Removal of lead ions from wastewater using magnesium sulfide nanoparticles caged alginate microbeads

Alginate-based materials as adsorbent for sustainable water treatment

With the encroaching issue of water pollution, the use of involved chemicals to remove pollutants from water is not only a risk of chemical contamination, a potential hazard to the environment and human health but also requires significant investment in managing and improving the chemicals. Therefore, alginate as one of the nanomaterial-adorned polysaccharides-based entity that usually extract from brown algae has been used as novel and more efficient catalysts in the removal of a variety of aqueous pollutants from wastewater, including ionic metals and organic/inorganic pollutants by using the adsorption techniques. Adsorption is a technique used in water treatment where non-polar or particles less soluble in water are stuck to the surface of the adsorbent and therefore purifying it. An example of pollutant typically removed via this method is an organic dye. Alginate-based composites due to their ability to bind to metals like Cd, Au, Cu, Fe, Ni, Pb, and Zn, are a common low-cost and highly effective adsorbents used to remove heavy metals, industrial paints, pesticides, and antibiotics. This review focusses on augmenting the recent status, challenges, and further prospects in alginate-based materials for their potential role exclusively in wastewater treatment, including their modification as adsorbents and their adsorption behaviors. Various applications of alginate-based adsorbent are showcased and tabulated their role in treatment of diverse range of pollutants. It can be concluded that the role of alginate in wastewater treatment is indispensable in the future with its biodegradability, low cost, stability, and high-water permeability properties. However, some challenges need to be identified and overcome to ensure the application of alginate in wastewater treatment can be widely used throughout the world, especially in Malaysia, a country with an abundance of water.

Development of nanoscale zero-valent iron embedded on polyaniline reinforced with sodium alginate hydrogel microbeads for effective adsorption of arsenic from apatite soil leachate water

A novel polymeric nanocomposite hydrogel adsorbent was developed to enhance the efficiency of arsenic removal from apatite soil leachate. Apatite soil aqueous leachate was treated with nanoscale zero-valent iron embedded on polyaniline reinforced with sodium alginate hydrogel beads. Various analytical techniques including attenuated total reflection -Fourier transform infrared spectroscopy, scanning electron microscopy with energy dispersive X-ray spectroscopy were employed to characterize these chemically synthesized hydrogel beads. The influence of different types and ratios of adsorbent materials, solution pH, adsorbent dosage, contact time, temperature, initial arsenic concentration, and the presence of co-existing ions on the adsorption process were investigated. Under optimum operating conditions; a pH range of 4-6, 80 mg of sorbent, 180 min contact time led to a remarkable arsenic removal efficiency of approximately 90.33 %. Thermodynamic, adsorption isotherm, and kinetic models provided a good description of the observed experimental results. Compared to the Freundlich and Temkin models, the Langmuir model was found to be the best fit for the experimental data, with a maximum adsorption capacity of 104.167 mg/g. Physical adsorption is mainly responsible for controlling the adsorption of arsenic ions onto the hydrogel. Thermodynamic studies verified that the adsorption process was endothermic and spontaneous.

Advances in structure designing and function tailoring strategy toward alginate-based hydrogels for efficient water remediation: A review

Alginate (mainly sodium alginate, SA), as a natural polysaccharide material, has been widely applied in water remediation due to its excellent biocompatibility, degradability, and high hydration properties. Alginate hydrogels exhibit high adsorption capacity, effectively removing heavy metal ions, dyes, antibiotics, phosphate ions, and other pollutants from wastewater. This review begins with a description of the chemical structure of sodium alginate and its physicochemical properties, followed by a detailed discussion of the preparation methods of alginate-based composite hydrogels, including physical and chemical crosslinking, emulsification, electrostatic complexation, self-assembly, ultrasound and microwave-assisted methods. Based on the different compositions of the composites, alginate-based composite hydrogels are classified into several types for the removal of specific pollutants. Moreover, the paper systematically summarizes the research progress of alginate-based composite hydrogels in adsorbing heavy metal ions, dyes, antibiotics, phosphate ions for application effects. Although alginate-based composite hydrogels demonstrate great potential in water remediation, challenges such as insufficient mechanical strength, poor regeneration ability, and low stability under extreme conditions still exist. Finally, the future development prospects of alginate composite hydrogels in the field of water remediation, as well as potential research directions to improve their adsorption performance, enhance their regeneration capacity, and improve their environmental friendliness are presented.

