Effect Of Water Chemistry Research Articles

Immobilization of U(VI) by stabilized iron sulfide nanoparticles: Water chemistry effects, mechanisms, and long-term stability

• CMC-stabilized FeS (CMC-FeS) nanoparticles can rapidly remove U(VI) from water. • CMC-FeS worked effectively under normal groundwater conditions (pH, DOM, co-solutes) • Reduction accounts for 90% of U(VI) removal and S 2− and S 2 2− are primary e-donors. • High concentrations (≥5 mM) of bicarbonate or DOM may inhibit the U(VI) removal. • Immobilized U kept stable in anoxic condition, while 26% remobilized under air in 180 days. Carboxymethyl cellulose stabilized iron sulfide (CMC-FeS) nanoparticles have been shown promising for reductive immobilization of U(VI) in water and soil. This work aimed to fill some critical knowledge gaps on the effects of the stabilizer and water chemistry, reaction mechanisms, and long-term stability of stabilized uranium. The optimal CMC-to-FeS molar ratio was determined to be 0.0010. CMC-FeS performed effectively over pH 6.0–9.0, with the best removal being at pH 7.0 and 8.0. The retarded first-order model adequately interpreted the kinetic data, representing a mechanistically sounder model for heterogeneous reactants of decaying reactivity. The presence of Ca 2+ (1 mM) or bicarbonate (1 mM) lowered the initial rate constant by a factor of 1.6 and 9.5, respectively, while 1 mM of Na + showed negligible effect. Humic acid at 1.0 mg/L (as total organic carbon) doubled the removal rate, but inhibited the removal at elevated concentrations (≥5.0 mg/L). Fourier transform infrared spectroscopy, X-ray diffractometer, X-ray photoelectron spectroscopy, and extraction studies indicated that reductive conversion of UO 2 2+ to UO 2 (s) was the primary reaction mechanism, accounting for ~90% of U removal at pH 7.0. S 2− and S 2 2− were the primary electron sources, whereas sorbed and structural Fe(II) acted as supplementary electron donors. The immobilized U remained stable under anoxic conditions after 180 days of aging, while ~26% immobilized U was remobilized when exposed to air for 180 days. The long-term stability is attributed to the protective reduction potential of CMC-FeS, the formation of uraninite and associated structural resistance to oxidation, and the high affinity of FeS oxidation products toward U(VI).

Investigation of Smart Waterflooding in Sandstone Reservoirs: Experimental and Simulation Study Part 2

Summary In a previous work (Al-Saedi et al. 2018c), we studied the effect of mineral composition of cores (using synthetic columns with varying mineralogy) on low-salinity (LS) waterflooding, and we presented a reactive-transport model (RTM) for the water/rock interactions. The results showed that kaolinite has the strongest effect and then quartz because of the high kaolinite surface area, and the most effective complexes were >SiOH (hydroxylated Si), >AlO– (aluminum oxide complex on quartz surface), and >SiO– (silicon mono oxide complex on quartz surface). In this paper, we use the same Bartlesville Sandstone cores (constant mineralogy) for all cases to investigate the effect of water chemistry on water/rock interactions during seawater and smart waterflooding of reservoir sandstone cores containing heavy oil. Oil recovery, surface-reactivity tests, and multicomponent reactive-transport simulation using CrunchFlow (Steefel 2009) were conducted to better understand smart waterflooding. Bartlesville Sandstone cores were saturated with heavy oil and connate formation water. Secondary waterflooding of these cores with formation water (FW) at 25°C resulted in an ultimate oil recovery of approximately 50% original oil in place (OOIP) for all reservoir cores in this study. FW salinity was 104,550 ppm. FW was diluted twice to obtain Smart Water 1 (SMW1). SMW2 was similar to SMW1 but depleted in divalent cations (Ca2+ and Mg2+). SMW3 was also similar to SMW1 but depleted in Mg2+ and SO42−, whereas SMW4 was the same as SMW1 but Ca2+ was diluted 100 times. Seawater (SW) salinity was 48,300 ppm, which is close to the SMW salinity (52,275 ppm). No oil recovery was observed during SMW1 flooding, whereas softening SMW1 (SMW2) resulted in a significant additional oil recovery of OOIP. Depleting Mg2+ and SO42− resulted in additional oil recovery but less than in SMW2. Diluting Ca2+ 100 times was the second-best scenario, after depleted Ca2+ in SMW2. The results of this study showed that the more diluted Ca2+ is in the injected brine, the more additional oil recovery that can be obtained, although the other divalent/monovalent cations/anions were increased or decreased or even depleted. Additional reservoir cores were allocated for surface-reactivity tests. The absence of an oil phase allows us to isolate the important water/rock reactions. The Ca2+, Mg2+, and SO42− effluents for all cores were matched using CrunchFlow, and then further investigations of the water/rock interactions were conducted. The RTM showed that decreasing the Mg2+ concentration will decrease the number of the most effective kaolinite edges Si-O− and Al-O−, but was not as pronounced as that in the presence of Ca2+, which explains why lowering the Mg2+ concentration gives lower additional oil recovery and why lowering the Ca2+ concentration gives higher additional oil recovery.

