Ion Adsorption Method Research Articles

Construction of ZnxCdyS with a 3D Hierarchical Structure for Enhanced Photocatalytic Hydrogen Production from Water Splitting.

The ZnxCdyS has been proven to have unique photoelectric properties, but its synthesis method and photocatalytic water cracking performance need to be further improved. In this paper, Cd-MOF@ZIF-8 with a MOF-on-MOF (MOF = metal-organic framework) structure was prepared by a simple ion adsorption method. Then, a CdS/ZnxCdyS heterojunction with a 3D hierarchical structure was formed by solvothermal sulfidation. The prepared catalysts with different Zn/Cd ratios show an improved hydrogen production performance for photocatalytic water splitting, and the hydrogen evolution rate of Zn1Cd1S can reach up to 29.2 mmol·g-1·h-1. The excellent photocatalytic activity not only benefits from ZnxCdyS strong light conversion ability but also is closely related to the hierarchical structure and large specific surface area. A type II heterojunction also plays an important role in the spatial separation of photogenerated carriers. This paper provides a simple and feasible idea for the synthesis of a photocatalyst with a large specific surface area using a MOF-on-MOF synthesis strategy.

Assessment of Heavy Metal Bioaccumulation in Freshwater Fish Species: Implications for Ecosystem Health and Human Well-being

This research article investigates the bioaccumulation of heavy metals in freshwater fish species from Tekrial Lake, Kamareddy, Thimmakpally Lake, Kamareddy, and Sriram Sagar Project, Nizamabad. The study focuses on Labeo rohita, Catla catla, and Channa punctata as model species to assess the effects of heavy metals, namely zinc(Zn), lead(Pb), ferrous(Fe), and manganese(Mg) on their vital organs including liver, gills, and muscles. Several experiments were conducted to evaluate the levels of heavy metal accumulation in fish tissues using advanced analytical techniques (Atomic Absorption Spectrometer(AAS),Inductively Coupled Plasma Mass Spectrometry). The results indicate a concerning presence of these heavy metals in the examined fish species, suggesting a potential threat to the aquatic ecosystem and human health through fish consumption. Furthermore, this study proposes effective methods to alleviate heavy metal contamination in freshwater fish. The recommended approaches include ion exchange, adsorption, reverse osmosis, and solvent extraction methods. These techniques show promising potential in removing heavy metals from fish tissues and restoring the ecological balance of freshwater ecosystems. Overall, this research sheds light on the alarming bioaccumulation of heavy metals in freshwater fish and emphasizes the detrimental effects on organ function. The proposed remediation strategies provide practical solutions for the mitigation of heavy metal pollution, ensuring sustainable aquatic environments and safeguarding human well-being.

Effect of Acidification on Clay Minerals and Surface Properties of Brown Soil

Globally, soil acidification is becoming a serious environmental and ecological concern, posing a major threat to ecosystem functions and services. In order to clarifying the acidification mechanism, evaluating acidification risk, and reconditioning soil acidification, the effects of acidification on clay mineral composition and soil surface properties should be evaluated. In this study, the surface charge, specific surface area (SSA), species and content of clay minerals were investigated using the ion adsorption method, methylene blue method, and X-ray diffraction (XRD) for brown soil samples, which collected from Muping, Shandong Province, China. The results showed that the clay mineral species and content varied with the degree of acidification. A small amount of montmorillonite was found in weakly acidic soils, and gibbsite was found in strongly acidic soils. Furthermore, although illite, kaolinite, vermiculite, and chlorite were commonly found in soils with different acidification degrees, their content differed. The negative charge (CEC8.2), permanent negative charge (CECP), variable negative charge (CECV), and SSA values decreased with increasing acidification, while anion exchange capacity values (AEC) decreased. The change of CECV was caused by soil organic matter, and the change of CECP was caused by illite content, which accounted for the largest proportion in clay minerals of brown soil.

Sub-nanometer Ru clusters on Sm2O3 obtained from a room temperature ion adsorption method for ammonia synthesis

Highly dispersed Ru clusters on a Sm2O3 catalyst has been successfully prepared by a green ion adsorption method. The surface Sm–H species can promote dissociation of nitrogen over Ru clusters and lead to a much enhanced activity for ammonia synthesis.

