Novel magnetic polysaccharide/graphene oxide @Fe3O4 gel beads for adsorbing heavy metal ions

Recent Developments in the Adsorption of Heavy Metal Ions from Aqueous Solutions Using Various Nanomaterials

Water pollution is caused by heavy metals, minerals, and dyes. It has become a global environmental problem. There are numerous methods for removing different types of pollutants from wastewater. Adsorption is viewed as the most promising and financially viable option. Nanostructured materials are used as effective materials for adsorption techniques to extract metal ions from wastewater. Many types of nanomaterials, such as zero-valent metals, metal oxides, carbon nanomaterials, and magnetic nanocomposites, are used as adsorbents. Magnetic nanocomposites as adsorbents have magnetic properties and abundant active functional groups, and unique nanomaterials endow them with better properties than nonmagnetic materials (classic adsorbents). Nonmagnetic materials (classic adsorbents) typically have limitations such as limited adsorption capacity, adsorbent recovery, poor selective adsorption, and secondary treatment. Magnetic nanocomposites are easy to recover, have strong selectivity and high adsorption capacity, are safe and economical, and have always been a hotspot for research. A large amount of data has been collected in this review, which is based on an extensive study of the synthesis, characterization, and adsorption capacity for the elimination of ions from wastewater and their separation from water. The effects of several experimental parameters on metal ion removal, including contact duration, temperature, adsorbent dose, pH, starting ion concentration, and ionic strength, have also been investigated. In addition, a variety of illustrations are used to describe the various adsorption kinetics and adsorption isotherm models, providing insight into the adsorption process.

Recent progresses in bentonite/lignin or polysaccharide composites for sustainable water treatment

Today, with the growth of the human population, industrial activities have also increased. Different industries such as painting, cosmetics, leather, etc. have broadly developed, and as a result, they also produce a lot of pollutants. These pollutants can enter the environment and pollute water, air, and soil. Organic dyes, nitro compounds, drug residues, pesticides and herbicides are pollutants that should be removed from the environment. Natural polymers or biopolymers are important types of organic materials that are broadly applied for different applications. Among them, polysaccharides and lignin, which are two types of biopolymers, have attracted much consideration owing to their advantages such as biocompatibility, environmental friendly, safety, availability, etc. Polysaccharides include cellulose, gum, starch, alginate (Alg), chitin, and chitosan (CS). On the other hand, bentonite is one of the types of clays, which owing to their properties like large specific surface area, adsorption performance, naturally available, etc., have drawn the interest of many researchers. As a result, the synthesis of a composite including polysaccharide/lignin and bentonite can be very efficient for different applications, especially environmental ones. In this review, we instigated the preparation of these composites as well as the removal performance of them. In fact, we reported recent advancements in the synthesis of lignin- and polysaccharide-bentonite composites for the removal of diverse kinds of contaminants like organic dyes, nitro compounds, and hazardous materials.

Adsorption of Pb(II) in water by modified chitosan-based microspheres and the study of mechanism

In this study, a fresh three-dimensional microsphere adsorbent (CATP@SA3) was successfully synthesized by Attapulgite (ATP) and combining Chitosan (CS), incorporating them into a Sodium alginate (SA) solution, and crosslinking them in a CaCl2 solution. Multiple analyses, including XRD, TGA, FTIR, XPS, SEM-EDS, and BET were utilized to comprehensively characterize the structural makeup of CATP@SA3. These analyses revealed the presence of beneficial functional groups like hydroxyl, amino, and carboxyl groups that enhance the adsorption efficiency in adsorption procedures. CATP@SA3 was evaluated by studying different factors, including material ratio, contact time, dosage, solution pH, Pb(II) concentration, temperature, ionic strength, and aqueous environment. Three adsorption models, including kinetic, isotherm, and thermodynamic, were fitted to the experimental data. The findings demonstrated that the maximum Pb(II) adsorption capacity of CATP@SA3 was 1081.36 mg/g, with a removal rate that exceeded 70 % even after 5 cycles of use. Furthermore, correlation adsorption models revealed that the adsorption process of Pb(II) with CATP@SA3 was driven by a chemical predominantly reaction.

Effective removal of Cu(II) from water by three-dimensional composite microspheres based on chitosan/sodium alginate/silicon dioxide: Adsorption performance and mechanism

Chitosan (CS) is commonly used as an adsorbent for removing Cu(II) from water, but it has drawbacks such as solubility in dilute acid, difficulty in recycling in powder form, and short service life. This study utilized sodium alginate (SA) as a gel carrier to encapsulate CS, combined with silicon dioxide (SiO2) to improve mechanical stability. The preparation of CS/SA/SiO2 (SSC1.0) involved physical blending, CaCl2 cross-linking, and freeze-drying. Characterization methods such as SEM-EDS, FTIR, BET, and XRD were used to analyze the structural composition of SSC1.0. The material exhibited a folded surface, porous internal cross-section, nitrogen/oxygen-containing functional groups, and thermal stability in high temperatures and various aqueous environments. The adsorption performance of SSC1.0 on Cu(II) was evaluated under different conditions, showing a maximum adsorption capacity of 47.50 mg/g. The material maintained a removal rate above 70 % after 5 cycles. SSC1.0 also showed the highest removal rate of Cu(II) when applied to mine wastewater treatment. Adsorption modeling indicated that the process was driven by chemical reactions and was spontaneous and heat-absorbing.'

Research progress on blood compatibility of hemoperfusion adsorbent materials

This comprehensive review examines the latest developments in improving the blood compatibility of hemoperfusion adsorbents. By leveraging advanced coating and modification techniques, including albumin-collodion, cellulose, hydrogel, and heparin coatings, notable enhancements in blood compatibility have been achieved across diverse adsorbent types, such as carbon-based, resin-based, and polysaccharide-based materials. Despite promising laboratory results, the intricate manufacturing processes and elevated costs present significant challenges for broad clinical application. Therefore, future endeavors should focus on cost-benefit analysis, large-scale production strategies, in-depth exploration of blood-material interactions, and innovative technologies to propel the development of safer and more effective blood purification therapies.

