Concentrations Of Heavy Metal Ions Research Articles

Concentration of heavy metal ions from aqueous media under dynamic conditions using a composite sorbent based on chitosan and silica

Objectives. The study set out to investigate the sorption, toxicological, and regeneration properties of a composite sorbent based on chitosan hydrogel and unsuspended silicon dioxide (chitosan–colloidal silica), which manifest themselves under dynamic conditions of purification of aqueous solutions, as a means of removing heavy metal ions.Methods. The total dynamic exchange capacity of a chitosan–colloidal silica composite sorbent was evaluated under dynamic sorption conditions by passing solutions containing Zn(II), Cd(II), Cu(II), and Cr(III) ions having a concentration of 240–251 mg/L through a fixed sorption bed. The method for determining acute toxicity using daphnia (Daphnia magna Straus) is based on the direct calculation of the mortality of daphnia exposed to toxic substances contained in the test aqueous extract in comparison with a reference culture in samples that do not contain toxic substances. The regeneration ability of the sorbent was assessed by counting the number of sorption–desorption cycles using 0.1 M NaOH and 0.1 M NaHCO3 eluents, as well as aqueous solutions of H2O2 (1 and 3%).Results. The effectiveness of the chitosan–colloidal silica composite sorbent in the process of dynamic purification of aqueous media to remove Cu(II), Zn(II), Cd(II), and Cr(III) ions was established. After determining the times of ion breakthrough and saturation of the developed sorbent, its dynamic exchange capacity was calculated by processing the kinetic curves of sorption of heavy metal ions under dynamic conditions. The results of regeneration of the sorbent were presented in the context of the possibility of its reuse. It is shown that the sorbent can withstand up to five sorption–desorption cycles while maintaining a level copper cation extraction above 90%.Conclusions. Analysis of the kinetic curves demonstrated that the driving force behind the removal of heavy metals from aqueous media by means of the obtained sorbent is the external diffusion mass transfer of ions from the mobile phase of the solution. Biotesting of samples showed that the developed chitosan-based sorbent does not have acute toxicity.

Heavy Metals Immobilization of LDH@biochar-Containing Cementitious Materials: Effectiveness and Mechanisms

The utilization of tailings for producing solid waste-based concrete can effectively mitigate the environmental consequences stemming from tailings accumulation. However, the presence of high concentrations of heavy metal ions in certain tailings can deleteriously affect the microstructure of the cement matrix. This study investigated the in-situ immobilization performance of Pb2+ and Mn2+ by calcium-aluminum layered double hydroxides (CaAl-LDH) and LDH@biochar blended in cement-based materials. The equilibrium adsorption capacity of CaAl-LDH/LDH@biochar for heavy metals in aqueous solution was assessed by adsorption kinetics, while the effect of pH value on the removal rate of heavy metals was also studied. The workability and mechanical properties of cement mortar are significantly improved with the addition of 4% LDH@biochar. LDHs@biochar can effectively reduce the deteriorating effects of heavy metal ions on the fundamental properties of cement materials. Compared with CaAl-LDH, the leaching concentrations for Pb2+ and Mn2+ in LDH@biochar at 28 d is decreased by 59% and 39%, respectively. The stable adsorption of Pb2+ and Mn2+ by LDH@biochar is attributed to multiple mechanisms, including interlayer anion exchange effect, chemical adsorption of surface functional groups and electrostatic attraction. This study provide valuable insights for enhancing the efficiency of heavy metal immobilization in cement-based materials.

Magnetic heterogenization of supramolecular carbohydrates for the efficient adsorption of heavy metals removal from wastewater