Synthesis of novel Mg–Al–Fe-type hydrotalcite with various Mg/Al/Fe ratios and its selective adsorption of As(V) from water

Arsenic is present both in groundwater and wastewater, and arsenic-contaminated water causes environmental pollution and serious health disorders, even at exposure to very low concentrations. Therefore, adsorption methods are attracting interest owing to their simple operation and low cost. It is crucial to develop inexpensive and effective adsorption technologies for removing As(V) from aqueous solutions. In this study, we synthesized novel Mg/Al/Fe (MAF) hydrotalcites at various ratios and evaluated the characteristics of MAF and As(V) ion adsorption capability. Physicochemical properties of MAF were characterized using X-ray diffraction, scanning electron microscopy, or fluoride ion adsorption method, whereas surface binding energy of MAF was measured using an XPS (spectroscopy system by X-ray photoelectron). Adsorption capabilities of MAF were evaluated by examining the effects of various metal adsorbate solution, multiple mixed adsorbate solution, solution pH, and treatment time, and assaying the Langmuir-adsorption and kinetics. MAF had high As(V) adsorption capacity; the amount of As(V) adsorption on MAF-2 was greater than other adsorbents, with selective As(V) adsorption capacity in multiple component solutions. Adsorption isotherm data were fitted using Freundlich and Langmuir models and adsorption dynamics were described by a pseudo-second-order model. A positive linear relationship was observed between the chloride ion eluted from MAF-2 and amount of As(V) ion adsorbed using MAF-2 (r ≥ 0.96). This indicates that the As(V) ion adsorption mechanism involves electrostatic attraction, surface inner-sphere complex formation, and ion exchange between As(V) and hydroxide ions, suggesting that in multiple metal ion mixed liquid phase, MAF-2 is useful for selective and effective adsorption of As(V) ion from arsenic polluted waters.

Highly efficient and stable photocatalytic properties of CdS/FeS nanocomposites

CdS/FeS nanocomposites were successfully synthesized via a liquid-phase thermal decomposition of a single precursor and an ion adsorption method.

Novel method of constructing CdS/ZnS heterojunction for high performance and stable photocatalytic activity

A series of CdS/ZnS heterojunction nanocomposites with different contents of CdS were successfully synthesized through liquid-phase thermal decomposition of a single precursor and ion adsorption method. The structures and properties of these nanocomposites were characterized by XRD, SEM, TEM, ultraviolet visible diffuse reflectance spectrum, electrochemical workstation and photodegradation test. Therefore, the influences of different contents of CdS on the photocatalytic performance of as-prepared samples were demonstrated explicitly. The CdS/ZnS (7:1) nanocomposite exhibited the highest photocatalytic efficiency when exposed to ultraviolet light for 35 min, the degradation efficiencies of rhodamine B (RhB) and methylene blue reached 96.1% and 99.6%, respectively, which is higher than other reported CdS/ZnS based photocatalysts. Moreover, with a 10-cycle test of the degradation of RhB under natural light, the degradation efficiency remained around 96%, showing the desirable photocatalytic stability of CdS/ZnS (7:1) nanocomposite. The approach provides new possibility to produce other metal sulfide nanocomposites.

A general strategy to fabricate soft magnetic CuFe2O4@SiO2 nanofibrous membranes as efficient and recyclable Fenton-like catalysts

Fenton or Fenton-like technique, as one of the advanced oxidation processes, plays a significant role in the removal of non-easily degradable organic pollutants; however, most of such catalysts are fragile with poor structural integrity under large deformation, thereby restricting their wide applications. Herein, soft copper ferrite nanostructures functionalized silica nanofibrous membranes (CuFe2O4@SNM) were fabricated through a novel strategy with the combination of in-situ dopamine polymerization, ion adsorption, and cohesive precipitation method. Benefiting from the high metallic ion adsorption capacity of polydopamine together with the rapid co-precipitation of adsorbed ions on fiber surface in alkaline solution, the membranes possessed homogenously distributed nanostructured CuFe2O4, large specific surface area, and high pore volume, which are a benefit for the improvement of Fenton-like catalytic activity towards organic pollutants decomposition. The resultant soft CuFe2O4@SNM provided favorable catalytic performance towards organic pollutants with a relatively high degradation degree of 96% in 20 min, a fast removal rate of 0.148 min−1, and outstanding recyclability. The successful preparation of such fascinating ceramic nanofibrous membranes would provide a reference for further exploitation of new type Fenton or Fenton-like catalysts with outstanding softness towards wastewater purification.

