) pattern typical of Amphiroa globally represents high levels of VHMC and dolomite composition carbonate. The dolomite seems most likely to be disordered, but higher resolution XRD is required for confirmation. The calcified long sides of medullary cells have predominantly VHMC/dolomite and the corners have bands of VHMC/dolomite. Epithallial cell walls are low Mg-calcite, and cortical cells are low Mg-calcite with bands of VHMC. VHMC/dolomite is more stable than Mg-calcite, and this may provide a competitive advantage for Amphiroa species as seawater pH declines. Further work is required to determine the metabolic controls on VHMC/dolomite mineral formation.

Oxygen isotope composition of the Phanerozoic ocean and a possible solution to the dolomite problem.

The 18O/16O of calcite fossils increased by ∼8‰ between the Cambrian and present. It has long been controversial whether this change reflects evolution in the δ18O of seawater, or a decrease in ocean temperatures, or greater extents of diagenesis of older strata. Here, we present measurements of the oxygen and ?clumped" isotope compositions of Phanerozoic dolomites and compare these data with published oxygen isotope studies of carbonate rocks. We show that the δ18O values of dolomites and calcite fossils of similar age overlap one another, suggesting they are controlled by similar processes. Clumped isotope measurements of Cambrian to Pleistocene dolomites imply crystallization temperatures of 15-158 °C and parent waters having δ18OVSMOW values from -2 to +12‰. These data are consistent with dolomitization through sediment/rock reaction with seawater and diagenetically modified seawater, over timescales of 100 My, and suggest that, like dolomite, temporal variations of the calcite fossil δ18O record are largely driven by diagenetic alteration. We find no evidence that Phanerozoic seawater was significantly lower in δ18O than preglacial Cenozoic seawater. Thus, the fluxes of oxygen-isotope exchange associated with weathering and hydrothermal alteration reactions have remained stable throughout the Phanerozoic, despite major tectonic, climatic and biologic perturbations. This stability implies that a long-term feedback exists between the global rates of seafloor spreading and weathering. We note that massive dolomites have crystallized in pre-Cenozoic units at temperatures >40 °C. Since Cenozoic platforms generally have not reached such conditions, their thermal immaturity could explain their paucity of dolomites.

Megaprepuce: a systematic review of a rare condition with a controversial surgical management.

Megaprepuce (MP) is a rare and challenging condition characterised by an excessive inner prepuce, paucity of penile skin and an extremely narrow phimotic ring. The aetiological factors leading to its development are poorly understood. A variety of surgical techniques have been described in the last 26 years mostly with small number of patients and short follow-up. It is also highly likely that some series have in the past included different variants of inconspicuous penis combining concealed penis, MP and webbed penis. This article is a systematic review of the literature on Megaprepuce; in particular the embryology, history, aetiology, and the surgical techniques available for the correction of this unique penile anomaly will be presented and discussed in this study.

First-Principle Studies of the Vibrational Properties of Carbonates under Pressure.

Using the density functional theory with the hybrid functional B3LYP and the basis of localized orbitals of the CRYSTAL17 program code, the dependences of the wavenumbers of normal long-wave ν vibrations on the P(GPa) pressure ν(cm-1) = ν0 + (dv/dP)·P + (d2v/dP2)·P and structural parameters R(Å) (R: a, b, c, RM-O, RC-O): ν(cm-1) = ν0 + (dv/dR) - (R - R0) were calculated. Calculations were made for crystals with the structure of calcite (MgCO3, ZnCO3, CdCO3), dolomite (CaMg(CO3)2, CdMg(CO3)2, CaZn(CO3)2) and aragonite (SrCO3, BaCO3, PbCO3). A comparison with the experimental data showed that the derivatives can be used to determine the P pressures, a, b, c lattice constants and the RM-O metal-oxygen, and the RC-O carbon-oxygen interatomic distances from the known Δν shifts. It was found that, with the increasing pressure, the lattice constants and distances R decrease, and the wavenumbers increase with velocities the more, the higher the ν0 is. The exceptions were individual low-frequency lattice modes and out-of-plane vibrations of the v2-type carbonate ion, for which the dependences are either nonlinear or have negative dv/dP (positive dv/dR) derivatives. The reason for this lies in the properties of chemical bonding and the nature of atomic displacements during these vibrations, which cause a decrease in RM-O and an increase in RC-O.

