Fabrication of Composite Beads Based on Calcium Alginate and Tetraethylenepentamine-Functionalized MIL-101 for Adsorption of Pb(II) from Aqueous Solutions

Insights into the newly synthesized bi- Mannich base for carbon steel corrosion inhibition in H2S and HCl solution

Adding corrosion inhibitors is considered to be a cost-effective way to inhibit metal corrosion. In this study, we report the synthesis of a bi-mannich base corrosion inhibitor (BMT) with an impressive inhibition efficiency on carbon steel in H2S and HCl co-existing solution. At the BMT concentration of 9 ppm, the inhibition efficiency (η) of 96.9%, 97.6% and 98.0% were determined by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy, respectively. The adsorption of BMT on the carbon steel surface follows the Langmuir adsorption isotherm, and the calculated free energy indicates that the adsorption is a spontaneous process. This research also delves into understanding the adsorption behavior and corrosion inhibition mechanism of BMT on carbon steel surfaces through quantum chemistry calculations. The results of this study provide guidance for the application of BMT as a corrosion inhibitor in sour and acid environments.

Heavy metal sequestration from wastewater by metal-organic frameworks: a state-of-the-art review of recent progress

Metal-organic frameworks (MOFs) have emerged as highly promising adsorbents for removing heavy metals from wastewater due to their tunable structures, high surface areas, and exceptional adsorption capacities. This review meticulously examines and summarizes recent advancements in producing and utilizing MOF-based adsorbents for sequestering heavy metal ions from water. It begins by outlining and contrasting commonly employed methods for synthesizing MOFs, such as solvothermal, microwave, electrochemical, ultrasonic, and mechanochemical. Rather than delving into the specifics of adsorption process parameters, the focus shifts to analyzing the adsorption capabilities and underlying mechanisms against critical metal(loid) ions like chromium, arsenic, lead, cadmium, and mercury under various environmental conditions. Additionally, this article discusses strategies to optimize MOF performance, scale-up production, and address environmental implications. The comprehensive review aims to enhance the understanding of MOF-based adsorption for heavy metal remediation and stimulate further research in this critical field. In brief, this review article presents a comprehensive overview of the contemporary information on MOFs as an effective adsorbent and the challenges being faced by these adsorbents for heavy metal mitigation (including stability, cost, environmental issues, and optimization), targeting to develop a vital reference for future MOF research.

Synthesis of Porous MgAl-LDH on a Micelle Template and Its Application for Efficient Treatment of Oilfield Wastewater

In this paper, a series of porous hierarchical Mg/Al layered double hydroxides (named as LDH, TTAC-MgAl-LDH, CTAC-MgAl-LDH, and OTAC-MgAl-LDH) was synthesized by a simple green hydrothermal method using wormlike micelles formed by salicylic acid and surfactants with different carbon chain lengths (0, 14, 16, and 18) as soft templates. BET, XRD, FTIR, TG, and SEM characterizations were carried out in order to investigate the structure and properties of the prepared materials. The results showed that the porous hierarchical CTAC-MgAl-LDH had a large specific surface area and multiple pore size distributions which could effectively increase the reaction area and allow better absorption capability. Benefiting from the unique architecture, CTAC-MgAl-LDH exhibited a large adsorption capacity for sulfonated lignite (231.70 mg/g) at 25 °C and a pH of 7, which outperformed the traditional LDH (86.05 mg/g), TTAC-MgAl-LDH (108.15 mg/g), and OTAC-MgAl-LDH (110.51 mg/g). The adsorption process of sulfonated lignite followed the pseudo-second-order kinetics model and conformed the Freundlich isotherm model with spontaneous heat absorption, which revealed that electrostatic adsorption and ion exchange were the main mechanisms of action for the adsorption. In addition, CTAC-MgAl-LDH showed a satisfactory long-time stability and its adsorption capacities were still as high as 198.64 mg/g after two adsorption cycles.

