Concentrations Of Heavy Metal Ions Research Articles

Comparative physicochemical analysis of galvanic sludge wastes

The paper provides the physicochemical analysis of galvanic sludge to determine the presence and concentration of toxic metals. Two sludges sampled from the same factory, but from different technological processes, alkaline galvanic sludge obtained from galvanizing process and acidic sludge generated from the chromium plating process were analyzed. Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES) revealed increased concentrations of toxic heavy metal ions Zn2+, Cr3+, Ni2+ and Pb2+ in the sludge from the galvanizing process and Cr3+, Cu2+, Ni2+, Pb2+, Cd2+ and Zn2+ from the chroming process. Moreover, the sludges were further physicochemically characterized by Reflectance Fourier Transform InfraRed Spectrometry (FTIR), Scanning Electron Microscopy with Energy-dispersive X-ray Spectroscopy Analysis (SEM-EDX) and X-ray diffraction (XRD). The results of ICP-OES were corroborated by FTIR. Analysis of FTIR spectra revealed the specific bands indicating the existence of metal oxides in the analyzed sludges, as well as the presence of organic substances, i.e. solvents and surfactants, used in the electroplating process. The analysis was accomplished following international norms and confirmed the increased concentrations of heavy metal ions from both sludges. In line with the regulations of the Environmental Protection Agency (EPA), the results proved the hypothesis that galvanic sludge is hazardous waste.

Synthesized Zeolite Based on Egyptian Boiler Ash Residue and Kaolin for the Effective Removal of Heavy Metal Ions from Industrial Wastewater

The increase of global environmental restrictions concerning solid and liquid industrial waste, in addition to the problem of climate change, which leads to a shortage of clean water resources, has raised interest in developing alternative and eco-friendly technologies for recycling and reducing the amount of these wastes. This study aims to utilize Sulfuric acid solid residue (SASR), which is produced as a useless waste in the multi-processing of Egyptian boiler ash. A modified mixture of SASR and kaolin was used as the basic component for synthesizing cost-effective zeolite using the alkaline fusion-hydrothermal method for the removal of heavy metal ions from industrial wastewater. The factors affecting the synthesis of zeolite, including the fusion temperature and SASR: kaolin mixing ratios, were investigated. The synthesized zeolite was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), particle size analysis (PSD) and N2 adsorption-desorption. The SASR: kaolin weight ratio of 1:1.5 yields faujasite and sodalite zeolite with 85.21% crystallinity, which then shows the best composition and characteristics of the synthesized zeolite. The factors affecting the adsorption of Zn2+, Pb2+, Cu2+, and Cd2+ ions from wastewater on synthesized zeolite surfaces, including the effect of pH, adsorbent dosage, contact time, initial concentration, and temperature, have been investigated. The obtained results indicate that a pseudo-second-order kinetic model and Langmuir isotherm model describe the adsorption process. The maximum adsorption capacities of Zn2+, Pb2+, Cu2+, and Cd2+ ions onto zeolite at 20 °C were 12.025, 15.96, 12.247, and 16.17 mg·g-1, respectively. The main mechanisms controlling the removal of these metal ions from aqueous solution by synthesized zeolite were proposed to be either surface adsorption, precipitation, or ion exchange. The quality of the wastewater sample obtained from the Egyptian General Petroleum Corporation (Eastern Desert, Egypt) was highly improved using the synthesized zeolite and the content of heavy metal ions was significantly reduced, which enhances the utilization of the treated water in agriculture.

