Low Metal Ion Concentrations Research Articles

One‐pot hydrothermal biochar obtained from malt bagasse waste as an electrode‐modifying material towards the stripping voltammetric sensing of lead

AbstractPb2+ ions are highly toxic to living beings because they tend to bioaccumulate in the body. For this reason, the development of simpler, low‐cost, and easy‐to‐operate techniques that can detect and quantify low concentrations of metal ions would help to identify contaminating media and improve public health. This work proposes a Pb2+ voltammetric sensor based on a carbon paste electrode modified with hydrothermal biochar (hydrochar, HC) obtained from malt bagasse waste (HC/CPE). The obtained hydrochar was characterized by zero‐charge point, FT‐IR, XRD and thermogravimetry. The differential pulse adsorptive anodic stripping voltammetry (DPAdASV) technique was used to perform the Pb2+ determination. After optimizing important parameters for detecting Pb2+ ions and the parameters of the voltammetric technique employed, a linear response range of 0.50 to 7.06 μmol L−1 with a limit of detection (LOD) and limit of quantification (LOQ) of 55.0 and 181.5 nmol L−1 were achieved, respectively. The developed voltammetric procedure was applied towards the Pb2+ determination at tap water and river water samples, with excellent recoveries (ranging of 91.19 to 109.22 %), proving that the HC‐based electrode has great potential for detecting Pb2+ ions. Hydrothermal carbonization allowed the biomass to be converted into functionalized hydrochar, eliminating the need for subsequent functionalization/activation steps for use as a Pb2+ adsorbing material on the electrodic surface. The proposed sensor also proved to be easy to assemble and environmentally friendly by using biomass waste as the carbon material. Thus, the proposed sensor adds to the literature the possibility of simple and easy detection of metal ions with a waste reuse bias.

Synthesis and characterization of X (X = Ni or Fe) modified BaTiO3 for effective degradation of Reactive Red 120 dye under UV-A light and its biological activity

For the sustainable advancement of industrial expansion that is environmentally conscious, harmful dyes must be removed from wastewater. Untreated effluents containing colors have the potential to harm the ecosystem and pose major health risks to people, animals, and aquatic life. Here, we have fabricated Ni or Fe modified with BaTiO3 materials and effectively utilized them for Reactive Red 120 (RR 120) dye degradation under UV-A light. The synthesized materials were characterized, and their structural, and photo-physical properties were reported. Phase segregation was not present in the XRD pattern, as evidenced by the absence of secondary phase peaks linked to iron, nickel, or oxides. Low metal ion concentrations may be the cause of this, and the presence of those elements was confirmed by XPS measurements. The Raman spectra of the BaTiO3/Ni and BaTiO3/Fe samples show a widened peak at 500 cm−1, which suggests that Ni or Fe are efficiently loaded onto the BaTiO3. RR 120 dye photodegradation under UV light conditions was effectively catalyzed by BaTiO3/Fe, as evidenced by its superior performance in the UV irradiation technique over both BaTiO3 and BaTiO3/Ni. Compared to bare BaTiO3, both metal-modified materials efficiently degraded the RR 120 dye. Acidic pH facilitated the degradation process, which makes sense given that the heterogeneous photo-Fenton reaction was the mechanism of degradation along with BaTiO3 sensitization. High-acidity sewage can be dangerous and carcinogenic, and conventional biological treatment methods are not appropriate for managing it. In the current investigation, it may be used to treat color effluents with extremely low pH levels. Additionally, the ability of the produced nanocomposites to inhibit the growth of twenty pathogens was examined, along with two fungi, fifteen Gram-negative Bacilli (GNB), one Gram-positive Bacilli (GPB), and two Gram-positive Cocci (GBC).

Electrochemical sensing platform for detection of heavy metal ions without electrochemical signal.

