Competitive Adsorption Effects Research Articles

Amino/MnO2 combined modified biochar for enhancing Pb2+ and Cd2+ removal and mechanisms from aqueous solution

Heavy metals from aqueous solutions tend to pose toxicity to the environment, hence it is urgent to treat this pollution. Current studies have exhibited the adsorption capacity of original biochar for Pb2+ and Cd2+ in water, while effective methods were lacking to enhance its adsorption capacity and alleviate competitive adsorption. In this study, MnO2 and amino group combined modification was proposed to improve the Pb2+ and Cd2+ adsorption capacity of rice straw-derived biochar (MNBC) in water. The adsorption performances and mechanisms of MNBC were obtained from batch experiments, several characterizations, and DFT calculation. The results found that modified methods rose the variety of functional groups variety and improved the pore structure of biochar. Maximum removal rates for Pb2+ and Cd2+ were 96.18% and 64.26% and still reached 87.6% and 54.4% after four cycles in single Pb2+ or Cd2+ system. Cation exchange as well as electrostatic attraction might the main adsorption mechanism in the Pb2+ and Cd2+ adsorption process. In binary system, theoretical calculation exhibited that electron cloud neared Pb was more possible to transfer with adsorbent than that of Cd, which was accordance to the results of competitive adsorption. The p orbital of O atom in MnO2 and N orbital atom in amino groups could hybridize with d orbital of Cd and Pb, which effectively reduced the effect of competitive adsorption. Overall, this study proved removal prospect of MNBC for Pb2+ and Cd2+ and its highly efficient and stable in application.

Adsorption of fluoride ion on Al/La modified acidified attapulgite composite materials

This study developed a novel fluoride ion adsorbent material (Al/La-A) for efficient removal of fluoride ions in water. The crystal structure, elemental composition, surface morphology, specific surface area, thermal stability and surface electronegativity before and after modification were explored using FTIR, XRD, XPS, SEM-EDS, BET, TG-DSC, and zeta potential measurements. Results showed that the fluoride ion adsorption capacity of Al/La-A reached 130.42 mg/g, with the surface area increasing from 65.66 m2/g to 111.68 m2/g, respectively, compared to unmodified attapulgite. Al/La-A maintained excellent fluoride ion removal performance over a wide pH range, with the best adsorption at pH 2. Coexisting ion experiments indicated weak competitive adsorption effects of Cl-, SO42-, and HCO3–, with fluoride ion adsorption remaining above 100 mg/g in the presence of different concentrations of coexisting anions. After 5 adsorption–desorption cycles, Al/La-A exhibited strong adsorption capacity and reusability. The fitting of Langmuir adsorption model and pseudo-second-order kinetic model to the adsorption of fluoride ions on Al/La-A indicated that the adsorption of fluoride ions on Al/La-A was primarily monolayer chemical adsorption. The adsorption mechanism of fluoride ions involved electrostatic interactions, ion exchange, and coordination complexation. This study provides a new research approach for the optimal utilization of attapulgite-based adsorbent materials and the efficient removal of fluoride-containing wastewater.

Metal oxide modified MCM-41 on simultaneous removal of HF and HCl: Experimental and theoretical studies

To address the issue of harmful gases Hydrogen fluoride (HF) and hydrogen chloride (HCl) in metallurgical waste gas, this study utilized metal oxide modified molecular sieve (MCM-41) for their simultaneous removal. The adsorption and removal of HF and HCl are mainly influenced by alkaline sites and pore structure, with alkaline sites having a greater impact. MgO affects the alkaline site strength and pore structure, thereby facilitating the removal of HF and HCl. On the surface of the adsorbent, HF and HCl react to form MgF2 and MgCl2, which gradually reduces the adsorbent's performance. HF and HCl have a higher adsorption strength on the MgO surface, and the H…O interaction causes a more stable adsorption configuration. There is a competitive adsorption effect between HF and HCl, with HF having a preference for adsorbing on the MgO surface over HCl. The adsorption energies of HF and HCl are unlimited by adsorption effects. When the O atom in MgO is replaced by HF and HCl, Mg-F bonds, Mg-Cl bonds, and H-O bonds are formed, resulting in the formation of MgF2, MgCl2, and H2O. HF is easier to prioritize removal than HCl

Molecular simulation of competitive adsorption of CO2/N2/O2 gas in bituminous coal

