Hazardous Heavy Metal Ions Research Articles

Efficient removal of environmentally hazardous heavy metal ions from water by NH2-MIL-101-Fe and MOF-808-EDTA based polyether sulfone adsorbents

The potential of metal–organic frameworks (MOFs) based polymeric composites for heavy metal removal was analyzed in this study. Two mixed matrix composites, along with NH2-MIL-101-Fe and MOF-808-EDTA, were synthesized. The MOFs were synthesized using the solvothermal method, and the mixed matrix spheres (MMSs) were prepared using the facile dropping method. The MMSs were characterized, and batch adsorption studies were performed at different pH and adsorbent dosages. For both MMSs, the optimum pH was between 5–5.5, and the highest removal rates were obtained for MOF-808-EDTA spheres (94 % Hg2+, 86 % As, 80 % Mn). The optimum adsorbent dosage for MOF-808-EDTA was found to be 5.42 g/L, while for NH2-MIL-101-Fe, it was 7.13 g/L, after which the metal ion removal efficiency was reduced. Langmuir adsorption isotherm was fitted with thermodynamic evaluation of Gibbs free energy, enthalpy, and entropy. MOF-808-EDTA demonstrated a greater adsorption capacity of 272.7 mg/g (Hg2+), 151.29 mg/g (As3+), and 125.9 mg/g (Mn2+) than the other MMP. The Gibbs free energy of −20.14 (Hg2+), −12.66 (Mn2+), and −52.61 kJ/mol (As3+) were obtained from the thermodynamic study. The results indicated that the process was exothermic and spontaneous. Breakthrough column studies were performed for MOF-808-EDTA spheres using the pore-surface-diffusion model. The transient column study was conducted for individual heavy metal ion solutions using Addesign™ software to evaluate column exhaustion time, breakthrough time and length of mass transfer zone. Studies with multicomponent solutions of heavy metals also gave potentially promising results in the separation of 92 % of Hg, 84 % As, and 75 % Mn which indicates the prepared adsorbents can be used to remove heavy metal ions from industrial wastewater samples.

Surface functionalization of oil palm empty fruit bunch (OPEFB)-derived cellulose as a carboxyl platform for metal cations and dyes removal from aquatic media

The abundant oil palm empty fruit bunch (OPEFB) as by-product of palm oil milling processes exhibits a potential as an alternative cellulose feedstock for bio-adsorbent. This study aimed to produce a highly carboxylated bio-adsorbent for direct industrial application from OPEFB-based cellulose via mercerization and followed by esterification with succinic anhydride (SA) to enhance its adsorptive capability towards hazardous heavy metal and dyes ions. The modification using SA provides the carbon backbone platform for carboxyl group attachment for the contaminants. The results showed that the carboxylated cellulose had a high carboxyl content (4.39 mmol/g). Carboxylated cellulose had a higher binding capacity for adsorbates, with removal rates of 94.7%, 97.85%, 40.9%, and 90.15% for dye, Pb2+, Cu2+, and Cd2+ cations, respectively, at pH 6, 4 hours reaction time, and at room temperature. In comparison, unmodified cellulose removed only 47%, 23.1%, 2.9%, and 7.5% for dye, Pb2+, Cu2+, and Cd2+ cations, respectively. The adsorption kinetics study revealed that the adsorption process followed the pseudo-second-order model. The adsorption isotherm of these two metal cations follows the model of Langmuir very well, while Cu2+ follows the Freundlich model. Our method produces bio-adsorbents with high carboxyl content and adsorption rate in a short reaction time using OPEFB as a green precursor material that is easily scalable for industrial use.

Hyperconfined bio-inspired Polymers in Integrative Flow-Through Systems for Highly Selective Removal of Heavy Metal Ions

