Application of carboxymethyl polysaccharides as bio-sorbents for the sequestration of heavy metals in aquatic environments

Quaternization of guar gum with in situ generated hydroxyprpopyl dimethylbenzyl ammonium chloride from N,N-dimethylbenzylamine and epichlorohydrin for the effective removal of anionic dyes from simulated wastewater

We report a quaternized guar gum (QGG) by grafting hydroxypropyl dimethylbenzyl ammonium chloride (HPDMBAC) onto guar gum (GG). HPDMBAC was obtained in situ from N,N-dimethylbenzyl amine and epichlorohydrin. The as-synthesized QGG was characterized by FTIR, XRD, FESEM, BET, EDS, zeta potential, and surface charge analysis. The QGG is a rapid and efficient adsorbent for the anionic dyes, Congo red (CR) and methyl orange (MO), from simulated wastewater with respective %removal of 96.16 % for CR in 25 min and 98.02 % for MO in 30 min. The adsorption followed pseudo-second order kinetics with the highest value of correlation coefficient and the lowest values of error function (χ2), root mean square error (RMSE) and normalized standard deviation (Δq%) for both the dyes. The Langmuir isotherm showed the better fitting of adsorption data with high maximum adsorption capacity of 213.30 and 305.44 mgg-1 for CR and MO, respectively. Additionally, the small value of χ2, RMSE and Δq% for Langmuir isotherm revealed its best fitting for both the dyes. Furthermore, the QGG demonstrated significant reusability for both the dyes studied for 15th adsorption-desorption cycles. Thus, QGG has a palpable potential as a cost-effective and sustainable adsorbent for removal of anionic dyes from wastewater.

Facile and green fabrication of biodegradable aerogel from chitosan derivatives/modified gelatin as absorbent for oil removal

Frequent oil spills have caused increasingly severe pollution of marine water bodies. As a result, exploring green and efficient aerogels to tackles oil pollution is in high demand. In this work, a unique strategy for preparing all-biomass aerogel was innovatively proposed. A series of all-biomass CW&BW@DCGA aerogels were successfully prepared by multiple dynamic covalent bonding, in which carboxymethyl chitosan (CMCS) as the substrate material, modified gelatin (Gel-ADH) as a reinforcing agent, and dialdehyde β-cyclodextrin (Da-β-CD) as a non-toxic cross-linking agent. The resulting aerogels were further hydrophobically modified with a green and natural wax blend consisting of carnauba wax (CW) and beeswax (BW). The experimental results demonstrated that incorporating Gel-ADH significantly improved the elastic properties of the materials. Specifically, when m(CMCS):m(Gel-ADH) = 7:3, the aerogel exhibited outstanding resilience, with 60 % compressive strain. In addition, CW&BW@DCGA displayed excellent hydrophobicity, boasting a water contact angle as high as 148.6°, and impressive absorption capacities ranging from 31.7 to 62.5 g/g towards different oils. Its adsorption capacity remained close to 70 % after 10 cycles, indicating favorable reusability. The dynamic absorption processes towards gasoline, diesel, and soybean oil were also well fitted with the pseudo-second-order kinetic model, suggesting that the process is primarily governed by chemisorption.

Unveiling the Potential of Protein-Based Sustainable Antibacterial Materials

The surge in bacterial growth and the escalating resistance against a multitude of antibiotic drugs have burgeoned into an alarming global threat, necessitating urgent and innovative interventions. In response to this peril, scientists have embarked on the development of advanced biocompatible antibacterial materials, aiming to counteract not only bacterial infections but also the pervasive issue of food spoilage resulting from microbial proliferation. Protein-based biopolymers and their meticulously engineered composites are at the forefront of this endeavor. Their potential in combating this severe global concern presents an approach that intersects the domains of biomedicine and environmental science. The present review article delves into the intricate extraction processes employed to derive various proteins from their natural sources, unraveling the complex biochemical pathways that underpin their antibacterial properties. Expanding on the foundational knowledge, the review also provides a comprehensive synthesis of functionalized proteins modified to enhance their antibacterial efficacy, unveiling a realm of possibilities for tailoring solutions to specific biomedical and environmental applications. The present review navigates through their antibacterial applications; from wound dressings to packaging materials with inherent antibacterial properties, the potential applications underscore the versatility and adaptability of these materials. Moreover, this comprehensive review serves as a valuable roadmap, guiding future research endeavors in reshaping the landscape of natural antibacterial materials on a global scale.

