Metals In Aqueous Media Research Articles

Metal-Organic Framework-Based Materials for Heavy Metal Sensing in Aqueous Media

Industrial development leads to an increasing amount of pollutants including heavy metal ions in surface and subsurface waters. For instance, wastewater from battery manufacturing, paint manufacturing or metal plating, contain heavy metals in high concentrations. The heavy metals are typically non-biodegradable and not-easy to excrete. Their presence within the organisms causes damage and failure of different organs. Consequently, the permissible concentrations of heavy metal ions in drinking water set by the World Health Organization are on a ppb level.In this work, electrode materials based on metal-organic frameworks (MOFs) are prepared and studied for sensing of heavy metals in aqueous media. These involved MOFs in their pristine form, composites of pristine MOFs and conducting polymer polyaniline as well as their carbonized derivatives. Cadmium and lead ions were used as model pollutants. Thorough physico-chemical characterization of the prepared materials was done using scanning electron microscopy, Raman spectroscopy, and dynamic light scattering. Electroanalytical performance was scrutinized using anodic stripping voltammetry and correlated with materials’ structural, morphology and textural properties. Limits of detection and sensitivity were determined upon optimization of the experimental conditions to identify the best material. Moreover, materials proved to be suitable for two heavy metal ions sensing in real river samples. Acknowledgments This work was supported by the Science Fund of the Republic of Serbia, grant number 7750219, Advanced Conducting Polymer-Based Materials for Electrochemical Energy Conversion and Storage, Sensors and Environmental Protection-AdConPolyMat (IDEAS programme).

Aerophilic Surfaces for Sustained Corrosion Protection of Metals Underwater

AbstractCorrosion and biofouling are wetting‐related phenomena that limit the effective use of metals in aqueous media. Nonwettable surfaces can mitigate the adverse effects of wetting by minimizing contact with water. However, current achievements in this field fall short of meeting industrial requirements due to the short lifetime of plastrons. This study proposes a method to measure the protective sustainability of plastron. Superhydrophobic (SHS) and aerophilic (APhS) surfaces are constructed on lightweight aluminum and are initially analyzed by conventional goniometry, which show comparable values. However, the plastron that develops underwater is substantially different. While SHS exhibit unevenly broken plastron, APhS show uniform, continuous plastron. As an example of the sustained protective performance of plastron, the corrosion resistance of SHS and APhS is presented. Potentiodynamic polarization, impedance spectroscopy, and long‐term immersion in seawater show a drastic enhancement in corrosion resistance, exclusively for APhS. In fact, almost no electrochemical signals are measurable, and no pitting corrosion is observed after 415 days of immersion in seawater. Conversely, SHS show no noticeable improvement and corrode faster than bare Al due to plastron loss. Since goniometric measurements do not provide information on plastron, it is essential to analyze the plastron for any non‐wettable surface utilized underwater.

Preparation of novel CS/SiO2-EDTA nanocomposite from ash of rice straw pellets for enhanced removal efficiency of heavy metal ions in aqueous medium

The production valuable materials from waste for environmental treatment have attracted considerable attention worldwide. In this study, porous silica was produced from the ash of rice straw pellets. The porous silica was then modified with chitosan (CS) and ethylenediaminetetraacetic acid (EDTA) to produce novel CS/SiO2-EDTA nanocomposites for the removal of heavy metals in aqueous medium. The adsorption of Pb2+ was investigated to evaluate the effectiveness of the composite and the effects of reaction parameters on the adsorption process were extensively explored. The adsorption is fast in the initial 5 min, then almost reaches equilibrium in 10 min. The conditions for the highest adsorption capacity are an EDTA content of 1.0 M, a pH of 6, an adsorbent dosage of 0.1 g/L, and a Pb2+ concentration of 100 ppm. The removal efficiency, adsorption capacity, and rate constant are 70.39 %, 703.9 ± 21.1 mg/g, and 0.012 ± 0.003 g/mg·min, respectively. The conditions for the highest adsorption efficiency are an EDTA content of 1.0 M, a pH of 6, an adsorbent dosage of 0.5 g/L, and a Pb2+ concentration of 40 ppm, where the adsorption efficiency, adsorption capacity, and rate constant are 89.88 %, 71.91 ± 1.86 mg/g, and 0.013 ± 0.002 g/mg·min, respectively. The selectivity of the composite was investigated by using Ni2+, Cu2+ and Fe2+ ions under the same experimental conditions. In multi-metal solutions, the adsorbent showed the highest affinity for Pb2+. In addition, the adsorption isotherms and thermodynamics were investigated and an adsorption mechanism was proposed.