Exposure to metals (Ca, K, Mn) and road salt (NaCl) differentially affect development and survival in two model amphibians

ABSTRACTHuman activity has led to widespread chemical alteration of natural environments. Aquatic ecosystems are especially susceptible to chemical changes, including those caused by runoff and invasive species. Here, we examined the effects of water chemistry, specifically sodium chloride as well as three metals (Ca, K, and Mn) known to differ between native and invasive wetland plant species’ leaf tissues, on the development of two model amphibians: the native Northern leopard frog, Lithobates pipiens, and the non-native African clawed frog, Xenopus laevis. We exposed frog eggs to metal treatment solutions and measured time to hatching (TTH), and following hatching, we exposed tadpoles to a lethal concentration of sodium chloride and recorded time to death (TTD). We found that increasing metal concentrations generally resulted in acceleration of TTH for Xenopus tadpoles, but had no effect on leopard frogs. However, increasing metal concentrations (Ca, Mn) increased leopard frog tadpole susceptibility to NaCl (decreased TTD), while increasing metal concentrations (Ca, K) generally resulted in decreased Xenopus tadpole susceptibility to NaCl. Overall, our data suggest that invasive amphibians may be more tolerant to chemical changes than native amphibians, including those driven by the introduction of invasive plant species.

Study Investigates Smart Waterflooding in Sandstone Reservoirs

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 193238, “Investigation of Smart Waterflooding in Sandstone Reservoirs: Experimental and Simulation Study, Part 2,” by Hasan N. Al-Saedi, SPE, Missouri University of Science and Technology and Missan Oil Company; Ralph E. Flori, SPE, Missouri University of Science and Technology; and Alsaba Mortadha, Australian College of Kuwait, prepared for the 2018 Abu Dhabi International Petroleum Exhibition and Conference, 12–15 November, Abu Dhabi. The paper has not been peer reviewed. In this paper, the authors consider the effect of water chemistry on water/rock interactions during seawater and smart waterflooding of reservoir sandstone cores containing heavy oil. Oil recovery, surface-reactivity tests, and multicomponent reactive-transport simulation were conducted to understand smart waterflooding better. The authors determine that lowering magnesium-ion (Mg2+) concentration results in lower additional oil recovery, and that lowering calcium-ion (Ca2+) concentration leads to higher additional oil recovery. Introduction “Smart water” (SW) can be defined as a water engineered by manipulating the ionic composition (adding or removing ions) regardless of the resulting salinity. An upward pH shift has been reported in the literature during low-salinity (LS) and/or smart waterflooding. That upward shift modifies the wettability of sandstone, thereby increasing oil recovery. When high salinity is displaced by LS water, Ca2+ will be desorbed from the clay surface because ion exchange occurs between hydrogen (H+) and Ca2+ at the negative sites of the clay surface. The organic materials will be then desorbed from the clay because of the reaction between the protonated basic and the acidic materials with hydroxide. The authors’ investigations on free-clay sandstone provided a different insight into such reactions. The observations