BackgroundAs the high impact of heavy metals hazards for humans and the environment, providing a suitable method to remove heavy metals is of great importance. Recently, magnetic adsorbents have been developed for their ease of separation, high absorption efficiency, and cost-effectiveness has been expanding. On the other hand, hybridism adsorbents composed of a magnetic core and an organic branch amended with different functional groups such as –OH, –NH2, −SH, and –COOH have suitable potentials for heavy metal removals. MethodsIn this, a simple procedure for the preparation of β-cyclodextrin bonded Fe3O4@SiO2 (β-CD-SiO2@Fe3O4) was reported. The morphological, structural, and thermal stability characteristics were investigated by the XRD, SEM, EDS, FT-IR, and TGA-DTA techniques. Next, the potential of β-CD-SiO2@Fe3O4 in the absorption of Cd2+ and Pb2+ ions from wastewaters was investigated. The effect of various parameters such as pH, adsorbent dosage, Pb/Cd concentration, and the temperature was investigated on the absorption of Cd2+ and Pb2+ heavy metal ions. Significant findingsThe maximum adsorption was achieved when pH = 6.5, heavy metal ion concentration (250 mg/L), and adsorbent dosage (0.075 g) at room temperature was used. The adsorption process could be described by kinetic models and the pseudo-second-order model was well-matched. The maximum adsorption capacities of Pb2+ and Cd2+ were obtained at 160 and 159.33 mg/g respectively. The negative value of ΔG indicates the spontaneity of the absorption process. The negative values of ΔH and ΔS show the exothermic nature of the absorption reaction.

Mechanistic Coupling of Coagulation-Flocculation, and Machine Learning for Removal of Various Contaminants from Water System

Water is the most precious compound on the earth. Presence of different pollutants in water is a major cause of pollution. Numerous materials and technologies have been used to remove these pollutants from the water supply. Access to safe water for everyone is the prime aim of sustainable development goal six. To do this, numerous materials and technologies have been created. Coagulation-flocculation and adsorption are the prime steps for treatment of wastewater. Coagulation-flocculation is done in tandem to counter the stabilizing force present to disturb the suspended particles' impurities and toxic materials, so as to allow collision of particles and lead to growth of flocs. Acute and chronic illnesses in humans can result from heavy metal ion concentrations that are higher than advised. Adsorption is effectively applied techniques for removal of these heavy metals and rest of the materials present in water. Machine learning helps to analyze the contaminants in water to develop a suitable technique and materials for removal of contaminants from water. The aim of this paper is to couple the coagulation-flocculation, and machine learning techniques together for removal of all contaminants from the water system and explain the mechanism which helps to know the chemical interaction.

The migration process and temperature effect of aqueous solutions contaminated by heavy metal ions in unsaturated silty soils

Adsorption-desorption experiments of three heavy metal ions (i.e., lead, copper, cadmium) in silty soil were carried out at different temperatures, and the microscopic characteristics of silty soil loaded with the three heavy metal ions were analyzed. A one-dimensional soil column was used to discuss the influences of heavy metal ion types and concentrations on the soil moisture distribution and the migration level of different heavy metal ions, especially during the dynamic change process from an unsaturated state to a saturated state. Studies show that the adsorption of heavy metal ions onto silty soil is closely related to the mineral composition and functional groups in silty soil. In addition to physical adsorption, the adsorption of heavy metal ions is closely related to the hydrolysis reaction of mineral components such as kaolinite, calcite, dolomite, plagioclase and quartz. Under constant temperature, the types and concentrations of heavy metal ions play an important role in the moisture migration of unsaturated soil. In the presence of heavy metal ions, the penetration of lead ions is the greatest, followed by copper ions and then cadmium ions. The greater the ion concentration is, the stronger the penetration of heavy metal ions in silty soils.

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.

The effect of acid mine drainage on the properties of an all-solid waste paste backfill body based on oil shale residue

The complex environment of mine water is closely linked to the effect of the backfill body. The goal of this study was to establish a method with which to reduce carbon emissions from cementitious materials while addressing the large amount of unutilized solid waste, such as oil shale residue, which lies on the surface of the planet, and pollutes the environment. Oil shale residue, fly ash, slag and coal gangue were used to produce an oil shale residue-based all-solid waste paste backfill (OSGPB) to study the changes in strength and environmental impact with corrosion time under acid mine drainage conditions. The development of cracks was monitored using digital image correlation (DIC) technology. The corrosion mechanism of OSGPB was analysed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). This study revealed that in an acid mine drainage environment, the unconfined compressive strength (UCS) decreased by 38.58% and 15.66% after 24 d of wetdry cycling and complete immersion corrosion, respectively. A significant quantity of corrosive gypsum was produced in the OSGPB, which expanded the internal micropores and gradually formed cracks. This led to more severe internal structural damage during wetdry cycles. Changes in the UCS of the OSGPB over 60 d were predicted using established grey models. The leached concentrations of heavy metal ions met the groundwater quality standard (class III) after the OSGPB was completely immersed in acid mine drainage and subjected to wetdry corrosion cycles. OSGPB showed great potential as a green backfilling material for mines.