Concentration-Driven Interfacial Amorphization toward Highly Stable and High-Rate Zn Metal Batteries.

The interfacial structure holds great promise in suppressing dendrite growth and parasitic reactions of zinc metal in aqueous media. Current advancements prioritize novel component fabrication, yet the local crystal structure significantly impacts the interfacial properties. In addition, there is still a critical need for scalable synthesis methods for expediting the commercialization of aqueous zinc metal batteries (AZMBs). Herein, we propose a scalable concentration-controlled method for realizing crystalline to amorphous transformation of the Zn metal interface with exceptional scalability (>1 m2) and processing consistency (>30 trials). Theoretical and experimental analyses highlight the advantages of amorphous ZnO, which exhibits moderate adsorption energy, strong desolvation ability, and hydrophilicity. Employing the amorphous ZnO-coated zinc metal anode (AZO-Zn) significantly enhances the cycling performance, impressively maintaining 1000 cycles at 100 mA cm-2. The prototype AZO-Zn||MnO2@CNT pouch cell demonstrates a capacity of 15.7 mAh and maintains 91% of its highest capacity over 100 cycles, presenting promising avenues for the future commercialization of AZMBs.

Brief Study of Clay as an Adsorbent of Metals in Aqueous Medium

Brief Study of Clay as an Adsorbent of Metals in Aqueous Medium

Machine Learning Assisted Metal Oxide‐Bismuth Oxy Halide Nanocomposite for Electrochemical Sensing of Heavy Metals in Aqueous Media

AbstractHeavy metal in excess quantity is one of the major inorganic pollutants in water. It causes several hazards to human life and ecosystem. It exists in traces in most of the commonly available drinking water sources from lakes, ponds, wells, etc., However, their presence in treated water is relatively significant. As the treated water is primarily used for agricultural purposes, it is necessary to monitor and measure their concentration. This requires sensing of metals in aqueous medium with good sensitivity and stability. Recently, nanosensors coupled with electrochemical transducer is preferred for analyzing heavy metal in aqueous solutions. In this work, Silver oxide‐bismuth oxy bromide coated with nafion is proposed as an electrochemical sensor for detection of heavy metal ions in aqueous solution. Cyclic voltammetry (CV) behavior of the proposed electrode is observed in different electrolytes. Further, Differential Pulse Voltammetry (DPV) study shows that current increases with trace nickel and copper metal ions of different concentration. Further, machine learning (ML) algorithms such as Naïve Bayes, ANN, SVM and decision trees are employed for nickel ions to train the cyclic voltammetry data and evaluate its performance. Naïve Bayes algorithm provides the best accuracy of 93.2% among all the models.

Ternary nanohybrid of biochar/ NiFe2O4 /Ag3PO4 for simultaneous adsorption of Hg(ІІ) and photodegradation of methylene blue; modeling, kinetic and isotherm studies

In this research, a ternary composite of biochar - nickel ferrite – silver phosphate has been characterized and employed for methylene blue photodegradation and mercury adsorption. Response surface methodology was adopted to optimize effective parameters on removal. It was found that maximum dye degradation and mercury adsorption was obtained at pH of 7 with dosage of 26 mg and 90 min reaction time. Moreover, the composite of biochar/NiFe2O4/Ag3PO4 with the ratio of 70:20:10 able to remove 94 % of dye and 98.5 % of mercury at the initial concentration of 10 mg L−1. It was found that the rate of methylene blue degradation increase with increasing the temperature as it was destroyed at a temperature of 45 °C within 1 h. Kinetic and isotherm studies for the adsorption experiments showed that mercury adsorption followed the pseudo – second order kinetic model and Langmuir adsorption isotherm. Moreover, thermodynamic study indicated that the adsorption process is spontaneous with an endothermic path. With a good maximum adsorption capacity of 241 mg g−1 and four cycle reusability, the prepared composite is a suitable candidate to simultaneously mitigate the side effect of dye and heavy metal in aqueous media.