Metal–Organic Framework-Based Aerogel: A Novel Adsorbent for the Efficient Removal of Heavy Metal Ions and Selective Removal of a Cationic Dye from Aqueous Solution

Ameliorating the existing purification methods with more affordable, efficient, and industrially adoptable methods that remove heavy metal ions from contaminated drinking water constitutes a persistent technological challenge. Metal–organic framework (MOF)-based materials with their excellent adsorption performance are recently explored as an alternative method to the traditional methods. Here, we report a MOF/biopolymer composite-based aerogel that is a cost-effective, highly efficient, and environmentally sustainable material for the removal of large concentrations of heavy metal ions (1277 mg of Pb2+, 466 mg of Cd2+, and 706 mg of Cr6+ per gram of the aerogel) and the selective removal of the cationic dye crystal violet (310 mg/g) from its mixture with (anionic) methyl orange from contaminated water samples. The MOF used herein is 2-methylimidazole zinc complex (ZIF-8), whereas the biopolymer is the nontoxic and biodegradable Iota-Carrageenan (iCG), a sulfated polysaccharide extracted from red seaweeds. We have transformed the ZIF-8 powder into a moldable, load-bearable, flexible, and eco-friendly ZIF-8@iCG aerogel. SEM images confirmed that ZIF-8 is physically embedded in Iota-Carrageenan, forming a honeycomb structure. The ZIF-8 is located onto the fibers of iCG, forming a thermally stable, flame-retardant ZIF-8@iCG hydrogel, with high mechanical strength and intrinsic porosity. The aerogel removes 92.03% of Pb2+ ions from an intentionally spiked Pb2+ solution (1 ppm), making this water sample drinkable upon three successive filtrations. The thermodynamics of metal ion adsorption suggest that the adsorption kinetics follow the Langmuir adsorption isotherm model and the adsorption process is endothermic. Ion leaching experiments suggest that leaching of zinc ions from the aerogel is negligible. Thus, the newly designed ZIF-8@iCG aerogel is a potentially effective adsorbent for the removal of heavy metal ions and organic dyes from drinking water and is intended for industrial use.

Development of in-situ electrochemical heavy metal ion sensor using integrated 1D/0D/1D hybrid by MWCNT and CQDs supported MnO2 nanomaterial

An integrated 1D/0D/1D hybrid nanomaterial was prepared from MWCNT supported carbon quantum dots @ MnO2 nanomaterial for a sensitive and selective electrochemical heavy metal ion sensor by hydrothermal methods. The developed nanomaterials were characterized by various analytical methods such as FESEM, HRTEM, XRD, FTIR, EDX and elemental mapping study, and also its electrochemical properties of the prepared samples were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analysis. Differential pulse voltammetry (DPV) analysis has been used to investigate the quantitative detection of heavy metal ions such as cadmium and chromium on modified electrodes under optimal conditions. The in-situ electrochemical sensitivity and selectivity of the samples were determined by varying various parameters, such as the concentration of heavy metal ions, different electrolytes and electrolyte pH. The observed DPV results show that prepared MWCNT (0.05 wt%) and CQD (0.1 wt%) supported MnO2 nanoparticles show effective detection response for chromium (IV) metal ion. In particular, 0D CQD, 1D MWCNT, and MnO2 hybrid nanostructures produced a synergistic effect among them, resulting in strong electrochemical performance of the prepared samples against the target metal ions.

Label-free heavy metal ion sensing via smartphone based app

The proliferation of heavy metal ions in water has been a serious problem that has been escalating day by day. Rapid detection of these ions in an aqueous solution is of immense significance to keep them within permissible limit. To address the growing concentration of heavy metal ions, we report a facile and cost-effective sensing scheme. Based on intensity modulation, the sensing scheme comprises of a smartphone, light source, and analyte. The results reveal that the concentration of heavy metal ions can be detected at ppb level. The sensing scheme renders an average limit of detection (LOD) of ∼0.5 ppb for those assessed ions. Further, spiked tap water has also been assessed to check the applicability of the scheme which eventually yields a ∼95% recovery level. Overall, the sensing scheme with minimal logistics is believed to replace the complex analysis procedure executed through bulky and sophisticated instruments.