Efficient separation of Cd2+ and Pb2+ by Tetradesmus obliquus: Insights from cultivation conditions with competitive adsorption modeling

Microalgae serve as efficient biosorbents for the removal of heavy metals. This study investigates the adsorption and desorption behavior of Tetradesmus obliquus FACHB-14 (T. obliquus) under various culture conditions. Glucose cultivation enhances adsorption, with Pb2+ exhibiting higher capacity than Cd2+, reaching a maximum of 80.24 mg/g at an initial heavy metal ion concentration of 64 mg/L. Kinetic modeling favors the pseudo-second-order kinetics. The Langmuir model is more suitable for describing the adsorption process of Cd2+ in BG11 and Pb2+ in glucose, with maximum adsorption capacities of 6.48 mg/g and 86.29 mg/g, respectively. The Temkin model is more suitable for describing the adsorption process of Pb2+ in BG11 and Cd2+ in glucose. Competitive adsorption reduces the maximum capacity by 42.60 % for Cd2+ and 55.61 % for Pb2+. The Extended Freundlich model fits competitive behavior. Analysis reveals increased extracellular polymer secretion under glucose conditions, which aids adsorption. Na2EDTA achieves up to 97.37 % recovery of heavy metal ions. Overall, T. obliquus cultured with glucose shows promise for heavy metal removal, especially in mixed systems.

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.

Effects of Polyether Amine Canopy Structure on Heavy Metal Ions Adsorption of Magnetic Solvent-Free Nanofluids.

Three Fe3O4 magnetic solvent-free nanofluids with different amine-based coronal layer structures are synthesized and characterized by using magnetic Fe3O4 as the core, silane coupling agent as the corona, and polyether amines with different graft densities and chain lengths as the canopy. The concentration of heavy metal ions after adsorption is measured by atomic absorption spectrometry (AAS) to study the effect of Fe3O4 magnetic solvent-free nanofluids on the adsorption performance of the heavy metal ions lead (Pb(II)) and copper (Cu(II)) in water. The adsorption of Fe3O4 magnetic solvent-free nanofluid was explored by changing external condition factors such as adsorption contact time and pH. Additionally, the adsorption model is established. The magnetic solvent-free nanofluid is separated from water by applying an external magnetic field to the system, and desorption and cyclic adsorption tests are carried out. Based on the adsorption mechanism, the structure design of Fe3O4 magnetic solvent-free nanofluid was optimized to achieve optimal adsorption performance.

Development of MXene for removal of lead (Pb+) ions from wastewater

Abstract A new family of 2D materials with enhanced properties than graphene plays a crucial role in environmental remediation and sustainability. The concentration of heavy metal ions in wastewater is an emerging issue in the global scenario. Heavy metals such as lead, chromium, cadmium, etc. are natural carcinogens and adversely affect environmental species, which tend to have potential activities on the surface of the new families. Lead poisoning is a very raising issue in some parts of India and is a major effluent disposed of to the waterbodies from various industrial streams. The removal of the lead components is studied in this research using adsorption experimentation using MXene as the surface-active adsorbent. The possible mechanism for lead removal from wastewater is also discussed, as well as the effective regeneration and reusability of the adsorbent over long adsorption cycles. MXenes were applied after the confirmation using X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy and zeta-potential. The induced coupled plasma–optical emission spectroscopy confirms the lead remediation by over 96% in the first adsorption cycle, which was then reduced to over 92% in the second adsorption cycle. The lead contamination was under the permissible limits as per the water standards.

Heavy metal decontamination by ion exchange polymers for water purification: counterintuitive cation removal by an anion exchange polymer

Ion exchange polymers were used for mercury and lead ions removal in water. The heavy metal ion concentration was analyzed by two independent methods: inductively coupled plasma–optical emission spectroscopy (ICP-OES) and gravimetry. The studied cation exchange polymer (CEP) was sulfonated poly(ether ether ketone) (SPEEK), and the anion exchange polymer (AEP) was poly(sulfone trimethylammonium) chloride (PSU-TMA). The removal capacity was connected with the ion exchange capacity (IEC) equal to 1.6 meq/g for both polymers. The concentration ranges were 0.15–0.006 mM for Hg2+ and 10.8–1.0 mM for Pb2+. SPEEK achieved 100% removal efficiency for mercury and lead if the concentration was below the maximum sorption capacity (Qmax), which was about 210 mg/g for Pb2+ with SPEEK. For PSU-TMA, the surprising removal efficiency of 100% for Hg2+, which seemed incompatible with ion exchange, was related to the formation of very stable complex anions that can be sorbed by an AEP. Langmuir adsorption theory was applied for the thermodynamic description of lead removal by SPEEK. A second-order law was effective to describe the kinetics of the process.