Study of modified biomass of Gossypium hirsutum as heavy metal biosorbent

The presence of heavy metals in aqueous media can cause serious threats to living organisms. Consequently, for the efficient and economic removal of heavy metals from water, a wide range of biomass as biosorbents has been investigated. The present study was designed to deploy Gossypium hirsutum stem powder as a biosorbent for efficient removal of toxic heavy metals including Pb2+, Cu2+, Zn2+ and Ni2+ ions from aqueous media. The biomass was modified through acid and base treatment prior to its deployment as biosorbent. Different instrumental techniques such as FTIR, SEM and TGA were used to analyze the structural, morphological, and thermal characteristics of biosorbent. AAS, and UV spectrophotometer were used to quantify the metal ions in solutions. Nonlinear models of Langmuir and Freundlich isotherms was explored for practical use in real sample analysis, and adsorption parameters were optimized systematically. The adsorption isotherms followed the non-linear Langmuir model, which best fit four heavy metals with an R2 value (0.99) in both acidic and base-modified biomass. The base treated biomass showed relatively higher maximum uptake capacity for the investigated heavy metals (Pb2+ 121.24, Cu2+ 117.09, Zn2+ 130.65, and Ni2+ 111.09 mg g−1) than that of acid treated biomass. Thermogravimetric analysis revealed the degradation pattern of designed adsorbent. Fourier transform infrared spectroscopy confirmed the presence of OH and Cl groups which were added during pretreatment. Scanning electron microscopy showed that the modified material has rough surface area which can contribute in enhancing the adsorption of heavy metals. The regeneration studies of modified biosorbent using 0.1 M HNO3 solution demonstrated that the biosorbent can be effectively utilized for further five biosorption cycles without significant loss in its adsorption capability. The findings of the study revealed that acid and base modified Gossypium hirsutum stem could be efficiently utilized as a biosorbent for the removal of heavy metals in water at pH 5.5 with an adsorbent dose of 0.5 g and equilibrium time of 35 min.

Usage of natural wastes from animal and plant origins as adsorbents for the removal of some toxic industrial dyes and heavy metals in aqueous media

It has always been crucial to have enough water available for survival and growth; hence it is necessary to purify polluted water for reuse. In this study, contaminated water is cleansed by the adsorption of three dyes Methylene blue (MB), Congo Red (CR), and Bromocersol Green (BCG), as well as two heavy metals, chromium (VI) and zinc (II) using a low-cost adsorbent like activated carbon gotten from treated sheep remnants and barely husks. H3PO4 acid-modified adsorbents were used in adsorption tests, which involved six different parameters (pH, contact time, adsorbent concentration, sorbent dosage, temperature, and stirring speed). The optimum pH values for the adsorption of Cr (VI), Zn (II), MB, CR, and BCG onto both adsorbents were 6, 7, 4, and 6, respectively, giving equilibrium adsorption capacity values of 1.617, 1.529, 15.388, 62.401, and 288.902 mg/g, respectively. The adsorption capacity of the activated carbon increases with increasing contact time till equilibrium is established, Adsorption isotherm study was evaluated using both the Langmuir and the Freundlich isotherms to confirm the effectiveness of adsorbents made from inexpensive wastes. Furthermore, the merits of using treated natural wastes from both plant and animal origins for water purification have been confirmed. This study supports the concepts of the environmental sustainability for the earth plant.