Accumulation of Heavy Metal Ions from Urban Soil in Spontaneous Flora

This study aimed to analyse the bioaccumulation of heavy metal ions in plants of spontaneous flora. An urban area was established from which soil samples were taken and analyses were performed on the content of heavy metal ions. The soil samples were collected from Iasi’s urban area to determine the heavy metal concentrations, obtain maps of sensitive land, and determine the content of heavy metals in spontaneous flora and transfer these into an aqueous extract. The investigation of heavy metal ion levels in certain plants revealed the following: (i) all plants from the Brassicaceae accumulate heavy metals, and B. juncea has a great ability to accumulate and transfer Cu, Cr(VI), Cd, Ni, Pb, and Zn towards the shoots; (ii) heavy metals (Fe, Cu, Cr, Mn, Zn) were present in variable concentrations, with mint and nettle being notable for their increased level of iron and thyme, and rattle for its zinc levels; (iii) toxic metals (Pb, Cd, Ni) are present in low concentrations in plants as well as in infusions, except for in primula and plantain, which do not have high levels of Pb and Cd. The results showed that values exceeded the maximum recommended values in areas with industrial pollution. Taking into account the potential for the bioaccumulation of heavy metal ions by plants from spontaneous flora and their use as medicinal plants, it is recommended, based on the studies conducted, to harvest and use plants from soils that do not contain heavy metal ions.

Control mechanism of the migration of heavy metal ions from gangue backfill bodies in mined-out areas

In the process of solid backfill mining, the leaching of heavy metal ions from the gangue backfill body in the mined-out area can pose potential risk of polluting water resources in the mine. Accordingly, based on the environment of the gangue backfill body, the migration model of heavy metal ions from the gangue backfill body was established to reveal the pollution mechanism of water resources by the gangue backfill body in the mined-out area. The main factors that affect the migration of heavy metal ions were analyzed, and prevention and control techniques for the leaching and migration of heavy metal ions from gangue backfill bodies were proposed. Research showed that the heavy metal ions in gangue backfill bodies were subjected to the coupled action of seepage, concentration, and stress and then driven by water head pressure and gravitational potential energy to migrate downward along the pore channels in the floor, during which mine water served as the carrier. The migration distance of heavy metal ions increased with time. According to the migration rate, the migration process can be subdivided into three phases: the rapid migration phase (0–50 years), the slow migration phase (50–125 years), and the stable phase (125–200 years). It was concluded that the leaching concentration of heavy metal ions, the particle size of gangue, the permeability of floor strata, and the burial depth of coal seams were the main influencing factors of the migration of heavy metal ions. From the two perspectives of heavy metal ion leaching and migration, prevention and control techniques for the leaching and migration of heavy metal ions from gangue backfill bodies were proposed to protect water resources in mining area. The present study is of great significance to realizing utilization of solid waste in mines and protecting the ecological environment.

One-Dimensional Phononic Crystals: A Simplified Platform for Effective Detection of Heavy Metals in Water with High Sensitivity.

Recently, the pollution of fresh water with heavy metals due to technological and industrial breakthroughs has reached record levels. Therefore, monitoring these metals in fresh water has become essentially urgent. Meanwhile, the conventional periodic one-dimensional phononic crystals can provide a novel platform for detecting the pollution of heavy metals in fresh water with high sensitivity. A simplified design of a defective, one-dimensional phononic crystals (1D-PnC) structure is introduced in this paper. The sensor is designed from a lead-epoxy multilayer with a central defect layer filled with an aqueous solution from cadmium bromide (CdBr2). The formation of a resonant peak through the transmittance spectrum is highly expected. This study primarily aims to monitor and detect the concentration of cadmium bromide in pure water based on shifting the position of this resonant peak. Notably, any change in cadmium bromide concentration can affect the acoustic properties of cadmium bromide directly. The transfer matrix method has been used to calculate the transmission spectra of the incident acoustic wave. The numerical findings are mainly based on the optimization of the cadmium bromide layer thickness, lead layer thickness, epoxy layer thickness, and the number of periods to investigate the most optimum sensor performance. The introduced sensor in this study has provided a remarkably high sensitivity (S = 1904.25 Hz) within a concentration range of (0-10,000 ppm). The proposed sensor provides a quality factor (QF), a resolution, and a figure of merit of 1398.51752, 48,875,750 Hz, and 4.12088 × 10-5 (/ppm), respectively. Accordingly, this sensor can be a potentially robust base for a promising platform to detect small concentrations of heavy metal ions in fresh water.