from chromatographic columns of quartz showed an increase in the acetate detachment from the quartz surface with a significant pH jump during LS waterflooding. The oil-recovery observations from the quartz column supported the proposed mechanism. Previous systematic laboratory works indicated that the abundance of Mg2+ in the formation water (FW) is more effective than Ca2+ for a higher LS enhanced-oil-recovery (EOR) effect. Conversely, the abundance of Ca2+ in the injected LS water has a larger effect on LS EOR. When Mg2+ was present in the LS water, no oil-recovery improvement occurred. Methodology Brines. Synthetic FW and SW were prepared by dissolving sodium chloride (NaCl), calcium chloride (CaCl2), and magnesium chloride (MgCl2) in deionized water. Crude Oil. A reservoir crude oil was de-livered from eastern Kansas from the Bartlesville sandstone reservoir. The crude oil had a viscosity of approximately 600 cp at ambient temperature. The density is 0.83 gm/cc at 20°C. Reservoir Rock Description and Core Preparation. Five Bartlesville sandstone reservoir cores were drilled from the original 3-in. diameter to a 1-in. diameter preserved core from eastern Kansas. The preserved reservoir sandstone cores were delivered with 3-in. diameter. The most abundant mineral was quartz, followed by clays.

The effects of water chemistry on the detachment and dissolution of differently stabilized silver nanoparticles from ceramic membranes

A multilevel statistical model was developed to demonstrate stabilizing agent impact on detachment of silver nanoparticles from ceramic water treatment membranes.

The combined effects of surface texture, flow patterns and water chemistry on corrosion mechanisms of stainless steel condenser tubes

Detailed failure analysis was carried out for a set of leaking vertical condenser tubes made from AISI 304L-type stainless steel. Experimental part of the analysis included non-destructive testing (eddy current testing and dye-penetrant testing), visual and stereoscopic examination, mechanical testing, chemical analysis, optical and scanning electron microscopy (SEM) and X-ray diffraction (XRD). The present failure was found to be a result of a sequence of several interrelated actions. Experimental evidence indicated the leaking to be caused by surface-breaking pitting resulting mainly from under deposit corrosion (UDC) mechanism. The observed UDC, however, was associated with the presence of distinct surface features promoting low local flow velocities and stagnation conditions. These features are believed to be the result of the specific inside diameter (ID) weld scarfing process. The present results also indicated that UDC was followed by flow accelerated corrosion (FAC) upon tube wall perforation. Computational fluid dynamics (CFD) was used to simulate water flow conditions inside the condenser tubes before and after perforation in order to evaluate the suggested failure sequence and the involved damage mechanisms. CFD results were found to be in strong support of the observed experimental evidence and the proposed failure mechanisms. Finally, the three interacting factors, i.e.; surface texture, flow conditions and water chemistry, are discussed in terms of their effects in leading to the observed final failure and forming its distinct morphology.

A Surface Complexation Model of Alkaline-SmartWater Electrokinetic Interactions in Carbonates