Three-dimensional ZnO–TiO2/graphene aerogel for water remediation: The screening studies of adsorption and photodegradation

Zinc oxide−doped titanium dioxide/graphene aerogel (ZnO−TiO2/GA) nanocomposite was fabricated by the two-step solvothermal method for efficient removal of dyes and toxic metals in aqueous media. Based on the results, ZnO−TiO2/GA material with an optimal ZnO amount of 300 mg has a synergistic effect on exhibiting an excellent photocatalytic-adsorption capacity. The highest degradation efficiency for methylene blue, rhodamine B, and methyl orange was 99.7, 97.3, and 94.9%, respectively, with the optimum conditions: catalyst dose of 0.2 g L−1, 20 ppm dye concentration at 20 min under ultra-visible (UV−11 W) light irradiation. Moreover, the material also showed outstanding reusability with more than 90% dye removal efficiency after 8 cycles of testing. The proposed pathway and intermediate products of dye degradation were also investigated using liquid chromatography−mass spectrometry (LC−MS) analysis. Besides that, the maximum absorption capacity for the toxic metal ions Cd2+ and Co2+ are 380.6 and 230.1 mg g−1, respectively, which followed by the Langmuir isotherm adsorption model. The results exhibited the material's potential for the treatment of water containing toxic metals and waste from textile dyeing.

Uniform and oriented zinc deposition induced by artificial Nb2O5 Layer for highly reversible Zn anode in aqueous zinc ion batteries

Zn metal has recently emerged as a promising candidate for stable and reversible anode in aqueous rechargeable batteries. However, despite the high reversibility of Zn metal in aqueous media, Zn metal anode utilization is limited owing to unavoidable dilemmas, such as dendrite growth, hydrogen gas evolution, and “dead Zn”, eventually leading to battery breakdown. Herein, we propose a Nb2O5 film as an effective coating layer to guarantee uniform ion flux and a rapid transportation pathway for Zn ions through Maxwell–Wagner polarization, resulting in homogeneous Zn electrodeposition under the Nb2O5 layer. The artificial Nb2O5 layer coated on the Zn surface (Nb2O5@Zn) acted as a guide for Zn deposition, enabling a dense and uniform morphology of electrodeposited Zn oriented in a specific direction. The symmetric Nb2O5@Zn anode system exhibited stable plating/stripping for up to 1000 h. Outstanding durability and resilience (220 h at 5 mA cm−2/5 mAh cm−2) and rapid plating/stripping with excellent recovery (returning to 1 from 10 mA cm−2) were verified under harsh cycling conditions. The excellent characteristics of Nb2O5 layer resulted in high electrochemical stability and performance for a full cell with a VO2 cathode for practical applications.

Zero residual heavy metals in aqueous media using composite coagulant converted from bauxite residue

Zero residual heavy metals in aqueous media using composite coagulant converted from bauxite residue

Development of Cyanine 813@Imidazole-Based Doped Supported Devices for Divalent Metal Ions Detection

A NIR cyanine@imidazole derivative Cy1 was synthesized and evaluated as a metal ion sensor in solution. Cy1 was shown to be very sensitive to all metal ions tested, presenting a blue shift in the absorption from 668 nm to 633 nm, followed by a change in colour from pale green to blue with Zn2+, Cd2+, Co2+, Ni2+ and Hg2+ ions. Despite the blue shift in the absorption, a decrease at 633 nm (with a colour change from pale green to colourless), as well as a quenching in the emission intensity at 785 nm were observed for Cu2+ ions. The results show the formation of sandwich complexes of two ligands per metal ion with the highest association constant observed for Cu2+ (Log Kass.abs = 14.76 ± 0.09; Log Kass.emis. = 14.79 ± 0.06). The minimal detectable amounts were found to be 31 nM and 37 nM, with a naked eye detection of 2.9 ppm and 2.1 ppm for Hg2+ and Cu2+ ions, respectively. These results prompted us to explore the applicability of Cy1 by its combination with nanomaterials. Thus, Cy1@ doped MNs and Cy1@ doped PMMA nanoparticles were synthesized. Both nanosystems were shown to be very sensitive to Cu2+ ions in water, allowing a naked-eye detection of at least 1 ppm for Cy1@ doped MNs and 7 ppm for Cy1@ doped PMMA. This colourimetric response is an easy and inexpensive way to assess the presence of metals in aqueous media with no need for further instrumentation.

