Toxic Heavy Metal Ions Research Articles

The use of agro-industrial residues of coffee ( Coffea arabica) for the removal of mercury from water

Contamination of water bodies by heavy metals is a continuously growing environmental issue. High concentrations of mercury (Hg) in river waters are a recognized environmental problem, because it is one of the most toxic heavy metal ions as it causes damage to the central nervous system. Its negative impact has led to the development of different methods for the treatment of effluents contaminated with Hg(II). The aim of this article is to evaluate the use of coffee ( Coffea arabica) residues as adsorbent of Mercury in an aqueous solution. Four kinetic models, including intraparticle diffusion, pseudo-first-order, pseudo-second-order, and Elovich kinetic models were applied to explore the internal mechanism of mercury adsorption. Results indicate that the pseudo-first-order and pseudo-second-order models could accurately describe the adsorption process. It means that chemical adsorption play an important role in the adsorption of mercury by activated carbon. Meanwhile, the external mass transfer process is more effective in controlling the activated carbon mercury adsorption according to the fitting result of the pseudo-first-order model. The fitting to Langmuir’s model suggested that the material surface is energetically homogeneous. The technique of contaminated biomass encapsulation proved to be safe for short-term disposal when metal recovery is not desired.

Electronic structure engineering of BaTiO3 cuboctahedrons by doping copper to enhance the photocatalytic activity for environmental remediation

The advent of perovskites as an efficient photocatalyst has paved the way to newer possibilities in the degradation of contaminants such as dyes and toxic heavy metal ions. The alleged poor photocatalyst BaTiO3 was engineered to perform better by decreasing its bandgap to make it visible light active via doping. The high-risk factor in the reduction of the bandgap is the formation of recombination centers for the charge carriers which decreases the efficiency of the photocatalyst. Herein, we studied the electronic structure tuning of BaTiO3 by doping copper and developed a one pot synthesis method to obtain copper doped BaTiO3 that has a high surface area, lower recombination rate, and higher photocatalytic efficiency towards dye degradation and hexavalent chromium ion reduction. The 0.5 CuBT sample had a photocatalytic efficiency of 99.4 % for methyl violet decomposition within 120 min and 99.8 % for hexavalent chromium ion reduction by fructose in 20 min.

A novel strategy of engineering genetically encoded probe for ultrasensitive sensing Hg2+ with unusual planar trigonometric coordination configuration

At present, few genetically encoded fluorescent probes are currently available for the analysis of toxic heavy metal ions, and most have poor performance that cannot meet the requirements of sensitive and dynamic detection in living cells. In this study, we designed a single fluorescent protein-based probe sfGFP-MerBD, which can specifically response to Hg2+ with high binding affinity and wide dynamic range. More importantly, the developing probe can timely and reversibly monitor changes of Hg2+ concentration in living mammalian cells. The excellent performance of this probe is largely due to the recognition element of the probe, MerBD, which adopts an unusual planar trigonometric coordination configuration with Hg2+, and the coordination can cause enough conformational change to influence the fluorescence of skeleton protein sfGFP coupled with it. The small peptide MerBD was delicately designed based on the three-dimensional structure of metalloprotein MerR. This novel design strategy solves the challenging problems that there are few natural functional proteins in the process of constructing fluorescent probes for toxic metal ions and some functional proteins cannot be directly used as recognition elements. Based on the new strategy, more genetically encoded fluorescent probes of toxic heavy metal ions can be efficiently constructed and applied in the future.

Facile synthesis of ZIF-8 incorporated electrospun PAN/PEI nanofibrous composite membrane for efficient Cr(VI) adsorption from water