Green synthesis and characterization of CuO/PANI nanocomposite for efficient Pb (II) adsorption from contaminated water

This study presents the synthesis of a green polymer-based nanocomposite by incorporating green CuO nanoparticles into polyaniline (PANI) for the adsorption of Pb (II) ions from contaminated water. The nanocomposite was extensively characterized using FTIR, XRD, BET, SEM-EDX, XPS, and Raman spectroscopy, both before and after Pb(II) adsorption. Optimization studies were performed to assess the effects of key parameters, including pH, adsorbent dosage, and initial ion concentration on the adsorption process. Adsorption isotherms and kinetic models were applied to analyze the experimental data, revealing that the Freundlich isotherm provided the best fit, with a high correlation coefficient (R²) and a (1/n) value less than 1, indicating favorable adsorption conditions. Furthermore, the Avrami and pseudo-first-order kinetic models demonstrated superior fitting compared to other models. The green nanocomposite exhibited outstanding adsorption capacity, highlighting its potential as a sustainable and efficient adsorbent for Pb(II) removal from wastewater.

Comprehensive insights into the application of graphene-based aerogels for metals removal from aqueous media: Surface chemistry, mechanisms, and key features

Efficient removal of heavy metals and other toxic metal pollutants from wastewater is essential to protect human health and the surrounding vulnerable ecosystems. Therefore, significant efforts have been invested in developing practical and sustainable tools to address this issue, including high-performance adsorbents. In this respect, within the last few years, graphene-based aerogels/xerogels/cryogels (GBAs) have emerged and drawn significant attention as excellent materials for removing and recovering harmful and valuable metals from different aqueous media. Such an upward trend is mainly due to the features of the aerogel materials combined with the properties of the graphene derivatives within the aerogel's network, including the GBAs' unique three-dimensional (3D) porous structure, high porosity, low density, large specific surface area, exceptional electron mobility, adjustable and rich surface chemistry, remarkable mechanical features, and tremendous stability. This review offers a comprehensive analysis of the fundamental and practical aspects and phenomena related to the application of GBAs for metals removal. Herein, we cover all types of (bottom-up) synthesized GBAs, including true microporous graphene-based aerogels as well as other 3D graphene-based open-cell interconnected mesoporous and macroporous aerogels, foams, and sponges. Indeed, we provide insights into the fundamental understanding of the GBAs' suitability for such an important application by revealing the mechanisms involved in metals removal and the factors inducing and controlling the highly selective behavior of these distinctive adsorbents. Besides conventional adsorptive pathways, we critically analyzed the ability of GBAs to electrochemically capture metal pollutants (i.e., electrosorption) as well as their efficiency in metals detoxification through reductive mechanisms (i.e., adsorption-reduction-readsorption). We also covered the reusability aspect of graphene aerogels (GAs)-based adsorbents, which is strongly linked to the GBAs' outstanding stability and efficient desorption of captured metals. Furthermore, in view of their numerous practical and environmental benefits, the development and application of magnetically recoverable GAs for metals removal is also highlighted. Moreover, we shed light on the potential practical and scalable implementation of GBAs by evaluating their performance in continuous metals removal processes while highlighting the GBAs' versatility demonstrated by their ability to remove multiple contaminants along with metal pollutants from wastewater media. Finally, this review provides readers with an accessible overview and critical discussion of major recent achievements regarding the development and applications of GAs-based adsorbents for metal ions removal. Along with our recommendations and suggestions for potential future work and new research directions and opportunities, this review aims to serve as a valuable resource for researchers in the field of wastewater treatment and inspire further progress towards developing next-generation high-performance GBAs and expanding their application.