Heavy metal pollution has attracted global attention because of its high toxicity, non-biodegradability, and carcinogenicity. Electrochemical sensors are extensively employed for the detection of low concentrations of heavy metal ions (HMIs). However, their applicability is often limited to the detection of ions that exhibit electrochemical signals exclusively in aqueous solutions. In this study, we proposed a multi-responsive detection platform based on the modification of horseradish peroxidase@zeolitic imidazolate frameworks-8/thionine/gold/ionic liquid-reduced graphene oxide (HRP@ZIF-8/THI/Au/IL-rGO). This platform demonstrated its capability to detect various metal ions, including those without conventional electrochemical signals. The Au/IL-rGO composite structure enhanced the specific surface area available for the reaction. Furthermore, the in situ growth of HRP@ZIF-8 not only shielded the THI signal prior to detection but also protected the electrode material. It was important to note that the introduced edetate disodium dihydrate (EDTA) had the ability to complex with various HMIs. When excess EDTA was present, it could cleave ZIF-8 and release HRP. In the presence of hydrogen peroxide (H2O2), HRP promoted the oxidation of THI previously reduced by the electrode and thus showed excellent sensitivity for HMIs detection. The proposed method overcame the limitation of traditional electrochemical sensors, which solely relied on electrochemical signals for detecting metal ions. This offers a novel approach to enhance electrochemical ion sensing detection.

Magnesium source with function of slowly releasing Mg and pH control for impurity-resistance synthesis ultra-large struvite from wastewater

Struvite (MgNH4PO4·6H2O, Magnesium ammonium phosphate, MAP), recovered from wastewater, has potential application as a slow-release fertilizer. However, crystal size distribution (CSD) of recovered MAP typically lied in the range of 50–300 μm, due to fast nucleation rate and notably narrow metastable zone width (MSZW) of MAP, with purity levels 40–90 %. In order to control the rate of nucleation, a novel magnesium source with the form of MgHPO4·3H2O wrapped with Mg(OH)2 was prepared, referred to as P-3. This compound gradually released Mg2+ and PO43−, regulating solution concentration kept in MSZW to promote crystal growth. The inherent Mg(OH)2 within P-3 also acted as a pH regulator in wastewater, eliminating the necessity for additional acid or alkali adjustments during crystallization process. The MAP precipitated by P-3 exhibited an impressive CSD of 5000–7000 μm, with a maximum size reaching 10,000 μm. This represented the largest CSD reported in literature for recovered MAP from wastewater. The significance of the ultra-large MAP precipitated by P-3 lied in its enhanced resistance to impurity adsorption, resulting in MAP with a remarkable purity 97 %, under conditions of low heavy metal ion concentration approximately 5 mg/L. Furthermore, the removal efficiency of ammonia nitrogen (NH4+) can reach 92 %. In comparison, two other magnesium sources, soluble salts (MgCl2 and Na2HPO4, P-1) and a combination of insoluble salts (Mg(OH)2 and MgHPO4, P-2) were evaluated alongside P-3. The CSD of MAP precipitated from P-1, P-2 was both <100 μm, with purity levels of 90 and 92 % and NH4+ removal efficiency of 92 and 90 %, respectively. Importantly, the strategy of obtaining ultra-large size MAP from wastewater in this study provided novel insights into the crystallization of other insoluble salts with large sizes.

Kinetic properties of glucose 6-phosphate dehydrogenase and inhibition effects of several metal ions on enzymatic activity in vitro and cells

Due to the non-degradable and persistent nature of metal ions in the environment, they are released into water bodies, where they accumulate in fish. In order to assess pollution in fish, the enzyme, glucose 6-phosphate dehydrogenase (G6PD), has been employed as a biomarker due to sensitivity to various ions. This study investigates the kinetic properties of the G6PD enzyme in yellow catfish (Pelteobagrus fulvidraco), and analyzes the effects of these metal ions on the G6PD enzyme activity in the ovarian cell line (CCO) of channel catfish (Ictalurus punctatus). IC50 values and inhibition types of G6PD were determined in the metal ions Cu2+, Al3+, Zn2+, and Cd2+. While, the inhibition types of Cu2+ and Al3+ were the competitive inhibition, Zn2+ and Cd2+ were the linear mixed noncompetitive and linear mixed competitive, respectively. In vitro experiments revealed an inverse correlation between G6PD activity and metal ion concentration, mRNA levels and enzyme activity of G6PD increased at the lower metal ion concentration and decreased at the higher concentration. Our findings suggest that metal ions pose a significant threat to G6PD activity even at low concentrations, potentially playing a crucial role in the toxicity mechanism of metal ion pollution. This information contributes to the development of a biomonitoring tool for assessing metal ion contamination in aquatic species.