Experimental study on environmental chemical effect and purification treatment of waste slurry in horizontal directional drilling

The waste slurry generated during Horizontal Directional Drilling (HDD) has detrimental effects on water sources, soil, and organisms. Existing studies lack quantitative analysis and assessment of the environmental hazards of waste slurry. The treatment of waste slurry is usually done by physical curing or chemical curing agents. The treatment effect of these treatments is unsatisfactory or not environmentally friendly enough. Research on the application of Microbially Induced Calcite Precipitation (MICP) in waste slurry purification can help provide innovative solutions. This study began by acquiring the basic properties, mineral composition, and particle size distribution of the waste slurry through experiments. The effects of different concentrations of waste slurry on soil chemical properties were compared, including the measurement of total dissolved solids (TDS), turbidity, and heavy metal ion concentrations of waste slurry supernatant. Additionally, the environmental impact of the waste slurry was assessed from an electrochemical, turbidity, and ionic composition perspectively. A combination formulation containing 2.8 wt% urease, 5 wt% urea, and 3.5 wt% calcium chloride was used to purify the waste slurry. The supernatant of the MICP treated waste slurry undergoes electrochemical testing to evaluate the effectiveness of MICP technology for slurry treatment. The findings indicate that both chemical additives and stratum contaminants significantly contribute to slurry pollution. When the waste slurry constitutes more than 40 wt% of the soil mass fraction, the electrical conductivity (EC) of the soil surpasses the threshold of 1000 μs/cm, and the pH level rises to approximately 9.5, rendering it unsuitable for plant growth. Moreover, the TDS, turbidity, and heavy metal ion concentrations in the waste slurry supernatant exceed the permissible environmental discharge limits. Notably, the concentration of arsenic (As) exceeds the national standard by 18 times, cadmium (Cd) by 20 times, and selenium (Se) by 208 times, posing a high risk of environmental pollution. However, the comparison of ion concentrations in the supernatant before and after MICP treatment reveals that MICP demonstrates effective cementation and co-precipitation of heavy metal ions. MICP purified 66.6 % of arsenic (As), all cadmium (Cd), 75 % of phosphorus (P), and 76 % of selenium (Se) from the waste slurry supernatant. The results of this research contribute to the quantitative evaluation of the environmental hazards of waste slurry. It also helps to promote the application of MICP in waste slurry purification.

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;.

Characterization, Efffects and Chemical Treatment of Heavy Metals in Produced Water from Injection Wells using Hydroxide Precipitation

Produced water obtained from five (5) water injection Wells in the Niger Delta area Nigeria were analysed for heavy metal ion concentrations using Themo Elemental Flame Atomic Absorption Spectrophotometer (AAS). Results obtained show that concentrations of lead (Pb2+), cadmium (Cd2+), chromium (Cr2+), nickel (Ni2+), cobalt (Co2+), vanadium (V2+), zinc (ZN2+), mercury (Hg+), silver (Ag+) and copper (Cu2) were above acceptable limits as specified by Environmental Guidelines and Standard for Petroleum Industries in Nigeria (EGASPIN). The concentrations of As2+, Fe2+, K+ and Mn2+ were within specification. Commingled produced water from the five water injection Wells were subjected to hydroxide precipitation using Ca(OH)2 at concentrations of 10, 20, 30, 40 and 50 ppm respectively. Results obtained show that all the heavy metal ions reduced within acceptable limit at 30 ppm chemical concentration. Heavy metal ions reduced with increase in chemical concentration with a corresponding increase in the pH of the solution which was however still within specification. The hydroxide converts the metal ions dissolved in solution into solid particles for easy sedimentation. Ca(OH)2 precipitates metal ions by changing the pH and electro-oxidizing potential of the solution. Properly treated produced water can be reinjected into the reservoir to enhance oil recovery, used in agriculture for irrigation purposes, discharged into the sea and other water bodies during offshore operations or even used in drilling services. Produced water discharged into the soil are non-biodegradable so must be adequately treated before discharge. Plants pick up heavy metals through their roots by the release of a variety of root exudates which changes the rhizosphere pH of the metal ion in solution thereby making them bioavailable for plant uptake by osmosis. Heavy metals in plants can exert a variety of toxic actions by damaging plant chloroplast thereby disturbing photosynthesis. Humans take in heavy metals into their system by consuming contaminated plants, water as well as inhaling contaminated air. Consumption, ingestion and inhalation of heavy metals by humans can cause a wide range of ailments such as cardiovascular diseases, kidney related problems, neurocognitive diseases, renal damage, heart disease, coronary artery disease, lung fibrosis, nasal cancer.