Monolayer Adsorption of Ciprofloxacin on Magnetic Inulin/Mg-Zn-Al Layered Double Hydroxide: Advanced Interpretation of the Adsorption Process

In this study, magnetic inulin/Mg-Zn-Al layered double hydroxide (MILDH) was synthesized for the adsorption of ciprofloxacin. The application of various analytical techniques confirmed the successful formation of MILDH. For the optimization of controllable factors, Taguchi design was applied and optimum values were obtained as equilibrium time─100 min, adsorbent dose─20 mg, and ciprofloxacin concentration─30 mg/L. The highest capacity of the material was recorded as 196.19 mg/g at 298 K. Langmuir model (R2 = 0.9669-0.9832) fitted best as compared to the Freundlich model (R2 = 0.9588-0.9657), concluded the monolayer adsorption of ciprofloxacin on MILDH. Statistical physics model M 2 was found to fit best to measured data (R2 = 0.9982-0.9989), indicating that the binding of ciprofloxacin took place on two types of receptor sites (n1 and n2). The multidocking mechanism with horizontal position was suggested on the first receptor site (n1 < 1), while multimolecular adsorption of ciprofloxacin lying vertically on the second receptor site (n2 > 1) at all temperatures. The adsorption energies (E1 = 22.79-27.20 kJ/mol; E2 = 18.00-19.46 kJ/mol) illustrated that the adsorption of ciprofloxacin onto MILDH occurred through physical forces. Best fitting of the fractal-like pseudo-first-order kinetic model (R2 = 0.9982-0.9992) indicated that the adsorption of ciprofloxacin happened on the MILDH surface having different energies. X-ray photoelectron spectroscopy analysis further confirmed the adsorption mechanism of ciprofloxacin onto MILDH.

Using NaOH@Graphene oxide-Fe3O4 as a magnetic heterogeneous catalyst for ultrasonic transesterification; experimental and modelling

Burning fossil fuels causes toxic gas emissions to increase, therefore, scientists are trying to find alternative green fuels. One of the important alternative fuels is biodiesel. However, using eco-friendly primary materials is a main factor. Sustainable catalysts should have high performance, good activity, easy separation from reaction cells, and regenerability. In this study, to solve the mentioned problem NaOH@Graphene oxide-Fe3O4 as a magnetic catalyst was used for the first time to generate biodiesel from waste cooking oil. The crystal structure, functional groups, surface area and morphology of catalyst were studied by XRD, FTIR, BET, and FESEM techniques. The response surface methodology based central composite design (RSM-CCD) was used for biodiesel production via ultrasonic technique. The maximum biodiesel yield was 95.88% in the following operation: 10.52:1 molar ratio of methanol to oil, a catalyst weight of 3.76 wt%, a voltage of 49.58 kHz, and a time of 33.29 min. The physiochemical characterization of biodiesel was based to ASTM standard. The magnetic catalyst was high standstill to free fatty acid due to the five cycle's regeneration. The kinetic study results possess good agreement with first-order kinetics as well as the activation energy and Arrhenius constant are 49.2 kJ/min and 16.47 * 1010 min-1, respectively.

An eco-friendly porous hydrogel adsorbent based on dextran/phosphate/amino for efficient removal of Be(II) from aqueous solution

A novel environmentally-friendly porous hydrogel adsorbent (GHPN) is firstly designed and prepared using dextran, phosphate, and calcium hydroxide for the adsorption of Be(II). GHPN shows good adsorption selectivity for Be(II) (Kd = 1.53 × 104 mL/g). According the adsorption kinetics and thermodynamics, the theoretical adsorption capacity of GHPN to Be(II) is 43.75 mg/g (35 °C, pH = 6.5), indicating a spontaneous exothermic reaction. After being reused for 5 cycles, the adsorption and desorption efficiencies of Be(II) with GHPN are obtained to be more than 80 %, showing acceptable recycling performance. Both of the characterizations and theoretical calculations indicate that the phosphate group, hydroxyl group, and amino group own the affinity to form stable complexes with Be(II). Benefiting from the introduction of phosphate and amino, the adsorption effect of the hydrogel adsorbent on Be(II) can be greatly improved, and surface precipitation, complexation, and ligand exchange are the dominant mechanisms of beryllium adsorption. The results suggest that GHPN has great potential to be utilized as an eco-friendly and useful adsorbent of Be(II) from aqueous solution.

Covalent organic framework-sodium alginate-Ca2+-polyacrylic acid composite beads for convenient dispersive solid-phase extraction of neonicotinoid insecticides in fruit and vegetables

Neonicotinoids, the fastest-growing class of insecticides, have posed a multi-media residue problem with adverse effects on environment, biodiversity and human health. Herein, covalent organic framework-sodium alginate-Ca2+-polyacrylic acid composite beads (CACPs), facilely prepared at room temperature, were used in convenient dispersive solid-phase extraction (dSPE) and combined with high-performance liquid chromatography (HPLC) for the detection of five neonicotinoid insecticides (thiamethoxam, acetamiprid, dinotefuran, clothianidin, imidacloprid). CACPs can be completely separated within 1 min without centrifugation. After seven adsorption/desorption cycles, it maintained high extraction efficiencies (>90%). The developed method exhibited a wide linear range (0.01 ∼ 10 μg mL-1), low limits of detection (LODs, 0.0028 ∼ 0.0031 mg kg-1), and good repeatability (RSD ≤ 8.11%, n = 3). Moreover, it was applied to the determination of five neonicotinoids in fruit and vegetables (peach, pear, lettuce, cucumber, tomato), and recoveries ranged from 73.6% to 116.2%.

Sequential removal of phosphate and copper(II) ions using sustainable chitosan biosorbent

Although adsorbents are good candidates for removing phosphorus and heavy metals from wastewater, the use of biosorbents for the sequential treatment of phosphorus and copper has not yet been studied. Porous chitosan (CS)-based biosorbents (CGBs) were developed to adsorb phytic acid (PA), a major form of organic phosphate. This first adsorbate (PA) further served as an additional ligand (P-type ligand) for the CGBs (N-type ligand) to form a complex with the second adsorbate (copper). After the adsorption of PA (the first adsorbate), the spent CGBs were recycled and used as a new adsorbent to adsorb Cu(II) ions (the second adsorbate), which was expected to have a dual coordination effect through P, N-ligand complexation with copper. The interactions and complexation between CS, PA and Cu(II) ions on the PA-adsorbed CGBs (PACGBs) were investigated by performing FTIR, XPS, XRD, and SEM-EDS analyses. The PACGBs exhibited fast and enhanced adsorption of Cu(II) ions, owing to the synergistic effect of the amino groups of CS (the original ligand, N-type) and the phosphate groups of PA (an additional ligand, P-type) on the adsorption of Cu(II) ions. This is the first time that sequential removal of phosphorus and heavy metals by biosorbents has been performed using biosorbents.

