Chloride Immobilization Research Articles

Roles of wood waste biochar for chloride immobilization in GGBS-blended cement composites

Due to its environmentally friendly features and economic benefits, biochar has garnered increasing attention as a sustainable and carbon-negative material in the construction sector. This study investigated the roles of wood waste biochar in enhancing the chloride immobilization capacity (CIC) of GGBS-blended cement (PG) composites by assessing the chemical chloride immobilization, physical chloride immobilization, and chloride migration resistance. The results indicated an initial increase in the chloride immobilization ratio (CIR) of PG composites, followed by a decrease upon the further increase in biochar dosage. The highest CIR was achieved by PGBC2, containing 2.0 wt% biochar. Microscale characterization revealed that biochar addition increased the formation of Friedel’s salts, thereby augmenting chemical chloride immobilization in the PG composites. Furthermore, biochar addition enhanced the adsorption of calcium ions and provided nucleation sites that supported the continuous hydration reaction, forming more hydration products and reinforcing the physical chloride immobilization. The highest compressive strength and elastic modulus were aligned with the lowest water adsorption and total porosity among all the tested groups, supporting the increased resistance of chloride migration in the PGBC composites. These findings offer novel insights into leveraging wood waste biochar for fortifying the durability of GGBS-blended concrete structures in chloride-rich environments.

Improving sulfate and chloride resistance in eco-friendly marine concrete: Alkali-activated slag system with mineral admixtures

This study investigates the effects of various mineral admixtures, such as fly ash, metakaolin, and limestone powder, on the mechanical, chloride, and sulfate resistance properties of alkali-activated slag (AAS). The resistance of alkali-activated concrete (AAC) to chloride and sulfate is evaluated using the rapid chloride migration (RCM), wetting-drying cycles, SEM and XRD, TG/DTG. The results reveal that introducing fly ash improves workability but degrades the strength and durability of AAS. The 15% slag substitution by metakaolin is recommended to improve durability. Incorporating 15% limestone powder increases the compressive strength and reduces porosity due to filling and nucleation effects. The replacement ratio of 30% for each mineral admixture induces a considerable Ca2+ dilution, resulting in reducing the strength and durability of AAC. Under short-term wetting-drying cycles, the continued hydration of raw materials under MgSO4 erosion and the subsequent production of gypsum, hydrotalcite, and brucite from the matrix initially increase the AAC strength. However, the continued substitution of calcium in the C-(A)-S-H gel by magnesium and precipitation of gypsum under excessive cycles adversely deteriorates the compressive strength. The chloride migration degree in AAC is closely related to the porosity. Although the porous gel N-A-S-H facilitates chlorine migration in accelerated tests, it prevents further chlorine penetration by adsorbing chloride ions in large quantities, exhibiting the dominant effect on chloride immobilization. The formation of Friedel's salt, stemming from the chemical bonding of chloride, is present only in the high-calcium specimen G100 and the highly reactive aluminum specimen G85M15. Improvements in the gel chemistry and porosity are key factors in bolstering the durability of AAC. The findings of this study contribute to advancing the application of eco-friendly AAC in marine environments.

Ag Nanoparticle-Induced Surface Chloride Immobilization Strategy Enables Stable Seawater Electrolysis.

Although hydrogen gas (H2 ) storage might enable offshore renewable energy to be stored at scale, the commercialization of technology for H2 generation by seawater electrolysis depends upon the development of methods that avoid the severe corrosion of anodes by chloride (Cl- ) ions. Here, it is revealed that the stability of an anode used for seawater splitting can be increased by more than an order of magnitude by loading Ag nanoparticles on the catalyst surface. In experiments, an optimized NiFe-layered double hydroxide (LDH)@Ag electrode displays stable operation at 400mA cm-2 in alkaline saline electrolyte and seawater for over 5000 and 2500h, respectively. The impressive long-term durability is more than 20 times that of an unmodified NiFe-LDH anode. Meticulous characterization and simulation reveals that in the presence of an applied electric field, free Cl- ions react with oxidized Ag nanoparticles to form stable AgCl species, giving rise to the formation of a Cl- -free layer near the anode surface. Because of its simplicity and effectiveness, it is anticipated that the proposed strategy to immobilize chloride ions on the surface of an anode has the potential to become a crucial technology to control corrosion during large-scale electrolysis of seawater to produce hydrogen.