High-performance copper terephthalic acid metal-organic framework/gum Arabic/carrageenan composite beads for efficient lead(II) removal from aqueous solutions

Lead (Pb(II)) contamination poses a significant threat to human health and the environment. This study investigates a new approach for Pb(II) removal from polluted water using copper terephthalic acid metal-organic framework/gum Arabic/potassium carrageenan (MGC) composite beads. We synthesized copper terephthalic acid MOF, potassium carrageenan beads, and MGC composite beads to evaluate their adsorption potential. Characterization of the synthesized adsorbents was performed using TGA, nitrogen adsorption/desorption, ATR-FTIR, zeta potential, SEM, and TEM analyses, revealing that MOF > MGC > KG in thermal stability. The MGC composite exhibited a high specific surface area (398.03 m2/g) with mesopores and diverse functional groups, alongside a pH of zero point charge (pHpzc) of 6.8 and a small particle size (20 nm). The maximum Langmuir adsorption capacity for Pb(II) removal by MGC reached 374.7 mg/g under optimized conditions (20 °C, pH 5, 60 min shaking time, 3.0 g/L adsorbent dosage). The adsorption data fit well with the Pseudo-First-Order kinetic model and Langmuir and Dubinin-Radushkevich isotherm models. The adsorption process was physical, favorable, and endothermic. EDTA was used as a desorption agent, showing that the composite beads retained 97 % efficiency after ten cycles, highlighting MGC's potential as a sustainable strategy for Pb(II) remediation.

Biomimetic Hierarchies for Universal Surface Enhancement and Applications in Water Treatment

Hierarchical superstructures, ubiquitously found in nature, offer enhanced efficiency in both substance reaction and mass transport owing to their unique multiscale features. Inspired by these natural systems, this research reports a general and scalable electrochemical scheme for creating highly branched, multilevel porous superstructures on various electrically conductive substrates. These structures exhibit cascading features from centimeters, submillimeters, micrometers, down to sub-100 nm, significantly increasing the surface area of substrates, such as foams, foils, and carbon cloth by 2 orders of magnitude─among the highest reported enhancements. This versatile and low-cost method, applicable to a range of electrically conductive substrates, enables innovative flow-assisted water purification with enhanced energy efficiency. The performance, successfully removing 99% of mercury within 0.5 h at 540 rpm and meeting the U.S. Environmental Protection Agency (EPA) safety standards for drinking water, further validates the advantages of these unique structures. Overall, the reported general, economical, and versatile scheme could broadly impact energy and environmental remediation.

Remediation of water containing lead(II) using (3-iminodiacetic acid) propyltriethoxysilane graphene oxide

A novel chelating adsorbent based on (3-iminodiacetic acid) propyltriethoxysilane graphene oxide (IAT-GO) has been developed, showing exceptional promise for capturing lead. IAT-GO is made by combining a high-surface-area graphene oxide with a specially designed chelating ligand, which can selectively and efficiently remove lead. The synthesis of IAT-GO involves a two-step progression. In the first step, covalent bonds form between graphene oxide and (3-aminopropyl)-triethoxysilane (AT) through hydrolysis, condensation, and epoxide ring opening reactions. In the second step, nucleophilic substitution reactions occur between the primary amines and chloroacetic acid (CAA). A comprehensive suite of characterization techniques, including XPS, UV-Vis, XRD, Raman, FTIR, TEM, and SEM, provides detailed insights into the IAT-GO adsorbent's chemical composition and physical form, elucidating its intricate structure and morphology. Optimizing the experimental conditions for using the adsorbent material to remove Pb(II) ions from contaminated water revealed a maximum adsorption capacity of 124.0 mg/g at pH 5 and 30 min. The IAT-GO displays high selectivity for Pb(II) in a mixture of six metal ions containing 100 ppm of each one. Moreover, the IAT-GO shows 100% removal of Pb(II) for concentrations lower than 50 ppm. The excellent fit of the experimental data with the Langmuir adsorption isotherm and pseudo-second-order kinetic models (R2 > 99%) indicates that Pb(II) ion uptake onto the IAT-GO surface occurs via the monolayer formation of mercury ions. IAT-GO demonstrates exceptional potential as an innovative adsorbent for lead-contaminated water. Nitric acid (0.4 M) effectively regenerates the material, while its reusability remains impressive even after five cycles (> 97% removal efficiency). Therefore, this study highlights the development of a groundbreaking material, IAT-GO, with exceptional potential for remediating lead-contaminated water. Its high efficiency, selectivity, reusability, and cost-effectiveness make it a promising candidate for real-world applications.