Heavy metals biosensor based on defective one-dimensional phononic crystals

In recent years, the detection of water pollution with low levels of heavy metals has attracted the great attention of many researchers as a result of the imminent danger of this type of pollution to all mankind. Meanwhile, we introduce a theoretical approach based on the one-dimensional phononic crystals (1D-PnCs) with a central defect layer as a novel platform for the highly sensitive detection of heavy metal pollution in freshwater. Therefore, the creation of a resonant peak in the transmittance spectrum related to this defect layer is highly conceivable. In this regard, the detection of cadmium chloride (CdCl2) as a dangerous, toxic, and extremely hazardous heavy metal could be investigated based on the small displacement in the position of this resonant peak with the changes in the CdCl2 concentration. Notably, any change in CdCl2 concentration has a direct impact on its acoustic properties. The theoretical framework of our research study is essentially based on the 2 × 2 transfer matrix method and the acoustic properties of the constituent materials as well. The optimization of all sensor parameters represents the mainstay of this study to get the best sensor performance. In this regard, the proposed sensor has a remarkably high sensitivity (S = 1904.25 Hz/ppm) over a concentration range of 0 – 10000 ppm. In addition, the sensor has a high quality factor (QF), and figure of merit of 1771.318, and 73529410−5 (ppm−1), respectively. Finally, we believe this sensor could be a key component of a feasible platform for detecting low concentrations of different heavy metal ions in freshwater.

Molecular Insights into a Novel Cu(I)-Sensitive ArsR/SmtB Family Repressor in Extremophile Acidithiobacillus caldus.

Acidithiobacillus caldus is a common bioleaching bacterium that is inevitably exposed to extreme copper stress in leachates. The ArsR/SmtB family of metalloregulatory repressors regulates homeostasis and resistance in bacteria by specifically responding to metals. Here, we characterized A. caldus Cu(I)-sensitive repressor (AcsR) and gained molecular insights into this new member of the ArsR/SmtB family. Transcriptional analysis indicated that the promoter (PIII) of acsR was highly active in Escherichia coli but inhibited upon AcsR binding to the PIII-acsR region. Size exclusion chromatography and circular dichroism spectra revealed that CuI-AcsR shared an identical assembly state with apo-AcsR, as a dimer with fewer α helices, more extended strands, and more β turns. Mutation of the cysteine site in AcsR did not affect its assembly state. Copper(I) titrations revealed that apo-AcsR bound two Cu(I) molecules per monomer in vitro with an average dissociation constant (KD) for bicinchoninic acid competition of 2.55 × 10-9 M. Site-directed mutation of putative Cu(I)-binding ligands in AcsR showed that replacing Cys64 with Ala reduces copper binding ability from two Cu(I) molecules per monomer to one, with an average KD of 6.05 × 10-9 M. Electrophoretic mobility shift assays revealed that apo-AcsR has high affinity for the 12-2-12 imperfect inverted repeats P2245 and P2270 in the acsR gene cluster and that Cu-loaded AcsR had lower affinity for DNA fragments than apo-AcsR. We developed a hypothetical working model of AcsR to better understand Cu resistance mechanisms in A. caldus. IMPORTANCE Copper (Cu) resistance among various microorganisms is attracting interest. The chemolithoautotrophic bacterium A. caldus, which can tolerate extreme copper stress (≥10 g/L Cu ions), is typically used to bioleach chalcopyrite (CuFeS2). Understanding of Cu resistance in A. caldus is limited due to scant investigation and the absence of efficient gene manipulation tools. Here, we characterized a new member of the ArsR/SmtB family of prokaryotic metalloregulatory transcriptional proteins that repress operons linked to stress-inducing concentrations of heavy metal ions. This protein can bind two Cu(I) molecules per monomer and negatively regulate its gene cluster. Members of the ArsR/SmtB family have not been investigated in A. caldus until now. The discovery of this novel protein enriches understanding of Cu homeostasis in A. caldus.

