A regenerable ion-imprinted magnetic biocomposite for selective adsorption and detection of Pb2+ in aqueous solution

Highly sensitive and highly selective lead ion electrochemical sensor based on zn/cu-btc-nh2 bimetallic MOFs with nano-reticulated reinforcing microstructure

Identifying ultra-trace amounts of divalent lead ions (Pb2+) with high response and selectivity, continues to be a pressing issue in identifying environmental pollutants and preventing health complications. This paper details how the in-situ electrodeposited Zn/Cu-BTC-NH2 metal-organic frameworks (MOFs) boosts Pb2+ concentration for amino adsorption and facilitates ion transfer between Cu element and Pb2+. The modified coating of the glassy carbon electrode (GCE) exhibits a unique nano-reticulated structure loaded with octahedron particles, the nano-reticulated structure ensures the structural strength of the modified electrode layer, while the loaded octahedral particles enhancing electrocatalytic activity. The ultra-trace detection of Pb2+ at concentrations below μg·L-1 is accomplished by using the square wave anodic stripping voltammetry (SWASV) method, the fabricated Zn/Cu-BTC-NH2 modified electrode signifies a detection threshold of 0.021 μg L-1 and a clearly ascending linear interval prior to the rise in Pb2+ concentration to 120 μg L-1. The reported electrochemical method for the precise identification of Pb2+ in water-based solutions offers a practical approach for modifying MOFs materials and detecting heavy metal ions.

A review of passive acid mine drainage treatment by PRB and LPB: From design, testing, to construction

An extensive volume of acid mine drainage (AMD) generated throughout the mining process has been widely regarded as one of the most catastrophic environmental problems. Surface water and groundwater impacted by pollution exhibit extreme low pH values and elevated sulfate and metal/metalloid concentrations, posing a serious threat to the production efficiency of enterprises, domestic water safety, and the ecological health of the basin. Over the recent years, a plethora of techniques has been developed to address the issue of AMD, encompassing nanofiltration membranes, lime neutralization, and carrier-microencapsulation. Nonetheless, these approaches often come with substantial financial implications and exhibit restricted long-term sustainability. Among the array of choices, the permeable reactive barrier (PRB) system emerges as a noteworthy passive remediation method for AMD. Distinguished by its modest construction expenses and enduring stability, this approach proves particularly well-suited for addressing the environmental challenges posed by abandoned mines. This study undertook a comprehensive evaluation of the PRB systems utilized in the remediation of AMD. Furthermore, it introduced the concept of low permeability barrier, derived from the realm of site-contaminated groundwater management. The strategies pertaining to the selection of materials, the physicochemical aspects influencing long-term efficacy, the intricacies of design and construction, as well as the challenges and prospects inherent in barrier technology, are elaborated upon in this discourse.

Highly sensitive detection of Pb2+ in the environment with DNAzyme and rolling circle amplification reaction

Lead (Pb2+) is a toxic heavy metal that can severely pollute the environment and cause harm to public health. Therefore, the prompt and accurate monitoring of lead levels in the environment is vital. In this study, a novel DNAzyme-based cascade signal amplification biosensor that could detect Pb2+ with high sensitivity was designed through the combination of the strand displacement reaction (SDR) and rolling circle amplification (RCA). When Pb2+ is absent, RCA is triggered under the synergistic action of T4 DNA ligase and phi29 DNA polymerase with an artificially fluorophore-labeled S-chains being released to replace the upstream products generated by repeated RCA, thereby restoring the quenched fluorescence and emitting a strong fluorescent signal. After adding Pb2+, 8-17 DNAzyme binds specifically to Pb2+ and catalyzes the cleavage of the rA site on a single-stranded DNA with artificially modified rA site to restrict the RCA. The designed sensor provides a linear detection range for Pb2+ from 25 pM to 1 µM, with a low limit of detection 8.3 pM. Significantly, this sensor still demonstrates satisfactory performance when used for detecting Pb2+ in environment samples (e.g., river water). We consider that our study can provide reference values and ideas for the development of heavy metal ion detection methods.