The main cause of coal spontaneous combustion is the oxidation and temperature rise of coal. Injecting composite inert gas for fire prevention and extinguishing is one of the important methods to prevent coal spontaneous combustion. A large number of studies have macroscopically investigated the fire prevention and extinguishing effects of CO2/N2 and their synergistic actions. However, there is currently a lack of research at the molecular level on the competitive adsorption mechanism between mixed inert gases (CO2, N2) and O2 molecules in coal. Therefore, this study conducted adsorption experiments using Qian Yingzi(QYZ) bituminous coal and compared them with the simulation data of the Wiser coal model to verify the reliability of the Wiser model. Subsequently, employing grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) methods, the competitive adsorption behavior of different proportions of binary mixed component gases (CO2/O2, CO2/N2, O2/N2) at a temperature of 303.15 K was investigated from five perspectives: adsorption capacity, adsorption selectivity coefficient, potential energy distribution, competitive adsorption heat, and interaction energy. The results indicate that among the competitive component gases, CO2 exhibits the strongest adsorption effect on the entire system, which is closely correlated with the distribution range of adsorption energy sites. The adsorption heat and adsorption amount of CO2 consistently exhibit a negative correlation, whereas the relationship between the adsorption heat of N2 and O2 and the adsorption amount shows a positive correlation. Their adsorption capacities depend on the pressure and the proportion of the two gases. Based on the isothermal adsorption curve of CO2/N2, it is recommended that the gas pressure during actual inert gas injection be less than 2.5 MPa. Under this pressure, the competitive adsorption effect is no longer significant, providing a certain theoretical basis for high-pressure injection. Moreover, the preliminary determination of the optimal injection ratio range is from 4:6–3:7. Furthermore, a systematic logical framework for selecting underground inert gas composition is proposed, and an underground mobile inert gas infusion process is adopted. The actual gas composition for infusion is determined based on cost factors in practical engineering. The research results can provide guidance for the selection of gas injection parameters for mixed inert gas fire prevention and extinguishing in goaf.

Simultaneous Removal of Pesticides Mixture and Natural Organic Matter from Surface Waters by Nitric and Chlorosulfonic Acid Functionalized Powdered Activated Carbon

AbstractBACKGROUNDSeveral studies have addressed the adsorption of pesticides such as alachlor, acetochlor, metolachlor, and fenthion from water and wastewater, yet the interaction of these compounds with natural organic matter (NOM) complicates their effective removal due to competitive adsorption effects. This study aims to fill this gap by exploring the efficacy of nitric acid and chlorosulfonic acid‐modified activated carbons in removing both pesticides and NOM under realistic environmental conditions.RESULTSModifications using nitric acid and chlorosulfonic acid significantly improved the pesticide removal capabilities of Norit SX F Cat (AC1) adsorbents. While both the original and chlorosulfonic acid‐modified adsorbents showed comparable efficacy in pesticide removal, nitric acid‐modified AC Puriss (AC2) adsorbents were less effective. Remarkably, a 100 mg/L dose of both original and modified powdered activated carbons (PACs) removed over 98% of all four pesticides from water samples. Additionally, a lower 25 mg/L dose effectively achieved similar removal rates, demonstrating their utility as feasible options for water treatment.CONCLUSIONModifying powdered activated carbons with nitric acid and chlorosulfonic acid has been proven to enhance their structural and adsorptive properties significantly. These modifications led to improved pesticide removal efficiencies, particularly with the chlorosulfonic acid‐modified PACs, which demonstrated superior performance in adsorption tests. The study also highlighted the competitive adsorption posed by low‐molecular‐weight organic substances in water, which compete with pesticides for active adsorption sites.This article is protected by copyright. All rights reserved.