Achieving Less Than 100 ppb Total Metal Ion Concentration in ESCAP Resins Synthesized by Atom Transfer Radical Polymerization

AbstractIn the photolithography process of integrated circuits （IC） manufacturing, it is desired that the photoresist resins have both smaller polydispersity index (PDI) and lower trace metal ion concentrations. The commercial environmentally stable chemical amplified photoresist (ESCAP) resins for 248 nm lithography are synthesized by free radical polymerization with PDI &gt;1.5. Although using atom transfer radical polymerization (ATRP) can result in lower PDI, the potential of high metal ion contamination is a major concern, as the reaction initiators usually are copper‐containing compounds. In this study, copolymer of p‐acetoxy styrene and tert‐butyl acrylate [poly(AOST‐co‐TBA)] is synthesized via ATRP achieving PDI as low as 1.25. It is then purified by ion exchange with two different resins, IRC747 and A15, which are effective at removing Cu and other metal ions. This reduces the total metal ion concentration in the copolymer powder to &lt;30 ppb with individual metal ion &lt;6 ppb. This is the first reported ATRP synthesized ESCAP resin having both low PDI and metal ion concentrations suitable for 248 nm photoresist application.

Peculiarities of Low Concentrations of Heavy Metal Ions' Effect on &amp;beta;-Carotene Content in Lymnaea stagnalis

The article deals with influence of heavy metal ions (cadmium, zinc, copper, lead, chromium, manganese and nickel) on &amp;beta;-carotene content in hemolymph, hepatopancreas, mantle and foot of &lt;i&gt;Lymnaea stagnalis&lt;/i&gt;. Its content dynamics was non-linear, owing to nature and specificity of the ions' effects, the exposure time and metabolic features of the organs and tissues. Over the two-day exposure, the impact Cr&lt;sup&gt;3&amp;#43;&lt;/sup&gt;, Mn&lt;sup&gt;2&amp;#43;&lt;/sup&gt;, Cu&lt;sup&gt;2&amp;#43;&lt;/sup&gt;, Ni&lt;sup&gt;2&amp;#43;&lt;/sup&gt; and Cd&lt;sup&gt;2&amp;#43;&lt;/sup&gt; ions resulted in increase of &amp;beta;-carotene content in the &lt;i&gt;L. stagnalis'&lt;/i&gt; hemolymph, indicating development of the immediate response to the toxic effects aimed at homeostasis. The Cr&lt;sup&gt;3&amp;#43;&lt;/sup&gt; impact caused its growth in hepatopancreas, mantle, and foot. The &amp;beta;-carotene content dynamics under the impact of all studied ions was organ-specific. Over the fourteen-day exposure, the suppressive effect of Mn&lt;sup&gt;2&amp;#43;&lt;/sup&gt;, Cu&lt;sup&gt;2&amp;#43;&lt;/sup&gt;, Ni&lt;sup&gt;2&amp;#43;&lt;/sup&gt;, Cd&lt;sup&gt;2&amp;#43;&lt;/sup&gt;, Cr&lt;sup&gt;3&amp;#43;&lt;/sup&gt; and Zn&lt;sup&gt;2&amp;#43;&lt;/sup&gt; on the &lt;i&gt;L. stagnalis&lt;/i&gt; metabolism increased, expressed in decrease of &amp;beta;-carotene content by 12.2-66.9&amp;#37;, except in hemolymph where under the impact of Cr&lt;sup&gt;3&amp;#43;&lt;/sup&gt; it increased 3.2 times, and in foot where under the impact of Ni&lt;sup&gt;2&amp;#43;&lt;/sup&gt; it remained at the control level. The hierarchical cluster analysis enabled to reveal regularities of HM ions impact on &amp;beta;-carotene content in hemolymph, hepatopancreas, mantle and foot of &lt;i&gt;L. stagnalis&lt;/i&gt;.