Simultaneous removal of chromate and phosphate using different operational combinations for their adsorption on dolomite and banana peel.

Chromate and phosphate are contaminant frequently present in industrial effluents such as tanneries. The objective of this work is to evaluate the efficiency of different operational combinations with dolomite and banana peel for the adsorption of phosphate and chromate in binary solutions. Both adsorbents are residuals from construction and food industries, respectively. Therefore, its use propitiates the reduction of treatment costs and it is an approach to the premises of the circular economy. In this work, the dolomite and banana peel adsorption efficiencies in simple and binary systems were studied. Equilibrium and kinetics tests were carried out in batch and in a fixed bed reactor. Dolomite was found to be selective for the adsorption of phosphate and banana peel for that of chromate. The mixture of adsorbents produced similar phosphate and chromate removal than each adsorbent individually. Therefore, the removals of both contaminants from binary solutions were tested using a fixed bed reactor filled with the mix of adsorbents and the breakthrough curves were analyzed. The obtained removals were 99% of phosphate and 70% of chromate. Finally, a brief discussion was held on the reuse and disposal of saturated adsorbents.

Ex-situ catalytic pyrolysis of chicken litter for bio-oil production: Experiment and characterization.

The depletion of fossil fuels has been a greater concern to the world due to the demand for energy that tremendously increasing with urbanization and population growth. For sustainable development, power industries are trying to find suitable substitute of petroleum fuel which is environment friendly and economically feasible. The biomass such as the production of bio-oil from chicken litter could be a possible alternative source of energy. The conversion of the feedstock was conducted through a catalytic pyrolysis process in an ex-situ fixed bed reactor heated at 500 °C with a heating rate of 50 °C/min. Proximate, ultimate, and calorific analysis of the feedstock was studied using TGA/DTG analysis, CHNS, and bomb calorimeter, respectively. GCMS and py-GCMS experiments on the bio-oil showed that the HHV of the feedstock was 16.01 MJ/kg. The addition of catalyst improved the quality of the bio-oil yield. The presence of dolomite and ZMS-5 catalyst enhances the phenols and aromatic content, respectively. Biomass to catalyst (B/C) ratio increased the oil production from 43.6g to 51.9g for dolomite and 43.6g-47.1g for ZMS-5 with the B/C ration of 20g:3g. Elevating the B/C ratio increases the pyrolytic liquid yield with greater influence on the furanic compound.

The Intensity of Heat Exchange between Rock and Flowing Gas in Terms of Gas-Geodynamic Phenomena.

Gas-induced geodynamic phenomena can occur during underground mining operations if the porous structure of the rock is filled with gas at high pressure. In such cases, the original compact rock structure disintegrates into grains of small dimensions, which are then transported along the mine working space. Such geodynamic events, particularly outbursts of gas and rock, pose a danger both to the life of miners and to the functioning of the mine infrastructure. These incidents are rare in copper ore mining, but they have recently begun to occur, and have not yet been fully investigated. To ensure the safety of mining operations, it is necessary to determine parameters of the rock-gas system for which the energy of the gas will be smaller than the work required to disintegrate and transport the rock. Such a comparison is referred to as an energy balance and serves as a starting point for all engineering analyses. During mining operations, the equilibrium of the rock-gas system is disturbed, and the rapid destruction of the rock is initiated together with sudden decompression of the gas contained in its porous structure. The disintegrated rock is then transported along the mine working space in a stream of released gas. Estimation of the energy of the gas requires investigation of the type of thermodynamic transformation involved in the process. In this case, adiabatic transformation would mean that the gas, cooled in the course of decompression, remains at a temperature significantly lower than that of the surrounding rocks throughout the process. However, if we assume that the transformation is isothermal, then the cooled gas will heat up to the original temperature of the rock in a very short time (<1 s). Because the quantity of energy in the case of isothermal transformation is almost three times as high as in the adiabatic case, obtaining the correct energy balance for gas-induced geodynamic phenomena requires detailed analysis of this question. For this purpose, a unique experimental study was carried out to determine the time required for heat exchange in conditions of very rapid flows of gas around rock grains of different sizes. Numerical simulations reproducing the experiments were also designed. The results of the experiment and the simulation were in good agreement, indicating a very fast rate of heat exchange. Taking account of the parameters of the experiment, the thermodynamic transformation may be considered to be close to isothermal.