Statistical physics investigation on the simultaneous adsorption mechanism of Cd2+ and Pb2+ on amino functionalized activated carbon derived from coal gasification fine slag

In this study, a novel surface amino-functionalized activated carbon (T-AC) was synthesized from coal gasification fine slag (CGFS) and used as an adsorbent for heavy metal ions. T-AC exhibits excellent adsorption capacity for Cd2+ and Pb2+. The adsorption process of Cd2+ and Pb2+ onto T-AC was found to be spontaneous. The dominant adsorption process was chemisorption, primarily involving chelation and covalent bonding. In binary systems, as the initial concentration increases, the independent adsorption effect of Pb2+ and Cd2+ gradually becomes a competitive adsorption effect. Statistical physical models revealed that the adsorption of T-AC for Cd2+ and Pb2+ in single systems followed a multi-molecular adsorption process, whereas in binary systems, it involved a multi-anchorage process. The adsorption capacity was primarily influenced by the number of ions attached to the receptor sites and the density of the adsorbent receptor sites. Moreover, elevating temperature enhanced the thermal movement of heavy metal ions within the pore structure of the adsorbent, reducing their tendency to aggregate at the active sites. This work provides insights into the microscopic-level adsorption process of heavy metal ions by carbon-based materials and contributed to understand of the adsorption behavior.

Hydrogen Flux Inhibition of Pd-Ru Membranes under Exposure to NH3.

The hydrogen flux inhibition of Pd-Ru membranes under exposure to 1-10% NH3 at 673-773 K was investigated. The Pd-Ru membranes were characterized by XRD, SEM, XPS, and hydrogen permeation tests. The results show that when exposed to 1-10% NH3 at 723 K for 6 h, the hydrogen flux of Pd-Ru membranes sharply decreases by 15-33%, and the decline in hydrogen flux becomes more significant with increasing temperatures. After the removal of 1-10% NH3, 100% recovery of hydrogen flux is observed. XPS results show that nitrogenous species appear on the membrane surface after NH3 exposure, and the hydrogen flux inhibition may be related to the competitive adsorption of nitrogenous species. By comparing the hydrogen flux of Pd-Ru membranes exposed to 10% NH3 with 10% N2, it is indicated that the rapid decrease in hydrogen flux is due to the concentration polarization and competitive adsorption of nitrogenous species. The competitive adsorption effect is attenuated, while the concentration polarization effect becomes more pronounced with increasing temperature.

Recovery mechanisms of shale oil by CO2 injection in organic and inorganic nanopores from molecular perspective

CO2 injection is the feasible method to enhance shale oil recovery and has attracted extensive attention in recent years. Since shale reservoir has omnipresent nanoscale pores, understanding the underlying CO2-EOR mechanisms at the nanoscale is of critical importance. In this work, we study the structural and dynamic properties of CO2/nC8 systems in organic kerogen and inorganic quartz nanopores by molecular dynamic simulation and clarify the dominant EOR mechanisms of CO2 injection in various mineral nanopores. We find a large positive slip velocity occurs when single-phase nC8 flows in quartz nanopore while it is no-slip boundary condition in kerogen nanopore. The CO2-regulated nC8 in quartz nanopore is the joint effect of slip, competitive adsorption and viscosity reduction. In the first stage, CO2 extracts the first adsorption layer of nC8 by competitive adsorption and forms a CO2 film on the quartz surface. The CO2 film reduces the slip velocity between nC8 and quartz surface and weakens the nC8 flow capacity. After CO2 adsorption is saturated, the CO2 mixes with nC8 in all flow regions and the effective viscosity of nC8 starts decreasing at this stage. The flow capacity of nC8 rises dramatically due to the viscosity reduction mechanism of CO2. In kerogen nanopore, it is no-slip boundary condition and CO2 mixes with nC8 in all flow regions directly instead of preferably adsorbed on the surface. Viscosity reduction is the dominant mechanism to affect nC8 flow behavior and nC8 flow capacity is enhanced monotonically as CO2 injection. Our study advances the understanding of the recovery mechanisms of shale oil by CO2 injection on nanoscale and provides the theoretical foundation for the optimization of CO2-EOR in shale oil reservoirs.

Sustainable triethylenetetramine modified sulfonated graphene oxide/chitosan composite for enhanced adsorption of Pb(II), Cd(II), and Ni(II) ions

A novel sulfonated group and triethylenetetramine modified GO/chitosan (GO-CS) adsorbent (T-SGO-CS) was successfully prepared and utilized for the adsorption of heavy metal ions from single-metal, binary-metal, and ternary-metal solutions. In a single system, the adsorption capacity was 312.28 mg/g for Pb2+, 260.52 mg/g for Cd2+, and 84.61 mg/g for Ni2+, whereas, Adsorption of Pb(II), Cd(II), and Ni(II) in binary and ternary systems was systematically studied. In tertiary systems, the effect of competitive adsorption was more pronounced. In addition, T-SGO-CS exhibited a high adsorption capacity and was recyclable for Pb2+, Cd2+, and Ni2+. T-SGO-CS is a novel and highly efficient adsorbent for omnidirectionally enhancing the adsorption of Pb2+, Cd2+, and Ni2+, as demonstrated by these results. Therefore, T-SGO-CS could be investigated as a potential new material for future applications in heavy metal removal.