Hexavalent chromium Cr(VI) is one of the most toxic heavy metal ions. Therefore, the removal of this contaminant from wastewater is of particular importance. Herein, a novel zeolitic imidazolate framework (ZIF-8) nanoparticles based electrospun polyacrylonitrile (PAN)/polyethylenimine (PEI) nanofibrous composite membranes (NCMs) were prepared and characterized by SEM, XRD, FTIR, TGA and other characterization techniques. The NCMs were tested for the adsorption of Cr(VI) from water. Results showed that the inclusion of PEI tailored the surface of the NCM to be superhydrophilic. The prepared electrospun NCM showed a high adsorption capacity for Cr(VI) (up to 403.5 mg·g−1) under ZIF-8 concentration of 5 wt%. More importantly, introducing ZIF-8 up to 5 % did not only increase the adsorption capacity but also enhanced the thermal stability, mechanical strength, and structure of the NCM. The experimental analysis of co-existing ions and the reusability of up to ten cycles showed that the optimized PAN/PEI@ZIF-8 NCM exhibited good selectivity and excellent stability for wastewater treatment. The adsorption kinetics followed the pseudo-second-order model and the adsorption isotherm could be fitted well by the Langmuir model. Thermodynamics revealed that the adsorption process was spontaneous and endothermic. The adsorption mechanism was found to be mainly electrostatic attraction and reduction. This study demonstrated the potential of ZIF-8-incorporated PAN/PEI NCMs for the removal of Cr(VI) from water.

Waste Tea Leaves as an Adsorbent for the Removal of Heavy Metal Ions from Aqueous Solutions: Quantitative Estimation using Spectrophotometry and Titrimetry

The rapid increase in industrialization and globalization in the last few decades has led to increased disposal of heavy metals in the environment leading to severe water and soil contamination. Among all known pollutants, heavy metals are especially notorious due to their high toxicity, persistent and bioaccumulative nature. Heavy metal toxicity is a major threat and therefore its removal and remediation require special attention to protect human, animal and plant health and to restore soil and water quality. Waste tea leaves (Camellia sinensis) are low-cost adsorbents and their use for the removal of heavy metal ions is likely to address the problems of waste management and heavy metal ion toxicity. In the present study, we have tested the efficacy of waste tea leaves for the quantitative removal of heavy metal ions like Ni(II) and Pb(II) from their aqueous test solutions using spectrophotometric and titrimetric methods respectively. With 5 g tea leaves in the Ni(II) solution, the removal percentage of the ion was found to be 85.56%. From a Pb(II) containing test solution, 286 ppm of the ion was adsorbed by the same amount of tea leaves. The amount of adsorbent dose was found to be directly related to the removal percentage of the metal ion. However, after reaching a threshold, increasing the adsorbent dose has only a negligible effect on adsorption. The adsorption was found to be primarily physisorption and follows Freundlich's adsorption isotherm. The zero-cost and easy availability of waste tea leaves make it a substrate of interest that can be used for the cost-effective removal of heavy metal ions from water and soil.

Heavy Metal Contamination in the Aquatic Ecosystem: Toxicity and Its Remediation Using Eco-Friendly Approaches

Urbanization and industrialization are responsible for environmental contamination in the air, water, and soil. These activities also generate large amounts of heavy metal ions in the environment, and these contaminants cause various types of health issues in humans and other animals. Hexavalent chromium, lead, and cadmium are toxic heavy metal ions that come into the environment through several industrial processes, such as tanning, electroplating, coal mining, agricultural activities, the steel industry, and chrome plating. Several physical and chemical methods are generally used for the heavy metal decontamination of wastewater. These methods have some disadvantages, including the generation of secondary toxic sludge and high operational costs. Hence, there is a need to develop a cost-effective and eco-friendly method for the removal of heavy metal ions from polluted areas. Biological methods are generally considered eco-friendly and cost-effective. This review focuses on heavy metal contamination, its toxicity, and eco-friendly approaches for the removal of heavy metals from contaminated sites.

Theoretical study of M2CO2 MXenes stability and adsorption properties for heavy metals ions removal from water

