Adsorption Of Chloride Research Articles

Adsorption of Corrosion Inhibitor 1-Dodecylpyridinium Chloride on Carbon Steel Studied by in Situ AFM and Electrochemical Methods

Corrosion rates are influenced by the formation of inhibitor aggregates at the steel surface. In situ atomic force microscopy (AFM) was used to investigate the adsorbed structures of cationic surfactant 1-dodecylpyridinium chloride (DPC) at a carbon steel surface in relation to its performance as a CO2-corrosion inhibitor. An increase in the water contact-angle in the presence of DPC indicated its adsorption at the steel, and in situ AFM visualization confirmed the formation of DPC aggregates. The aggregates changed from hemispherical to cylindrical shape with increasing DPC concentration in CO2-saturated brine, resulting in a decrease in corrosion rates as determined by electrochemical measurements. For comparison to the aggressive CO2 environment, the inhibition behavior of DPC was monitored in less corrosive N2-saturated solutions. Formation of cylindrical aggregates was quicker, and a lower corrosion rate was observed in brine saturated with N2 compared to CO2.

Zeta potential of limestone in a large range of salinity

Experimental investigations have been conducted to elucidate the variation of the zeta potential (ζ) of limestone in a large range of salinity. The effects of the type and concentration of inorganic salts, the pH, and the adsorption of the oil polar fractions, naphthenic acid and cationic surfactant on the ζ have been investigated in the paper. The results show that the ζ rises toward the positive with the increase of the concentration of inorganic salt, but the increase rate gets very low in the high-concentration brine. The mineral composition of the limestone has also some influence on the ζ. The high pH value results in the large ζ, and the adsorption of oil polar fractions and naphthenic acid is beneficial to the increase of the ζ. However, increasing the salinity reduces the effect of the pH, oil polar fractions and naphthenic acid on the ζ, and the ζ is nearly not affected by the above influencing factor in the formation water (total salinity: 223,802.8mg/L). Among the three surfactants of dodecyl trimethyl ammonium chloride, tetradecyl trimethyl ammonium chloride and octadecyl trimethyl ammonium chloride, the adsorption of octadecyl trimethyl ammonium chloride onto the rock surface is more efficient to increase the ζ, and the more adsorption leads to the higher ζ in the surfactant solutions with the same salinity. The adsorption quantity of octadecyl trimethyl ammonium chloride onto the limestone is the largest when the surfactant concentration is the same, and the high salinity promotes the adsorption of the surfactant onto the limestone. Nevertheless, the ζ decreases rather than rising due to the simultaneous increase of the salinity and surfactant adsorption. The above results indicate that the salinity is the dominant influencing factor on the ζ of the limestone in various conditions, which can be used as theoretical guidance for improved oil recovery in the carbonate reservoir with different salt contents.

Chloride adsorption by calcined layered double hydroxides in hardened Portland cement paste

This study investigated the feasibility of using calcined layered double hydroxides (CLDHs) to prevent chloride-induced deterioration in reinforced concrete. CLDHs not only adsorbed chloride ions in aqueous solution with a memory effect but also had a much higher binding capacity than the original layered double hydroxides (LDHs) in the cement matrix. We investigated this adsorption in hardened cement paste in batch cultures to determine adsorption isotherms. The measured and theoretical binding capacities (153 mg g−1 and 257 mg g−1, respectively) of the CLDHs were comparable to the theoretical capacity of Friedel's salt (2 mol mol−1 or 121 mg g−1), which belongs to the LDH family among cementitious phases. We simulated chloride adsorption by CLDHs through the cement matrix using the Fickian model and compared the simulation result to the X-ray fluorescence (XRF) chlorine map. Based on our results, it is proposed that the adsorption process is governed by the chloride transport through the cement matrix; this process differs from that in an aqueous solution. X-ray diffraction (XRD) analysis showed that the CLDH rebuilds the layered structure in a cementitious environment, thereby demonstrating the feasibility of applying CLDHs to the cement and concrete industries.