Synthesis of CdS/ZnO Hybrid Nanoarchitectured Films with Visible Photocatalytic Activity

Abstract A spin-coating method has been employed to prepare crystalline nanostructured zinc oxide (ZnO) thin films. The CdS nanoparticles are then deposited on the surface via a successive ion adsorption and reaction (SILAR) method. Three different concentrations (15, 30, and 50 mM) are used to investigate the effect of various CdS loading on the photocatalytic activity of the hybrid ZnO-CdS hybrid thin films. The transparent crack-free thin films possess fine nanostructures on the top surface, with a fine dispersion of CdS nanoparticles. The highest photocatalytic activity is realized when the concentration is 30 mM. ZnO-CdS hybrid thin films with high surface area, crystalline wall, and low band gap have a great potential as a high-performance material for absorption and degradation of harmful dye molecules such as methylene blue (MB).

Surface-adsorbed ions on TiO2 nanosheets for selective photocatalytic CO2 reduction

A method based on the adsorption of ions on the surface of two-dimensional (2D) nanosheets has been developed for photocatalytic CO2 reduction. Isolated Bi ions, confined on the surface of TiO2 nanosheets using a simple ionic adsorption method facilitate the formation of a built-in electric field that effectively promotes charge carrier separation. This leads to an improved performance of the photocatalytic CO2 reduction process with the preferred conversion to CH4. The proposed surface ion-adsorption method is expected to provide an effective approach for the design of highly efficient photocatalytic systems. These findings could be very valuable in photocatalytic CO2 reduction applications.

Determination of point of zero charge of natural organic materials.

This study evaluates different methods to determine points of zero charge (PZCs) on five organic materials, namely maple sawdust, wood ash, peat moss, compost, and brown algae, used for the passive treatment of contaminated neutral drainage effluents. The PZC provides important information about metal sorption mechanisms. Three methods were used: (1) the salt addition method, measuring the PZC; (2) the zeta potential method, measuring the isoelectric point (IEP); (3) the ion adsorption method, measuring the point of zero net charge (PZNC). Natural kaolinite and synthetic goethite were also tested with both the salt addition and the ion adsorption methods in order to validate experimental protocols. Results obtained from the salt addition method in 0.05M NaNO3 were the following: 4.72 ± 0.06 (maple sawdust), 9.50 ± 0.07 (wood ash), 3.42 ± 0.03 (peat moss), 7.68 ± 0.01 (green compost), and 6.06 ± 0.11 (brown algae). Both the ion adsorption and the zeta potential methods failed to give points of zero charge for these substrates. The PZC of kaolinite (3.01 ± 0.03) was similar to the PZNC (2.9-3.4) and fell within the range of values reported in the literature (2.7-4.1). As for the goethite, the PZC (10.9± 0.05) was slightly higher than the PZNC (9.0-9.4). The salt addition method has been found appropriate and convenient to determine the PZC of natural organic substrates.

Increasing of Photocatalytic Performance of TiO2 Nanotubes by Doping AgS and CdS

Highly ordered titanium nanotubes (TiO2 NTs) photocatalyst was prepared by the anodic oxidation method, and AgS, CdS, and AgS/CdS nanoparticles were doped on the surface of TiO2 NTs by the successive ion adsorption and reaction (SILAR) method. The photocatalysts were characterized by SEM, EDS, XRD, and potentiostat system. The SEM and EDS analyses respectively show that the average outer diameter of prepared photocatalysts is in the range of 50–120 nm, and the presence of Ti, O, Ag, and Cd is successfully proved. The photocatalytic properties of TiO2 NTs and doped TiO2 NTs were studied by measuring the degradation of Methylene Blue (MB) solution. The experimental results show that AgS/CdS/TiO2 photocatalyst exhibited most efficient photocatalytic activity with 340 µA/cm2 photocurrent value. AgS/CdS/TiO2 NTs photocatalyst shows up to 22.20% higher than TiO2 NTs, 16.42% higher than CdS/TiO2 NTs, and 4.3% higher than AgS/TiO2 NTs.

Nitrogen and fluorine dual-doped porous graphene-nanosheets as efficient metal-free electrocatalysts for hydrogen-evolution in acidic media

Nitrogen and fluorine dual-doped porous graphene-nanosheets (NFPGNS) with pyridinic N doped rich configurations have been synthesized by a simple ion adsorption and chemical-etching method.