Effect of Hydrated Calcium Aluminate Cement on the Chloride Immobilization of Portland Cement Paste

Effect of Hydrated Calcium Aluminate Cement on the Chloride Immobilization of Portland Cement Paste

Evaluation of the Surface Performance of Mortar Matrix Subjected to Sodium Chloride Solution Modified with Hybrid Nanosilica Cement Paste

In order to prolong the service life of cement-based materials subjected to external chloride ion attacks, two kinds of methods, a surface treatment and chloride immobilization, were combined by fabricating a nanosilica-modified cement paste and coating it on mortar samples as a surface treatment material (HSM). The protective effect of the HSM was evaluated according to its surface hardness, and an RCM test was carried out, which indicated that the attached layer could both increase the surface hardness and decrease the chloride diffusion coefficient. Then, the chloride immobilization mechanisms were illustrated in terms of chloride blocking resistance, chemical binding and physical binding X-ray diffraction (XRD), and thermogravimetric/derivative thermogravimetric (TG/DTG) and thermodynamic modeling. The results showed that the hybrid nanomaterials that modified the cementitious surface treatment materials may effectively improve the chloride-resistant property of a matrix with content of no more than 1%. This research outcome could provide evidence that hybrid nanosilica can be applied in surface treatment technology.

Preparation of solid disinfectant for water treatment and mechanism of benzalkonium chloride immobilization on activated carbon

Chlorine disinfection is the most widely used method to inactivate microorganisms in water, however, the byproducts generated after disinfection have a very harmful cumulative effect on human environment. Therefore, a new highly efficient broad-spectrum disinfectant without side-effects is urgently required. Benzalkonium chloride (BAC) can kill bacteria and fungi and inactivate viruses, so it is a dual-function disinfectant. In this paper, BAC molecules were immobilized onto activated carbon (AC), and the mechanism of BAC immobilization was explained at the molecular level. Then, the bactericidal performance of the modified AC was explored. The results showed that AC had a strong adsorption capacity for BAC molecules. The desorption of these BAC molecules from the AC occurred only on the ppm scale. In the immobilization mechanism, the adsorbed BAC molecules agglomerated due to the hydrophobic groups to form large agglomerates. Since the pores of AC are mostly in the shape of ink bottles, it is difficult for these agglomerates to be released from the narrow pore-inlet. The solid disinfectant prepared by fixing different BAC contents in the AC had strong bactericidal performance for Escherichia coli, and the performance was influenced by many factors, including the ability of microorganisms to adsorb onto the BAC-modified AC and the number of free BAC molecules that easily combined with the microorganisms. The bactericidal rate of these solid disinfectants was greater than 95%, and their application to inactivate microorganisms can be used to avoid the disadvantages of chlorine disinfection in water treatment.

Assessment of the In Vivo Release and Biocompatibility of Novel Vesicles Containing Zinc in Rats.

This paper is focused on the in vivo release and biocompatibility evaluation in rats of some novel systems entrapping zinc chloride in lipid vesicles. The particles were prepared by zinc chloride immobilization inside lipid vesicles made using phosphatidylcholine, stabilized with 0.5% chitosan solution, and dialyzed for 10 h to achieve a neutral pH. The submicrometric systems were physico-chemically characterized. White Wistar rats, assigned into four groups of six animals each, were treated orally with a single dose, as follows: Group I (control): deionized water 0.3 mL/100 g body weight; Group II (Zn): 2 mg/kg body weight (kbw) zinc chloride; Group III (LV-Zn): 2 mg/kbw zinc chloride in vesicles; Group IV (LVC-Zn): 2 mg/kbw zinc chloride in vesicles stabilized with chitosan. Haematological, biochemical, and immune parameters were assessed after 24 h and 7 days, and then liver fragments were collected for histopathological examination. The use of zinc submicrometric particles—especially those stabilized with chitosan—showed a delayed zinc release in rats. No substantial changes to blood parameters, plasma biochemical tests, serum complement activity, or peripheral neutrophils phagocytic capacity were noted; moreover, the tested substances did not induce liver architectural disturbances. The obtained systems provided a delayed release of zinc, and showed good biocompatibility in rats.