Access to clean water, hygiene, and sanitation is becoming an increasingly pressing global demand, particularly owing to rapid population growth and urbanization. Phytoremediation utilizes a highly conserved phytochelatin in plants, which captures hazardous heavy metal ions from aquatic environments and sequesters them in vacuoles. Herein, we report the design of phytochelatin-inspired copolymers containing carboxylate and thiolate moieties. Titration calorimetry results indicate that the coexistence of both moieties is essential for the excellent Cd2+ ion-capturing capacity of the copolymers. The obtained dissociation constant, KD ~ 1 nM for Cd2+ ion, is four-to-five orders of magnitude higher than that for peptides mimicking the sequence of endogenous phytochelatin. Furthermore, infrared and nuclear magnetic resonance spectroscopy results unravel the mechanism underlying complex formation at the molecular level. The grafting of 0.1 g bio-inspired copolymers onto silica microparticles and cellulose membranes helps concentrate the copolymer-coated microparticles in ≈3 mL volume to remove Cd2+ ions from 0.3 L of water within 1 h to the drinking water level (<0.03 µM). The obtained results suggest that hyperconfinement of bio-inspired polymers in flow-through systems can be applied for the highly selective removal of harmful contaminants from the environmental water.

Non-Faradaic Impedimetric Detection of Heavy Metal Ions via a Hybrid Nanoparticle-DNAzyme Biosensor.

Due to rapid industrialization, novel water-quality monitoring techniques for the detection of highly toxic and hazardous heavy metal ions are essential. Herein, a hybrid noble nanoparticle/DNAzyme electrochemical biosensor is proposed for the simultaneous and label-free detection of Pb2+ and Cr3+ in aqueous solutions. The sensor is based on the combination of a two-dimensional naked-platinum nanoparticle film and DNAzymes, whose double-helix configuration disassembles into smaller fragments in the presence of target-specific heavy metal ions. The electrochemical behavior of the fabricated sensor was investigated with non-faradaic electrochemical impedance spectroscopy (EIS), resulting in the successful detection of Pb2+ and Cr3+ well below their maximum permitted levels in tap water. So far, there has been no report on the successful detection of heavy metal ions utilizing the non-faradaic electrochemical impedance spectroscopy technique based on advanced nanomaterials paired with DNAzymes. This is also one of the few reports on the successful detection of chromium (III) via a sensor incorporating DNAzymes.

N,N’-bis(3-dithiocarbamatopropyl) piperazine bridged metallomacrocyclic complexes of Ni(II), Cu(II) and Zn(II): Synthesis, characterization, photophysical, in-silico study and their potential utility in heavy metal ion sensing

Two secondary diamines viz. N,N’-bis{3-(p-methoxybenzylamino)propyl}piperazine (H2L1) and N,N’-bis{3-(p-chlorobenzylamino)propyl}piperazine (H2L2) holding N,N’-bispropylpiperazine linkers have been prepared and subsequently used to derive a new series of N,N’-bis(3-dithiocarbamatopropyl) piperazine bridged metallomacrocyclic complexes [M(II)2-µ2-bis-{(κ2S,S-S2CN(R)C3H6)2piperazine}] wherein R = p-methoxybenzyl, M = Ni(II) 1, Cu(II) 2, Zn(II) 3; R = p-chlorobenzyl, M = Ni(II) 4, Cu(II) 5, Zn(II) 6. The formation and purity of all the metallomacrocyclic dithiocarbamate complexes were verified by microanalysis and standard methods such as HRMS, NMR, IR and UV–Visible absorption spectroscopy and corroborated by density functional theory calculations. The experimental (magnetic susceptibility and UV–Visible) and theoretical calculations suggest a square planar/distorted square planar environment around nickel(II)/copper(II) and tetrahedral/distorted tetrahedral environment around zinc(II) centres in 1–6. Thermogravimetric study was carried out on 1–6 to study their thermal stability and degradation behaviour. Notably, TG curves of compounds 2, 3 and 5 gave a stable residual mass corresponding to corresponding metal sulphides (MS). Notably, the calculated HOMO-LUMO gaps (1.19–1.33 eV) for Cu(II)-dithiocarbamate 2 and 5 indicates their semiconducting nature. The potentials of these metallomacrocycles as a molecular probe for optical sensing of environmentally hazardous heavy metal ions ca Pb(II), Cd(II) and Hg(II) were further examined by using UV–Visible and fluorescence spectroscopies.