Selective removal of thallium from water by MnO2-doped magnetic beads: Performance and mechanism study

Aqueous thallium has posed an increasing threat to environment as human's intensified activities in mining, refining, process and discharge. Remediation on thallium pollution has been of up-most importance to water treatment. In present work, MnO2 and magnetic Fe3O4 have been implanted to sodium alginate (SA) in presence of carboxyl methyl cellulose (CMC), and the resultant beads consisted of SA/CMC/MnO2/Fe3O4 were characterized. The materials were applied to treatment of Tl-contaminated water as adsorbent in lab. The removal results revealed that the adsorption capacity reached 38.8 mg (Tl)·g (beads)-1 and almost 100 % removal efficiency was achieved. The residual Tl was below 0.1 μg·L-1, meeting the discharge standard regulated in China. The kinetic adsorption was better described as a pseudo-second-order and three-step intra-particle diffusion model. Freundlich isotherm was well fitted the experimental data. The absorbent shown an excellent competitive specificity (KTl/M: ∼104!) over common hazardous ions Cu2+, Cd2+, Co2+, Pb2+ and Cr3+, as well as naturally abundant K+ and Na+ (KTl/M: 10-102) in mimic environmental conditions. Regeneration and reusability of the absorbent was also verified by five absorption-desorpotion cycles. XPS results revealed that a redox reaction between Mn4+ with Tl+, and an ion exchange of H+ (-O-Fe) and Tl+ were assumed to be main process for the specific capturing. This study provided an efficient SA/CMC/MnO2/Fe3O4 composite beads that could be a promising adsorbent for Tl-polluted water treatment.

Preparation of recyclable magnetic palladium nanocatalysts by dispersion strategy based on sodium alginate for reduction of p-nitrophenol and Suzuki-Miyaura coupling

Palladium (Pd) has excellent catalytic performance, its application is seriously limited by low atomic utilization and weak recovery capacity. To solve these problems, we report a universal palladium nanocatalysts preparation strategy by taking advantage of the rich chemistry of sodium alginate (SA). SA units not only self-assemble into a cross-linked porous carboxyl and hydroxyl framework but also can coat different substrates. Benefiting from the distinguished chelation of SA, metallic nanocatalysts can be achieved. As a proof-of-concept demonstration, Pd loading on nano-Fe3O4 modified with SA and investigated their catalytic capabilities. The catalyst was Fe3O4 nanoparticles encapsulated by SA film loaded with 0.4 wt% of Pd. It has a particle size around 100 nm and has good superparamagnetism with a saturation strength of 76.26 emu/g. It exhibited good catalytic activity at TOF = 660 h-1 and TOF = 4311 h-1 in typical Suzuki-Miyaura coupling reaction and the reduction of p-nitrophenol, respectively, and showed appreciable recyclability in the test of recyclability. Thus, our findings demonstrate that recyclable magnetic palladium nanocatalysts have several attractive features, such as easy preparation, outstanding catalytic activity and reusability. This work lays the foundation for the preparation of palladium nanocatalysts and the potential application of SA in the field of catalysts.

Sustainable removal of hexavalent chromium using graphene oxide - Iron oxide reinforced pectin/polyvinyl alcohol magnetic gel beads

The study investigated removal of hexavalent chromium Cr (VI) from aqueous solution using graphene oxide‑iron oxide reinforced pectin/polyvinyl alcohol magnetic gel beads prepared through co-precipitation and freeze-drying technique. Scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, vibrating sample magnetometer, N2 adsorption-desorption isotherm, and zeta potential are used for characterization. The surface area of magnetic gel beads calculated by BET method was determined to be 100.95 m2/g, significantly higher than that of GO and GO-Fe3O4. The optimum removal efficiency of GO-Fe3O4/Pec/PVA was assessed by batch method at variables such as pH(1-6), adsorption time(0-180 min), and temperature(25-35 °C). Accordingly, 0.2 g GO-Fe3O4/Pec/PVA dose, pH 2, contact time: 120 min at 25 °C were found to be the optimal conditions, and maximum adsorption capacity of GO, GO-Fe3O4 and GO-Fe3O4/Pec/PVA toward Cr(VI) removal was found to be 39.5, 62.5 and 78.55 mg g-1, respectively. Kinetic and isotherm studies indicate adsorption data follow pseudo-second-order kinetic and Langmuir isotherm models. Thermodynamic studies showed adsorption capacities of adsorbents decreased when temperature increased which indicated adsorption for Cr (VI) was an exothermic process. The activation energies were found to be 34.92, 26.57, and 35.23 KJ mol-1 for GO, GO-Fe3O4, and GO-Fe3O4/Pec/PVA, respectively, which illustrated adsorption of Cr(VI) onto the surface of adsorbents was a physical process. The beads exhibit excellent recoverability and reusability over five cycles. Overall, GO-Fe3O4/Pec/PVA demonstrates exceptional adsorption properties and can serve as an efficient, stable, less toxic, and magnetically separable adsorbent for removal of Cr(VI) from aqueous solution.

Tosyl-carrageenan/alginate composite adsorbent for removal of Pb2+ ions from aqueous solutions

The current study effectively designed novel cross-linked tosyl-carrageenan/alginate (Ts-Car/Alg) beads to remove Pb2+ ions from their aqueous solutions. To confirm the structure of the produced matrix, characterization methods such as XRD, SEM, FTIR, and EDX were used. Batch experiments were employed in order to further evaluate the adsorption efficiency of Pb2+ ions. Additionally, various variables, including contact time, solution pH, adsorbent dosage, and initial concentration of Pb2+ ions were investigated using atomic absorption. The results of this study showed that the adsorption equilibrium increased as Pb2+ ions concentration increased at pH = 5.3 after a contact time of 120 min, with 0.3 g of Ts-Car/Alg that having the best adsorption capacity at 74 mg/g. The adsorption progression was further examined using the kinetic and isothermal models. With a correlation coefficient of 0.975, the Freundlich model was thought to better fit Pb2+ ions adsorption from the isotherm investigation. Also, the adsorption kinetics were investigated using a pseudo-second-order model with 1/n ratio of 0.683. This Ts-Car/Alg adsorbent is regarded as an effective candidate to be used for water treatment because the reusability process of produced beads was successfully completed twice, and the adsorbent maintained its ability to remove Pb2+ ions. The prepared Ts-Car/Alg beads are therefore excellent candidates to be used as potent Pb2+ ions adsorbents from their aqueous solutions. The Ts-Car/Alg beads' regeneration and reusability investigation for the removal of heavy metal ions was completed in at least two successful cycles.