Heavy-metals ions are one of the reasons to cause the pollution of water. The toxic heavy metal ions, such as Pb2+ and Cu2+, have been aroused worldwide concern due to their high toxicity and carcinogenicity. Two-dimensional (2D) transition metal carbide materials (MXenes) exhibit the hydrophilic surface, and the excellent chemistry stabilities, and can be the potential materials for water decontamination field. Here, by using density functional theory calculations, the adsorption behaviors of heavy metals, Ag, Au, Cu, Pb, and Zn on M2CO2 (M = Sc, Ti, V, Cr, Zr, Nb, Mo, Ta, and W) are investigated. Results show that Pb can stably be adsorbed on V2CO2, Cr2CO2, and Zr2CO2 MXenes with the corresponding adsorption energy lower than 0 eV. Densities of states and charge transfers analysis show that the hybridization of O* p orbital with Pb p and d orbitals promote the binding strength of M2CO2 (M = V, Cr, Zr) with Pb. In addition, it shows that the high Pb coverage on M2CO2, the F mixed in the terminal O* of M2CO2, and the strain in M2CO2 can alter the adsorption ability of M2CO2 for Pb. Ab initio molecular dynamics (AIMD) simulations results indicate that the adsorbed Pb on the M2CO2 cannot aggregate into clusters at conducting temperature (300 K). Moreover, the results of the reaction energy, the binding energy, and the formation energy of hydrated Pb2+ ([PbH2On]2+) on M2CO2, and the change of bond lengths of Pb-O, dPb-O in ([PbH2On]2+) indicate that the Pb2+ can be efficiently removed from waste water even it was hydrated into [PbH2On]2+. This work illustrates that the 2D MXenes can be the promising materials for the removal of toxic metals (such as Pb2+) from water.

Synthesis of a Novel Hydrazone Functionality based Spectrophotometric Probe for Selective and Sensitive Estimation of Toxic Heavy Metal Ions

AbstractHeavy metal ions (HMIs), particularly Hg2+, Fe2+, Pb2+, and Cd2+, are toxic to biological systems. These HMIs display a wide distribution in aqueous systems, and due to their bioaccumulation tendency, their prevalence, even at very low concentrations, results in serious health issues in humans. This warrants the availability of easily affordable, reliable, quick, and sensitive approaches for real‐time monitoring of the concentration of HMIs in aqueous environments. Herein, we present the synthesis of a novel hydrazone functionality‐based chromogenic probe that ensures selective and sensitive spectrophotometric sensing of HMIs. More specifically, the synthesis of 3‐(2‐(2,4‐dinitrophenyl) hydrazono) Penta‐1,4‐diene‐1,5‐diyl) diphenol referred to as HZ in the MS through a two‐step approach via the low‐cost precursors viz. Salicaldehyde, acetone, and 2, 4‐dinitrophenyl hydrazine (2, 4‐DNP) is presented. The unique functionality of the as‐synthesized HZ, well‐characterized via spectroscopic approaches, is demonstrated to facilitate the spectrophotometric sensing of Hg2+, Fe2+, Pb2+, and Cd2+ with detection limits as low as 0.74 μM, 1.46 μM, 0.75 μM, and 0.75 nM respectively. Importantly the spectrophotometric response of HZ is demonstrated to be very sensitive to the nature of HMI, which does ensure selective specification of the chosen HMIs. The sensing ability of the HZ is well within concentration ranges that include WHO‐recommended safe and toxic concentrations for these HMIs.

Efficient Visible-Light-Driven Tetracycline Degradation and Cr(VI) Reduction over a LaNi1-xFexO3 (0 ≤ x ≤ 1)/g-C3N4 Type-II Heterojunction Photocatalyst.

The development of efficient, stable, and visible-light-responsive photocatalysts is crucial to address the pollution of water bodies by toxic heavy metal ions and organic antibiotics. Herein, a series of LaNi1-xFexO3/g-C3N4 heterojunction photocatalysts are prepared by a simple wet chemical method. Moreover, LaNi0.8Fe0.2O3/g-C3N4 composites are characterized by various methods, including structure, morphology, optical, and electrochemical methods and tetracycline degradation and photocatalytic reduction of Cr(VI) under visible light irradiation. Then, the photocatalytic performance of as-prepared LaNi0.8Fe0.2O3/g-C3N4 composites is evaluated. Compared with pure LaNi0.8Fe0.2O3 and g-C3N4, the LaNi0.8Fe0.2O3/g-C3N4 composite photocatalysts exhibit excellent photocatalytic performance due to synergy of doping and constructing heterojunctions. The results show that the doping of Fe ions can increase the concentration of oxygen vacancies, which is ultimately beneficial to the formation of electron traps. Moreover, the type-II heterojunction formed between LaNi0.8Fe0.2O3 and g-C3N4 effectively strengthens the separation and transfer of photoinduced carriers, thereby promoting photocatalytic activity. Furthermore, the photocatalytic activity of the LaNi0.8Fe0.2O3/g-C3N4 photocatalyst remains almost unchanged after three cycles, indicating long-term stability. Ultimately, the photocatalytic mechanism of the LaNi0.8Fe0.2O3/g-C3N4 composites is proposed.