Thioglycolic acid capped CdSe/ZnS quantum dot as fluorescent sensor for the detection of water-soluble hazardous heavy metal ions

Thioglycolic acid capped CdSe/ZnS quantum dot as fluorescent sensor for the detection of water-soluble hazardous heavy metal ions

Chitosan-assisted self-assembly of flower-shaped ε-Fe2O3 nanoparticles on screen-printed carbon electrode for Impedimetric detection of Cd2+, Pb2+, and Hg2+ heavy metal ions in various water samples

This study focuses on the fabrication of a novel sensing platform on a screen-printed carbon electrode, modified by a combination of hydrothermally synthesized iron dioxide (ε-Fe2O3) nanoparticles and Chitosan (CS) biopolymer. This unique organic-inorganic hybrid material was developed for Electrochemical Impedance Spectroscopy (EIS) sensing, specifically targeting heavy metal ions that include Hg2+, Cd2+, as well as Pb2+. The investigation encompassed a comprehensive analysis of various aspects of the prepared Fe2O3 and CS/ε-Fe2O3 nanocomposites, including phase identification, determination of crystallite size, assessment of surface morphology, etc. CS/ε-Fe2O3 was drop-casted and deposited on the Screen-Printed Electrode (SPE). The resulting sensor exhibited excellent performance in the precise and selective quantification of Hg2+, Cd2+, and Pb2+ ions, with minimal interference from other substances. The fabricated sensor exhibits excellent performance as the detection range for Hg2+, Cd2+, and Pb2+ ions linearity is 2–20 μM, sensitivity, and LOD are 243 Ω/ μM cm2 and 0.191 μM, 191 Ω/μM cm2, and 0.167 μM, 879 Ω/ μM cm2, and 0.177 μM respectively. The stability of the CS/ε-Fe2O3/SPE electrode is demonstrated by checking its conductivity for up to 60 days for Hg2+, Cd2+, and Pb2+ ions. The reusability of the fabricated electrode is 14 scans, 13 scans, and 12 scans for Hg2+, Cd2+, and Pb2+ ions respectively. The findings indicate the successful development of an innovative CS/ε-Fe2O3 electrode for the EIS sensing platform. This platform demonstrates notable potential for addressing the critical need for efficient and sensitive EIS sensors capable of detecting a range of hazardous heavy metal ions, including Hg2+, Cd2+, and Pb2+.

Gold Nanoparticle-Modified Carbon-Fiber Microelectrodes for the Electrochemical Detection of Cd2+ via Fast-Scan Cyclic Voltammetry.

Neurotoxic heavy metals, such as Cd2+, pose a significant global health concern due to their increased environmental contamination and subsequent detrimental health hazards they pose to human beings. These metal ions can breach the blood-brain barrierblood-brain barrier, leading to severe and often irreversible damage to the central nervous system and other vital organs. Therefore, developing a highly sensitive, robust, and rapid in vivo detection method for these hazardous heavy metal ions is of the utmost importance for early detection, thus initiating timely therapeutics. Detecting ultra-low levels of toxic metal ions in vivo and obtaining accurate speciation information remains a challenge with conventional analytical techniques. In this study, we fabricated a novel carbon carbon-fiber microelectrode (CFM)-based sensor that can detect Cd2+ ions using fast-scan cyclic voltammetry by electrodepositing gold nanoparticles (AuNP). We optimized electrochemical parameters that generate a unique cyclic voltammogram (CV) of Cd2+ at a temporal resolution of 100 ms with our novel sensor. All our experiments were performed in tris buffer that mimics the artificial cerebellum fluid. We established a calibration curve resulting in a limit of detection (LOD) of 0.01 µM with a corresponding sensitivity of 418.02 nA/ µM. The sensor's selectivity was evaluated in the presence of other metal ions, and it was noteworthy to observe that the sensor retained its ability to produce the distinctive Cd2+ CV, even when the concentration of other metal ions was 200 times higher than that of Cd2+. We also found that our sensor could detect free Cd2+ ions in the presence of complexing agents. Furthermore, we analyzed the solution chemistry of each of those Cd2+-ligand solutions using a geochemical model, PHREEQC. The concentrations of free Cd2+ ions determined through our electrochemical data align well with geochemical modeling data, thus validating the response of our novel sensor. Furthermore, we reassessed our sensor's LOD in tris buffer based on the concentration of free Cd2+ ions determined through PHREEQC analysis, revealing an LOD of 0.00132 µM. We also demonstrated the capability of our sensor to detect Cd2+ ions in artificial urine samples, showcasing its potential for application in actual biological samples. To the best of our knowledge, this is the first AuNP-modified, CFM-based Cd2+ sensor capable of detecting ultra-low concentrations of free Cd2+ ions in different complex matrices, including artificial urine at a temporal resolution of 100 ms, making it an excellent analytical tool for future real-time, in vivo detection, particularly in the brain.