Preparation and Heavy Metal Adsorption Performance of 2-Aminopyridine-Modified Sodium Alginate/Polyacrylic Acid Hydrogel

This study utilized the Schiff base reaction as a chemical bonding method to successfully graft 2-aminopyridine onto oxidized sodium alginate, resulting in the formation of modified sodium alginate (OSM). Subsequently, the OSM/polyacrylic acid (OSM/PAA) hydrogel was synthesized via a thermally initiated free radical polymerization process and evaluated as an adsorbent for the removal of heavy metal ions from wastewater. Comprehensive characterization of the prepared samples was performed using FT-IR, SEM, and TGA. The influence of temperature, pH, adsorbent dosage, contact time, and heavy metal ion concentration on the adsorption capacity of the OSM/PAA adsorbent in simulated wastewater was thoroughly investigated. Additionally, a detailed analysis of the adsorption thermodynamics, kinetics, and mechanisms was conducted. Experimental results indicated that at 25 °C, pH 5.0, and an adsorbent dosage of 0.4 g/L, the maximum adsorption capacities of the OSM/PAA hydrogel for Cu(II), Zn(II), and Ni(II) were 367.64 mg/g, 398.4 mg/g, and 409.83 mg/g, respectively. These findings suggest that the adsorption of heavy metal ions by OSM/PAA is a spontaneous, heterogeneous chemical process with significant potential for practical applications in wastewater treatment.

Covalently crosslinked carboxymethyl chitosan beads containing SiO2 and ionic polymer for efficient adsorptive removal of methylene blue

The carboxymethyl chitosan (CMCS)-based porous beads are still criticized for their limited number of binding sites, which impairs their efficacy in removing aqueous pollutants. To overcome this challenge, this work introduces the production of covalently crosslinked CMCS-based beads containing SiO2 and poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS). The porous composite beads not only possess remarkable stability under acidic conditions, but also have abundant active binding sites for adsorption. By using methylene blue (MB) as a representative pollutant, adsorption experiments have demonstrated that the presence of SiO2 and PAMPS significantly enhances the adsorption performance of the CMCS-based beads. The adsorption behavior aligns with the pseudo-second-order kinetic model and the Langmuir isotherm model, indicating the occurrence of chemical adsorption and monolayer adsorption phenomena. The optimal sample, CCMCS-SiO2@PAMPS, exhibits a maximum adsorption capacity of 606.06, 649.35, and 684.93 mg g-1 at 25, 35, and 45 °C, respectively, as calculated from the Langmuir isotherm model. The effects of pH, ionic strength, and adsorbent dosage on adsorption performance are investigated, and the porous composite beads exhibit robust reusability, maintaining their efficiency even after four adsorption-desorption cycles. The significant findings of this research confirm the superior performance of the functionalized CMCS-based beads for the effective removal of organic dyes from aqueous environments.

Effect of modifications on structure, physicochemical properties and lead ions adsorption behavior of dietary fiber of Flammulina velutipes

The health effects of dietary fiber have been widely concerned, which are closely related to physicochemical properties. This study focused on soluble dietary fiber of Flammulina velutipes (FDF), evaluated the effects of modifications on structural characterization, the physicochemical properties and the heavy metal adsorption characteristics, and further clarified underlying mechanisms on Pb2+ adsorption behavior of FDFs. The results showed the modifications of extrusion and cellulase improved the yield of FDFs, increased the release of active groups and enhanced the adsorption ability in vitro. Besides, Pb2+ adsorption altered porous structure and led to the presence of carboxylate. It was a spontaneous endothermic reaction and can be fitted by the pseudo-second-order kinetic equation. The Freundlich equation was suitable to describe the adsorption isotherm. These results highlighted potential applications of the dietary fiber modification and laid the theoretical foundation for the modification processing of F. velutipes and protection from food-derived heavy metal toxicity.

Synergistic and simultaneous removal of heavy metal ions over waste bamboo shoot particles encapsulated carboxymethyl cellulose/gelatin composite hydrogel

Carboxymethyl cellulose (CMC) hydrogels are commonly used for heavy metal removal due to their abundant hydroxyl and carboxyl groups. However, pristine CMC hydrogels always suffer from low gel strength and limited adsorption properties in large-scale applications. In this study, to improve the gel strength and heavy metal ions removal capacity, fish gelatin and bamboo shoot particle (BSP) were introduced to CMC hydrogels, respectively. The formation of the composite hydrogel with enhanced gel strength was primarily driven by hydrogen bonding, which exhibited an increase strain resistance with a critical strain value up to 214.68 %. As expected, the composite hydrogel can effectively remove Cd2+, Hg2+, and Pb2+ from aqueous solutions simultaneously. The physical adsorption process of heavy metals by the composite hydrogel was well described by the pseudo-second-order kinetic model, while the Langmuir model indicated maximum adsorption capacities of 147.7 mg/g for Cd2+, 88.62 mg/g for Hg2+, and 163.89 mg/g for Pb2+. Notably, the composite hydrogel exhibited enhanced recyclability, maintaining its efficacy for up to at least five cycles. This study underscores the potential of using naturally occurring biodegradable materials for the removal of heavy metals, and paved ways for heavy metal removal at industrial levels.