Facile fabrication of Co-doped cerium-manganese oxide for enhancing peroxymonosulfate activation to rapidly achieve simultaneous elimination of p-arsanilic and its oxidation by-product As(V)

Efficient purification of the wastewater containing organoarsenic by activated peroxymonosulfate (PMS) usually faces with a great challenge because the degradation of organoarsenic is coupled with the release of its byproduct As(V). Heterogeneous catalysts with catalytic and adsorption functions show great potential in activating PMS for the degradation of organoarsenic and the removal of secondary inorganic arsenic. In this study, Co-CeMnO was designed and fabricated to realize simultaneous elimination of p-arsanilic (p-ASA) and As(V) in Co-CeMnO (0.2 g/L)/PMS (0.25 mM) system, in which 50 µM p-ASA was almost completely degraded within 5 min and approximately 100% of the produced As(V) was removed within 30 min. The rate constant of the pseudo-first-order kinetics for the p-ASA degradation by PMS mediated with Co-CeMnO was high up to 0.65 min−1, approximately 6.5 times higher than that in the system of CeMnO/PMS. It was revealed that SO4•−, •OH and 1O2 acted as the main oxidant species responsible for the oxidation of organics and As(III), and the surface −OH of Co-CeMnO led to the adsorption of As(V) via ion exchange. The excellent reusability and stability of Co-CeMnO was verified by five cycles with high removal efficiencies of p-ASA (>92% within 10 min) and arsenic (>98% within 90 min) and low leached metal ion concentrations (Co ions < 0.27 mg/L; Mn ions < 0.15 mg/L; Ce ions ≈ 0). Under the condition of initial pH 5, p-ASA was degraded completely and over 98% of total arsenic was adsorbed in different water matrices, indicating the practical application potential of Co-CeMnO/PMS system. Thus, the present study provided a reliable PMS activation strategy by constructing bifunctional catalysts to achieve satisfactory treatment of the wastewater containing p-ASA.

Determination of iron in water by flame atomic absorption spectrometry with sorption preconcentration

Determination and monitoring of pollutants in the natural environment is an urgent task because of their impact on living organisms as a result of numerous anthropogenic impacts. For this reason, a large number of publications are devoted to the development, modification or optimization of analytical methods that can solve these problems. When determining trace elements present in various samples, such as natural and waste water, biological samples and alloy samples, direct determination by various instrumental methods is often impossible due to the matrix effect and rather low concentration of metal ions in the sample. The atomic absorption method is one of the methods widely used for the determination of iron ions, which has such advantages as simplified sample preparation, low probability of contamination and loss of elements, increased analytical productivity, the detection limit of components in the analyzed mixture reduced by several orders of magnitude, and the ability to determine trace amounts of elements in small samples. The aim of the study was to develop a technique for the preliminary concentration of Fe (III) ions in waters of various origins using a sorbent immobilized with sulfosalicylic acid and their further determination by flame atomic absorption spectrometry. Sorbents obtained on the basis of polyacrylonitrile modified with polyethylene polyamine (PPF-1 and PPA-1) with sulfosalicylic acid immobilized on their surface were used for selective sorption of Fe (III) ions. Optimal conditions for the immobilization of sulfosalicylic acid on sorbents and the formation of complexes with Fe (III) ions were studied. The developed sorption-atomic absorption technique provided determination of low concentrations of Fe (III) ions in various waters. The use of PPF-1 as a sorbent with immobilized sulfosalicylic acid for pre-concentration of iron has a number of advantages compared to traditional atomic absorption procedure, i.e., the simplicity, high degree of iron extraction, high sensitivity and selectivity of iron determination, as well as a low cost. The detection limit of iron ions is 0.01 μg/L, Sr does not exceed 0.033.