Comprehensive assessment of carbon-, biomaterial- and inorganic-based adsorbents for the removal of the most hazardous heavy metal ions from wastewater.

Owing to the high cost of recycling waste, underdeveloped countries discharge industrial, agricultural, and anthropogenic effluents without pretreatment. As a result, pollutant-loaded waste enters water bodies. Among the diverse toxic contaminants, heavy metal ions are the most detrimental because of their chronic toxicity, non-degradability, prevalence, and bioaccumulation. The growing shortage of water resources demands the removal of heavy metal ions from wastewater. Three SDGs of the sustainability agenda of the United Nations appeal for clean water to protect life beneath water and on land depending on the water sources. Therefore, efficient environmentally friendly approaches for wastewater treatment are urgently required. In this regard, several methods have been developed for the removal of heavy metal ions from wastewater, including adsorption as the most widely used method owing to its eco-friendly, cost-effective, and sustainable nature. The present review discusses the progress in the preparation and application of various adsorbents based on carbon, micro-organisms, agricultural waste and inorganic materials for the extraction of toxic metal ions such as Pb2+, Cr6+, As3+, As5+, Hg2+ and Cd2+. Herein, we provide information on the role of the homogeneity and heterogeneity of adsorbents, kinetics of the adsorption of an adsorbate on the surface of an adsorbent, insights into adsorption reaction pathways, the mechanism of the sorption process, and the uptake of solutes from solution. The present review will be useful for researchers working on environmental protection and clean environment.

A dual template ion imprinted polymer based on acrylamide monomer/modified graphene oxide for simultaneous adsorption of Ni (II)/Cd (II)

Utilizing ion imprinted polymers (IIPs) to target hazardous heavy metal ions presents an effective solution for addressing water pollution by recognizing and adsorbing specific metal cations. Although dual-template IIPs can...

Surface Functionalized Mesoporous Silica Nanoparticles for Enhanced Removal of Heavy Metals: A Review

Human health and environmental sustainability are strongly influenced by the contamination of water resources with hazardous heavy metal ions due to the accumulation in human body via food chains. Thereby, researchers’ attention has been paid on effective methods for heavy metal ion scavenging to prevent them releasing to environment. Notably, Mesoporous Silica Nanoparticles (MSNPs) with high surface area, massive surface area to volume ratio, large pore volume and uniform pore distribution play a crucial role in addressing this challenge. Additionally, researchers focus on novel surface functionalization methods of MSNPs with suitable organic and inorganic moieties to amplify the adsorption efficiency of heavy metals. MSNPs possess easily functionalizable surface which facilitates the modifications and enhanced removal of heavy metals. The review article summarizes the different moieties used for functionalization of MSNPs such as amino, thio, carboxyl, phenyl, cyano groups, different types of polymers, inorganic functional groups. Further, a comparison has been made between functional and unmodified MSNPs to elaborate how these modifications have enhanced the removal performance of heavy metals in water. Further, this review provides an overview on different synthesis routes and structure directing agent used in synthesis of MSNPs. Moreover, pH effect on adsorption andreusability of modified NPs, while illustrating the mechanism of adsorption on to modified MSNPs surface has also been elaborated. Maximum adsorption capacity of each functional moiety has been taken into consideration with the aim of supporting future advancements.&#x0D; Keywords: Adsorption, Mesoporous silica nanoparticles, Heavy metals, Functionalization, Maximum adsorption capacity

Preparation and characterization of ball milled hexagonal‑boron nitride (BMBN) and fluorescein (FL) decorated reduced graphene oxide (RGO) nanocomposite towards toxic heavy metal ion detection