Understanding the effect of injection water chemistry is becoming crucial, as it has been recently shown to have a major impact on oil recovery processes in carbonate formations. Various studies have concluded that surface charge alteration is the primary mechanism behind the observed change of wettability towards water-wet due to SmartWater injection in carbonates. Therefore, understanding the surface charges at brine/calcite and brine/crude oil interfaces becomes essential to optimize the injection water compositions for enhanced oil recovery (EOR) in carbonate formations. In this work, the physicochemical interactions of different brine recipes with and without alkali in carbonates are evaluated using Surface Complexation Model (SCM). First, the zeta-potential of brine/calcite and brine/crude oil interfaces are determined for Smart Water, NaCl, and Na2SO4 brines at fixed salinity. The high salinity seawater is also included to provide the baseline for comparison. Then, two types of Alkali (NaOH and Na2CO3) are added at 0.1 wt% concentration to the different brine recipes to verify their effects on the computed zeta-potential values in the SCM framework. The SCM results are compared with experimental data of zeta-potentials obtained with calcite in brine and crude oil in brine suspensions using the same brines and the two alkali concentrations. The SCM results follow the same trends observed in experimental data to reasonably match the zeta-potential values at the calcite/brine interface. Generally, the addition of alkaline drives the zeta-potentials towards more negative values. This trend towards negative zeta-potential is confirmed for the Smart Water recipe with the impact being more pronounced for Na2CO3 due to the presence of divalent anion carbonate (CO3)-2. Some discrepancy in the zeta-potential magnitude between the SCM results and experiments is observed at the brine/crude oil interface with the addition of alkali. This discrepancy can be attributed to neglecting the reaction of carboxylic acid groups in the crude oil with strong alkali as NaOH and Na2CO3. The novelty of this work is that it clearly validates the SCM results with experimental zeta-potential data to determine the physicochemical interaction of alkaline chemicals with SmartWater in carbonates. These modeling results provide new insights on defining optimal SmartWater compositions to synergize with alkaline chemicals to further improve oil recovery in carbonate reservoirs.

Water chemistry and light effects on survival of hatching salmonids in spring channels

This study informs the restoration and development of salmonid fisheries and aquaculture facilities regarding water quality and light effects on hatching survival in spring channels. Brook trout Salvelinus fontinalis eggs were hatched in springs from karst and silica-clastic aquifers to determine whether survival was affected by water quality in differing geological areas. Nitrogen gas saturation (N2) was highest in karst springs and impacted survival, with a negative relationship between N2 and survival during hatching (> 110% N2 corresponded to 70.5% survival). A multiple regression model was developed to predict survival that included N2, acid neutralizing capacity (ANC), and light intensity (Light) following the equation: In a follow-up experiment, brook trout eggs were fertilized and hatched in hatching boxes in high and low levels of ultraviolet light (UV), fluorescent light, and complete darkness to test the effects of UV and light intensity on survival. Logistic regression was used to model the probability of mortality as a function of UV-B intensity. Results indicated freshly fertilized eggs were more severely impacted by light and UV than post-eyed eggs, and both UV and fluorescent light treatments experienced high mortality compared to the treatment in complete darkness. Karst springs with intermediate concentrations of calcium and increased ANC provide improved water quality for salmonids as compared to silica-clastic aquifers; however, high N2 can have negative effects on survival which, could be overcome by aeration within spring channels. Furthermore, using advanced aquaculture techniques, it may be possible to develop a brood stock that is resistant to the effects of N2. Effects of UV and light intensity pose additional challenges at early life stages for salmonids which, can be overcome by shading hatch boxes in the spring channel.

A Damage Constitutive Model of Rock under Hydrochemical Cyclic Invasion

In order to analyze the stability of water‐related materials, the deterioration and damage of rock strength due to circulating water intrusion in an open tailings pond were studied. Uniaxial compression tests were carried out for rocks under different hydrochemical environments and varying numbers of invasion cycles. Results show that, with increasing number of cycle times, rock peak strength and elastic modulus gradually decrease and the acidity and alkalinity of the soaking solution also degrades rock strength. The curve of the number of cycles, acidity, alkalinity, peak strength, and elastic modulus is fit numerically. Based on the principle of damage mechanics, a hydraulic‐chemistry‐mechanics (HCM) coupling damage variable is defined. Based on the theory of microbody strength distribution, the constitutive equation for rock damage under the coupled effect of water chemistry and cyclic water invasion is established. The results verify the validity of the established damage constitutive model.