Fir sawdust as a low-cost and easily recyclable adsorbent: efficient removal of Pb(II), Cu(II), and Zn(II) contaminants from wastewater.

The main pollution sources of heavy metals are the arbitrary discharge of industrial wastewater and waste residues, which cause serious harm to the water environment, soil environment, and human health. In this study, following the principle of waste utilization, a gel adsorbent (AA-SW-AMPS) was prepared by microwave-assisted chemical cross-linking using fir sawdust as raw material. A scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and swelling dynamic experiments were used to investigate the microstructure, reaction mechanism, and water absorption performance of AA-SW-AMPS. The N2 adsorption-desorption curve shows that the porous structure of AA-SW-AMPS creates 240.75 cm2/g of specific surface area to enable excellent heavy-metal sorption. It was determined by adsorption experiments that the optimal adsorption state was when the dosage of AA-SW-AMPS was 5g/L, the pH of the solution was 5, the adsorption time was 45min, and the initial heavy metal ion concentration was 250mg/L. In addition, the adsorption mechanism was investigated using adsorption dynamics, adsorption isotherm, and Materials Studio simulation. The results show that the maximum adsorption capacities of AA-SW-AMPS for Pb(II), Cu(II), and Zn(II) were 253.49mg/g, 237.29mg/g, and 232.15mg/g, respectively, and the adsorption mechanism is monolayer chemisorption. The adsorbent showed great potential in removing heavy metals from wastewater.

Peculiarities of Transamination Processes in Tissues of Cyprinus carpio and Unio pictorum under the Impact of Elevated Concentrations of Metal Ions in Water

The role of the amino acids' transamination in the tissues of fish (<i>Cyprinus carpio</i> L.) and mollusk (<i>Unio pictorum</i> L.) in homeostasis of protein metabolism under the impact of 2 and 5 maximum permissible concentrations (MPC) of Mn<sup>2+</sup>, Zn<sup>2+</sup>, Cu<sup>2+</sup> and Pb<sup>2+</sup> ions was studied. Changes in the aspartate amino-transferase (AsAT) and alanine aminotransferase (AlAT) activity under toxic impact were species-specific and depend on nature and concentration of metal in water, tissular and cellular localization of enzymes. Impact of all metals, except for Cu, caused increase of mitochondrial AsAT activity in liver and muscles of carp. Exposure to sublethal concentrations of Zn<sup>2+</sup>, Cu<sup>2+</sup>, and Pb<sup>2+</sup> ions also resulted in AsAT activation in the mitochondria of mollusk's tissues. AlAT activity in the cytoplasmic fraction of muscles and liver of both hydrobionts increased under the impact 5 MPC of all metal ions and decreased under 2 MPC. Changes of AlAT activity in mitochondria and AsAT in cytoplasm of both fish and mollusk under the impact of 2 MPC were multidirectional and determined by metal and its concentration. The transaminases' role in adaptation of the aquatic animals to the impact of heavy metal ions consists in redistribution of amino acid reserves in order to use some for ammonia detoxification (glutamate, aspartate), and others (keto acids) for energy producing to counteract the stress factor. Changes in transaminases' activity reflect the state of the organism under the impact of elevated concentrations of heavy metal ions, characterize degree of the considered hydrobionts resistance to pollution, and can also be used to predict changes in biocenoses in the contaminated areas.