Drought-resistant and water-retaining tobermorite/starch composite hydrogel for the remediation of cadmium-contaminated soil

The objective of this work is utilizing fly ash to synthesize tobermorite (TOB) with a higher specific surface area and layered structure, and incorporating it into the starch/acrylic acid network to boost the drought resistance, water retention and heavy metal adsorption properties. The water absorption and water retention performance and cadmium adsorption characteristics of tobermorite/leftover rice-based composite hydrogel (TOB@LR-CH) were evaluated by water absorption swelling test, soil evaporation test and batch adsorption experiment. By adjusting the addition of TOB and other synthesized conditions, the swelling property (from 114.80 g/g to 322.64 g/g), water retention (71.80 %, 144 h) and Cd2+ adsorption characteristics (up to 591.36 mg/g) were significantly enhanced. Adding a moderate amount of TOB (2 wt%) provided the most uniform tobermorite dispersion during synthesis, and TOB2@LR-CH exhibited the most stable three-dimensional network and highest proportion of effective TOB. The adsorption behavior of cadmium on TOB2@LR-CH was more consistent with the pseudo-second-order kinetics and Langmuir isotherm models. Additionally, the regeneration test results displayed that the adsorption removal rate of cadmium by TOB2@LR-CH adsorbent remained stable after 5 cycles. This study demonstrates that TOB@LR-CH has good water absorption and water retention potential in arid and semi-arid soils, and also has potential application prospects in remediating Cd(II)-contaminated soil.

Preparation of magnetic sodium alginate/sodium carboxymethylcellulose interpenetrating network gel spheres and use in superefficient adsorption of direct dyes in water

The rapid development of the printing and dyeing industry has led to the production of a large amount of high-density printing and dyeing wastewater, and technology for its effective treatment has become a focus of research. To construct a polymeric adsorbent material with abundant functional groups for the efficient adsorption of dye wastewater, a novel magnetic sodium alginate/carboxymethylcellulose interpenetrating network gel sphere (Fe3O4@SA/CMC-Fe) was prepared by co-blending sodium alginate (SA) and sodium carboxymethylcellulose (CMC) with Fe3O4; Fe3O4@SA/CMC-Fe was characterized by SEM-EDS, XRD, TGA, FT-IR, UV-Vis, VSM, BET-BJH and XPS. Static adsorption experiments showed that the optimal rates for adsorption of DV 51 and DR 23 from solutions with neutral pH values by Fe3O4@SA/CMC-Fe were up to 96 %, the adsorption process exhibited a Langmuir adsorption isotherm, and the dynamic adsorption process was accurately described by the pseudo-second-order kinetic model. A thermodynamic study showed that the adsorption reactions were all spontaneous exothermic reactions with increasing entropy. The mechanism for adsorption of the dyes by Fe3O4@SA/CMC-Fe involved hydrogen bonding, complexation and electrostatic adsorption. In summary, Fe3O4@SA/CMC-Fe is a green, simple, recyclable and highly efficient magnetic adsorbent that is expected to be widely used in treating dye wastewaters over a wide pH range.

Graphene oxide nanosheets immobilised on honeycomb pore structure of pomelo peel for enhanced removal of methylene blue

Herein, for the first time, a simple, green, direct immersion immobilisation method is reported for graphene oxide (GO) nanosheets using pomelo peel (PL) as a substrate. A GO/PL porous sponge was successfully prepared and used to remove methylene blue (MB) from dye wastewater. Considering the porosity, hydrophilicity and elasticity of the PL, the PL was placed in a GO aqueous suspension through direct immersion immobilisation. The carboxyl and hydroxyl groups in the peel could effectively capture and immobilise the GO nanosheets. GO was adsorbed into the PL pores and dispersed throughout the PL. Finally, the prepared super-hydrophilic and elastic GO/PL exhibited excellent adsorption performance towards MB in dye wastewater. The adsorption results revealed that the adsorption behaviour was consistent with the Langmuir isotherm and quasi-secondary kinetic models. The maximum equilibrium adsorption capacity of GO/PL towards MB was 124.2 mg/g, exceeding the values obtained for most of the previously reported adsorbents. Moreover, after five consecutive adsorption-desorption cycles, GO/PL retained 75% of its initial adsorption capacity. Mechanistic analysis revealed that pore filling, electrostatic attraction, ion exchange and hydrogen bonding interactions are the primary driving forces facilitating MB adsorption.

Myrica esculenta Leaf Extract-Assisted Green Synthesis of Porous Magnetic Chitosan Composites for Fast Removal of Cd (II) from Water: Kinetics and Thermodynamics of Adsorption

Heavy metal contamination in water resources is a major issue worldwide. Metals released into the environment endanger human health, owing to their persistence and absorption into the food chain. Cadmium is a highly toxic heavy metal, which causes severe health hazards in human beings as well as in animals. To overcome the issue, current research focused on cadmium ion removal from the polluted water by using porous magnetic chitosan composite produced from Kaphal (Myrica esculenta) leaves. The synthesized composite was characterized by BET, XRD, FT-IR, FE-SEM with EDX, and VSM to understand the structural, textural, surface functional, morphological-compositional, and magnetic properties, respectively, that contributed to the adsorption of Cd. The maximum Cd adsorption capacities observed for the Fe3O4 nanoparticles (MNPs) and porous magnetic chitosan (MCS) composite were 290 mg/g and 426 mg/g, respectively. Both the adsorption processes followed second-order kinetics. Batch adsorption studies were carried out to understand the optimum conditions for the fast adsorption process. Both the adsorbents could be regenerated for up to seven cycles without appreciable loss in adsorption capacity. The porous magnetic chitosan composite showed improved adsorption compared to MNPs. The mechanism for cadmium ion adsorption by MNPs and MCS has been postulated. Magnetic-modified chitosan-based composites that exhibit high adsorption efficiency, regeneration, and easy separation from a solution have broad development prospects in various industrial sewage and wastewater treatment fields.

Recent advances of magnetic chitosan hydrogel: Preparation, properties and applications

Magnetic chitosan hydrogels are organic-inorganic composite material with the characteristics of both magnetic materials and natural polysaccharides. Due to its biocompatibility, low toxicity and biodegradability, chitosan, a natural polymer has been widely used for preparing magnetic hydrogels. The addition of magnetic nanoparticles to chitosan hydrogels not only improves their mechanical strength, but also endows them with magnetic thermal effects, targeting capabilities, magnetically-sensitive release characteristics, easy separation and recovery, thus enabling them to be used in various applications including drug delivery, magnetic resonance imaging, magnetothermal therapy, and adsorption of heavy metals and dyes. In this review, the physical and chemical crosslinking methods of chitosan hydrogels and the methods for binding magnetic nanoparticles in hydrogel networks are first introduced. Subsequently, the properties of magnetic chitosan hydrogels were summarized including mechanical properties, self-healing, pH responsiveness and properties in magnetic fields. Finally, the potential for further technological and applicative advancements of magnetic chitosan hydrogels is discussed.