Constructing Highly Reliable and Adaptive Primary Explosive Composites for Micro-Initiator Assisting by a Hybrid Template of Metal-Organic Frameworks and Cross-Linked Polymers

Primary explosive, as a reliable initiator for secondary explosives, is the central component of micro-initiators for modern aerospace systems and military operations. However, they are typically prepared as powders, posing potential safety risks because of the inevitable particles scattering issues in the actual working environments. Here, the fabrication of a highly adaptive bulk material of copper azide (CA)-based safe primary explosive for micro-initiators is demonstrated. This bulk material, as derived by a complete azidation reaction of the carbonized metal-organic framework/cross-linked polymer hybrid template, enables the firm embedding of active CA species in a cross-linked carbon network (denoted as CA-C). Interestingly, this CA-C bulk material demonstrates multifarious mechanical stabilities (e.g., good shock and vibration resistance, and anti-overload capacity) in the simulated working conditions. Meanwhile, the CA contents in the CA-C bulk material reached as high as 70.3%, ensuring its detonation power. As a proof of concept, CA-C bulk material assembling in a micro-detonator can efficiently detonate the secondary explosive of CL-20 under laser irradiation. This work hereby advances the fabrication of safe and powerful primary explosives for the fulfillment of safe micro-initiator in a broad range of applications in aerospace systems.

Electrospinning Novel Sodium Alginate/MXene Nanofiber Membranes for Effective Adsorption of Methylene Blue

Understanding how to develop highly efficient and robust adsorbents for the removal of organic dyes in wastewater is crucial in the face of the rapid development of industrialization. Herein, d-Ti₃C₂T_x nanosheets (MXene) were combined with sodium alginate (SA), followed by electrospinning and successive Ca²⁺-mediated crosslinking, giving rise to a series of SA/MXene nanofiber membranes (NMs). The effects of the MXene content of the NMs on the adsorption performance for methylene blue (MB) were investigated systemically. Under the optimum MXene content of 0.74 wt.%, SA/MXene NMs possessed an MB adsorption capacity of 440 mg/g, which is much higher than SA/MXene beads with the same MXene content, pristine MXene, or electrospinning SA NMs. Furthermore, the optimum SA/MXene NMs showed excellent reusability. After the adsorbent was reused ten times, both the MB adsorption capacity and removal rate could remain at 95% of the levels found in the fresh samples, which indicates that the electrospinning technique has great potential for developing biomass-based adsorbents with high efficiency.

Efficient visual adsorption of Pb2+ by nanocellulose/sodium alginate microspheres with fluorescence sensitivity

In this study, carbon dots (CDs) were prepared by a one-pot hydrothermal method using tempo-oxidized cellulose nanocrystals (TOCNC) and polyethylenimine (PEI). The CDs were self-assembled with a microsphere adsorbent prepared using TOCNC and sodium alginate (SA). CDs-TOCNC/SA-an environmentally friendly, fluorescent-sensitive, and recyclable microsphere adsorbent-was obtained. FTIR analysis showed that PEI successfully modified the CDs. In addition, the fluorescence quenching of CDs was observed when the concentration of Pb²⁺ was 0.0001-100 mg/L, indicating that CDs can dynamically monitor Pb²⁺. CDs-TOCNC/SA can produce blue fluorescence under 365 nm UV light and selectively and efficiently adsorb Pb²⁺. When the concentration of Pb²⁺ was 0.0001-100 mg/L, fluorescence quenching of the adsorbent was observed, indicating that CDs-TOCNC/SA could visually adsorb Pb²⁺. The adsorption isotherm and kinetic parameters show that the adsorption process conforms to the Langmuir isotherm model at 298 K, and the maximum adsorption capacity of Pb²⁺ was 190.1 mg/g at pH = 5. Moreover, CDs-TOCNC/SA could still obtain 78.99 % Pb²⁺ after five sorption-desorption cycles. The adsorption mechanism may involve ion exchange, electrostatic attraction, intra-particle diffusion, and chemical complexation.

Enzymes-Encapsulated Defective Metal-Organic Framework Hydrogel Coupling with a Smartphone for a Portable Glucose Biosensor

Enzymes featuring high catalytic efficiency and selectivity have been widely used as the sensing element in analytical chemistry. However, the structural fragility and poor machinability of an enzyme significantly limit its practicability in biosensors. Herein, we develop a robust and sensitive hybrid biosensor by means of co-encapsulating enzymes into a defective metal-organic framework (MOF), followed by a double-crosslinked alginate gelatinization. The defective MOF encapsulation can enhance the stability of enzymes, yet well preserve their biocatalytic function, while the alginate gelatinization allows the MOF biohybrid high stretchability and mechanical strength, which facilitates the integration of a bead-, fiber-, and sheet-like portable biosensor. In this work, the enzymes consisting of glucose oxidase and peroxidase are co-encapsulated into this MOF hydrogel, and it can efficiently convert glucose into a blue-violet product through the biocatalytic cascade of encapsulated enzymes, enabling the colorimetric biosensing of glucose on a miniaturized MOF hydrogel when coupling with a smartphone. Interestingly, this MOF biohybrid hydrogel outputs a stronger sensing signal than the free biohybrid powders, attributed to the catalytic product-accumulated effect of the highly hydrophilic microenvironment of the hydrogel. As a result, this portable biosensor can sensitively and selectively sense glucose with a linear range from 0.05 to 4 mM. Importantly, both the hydrophilic hydrogel and MOF "armor" endow enzymes with high durability, and its sensing activity was well-maintained even after placing the biosensor at room temperature for 30 d. We believe that this MOF biohybrid hydrogel has huge potential for the engineering of next-generation portable biosensors.