The Stoichiometry of Proton, Chloride, and Phthalate Adsorption on Goethite

The adsorption of ions on solid surfaces can be measured in the absence of competing reactions if the background electrolytes are inert or indifferent. The background electrolytes are not necessarily inert or indifferent, particularly if their concentrations are high, which can result from pH adjustments. Therefore, an understanding of the adsorption of ions on solid surfaces should include the potential role of each of the other ions in the system. This study investigated the adsorption of phthalate, an environmentally common ligand, on goethite with concurrent measurements of other ions present in the matrix. Measuring the stoichiometry of all adsorbing ions will identify any coadsorption process present, if any, and also elucidate the net change in surface charge characteristics. The stoichiometry of protons and Cl− ions adsorbing onto the surface of goethite and the stoichiometry of protons and phthalate ions adsorbing onto the same surface with NaCl as the background electrolyte were measured. Proton adsorption data were obtained using the backtitration technique, while Cl− and phthalate adsorption data were obtained by mass balance as a function of pH. The proton/Cl− adsorption stoichiometry is 1:1 and the proton/phthalate adsorption stoichiometry is 2:1. Such stoichiometries imply that the net charge on the surface is neutral. The Cl− and phthalate anions were found to exhibit a competitive reaction with the surface. The surface showed a preference for phthalate at pH values >2.5. The adsorption reactions of cations and anions are tightly intertwined and occur concurrently, and quantifying both of these reactions is needed to fully understand the adsorption processes involved. Accordingly, the adsorption study of specific ions should also include an adsorption study of all the other competitive or coadsorbing ions present.

Adsorption of benzyldimethyldodecylammonium chloride onto stainless steel using the quartz crystal microbalance and the depletion methods: an optimisation study

The adsorption behaviour of benzyldimethyldodecylammonium chloride (C12BDMAC) corrosion inhibitor from aqueous solutions onto a stainless steel surface has been investigated using the quartz crystal microbalance (QCM) technique and the depletion-HPLC method. Three different experimental procedures were used to carry out the adsorption measurements using the QCM. The results revealed that the employed experimental procedure had a marked influence on both of the measured frequency and dissipation energy changes. Additionally, the measured changes in the normalized frequency and dissipation changes were found to be overtone-dependent. The adsorbed amounts determined by QCM were higher than those determined by depletion due to strong contributions from the bulk liquid properties. The direct application of the measured frequency shifts corresponding to the lowest dissipation changes, ΔflowestD, in the Sauerbrey equation was effective in minimising these contributions within an acceptable experimental tolerance. A correction procedure, based on the Kanazawa equation, has been proposed and applied successfully to separate the contribution from the bulk effects to the calculated adsorbed mass. The adsorption isotherms obtained from the corrected frequency shifts and the depletion method were perfectly matched over the whole range of concentrations investigated.

Forming a filter media from zeolite modified with SDBAC for wastewater treatment process

This paper investigates the effects of several parameters (amounts of organic matter, grain size, content of solid phase, stirring rate, and temperature) on the adsorption of stearyl dimethyl benzyl ammonium chloride (SDBAC) in natural zeolite tuff in the process of formation of adsorbents based on organo-zeolite, a potential filter in waste water treatment process. Obtained results show that the most favorable ratio between the amount of SDBAC and zeolites is 50-75 mmol M+/kg. Larger grains have lower zeolite adsorption power of organic cations on the surface of zeolite, while favorable percentage of content of solids in the zeolite suspension is 10-20%. Interference between adsorption of mixture and temperature, especially in volumes of SDBAC lower than 75 mmol M+/kg of zeolite, have no significant impact on adsorption of organic cations on the surface of the zeolite. The obtained results present an initial step for defining the optimal operating parameters for forming adsorbents based on organo-zeolite as a filter potentially utilized in waste water treatment.