Effect of Hydrated Calcium Aluminate Cement on the Chloride Immobilization of Portland Cement Paste

Effect of Hydrated Calcium Aluminate Cement on the Chloride Immobilization of Portland Cement Paste

Preparation of ultrafine fly ash by wet grinding and its utilization for immobilizing chloride ions in cement paste

In this study, to promote the chloride binding capacity of coal fired fly ash (RFA) in cementitious materials, wet grinding was employed and ultrafine fly ash (UFA) with D50 = 2.1 μm was prepared; SEM, XRD, TG, FTIR, and XPS were used to evaluate the chemical and physical change in the process of wet grinding. Then, two kinds of binders composed of cement and FA were designed, and the chloride immobilization was comparatively studied in terms of chemical binding, physical binding, and migration resistance. The hydration behavior and hydrates were investigated in terms of TGA, XRD, NMR, and MIP. Results revealed that UFA exhibited higher pozzolanic reactivity due to the increase of specific surface area, destruction of original molecular structure, and exposure of active reaction sites. And chloride immobilization in cement-UFA system was much greater than that in cement-RFA system at ages of 7 d and 28 d. The mechanism behind was discussed in three aspects: (a) chemical binding was promoted because of the more produced chloroaluminates facilitated by the release of aluminum from UFA; (b) physical adsorption was strengthened at 7 d but weakened at 28 d, resulting from the opposite influence on the amount of C-S-H gel at different ages; (c) migration resistance was improved by the reduction of pore volume and the increase in the complexity of pore structure. This investigation provided one new method for processing FA to promote the chloride immobilization of cement-FA system.

Improvement in chloride immobilization of cement-metakaolin system by triisopropanolamine

Metakaolin (MK) is a widely used admixture in chloride immobilization which is conducive to the durability of reinforced concrete. In this study, triisopropanolamine (TIPA) was added into cement-MK system to improve the chloride immobilization by expediting the pozzolanic reaction of MK. The effect of TIPA on hydration of binder composed of 90% Portland cement and 10% MK was investigated, and the hydration behavior was characterized by thermogravimetric analysis, X-ray diffraction, nuclear magnetic resonance spectroscopy, and mercury intrusion porosimetry, based on the evaluation of pozzolanic reaction of MK by ion dissolution. Results indicated that TIPA promoted the hydration of both MK and cement, and chloride immobilization was also improved. The mechanism for the improvement was involved in three aspects: a) TIPA facilitated the dissolution of aluminum from MK to obtain more chloroaluminate salts, strengthening chemical binding; b) TIPA accelerated hydration of cement and MK for more C-S-H gel, conducive to the physical adsorption; c) TIPA increased the amount of hydrates to refine the pore structure, hindering the migration of chloride ion. This investigation provided one new method for improving the pozzolanic reaction of MK to enhance chloride immobilization of cement-MK system.

Mechanical Properties, Microstructure, and Chloride Content of Alkali-Activated Fly Ash Paste Made with Sea Water.

The aim of the present study is to investigate the potential of sea water as a feasible alternative to produce alkali-activated fly ash material. The alkali-activated fly ash binder was fabricated by employing conventional pure water, tap water, and sea water based alkali activating solution. The characteristics of alkali-activated materials were examined by employing compressive strength, mercury intrusion porosimetry, XRD, FT-IR, and 29Si NMR along with ion chromatography for chloride immobilization. The results provided new insights demonstrating that sea water can be effectively used to produce alkali activated fly ash material. The presence of chloride in sea water contributed to increase compressive strength, refine microstructure, and mineralogical characteristics. Furthermore, a higher degree of polymerization on the sea water-based sample was observed by FT-IR and 29Si NMR analysis. However, the higher amount of free chloride ion even after immobilization in sea water-based alkali-activated material, should be considered before application in reinforced structural elements.

Effects of colloidal nano-SiO2 on the immobilization of chloride ions in cement-fly ash system

This paper investigates effect of colloidal nano-SiO2 (CNS) on chloride immobilization of cement-fly ash (FA) system composed of 70% cement and 30% FA from 7 d to 90 d age. The mechanism was revealed in terms of migration resistance, chemical binding, and physical binding; and each aspect was determined with corresponding measurements, including microstructure of hydrates examined by XRD, EDS, TGA and NMR, and pore structure evaluated by MIP. Results reveal that the CNS dosage influenced immobilized chloride ratio (ICR). 0.5% CNS promoted the ICR, while more than 0.5% CNS decreased ICR. The promotion by 0.5% CNS was derived from the refined pore structure and the increased amount of C–S–H gel, which could enhance the migration resistance and physical binding; the decrease by more than 0.5% CNS was because of the reduced amount of chloroaluminates and the decreased Ca/Si ratio, leading to the decline in chemical binding and physical binding. Furthermore, curing age also affected ICR. 28-day ICR was higher than that at 7 d or 90 d. The increase of ICR from 7 d to 28 d was attributed to the refinement of pore structure and the increase in amount of chloroaluminates and C–S–H gel; reduction from 28 d to 90 d age was due to the negative effects including the decrease in content of chloroaluminates and the reduced Ca/Si ratio. The findings are expected to give new insight into the effect of nano-SiO2 on performance of cement-based materials.