High-sensitivity detection of low-concentration heavy metal ions in solution by multiple reflection enhanced absorption (MREA) spectroscopy.

Heavy metal ions (Cr6+, Co2+, Ni2+, and Cu2+) in the electroplating and electrolysis industries are significantly related to process parameters and product quality, even at lower concentrations. Absorption spectroscopy is widely used for substance qualitative and quantitative analysis, which is an analytical method with the potential for real-time monitoring of heavy metal ions concentration in industrial processes. In this paper, a low-concentration heavy metal ion analysis method based on multiple reflection enhanced absorption (MREA) is proposed. Compared with traditional absorption, MREA has the advantages of low concentration detection limit and high-sensitivity. First, a reflective film (Al-SiO2) was prepared and a multiple reflection optical structure was designed to realize multiple parallel reflections of light in the solution medium. Then absorption spectra of low-concentration Cr6+, Co2+, Ni2+ and Cu2+ solutions were measured by MREA and traditional absorption methods. Finally, spectral bandwidth and incident light spots were optimized to obtain a superior absorption enhancement effect. The results showed that MREA could effectively increase the substance absorbance compared with traditional absorption. At the same time, with the optimal spectral bandwidth (0.4 nm) and incident light spot (1 mm), the detection limit of Cr6+, Co2+, Ni2+ and Cu2+ was reduced by 81.48%, 82.52%, 80.92% and 82.93%, respectively. The sensitivity was improved by 5-6 times, which was more obvious for low-concentration detection. In addition, the MREA method can achieve ion concentration analysis when Cr6+, Co2+, Ni2+, and Cu2+ coexist, and the linear correlative coefficients of the C-A curves were all greater than 0.999. Moreover, by adjusting reflectivity of the reflective film and the number of reflections in the optical structure, the results of the MREA method can be further optimized for the low-concentration heavy metal ion analysis. The MREA method has the advantages of simplicity, rapidity and versatility, which can provide the technical foundation for real-time monitoring method development of low-concentration heavy metal ions in industrial processes.

Modelling the Effect of mercury on the Growth Rate of an SDS-degrading Pseudomonas sp. strain Maninjau1

The SDS-degrading bacterium Pseudomonas sp. strain Maninjau1 experienced significant inhibition by mercury. Observations of bacterial growth at varying mercury concentrations revealed a sigmoidal pattern, with lag periods extending from 7 to 12 hours. Increasing mercury concentrations progressively impeded growth, with a concentration of 1.0 mg/L nearly halting bacterial activity. To analyze these effects, the modified Gompertz model was employed to determine growth rates across different mercury concentrations. These rates were then subjected to several models, including the modified Han-Levenspiel, Wang, Liu, Shukor, modified Andrews, and Amor models. Among these, the Amor model failed to appropriately fit the growth curves. Statistical analysis indicated that the Shukor model performed the best, evidenced by the lowest values for Root Mean Square Error (RMSE) and Akaike’s Information Criterion corrected (AICc), the highest adjusted correlation coefficient (adR2), and values of Accuracy Factor (AF) and Bias Factor (BF) closest to unity. The parameters obtained from the Shukor model, which are mmax (h-1) and Sm (mg L-1) and n which represent maximum growth rate, critical heavy metal ion concentration and empirical constant values were 0.187, 1.126 and 2.406, respectively. The Shukor model allows for the prediction of the critical heavy metals concentration which can completely inhibited bacterial growth. This robust modeling approach underscores the Shukor model's suitability for predicting the impact of mercury on the growth dynamics of Pseudomonas sp. strain Maninjau1 under toxic stress conditions.