Highlighting the Importance of Characterization Techniques Employed in Adsorption Using Metal-Organic Frameworks for Water Treatment

The accumulation of toxic heavy metal ions continues to be a global concern due to their adverse effects on the health of human beings and animals. Adsorption technology has always been a preferred method for the removal of these pollutants from wastewater due to its cost-effectiveness and simplicity. Hence, the development of highly efficient adsorbents as a result of the advent of novel materials with interesting structural properties remains to be the ultimate objective to improve the adsorption efficiencies of this method. As such, advanced materials such as metal-organic frameworks (MOFs) that are highly porous crystalline materials have been explored as potential adsorbents for capturing metal ions. However, due to their diverse structures and tuneable surface functionalities, there is a need to find efficient characterization techniques to study their atomic arrangements for a better understanding of their adsorption capabilities on heavy metal ions. Moreover, the existence of various species of heavy metal ions and their ability to form complexes have triggered the need to qualitatively and quantitatively determine their concentrations in the environment. Hence, it is crucial to employ techniques that can provide insight into the structural arrangements in MOF composites as well as their possible interactions with heavy metal ions, to achieve high removal efficiency and adsorption capacities. Thus, this work provides an extensive review and discussion of various techniques such as X-ray diffraction, Brunauer-Emmett-Teller theory, scanning electron microscopy and transmission electron microscopy coupled with energy dispersive spectroscopy, and X-ray photoelectron spectroscopy employed for the characterization of MOF composites before and after their interaction with toxic metal ions. The review further looks into the analytical methods (i.e., inductively coupled plasma mass spectroscopy, ultraviolet-visible spectroscopy, and atomic absorption spectroscopy) used for the quantification of heavy metal ions present in wastewater treatment.

Self-Stirring Microcatalysts: Large-Scale, High-Throughput, and Controllable Preparation and Application

Herein, we introduce a strategy to develop a kind of unprecedented microcatalyst, which owns self-stirring and catalytic performance based on pneumatic printing and magnetic field induction technology. A spindle-shaped microcatalyst based on metal-organic frameworks (MOFs) with a certain aspect ratio and size can be obtained by tuning the printing parameters and the intensity of the magnetic field. One nozzle can print 18 000 microcatalysts per hour, which provides a prerequisite for the realization of large-scale production in the industrial field. Furthermore, this strategy can be widely applied to a variety of other heterogeneous catalysts, such as mesoporous SiO₂, zeolite, metallic oxide, and so on. To demonstrate the superiority of the printed catalyst, the series of printed microcatalysts were evaluated by various catalytic reactions including liquid-phase hydrogenation, microdroplet dye-fading, and photocatalytic degradation in microreactor, all of which exhibited excellent catalytic performance.

Potential of biocompatible calcium-based metal-organic frameworks for the removal of endocrine-disrupting compounds in aqueous environments

Rapid urbanization, industrialization and population growth have accelerated the amount and variety of emerging contaminants being released into the aqueous environment, including endocrine-disrupting compounds (EDCs). The introduction of these compounds constitutes a threat to human health and the environment, even at trace levels. Hence, new water treatment technologies are urgently required to effectively remove EDCs from water. The currently available technologies used in water remediation processes are expensive and ineffective, and some produce harmful by-products. Calcium-based metal-organic frameworks (Ca-MOFs) are porous synthetic materials that can potentially be applied as adsorbents. These MOFs are hydrolytically stable, biocompatible and low-cost compared with conventional porous materials. The structure of Ca-MOFs is maintained even though calcium metal centers in the structure can easily coordinate with water. Ca-MOFs and their composite derivatives have the potential for use in water purification because these biocompatible adsorbents have been shown to selectively extract a significant quantity of contaminants. This review highlights the potential of Ca-MOFs to adsorb EDCs from aqueous environments and discusses adsorbent preparation methods, adsorption mechanisms, removal capacity, water stability and recyclability. This review will support future efforts in synthesizing new biocompatible MOFs as an environmental treatment technology that can effectively remove EDCs from water, thereby improving environmental and human health.