Simple, universal colorimetric strategy for amplified detection of nanomolar toxic heavy metal ions based on multi-component complexation and Tyndall effect

This work describes a new class of universal nanoprobe-free colorimetric assay with Tyndall effect (TE) signaling for amplified detection of nanomolar heavy metal ions based on analyte-triggered multi-component complexation. In the presence of NH2OH·HCl, Cu2+ (model analyte) is reduced to Cu+ which in turn reacts with KSCN and CHClN2O3 to form colloidal three-component complexation particles unexpectedly producing an enhanced TE signal with the aid of a 635 nm laser pointer. The results show that the developed method could detect Cu2+ in a linear concentration range of 156 nM ∼ 120 µM with a limit of detection (LOD) of ∼38 nM (3σ) using a smartphone for quantitative readout. The generality of the new equipment-free strategy was demonstrated well with selective detection of Cd2+ as the second model analyte with a LOD down to ∼1.27 nM where KI and CHClN2O3 were adopted as the three-component complexation reagents. In addition, satisfying recovery results obtained from analysis of Cu2+ and Cd2+ in several polluted real water samples ranged from 93.1% to 104.67% and 93.21–101.85%, respectively. To the best of our knowledge, this may be the first report of nanoprobe-free TE-based colorimetric assay based on multi-component complexation.

Design, synthesis, and nanoengineered modification of spherical graphene surface by layered double hydroxide (LDH) for removal of As(III) from aqueous solutions

In this study, new nano spherical graphene modified with LDH (Layered Double Hydroxide) was prepared and used to remove As(III) ion from aqueous solutions. At first, graphene oxide was synthesized from graphite using a well-known Hammer method. The obtained graphene oxide solution was sprayed in octanol solution under different temperatures and sprayed speed as influenced variables. The structure and physical characterization of synthesized spherical graphene oxide were determined by various techniques, including FT-IR, N2 adsorption-desorption, SEM, TEM, and EDX. In the next step, the hydrothermal method was applied to deposition LDH on the spherical graphene oxide. The synthesized spherical graphene modified by LDH was used to remove As(III) as a toxic heavy metal ion. The effect of influenced variables including pH, contact time, amount of sorbent, and type eleunt studied and the optimum values were as 8, 30, 50, and HCl (0.5 mol·L−1), respectively. After optimization, the studied sorbent was shown a high adsorption capacity (149.3 mg·g−1). The adsorption mechanism and kinetic models exhibited good agreement with the Langmuir isotherm and pseudo-second-order trends, respectively. Besides, the synthesized product was tested for seven times without significant loss in its sorption efficiency.

Crystal graph convolution neural networks for fast and accurate prediction of adsorption ability of Nb2CTx towards Pb(ii) and Cd(ii) ions

Precisely measuring the adsorption capability of materials towards toxic heavy metal ions in aqueous solution is essential for the synthesis of effective novel adsorbents.

A Novel Electrodialysis Membrane, Modified by Polydopamine and Carbon Nanofibers, Removes Toxic Heavy Metal Ions From Wastewaters

Background: In light of severe and growing shortages of clean water and the rising environmental pollution in many countries, seawater desalination has been an effective method to produce freshwater. Cationic membranes have enabled environmental scientists to effectively remove toxic heavy metals from wastewater and to regenerate freshwater. Methods: We used a novel method, involving electro- and physico-chemical membranes to successfully remove toxic heavy metal ions (copper & chromium) from wastewater samples. Specifically, Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, surface wettability, flux, selectivity and electrical resistance measurements were applied to conduct this study. Results: The obtained results illustrated relatively uniform foaming of the modified membranes. Also, electron microscopic images indicated almost even distribution of the particles. The dada indicated that applying polydopamine layer and incorporating nanofibers in monomer solution caused surface hydrophilic enhancement. Also, increased carbon nanofibers loading ratio to 0.07% raised the ionic flux. The data also showed a higher capacity in the modified membranes for the removal of copper and chromium ions from the wastewater samples. Although the surface modified membranes displayed a higher flux and lower permselectivity to some extents, utilizing nanoparticles led to a steady trend of ion elimination. Generally, carbon nanofibers incorporation to the membrane surface modified samples up to 0.1% weight, resulting in nearly a constant areal electrical resistance. Conclusion: The novel method developed by this study is an excellent candidate with high potential for the removal of toxic heavy metal ions from wastewater samples.