Analysis of colloidal activated carbon alternatives for in situ remediation of a large PFAS plume and source area

AbstractThis study evaluated optimal locations for in situ remediation of per‐ and poly‐fluoroalkyl substances (PFAS) in groundwater with colloidal activated carbon (CAC). New Freundlich isotherms for PFAS adsorption to CAC were estimated to illustrate the effect of competitive adsorption with dissolved organic carbon and other PFAS in a groundwater sample. A hypothetical model scenario was constructed based on source area characteristics similar to a site impacted by aqueous film forming foam in South Dakota. Modeling indicates that, even with high PFAS concentrations, CAC would still be capable of maintaining concentrations below proposed maximum contaminant levels in the adsorption zone for at least 30–40 years. Two‐dimensional areal modeling indicates that the future breakthrough of PFAS is likely to occur in the localized core of the plume, and that the corresponding future reinjection of CAC will only need to be conducted over a smaller portion of the original injection footprint. The benefits of implementing a phased remedial approach at PFAS sites are discussed. Source area and mid‐plume CAC treatments are shown to be ineffective at attenuating PFAS concentrations at the downgradient property boundary within a reasonable timeframe when PFAS travel time is relatively slow. Among the CAC alternatives evaluated here, a downgradient CAC permeable reactive barrier has the best performance with respect to protecting downgradient receptors.

Exploring the effects of interactions between nonylphenol ethoxylate and ionic surfactants on interfacial and foaming properties

Nonylphenol ethoxylate (NPE-9) is a widely recognized non-ionic surfactant that finds extensive applications in various industries, including detergency, emulsification, and agriculture. Combining NPE-9 with an ionic surfactant reflects an inexpensive and highly promising approach for enhancing the efficacy of NPE-9. This study explores the molecular interactions between NPE-9 and ionic surfactants (SDS and CTAB) and examines the impact of these interactions on interfacial properties and foaming. The micellization parameters, including the critical micelle concentration (CMC), degree of counterion binding (β), degree of counterion dissociation (α), and change in free energy of micellization (ΔGmic), were investigated for sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) in the presence and absence of NPE-9, using conductometric measurements. The combined effect of NPE-9 and an ionic surfactant resulted in a synergistic interaction, reducing the CMC of the ionic surfactant, and promoting the formation of micelles. The interaction between NPE-9 and ionic surfactants at the air/water interface was investigated using surface tension measurements. The interfacial properties improved through the competitive adsorption and synergistic effect observed between NPE-9 and an ionic surfactant. In this context, the surface tension data of NPE-9 is utilized to calculate interfacial parameters, including maximum surface excess concentration (Γmax), minimum area per molecule (Amin), and surface effectiveness (π). Adding SDS and CTAB to NPE-9 solutions resulted in a notable enhancement in foamability and foam stability. The utilization of various techniques consistently produced improvements in the interfacial and foaming properties of NPE-9.

To explore the remediation mechanism and effect of biochar and KH2PO4 on soils contaminated with heavy metal ions Hg2+, Cd2+ and Pb2+

In this study, wheat straw-derived biochar was prepared by setting a temperature of 400 °C under an oxygen-limited environment using the technique of “programmed temperature increase control”. The results showed that the biochar had a strong adsorption capacity for Hg2+, Cd2+ and Pb2+ ions, and the adsorption pattern was Hg2+>Cd2+>Pb2+. There was a competitive adsorption effect during the coexistence of the ions. The results of the soil remediation tests showed that the effects of biochar on soil physicochemical properties and heavy metal distribution was generally greater than those of KH2PO4 in single or combined contaminated soil. The adsorption effect of heavy metal ions in soil was the best in the case of mixed additions. The results can provide a scientific basis for the treatment of heavy metal contaminated soil with wheat straw biochar in the future.