Preparation and application of the thermo-/pH-/ ion-sensitive semi-IPN hydrogel based on chitosan

Chitosan based hydrogels with multiple stimulus responses have broad application prospects in many fields. Considering the advantages of semi interpenetrating network (IPN) technology and the special temperature and ion responsiveness of polymers containing zwitterionic groups, a semi-IPN hydrogel was prepared through in situ free radical polymerization of N,N-dimethyl acrylamide and [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) ammonium hydroxide with polyethylene glycol dimethacrylate as a crosslinker and carboxymethyl chitosan as filler. The gel mass fraction and swelling ratio were measured, and the preparation conditions were optimized. The result indicated that the hydrogel possessed a unique thermo-/pH-/ ion-sensitive behavior. The swelling ratio increased with the increase of temperature and ion concentration, and showed a decreasing trend with the increase in pH. In addition, the hydrogel was stable when the stimuli changed. Adsorption behavior of the hydrogel to Eosin Y (EY) was systematically investigated. The adsorption process can be described well by the pseudo-second-order kinetic model and Langmuir isotherm model, indicating that it was a chemical adsorption. The experiments indicated that the hydrogel exhibited good antifouling and reusability features. Therefore, the semi-IPN hydrogel with antifouling properties and thermo-/pH-/ion-sensitivity can be easily manufactured is expected to find applications in water treatment fields.

Weathered Coal-Immobilized Microbial Materials as a Highly Efficient Adsorbent for the Removal of Lead

Most research on immobilized microorganisms employs biomass charcoal as a carrier, but limited studies explore coal-based resources for microbial immobilization. Herein, lead-resistant functional strains were immobilized using weathered coal as a carrier, resulting in the development of a weathered coal-immobilized microbial material (JK-BW) exhibiting high efficiency in lead removal from solutions. A quadratic polynomial model for the adsorption capacity and adsorption rate of JK-BW on Pb2+ was developed using the Box-Behnken method to determine the optimal adsorption conditions. The Pb2+ adsorption mechanism of JK-BW was studied through batch adsorption and desorption experiments along with SEM-EDS, BET, FT-IR, and XPS analyses. Findings indicated that optimal conditions were identified at 306 K temperature, 0.36 g/L adsorbent dosage, and 300 mg/L initial solution concentration, achieving a peak adsorption performance of 338.9 mg/g (308 K) for the immobilized material, surpassing free cell adsorption by 3.8 times. Even after four cycles of repeated use, the material maintained its high adsorption capacity. Pb2+ adsorption by JK-BW involved monolayer chemisorption with ion exchange, complexation, precipitation, physical adsorption, and microbial intracellular phagocytosis. Ion exchange accounted for 22-42% and complexation accounted for 39-57% of the total adsorption mechanisms, notably involving exchanges with K, Ca, Na, and Mg ions as well as complexation with -OH, -COOH, CO-OH, -COOH, CO-, NH2, and the β-ring of pyridine for Pb2+ adsorption.

Biomagnetic chitosan-ethylene glycol diglycidyl ether/organo-nanoclay nanocomposite for azo dye removal: A statistical modeling by response surface methodology

Herein, a quadruple biomagnetic nanocomposite of cross-linked chitosan-ethylene glycol diglycidyl ether/organo-nanoclay (MCH-EGDE/ORNC) was designed for the uptake of remazol brilliant blue R (RBBR) dye from aqueous environment. The adsorption process was systematically improved via the Box-Behnken design (BBD) to determine the influence of key uptake parameters, including MCH-EGDE/ORNC dosage, pH, and time, on the RBBR removal. The highest RBBR removal of 87.5 % was achieved at the following conditions: MCH-EGDE/ORNC dosage: 0.1 g/100 mL; pH: 4.0; contact time: 25 min. The findings of the kinetics and equilibrium studies revealed an excellent fit to the pseudo-second order and the Freundlich models, respectively. The adsorption capacity of the MCH-EGDE/ORNC for RBBR was found to be 168.4 mg/g, showcasing its remarkable adsorption capability. The present work highlights the potential of MCH-EGDE/ORNC biomaterial as an advanced adsorbent and lays the foundation for future applications in water purification and environmental remediation.