Validation and calibration of a novel GEM biosensor for specific detection of Cd2+, Zn2+, and Pb2+

BackgroundIn this study, we designed a novel genetic circuit sensitive to Cd2+, Zn2+ and Pb2+ by mimicking the CadA/CadR operon system mediated heavy metal homeostasis mechanism of Pseudomonas aeruginosa. The regular DNA motifs on natural operon were reconfigured and coupled with the enhanced Green Fluorescent Protein (eGFP) reporter to develop a novel basic NOT type logic gate CadA/CadR-eGFP to respond metal ions mentioned above. A Genetically Engineered Microbial (GEM)-based biosensor (E.coli-BL21:pJET1.2-CadA/CadR-eGFP) was developed by cloning the chemically synthesised CadA/CadR-eGFP gene circuit into pJET1.2-plasmid and transforming into Escherichia coli (E. coli)-BL21 bacterial cells.ResultsThe GEM-based biosensor cells indicated the reporter gene expression in the presence of Cd2+, Zn2+ and Pb2+ either singly or in combination. Further, the same biosensor cells calibrated for fluorescent intensity against heavy metal concentration generated linear graphs for Cd2+, Zn2+ and Pb2+ with the R2 values of 0.9809, 0.9761 and 0.9758, respectively as compared to non-specific metals, Fe3+ (0.0373), AsO43− (0.3825) and Ni2+ (0.8498) making our biosensor suitable for the detection of low concentration of the former metal ions in the range of 1–6 ppb. Furthermore, the GEM based biosensor cells were growing naturally within the concentration range of heavy metals, at 37 °C and optimum pH = 7.0 in the medium, resembling the characteristics of wildtype E.coli.ConclusionFinally, the novel GEM based biosensor cells developed in this study can be applied for detection of targeted heavy metals in low concentration ranges (1–6 ppb) at normal bacterial physiological conditions.

The Cr(III) Exchange Mechanism of Macroporous Resins: The Effect of Functionality and Chemical Matrix, and the Statistical Verification of Ion Exchange Data

This study focuses on investigating and comparing the influence of the surface functional groups and chemical matrices of macroporous resin on the Cr(III) exchange mechanism. The results discussed herein indicate that sulfonic resin removed Cr(III) ions with faster kinetics than carboxylic resin. Equilibrium was established within 15 and 7 min for the carboxylic and sulfonic resins, respectively, with a 99.5% removal efficiency at 333 K. The Langmuir exchange capacity was observed to be higher for the sulfonic resin (1.5 mmol∙g−1) than the carboxylic resin (0.80 mmol∙g−1) at 333 K. The adsorption isotherms obtained for the carboxylic and sulfonic resins were H and S types, respectively, representing a higher affinity of the carboxylic resin for Cr(III) removal at a low metal ion concentration. Additionally, it was noted that the carboxylic resin preferentially co-sorbed H+ and Cr(OH)2+ ions below Cr(III) concentrations of 6–8 mmol.L−1. The H+ ions co-sorption was almost negligible, whereas the Cr(III) exchange was 87 and 34.5% for the carboxylic acid resin and sulfonic acid resins, respectively. The data of the concentration studies were evaluated using non-linear forms of Freundlich, Langmuir, and Dubinin–Radushkevich adsorption isotherm models, and the kinetic data were analyzed using pseudo-Ist- and pseudo-IIst-order kinetic models. The activation energy Ea for Amberlite IRC-50 (Na+) was greater (22.4 kJ∙mol−1) than that of Amberlyst-15 (Na+) 17 kJ∙mol−1, indicating a higher energy barrier for the ion exchange reaction on carboxylic resin. As per the findings of a statistical error analysis (RMSE and SSE) and absolute average relative distribution (AARD) statistical model, a close agreement between the experimental and theoretical values suggested that the Langmuir isotherm was well-fitted to the current adsorptive investigations. The interaction of the COO− and SO3− functional sites of the resins for the exchange of Cr(III) ions was validated through an FT-IR analysis. The macroporous resins used in the current study for Cr(III) exchange showed promising performances compared to other resins. The current investigations revealed valuable insights for choosing macroporous resins as adsorbents in water filtration systems.

Metal Binding of Alzheimer's Amyloid-β and Its Effect on Peptide Self-Assembly.