Solidification/stabilization of flue gas desulfurization brine and coal fly ash for heavy metals and chloride immobilization: Effects of S/S conditions and zero-valent-iron pretreatment

Effective management of flue-gas-desulfurization (FGD) wastewater and coal-combustion-residues (CCRs) are major challenges in the coal-fired power industry. The zero-liquid-discharge (ZLD) method of combining FGD brines and CCRs in solidification/stabilization (S/S) is promising due to its potential of treating both wastes in the same process. This study evaluated the performance of such a ZLD method for immobilizing heavy metals (Se, As, Cd and Cr) and chloride in FGD wastewater and/or CCRs. Effects of different coal fly ash (bituminous (BCFA) and sub-bituminous (SCFA)), activating agent (Portland cement (PC) and lime) and pretreatment of brines by zero valent iron (ZVI) on the S/S process were evaluated. Short-term and long-term leaching tests were conducted to evaluate performance of the S/S solids in pollutant retainment. The pre-treatment of FGD brine by ZVI enhanced the retainment of heavy metals when BCFA was used, but not when SCFA was used since it already performed quite well without ZVI pretreatment. Quantitative X-ray diffraction and scanning electron microscopy analyses strongly indicated the formation of Friedel’s salt, Ca2Al(OH)6(Cl,OH)·2H2O, is critical in the retainment of heavy metals and chloride. SCFA contained higher lime and reactive aluminate contents than BCFA; thus, S/S solids made with SCFA contained higher amounts of Friedel’s salt.

Effects of amorphous aluminum hydroxide on chloride immobilization in cement-based materials

This study investigated the effects of amorphous aluminum hydroxide (AAH) on chloride ions immobilization ability of cement-based materials. Paste samples with different dosages of AAH were prepared, and the chloride binding capacity was examined. Hydrates at the age of 7 d and 28 d were analyzed by X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), and Nuclear Magnetic Resonance (NMR). Pore structure was also evaluated by mercury intrusion porosity (MIP). Results revealed that addition of AAH retarded the cement hydration, refined the pore structure, and enhanced the immobilization ability of chloride ions in cement-based materials. The increase in immobilized chloride ratios (ICR) was related to three aspects: a) the migration resistance was strengthened by the refined pore structure; b) chemical binding ability was increased because of the increased content of Kuzel’s salt in hydrates; c) the physical adsorption ability was weakened by the reduced amount of C-S-H gel in hydrates due to the retarding effect of AAH.

Chloride immobilization of cement-based material containing nano-Al2O3

The utilization of marine resources in reinforced concrete is severely limited, due to the risk of steel corrosion caused by the introduced chloride. In order to reduce this risk, nano-Al2O3 (NA) was added into cement-based materials system by improving the chloride immobilization. The immobilized chloride ratio (ICR) of the system was evaluated, and the results indicated that the addition of NA could significantly enhance ICR. Based on the results from TG, XRD, 27Al NMR, MIP, 29Si NMR, and EDS, the mechanism behind was discussed from three aspects of chemical binding, migration resistance, and physical adsorption. The reasons for the increased ICR were as follows: a) chemical binding was promoted by increasing the amount of chloroaluminates; b) migration resistance was improved by refining the pore structure; c) physical adsorption, depending on the amount and the Ca/Si ratio of C-S-H gel, was reduced negligibly. These findings can provide guidance for the theoretical study of chloride immobilization and the application of marine resources.

Effect of TIPA on Chloride Immobilization in Cement‐Fly Ash Paste

Utilization of sea sands and coral aggregate for concrete in ocean construction is increasingly attracting the attention all over the world. However, the potential risk of steel corrosion resulting from chloride in these raw materials was one of the most concerned problems. To take this risk into account, chloride transporting to the surface of steel should be hindered. The formation of Friedel’s salt in hydration process is widely accepted as an effective manner for this hindrance. In this study, an attempt to hasten the formation of Friedel’s salt by adding triisopropanolamine (TIPA) was done in the cement‐fly ash system, with intention to chemical bind chloride, and the chloride‐binding capacity at 60 d age was examined. The results show that TIPA can enhance the chloride‐binding capacity of cement‐fly ash paste at 60 d age, and the reason is that the formation of Friedel’s salt can be accelerated with addition of TIPA. The mechanism behind is revealed as follows: on the one hand, the accelerated cement hydration provides more amount of calcium hydroxide to induce the pozzolanic reaction of fly ash, which can hasten the dissolution of aluminum into liquid phase; on the other hand, TIPA can directly hasten the dissolution of aluminum in fly ash, offering more amounts of aluminum in liquid phase. In this case, the aluminum/sulfate (Al/S) ratio was obviously increased, benefiting the formation of Friedel’s salt in hydration products. Such results would expect to provide useful experience to promote the chloride‐binding capacity of cement‐fly ash system.