Stability constants of complexes of metal ions with peatsoil humic acids under non-acid-conditions

Stability constants of complexes of four divalent metal ions viz. Cu2+, Pb2+,Mg2+ and Cd2+ with humic acids (HA) were determined by potentiometric titration of humic acids with the corresponding salt of the divalent metals in aqueous media under non-acid-condition. The log K (logarithm of the stability constant) ranged from 1.0942 to 2.7471 for metal-humic acid complexes were determined using point-wise computational method. The order of stability constants were obtained as follows: Cu >Pb> Cd > Mg for metal -HA complexes respectively, indicating a higher degree of complexation with Cu metal ion.

Monodisperse superparamagnetic nanoparticles separation adsorbents for high-yield removal of arsenic and/or mercury metals in aqueous media

The use of magnetic nanoparticles (MNPs) as adsorbent/separation agents for the removal of heavy metal-based compounds from aqueous environments has received much attention in the last few years. However, in most cases, the designed particles present large dimensions (at least several tens of nm) in order to provide them with high magnetic energy and the capability to be collected with a magnet, thus decreasing their surface-to-volume ratio and displaying a non-superparamagnetic behavior which leads to their irreversible aggregation and avoid their use in repetitive adsorption cycles.Here, we report the preparation of 8.50 nm iron oxide-based MNPs with high specific surface areas where large adsorption of heavy metals can efficiently take place. Through an exhaustive control over the synthetic procedures, we obtained MNPs with high magnetizations despite their reduced dimensions (ca. 80 emu·g−1) and superparamagnetic behavior, enabling their efficient separation with a single magnet whilst avoiding irreversible aggregation. After incubation of MNPs in heavy metal aqueous solutions for 24 h, extremely high adsorption values up to ca. 400 mg of arsenic oxide and 500 mg of mercury oxide per gram of MNPs were measured. The pH of the pollutant solutions has a great influence over the bioremediation capability of the MNPs, being the largest adsorption extents at pH 10.0 and 5.5 for arsenic and mercury oxides, respectively. Moreover, the efficiency of desorption protocols and the subsequent reusability of the MNPs for at least four bioremediation cycles was also evaluated. The adsorption data were modeled following a Langmuir-type behavior, while kinetics experiments demonstrated that pollutant ions are adsorbed onto MNPs surfaces through chemisorption processes.

Use of agro-industrial residues of plantain (Musa paradisiaca) in the adsorption of Ni (II)

The presence of heavy metals in aqueous media represents a severe threat to ecosystems because they are non-biodegradable, toxic, and carcinogenic. In the present work, the utilization of agro-industrial residues from obtaining plantain starch for removing Ni (II) was studied, establishing the effect of temperature, adsorption dose, and initial concentration. The kinetics, equilibrium, and thermodynamic parameters that determine the process were studied. For this purpose, tests were carried out in a batch system maintaining constant stirring (200 rpm), pH (2), and solution volume (100 mL). The remaining metal concentration was determined by atomic adsorption at 237 nm. It was found that the best adsorption conditions were given at 55 ºC, 0.6775 g, and 368 mg/L obtaining a maximum adsorption capacity of 47.57 mg/g corresponding to a removal of 87%. The kinetic model that best fits the experimental data was a pseudo-second-order model, and the isotherm that describes the process is Langmuir and Freundlich, so the adsorption is given by chemisorption and multilayers. The thermodynamic parameters determined suggest that the process is favourable, not spontaneous, endothermic, and irreversible under the studied conditions. The results show that the residual biomass from the obtaining of plantain starch is a good precursor for absorbing Ni (II) in an aqueous solution.