Nanotechnology as an efficient and effective alternative for wastewater treatment: an overview

The increase in the surface and groundwater contamination due to global population growth, industrialization, proliferation of pathogens, emerging pollutants, heavy metals, and scarcity of drinking water represents a critical problem. Because of this problem, particular emphasis will be placed on wastewater recycling. Conventional wastewater treatment methods may be limited due to high investment costs or, in some cases, poor treatment efficiency. To address these issues, it is necessary to continuously evaluate novel technologies that complement and improve these traditional wastewater treatment processes. In this regard, technologies based on nanomaterials are also being studied. These technologies improve wastewater management and constitute one of the main focuses of nanotechnology. The following review describes wastewater's primary biological, organic, and inorganic contaminants. Subsequently, it focuses on the potential of different nanomaterials (metal oxides, carbon-based nanomaterials, cellulose-based nanomaterials), membrane, and nanobioremediation processes for wastewater treatment. The above is evident from the review of various publications. However, nanomaterials' cost, toxicity, and biodegradability need to be addressed before their commercial distribution and scale-up. The development of nanomaterials and nanoproducts must be sustainable and safe throughout the nanoproduct life cycle to meet the requirements of the circular economy.

Adsorption behavior and mechanism of action of magnetic MIL-100(Fe) on MB

Dye wastewater seriously affects human living environment and human health. This experiment develops green and efficient recyclable Fe₃O₄@MIL-100(Fe) under room temperature conditions. The microscopic morphology, chemical structure and magnetic properties of Fe₃O₄@MIL-100 (Fe) were characterized by SEM, FT-IR, XRD and VSM, and the adsorption capacity and adsorption mechanism of the adsorbent on methylene blue (MB) were investigated. The results showed that MIL-100(Fe) was successfully grown on Fe₃O₄, and the composite had excellent crystalline shape and morphology and good magnetic response. The specific surface area of Fe₃O₄@MIL-100(Fe) is 1203.18 m² g^-1 by N₂ adsorption isothermal curve, and MIL-100(Fe) still has high specific surface area after compounding with magnetic particles. The adsorption process follows the quasi-level kinetic equation and the Langmuir isothermal model, according to which the adsorption capacity of Fe₃O₄@MIL-100 (Fe) on MB can be up to 487.8 mg g^-1 for a single molecular layer. The thermodynamic experiments show that the adsorption of MB by the adsorbent is a spontaneous heat absorption process. In addition, the adsorption amount of Fe₃O₄@MIL-100 (Fe) on MB was still maintained at 88.4% after 6 cycles with good reusability, and its crystalline shape did not change significantly, indicating that Fe₃O₄@MIL-100 (Fe) can be used as an efficient and regenerable adsorbent for the treatment of printing and dyeing wastewater.

Adsorption mechanism and removal efficiency of magnetic graphene oxide-chitosan hybrid on aqueous Zn(II)

Magnetic architecture incorporating graphene-chitosan has demonstrated encouraging application in wastewater purification. Herein, a ternary hybrid based on Fe₃O₄-graphene oxide-chitosan (MGOCS) was fabricated and employed as adsorbent to remove aqueous Zn(II). The adsorption mechanism was intensively inspected based on the hard and soft acid base (HSAB) theory. Results present, MGOCS removes 96.73 % of Zn(II) in 38 min, with adsorption quantity 386.92 mg·g^-1. Electron transfer and energy lowering determined by the HSAB theory illuminate the plausible adsorption sites in each component of MGOCS: O₂^- in Fe₃O₄, -C(=O)NH-, -NH₂ in chitosan and -OH in graphene oxide. The exploration was upheld by spectroscopic analyses. Thereby, following adsorption mechanism was proposed. (1) ZnO bond was formed featured by electron donation. (2) The -C(=O)NH- group formed via amidation between graphene oxide and chitosan contributes to Zn(Π) uptake. This work may inspire the development of efficient adsorbent based on magnetic graphene-chitosan for wastewater remediation.

Two recyclable and complementary adsorbents of coal-based and bio-based humic acids: High efficient adsorption and immobilization remediation for Pb(II) contaminated water and soil

Humic acid can effectively bind heavy metals and is a promising remediation agent for heavy metals-contaminated water and soil. Many successful applications of humic acid have been reported, but rarely studied the specific process and mechanism of heavy metal removal by humic acids from water and soil, especially the simultaneous application of coal-based and bio-based humic acids. In this work, two kinds of coal-based and bio-based humic acid materials (CHA and BHA) from weathered coal and rice husk were industrially produced and studied their Pb(II) adsorption and immobilization characteristics and mechanisms in water and soil. The batch adsorption experiments obtained the Pb(II) adsorption by CHA and BHA both were spontaneous and endothermic monolayer chemisorption and controlled by three rate-limiting steps (bulk, film, and pore) in the adsorption process. CHA and BHA had highly efficient Pb(II) adsorption capacities, obtained their maximum adsorption capacity was 201 and 188 mg g^-1, respectively. In addition to the two main adsorption mechanisms of ion exchange and surface complexation, electrostatic interaction, precipitation reaction, and π-π interaction were also involved. Soil culture experiments showed that CHA and BHA both exhibited a highly efficient immobilization effect on Pb(II)-contaminated soil, and CHA and BHA had a better synergistic promotion effect. Compared with the CK soil, the content of DTPA-Pb(II) decreased by 10.2-13.2% and the content of RES-Pb(II) increased by 14-22% in soils treated with different humic acids. Ion exchange, complexation, precipitation, and electrostatic attraction promote the transformation of unstable Pb(II) to stable Pb(II), which was of great significance for the immobilization of Pb(II) in soil. Overall, CHA and BHA have the potential to be used as green, efficient, and promising adsorbents to remove and immobilize Pb(II) from wastewater and soil.