Proto-dolomite formation in microbial consortia dominated by Halomonas strains.

Microbes can be found in hypersaline environments forming diverse populations with complex ecological interactions. Microbes in such environments were found to be involved in the formation of minerals including dolomite, a mineral of economic importance and whose origin has been long-debated. Various reports on in vitro experiments using pure cultures provided evidence for the microbial role in dolomite formation. However, culturing experiments have been limited in scope and do not fully address the possible interactions of the naturally occurring microbial communities; consequently, the ability of microbes as a community to form dolomite has been investigated in this study. Our experiments focused on examining the microbial composition by culturing aerobic heterotrophs from the top hypersaline sediments of Al-Khiran sabkha in Kuwait, a modern dolomite-forming environment. The objectives of this study were to assess the ability of two microbial consortia to form dolomite using enrichment culture experiments, mineralogy, and metagenomics. Proto-dolomite was formed by a microbial community dominated by Halomonas strains whereby degradation of the extracellular polymeric substances (EPS) was observed and the pH changed from 7.00 to 8.58. Conversely, proto-dolomite was not observed within a microbial community dominated by Clostridiisalibacter in which EPS continuously accumulated and the pH slightly changed from 7.00 to 7.29.

Microbial community composition and dolomite formation in the hypersaline microbial mats of the Khor Al-Adaid sabkhas, Qatar.

The Khor Al-Adaid sabkha in Qatar is among the rare extreme environments on Earth where it is possible to study the formation of dolomite-a carbonate mineral whose origin remains unclear and has been hypothetically linked to microbial activity. By combining geochemical measurements with microbiological analysis, we have investigated the microbial mats colonizing the intertidal areas of sabhka. The main aim of this study was to identify communities and conditions that are favorable for dolomite formation. We inspected and sampled two locations. The first site was colonized by microbial mats that graded vertically from photo-oxic to anoxic conditions and were dominated by cyanobacteria. The second site, with higher salinity, had mats with an uppermost photo-oxic layer dominated by filamentous anoxygenic photosynthetic bacteria (FAPB), which potentially act as a protective layer against salinity for cyanobacterial species within the deeper layers. Porewater in the uppermost layers of the both investigated microbial mats was supersaturated with respect to dolomite. Corresponding to the variation of the microbial community's vertical structure, a difference in crystallinity and morphology of dolomitic phases was observed: dumbbell-shaped proto-dolomite in the mats dominated by cyanobacteria and rhombohedral ordered-dolomite in the mat dominated by FAPB.

Dolomite used in phosphate water treatment: Desorption processes, recovery, reuse and final disposition.

Desorption is a method that contributes to two important aspects for the sustainability of the water treatments that involve adsorption processes: a) the regeneration of the adsorbent making it reusable in several efficient cycles and, b) the recovery of the adsorbate. In previous studies, it was shown that dolomite constituted an efficient adsorbent of phosphates from aqueous solutions. Once the adsorbent saturation is achieved, it becomes useless for further uses, generating waste, a new environmental problem if it could not be properly disposed. In this work, the main objectives were to study the phosphate desorption process for the recovery and reuse of dolomite and to evaluate the possibilities of a final disposal of exhausted dolomite for agricultural soil improvement and applying the desorbed phosphate as fertilizer. The most efficient agent for the desorption process was 1 M NH4Cl. Ultrasound evidenced a negative effect on desorption. The pseudo-second order model fitted better the experimental data and the equilibrium time was 30 min. Up to four efficient adsorption-desorption cycles were obtained. Phosphate bioavailability of exhausted dolomite was assessed with autochthonous microorganisms. The obtained extracts were used in Lactuca sativa growth experiments, establishing that they are not phytotoxic and otherwise, could promote the vegetal growth.