Gas permeation properties of bridged-type organosilica membranes at extremely low temperatures and the application to oxygen separation

A bridged-type organosilica, bis(triethoxysilyl)methane (BTESM) membrane was evaluated in detail for single-gas permeation at temperatures ranging from −130 to −200 °C, and for binary (O2/He, O2/N2) separation at 30 and -115 °C, respectively. The permeance of He, Ar, and N2 demonstrated a trend of activated diffusion as permeance increased with an increase in the temperature; O2 permeance, however, reached its maximum value at about −80 °C. O2 permeance increased with a decrease in the temperature (30 to −80 °C), and permeance then gradually decreased (−80 to −130 °C), which demonstrates surface diffusion. In the case of O2/He binary separation, both O2 and He permeated according to molecular sieving at 30 °C, but at −115 °C, O2/He selectivity was enhanced approximately 10-fold due to permeation blockage by adsorbed O2. On the other hand, in the case of O2/N2 binary separation at −115 °C, the effect of permeation blocking by adsorbed O2 permeance was lessened due to the effect of competitive adsorption, which translated to a level of O2/N2 selectivity that was only 1.5-fold higher than that at 30 °C.

Modified superhydrophobic magnetic Fe3O4 nanoparticles for removal of microplastics in liquid foods

Microplastics (MPs) stemming from plastic products have attracted wide attention around the world due to their stealth, persistence and potential threat to humans. It is essential to remove MPs by using eco-friendly and effective methods. In this study, to remove MPs, we proposed to prepare Fe3O4 superhydrophobic magnetic adsorbents (Fe3O4@Cn, n = 12, 14, 16, 18) modified by different saturated fatty acids (C12, C14, C16, C18) by liquid phase deposition method. Transmission electron microscope, atomic force microscopy, Fourier transform infrared spectroscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, vibrating sample magnetometry and nitrogen adsorption measurements were applied to characterize the morphology, functional groups, crystalline structures of Fe3O4@Cn as well as its magnetic properties and pore size distribution. It was shown that Fe3O4@Cn exhibited the characteristics of magnetic materials with superhydrophobic properties and thus possessed the ability to separate oil and water. During the removal of MPs in five liquid food systems, Fe3O4@C12 exhibited 92.89 % adsorption efficiency, which was ascribed to the electrostatic and chemical bonding interactions between MPs and Fe3O4@Cn, as suggested by density functional theory (DFT) calculations. In addition, the presence of organic matter in water can decrease the removal efficiency of Fe3O4@Cn due to the competitive adsorption effect. Simulation by Langmuir isotherm model suggested that Fe3O4@C12 displayed the greatest adsorption efficiency for Polystyrene (PS) (809.29 mg/g), which is higher than that of Fe3O4@C14, Fe3O4@C16, and Fe3O4@C18. In addition, Langmuir adsorption isotherm and Gaussian calculations suggested that PS was removed by Fe3O4@C12 through an exothermic reaction controlled by chemisorption. Overall, these results indicated that superhydrophobic magnetic materials prepared in this study show high potential for removing MPs in aqueous systems due to their low costs, good environmental friendliness, and high removal performance.

The Blue Tansy Essential Oil–Petra/Osiris/Molinspiration (POM) Analyses and Prediction of Its Corrosion Inhibition Performance Based on Chemical Composition

Sustainable materials encompass a diverse range of substances used in both consumer and industrial domains. These materials are sourced in quantities that safeguard non-renewable resources and environmental equilibrium, with a focus on bio-based alternatives derived from plants. This study investigates the corrosion inhibition potential of two distinct Blue Tansy essential oils (BTES 1 and BTES 2) with varying chemical compositions. Corrosion resistance for mild steel in 1 M HCl environment was assessed using weight loss and Potentiodynamic polarization techniques. The evaluation of BTES 1 and BTES 2 revealed compelling insights. Notably, their inhibition efficiency exhibited an intriguing, damped oscillation pattern with fluctuating concentrations. Remarkably, at 0.5 g/L concentration, BTES 1 achieved an impressive 80% inhibition, while BTES 2 demonstrated a substantial 70% inhibition at 2.5 g/L. This behavior stems from intricate interactions among active compounds, leading to protective film formation and competitive adsorption effects. Importantly, congruence between weight loss measurements and potentiodynamic polarization curves fortified the reliability of outcomes. The study also confirmed BTES as a mixed-type inhibitor, as indicated by polarization curves. Furthermore, Petra/Osiris/Molinspiration (POM) analyses were conducted to unravel molecule interactions, elucidate toxicity risks, and assess bioactivity scores. This comprehensive exploration sheds light on the interplay between sustainable materials, corrosion inhibition efficacy, and complex molecular dynamics, enhancing our understanding of environmentally conscious corrosion prevention strategies.