Heavy metal sorption by native shells of pea grain

One of the current problems of the agricultural and industrial complex is the increase in the volume of waste generated, with a low level of recycling. A promising way to recycle waste from enterprises engaged in grain processing is to produce sorbents for purification of polluted water. The aim of this work was to study the degree of sorption of heavy metal ions, which are one of the main pollutants of surface and industrial wastewater, native shells of pea grains. The raw materials investigated were crushed and infused in distilled water. Then solutions of heavy metals in a certain concentration were added, followed by filtration, mineralisation of the obtained samples, and determination of the residual concentration of heavy metal ions by inversion voltammetry. It was found that the sorption activity of pea grain shells varies depending on the variety of this crop and the type of heavy metals. The lowest residual concentration of cadmium in the model solutions after exposure indicates the highest sorption capacity of the native shells of the pea grains in relation to the ions of this metal. The best ability to bind heavy metal ions were the shells of pea variety Temp. However, native shells of pea grains are not able to fully extract heavy metal ions from aqueous solutions. Modification of pea grain shells will increase their sorption activity.

Development of a 3-D-printable device for continuous measuring of heavy metal ion concentrations

Three-dimensional (3-D) printing offers the potential to create a range of tailored devices within many different industrial facilities. In this article, devices were designed and fabricated using 3-D printing to house electrodes for the testing of heavy metal concentration in hazardous fluids, particularly for biological samples such as urine or blood. The devices, connected to a syringe pump, were shown to be able to be operated without leaking. Proof of concept experiments were performed using Anodic Stripping Voltammetry (ASV) methods, demonstrating that the devices are able to be used for quick, cheap testing, showing the potential of the technique as a more hygienic analysis technique than conventional ASV with an immediacy that standard techniques such as inductively coupled plasma mass spectrometry (ICP-MS) do not offer. With further development and validation, 3-D-printed ASV techniques may provide a robust, reliable and affordable solution for heavy metal concentration detection in remote locations.

Mathematical Modelling on the effect of Mercury on the Growth Rate of Serratia marcescens strain DRY6 on Sodium Dodecyl Sulphate

Sodium dodecyl sulfate (SDS) or sodium lauryl sulfate (SLS) is a common anionic surfactant found in various cleaning and personal hygiene products. It has both a polar "headgroup" and a hydrocarbon tail, giving it amphiphilic properties that make it effective as a detergent. However, this also makes it a major pollutant in aquatic environments. Researchers have studied the biodegradation of SDS by microorganisms, particularly bacteria, as a potential cleanup method. It has been found that mercury can significantly inhibit the degradation of SDS by the Serratia marcescens strain DRY6 bacteria. At different mercury concentrations, the bacteria exhibited sigmoidal growth with lag times of 7 to 10 hours, but overall growth was decreased with higher mercury concentrations, with a concentration of 1.0 g/L virtually stopping all growth. A modified Gompertz model was used to calculate growth rates at various mercury concentrations, and these rates were then modeled using five different models: modified Han-Levenspiel, Wang, Liu, modified Andrews, and Amor. Only three of the models (Wang, modified Han-Levenspiel, and Liu) were able to accurately fit the curve, with the Wang model performing the best statistically. The Wang model yielded estimates of 0.216 (95% confidence interval: 0.193 to 0.239) for the critical heavy metal ion concentration, 1.05 (95% confidence interval: 0.938 to 1.167) for the maximum growth rate, and 0.389 (95% confidence interval: 0.148 to 0.636) for the empirical constant , represented by Ccrit, max and m, respectively.