In the present work, a novel hybrid fluorescent nanocomposite (RBF) based on ball milled hexagonal-Boron Nitride (BMBN) and Fluorescein (FL) decorated reduced Graphene Oxide (RGO) was synthesized for the effective detection and removal of hazardous heavy metal ions present in effluents. Where two different textile effluents namely, reaction outlet and factory outlet collected at the river Noyyel, Tamilnadu were considered. The prepared RBF was subjected to XRD, FTIR, SEM, EDX, TEM, PSA, BET, UV–vis, PL and XPS studies which strongly confirm the decoration of FL and BMBN at the surface of RGO sheets. The selectivity of RBF was examined by considering various toxic heavy metal ions. Where the RBF exhibits remarkable sensing towards Zn2+ (10.7 nM) via enhanced fluorescence and for Fe3+ (15.6 nM), Sn4+ (60.7 nM) and Hg2+ (465.4 nM) ions by “Turn-off” fluorescence only at neutral pH. In addition, the RBF was highly efficient to remove Hg (81.3 %) than Zn (63.7 %), Fe (38.2 %) and Sn (62.9 %) in real-time samples. Moreover, the prepared RBF could also serve as water sensor for the water contaminated organic solvents of Acetonitrile (ACN) and Tetrahydrofuran (THF). Hence the prepared RBF might be a potential choice for the effective detection and removal of heavy metal ions during wastewater treatment.

Cadmium(II) adsorption with ZIF-8 nanocrystals of different morphology

The food safety and human health have been seriously threatened by water pollution with heavy metals. Metal-organic framework (MOF) is considered as one of the promising adsorbents for decontamination of heavy-metal-containing water owing to ordered structure with high porosity. In this work, ZIF-8 nanocrystals with different morphologies (ZIF-RD, ZIF-TD and ZIF-L) were obtained by simply adjusting the synthesis process and precisely characterized via XRD, BET, SEM, FT-IR and XPS. The as-synthesized samples were used for adsorption of Cd2+ to measure the adsorption behavior. The largest Cd2+ adsorption capacity was achieved on truncated-dodecahedral ZIF-8 sample with the qe of 73.8 mg/g, whereas the rhombic dodecahedral ZIF-8 with the largest surface area showed the poorest adsorption performance. Adsorption mechanism study revealed that the Cd2+ adsorption on three ZIF-based materials involves chemical adsorption process. Moreover, ZIF-8 chelates with Cd2+ ions primarily through N-containing groups on the MOF skeleton. Our findings also proved that the specific area of adsorbents does not necessarily ensure the efficiency for removing hazardous heavy metal ions.

Effect of Pyrolysis Temperature of Coconut Fibre Biochar Incorporated in Zn/Al Layered Double Hydroxide for the Removal of Nickel(II)

Coconut-fiber biochar (CCFB) pyrolyzed at different pyrolysis temperatures (400°C, 500°C, and 600°C) that immobilized Zn/Al layered double hydroxides (Zn/Al LDH-CCFB) composite adsorbent was prepared via a simple co-precipitation technique. The composite adsorbents were used to reduce the high concentration of Ni(II) metal ions from aqueous solution. The morphological analysis was investigated scanning electron microscopy (SEM). A series of batch adsorption tests was conducted with different parameters, which cover the pH of the solution (3–7), initial concentration of Ni(II) (10–250 mg/L), and contact time of the shaking time (0.16–8 h). Pseudo-second order kinetic model was well fitted for all of the samples, compared to pseudo-first order and intraparticle diffusion kinetic models, with the value of R2 = 0.9993, 0.9719, 0.9924, and 0.9978 for Zn/Al LDH-0, Zn/Al LDH-CCFB400, Zn/Al LDH-CCFB500, and Zn/Al LDH-CCFB600, respectively. Meanwhile, the adsorption process was best described by the Freundlich model with the value of R2 = 0.9311, 0.9987, 0.9843, and 0.9981 for Zn/Al LDH-0, Zn/Al LDH-CCFB400, Zn/Al LDH-CCFB500, and Zn/Al LDH-CCFB600, respectively. From the adsorption performance test, it was found that the adsorption capacity of Zn/Al LDH-CCFB500 that was agitated for 4 h at pH 7 was higher compared with other samples, demonstrating an adsorption capacity of up to 106.95 mg/g. The adsorption capacity of all of the Zn/Al LDH-CCFB had improved, compared to pristine Zn/Al LDH-0. Thus, it is concluded that Zn/Al LDH-CCFB possesses a great potential for the adsorbent in the removal of pollutants, especially the hazardous heavy metal ions.