Design of glucono-δ-lactone-induced pinto bean protein isolate/κ-carrageenan mixed gels with various microstructures: fabrication, characterization, and release behavior

BACKGROUND

Protein gels are used for different purposes, such as providing good texture, serving as fat replacers, and enhancing the nutritional and functional characteristics of foods. They can also deliver controlled release agents for sensitive drugs. The objective of this study was to investigate the impact of κ-carrageenan (kcr) concentration (0, 1.5, 3, and 4.5 mg g^-1 ) on the morphological and physicochemical properties and release behavior of glucono-δ-lactone (GDL)-induced pinto bean protein aggregate (PBA) gels.

RESULTS

When κ-carrageenan concentration increased from 0 to 1.5 and 3 mg.g^-1 , the firmness of the samples increased significantly, by 2.04 and 3.7 fold, respectively (P < 0.05). A compact and homogenous network with considerable strength and maximum water-holding capacity (97.52 ± 1.17%) was obtained with the addition of 3 mg g^-1 κ-carrageenan to the gel system. Further increasing the κ-carrageenan concentration to 4.5 mg g^-1 produced a coarse gel structure with higher storage modulus (G'), firmness (6.30-fold), thermal stability, and entrapment efficiency (85.6%). Depending on the κ-carrageenan concentration, various microstructures from protein continuous phase to κ-carrageenan continuous phase were observed. The release test indicated that 70.25% of the loaded curcumin was released in the simulated gastrointestinal tract for pure PBA gels. In contrast, for binary gels containing 4.5 mg g^-1 κ-carrageenan, curcumin was protected in the upper gastrointestinal tract, and 64.45% of loaded curcumin was delivered to the colon.

CONCLUSION

Our study showed that κ-carrageenan/PBA gels had high entrapment efficiency and could protect curcumin in the upper gastrointestinal tract. The hydrogels are therefore very valuable for colon-targeting delivery purposes. © 2022 Society of Chemical Industry.

Reusable Sugar-Based Gelator for Marine Oil-Spill Recovery and Waste Water Treatment

In this work, the gelation ability of a series of novel pyridine-based glucose tailored gelators (DPHAEN, DPHABN, and DPHAHN) with a flexible alkyl chain has been examined in binary solvent mixtures using a number of techniques, for example, UV spectroscopy, FT-IR spectroscopy, NMR spectroscopy, rheology measurement, SEM, XRD, and computational study. Proposed herein is an environment-friendly method to realize toxic dye separation and oil/water separation. It has been found that gels in a selective binary solvent mixture are efficient reusable absorbers of toxic dye molecules. A new gravitational force-driven, simple one-step, toxic dye removal and oil-water separation method is presented for sustainable filtration of waste water and simultaneous collection of oil. The gel column also showed high stability and reusability over repeated use and can be easily scaled for efficient clean-up of a large number of toxic dyes and oil spills present in water. Studies also exposed that the gel column can simultaneously separate dye molecules and mineral oils from water. This simple, green, and efficient method overcomes a nontrivial hurdle for environmentally safe separation of toxic dyes as well as oil/water mixtures and offers insights into the design of advanced materials for practical oil/water separation.

Nanotechnology- A ray of hope for heavy metals removal

Environmental effects of heavy metal pollution are considered as a widespread problem throughout the world, as it jeopardizes human health and also reduces the sustainability of a cleaner environment. Removal of such noxious pollutants from wastewater is pivotal because it provides a propitious solution for a cleaner environment and water scarcity. Adsorption treatment plays a significant role in water remediation due to its potent treatment and low cost of adsorbents. In the last two decades, researchers have been highly focused on the modification of adsorption treatment by functionalized and surface-modified nanomaterials which has spurred intense research. The characteristics of nano adsorbents attract global scientists as it is also economically viable. This review shines its light on the functionalized nanomaterials application for heavy metals removal from wastewater and also highlights the importance of regeneration of nanomaterials in the view of visualizing the economic aspects along with a cleaner environment. The review also focused on the proper disposal of nanomaterials with crucial issues that persist in the adsorption process and also emphasize future research modification at a large-scale application in industries.

Ni-alginate hydrogel beads for establishing breakthrough curves of lead ions removal from aqueous solutions

The scientific impact of this work is the protection of the environment from hazardous pollutants using a column technique. Besides its higher stability at working pH and its time persisting, Ni-alginate has a higher ability to remove lead ions compared to the other prepared beads (Sr-alginate, Co-alginate, and Ca-alginate). Also, Ni-alginate possessed a higher removal percent, 93.3%, toward Pb2+ than the other ions, taking the sorption order of Pb2+ > Sr2+ > Co2+ > Cd2+ > Zn2+. Therefore, this study focused on using Ni-alginate as a selective sorbent for lead ions. Fixed-bed column was employed for the sorption process. The results for that efficiency are presented as breakthrough curves in view of the impact of various parameters; influent flow rate (1.5, 3.0, and 5.0 mL/min), lead concentration (100, 150, and 200 mg/L), and bed depth of sorbent (3.0, 5.0, and 7.0 cm). Breakthrough modeling including Thomas and Yan models was employed. The outcomes indicated that Thomas theory is more applicable. The overall outcomes indicated that Ni-alginate is recommended for selective removal of Pb2+ from waste solutions.

Prospects of Polymeric Nanocomposite Membranes for Water Purification and Scalability and their Health and Environmental Impacts: A Review

Water shortage is a major worldwide issue. Filtration using genuine polymeric membranes demonstrates excellent pollutant separation capabilities; however, polymeric membranes have restricted uses. Nanocomposite membranes, which are produced by integrating nanofillers into polymeric membrane matrices, may increase filtration. Carbon-based nanoparticles and metal/metal oxide nanoparticles have received the greatest attention. We evaluate the antifouling and permeability performance of nanocomposite membranes and their physical and chemical characteristics and compare nanocomposite membranes to bare membranes. Because of the antibacterial characteristics of nanoparticles and the decreased roughness of the membrane, nanocomposite membranes often have greater antifouling properties. They also have better permeability because of the increased porosity and narrower pore size distribution caused by nanofillers. The concentration of nanofillers affects membrane performance, and the appropriate concentration is determined by both the nanoparticles' characteristics and the membrane's composition. Higher nanofiller concentrations than the recommended value result in deficient performance owing to nanoparticle aggregation. Despite substantial studies into nanocomposite membrane manufacturing, most past efforts have been restricted to the laboratory scale, and the long-term membrane durability after nanofiller leakage has not been thoroughly examined.