ConspectusMetal ions have been identified as key factors modulating the aggregation of amyloid-β peptide (Aβ) implicated in Alzheimer's disease (AD). The presence of elevated levels of metal ions in the amyloid plaques in AD patients supports the notion that the dysfunction of metal homeostasis is connected to the development of AD pathology. Here, recent findings from high- and low-resolution biophysical techniques are put into perspective, providing detailed insights into the molecular structures and dynamics of metal-bound Aβ complexes and the effect of metal ions on the Aβ aggregation process. In particular, the development of theoretical kinetic models deducing different microscopic nucleation events from the macroscopic aggregation behavior has enabled deciphering of the effect of metal ions on specific nucleation processes. In addition to these macroscopic measurements of bulk aggregation to quantify microscopic rates, recent NMR studies have revealed details about the structures and dynamics of metal-Aβ complexes, thereby linking structural events to bulk aggregation. Interestingly, transition-metal ions, such as copper, zinc, and silver ions, form a compact complex with the N-terminal part of monomeric Aβ, respectively, where the metal-bound "folded" state is in dynamic equilibrium with an "unfolded" state. The rates and thermodynamic features of these exchange dynamics have been determined by using NMR relaxation dispersion experiments. Additionally, the application of specifically tailored paramagnetic NMR experiments on the Cu(II)-Aβ complex has been fruitful in obtaining structural constraints within the blind sphere of conventional NMR experiments. This enables the determination of molecular structures of the "folded" Cu(II)-coordinated N-terminal region of Aβ. Furthermore, the discussed transition-metal ions modulate Aβ self-assembly in a concentration-dependent manner, where low metal ion concentrations inhibit Aβ fibril formation, while at high metal ion concentrations other processes occur, resulting in amorphous aggregate formation. Remarkably, the metal-Aβ interaction predominately reduces one specific nucleation step, the fibril-end elongation, whereas primary and surface-catalyzed secondary nucleation mechanisms are less affected. Specific inhibition of fibril-end elongation theoretically predicts an enhanced generation of Aβ oligomers, which is an interesting contribution to understanding metal-Aβ-associated neurotoxic effects. Taken together, the metal binding process creates a metal-bound Aβ complex, which is seemingly inert to aggregation. This process hence efficiently reduces the aggregation-prone peptide pool, which on the macroscopic level is reflected as slower aggregation kinetics. Thus, the specific binding of metals to the Aβ monomer can be linked to the macroscopic inhibitory effect on Aβ bulk aggregation, providing a molecular understanding of the Aβ aggregation mechanism in the presence of metal ions, where the metal ion can be seen as a minimalist agent against Aβ self-assembly. These insights can help to target Aβ aggregation in vivo, where metal ions are key factors modulating the Aβ self-assembly and Aβ-associated neurotoxicity.

PH-dependent Synthesis and Interactions of Fluorescent L-Histidine Capped Copper Nanoclusters with Metal Ions.

In this work, L-Histidine-protected copper nanoclusters synthesized by changing the pH levels of precursor solution have been shown to display different emission wavelengths and intensities. As determined by mass spectrometry, nanoclusters Cu3L2 synthesized at acidic pH have 3 atoms in their core and emit in the greenish-yellow region, and nanoclusters Cu2L2, synthesized in the basic conditions have 2 atoms in their core and emit in the blue-green region. They are expected to have coordination through the carboxylate group and nitrogen of the imidazole ring of histidine ligand, respectively. Metal ions Mg2+, Mn2+, Zn2+, and Pb2+ selectively enhance the interaction between carboxylate - copper metal core and increase the emission intensity of Cu3L2. These metal ions weaken the interaction between imidazole nitrogen and copper metal core and quench the emission intensity of Cu2L2. As synthesized, nanoclusters exhibit good water solubility and photostability, they can act as fluorescent probes to sense the metal ions, therefore, they were utilized for the optical sensing of the mentioned metal ions. Fluorescent nanoclusters were found to sense even a very low concentration of metal ions with a limit of detection (3 σ/slope) in nanomolar range.