A supramolecular fluorescence array sensor for toxic heavy metal ion detection in environmental water and rice seedling extracts.

A supramolecular fluorescence array sensor based on cucurbituril-dye host-guest complexes (6-QAA@Q[7], PyY@Q[7], and TO@Q[8]) was constructed. The results showed that it can quickly identify and detect toxic heavy metal ions, such as Ag+, Cr3+, Hg2+, Ni2+, and Pb2+. When these five toxic heavy metal ions were added to the supramolecular fluorescence array sensor, different fluorescence responses were produced due to the different binding capacities of the metal ions to the cucurbituril-dye complex. Linear discriminant analysis (LDA) showed that the supramolecular fluorescence array sensor could identify and distinguish these five toxic heavy metal ions and a mixture containing different concentration ratios could be classified. The linear correlation between the metal ion concentration and factor 1 (F1) was strong, and the detection limit (LOD) was as low as 10-6-10-7 mol L-1. These five toxic heavy metal ions in environmental water and rice seedling extracts were identified using the supramolecular fluorescence array sensor. This sensor provides a quick and convenient method for monitoring toxic heavy metal ions in sewage.

Recent progress on detection of bivalent, trivalent, and hexavalent toxic heavy metal ions in water using metallic nanoparticles: A review

Most of the metal ions are carcinogens and lead to serious health concerns by producing free radicals. Contamination of drinking water sources with heavy metals has a harmful impact on the environment and human health. The most commonly used heavy metals are zinc (Zn), copper (Cu), lead (Pb), tin (Sn), cadmium (Cd), chromium (Cr), iron (Fe), and mercury (Hg), etc. The heavy metal ions are easily absorbed by living things via water and spread throughout the food chain, posing a threat to humans, plants, and animals. Hence, fast and accurate detection of metal ions has become a critical issue. Among various metal ions arsenic, cadmium, lead, mercury and chromium are considered to be highly toxic. To detect these metal ions, colorometric, fluorometric and electrochemical biosensors with interfaces such as nanomaterials like especially metal nanoparticles including gold, silver, copper nanoparticles have been developed. Among these, nanomaterials are considered to be most promising, owing to their strong adsorption, fast electron transfer kinetics, and biocompatibility, which are very apt for biosensing applications. The coupling of various techniques with nanomaterials has enhanced the sensitivity, limit of detection, and robustness of the sensors. In this review, the reduction of toxicity or removal of toxic metal ions from water by various techniques and various metal nanoparticles have been summarized. Also, different types of sensors employed in the detection of metal ions with various interfaces have been highlighted.

Highly sensitive surface acoustic wave biosensor for the detection of Hg2+ based on the thymine-Hg2+-thymine structure.

The detection of mercury ions (Hg2+) with an ultralow concentration is of great significance for the treatment of heavy metal pollution in industrial waste water and the monitoring of drinking water quality. In this study, a simple, sensitive, and portable surface acoustic wave (SAW) biosensor for the determination of Hg2+ concentration was developed. First, a DNA fragment with a specific binding capacity for Hg2+ was chemically adsorbed on to the sensitive region through forming Au-S bonds with the SAW biosensor. The DNA probe could then form a thymine-Hg2+-thymine (T-Hg2+-T) complex with strong affinity for Hg2+ after immersion in a test solution containing Hg2+, resulting in a significant change in the response frequency of the device. The linear detection range of the device was 10 pM to 1 nM, while the limit of detection (LOD) was as low as 6.3 pM. Furthermore, the SAW biosensor exhibited excellent selectivity to Hg2+ compared with that of interfering ions, e.g., Ag+, Ba2+, Cu2+, Zn2+, Mn2+, Fe3+, Ca2+, and Na+. The results provide a new strategy for the preparation of portable devices that can monitor toxic heavy metal ions with high sensitivity and selectivity.