Linking pore scale mechanisms with macroscopic to core scale effects in controlled ionic composition low salinity waterflooding processes

The controlled ionic composition low salinity waterflooding processes through tuning of salinity and ionic composition are lately becoming popular for oil recovery in carbonates. Most of the experimental work reported in this area has been limited to macroscopic and core scale measurements and these results consensually pointed out wettability alteration towards water-wet state to be the main recovery mechanism. It is widely believed that wettability is the macroscopic to core scale effect and the link between such effects with molecular scale interactions and phenomena occurring at both carbonate-oil/brine and oil-brine interfaces is not yet well understood. The current study aims to address this knowledge gap by acquiring data on various crude oil/brine/carbonate and crude oil-brine physicochemical interactions using several macroscopic, pore, and core scale experimental techniques. These techniques include contact angle, zeta potential, cryo-broad ion beam scanning electron microscope (BIB-SEM), sum frequency generation (SFG) spectroscopy, and core flooding relative permeabilities. Both high salinity water (HSW) and a controlled ionic composition low salinity water (CICLSW) containing sufficient amount of three key ions (sulfates, magnesium, and calcium) are used to delineate water chemistry effects on resulting physicochemical interactions and changes occurring at carbonate-oil/brine and oil-brine interfaces.The macroscopic contact angle data showed strongly oil-wet behavior with HSW and favorable wettability alterations towards water-wet conditions with CICLSW. The opposing polarity of zeta potentials is observed at calcite/brine and oil-brine interfaces with HSW, which can collapse the thin water film and cause the direct contact of crude oil on to the rock surface to result in oil-wetness. In contrast, CICLSW showed increasingly negative zeta potentials at oil/brine interface and the polarity reversal to negative zeta potentials across calcite/brine interface to stabilize the water-film on the rock surface and subsequently render water-wet conditions. The cryo-BIB-SEM imaging showed trapping of oil ganglia in larger pores and relatively less contact of crude oil with carbonate surface for CICLSW flooded sample. The phase distributions in the sample further confirmed less amount of oil trapped in carbonate pores, which provides a clear indication of CICLSW effect on wettability alteration and better oil mobilization in carbonates. It is also understood from sum frequency generation spectroscopy CH3/CH2 stretching results that CICLSW increased the conformation order of hydrocarbon chains to enhance the interactions at thin interfaces and ultimately alter the wettability. Significant increase in the intensities of free OH stretches and hydrogen bonding are observed at oil/water interface with CICLSW. Such result provides a direct indication that dissolved salt ions displace some water molecules at the interface, resulting in reduced free OH bond densities to correlate well with zeta potential drop observed in HSW. The shifts in relative permeability curves obtained by history matching the coreflood experimental data also confirmed the favorable effect of CICLSW in altering the wettability towards water-wet conditions. This study thereby establishes a good agreement between macroscopic to core scale effects and pore scale interactions occurring at carbonate-oil/brine and oil-brine interfaces to clearly demonstrate the beneficial effects of CICLSW on wettability alteration and oil recovery in carbonates.

Analysis of pedotransfer functions to predict the effects of salinity and sodicity on saturated hydraulic conductivity of soils

Soil sodicity and salinity are global issues associated with irrigated and non-irrigated land management. The combination of high sodium adsorption ratio (SAR) and low electrical conductivity (EC) of the soil solution decreases the saturated hydraulic conductivity of soils. Unfortunately, there have been few attempts to model the changes in saturated hydraulic conductivity in response to EC and SAR. The objectives of this study was to analyze previously developed functions to predict changes in saturated hydraulic conductivity (Ksat) with EC and SAR and to develop new simple functions to predict changes in Ksat with EC and SAR. The performance of previously developed functions were analyzed on 10 different soils. New pedotransfer functions (PTFs) were developed to predict the effects of EC and SAR on relative saturated hydraulic conductivity. The developed PTFs were able to predict the changes in relative Ksat with a geometric root mean squared error (GMRMSE) of 1.80 compared to 3.38 cm day−1 from the semiempirical function used as a module implemented by the Hydrus hydrological modeling application. A PTF was developed to predict the change in relative saturated hydraulic conductivity in soils with swelling clay minerals that does not require X-ray diffraction to quantify clay mineralogy and has the same prediction parameters used for every soil. The developed PTF can easily be used by agricultural and irrigation managers to predict the effects of irrigation water chemistry on relative saturated hydraulic conductivity.