Synthesis and characterization of Ag@polycarbazole nanoparticles using different oxidants and their dispersion behavior

AbstractAg nanoparticles (NPs) encapsulated by polycarbazole (PCz) have been synthesized using ion adsorption method. The PCz synthesis around Ag NPs has been performed by adsorbing Ag+1and Fe+3oxidants onto Ag NPs, which initiated surface polymerization and thus, Ag NPs@PCz nanocomposite has been synthesized. The morphology of pure NPs and composite NPs was characterized by TEM which also elucidated the effect of oxidant on the core NPs, beside their morphologies and phase contrasts of metal NPs and polymer. The polymer around the surface of core NPs was characterized by FT-IR which proved that PCz was the organic phase of the composite NPs. UV-Vis spectroscopy has been employed to study surface plasmon resonance (SPR) of pure NPs and composite of NP which demonstrated that SPR of core NPs remained preserved after coating with the polymer. Furthermore, Zeta Sizer Nano series has been applied to analyze the dispersion behavior of pure NPs and composite NPs which displayed the greatly improved dispersion behavior of the composite NPs as compared to pure Ag NPs. Therefore, our study proved helpful to analyze the suitability of metal oxidants for PCz based nanocomposite synthesis and determination of their optical and dispersion behavior.

Fluorine-Doped and Partially Oxidized Tantalum Carbides as Nonprecious Metal Electrocatalysts for Methanol Oxidation Reaction in Acidic Media.

A nonprecious metal electrocatalyst based on fluorine-doped tantalum carbide with an oxidative surface on graphitized carbon (TaCx FyOz/(g)C) is developed by using a simple one-pot in situ ion exchange and adsorption method, and the TaCxFyOz/(g)C shows superior performance and durability for methanol oxidation reaction and extreme tolerance to CO poisoning in acidic media.

Effect of ageing on surface charge characteristics and adsorption behaviour of cadmium and arsenate in two contrasting soils amended with biochar

Biochar has been recognised as an effective amendment for the remediation of contaminated soils; however, there is limited knowledge on the effects of biochar ageing in soil on its adsorption behaviour for cationic and anionic species. Biochars are considered to develop negative charge from oxidation with ageing, which may create additional interaction mechanisms for adsorption processes. In the present study, surface charge characteristics and cadmium (Cd) and arsenate (AsO43–) adsorption behaviour of aged biochar were investigated in two soils with variable charge, an Oxisol and an Inceptisol, by comparing (i) unamended soils, and soils amended with (ii) fresh biochar (450°C) and (iii) biochar (450°C) aged for 12 months, applied at a rate of 2% w/w. Surface charge characteristics were assessed using the ‘index’ ion adsorption method, with a LiCl electrolyte. Batch adsorption studies were conducted using fresh and aged soil–biochar mixtures. In contrast to previous studies, the results provided no evidence of an increase in cation exchange capacity as a consequence of biochar ageing. There was an increase in Cd adsorption in the presence of aged biochar in both soil types compared with unamended soils and soils amended with fresh biochar. Results also indicated an increase in AsO43– adsorption in the Inceptisol amended with aged biochar, whereas a decrease in AsO43– adsorption was observed in the Oxisol amended with aged biochar. Overall, the study has highlighted that adsorption behaviour of aged biochar varies depending on the ion it interacts with, soil properties and solution pH.

DEVELOPMENT OF GROUND ENVIRONMENT IMPROVEMENT AND RESTORATION USING THE ROTARY CRUSHING AND DIFFUSIVE MIXING METHOD AS WELL AS ION ADSORPTION METHOD

Lowlands are easily concentrated by effects of water and soil pollution. There is a demand for the development of technology that can both restore the ground environment and improve soft ground. The authors implemented testing used a rotary crushing and diffusive mixing (referred to hereafter as RCDM) method and an ion adsorption method (Nano-size inorganic Layered Double Hydroxide - NLDH - method) for the purpose of developing technology that can restore the ground environment and improve soft ground. These examples are believed to show the broad applicability of both methods.