MIL series of metal organic frameworks (MOFs) as novel adsorbents for heavy metals in water: A review

With large specific surface area, abundant adsorption sites, flexible pore structure, and good water stability, Materials of Institute Lavoisier frameworks (MILs) have attracted increasing attention as effective environmental adsorbents. This review systematically analyzes and recapitulates recent progress in the synthesis and application of MIL-based adsorbents for the removal of aqueous heavy metal ions. Commonly used solvothermal, microwave, electrochemical, ultrasonic, and mechanochemical syntheses of MILs are first summarized and compared. Instead of focusing on adsorption process parameters, adsorption performances and governing mechanisms of virgin MILs, functional MILs, MIL-based composites, and carbonized MILs to representative metal(loid) ions (chromium, arsenic, lead, cadmium, and mercury) in water under various conditions are then systematically reviewed and discussed. In the end, this work also outlines prospects and future directions to promote the applications of MILs in treating heavy metal contaminated water.

In situ growth of ZIF-8 on carboxymethyl chitosan beads for improved adsorption of lead ion from aqueous solutions

In this study, a method for the in situ growth of zeolitic imidazolate framework-8 (ZIF-8) on carboxymethyl chitosan beads (BCMC) to produce a composite adsorbent (BCMC@ZIF-8) for the removal of Pb²⁺ from water is proposed. The results revealed that the utilization of the BCMC as a framework enhanced the stability of ZIF-8, and the presence of the latter in the composite improved the removal efficiency of Pb²⁺ from water. Data from X-ray photoelectron spectroscopy analysis and adsorption kinetics revealed that the adsorption mechanism included diffusion and the sharing/transfer of electrons between BCMC@ZIF-8 and Pb²⁺. The maximum adsorption capacity of BCMC@ZIF-8 fitted using the Langmuir model was 566.09 mg/g. Results of the experiments on the regeneration of the adsorbent and its stability in water further indicated that BCMC improved the stability of ZIF-8. This study demonstrated that the stability of metal-organic framework (MOF) materials, which exhibited high efficiencies for the removal of heavy metals in water can be improved through fixation of the polymer skeleton. Thus, the present study offers practical and theoretical guidance for the application of MOF materials in water treatment.

Efficient capture of ReO4- on magnetic amine-functionalized MIL-101(Cr): Revealing from selectivity to mechanism

The efficient decontamination of pertechnetate (⁹⁹TcO₄^-) is an essential task for managing radioactive ⁹⁹Tc in nuclear wastes. Perrhenate, (ReO₄^-), as a nonradioactive analog, exhibits almost identical physicochemical properties as ⁹⁹TcO₄^-. Herein, a novel magnetic amine-functionalized MIL-101(Cr) (NH₂-MIL-101(Cr)@Fe₃O₄) was prepared and used to efficiently remove ReO₄^- from solution for the facile magnetic separation. A series of environmental parameters were considered to investigate the adsorption performance of NH₂-MIL-101(Cr)@Fe₃O₄. Experimental results suggested that NH₂-MIL-101(Cr)@Fe₃O₄ has reached a satisfied adsorption capacity (~401 mg/g) and a very fast adsorption kinetics at pH 7.0. The selectivity for ReO₄^- was maintained even in the presence of interfering anions with relatively high concentrations. ReO₄^- were mainly captured by N-donor sites of the surface-decorated amine via complexation and were trapped in the cavities of modified MIL-101(Cr). NH₂-MIL-101(Cr)@Fe₃O₄ exhibits satisfactory adsorption performance for ReO₄^- and can be conveniently separated from wastewaters after adsorption.

Screening of Electrospray-operating Parameters in the Production of Alginate-Royal Jelly Microbeads Using Factorial Design

Introduction:

Royal jelly (RJ) has been consumed as food or as a supplement because of its high nutritional and medicinal values. A fresh harvested RJ is yellowish to whitish in color and contains proteins, free amino acids, lipids, vitamins, and sugar. Without proper storage conditions, such as at 4°C, the color of RJ changes to much darker yellow and produces a rancid smell. To prolong its shelf life, RJ is usually mixed with honey. Alginate, a natural and edible polymer derived from seaweed, is commonly used to encapsulate drugs and food due to its ability to form gels by reacting with divalent cations. However, there is a lack of research on the microencapsulation of RJ in alginate using electrospray. The electrospray technique has the advantage in producing consistent size and shape of alginate microbeads under optimum parameters.

Aim:

This research aimed to optimize electrospray-operating parameters in producing alginate–RJ microbeads.