Geosynthetic clay liners: Perceptions and misconceptions

The behaviour of geosynthetic clay liners (GCLs) as part of a physical-environmental system is examined. Consideration is given to: (a) both the physical and hydraulic interactions with the materials, and the chemical interactions with the fluids, above and below the liner, (b) time-dependent changes in the materials, (c) heat generated from the material to be contained, as well as (d) the climatic conditions both during construction and during service. This paper explores some common perceptions about GCL behaviour and then examines the misconceptions that can arise and their implications. It demonstrates how what may first appear obvious is not always as one expects and that more is not always better. It discusses: (i) the pore structure of a GCL, (ii) the dependency of the water retention curve of the GCL on its structure, bentonite particle sizes and applied stress, (iii) the effect of the subgrade pore water chemistry, (iv) the mineralogy of the subgrade, and (v) thermal effects. The desirability of a GCL being reasonably well-hydrated before being permeated is examined. The critical size of needle-punch bundles at which preferential flow can increase hydraulic conductivity by orders of magnitude is illustrated. The dependency of self-healing of holes on the interaction between GCL and subgrade is discussed. Finally, the transmissivity of the geomembrane/GCL interface is shown to be a function of GCL and geomembrane characteristics and to be poorly correlated with GCL hydraulic conductivity.

CRUD deposition in accelerated high-temperature water: Investigation on the effect of substrate material and water chemistry

Deposition of corrosion products (CRUD) on micro-orifice specimens under accelerated flow conditions was investigated in high-temperature water on several substrate materials (SS 304L, Titanium, Alloy 690, Zirlo and magnesia stabilised Zirconia) and water chemistries (0–2 ppm of Li, 0–2.5 ppm of H2). Regardless of the substrate material, no significant differences in radial CRUD build-up were observed in high purity water (0 ppm of Li and either 0 or 2.5 ppm of H2). Conversely, in lithiated water (2 ppm of lithium and 2.5 ppm of H2), the CRUD surface build-up was dependent on the oxide electrical conductivity, which in turn depends on the substrate material. In fact, no build-up occurred on Zirconia and only a minor deposition on Zirlo. The deposition mechanism was ascribed to be dominated by particulate deposition at neutral pH where magnetite solubility is the highest. Conversely, crystalline build-up induced by electrokinetic activity played an important role at alkaline pH where oxide solubility was the lowest.

Effects of calcium availability on growth of larval Lake Sturgeon

A variety of environmental factors are known to influence growth rate and survival of larval fish. The effects of water chemistry, such as calcium hardness of freshwater systems, have been reasonably well-described in teleosts in the early life stages. However, the Lake Sturgeon, Acipenser fulvescens, is unusual in the conjunction of high calcium demand for growth in early life (as in all vertebrate animals), but low internal calcium reserves due to relatively few bony structures, especially in early life. This study reared Lake Sturgeon from hatch until after first feeding in 0.1, 0.2 and 1.5 mM [Ca2+]. No differences were observed between rearing environments in hatching success or survival. Fish reared in the lowest [Ca2+] demonstrated earlier significant increases in wet weight and total length, and absorbed yolk at a faster rate. Fish in all treatments accumulated Na+ and Cl− throughout the pre-feeding stages and continued to increase whole-body [NaCl] in the calcium-limited water after feeding. Continued growth of fish in the lowest calcium concentration was significantly impacted as the fish grew, suggesting that water chemistry was an important influence on developmental progression, and therefore, factors relevant to long-term survival such as condition and available time for feeding onset to occur.