高炉スラグセメント硬化体の塩化物イオン吸着能に及ぼすCa溶脱の影響

放射性廃棄物処分施設にコンクリートを使用することが検討されており長期にわたる核種の外部環境への漏洩抑制が期待されている。その際に長期間地下水に曝露することによりセメント硬化体内部からカルシウムが溶脱し吸着量が減少すると考えられる。本研究ではCa溶脱程度に応じた高炉スラグセメント硬化体の塩化物イオン吸着量を実験的に検討し、予測式を構築することで吸着量を定量的に明らかにした。その結果、溶脱によりCa/Si比が低下し高炉スラグセメントにおいてはAl/Si比が増加することにより吸着量に影響を及ぼすことを明らかにした。

Mercuric chloride adsorption on sulfur-containing BC2N nanotube: toward HSAB concept

Electronic sensitivity of pristine and sulfur-containing BC2N nanotubes to mercuric chloride (HgCl2) molecule was investigated by utilizing density functional theory. It was found that HgCl2 is weakly adsorbed on the tube, releasing energy of 6.4–8.1 kcal/mol, and electronic properties of the tube are not significantly changed. To overcome this problem, carbon atoms of the tube were substituted by sulfur atom. Of interest are sulfur derivative functional adsorbents because of their strong affinity toward mercury. This observation may be explained based on the Pearson’s hard–soft acid–base theory. It was demonstrated that the S-doped tube can not only strongly adsorb the HgCl2 molecule, but also may effectively detect its presence due to drastic increment of the tube electrical conductivity.

Investigation on the montmorillonite adsorption of biocidal compounds incorporating thermodynamical-based multicomponent adsorption isotherm

Sublethal concentration of biocides, namely triclosan and benzalkonium chloride, have been known to raise severe environmental problems such as pathogens resistance and the existence of the toxic compounds in reclaimed water. Simple adsorption process of those biocides onto the bentonite modified by dodecyltricetyl ammonium bromide (DTAB) cation, show a remarkable increase on the removal efficiency of triclosan, regardless of the pH value. It was found that organophilic cation facilitates the anchoring of hydrophobic triclosan, but slightly limits the adsorption of benzalkonium chloride by occupying the active cation exchange site in the bentonite structure. Adsorption of a single system can be described properly by Langmuir isotherm equation. Incorporation of the Gibb’s free energy on the affinity constant of the extended Langmuir equation may attribute robust predictive ability on the binary adsorption model.

Comparative study of the adsorption of [formula omitted] and Cl− anions on smooth and rough surfaces of noble metal electrodes by in situ radiotracer thin gap method

The so-called in situ thin gap method for the measurement of the surface excess of the radiolabelled species was originally designed for the application of noble metal electrodes with low surface roughness. Therefore, the observation of adsorbed species containing radioisotopes of high specific activity (i.e., 35S and 14C) was only possible. A recent extension of the original thin gap method to metals with a surface roughness factor higher than 10, however, made it possible to follow the adsorption of species with low specific activity (i.e., 36Cl). Based on the validation of the improved thin gap method (Horváth et al., 2013), this study aims at the comparison of the sulfate/bisulfate and chloride adsorption on both smooth (Pt and Au) and rough (platinized platinum) noble metal electrodes. It was found that the radiation signal of the adsorbed chloride ions can also be detected, and the surface excess of both radiolabelled bisulfate and chloride ions can be measured. The accumulation of the adsorbed species on rough electrodes took place at a much longer time scale than the removal of the same species. No such difference was found for smooth electrodes. The apparent asymmetry in the temporal behaviour of the adsorption and desorption processes on rough electrodes could be understood by the difference in the concentration gradient in the solution near or within the porous structures during the respective processes.

Modeling of Mercuric Chloride Removal by CuCl2-Impregnated Activated Carbon Sorbent in a Fabric Filter

A model for the physical adsorption of mercuric chloride (HgCl2) onto raw activated carbon (AC) and 4 and 10% CuCl2-impregnated activated carbon (CuCl2–AC) sorbents in a fabric filter was studied on the basis of the adsorption equilibrium and kinetics. Sorbent loading, particle size, filtration time, and CuCl2 loading onto AC were found to be the major factors determining a HgCl2 removal efficiency. Although high sorbent loading and small sorbent particle size result in high HgCl2 removal efficiencies, the inlet HgCl2 concentration and superficial gas velocity were found to have little impact on HgCl2 removal. Our operation case study result shows that sorbent injection for a short duration at a high loading followed by the discontinuation of the injection until a cleaning cycle can significantly save a total sorbent amount with high sorbent utilization, while the same amount of HgCl2 is removed. The adsorption of HgCl2 onto raw AC and CuCl2–AC in the filter cake was found to be primarily governed by the ...