Green and cost-efficient functionalized clay adsorbent enables one-step ultraefficient removal of Pb(II) at very low and high concentrations

It is always a huge challenge to purify wastewater containing very low or high concentrations of heavy metal ions to drinking water level (World Health Organization (WHO) guidelines) by one-step static or dynamic adsorption with a highly efficient, cost-effective, and environmentally friendly adsorbent. In response to this challenge, a green, low cost and powerful porous silicate/Fe3O4 adsorbent (named MCSiMg49) with ultra-strong purification ability towards the Pb(II) in both low- and high-concentration wastewater was developed using natural abundant, safe, and nontoxic palygorskite-rich clay as the starting material and water as the only solvent. The adsorbent possesses a high specific surface area of 332.41 m2/g (2.81 times that of raw clay), and was proven to be the best one to date that can purify deeply Pb(II) in water. The adsorption capacity of the adsorbent towards Pb(II) reached 499.3 mg/g, and 99.8% of Pb(II) can be removed from 800 mg/L Pb(II) solution after adsorption with 3 g/L of the adsorbent, which is significantly superior to other adsorbents and commercial activated carbon (AC). The adsorption column packed with MCSiMg49 (1 g, upper layer) and clay (1 g, lower layer) can remove completely Pb(II) from natural water (e.g., Yangtze River water or Yellow River water) (concentration: 50 mg/L), and 3000 mL clean drinking water (WHO guidelines) was obtained by a one-step filtration process. The MCSiMg49 adsorbent is easy to use in both dynamic and static adsorption, because it can be quickly recycled from the solution by external magnetic field after use. The adsorption of Pb(II) on the adsorbent was mainly driven by the cooperation of electrostatic attraction, ion exchange, chemical complexation and in situ mineralization of Pb(II).

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.

A biomimetic porous fibre bundle adsorbent for the rapid and complete removal of multiple low-level heavy metal ions

Improving diffusion and mass transfer kinetics to enhance the synchronous removal efficiency of adsorbents for low concentrations of various heavy metal ions is of great significance for reducing heavy metal removal. Here, a biomimetic porous fibre bundle adsorbent with multiple adsorption sites was constructed by embedding and bonding porous coconut shell biochar on amino and sulfhydryl group-functionalized cellulose nanofibre bundles in the process of fibrogenesis, which was inspired by the principle of spider silk. The high porosity, specific surface area (212.17 m2/g) and swelling rate (184 %) of the porous fibre bundle could effectively improve the diffusion and mass transfer kinetics. Multiple adsorption sites of amino, carboxyl, and sulfhydryl groups endow the adsorbent with a synchronous removal rate for various heavy metal ions in water. Therefore, the porous fibre bundle could remove low concentrations of Pb(II), Cu(II), Cd(II) and Cr(VI) to safe drinking water level standard concentrations (US EPA) within 20 min. This study provided a simple method for designing an effective adsorbent for lowering heavy metal removal.

Hydrochemistry of an ancient traditional irrigation reservoir in Padaviya, Sri Lanka

Padaviya Wewa Reservoir constructed in 2nd century BC is an important traditional reservoir in Sri Lanka. The construction and the use of these traditional Sri Lankan reservoirs are different from modern large-scale hydroelectric and multi-purpose reservoirs in Sri Lanka and the rest of the world. The hydrochemistry of these unique water bodies has been rarely studied and understood. In this study, depth-wise distribution of Fe, Mn, Zn, Cd, and As and their correlation with pH, dissolved oxygen, conductivity, temperature, BOD, COD, and total phosphate were investigated to identify the mechanisms that drive the water quality in Padaviya Wewa Reservoir. There is a well distinguishable chemical gradient from the surface to the bottom of the water column suggesting that Padaviya is not a well-mixed water body even though the maximum water depth during the study period was 4.75 m. There was a strong negative correlation between Fe, Mn, Zn, and Cd and DO in both surface and bottom waters. In addition, a strong positive correlation between Fe, Mn, Zn, Cd, and As, and total phosphate was observed in bottom waters. The suggested driving force behind the depth-wise distribution of chemical species is intense biological activities in the reservoir. The weak thermal stratification is strengthened by photosynthesis at the surface waters and organic matter degradation at bottom of the reservoir. The end-result of these biological activities are oxygen rich surface waters with low concentrations of nutrients and metal ions and oxygen depleted bottom waters with higher concentrations of nutrients and metal ions.