Some Considerations for Applicability of Seawater as Mixing Water in Concrete

According to the report of the World Meteorological Organization (WMO), more than half of the world’s population will not have enough drinking water by 2025. To save drinking water, use of seawater in the concrete industry seems imperative. In the present study, the possibilities of seawater as a material of concrete are discussed as a result of the literature-based and experimental investigations. From the results of the literature-based study, more than half of the papers collected in this study had positive opinions about concrete mixed with seawater by adding the mineral admixture such as blast furnace slag (BFS). In addition, some results of long-term exposure tests indicated the high possibility of using seawater as a material of concrete. The experimental data obtained in this study indicated that the addition of BFS might contribute significantly to the corrosion resistance of steel bar, because of the low oxygen environment around steel bar and chloride immobilization.

Palladium(II) chemically bonded to silica surface applied to the separation and identification of polycyclic aromatic sulfur heterocycles in heavy oil

Separation of polycyclic aromatic sulfur heterocycles among themselves and also from interferents in petrochemical matrices is a challenging task because of their low concentration, matrix complexity, and also due to the presence of polyaromatic hydrocarbons, as they present similar physico-chemical properties. Therefore, the objective of this work was preparation, characterization, and application of a stationary phase for separation of these compounds in a heavy gas oil sample and their identification by comprehensive two-dimensional gas chromatography. The stationary phase was prepared by grafting mercaptopropyltrimethoxisilane onto a silica surface, followed by palladium(II) chloride immobilization. Elemental analysis, thermogravimetry, nitrogen adsorption-desorption isotherms, infrared analysis, and scanning electron microscopy were performed to characterize this solid phase. Sulfur compounds were separated in an open column packed with the stationary phase and analyzed by comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometric detection. The number of compounds tentatively identified was 314 and their classes were thiophenes, benzotiophenes, dibenzothiophenes, naphthothiophenes, benzonaphthothiophenes, and dinaphthothiophenes. Separation among sulfur compounds and polyaromatic hydrocarbons was successful, which is a difficult goal to achieve with the traditionally employed solid phases. Some recalcitrant compounds (dibenzothiophenes with substituents of two and four carbons) were fully separated and tentatively identified.

Cardiac troponin T detection using polymers coated quartz crystal microbalance as a cost-effective immunosensor

Cardiac troponin T (cTnT) detection has been the focus of increased interest due to its role in myocardial infarction diagnosis. In this study, we report a relatively low coat technique to detect cTnT using a quartz crystal microbalance (QCM) sensor. A sensitive detection is achieved by introducing a QCM surface with a carboxylic polyvinyl chloride immobilization layer. The surface morphologies of this polymer film under varied deposition thickness have been investigated by field emission scanning electron microscopy and atomic force microscopy. A cTnT detection result from a modified QCM surface can be obtained within a short response time by a direct detection of the immunoreaction and a direct conversion of mass accumulation into a frequency shift, representing a measurable electrical signal. The relationship between the cTnT concentration and the response current from a QCM sensor shows detectability at the concentration of cTnT as low as 5 ng/ml.

Stabilization/solidification of petroleum drill cuttings: Leaching studies

This work explores the effectiveness of Portland cement (CEM I), with the addition of high carbon fly ash (HCFA), as a novel binder, for the improvement of leachability-related properties of stabilized/solidified (s/s) petroleum drill cuttings. A factorial design experiment was adopted to investigate the effects of waste-to-binder ratio, HCFA addition, and curing time on leachate pH, acid neutralization capacity (ANC), and metal, chloride and hydrocarbon leaching. The leachate pH and ANC of all products suggested successful formation of a calcium–silicate–hydrate-based matrix with good resistance to acid attack, and little detrimental effect from drill cuttings addition. Leaching of amphoteric metals was significantly affected by pH, which was a function of other studied factors. All studied factors also affected leaching of chloride and hydrocarbons. CEM I, without HCFA addition, was more effective in immobilizing chlorides, but the overall chloride immobilization was poor in all runs. HCFA addition significantly reduced the leaching of hydrocarbons. Comparison of milligram of contaminant leached per kilogram of drill cuttings from the s/s products and untreated drill cuttings provided clear evidence of hydrocarbon and chloride immobilization. This work shows that HCFA improved the immobilization of organic contaminants and may represent an inexpensive binder for stabilization/solidification of organic wastes.