Phase transformation of nanoscale zero-valent iron and concurrent arsenite sequestration under oxic water environment

Nanoscale zero-valent iron (nZVI) may partially or completely transform to iron (hydr)oxides when it is used to remove arsenite [As(Ⅲ)]. It is necessary to explore the dynamic phase transformation of nZVI and concurrent arsenic valent changes since reactivity is relevant to the exiting species. In this study, X-ray photoelectron spectra (XPS), X-ray diffraction (XRD), Raman spectrum, and scanning electron microscope (SEM) were used to probe the phase transformation of nZVI under the varied simulated polluted water, including different As(Ⅲ) concentration, pH, and co-existing anions. The mainly final product of nZVI corrosion was lepidocrocite (γ-FeOOH) evaluated by XRD. Because of proton release, As(Ⅲ) made more Fe0 corroded in the initial reaction and the corrosion process was faster in the later stage. The formation of iron (hydr)oxides was the main factor affecting the removal of As(Ⅲ) between pH 2–8. And the co-existing anions promoted the corrosion of Fe0, which weakened the negative effect of competitive adsorption on As(Ⅲ) removal to some extent. This research will provide vital information on the evolution and fate of nZVI under environmental conditions, as well as As(Ⅲ) stabilization and mobilization for nZVI treatment system.

Influence of FeCl3/Fe3(PO4)2/CaO in sludge on the migration pattern of heavy metals during coal slime combustion

The influence of minerals (FeCl3, Fe3(PO4)2, CaO) contained in SS(Sewage Sludge) on the migration and mechanism of Pb, As, Cu, Cr, Cd in CS(Coal Slime) during the co-combustion process was studied by electric heating tube furnace. Studies have shown that the interaction of minerals in SS with minerals and heavy metals in CS is an important factor affecting the migration of heavy metals in the co-combustion process of SS-CS. The heavy metals combine to form volatile heavy metal-Cl compounds. Compared with the single combustion of CS, the retention rates of Pb, As, Cu, and Cd are reduced by 89.6%, 45.1%, 70.4%, and 89.2% at 900 °C. When CS is blended with Fe3(PO4)2, Fe3(PO4)2 decomposes a large amount of Fe2O3 and P with the increase of combustion temperature to react with As, Cu, and Cr in CS, which makes the retention rate of the three heavy metals increase by 30.6%, 194.1%, and 1726.4% under the combustion condition of 900 °C compared with CS alone. When CS was burned with CaO, CaO had a competitive adsorption effect on Pb and Cd, which reduced the retention rate of Pb and Cd by 12.2% and 58.2% at 900 °C compared with CS alone. Meanwhile, CaO reacted with As, which increased the retention rate of As by 1.3% and 38.9% at 700 °C and 900 °C.The effects of Cl on the migration of Pb, Cu, Cr, and Cd were stronger than those of CaO and Fe3(PO4)2, and Fe2O3 and CaO had the greatest effect on the sequestration of As.

Effect of competitive adsorption between specialty admixtures and superplasticizer on structural build-up and hardened property of mortar phase of ultra-high-performance concrete

This study aims to enhance structural build-up of ultra-high-performance concrete (UHPC) without influencing the initial flowability, which is critical in repair applications (e.g., use of UHPC in thin bonded overlays for bridge deck rehabilitation). Specialty admixtures, such as a viscosity-modifying admixture (VMA), have been used to enhance the structural build-up at rest. However, the use of specialty admixtures can increase superplasticizer (SP) demand to maintain proper flowability; the synergistic effect of these admixtures on structural build-up is not well understood as the coupled admixture content can reverse the net effect on yield stress, viscosity, and thixotropy. In this study, VMAs including welan gum (WG), diutan gum (DG), and cellulose ether (CE) were used. Styrene-butadiene rubber (SBR) and acrylic ester (AE) latex polymers (LPs) that can enhance structural build-up and bond strength were also incorporated. The competitive adsorption between these specialty admixtures and SP and its effect on structural build-up, early-age hydration, compressive and pull-off strengths, porosity and entrapped air content of UHPC mortar (i.e., without fiber) were systematically investigated. Test results indicated that the incorporation of anionic WG and DG that exhibited high competitive adsorption with SP led to a 275%–450% enhancement in structural build-up despite the 55%–135% increase of SP demand. Such increase was limited to 130% when using CE, SBR, or AE that cannot effectively adsorb onto cement particles in the presence of SP. This was because the high competitive adsorption between specialty admixtures and SP strengthened the particle flocculation and promoted the cement hydration in the first hour; the latter resulted in 20%–40% enhancement in non-reversible component of structural build-up. Furthermore, the use of LP at low and moderate dosages secured high bond strength to normal strength mortar despite 8%–33% decrease in compressive strength given the increased capillary porosity. The use of VMAs increased the entrapped air and resulting 5%–15% lower compressive strength, while the bond strength was not influenced.