Variation in sampling effort affects the observed richness of plant-plant interactions via heterospecific pollen transfer: implications for interpretation of pollen transfer networks.

PREMISE OF THE STUDY: There is growing interest in understanding plant-plant interactions via pollen transfer at the community level. Studies on the structure and spatial variability of pollen transfer networks have been valuable to this understanding. However, there is high variability in the intensity of sampling used to characterize pollen transfer interactions, which could influence network structure. To date, there is no knowledge of how sampling effort influences the richness of pollen on stigmas and thereby transfer interactions observed, nor how this may vary across species and study sites. METHODS: We use rarefaction curves on 16 species to characterize the relationship between sampling effort (number of stigmas analyzed) and the richness of pollen transfer interactions recorded. We further assess variability in this relationship among species, plant community types, and sites within a single plant community. KEY RESULTS: We show high among-species variation in the amount of sampling required to sufficiently characterize interspecific pollen transfer. We further reveal variability in the sampling effort-interaction richness relationship among different plant communities and even for the same species growing in different sites. CONCLUSIONS: The wide heterogeneity in the sampling effort required to accurately characterize pollen transfer interactions observed has the potential to influence the characterization of pollen transfer dynamics. Thus, sampling completeness should be considered in future studies to avoid overestimation of modularity and specialization in pollen transfer networks that may bias the predicted causes and expected consequences of such processes for plant-plant interactions.

Effect of brine salinity and guar gum on the transport of barium through dolomite rocks: Implications for unconventional oil and gas wastewater disposal.

This research aimed to elucidate the effect of brine salinity and guar gum on the sorption and transport of Ba in dolomite rocks collected from the Arbuckle formation in Oklahoma, USA. Guar gum represents the most important organic additive used in viscosified fracturing fluids, and Ba constitutes the most common and abundant heavy metal found in unconventional oil and gas (UOG) wastewater. Batch experiments conducted using powdered dolomite rocks (500-600 µm particle size) revealed that at brine salinities of UOG wastewater, chloro-complexation reactions between Ba and Cl ions and pH changes that results from dolomite dissolution are the controlling factors of Ba sorption on dolomite. Competition of Ba with common cations (Ca and Mg) for hydration sites of dolomite, plays a secondary role. Core-flooding experiments conducted to analyze the transport of Ba through natural and synthetic dolomite core plugs are in agreement with the batch sorption experimental results. The transport of Ba through dolomite rocks, increases with increasing brine salinity (0-180,000 mg-NaCl/L). The presence guar gum (50-500 mg/L) does not affect the transport of Ba through dolomite rocks of high flow properties (25-29.6% porosity, 9.6-13.7 mD permeability). However, core-flooding experiments conducted using tight dolomite rocks (6.5-8.6% porosity, 0.06-0.3 mD permeability), revealed that guar gum can retard the transport of Ba by clogging high permeability/porosity regions of tight dolomite rocks. The mechanism of Ba sorption on dolomite can be represented by a sorption model that accounts for both surface complexation reactions on three distinct hydration sites (>CaOHo, >MgOHo, and >CO3Ho), and the kinetic dissolution of dolomite. These results are important in understanding and predicting the fate of Ba present in UOG wastewater disposed into deep dolomite saline aquifers.

Eutrophication decrease: Phosphate adsorption processes in presence of nitrates.

Eutrophication causes aquatic environment degradation as well as serious problems for different purposes of water uses. Phosphorus and nitrogen, mainly as phosphate and nitrate respectively, are considered responsible for eutrophication degradation. The focus of this work was the study of adsorption processes for decreasing phosphate and nitrate concentrations in bi-component aqueous systems. Dolomite and hydroxyapatite were selected as low-cost adsorbents. Obtained results showed that both adsorbents have high capacity for phosphate adsorption which the presence of nitrate does not modify. Hydroxyapatite proved to be the most efficient adsorbent, however, it showed a low percentage of desorption and few possibilities of reuse. Dolomite, on the other hand, allows a desorption of the adsorbed material that favours its reuse.