Highly Selective Pb(II) Adsorption by DTPA-Functionalized Graphene Oxide/Carboxymethyl Cellulose Aerogel

Graphene oxide (GO) exhibits a strong adsorption capacity for the removal of heavy metal ions from liquids, making it a topic of increasing interest among researchers. However, a significant challenge persists in the preparation of graphene oxide-based adsorbents that possess both high structural stability and excellent adsorption capacity. In this paper, a green and environmentally friendly ternary composite aerogel based on graphene was successfully synthesized. The adsorption capacity of graphene oxide was enhanced through diethylenetriaminepentaacetic acid modification, while the incorporation of composite carboxymethyl cellulose improved the structural stability of the composite aerogel in liquid. The composite aerogel demonstrates robust interactions between its components and features a multiscale porous structure. Adsorption tests conducted with Pb(II) revealed that the GO/DTPA/CMC (GDC) composite aerogel exhibits a favorable adsorption capacity. The study of adsorption kinetics and isotherms indicated that the adsorption process follows the quasi-secondary adsorption model and Freundlich adsorption model, suggesting a chemical multilayer adsorption mechanism, and the maximum adsorption capacity for Pb(II) ions was 521.917 mg/g based on the quasi-quadratic kinetic model fitting. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) analyses, performed before and after adsorption, confirmed that the adsorption of Pb(II) primarily occurs through chelation, complexation, proton exchange, and electrostatic interactions between ions and active sites such as hydroxyl and carboxyl groups. This study presents an innovative strategy for simultaneously enhancing the adsorption properties of graphene oxide-based composite aerogels and ensuring solution stability.

Kinetic and equilibrium study of graphene and copper oxides modified nanocomposites for metal ions adsorption from binary metal aqueous solution

Presently, the main cause of pollution of natural water resources is heavy metal ions. The removal of metal ions such as nickel (Ni2+) and cadmium (Cd2+) has been given considerable attention due to their health and environmental risks. In this regard, for wastewater treatment containing heavy metal ions, graphene oxide (GO) nanocomposites with metal oxide nanoparticles (NPs) attained significant importance. In this study, graphene oxide stacked with copper oxide nanocomposites (GO/CuO-NCs) were synthesized and characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and atomic force microscopy (AFM) analytical procedures. The prepared GO/CuO-NCs were applied for the removal of Ni2+ and Cd2+ ions from a binary metal ion system in batch and continuous experiments. The obtained results revealed that GO/CuO-NCs exhibited the highest removal efficiencies of Ni2+ (89.60% ± 2.12%) and Cd2+ (97.10% ± 1.91%) at the optimum values of pH: 8, dose: 0.25 g, contact time: 60 min, and at 50 ppm initial metal ion concentration in a batch study. However, 4 mL/min flow rate, 50 ppm initial concentration, and 2 cm bed height were proved to be the suitable conditions for metal ion adsorption in the column study. The kinetic adsorption data exhibited the best fitting with the pseudo-second-order model. The adsorption isotherm provided the best-fitting data in the Langmuir isotherm model. This study suggested that the GO/CuO nanocomposites have proved to be efficient adsorbents for Ni2+ and Cd2+ ions from a binary metal system.