A bifunctional robust metal sulfide with highly selective capture of Pb2+ ions and luminescence sensing ability for heavy metals in aqueous media

A 3-D metal sulfide ion exchanger (MSIE) with extra-framework H+ ions showed a remarkable capability for sorption of Pb2+ ions and highly efficient luminescence sensing properties towards various heavy metal ions.

Magnetic Hydroxyapatite for Batch Adsorption of Heavy Metals

In this work, magnetic hydroxyapatite or hydroxyapatite-iron (III) oxide (HAp-Fe3O4) composite was used as the adsorbent of heavy metals and the performance was evaluated using the batch test. The presence of heavy metals in the effluent from wastewater discharge can be toxic to many organisms and can even lead to eye burns. Therefore, hydroxyapatite synthesized from the chemical precipitation of calcium nitrate tetrahydrate and diammonium hydrogen phosphate solutions is used to remove heavy metal in aqueous media. Magnetic properties of Fe3O4 can help prevent formation of secondary pollutants caused by the loss of adsorbent. The synthesized HAp-Fe3O4 can remove cadmium, zinc and lead effectively, which is up to 90% removal. Reusability study shows that the adsorbent could retain heavy metal ions even after four cycles. The percentage removal of heavy metals maintains at around 80% after four times of usage. The composite of HAp-Fe3O4 demonstrates good performance and stability which is beneficial for heavy metal removal in the future.

OBTAINING DERIVATIVES OF HUMIC SUBSTANCES FROM OXIDIZED COAL AND STUDY OF PHYSICO-CHEMICAL AND ADSORPTION PROPERTIES

In the work, a chemical analysis of humic substances based on oxidized coal of the Maikuben basin (Kazakhstan) is carried out. Humic acids were obtained on the basis of potassium humates by acidification with a 20% acid solution to pH = 3-4.5. The optimal conditions for obtaining nitrohumic acids from oxidized coals are: the duration of the process is 3 hours, the ratio of S:L = 1:5, the content of nitric acid is 64%, sulfuric acid is 96% and the composition of the nitrating mixture is 1:1 (g/g). Amminohumic derivatives were obtained in the presence of a 3% aqueous solution of ammonia using mechanical activation and ultrasonic treatment. The samples obtained were tested as an adsorbent for water purification from heavy metals. Humic acids and aminohumate showed the highest degrees of purification for zinc (99.0-100.0%) and cadmium (80.0-96.7%), and nitrohumic acid showed a high adsorption capacity for heavy metals like copper - 100.0 % and lead 82.9%. This is due to the fact that when interacting with heavy metals, humic acids and their derivatives (amino and nitro) form chelate complexes due to carboxyl, phenolic, nitro and amino groups. As a result of the study, the possibility of using them as non-toxic available sorbents for the purification of heavy metals in aqueous media has been shown.

Formation and Characterization of Dispersed Mixed Iron-titanium Oxide Systems by Electrochemical Method

Aims: Anodic polarization behavior of a combined iron-titanium electrode (two metals in electrical contact with each other) in aqueous solutions containing halide ions (F- and Cl-) was studied. Methods: he joint anodic dissolution of titanium and iron with subsequent thermal treatment makes it possible to obtain precursors of a highly dispersed mixed oxide system Fe2O3-TiO2. The phase and elemental composition and structural characteristics of obtained products were examined using X-ray diffraction and scanning electron microscopy. It has been experimentally confirmed that via changing the anode current density, hydrofluoric acid concentration in electrolyte and ratio of the working surface area of contacting metals, it is possible to effectively control the rate of anodic reactions and phase composition and morphology of anodic oxidation products for iron and titanium components in a combined electrode. Results: The main results of this study are as follows: Electrochemical method for the synthesis of complex dispersed oxide system Fe2O3-TiO2 based on joint anodic oxidation of contacting metals in aqueous media was suggested. Relationships between parameters of the electrochemical process and characteristics of the synthesized oxide system were revealed. Conclusion: By varying the parameters of the electrolysis process, it is possible to prepare complex oxyhydroxides with different ratios of iron and titanium, which makes it possible to synthesize precursors of iron titanates of preset composition and structure.