Effect of reaction parameters on Arsenic removal capacity from aqueous solutions using modified magnetic PU foam nanocomposite

A novel Fe3O4 -polyurethane (PU) foam nanocomposite was fabricated and utilized to study the removal of heavy metal ions from water. Magnetite (Fe3O4) nanoparticles with (3-Aminopropyl) triethoxysilane (APTES) was synthesized and incorporated into polyurethane foam. Different characterization methods, such as TEM, BET, EDS, SEM and optical microscopy, were used to evaluate the properties of synthesized nanoparticles and modified foam. The effects of experimental parameters, such as reaction time, adsorbent weight, pH level, and arsenic concentration on the performance of modified PU toward removal of arsenic removal, were investigated. Furthermore, the performance of the modified nanocomposite foam for removal of other heavy metal ions, such as Zn and Cd, was studied under the same optimum reaction condition. The modified magnetite polyurethane foam nanocomposite demonstrated remarkable adsorption capacity for arsenic species with good stability and reusability after five successive adsorption/desorption cycles. The findings of this study suggest that Fe3O4@APTES-PU foam can be further modified to remove other forms of hazardous heavy metal ions from wastewater and drinking water.

Ag decorated Zn-Al layered double hydroxide for adsorptive removal of heavy metals and antimicrobial activity: Numerical investigations, statistical analysis and kinetic studies

Ag nanoparticles have been decorated with Zn-Al layered double hydroxide (LDH) using a simple synthetic procedure. The structural and morphological characterization result confirms the formation of the layered structure Ag@Zn-Al LDH. Ag@Zn-Al LDH has been evaluated for adsorptive elimination of hazardous heavy metal ions like Pb2+ and Cd2+ from an aqueous solution. pH, initial concentration, and contact time are well-studied adsorption conditions as independent variables. The Response Surface Model was used to describe the optimization of the variables (RSM). The optimal conditions for Pb2+ and Cd2+ removal under the constraints are 200 ppm heavy metal levels (concentration), pH 8.0, a reaction duration of 90 min, and a response of 98.9 % by Ag@Zn-Al LDH. With exceptional adsorption efficiencies of 537.63 and 401.62 mg/g, the Langmuir isotherm fitted the adsorption of Pb2+ and Cd2+ well. Studies on thermodynamics demonstrate the exothermic spontaneity and pseudo-second-order kinetic model was determined to be more appropriate. Ag@Zn-Al LDH exhibits more antibacterial activity than Zn-Al LDH, with MIC values that are similar to those of standard streptomycin. The examination indicates that the synthesised Ag@Zn-Al LDH has good adsorption and antibacterial activity.

Adsorption of Heavy Metals on Bentonitic Soil for Use in Landfill Liners

Hazardous heavy metal ions such as copper, zinc, nickel, chromium, cadmium, and lead engender a potential risk to human health. Among the processes involved in the retention of these contaminants, adsorption is advantageous for removing toxic metals because of its environmentally friendly aspect, efficiency, and low-cost operation. Information on the adsorption of heavy metals in soils from the semiarid region of northeastern Brazil is still scarce. In this study, the adsorption of heavy metals (Cd, Cu, Zn, Ni, and Pb) by a semiarid Brazilian bentonitic soil is investigated. This soil has been used as a bottom liner in an experimental municipal solid waste (MSW) cell located in Campina Grande, State of Paraíba, Brazil. The experimental cell consists of a landfill unit on an experimental scale, with the same constructive elements of a sanitary landfill. Disturbed and undisturbed samples of the investigated soil were collected at a quarry in the rural zone of Boa Vista (state of Paraiba, Northeast Brazil). Sorption attributes were determined via batch tests with a soil-solution ratio of 1 : 12.5 (4 g of dry soil to 50 mL of solution). Linear, Freundlich, and Langmuir isotherms were fitted to the experimental data, using as fitting parameters Pearson correlation coefficient ([Formula: see text]) and [Formula: see text] value with a significance level [Formula: see text]. The ascending order of maximum adsorption capacity for heavy metals followed the series Ni &lt; Cr &lt; Zn &lt; Cd &lt; Cu &lt; Pb. The maximum adsorbent capacities obtained were similar to those of other Brazilian soils and other adsorbents. Therefore, the studied soil has a high potential to be used in the retention of heavy metals.