Preparation and characterization of polyethyleneimine functionalized magnetic graphene oxide as high uptake and fast removal for Hg (II)

Polyethyleneimine functionalized magnetic graphene oxide adsorbent (PEI-mGO) was synthesized by introducing polyethyleneimine onto Fe₃O₄/graphene oxide. The structures and morphologies of PEI-mGO was identified by using Fourier-tranform infrared (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) methods. Quantities of bar-like Fe₃O₄ nanoparticles were observed on the surfaces of PEI-mGO. The adsorption of PEI-mGO for Cu(II), Pb(II), Hg(II), Co(II) and Cd(II) was compared. The adsorption results indicated that PEI-mGO showed higher uptake for Hg(II) than the other ions. The influence of various variables for the adsorption of Hg(II) on PEI-mGO was explored. The adsorption kinetics and isotherm could be described well by the pseudo-second-order and Langmuir models. The maximal uptake of PEI-mGO for Hg(II) from Langmuir model was 857.3 mg g^-1, which was higher than that reported previously. The adsorption removal was a fast and endothermic process governed by the chemical process. The uptake increased with increasing temperature. PEI-mGO showed an excellent performance for removal of Hg(II) with 93.3% removal efficiency from simulated wastewater. Adsorption-desorption cycled experiments indicated that PEI-mGO could be recycled. PEI-mGO could be easily separated from the adsorbed solution by using a magnet. Hence, this novel adsorbent would be promising for the removal of Hg(II) from wastewater.

Graphene oxide modified κ-carrageenan/sodium alginate double-network hydrogel for effective adsorption of antibiotics in a batch and fixed-bed column system

The treatment of antibiotic wastewater pollution is imminent, the studies of double-network hydrogels as adsorbents have gradually increased, it is quite important to develop a non-toxic hydrogel with excellent properties as adsorbent. In this study, a graphene oxide modified κ-carrageenan/sodium alginate (GO-κ-car/SA) gel was prepared by calcium hardening. The addition of GO nanosheets enhances the mechanical strength and anti-swelling property of the double-network hydrogel, making it possible for the application in the fixed-bed column system. The elastic modulus is twice as much as the hydrogel without GO. The maximum adsorption capacity in the experiments of the GO-κ-car/SA gel for CIP and OFL can reach 272.18 mg g^-1 and 197.39 mg g^-1, respectively. The GO-κ-car/SA gel always remains negatively charged, which means that the adsorption capacity of the gel is better in an acidic environment. In the fixed-bed column system, through Thomas fitting, the maximum adsorption capacity of the simulated OFL wastewater (200 mg L^-1) is 83.99 mg g^-1. The adsorption mechanism of antibiotics by GO-κ-car/SA gel depends on hydrogen bond, functional groups and electrostatic adsorption. The good hydrophilic properties, excellent adsorption capacity and high mechanical strength, which can ensure that the adsorbent is in full contact with the contaminants without major deformation or damage, makes the study more helpful for the further study on hydrogel in the fixed-bed column system.

Graphene-based nanocomposites and nanohybrids for the abatement of agro-industrial pollutants in aqueous environments

Incessant release of a large spectrum of agro-industrial pollutants into environmental matrices remains a serious concern due to their potential health risks to humans and aquatic animals. Existing remediation techniques are unable to remove these pollutants, necessitating the development of novel treatment approaches. Due to its unique structure, physicochemical properties, and broad application potential, graphene has attracted a lot of attention as a new type of two-dimensional nanostructure. Given its chemical stability, large surface area, electron mobility, superior thermal conductivity, and two-dimensional structure, tremendous research has been conducted on graphene and its derived composites for environmental remediation and pollution mitigation. Various methods for graphene functionalization have facilitated the development of different graphene derivatives such as graphene oxide (GO), functional reduced graphene oxide (frGO), and reduced graphene oxide (rGO) with novel attributes for multiple applications. This review provides a comprehensive read on the recent progress of multifunctional graphene-based nanocomposites and nanohybrids as a promising way of removing emerging contaminants from aqueous environments. First, a succinct overview of the fundamental structure, fabrication techniques, and features of graphene-based composites is presented. Following that, graphene and GO functionalization, i.e., covalent bonding, non-covalent, and elemental doping, are discussed. Finally, the environmental potentials of a plethora of graphene-based hybrid nanocomposites for the abatement of organic and inorganic contaminants are thoroughly covered.

Aloe Vera Functionalized Magnetic Nanoparticles Entrapped Ca Alginate Beads as Novel Adsorbents for Cu(II) Removal from Aqueous Solutions

CABs (Ca alginate beads), AVCABs (Aloe vera Ca alginate beads), and AVMNCABs (Aloe-vera functionalized magnetic nanoparticles entrapped Ca alginate beads) were developed as adsorbents for the removal of Cu(II) from aqueous solutions. The materials were characterized using Fourier-transform infrared (FTIR) spectroscopy, high-resolution scanning electron microscopic (HR-SEM) analysis, X-ray diffraction (XRD), energy-dispersive X-ray (EDX) spectroscopy, and a vibrating-sample magnetometer (VSM). The effect of several parameters, such as pH, time, temperature, adsorbent dose, etc., were investigated. The adsorption isotherm of Cu(II) was adjusted best to the Langmuir model. The maximum adsorption capacities were 111.11 mg/g, 41.66 mg/g, and 15.38 mg/g for AVMNCABs, AVCABs, and CABs, respectively. The study of the adsorption kinetics for Cu(II) ions on beads followed a pseudo-second-order kinetic model, with a very good correlation in all cases. The adsorption studies used a spectrophotometric method, dealing with the reaction of Cu(II) with KSCN and variamine blue.

XPS and NMR analyze the combined forms of Pb in Cladophora rupestris subcells and its detoxification

In this study, the combined forms of Pb in Cladophora rupestris (L.) (C. rupestris) were investigated via X-ray photoelectron spectroscopy (XPS) and nuclear magnetic resonance (NMR), different Pb concentrations (0, 0.5, and 5.0 mg/L), and C. rupestris subcells were explored. Results showed that combined forms of Pb mainly account for Pb-polysaccharides (Pb-OH of carbohydrates) in the cell wall, Pb-protein (Pb-N= and (C-N-)₂Pb) in the organelle, and Pb-organic acid (Pb-sulfates, (CO)₂-Pb and (COO)₂-Pb) in the soluble fraction. Pb-S-containing group (Pb-C-S) could formed in subcelluar when C. rupestris was subjected to high Pb stress. Meanwhile, Pb²⁺ could penetrate the C. rupestris cells via the formed chelate between GSH/MT and -OH functional groups. Results could help understand the role of subcellular fraction in the algae remediation and detoxification to heavy metal.