Inhibitory Effect of Copper on the Growth Rate of Serratia marcescens strain DRY6 on SDS

The anionic surfactant known as sodium dodecyl sulfate (SDS) or sodium lauryl sulfate (SLS) is found in a wide variety of products designed for cleaning and personal hygiene. Because of the combination of its hydrocarbon tail and its polar "headgroup," the molecule possesses the amphiphilic qualities that make it suitable for use as a detergent. Due to this it is a major pollutant in aquatic bodies. One of the most researched types of cleanup is biodegradation by microorganisms, particularly bacteria. Copper has a profound effect in inhibiting the degradation of SDS by the bacteria Serratia marcescens strain DRY6. Under different copper concentrations, the SDS-degrading bacteria grew in a sigmoidal manner with lag times of 7 to 10 hours. Overall growth was decreased when the concentration of copper was raised, with 1.0 g/L virtually completely stopping bacterial growth. Rates of expansion at various copper concentrations were calculated using a modified Gompertz model. Following the modification of the Gompertz model, the growth rates were modeled using the modified Han-Levenspiel, Wang, Liu, modified Andrews, and the Amor models. Only three of the five models (Wang, modified Han-Levenspiel, and the Liu models) were able to match the curve; the modified Andrews and Amor models did not. As for model fit, the Wang and modified Han-Levenspiel models perform admirably, but the Liu model performs poorly. The Wang model performed best statistically, with the lowest RMSE and AICc values, the greatest adjusted correlation coefficient (adR2), and AF and BF values closest to unity. The Wang model yielded estimates of 0.216 (95% confidence interval: 0.193 to 0.239), 1.05 (95% confidence interval: 0.938 to 1.167), and 0.389 (95% confidence interval: 0.148 to 0.636) for the critical heavy metal ion concentration (g/l), maximum growth rate (g/l h), and empirical constant.

Optimal design and performance of eco-friendly materials stabilized with inorganic binder based on fluidized bed coal combustion fly ash and regenerated brick powder

The development of green and eco-friendly road engineering materials has become essential to achieving carbon emission reduction and sustainable development. In this study, recycled brick powder (RBP) from construction waste and fluidized bed coal combustion fly ash (FBCF) are combined to replace the traditional lime-fly ash diatomic material in order to produce eco-friendly materials stabilized with inorganic binder (EFMSIB) for roads. The results showed that, when the ratio of EFMSIB is m(RBP):m(FBCF):m(Aggregate) equals 7%:13%:80%, its 7d and 28d unconfined compressive strength are 3.4 MPa and 8.72 MPa, respectively, 180d compression rebound modulus is 1440 MPa, 180d bending tensile strength is 1.51 MPa, 28d mass loss rate is 1.87%, and the residual compressive strength was 93.36%, and all the properties reached the optimal values. The composite material of FBCF and RBP can complete the pozzolanic reaction to form ettringite (AFt) relatively quickly at the early stage of hydration, which promotes the development of the early strength of hydration products, resulting in the compressive strength of NT4 increased by 1.8 times compared with the reference sample. With the growth of the curing age, the active SiO2 and Al2O3 in the material react with CaO to produce hydrated calcium silicate, which promotes the development of the strength of the system in the later stage, resulting in the compressive strength of NT4 increased by 1.6 times compared with the reference sample. The prepared EFMSIB material has a better self-consolidation effect on heavy metals, and the leachate heavy metal ion concentration of NT4 can reach the standard of class III surface water.

Synthesis of ZIF-8@GO-COOH and its adsorption for Cu(II) and Pb(II) from water: Capability and mechanism

The removal of heavy metal ions from the aqueous environment is an important topic as heavy metal pollution is widely distributed in water bodies, causing serious damage to aquatic ecosystems and worsening the already scarce freshwater resources. In this work, we report the synthesis of novel ZIF-8@GO-COOH composite nanosorbent materials by in situ self-assembly. The physicochemical properties of the composites were investigated using relevant characterisation techniques, and the adsorption capacity of ZIF-8@GO-COOH for copper and lead ions in aqueous solution was tested by batch adsorption experiments. The adsorption behaviour was analysed by combining adsorption kinetics, adsorption isotherm model and Van't Hoff model. The results showed that the adsorption capacities of ZIF-8@GO-COOH for Cu(II) and Pb(II) were 93.26 mg/g and 95.875 mg/g, respectively, when the initial heavy metal ion concentration was 100 mg/L, the adsorption time was 60 min, the temperature was 293 K and the pH conditions were suitable. The high adsorption performance of ZIF-8@GO-COOH was attributed to its surface with abundant oxygen-containing functional groups and excellent specific surface area, which gives it a significant advantage in the removal of heavy metal ions from aqueous solutions.