Effects of heavy metal ions Cu2+/Pb2+/Zn2+ on kinetic rate constants of struvite crystallization

Struvite (MAP) crystallization technology is widely used to treat ammonia nitrogen in waste effluents of its simple operation and good removal efficiency. However, the presence of heavy metal ions in the waste effluents causes problems such as slow crystallization rate and small crystal size, limiting the recovery rate and economic value of the MAP. The present study was conducted to investigate the effects of concentrations of three heavy metal ions (Cu2+, Zn2+, and Pb2+) on the crystal morphology, crystal size, average growth rate, and crystallization kinetics of MAP. A relationship was established between the kinetic rate constant Kt calculated by the chemical gradient model and the concentrations of heavy metal ions. The results showed that low concentrations of heavy metal ions in the solution created pits on the MAP surface, and high level of heavy metal ions generated flocs on the MAP surface, which were composed of metal hydroxides, thus inhibiting crystal growth. The crystal size, average growth rate, MAP crystallization rate, and kinetic rate constant Kt decreased with the increase in heavy metal ion concentration. Moreover, the Kt demonstrated a linear relationship with the heavy metal concentration ln(C/C*), which provided a reference for the optimization of the MAP crystallization process in the presence of heavy metal ions.

Investigation of the corrosion of stainless steel, copper and aluminium in sunflower biodiesel solution: Experimental and theoretical approaches

The increase in energy has created a clear imbalance between the availability and usage of these resources, prompting the industry to resort to biofuels. The main objective of this study is to investigate the corrosion resistance of materials used as biofuel production reactors (stainless steel (SS), aluminium (Al), and copper (Cu)) during sunflower biodiesel production. The corrosion resistance of stainless steel, aluminium, and copper was investigated using electrochemical monitoring techniques such as open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS). Throughout this work, spectroscopic methods, including Fourier transform infrared (FTIR), GS/MS, UV absorption, SEM/EDS, and X-ray diffraction (XRD), have been used to thoroughly examine the surfaces of the metals and the composition of the biodiesel after testing. All metals examined showed excellent corrosion resistance, attributed to the formation of such a passivation film on their surfaces, as shown by the EIS data. SEM/EDS analysis confirmed that the methyl esters had a slight impact on metal deterioration, with a modest corrosion rate and the formation of localized micro-pitting on the metal surface. The FAAS analysis also revealed the existence of a low concentration of metal ions released into the solution. Therefore, the correlation approach (DFT and molecular dynamics simulations (MDS)) was applied to support the experimental results that favoured aluminium as the base metal for biodiesel synthesis due to its low corrosion rate during the process.

Influence of pollutant concentration on the separation efficiency of chelating membranes for removing simultaneously metal ions and proteins from simulated industrial wastewater

AbstractBACKGROUNDA novel chelating membrane was fabricated for removing simultaneously metal ions (Cd2+, Pb2+ and Cu2+) and proteins (bovine serum albumin and lysozyme) from simulated industrial effluent. The purpose of the study was to investigate the influence of pollutant concentration on the separation efficiency of the chelating membrane for pollutants.RESULTS(i) The removal of metal ions mainly relies on the adsorption capacity of the chelating membrane, and seems to be independent of the concentration of protein. (ii) The retention of proteins depends mainly on their concentration in solution. (iii) When the wastewater contains high concentration of metal ions (C = 100 mg L−1) and low concentration of proteins (C = 10 mg L−1), the chelating membrane exhibits overall poor separation performance, with a low ion removal efficiency (55–70%) and a low protein rejection rate (ca 60%). (iv) When the wastewater contains low concentration of metal ions (C = 10 mg L−1) and high concentration of proteins (C = 100 mg L−1), the chelating membrane exhibits overall excellent separation performance, with ion removal rates of higher than 90% (except for Cd2+) and protein rejection rates of higher than 90%.CONCLUSIONSThe separation efficiency of the chelating membrane for metallic and organic pollutants greatly depends on the pollutant concentration in the wastewater. This study provides a theoretical basis for membrane technology for removing simultaneously heavy metals and organic pollutants in wastewater. © 2022 Society of Chemical Industry (SCI).