Effect of soil biology and pore water chemistry on a lakebed sediment

This paper attempts to explain how a normally consolidated lakebed sediment can have an undrained strength ratio of approximately unity, when the lithic component of the sediment is less than 3% by volume. The structured clay framework, coupled with sensitivity measurements of the sediment, show that the structure retains a very high strength in a remoulded state. Close examination of the sediment indicates a significant microfossil presence. When considered together with the depositional environment and local water chemistry, this suggests that the soil strength arises from a structural matrix of biofilm adhering to the clay and microfossil particles, which is enhanced by cross-linking due to the presence of multi-valent cations in the local water. Laboratory-scale piezocone, piezoball and T-bar penetrometer tests show that the strength and consolidation characteristics can be significantly altered by changes in the pore water chemistry, an observation that should be considered in geotechnical design for such soils.

Impact of water chemistry, shelf-life, and regeneration in the removal of different chemical and biological contaminants in water by a model Polymeric Graphene Oxide Nanocomposite Membrane Coating

The present study aims to investigate the impact of water chemistry, shelf-life and regeneration of a previously developed chitosan (CS)-polyethyleneimine (PEI)-graphene oxide (GO) nanocomposite membrane coating. Several studies have shown the development of coatings with multifuctionality in DI water but have negleted the effects of water chemistry, shelf-life and chemical regeneration of these nanocomposite coatings for the simultaneous removal of different biological and chemical water contaminants. This nanocomposite was selected for this investigation since it showed a broad removal capability. This nanocomposite showed removals of Cr(VI), Cu(II), and Pb(II) over 90% at 1 ppm initial concentration and nitrate >75% at 20 ppm initial concentration under DI water. Furthermore, the coated filters were effective in removing >3 logs of E. coli K12, B. subtilis, and P. aeruginosa. The integrity and performance of the modified filters were investigated against a wide range of water chemistries with different pH values, salinity, and total hardness. For water chemistries with pH 4–9, salinity 50–1000 ppm, and total hardness of 50–500 ppm as CaCO3, at least one tested contaminant showed similar percentage removals indicating the potential use of the modified filters in these large ranges of water chemistry conditions. Based on that, the filters were used to treat representative samples of wastewater and seawater. The coated filters were able to remove suspended particles, bacteria, and heavy metals effectively. Later the potential for regeneration and the shelf-life of the coated filters were also investigated. For the regeneration, only 0.1 M HCl was able to desorb up to 40% of the adsorbed heavy metal, indicating that the filter can be partially regenerated. Accelerated experiments of shelf-life demonstrated that the modified filters lose their optimum performance around 9–12 months, indicating their potential for short-term storage without any specific preservation conditions.

Effect of water chemistry on the composition of oxides formed on stainless steel surfaces in light water reactors

Results of first-principles calculations have been combined with thermochemical data to evaluate the free energies of formation and the equilibrium composition of Cr-containing nickel ferrite spinel in contact with aqueous solution. Under conditions of solid-liquid equilibrium, with temperature, pH, and concentration of aqueous cations (Ni2+, Fe2+/3+, Cr3+) that are characteristic to operating light water reactors (LWRs), Cr is incorporated at the octahedral site of the spinel up to 12–14 at. %. The effects of temperature, pH, and concentration of aqueous species on the spinel composition are discussed.