Adsorption of benzethonium chloride from aqueous solutions on dispersed adsorbents

The adsorption of benzethonium chloride from aqueous solutions on the surface of finely dispersed particles of aluminum oxide, titanium dioxide, and zirconium dioxide is investigated. The ratio of the amount of adsorbed benzethonium chloride molecules to the amount of surface hydroxyl groups as potential adsorption sites is proposed to be used for characterizing the structure of adsorption layers. It is shown that the formation of supramolecular structures of benzethonium chloride molecules on solid surfaces begins when its concentrations in suspensions is significantly lower than the critical micellization concentration. It is established that benzethonium chloride is adsorbed via simultaneous interaction of the surfactant molecules with the surface hydroxyl groups and hydrophobic interaction of their hydrocarbon tails; the amounts of molecules adsorbed as a result of these interactions depend on both benzethonium chloride concentration in a solution and the density of the hydroxyl groups on an oxide surface.

Adsorption of Benzyldimethylhexadecylammonium Chloride at the Hydrophobic Silica–Water Interface Studied by Total Internal Reflection Raman Spectroscopy: Effects of Silica Surface Properties and Metal Salt Addition

The adsorption of the cationic surfactant benzyldimethylhexadecylammonium (BDMHA(+)) chloride was studied at an octadecyltrichlorosilane (OTS)-monolayer-modified silica-water interface by Raman spectroscopy in total internal reflection (TIR) geometry. The present study demonstrates the capabilities of this spectroscopic technique to evaluate thermodynamic and kinetic BDMHA(+)Cl(-) adsorption properties at the hydrophobic silica surface. The surface coverage of BDMHA(+) decreased by 50% at the hydrophobic OTS-silica surface relative to the surface coverage on bare silica; the dominating driving mechanisms for surfactant adsorption were identified as hydrophobic effects and head group charge screening by the electrolyte counterions. Addition of magnesium metal salt (MgCl2) to the aqueous solution (∼ neutral pH) lowered the surface coverage and moderately increased the Langmuir adsorption constants relative to those of the pure surfactant. These trends were previously observed at the hydrophilic, negatively charged silica surface but with a smaller change in the Gibbs free energy of adsorption at the hydrophobic silica surface. The hydrophobic OTS-silica surface properties resulted in shorter times for the surfactant to reach steady-state adsorption conditions compared to the slow adsorption kinetics previously seen with the surfactant at the hydrophilic surface. Adsorption isotherms, based on Raman signal intensities from spectral analysis, were developed according to the Langmuir adsorption model for the pure surfactant at the OTS-silica-water interface; the modified Langmuir model was applied to the surfactant adsorption in the presence of 5, 10, 50, and 100 mM magnesium chloride. Spectral analysis of the Raman scattering intensities and geometric considerations suggests a hemimicelle-type surface aggregate as the most likely surfactant structure at the OTS-silica surface. The different kinetics observed at the hydrophilic versus the hydrophobic silica surface further indicate that the surface charge and potential influence the surfactant diffusion and kinetic rates of adsorption at the silica-water interface.

Adsorption mechanism of chlorides on carbon nanotubes based on first-principles calculations

The direct adsorption mechanism of chlorides (LiCl, NaCl, KCl, CsCl, MgCl2, CaCl2, SrCl2 and BaCl2) on carbon nanotubes (CNTs) was investigated with first-principles calculations. The dipole moment, the adsorption energy and the Coulomb interaction energy were calculated. The value of the adsorption energy ranges from 0.2 to 0.6eV. Considering the structure change of chlorides before and after adsorption, we find that the adsorption energy, just as the Coulomb energy, is proportional to the ratio of chloride’s dipole moment to the square of adsorption distance. So, we conclude that the direct adsorption of chlorides on CNTs occurs mainly through long-range electrostatic interactions.