A novel three-dimensional electrochemical Cd(II) biosensor based on l-glutathione capped poly(3,4-ethylenedioxythiophene):polystyrene sulfonate/carboxylated multiwall CNT network

The increased water contamination caused by heavy metal ions has negative consequences for human beings. The majority of these metal ions are incredibly poisonous, nonbiodegradable, and bioaccumulative. Therefore, detection of these hazardous heavy metal ions is crucial in the current situation. The sensing mechanism of electrochemical biosensors must be understood to increase the sensing performance such as selectivity, sensitivity, detection limit, repeatability, and reproducibility for application scenarios. The present investigation demonstrates the preparation of L-Glutathione modified Poly (3,4-ethylenedioxythiophene): polystyrene sulfonate/carboxylated multiwall carbon nanotubes (LGSH@PEDOT:PSS/MWCNTs-COOH) network by the solution processing method. The efficacy of the LGSH@PEDOT: PSS/MWCNTs-COOH network has been investigated using GIXRD, Raman, UV-Vis, FT-IR, AFM, CV, and EIS. The detection capability of the LGSH@PEDOT: PSS/MWCNTs-COOH network as a biosensor has been investigated utilizing the DPASV technique. The presented Cd(II) biosensor exhibited a sensitivity of 10.69 μA/ppm and a detection limit of 1 ppb. Moreover, the developed biosensor exhibited good selectivity, repeatability (RSD = 1.83%), and reproducibility (RSD = 4.73%). These favorable results make LGSH@PEDOT: PSS/MWCNTs-COOH electrode as an excellent Cd(II) ions detection probe as the next generation electrochemical biosensor to detect lungs, kidney, and breast cancers.

Polydopamine-assisted polyethyleneimine grafting on electrospun cellulose acetate/TiO2 fibers towards highly efficient removal of Cr(VI)

Highly efficiently removing hazardous heavy metal ions from water is very important from a viewpoint of maintaining the sustainable development of ecological environment. In this work, a novel adsorbent based on the cellulose acetate (CA) was developed, which was fabricated through the blend electrospinning of CA and titanium dioxide (TiO2) nanoparticles, surface modification by polydopamine (PDA) and then grafted by polyethyleneimine (PEI). The composite CA/TiO2 electrospun fibers exhibit the porous structure, while the surface modification by PDA-assisted PEI grafting has no apparent effect on morphology of the electrospun fibers. The CA/TiO2@PDA@PEI composite fibers show the large number of amine groups, and the surface of the fibers can be positively charged in the acidic solution. Adsorption measurements show that the fibrous membrane samples exhibit excellent adsorption ability toward Cr(VI), and the maximum adsorption capacity is as high as 357.1 mg g−1 at solution pH value of 2, solution temperature of 25 °C. Specifically, about 72.1 % Cr(VI) can be directly reduced to harmless Cr(III) during the adsorption measurement, which is much higher than those of the almost adsorbents reported in literatures. The excellent adsorption/reduction ability endows the fibrous membranes with great potential application in removing highly hazardous Cr(VI) from wastewater.

A Mini Review on Arsenic and Cadmium Ion Detection Using Fluorescent-Colorimetric Sensors

Heavy metals with high atomic numbers, mass, and density are five times greater than water. They are naturally occurring elements and widely distributed in the environment due to their numerous applications like agricultural, industrial, domestic, technological, and medical fields increasing issues about their potential impact on the environment and human health. In this mini review, we focused on cadmium and arsenic metals. Cadmium is also the non-essential toxic heavy metal element found naturally in the earth's crust, and it is easily affected by plants’ movements through the food cycle and also causes harm to live beings. Arsenic is a common element found in low amounts in almost all environmental compartments. Chemosensors play a pivotal role in environmental and analytical chemistry. Chemosensors can detect enzymes, anions, and hazardous heavy metal ions with excellent selectivity and sensitivity at a low cost. Colorimetric chemosensors are instruments that convert chemical data into analytically relevant signals that can be viewed with the naked eye. Fluorescent-based chemosensors for cations, anions, and neutral analytes have been used in a wide range of applications.