The optimization effect of different parameters on the super hydrophobicity of prickly-shaped carbonyl iron particles

In this study, the effects of glucose concentration, temperature, and time parameters of the hydrothermal reaction on the growth of prickly-shaped carbonyl iron were studied by using an experimental design to obtain the maximum superhydrophobicity of the magnetic particles. The experimental design was carried out by Response Surface Methodology (RSM) analysis using the Central Composite Design (CCD) method. Field Emission Scanning Electron Microscopy (FESEM) analysis was performed to qualitatively assess the growth of the prickly-shaped carbonyl iron, and Water Contact Angle (WCA) analysis was used to quantify the superhydrophobicity of the resulting particles. The results revealed that the elevation of the concentration and time increased the roughness (prickly shape) of the particle surface and contact angle up to a point, after which it did not affect them. The temperature elevation caused an increase in the prickly shape of the particles and contact angles and then reduced them. The optimum concentration, temperature, and time were 0.75 Mol L⁻¹, 170 °C, and 4 hours, respectively, for the maximum growth of prickly-shaped particles and the maximum contact angle was 169.7°. Fourier-Transform Infrared Spectroscopy (FT-IR) and thermogravimetric analysis (TGA) results confirmed the presence of glucose and stearic acid chemically bonded to the carbonyl iron particles. The X-ray Diffraction (XRD) results showed that the carbonyl iron had been not converted into iron oxide during the synthesis procedures of the superhydrophobic particles. Vibrating Sample Magnetometer (VSM) analysis showed that making the particles superhydrophobic had little effect on the magnetization reduction.

The effects of glucose concentration, temperature, and time parameters of the hydrothermal reaction on the growth of prickly-shaped magnetic particles were studied by using an experimental design to obtain the maximum superhydrophobicity.

Synthesis and application of graphene oxide as a nanoadsorbent to remove Cd (II) and Pb (II) from water: adsorption equilibrium, kinetics, and regeneration

In this work, graphene oxide (GO) was synthesized by the modified Hummers method. The nanomaterial was characterized by FTIR and Raman spectroscopy, SEM, and pH at the point of zero charge. GO exhibited typical characteristics of graphene-based materials, indicating that graphite oxidation and exfoliation occurred successfully. Cd (II) and Pb (II) adsorption onto GO was carried out in batch systems, in which the effect of adsorbent dosage, contact time, and initial adsorbate concentration were evaluated. Langmuir, Freundlich, and Sips isotherm models, as well as pseudo order models and Elovich kinetic equation were applied to adsorption experimental data. Results indicated that increasing adsorbent mass, the removal efficiency of Cd (II) and Pb (II) increased. Freundlich isotherm better described Pb (II) adsorption (R² = 0.96), while Cd (II) isotherm showed linear behavior. From the Akaike's AIC parameter, kinetic data were satisfactorily described by pseudo-first order (Cd (II)) and pseudo-n order (Pb (II)) models. GO was successfully subjected to five regeneration cycles, maintaining high efficiency (> 90%) in all cycles. GO showed high potential for the adsorption of Cd (II) and Pb (II) from aqueous solution, due to its high adsorption capacity, rapid Cd (II) and Pb (II) intakes, and great regeneration performance.

Polysaccharides Composite Materials as Carbon Nanoparticles Carrier

Nanotechnology is a dynamically developing field of science, due to the unique physical, chemical and biological properties of nanomaterials. Innovative structures using nanotechnology have found application in diverse fields: in agricultural and food industries, where they improve the quality and safety of food; in medical and biological sciences; cosmetology; and many other areas of our lives. In this article, a particular attention is focused on carbon nanomaterials, especially graphene, as well as carbon nanotubes and carbon quantum dots that have been successfully used in biotechnology, biomedicine and broadly defined environmental applications. Some properties of carbon nanomaterials prevent their direct use. One example is the difficulty in synthesizing graphene-based materials resulting from the tendency of graphene to aggregate. This results in a limitation of their use in certain fields. Therefore, in order to achieve a wider use and better availability of nanoparticles, they are introduced into matrices, most often polysaccharides with a high hydrophilicity. Such composites can compete with synthetic polymers. For this purpose, the carbon-based nanoparticles in polysaccharides matrices were characterized. The paper presents the progress of ground-breaking research in the field of designing innovative carbon-based nanomaterials, and applications of nanotechnology in diverse fields that are currently being developed is of high interest and shows great innovative potential.

Chitin/egg shell membrane@Fe3O4 nanocomposite hydrogel for efficient removal of Pb2+ from aqueous solution

The development of adsorbents by using the byproducts or waste from large-scale industrial and agricultural production is of great significance, and is considered to be an economic and efficient strategy to remove the heavy metals from polluted water. In this work, a novel chitin/EM@Fe3O4 nanocomposite hydrogel was obtained from a NaOH/urea aqueous system, where the proteins of egg shell membrane and Fe3O4 nanoparticles were chemically bonded to chitin polymer chains with the help of epichlorohydrin. Due to the existence of a large number of -NH2, -OH, -CONH-, -COOH and hemiacetal groups, the adsorption efficiency for Pb2+ into the absorbent was dramatically enhanced. The experimental results revealed that the adsorption behavior strongly depends on various factors, such as initial pH, initial Pb2+ concentration, incubation temperature and contact time. The kinetic experiments indicated that the adsorption process for Pb2+ in water solution agreed with the pseudo-second-order kinetic equation. The film diffusion or chemical reaction is the rate limiting process in the initial adsorption stage, and the adsorption of Pb2+ into the nanocomposite hydrogel can well fit the Langmuir isotherm. Thermodynamic analysis demonstrated that such adsorption behaviors were dominated by an endothermic (ΔH° > 0) and spontaneous (ΔG° < 0) process.

Preparation and applications of chitosan and cellulose composite materials

Chitosan is a natural fiber, chemically cellulose-like biopolymer, which is processed from chitin. Its use as a natural polymer is getting more attention because it is non-toxic, renewable, and biocompatible. However, its poor mechanical and thermal strength, particle size, and surface area restrict its industrial use. Consequently, to improve these properties, cellulose and/or inorganic nanoparticles have been used. This review discusses the recent progress of chitosan and cellulose composite materials, their preparation, and their applications in different industrial sectors. It also discusses the modification of chitosan and cellulose composite materials to allow their use on a large scale. Finally, the recent development of chitosan composite materials for drug delivery, food packaging, protective coatings, and wastewater treatment are discussed. The challenges and perspectives for future research are also considered. This review suggests that chitosan and cellulose nano-composite are promising, low-cost products for environmental remediation involving a simple production process.