Field specific capture of Pb(II) in aqueous samples with three channels in-tip microextraction apparatus based on ion-imprinted polymer

On-site specific capture is a critical step in accurate analysis of trace Pb(II) in environmental waters. In this connection, a new Pb(II)-imprinted polymer-based adsorbent (LIPA) was in-situ prepared in pipette tip and used as the extraction medium of laboratory-made portable three channels in-tip microextraction apparatus (TIMA). Density function theory was employed to verify the selection of functional monomers for the preparation of LIPA. The physical and chemical properties of the prepared LIPA were inspected with various characterization techniques. Under the beneficial preparation parameters, the LIPA presented satisfactory specific recognition performance towards Pb(II). Selectivity coefficients of LIPA towards Pb(II)/Cu(II) and Pb(II)/Cd(II) were 6.82 and 3.27 times higher than that of non-imprinted polymer-based adsorbent, respectively, and the adsorption capacity towards Pb(II) was as high as 36.8 mg/g. Freundlich isotherm model fitted well with the adsorption data, revealing that the adsorption of Pb(II) on LIPA was a multilayer process. After optimizing the extraction conditions, the developed LIPA/TIMA was employed to field selectively separate and enrich trace Pb(II) in various environmental waters followed by quantification with atomic absorption spectrometry. The enhancement factor, linear range, limit of detection and RSDs for precision were 183, 0.50-10000 ng/L, 0.14 ng/L and 3.2-8.4%, respectively. Accuracy of the developed approach was inspected by means of spiked recovery and confirmation experiments. Achieved results reveal that the developed LIPA/TIMA technique is good for field selective separation and preconcentration of Pb(II) and the introduced approach can be used to measure ultra-trace Pb(II) in a variety of waters.

A portable microfluidic electrochemical sensing platform for rapid detection of hazardous metal Pb2+ based on thermocapillary convection using 3D Ag-rGO-f-Ni(OH)2/NF as a signal amplifying element

Heavy metal pollution is causing a great threat to ecological environment and public health, which needs an efficient strategy for monitoring. A portable microfluidic electrochemical sensing system was developed for the determination of heavy metal ions. Herein, the detection of Pb²⁺ was chosen as a model, and a microfluidic electrochemical sensing chip relying on a smartphone-based electrochemical workstation was proposed for rapid detection Pb²⁺ with the assistance of thermocapillary convection result from the formed temperature gradient. The 3D Ag-rGO-f-Ni(OH)₂/NF composites, prepared by one-step hydrothermal method without any Ni precursor salt, were used to further amplify electrochemical signals under the synergistic effect of thermocapillary convection. The thermocapillary convection could accelerate the preconcentration process and shorten the detection time (save 300 s of preconcentration time). The fabricated system exhibited the exceptional competence for monitoring of Pb²⁺ range from 0.01 μg/L to 2100 μg/L with a low detection limit (LOD) of 0.00464 μg/L. Furthermore, this portable system has been successfully demonstrated for detecting Pb²⁺ (0.01 μg/L to 2100 μg/L) in river water (LOD = 0.00498 μg/L), fish (LOD = 0.00566 μg/L) and human serum samples (LOD = 0.00836 μg/L), and the results were consistent with inductively coupled plasma-mass spectrometry (ICP-MS). The proposed novel sensing platform provides a cost-effectiveness, rapidly responding and ease-to-use pathway for analysis of heavy metal ions in real samples and shows great potential in point-of-care testing.

One-Step Pyrolysis Fabrication of Magnetic Bagasse Biochar Composites with Excellent Lead Adsorption Performance

In the present study, a magnetically separable adsorbent, manganese ferrite (MnFe₂O₄)/sugarcane bagasse biochar magnetic composites (MFSCBB-MCs), was fabricated through a one-step pyrolysis method. The characterization of the prepared adsorbents indicated that MnFe₂O₄ nanoparticles were successfully embedded into the biochar matrix, offering magnetic separability and increasing the negative charges on the surface relative to the pristine biochar. Batch adsorption tests indicated that the adsorption of lead on MFSCBB-MCs was pH- and dose-dependent. The experimental results were effectively fitted using the pseudo-second-order kinetic model (R ² > 0.99) and the Langmuir isotherm equation (R ² > 0.99), indicating the main chemisorption pathway and monolayer coverage process. Meanwhile, lead adsorption was found to be spontaneous and endothermic, as shown by the study of thermodynamic parameters. The maximum capacity, q _m, calculated from the Langmuir model was 155.21 mg·g^-1 at 25 °C, demonstrating excellent adsorption capability compared with several previously reported bagasse adsorbents. Based on adsorption mechanism analysis, physical adsorption, electrostatic attraction, and complexation were all involved in the lead(II) adsorption process on MFSCBB-MCs. Furthermore, the adsorbent was easily regenerated as indicated by the high magnetic separation and chemical desorption potential after five cycles, so it is a cost-effective and environmentally favorable adsorbent for wastewater lead removal.