Materials and Methods:

Optimization of alginate–RJ microbeads electrospray parameters was carried out using 2⁴ factorial design with three center points (19 runs). The studied parameters were flow rate, high voltage, nozzle size, and tip-to-collector distance, whereas the responses were particle size, particle size distribution, and sphericity factor. The responses of each run were analyzed using Design-Expert software.

Results:

Nozzle size is a significant parameter that influences the particle size. Flow rate is a significant parameter influencing the sphericity factor.

Conclusion:

Screening of the electrospray-operating parameters paves the way in determining the significant parameters and their design space to produce consistent alginate–RJ microbeads.

Amino-decorated magnetic metal-organic framework as a potential novel platform for selective removal of chromium (Vl), cadmium (II) and lead (II)

In this work, the -NH₂ functional group via 3-aminopropyltrimethoxysilane (APTMS) was selected to anchor onto the pore surface of magnetic metal organic framework using microwave green chemical process. The prepared nanocomposite was investigated for potential and fast removal of cationic Cd(II), Pb(II) as well as anionic Cr(VI) species via batch adsorption. Six kinetics models were applied in order to examine the adsorption mechanisms; the obtained data confirmed that the investigated metal ions followed the pseudo-second order model. The adsorption processes were fitted to the Langmuir model and the maximum adsorption capacities of cadmium (II), lead (II) and chromium (VI) ions were 693.0, 536.22 and 1092.22 mg g^-1. In addition, thermodynamic study confirmed the endothermic and spontaneous adsorption reactions. The nFe₃O₄@MIL-88A(Fe)/APTMS was easily regenerated and the adsorptive removal values were decreased by only 3% after five consecutive recycling processes. The recovery values from tap water, sea water and wastewater were identified as Cd(II) (98.49, 96.22 and 94.73), Pb(II) (96.88, 93.31 and 91.81) and Cr(VI) (99.69, 98.01 and 95.46), respectively.

Efficient Adsorption of Pb(II) from Aqueous Solutions by Metal Organic Framework (Zn-BDC) Coated Magnetic Montmorillonite

Composite adsorption materials combine the advantages of various adsorptive materials and compensate for the defects of single adsorbents. Magnetic montmorillonite (MMMT) shows good adsorption properties for Pb(II). In order to further improve the adsorption properties of MMMT, in this work, Zn-BDC, a kind of metal⁻organic framework (MOF), was modified onto the surface of MMMT by in situ polymerization. The composite material MMMT@Zn-BDC was characterized by Zetasizer, SEM, TEM, FTIR, XRD, VSM, and XPS. The influence of adsorption conditions on the adsorption capacity of MMMT@Zn-BDC for Pb(II) was examined, including the adsorbent dosage, pH of Pb(II) solution, initial concentration of Pb(II), and the temperature and adsorption time. Also, the adsorption mechanism was studied. The results of this study show that MMMT@Zn-BDC adsorbs Pb(II) via chemisorption. In addition, MMMT@Zn-BDC exhibits good potential for adsorbing Pb(II), including its high adsorption capacity (724.64 mg/g) and good recyclability.

Polymeric Composites with Embedded Nanocrystalline Cellulose for the Removal of Iron(II) from Contaminated Water

The exponential increase in heavy metal usage for industrial applications has led to the limited supply of clean water for human needs. Iron is one of the examples of heavy metals, which is responsible for an unpleasant taste of water and its discoloration, and is also associated with elevated health risks if it persists in drinking water for a prolonged period of time. The adsorption of a soluble form of iron (Fe2+) from water resources is generally accomplished in the presence of natural or synthetic polymers or nanoparticles, followed by their filtration from treated water. The self-assembly of these colloidal carriers into macroarchitectures can help in achieving the facile removal of metal-chelated materials from treated water and hence can reduce the cost and improve the efficiency of the water purification process. In this study, we aim to develop a facile one-pot strategy for the synthesis of polymeric composites with embedded nanocrystalline cellulose (NCC) for the chelation of iron(II) from contaminated water. The synthesis of the polymeric composites with embedded nanoparticles was achieved by the facile coating of ionic monomers on the surface of NCC, followed by their polymerization, crosslinking, and self-assembly in the form of three-dimensional architectures at room temperature. The composites prepared were analyzed for their physiochemical properties, antifouling properties, and for their iron(II)-chelation efficacies in vitro. The results indicate that the embedded-NCC polymeric composites have antifouling properties and exhibit superior iron(II)-chelation properties at both acidic and basic conditions.