Novel Ternary System for Electrochemiluminescence Biosensor and Application toward Pb2+ Assay

This study constructed an electrochemiluminescence (ECL) biosensor for ultrasensitive detection of Pb2+ in a ternary system by employing DNAzyme. The ternary system is composed of a potassium-neutralized perylene derivative (K4PTC) as the ECL emitter, K2S2O8 as the coreactant, and neodymium metal-organic frameworks (Nd-MOFs) as the coreaction accelerators. Nd-MOFs immobilize DNAzymes and enhance the luminescence intensity of the K4PTC/K2S2O8 system. As part of this system, K4PTC enhances the ECL signal in solution and supports Pb2+ detection. The sequence of ferrocene (Fc)-linked DNA (DNA-Fc) is catalytically cleaved by DNAzymes in the presence of Pb2+. This causes the removal of DNA1-Fc from the electrode surface to recover the ECL signal. As a result, the as-prepared ECL biosensor can quantify Pb2+ with a detection limit (LOD) of 4.1 fM in the range of 1 μM to 10 fM. The ECL biosensor displays high specificity, good stability, excellent reproducibility, and desirable practicality for Pb2+ detection in tap water. Moreover, by simply changing the sequence of the DNAzyme, new biosensors can be designed for ultrasensitive detection of different heavy metal ions, offering an excellent approach for monitoring water quality safety.

Exopolysaccharide-Producing Bacteria Regulate Soil Aggregates and Bacterial Communities to Inhibit the Uptake of Cadmium and Lead by Lettuce

The accumulation of heavy metals in the soil not only causes serious damage to the soil ecosystem, but also threatens human health through the food chain. Exopolysaccharides have the functions of adsorbing and chelating heavy metals and reducing their bioavailability in the soil. In our study, exopolysaccharide-producing bacteria with a high efficiency in adsorbing cadmium (Cd) and lead (Pb) were screened from heavy metal-contaminated farmland. Through pot experiments, the influence of functional strains on the size distribution, heavy metal content, and bacterial community structure of soil aggregates in lettuce was studied using high-throughput sequencing technology. The results show that 11 strains secreting exopolysaccharides were initially screened from heavy metal-contaminated soil. Among them, strain Z23 had a removal rate of 88.6% for Cd and 93.2% for Pb. The rate at which Cd was removed by strain Z39 was 92.3%, and the rate at which Pb was removed was 94.4%. Both strains belong to Bacillus sp. Strains Z23 and Z39 induced the formation of Fe2Pb(PO4)2, Cd2(PO4)2, and Pb2O3 in the solution. The pot experiments showed that strains Z23 and Z39 increased (19.1~23.9%) the dry weight and antioxidant enzyme activity of lettuce roots and leaves, while reducing (40.1~61.7%) the content of Cd and Pb. Strains Z23 and Z39 increased the proportion of microaggregates (<0.25 mm) and the content of exopolysaccharides in rhizosphere soil and reduced (38.4-59.7%) the contents of available Cd and Pb in microaggregates, thus inhibiting the absorption of heavy metals by lettuce. In addition, the exopolysaccharide content and the bacterial community associated with heavy metal resistance and nitrogen (N) cycling (Patescibacteria, Saccharimonadales, Microvirga, and Pseudomonas) in microaggregates were key factors affecting the available heavy metal content in soil. These results show that the exopolysaccharide-producing bacteria Z23 and Z39 reduced the absorption of Cd and Pb by lettuce tissues, thus providing strain resources for the safe utilization of soils that exceed heavy metal standards for farmland and for reducing the heavy metal content in vegetables.

Glutaraldehyde crosslinked ternary carboxymethylcellulose/polyvinyl alcohol/polyethyleneimine film with enhanced mechanical properties, water resistance, antibacterial activity, and UV-shielding ability without any UV absorbents

Despite the plethora of methods reported for fabricating ultraviolet (UV) shielding films using various UV absorbers to date, it remains a major challenge for the development of novel UV shielding films that simultaneously exhibit excellent transparency. In this work, a novel composite film (GA-x-CMC/PVA/PEI) is fabricated by integrating anionic carboxymethylcellulose (CMC), cationic polyethyleneimine (PEI), and polyvinyl alcohol (PVA) via electrostatic and hydrogen bond interactions and further cross-linking with glutaraldehyde (GA). Herein, PVA expands hydrogen bonding networks, reduces film haze, and enhances its mechanical strength. GA acts as a crosslinker in producing Schiff bases with PEI and acetals with CMC and PVA. The synthesized GA-x-CMC/PVA/PEI composite film possesses a notable amount of unsaturated -CH=N- bonds of Schiff base, resulting from the condensation of PEI and GA, which exhibit superior shielding efficiency against both UV-A and UV-B rays while maintaining exceptional transparency, visibility, and simultaneously enhancing mechanical properties and thermal stability. Notably, increasing the content of PEI leads to almost complete shielding of the entire UV spectrum (<400 nm) due to the increasing of the number of -CH=N- unsaturated bonds. Furthermore, the obtained film without any UV-shielding additives has exceptional mechanical properties, hydrophobicity, and antibacterial properties, rendering it a wide application prospect.