Preparation, adsorption performance and mechanism of MgO-loaded biochar in wastewater treatment: A review

Biochar is a low cost, porous and solid material with an extremely high carbon content, various types of functional groups, a large specific surface area and many other desirable characteristics. Thus, it is often used as an adsorbent or a loading matrix. Nano-magnesium oxide is a crystalline material with small particles and strong ion exchangeability. However, due to the high surface chemical energy, it easily forms agglomerates of particles. Therefore, to combine the advantages of biochar and magnesium, metal magnesium nanoparticles can be loaded onto the surface of biochar with different modification techniques, resulting in biochars with low cost and high adsorption performance to be used as an adsorption matrix (collectively referred to as Mg@BC). This review presents the effects of different Mg@BC preparation methods and synthesis conditions and summarizes the removal capabilities and adsorption mechanisms of Mg@BC for different types of pollutants in water. In addition, the review proposes the prospects for the development of Mg@BC to solve various problems in the future.

A biomass-derived Schiff base material composited with polylactic acid nanofiber membrane as selective fluorescent 'turn off/on' platform for Pb2+ quantitative detection and characterization

Herein, a biomass-derived compound Z1 is synthesized via 'one pot' method for detection Pb²⁺ using fluorescence and visual dual-mode in aqueous solution. Z1 shows good response to Pb²⁺ with a limit of detection (LOD) of 13.4 nM. Importantly, the coordination mode of Z1 with Pb²⁺ is further evaluated by UV-vis and NMR spectroscopy and a 1:1 stoichiometry is identified. Furthermore, Z1 can be applied to detection Pb²⁺ in practical samples with satisfactory recoveries in range of 96.0 %-112.0 % in real samples. Besides, Z1 is added into polylactic acid (PLA) solution and made as portable fluorescence nanofiber membrane for Pb²⁺ detection. Further, Z1 responds to Pb²⁺ with high selectivity and sensitivity and has been applied for tracking Pb²⁺ changes in soil samples, zebrafish, and plant tissues. These results indicated that Z1 had great application potential in accurate detection Pb²⁺.

Sustainable and efficient technologies for removal and recovery of toxic and valuable metals from wastewater: Recent progress, challenges, and future perspectives

Due to their numerous effects on human health and the natural environment, water contamination with heavy metals and metalloids, caused by their extensive use in various technologies and industrial applications, continues to be a huge ecological issue that needs to be urgently tackled. Additionally, within the circular economy management framework, the recovery and recycling of metals-based waste as high value-added products (VAPs) is of great interest, owing to their high cost and the continuous depletion of their reserves and natural sources. This paper reviews the state-of-the-art technologies developed for the removal and recovery of metal pollutants from wastewater by providing an in-depth understanding of their remediation mechanisms, while analyzing and critically discussing the recent key advances regarding these treatment methods, their practical implementation and integration, as well as evaluating their advantages and remaining limitations. Herein, various treatment techniques are covered, including adsorption, reduction/oxidation, ion exchange, membrane separation technologies, solvents extraction, chemical precipitation/co-precipitation, coagulation-flocculation, flotation, and bioremediation. A particular emphasis is placed on full recovery of the captured metal pollutants in various reusable forms as metal-based VAPs, mainly as solid precipitates, which is a powerful tool that offers substantial enhancement of the remediation processes' sustainability and cost-effectiveness. At the end, we have identified some prospective research directions for future work on this topic, while presenting some recommendations that can promote sustainability and economic feasibility of the existing treatment technologies.