Removal of toxic heavy metal ion from tannery effluent by using Fusarium subglutinans and Hylocereus undatus

Removal of toxic heavy metal ion from tannery effluent by using Fusarium subglutinans and Hylocereus undatus

Chromium (VI) reduction by two-chamber bioelectrochemical system with electrically conductive wall

Hexavalent chromium (Cr(VI)) poses a threat to public health and the environment owing to its high toxicity. Various microbial Cr(VI) reduction methods have been proposed to treat contaminated water; however, they are not effective at high concentrations of Cr(VI), which inhibit microbial growth and viability. To overcome the limitations of conventional microbial methods, we set up a novel bioelectrochemical reactor in which microbial cells were separated from Cr(VI) by an electroconductive barrier consisting of a vertically aligned carbon nanotube (VACNT) composite to remove toxic heavy metal ions. This study demonstrated that chromium compounds could be biologically and sustainably treated with the VACNT composite without growth inhibition, using electron transfer from an electron shuttle secreted by Pseudomonas aeruginosa, even at the microbial inhibitory concentration of Cr(VI). The content of Cr(VI) was measured using the diphenylcarbazide method, and Cr(III), the reduction product, was identified using X-ray photoelectron spectroscopy. Pyocyanin, a phenazine secreted by P. aeruginosa, was identified as an electron mediator in Cr(VI) reduction, using aeration and phz mutant assay. The bioelectrochemical reactor used in this study exhibited a Cr(VI) removal rate of 99.6% at 100 mg/L, which is the highest reduction rate achieved using P. aeruginosa. The microbial Cr(VI) reduction system developed in this study allows microbial Cr(VI) reduction to overcome the hurdles of biological treatment of toxic materials and has advanced the understanding of microbial electron transfer.

Microwave-assisted Synthesis, Characterization, Photocatalytic Degradation of Antibiotics, and Fluorometric Selective Sensing Activity of g-C3N4 Supported CuO Composites.

Herein, we have designed for the fabrication of a series of g-C3N4/CuO composite by using one-step microwave-assisted synthesis for the degradation of antibiotics and detection of nano-molar range of toxic heavy metal ions. The synthesized g-C3N4/CuO composites were analyzed and characterized to know the structure, phase, surface area, absorption region, bandgap, and size of the composites. From the observation of TEM and XRD measurements, g-C3N4/CuO composites have hexagonal shape with average diameter of the particles is 25 ± 5nm. The observed band gap values from UV-vis DRS for g-C3N4 nanosheets and CuO NPs are 2.64eV and 1.72eV. The synthesized g-C3N4/CuO composite has prodigious specific surface area (32.47 m2/g), which is the evident for superior heterogeneous catalytic applications. Therefore, the synthesized g-C3N4/CuO composites were tested for the degradation of antibiotics such as tetracycline (TC) and ciprofloxacin (CIP) under UV light illumination, it shows 88.02% and 90.01% degradation was observed within 1h due to the matching optical band gap and internal charge transfer of excitons with in the heterojunction surface among g-C3N4 and CuO in the composite than the individual components (g-C3N4 and CuO) due to the high surface area and tiny particles of CuO were randomly deposited on the surface of g-C3N4 nanosheets. The catalytic reduction reaction follows as pseudo-first order equation and reused for 5 consecutive cycles without remarkable loss of catalytic activity. Moreover, the synthesized CuO NPs and g-C3N4/CuO composites were used as a prominent fluorescence sensing probe for the selective detection of Pb2+ in nano-molar range of concentration with Ksv is 1.38 × 104mol- 1dm3. It was observed as a linear relationship based on the change in intensity, the limit of detection was determined to be 0.184 nM.

Toxic heavy metal ion detection by fluorescent nanocarbon sensor derived from a medicinal plant

In the twenty-first century, the importance of environmental pollution sensing cannot be overstated. Cadmium is a well-known poisonous heavy metal that seriously endangers human health. In terms of screening for poisons and diagnosing illnesses, the sensitive and focused detection of cadmium in cells is crucial. In this work, we developed Green fluorescent Carbon nanomaterial (Carbon nanomaterial) synthesized from a novel precursor, Justicia Wynaadensis, by the most eco-friendly, cost-effective hydrothermal method, which acts as a fluorescent probe for Cadmium fluorescence sensing technique with the concentration range of 1 nM–1 M. The sensor displays remarkable linear detection with a 5.235 nM detection limit.