Supported Noble Metals on Hydrogen‐Treated TiO2 Nanotube Arrays as Highly Ordered Electrodes for Fuel Cells

Hydrogen-treated TiO2 nanotube (H-TNT) arrays serve as highly ordered nanostructured electrode supports, which are able to significantly improve the electrochemical performance and durability of fuel cells. The electrical conductivity of H-TNTs increases by approximately one order of magnitude in comparison to air-treated TNTs. The increase in the number of oxygen vacancies and hydroxyl groups on the H-TNTs help to anchor a greater number of Pt atoms during Pt electrodeposition. The H-TNTs are pretreated by using a successive ion adsorption and reaction (SIAR) method that enhances the loading and dispersion of Pt catalysts when electrodeposited. In the SIAR method a Pd activator can be used to provide uniform nucleation sites for Pt and leads to increased Pt loading on the H-TNTs. Furthermore, fabricated Pt nanoparticles with a diameter of 3.4 nm are located uniformly around the pretreated H-TNT support. The as-prepared and highly ordered electrodes exhibit excellent stability during accelerated durability tests, particularly for the H-TNT-loaded Pt catalysts that have been annealed in ultrahigh purity H2 for a second time. There is minimal decrease in the electrochemical surface area of the as-prepared electrode after 1000 cycles compared to a 68 % decrease for the commercial JM 20 % Pt/C electrode after 800 cycles. X-ray photoelectron spectroscopy shows that after the H-TNT-loaded Pt catalysts are annealed in H2 for the second time, the strong metal-support interaction between the H-TNTs and the Pt catalysts enhances the electrochemical stability of the electrodes. Fuel-cell testing shows that the power density reaches a maximum of 500 mWcm(-2) when this highly ordered electrode is used as the anode. When used as the cathode in a fuel cell with extra-low Pt loading, the new electrode generates a specific power density of 2.68 kWg(Pt) (-1) . It is indicated that H-TNT arrays, which have highly ordered nanostructures, could be used as ordered electrode supports.

Surface charge properties of kaolinite from Thai soils

Kaolinite is the major clay mineral in many Thai soils and the charge characteristics of soil kaolinites have not been properly evaluated. Soil samples from sub-soil horizons of fourteen Oxisols and Ultisols from Thailand were taken for this study. Clay fractions were separated from the soils, and free iron oxides and organic matter were removed to obtain soil kaolinites. Surface charge properties of soil kaolinites and a reference kaolinite (KGa-2) were evaluated by various procedures. Permanent negative charge (−σp) was determined by cesium adsorption method. Point of zero charge (PZC) was measured by ion adsorption, potentiometric titration and electrophoretic mobility methods. X-ray diffraction analysis showed that kaolinites isolated from the Thai soils contain traces to small amounts of quartz, anatase, gibbsite, hydroxy-Al interlayered vermiculite (HIV) and illite. The value of −σp of soil kaolinites varied between 34.9 and 145.3mmolc kg−1; excluding a few anomalous values for the kaolinites with impurities of 2:1 clay minerals, soil kaolinites have an average −σp of 52mmolc kg−1. The −σp on soil kaolinites was positively correlated with the specific surface area (SSA) of the samples. All kaolinites exhibited increasing negative charge and decreasing positive charge with increasing equilibrium solution pH confirming the presence of variable charge on the mineral surface. The PZNC values of soil kaolinites varies from 2.1–3.1, except for two samples where it could not determined as the CEC values were greater than the AEC values at all pH values. Potentiometric titration curves for all kaolinites exhibited variable net proton charge (ΔH−ΔOH or σH) with changing equilibrium solution pH from 2 to 10. The PZSE values were slightly higher than the PZNC values of the soil kaolinites, and varied between 2.3 and 2.9. The zeta potential of all kaolinites became more negative with increasing solution pH (2 to 6) but not low enough to reach a positive value for all but one soil kaolinites; hence the IEP of soil kaolinites could not be obtained. The PZC of kaolinite from Thai soils are at lower pH than the natural pH of these soils, thus soil kaolinites carry a net negative charge under natural conditions and they have some limited ability to adsorb cations. Changes in soil pH from soil acidification, liming or addition of any other amendments or practices can substantially change the cation- or anion-exchange capacity of soil kaolinites, which may influence the availability of nutrient elements in the soils.

Preparation and Antibacterial Activity of Al<sub>2</sub>O<sub>3</sub>-ZrO<sub>2</sub> Carrying Ag<sup>+</sup>

A group of new composite antibacterial agent was prepared by ion adsorption method, in which silver ion is the main active ingredient, with alumina and zirconia as the carriers. The influence of mixing time, content of zirconia, silver ion content and calcination temperature on the antibacterial properties of the composite powder are discussed in this paper. The results show that when the content of ZrO2 is 4%, Ag+ content is 4%，mixing temperature is 70°C，mixing time is 4h, the composite antibacterial agent has a good property. ZrO2 can be loaded in the large hole of Al2O3 as a second carrier; it can keep a larger surface area-based carrier, suitable pore structure, and also play an important role on antibacterial properties at high temperature.