Adsorption of vapor-phase elemental mercury (Hg0) and mercury chloride (HgCl2) with innovative composite activated carbons impregnated with Na2S and S0 in different sequences

As powdered activated carbon (PAC) is being widely used for mercury adsorption, its efficiency can be enhanced by sulfur impregnation. In this study, innovative composite PACs impregnated with two sulfur species, vapor-phase elemental sulfur (S0) and aqueous-phase sodium sulfide (Na2S), in different sequences were developed for investigating the removal of gaseous elemental mercury (Hg0) or mercury chloride (HgCl2) with respect to the adsorptive capacities and adsorption rates at different influent Hg0 or HgCl2 concentrations and different adsorption temperatures. The effects of sulfur impregnation on the physicochemical characteristics of the PACs, including specific surface area, volumes of various pore sizes, and sulfur content, were also examined. In the results, the PACs impregnated with aqueous Na2S, followed by the subsequent gaseous Hg0 impregnation exhibited higher adsorptive capacities of both mercury species. At elevated adsorption temperatures (200 and 300°C), the adsorption of Hg0 is more effective onto the surface of the composite sulfur-impregnated PACs, whereas the composite PACs provided elevated capacities for HgCl2 at a lower adsorption temperature (150°C), suggesting possible variation of mercury control strategies under different circumstances. These findings provide insight into the application of this innovative composite PACs for the removal of gaseous Hg0 or HgCl2. Higher adsorptive capacities of Hg0 or HgCl2 compared to those of previous studies were achieved by using the innovative composite sulfur-impregnated activated carbons.

Environmental risk assessment of groundwater quality and treated wastewater reuse on aquifer recharge: a case study in Korba, Tunisia

Water resources associated with the Mediterranean arid to semiarid environment in Tunisia are at risk of degradation in terms of quantity and quality, especially due to groundwater overexploitation. Therefore, the reuse of treated wastewater (TWW) for the artificial recharge of groundwater has been implemented as an alternative, particularly in Korba coastal area of Tunisia. The aim of the current study was to assess the environmental risk of the groundwater quality as well as the reuse of TWW for Korba local aquifer recharge. On one hand, results showed high levels of chloride, ammonia, and sodium adsorption ratio (SAR) in the TWW and high electrical conductivity, nitrate, chloride concentrations, and SAR in groundwater. Heavy metal concentrations were commonly under the detection limit. On the other hand, groundwater was contaminated with pesticides. Environmental risk monitoring of TWW is fundamental to assess its safety reuse on the aquifer recharge and in presenting a coastal barrier against seawater intrusion. Also, it will allow for more effective allocation of resources in future monitoring programs and it can contribute to the environmental management of the treatment plant.

Toxicological characterization of the landfill leachate prior/after chemical and electrochemical treatment: A study on human and plant cells

In this research, toxicological safety of two newly developed methods for the treatment of landfill leachate from the Piškornica (Croatia) sanitary landfill was investigated. Chemical treatment procedure combined chemical precipitation with CaO followed by coagulation with ferric chloride and final adsorption by clinoptilolite. Electrochemical treatment approach included pretreatment with ozone followed by electrooxidation/electrocoagulation and final polishing by microwave irradiation. Cell viability of untreated/treated landfill leachate was examined using fluorescence microscopy. Cytotoxic effect of the original leachate was obtained for both exposure periods (4 and 24h) while treated samples showed no cytotoxic effect even after prolonged exposure time. The potential DNA damage of the untreated/treated landfill leachate was evaluated by the comet assay and cytokinesis-block micronucleus (CBMN) assay using either human or plant cells. The original leachate exhibited significantly higher comet assay parameters compared to negative control after 24h exposure. On the contrary, there was no significant difference between negative control and chemically/electrochemically treated leachate for any of the parameters tested. There was also no significant increase in either CBMN assay parameter compared to the negative control following the exposure of the lymphocytes to the chemically or electrochemically treated landfill leachate for both exposure periods while the original sample showed significantly higher number of micronuclei, nucleoplasmic bridges and nuclear buds for both exposure times. Results suggest that both methods are suitable for the treatment of such complex waste effluent due to high removal efficiency of all measured parameters and toxicological safety of the treated effluent.