Adsorption of Lead (ii), Chromium (vi) and Manganese (ii) metal ions from water using modified Pennisetum purpureum Schumach plant stalk

Water pollution is a global problem affecting humanity. Availability of clean water is a fundamental prerequisite to public health safety and the survival of the human race as well as animals. However, pollution of river water by heavy metal ions deposition is a grave environmental problem. Presence of the heavy metals in the water, pose a serious health risk particularly to rural populations which rely majorly on the river water for domestic purposes. Several methods for elimination of the heavy metal pollutants from river waters have been previously employed. However, most of these methods are expensive and cumbersome, hence not sustainable. This research explored the potential of modified Pennisetum purpureum Schumach plant adsorbent in removal of Lead (II), Manganese (II) and Chromium (VI) ions from spiked water samples by adsorption. Surface analysis of the adsorbent using FTIR Photometer confirmed presence of functional groups such as -NH2, C=O and O-H responsible for adsorption of heavy metal ions. Concentration of heavy metal ions in water samples was determined before and after adsorption process using Atomic Absorption Spectroscopy (AAS) and means concentration computed. Effect of changes in pH on adsorption was investigated by conducting adsorption at three different pH conditions of 5, 7 and 9. Modification of the adsorbent surface improved its adsorption capacity. For instance, at pH 5, adsorption of Cr+6 increased from 12% to 14.82% when modified adsorbent was used. The modified adsorbent achieved greater % adsorption in all the three metals. Increase in the pH of adsorption from 5 to 9 had a reducing effect on the percent adsorption. At pH of 5 the % adsorption of Pb+2 reduced from 90.26% to 73.75% at pH of 9. This reductions in percentage adsorption were recorded for Pb+2 and Mn+2 ions but not significant for Cr+6 ions. These results show the potential of P. purpureum plant for use as an adsorbent in purification/detoxification of river water which would present a cheaper and more readily available alternative to many current adsorbents and adsorption methods in use. However further research is needed to determine the optimal set of conditions as well as the most suitable modification treatment for maximum adsorption.

Comparative genomic analysis provides insight into the phylogeny and potential mechanisms of adaptive evolution of Sphingobacterium sp. CZ-2

Sphingobacterium is a class of Gram-negative, non-fermentative bacilli that have received widespread attention due to their broad ecological distribution and oil degradation ability, but are rarely involved in infections. In this manuscript, a novel Sphingobacterium strain isolated from wildfire-infected tobacco leaves was named Sphingobacterium sp. CZ-2. NGS and TGS sequencing results showed a whole genome of 3.92 Mb with 40.68 mol% GC content and containing 3,462 protein-coding genes, 9 rRNA-coding genes and 50 tRNA-coding genes. Phylogenetic analysis, ANI and dDDH calculations all supported that Sphingobacterium sp. CZ-2 represented a novel species of the genus Sphingobacterium. Analysis of the specific genes of Sphingobacterium sp. CZ-2 by comparative genomics revealed that metal transport proteins encoded by the troD and cusA genes could maintain the balance of heavy metal ion concentrations in the internal environment of bacteria and avoid heavy metal toxicity while meeting the needs of growth and reproduction, and transport proteins encoded by the malG gene could keep nutrients required for the survival of bacteria. Synteny and genome evolutionary analyses of Sphingobacterium strains implicated that the gene family contraction as a major process in genome evolution, with insertional sequences leading to mutations, deletions and reversals of genes that help bacteria to withstand complex environmental changes. Complete genome sequencing and systematic comparative genomic analysis will contribute new insights into the adaptive evolution of this novel species and the genus Sphingobacterium.