Curcumin-based ratiometric electrochemical sensing interface for the detection of Cd2+ and Pb2+ in grain products

The conventional electrochemical detection in food samples often suffers from low stability and poor reproducibility. The construction of ratiometric sensor is regarded as an effective means to overcome the issues. Herein, poly-curcumin (p-CCM)-Multi walled carbon nanotubes (MWCNTs)-layered double hydroxides (LDHs) was constructed as a novel rationmetric sensing material for detection of Cd2+ and Pb2+ in grain samples. Under the synergistic effect of MWCNTs and the adsorption capacity of LDHs, the p-CCM/MWCNTs/LDHs can significantly enhance the electrochemical responses of heavy metals. In the differential pulse voltammetry test, the ratio of oxidation peak currents between heavy metal ions and curcumin was directly proportional to the concentration of heavy metal ions. This has formed the basis of a new ratiometric electrochemical sensor for the detection of the levels of Cd2+ and Pb2+ in grain products. Under optimal conditions, the limits of detection for Cd2+ and Pb2+ were found to be 0.61 μg mL−1 and 0.74 μg mL−1, respectively. It is worth mentioning that the method was additionally utilized to detect Cd2+ and Pb2+ in rice and flour samples. The satisfactory recovery outcomes in both samples demonstrated minimal interference of the food matrix with the obtained ratiometric sensor. In this work, a CCM-based ratiometric electrochemical sensor was presented, which could potentially replace the widely used ferrocene-based ratiometric electrochemical sensor, thereby enhancing the exploration of electrode materials for ratiometric electrochemical sensors.

The apple Ca2+/H+ exchanger MdCAX2L-2 functions positively in modulation of Ba2+ tolerance

Calcium is an essential element for plant growth and development, and it plays an important role in the responses of plants to abiotic stress. High concentrations of heavy metal ions in soil significantly affect the yield and quality of crops and pose human health threats when these ions accumulate in edible organs. The Ca2+/H+ exchanger (CAX) family is a class of transporters that mediate the transmembrane transport of both Ca2+ and metal ions, and they are widely involved in regulating plant growth and development and stress responses. Here, we cloned an AtCAX2 ortholog, MdCAX2L-2, from apple. It is constitutively expressed in various apple tissues and significantly induced by Ca2+ and Ba2+ treatments. The MdCAX2L-2 protein is located in the vacuolar membrane in both plant and yeast cells. Overexpression of MdCAX2L-2 enhanced the tolerance of the yeast mutant K667 to high concentrations of Ca2+ and Ba2+. In addition, the role of MdCAX2L-2 in modulating Ba2+ tolerance was identified using MdCAX2L-2-overexpressing transgenic Arabidopsis plants and apple calli. Comparison of growth phenotypes and stress-related physiological indexes under BaCl2 treatment indicated that MdCAX2L-2 could enhance the Ba2+ tolerance of plants by promoting Ba2+ compartmentalization into the vacuoles and eliminating excess ROS. Our results provide insights that will aid future studies examining the function of CAX proteins in regulating stress tolerance in fruit crops, as well as their underlying mechanisms.

Effects of biochar-derived dissolved organic matter on the gut microbiomes and metabolomics in earthworm Eisenia fetida

The ecological risks of biochar-derived dissolved organic matter (DOM) to soil invertebrates at different organismal levels remains limited. This study comprehensively explored the ecological risks of biochar-derived DOM on earthworm gut through assessments of enzyme activity response, histopathology, gut microbiomes, and metabolomics. Results demonstrated that DOM disturbed the digestive enzymes in earthworm, especially for 10% DOM300 groups. The integrated biomarker response v2 (IBRv2) indicated that the perturbation of earthworm digestive enzymes induced by DOM was both time-dependent and dose-dependent. Pathological observations revealed that 10% DOM300 damaged intestinal epithelium and digestive lumen of earthworms. The significant damage and injury to earthworms caused by DOM300 due to its higher concentrations of heavy metal ions and organic substrates (e.g., toluene, hexane, butanamide, and hexanamide) compared to DOM500 and DOM700. Analysis of 16S rRNA from the gut microbiota showed a significant decrease in genera (Verminephrobacter, Bacillus, and Microbacteriaceae) associated with inflammation, disease, and detoxification processes. Furthermore, 10% DOM300 caused the abnormality of metabolites, such as glutamate, fumaric acid, pyruvate, and citric acid, which were involved in energy metabolism, These findings contributed to improve our understanding of the toxic mechanism of biochar DOM from multiple perspectives.