Specific Ion Effects at Two Single-Crystal Planes of Sapphire

Experimental results on specific ion effects at the c- and r- single-crystal planes of sapphire obtained by zeta-potential measurements at pH 5.8 are reported. Both crystal planes have negative electrokinetic charge at pH 5.8 and their intrinsic isoelectric points are found close to pH 4. The water structure "making" surface (i.e., r-plane, based on surface diffraction and surface complexation modeling) causes cation specificity in the order Li(+) > Na(+) > K(+) > Rb(+) > Cs(+) in chloride systems while no anion sensitivity occurs in sodium systems (Cl(-), NO3(-), and BrO3(-)) as expected. The cation series concurs with the simple idea of structure making ions being adsorbed more strongly on structure making surfaces and also concurs with the sequence found for particulate alumina for the cation series in nitrate systems. On the structure breaking basal plane (i.e., c-plane, again based on surface diffraction and surface complexation modeling), no cation specific effects are observed in chloride systems, but the structure breaking properties are retrieved in the cation series in nitrate systems. Surprisingly, anion specificity is observed on sapphire-c. Furthermore, the chloride ion shows unexpected behavior that suggests chloride adsorption onto the negatively charged surface. Based on these experimental observations in conjunction with generic results from published MD simulations, the c-plane sapphire aqueous electrolyte interface is a nonpolar surface with negative charge. The nonpolarity finds repercussions in the weak water ordering and the observed ion specific effects. The low isoelectric points of the cuts cannot be explained by the respective surface chemistries of the ideal surfaces. Relation to "inert" surfaces and concomitant dominance of hydroxide ion adsorption is a possible explanation for the low isoelectric points of both cuts. The reported ion specific effects occur at concentrations below 10 mM. Overall, the results support the idea that ion specific effects are largely governed by surface hydration.

Adsorption of the disinfectant benzalkonium chloride on montmorillonite. Synergistic effect in mixture of molecules with different chain lengths

The biocide benzalkonium chloride (BAC) is a mix of cationic alkylbenzyldimethylammonium surfactants having different alkyl chain lengths. A comparative study of adsorption on the phyllosilicate clay montmorillonite of two of these surfactants, with alkyl chains having respectively 12 C atoms (BAC-12) and 14 C atoms (BAC-14), and a mixture of both surfactants is presented in this work. Adsorption isotherms were performed for individual surfactants and for a 1:1 mixture BAC-12+BAC-14. The adsorption was investigated in an ample concentration range that covers almost seven orders of magnitude in concentrations (from 1 nM to 10 mM), range that includes environmentally relevant concentrations. Quantification of BAC was performed by HPLC–UV and LC–MS and the results were completed with powder X-Ray diffraction. The adsorption of both surfactants leads to adsorption isotherms with two well differentiated steps. The first step corresponds almost exclusively to a cation exchange process, and the binding constant is very similar for both surfactants. The second step of the isotherms is observed at higher concentrations and adsorption is mainly driven by lateral interactions between surfactant molecules. The binding constant of this step is larger for BAC-14 than for BAC-12. Adsorption from a BAC-12+BAC-14 mixture shows a synergistic behaviour, possibly due to a better packing arrangement in the interlayer. Calculations show that in natural systems silicate clays are major sorbents of BAC at low concentrations whereas binding to humic acid is predominant at high concentrations.

AuCl3 on polypyrrole-modified carbon nanotubes as acetylene hydrochlorination catalysts

In this study, polypyrrole (PPy) was deposited on the surface of multiwall carbon nanotubes (MWCNTs), and PPy–MWCNTs were used to support the AuCl3 catalyst. Transmission electron microscopy and Fourier-transform infrared spectrometry confirmed the presence of PPy species in AuCl3/PPy–MWCNT catalysts. AuCl3/PPy–MWCNTs displayed enhanced catalytic activity and stability for acetylene hydrochlorination compared to AuCl3/MWCNT. Electron transfer may occur between the N atom of PPy and the Au3+ center, which affects the adsorption of hydrogen chloride during acetylene hydrochlorination.