Adsorption Characteristics of Arsenic and Cadmium by FeMnNi-LDH Composite Modified by Fulvic Acid and Its Mechanisms

Toxic As(Ⅲ) and Cd(Ⅱ) ions in water can be transferred and enriched into human bodies through the food chain, causing serious health damage at excessive levels. In this study, fulvic acid (FA) was selected as the modifier of iron-manganese-nickel layered double hydroxide (FeMnNi-LDH), and a stable layered composite (FA@FeMnNi-LDH) was prepared using the co-precipitation method, which could adsorb As(Ⅲ) anions and Cd(Ⅱ) cations simultaneously, especially with the higher adsorption capacity of the cation Cd(Ⅱ). Its structure was characterized by XRD, TEM, FT-IR, and XPS, and the adsorption capacity and mechanisms of As(Ⅲ) and Cd(Ⅱ) in water by the composite were also investigated. The results showed that with typical characteristic peaks of layered double hydroxides, the synthesized composite possessed a stable structure, maximum FA loading capacity, and optimal adsorption performance. The adsorption kinetics of As(Ⅲ) and Cd(Ⅱ) conformed to the pseudo-second-order kinetic model, and the adsorption isotherms well-followed the Langmuir model, with the maximum adsorption capacity at 25℃ being 249.60 mg·g-1 for As(Ⅲ) and 156.50 mg·g-1 for Cd(Ⅱ), respectively. The composite exhibited a good adsorption performance on As(Ⅲ) and Cd(Ⅱ) in the range of pH 2-7 and pH 4-7, respectively. The competitive adsorption effect of co-existed anions on As(Ⅲ) showed a sequence of PO43->CO32->NO3-, and that of co-existed cations on Cd(Ⅱ) was Pb2+>Cu2+>K+. The adsorption capacity of As(Ⅲ) and Cd(Ⅱ) decreased with the increase in the concentration of competing ions. The main adsorption mechanism for As(Ⅲ) was ion-exchange occurring in the interlayers of LDH, and that for Cd(Ⅱ) was coordination complexation occurring with the loaded FA, respectively. In conclusion, the prepared FA@FeMnNi-LDH composite material posed a good application prospect for adsorption removal of As(Ⅲ) and Cd(Ⅱ) in water and their toxicity control.

Theoretical study on the interaction between cis-2 bis(benzofuro)[60]fullerene derivative and NO dominated double gas molecule

The interaction between cis-2 bis(benzofuro)[60]fullerene derivative and NO dominated double gas molecule was studied at the 6–311G(d,p) basis set level by density functional theory B3LYP-D3 method. The geometric structures of six interaction systems were optimized, and the optimized configurations were analyzed by electronic properties, infrared chromatography and independent gradient model to reveal the essence of intermolecular interaction. The results shows that NONO2, NON2, NOCO, NOCO2 and NOHCN are co-adsorbed on the surface of the compound in physical form, and the binding energies are −77.62 kJ/mol, −24.24 kJ/mol, −27.43 kJ/mol, −39.28 kJ/mol and −36.29 kJ/mol, respectively. The van der Waals interaction between gas molecules makes the three molecular interaction system have synergistic adsorption or competitive adsorption effect. Among them, the synergistic effect of NONO2 co-adsorption system is the biggest, and there is a strong attraction between NO and NO2 molecules. Compared with the interaction system of single gas molecule with cis-2 bis(benzofuro) [60]fullerene derivative, the interaction intensity of double gas molecule with the derivative is significantly improved.