Electro-kinetic induced wettability alteration in carbonates: Tailored water chemistry and alkali effects

The injection of optimized water in terms of desired salinity range and ionic composition into a reservoir to enhance oil recovery is widely known as SmartWater flooding. The synergistic effects of different SmartWater brines with alkali on wettability alteration of carbonates is investigated in this study by measuring the ζ-potentials at calcite/brine and oil/brine interfaces.The ζ-potential at calcite/brine/oil interfaces indicate that a higher concentration of sulfates is necessary to result in a favorable wettability alteration. Both alkalis (NaOH and Na2CO3) increase the negative ζ-potential at the two interfaces for low salinity Na2SO4 brine. A slight increase in negative charge is observed at the two interfaces using NaCl brine with Na2CO3 alkali while there is no much change in ζ-potentials with alkali in SmartWater (10-times reduced salinity seawater). Sodium carbonate effects on the ζ-potential of calcite is more pronounced when compared to NaOH due to the availability of carbonate ions as excess potential determining ions. The surface complexation modeling results quantitatively agree with the experimental data at the calcite/brine interface. For the oil/brine interface, a reasonable match is obtained and further calibration of carboxylic acid group and nitrogen based crude oil reactions is recommended to improve these predictions.These results indicate that Na2SO4 brine is highly suitable for alkaline-assisted water-flooding processes in carbonates. The negligible impact of adding alkali on measured dielectric constant as well as strong agreement obtained between the polarity of ζ-potentials at both calcite/brine and oil/brine interfaces with contact angle results confirm the robustness of the reported experimental ζ-potential values.

Factors affecting MeHg bioaccumulation in stream biota: the role of dissolved organic carbon and diet

The bioaccumulation of the neurotoxin methylmercury (MeHg) in freshwater ecosystems is thought to be mediated by both water chemistry (e.g., dissolved organic carbon [DOC] and dissolved mercury [Hg]) and diet (e.g., trophic position and diet composition). Hg in small streams is of particular interest given their role as a link between terrestrial and aquatic processes. Terrestrial processes determine the quantity and quality of streamwater DOC, which in turn influence the quantity and bioavailability of dissolved MeHg. To better understand the effects of water chemistry and diet on Hg bioaccumulation in stream biota, we measured DOC and dissolved Hg in stream water and mercury concentration in three benthic invertebrate taxa and three fish species across up to 12 tributary streams in a forested watershed in New Hampshire, USA. As expected, dissolved total mercury (THg) and MeHg concentrations increased linearly with DOC. However, mercury concentrations in fish and invertebrates varied non-linearly, with maximum bioaccumulation at intermediate DOC concentrations, which suggests that MeHg bioavailability may be reduced at high levels of DOC. Further, MeHg and THg concentrations in invertebrates and fish, respectively, increased with δ15N (suggesting trophic position) but were not associated with δ13C. These results show that even though MeHg in water is strongly determined by DOC concentrations, mercury bioaccumulation in stream food webs is the result of both MeHg availability in stream water and trophic position.

Effect of Water Chemistry on Antimony Removal by Chemical Coagulation: Implications of ζ-Potential and Size of Precipitates.

The process of coagulation and precipitation affect the fate and mobility of antimony (Sb) species in drinking water. Moreover, the solubility and physico-chemical properties of the precipitates may be affected by the media chemistry. Accordingly, the present study aimed to investigate the removal of Sb(III, V) species by ferric chloride coagulation under various water chemistry influences with a particular focus on the role of the properties of the precipitates. The results indicated that the amount of Sb(III) removed increased with increasing solution pH, showing the insignificant effects of the hydrodynamic diameter (HDD) and ζ-potential of the precipitates. However, no Sb(V) removal occurred at alkaline pH values, while a highly negative ζ-potential and the complete dissolution of precipitates were observed in the aqueous solution. The solution pH was also useful in determining the dominant coagulation mechanisms, such as co-precipitation and adsorption. The Fe solubility substantially affects the Sb removal at a certain pH range, while the HDD of the precipitates plays an insignificant role in Sb removal. The presence of divalent cations brings the ζ-potential of the precipitates close to point of zero charge (pzc), thus enhancing the Sb(V) removal at alkaline pH conditions. Pronounced adverse effects of humic acid were observed on Sb removal, ζ-potential and HDD of the precipitates. In general, this study may provide critical information to a wide group of researchers dealing with environmental protection from heavy metal pollution.