Cold Plasma-Assisted Extraction of Phytochemicals: A Review

In recent years, there has been growing interest in bioactive plant compounds for their beneficial effects on health and for their potential in reducing the risk of developing certain diseases such as cancer, cardiovascular diseases, and neurodegenerative disorders. The extraction techniques conventionally used to obtain these phytocompounds, however, due to the use of toxic solvents and high temperatures, tend to be supplanted by innovative and unconventional techniques, in line with the demand for environmental and economic sustainability of new chemical processes. Among non-thermal technologies, cold plasma (CP), which has been successfully used for some years in the food industry as a treatment to improve food shelf life, seems to be one of the most promising solutions in green extraction processes. CP is characterized by its low environmental impact, low cost, and better extraction yield of phytochemicals, saving time, energy, and solvents compared with other classical extraction processes. In light of these considerations, this review aims to provide an overview of the potential and critical issues related to the use of CP in the extraction of phytochemicals, particularly polyphenols and essential oils. To review the current knowledge status and future insights of CP in this sector, a bibliometric study, providing quantitative information on the research activity based on the available published scientific literature, was carried out by the VOSviewer software (v. 1.6.18). Scientometric analysis has seen an increase in scientific studies over the past two years, underlining the growing interest of the scientific community in this natural substance extraction technique. The literature studies analyzed have shown that, in general, the use of CP was able to increase the yield of essential oil and polyphenols. Furthermore, the composition of the phytoextract obtained with CP would appear to be influenced by process parameters such as intensity (power and voltage), treatment time, and the working gas used. In general, the studies analyzed showed that the best yields in terms of total polyphenols and the antioxidant and antimicrobial properties of the phytoextracts were obtained using mild process conditions and nitrogen as the working gas. The use of CP as a non-conventional extraction technique is very recent, and further studies are needed to better understand the optimal process conditions to be adopted, and above all, in-depth studies are needed to better understand the mechanisms of plasma-plant matrix interaction to verify the possibility of any side reactions that could generate, in a highly oxidative environment, potentially hazardous substances, which would limit the exploitation of this technique at the industrial level.

Eco-Friendly Electroless Template Synthesis of Cu-Based Composite Track-Etched Membranes for Sorption Removal of Lead(II) Ions

This paper reports the synthesis of composite track-etched membranes (TeMs) modified with electrolessly deposited copper microtubules using copper deposition baths based on environmentally friendly and non-toxic reducing agents (ascorbic acid (Asc), glyoxylic acid (Gly), and dimethylamine borane (DMAB)), and comparative testing of their lead(II) ion removal capacity via batch adsorption experiments. The structure and composition of the composites were investigated by X-ray diffraction technique and scanning electron and atomic force microscopies. The optimal conditions for copper electroless plating were determined. The adsorption kinetics followed a pseudo-second-order kinetic model, which indicates that adsorption is controlled by the chemisorption process. A comparative study was conducted on the applicability of the Langmuir, Freundlich, and Dubinin-Radushkevich adsorption models to define the equilibrium isotherms and the isotherm constants for the prepared composite TeMs. Based on the regression coefficients R², it has been shown that the Freundlich model better describes the experimental data of the composite TeMs on the adsorption of lead(II) ions.

Sulfur-Doped Binary Layered Metal Oxides Incorporated on Pomegranate Peel-Derived Activated Carbon for Removal of Heavy Metal Ions

In this study, a novel biomass adsorbent based on activated carbon incorporated with sulfur-based binary metal oxides layered nanoparticles (SML-AC), including sulfur (S2), manganese (Mn), and tin (Sn) oxide synthesized via the solvothermal method. The newly synthesized SML-AC was studied using FTIR, FESEM, EDX, and BET to determine its functional groups, surface morphology, and elemental composition. Hence, the BET was performed with an appropriate specific surface area for raw AC (356 m2·g−1) and modified AC-SML (195 m2·g−1). To prepare water samples for ICP-OES analysis, the suggested nanocomposite was used as an efficient adsorbent to remove lead (Pb2+), cadmium (Cd2+), chromium (Cr3+), and vanadium (V5+) from oil-rich regions. As the chemical structure of metal ions is influenced by solution pH, this parameter was considered experimentally, and pH 4, dosage 50 mg, and time 120 min were found to be the best with high capacity for all adsorbates. At different experimental conditions, the AC-SML provided a satisfactory adsorption capacity of 37.03−90.09 mg·g−1 for Cd2+, Pb2+, Cr3+, and V5+ ions. The adsorption experiment was explored, and the method was fitted with the Langmuir model (R2 = 0.99) as compared to the Freundlich model (R2 = 0.91). The kinetic models and free energy (<0.45 KJ·mol−1) parameters demonstrated that the adsorption rate is limited with pseudo-second order (R2 = 0.99) under the physical adsorption mechanism, respectively. Finally, the study demonstrated that the AC-SML nanocomposite is recyclable at least five times in the continuous adsorption−desorption of metal ions.