Drug delivery using reduction-responsive hydrogel based on carboxyethyl-succinoglycan with highly improved rheological, antibacterial, and antioxidant properties

The development of exopolysaccharide-based polymers is gaining increasing attention in various industrial biotechnology fields for materials such as thickeners, texture modifiers, anti-freeze agents, antioxidants, and antibacterial agents. High-viscosity carboxyethyl-succinoglycan (CE-SG) was directly synthesized from succinoglycan (SG) isolated from Sinorhizobium meliloti Rm 1021, and its structural, rheological, and physiological properties were investigated. The viscosity of CE-SG gradually increased in proportion to the degree of carboxyethylation substitution. In particular, when the molar ratio of SG and 3-chloropropionic acid was 1:100, the viscosity was significantly improved by 21.18 times at a shear rate of 10 s-1. Increased carboxyethylation of SG also improved the thermal stability of CE-SG. Furthermore, the CE-SG solution showed 90.18 and 91.78 % antibacterial effects against Escherichia coli and Staphylococcus aureus and effective antioxidant activity against DPPH and hydroxyl radicals. In particular, CE-SG hydrogels coordinated with Fe3+ ions, which improved both viscosity and rheological properties, while also exhibiting reduction-responsive drug release through 1,4-dithiothreitol. The results of this study suggest that SG derivatives, such as CE-SG, can be used as functional biomaterials in various fields such as food, cosmetics, and pharmaceutical industries.

Novel amino-ethyl carboxymethyl cellulose crosslinked ampholyte hydrogel development for Methyl orange removal from waste water

In the modern era, with the rapid growth of various industries, the issues of energy crisis and environmental pollution have garnered increasing attention. One significant source of industrial pollution is printing and dyeing wastewater. This wastewater often contains dyes that have aromatic structures and azo groups, such as Methyl orange (MO), which are both toxic and difficult to degrade. If these dyes are released into the wastewater stream without any treatment, they can have adverse effects on ecological balance and human health. Therefore, it is crucial to identify suitable treatment strategies to efficiently remove dyes from wastewater systems before discharge. In this study, the Methyl orange (MO) azo dye has been removed from dyes-contaminated wastewater, for the first time, using a novel amino-ethyl carboxymethyl cellulose crosslinked ampholyte hydrogel (AECMC). Different characterization methods, including FTIR, TGA, and DSC were used to characterize the generated AECMC compounds. The water absorption and cationic exchange capacities were assessed. Factors affecting the MO anions adsorption including MO concentration, adsorption pH, temperature, time, adsorbent dose, and agitation speed have been investigated. Moreover, the kinetics of the adsorption process was assessed by the use of three models: pseudo-first-order, Pseudo-second-order, and Elovich. Moreover, the mechanism of the adsorption process was monitored using the Intraparticle diffusion and Boyd models. Additionally, the adsorption isotherm was examined using established models such as Langmuir, Freundlich, and Temkin isotherms. The thermodynamic characteristics of the MO adsorption process have been investigated at various adsorption temperatures using the Van't Hoff model. The results obtained from the study indicate that the process of MO adsorption adhered to the Pseudo-second-order kinetic model, the Langmuir isotherm model was found to be applicable, and spontaneous and exhibited an endothermic character. In conclusion, the developed novel amino-ethyl carboxymethyl cellulose crosslinked ampholyte hydrogels (AECMC) have successive in the removal of the MO anionic dye from contaminated wastewater.

The relationship between polysaccharide structure and its antioxidant activity needs to be systematically elucidated

Polysaccharides have a wide range of applications due to their excellent antioxidant activity. However, the low purity and unclear structure of polysaccharides have led some researchers to be skeptical about the antioxidant activity of polysaccharides. The current reports on the structure-activity relationship of polysaccharides are sporadic, so there is an urgent need to systematically summarize the antioxidant effects of polysaccharides with clear structures and the relationships between the structures to provide a scientific basis for the development and application of polysaccharides. This paper will systematically elucidate the structure-activity relationship of antioxidant polysaccharides, including the molecular weight, monosaccharide composition, glycosidic linkage, degree of branching, advanced conformation and chemical modification. For the first time, the antioxidant activity of polysaccharides is related to their chemical structure through histogram and radar map, and further studies using principal component analysis and cluster analysis. We critically discussed how the source, chemical structure and chemically modified groups of polysaccharides significantly contribute to their antioxidant activity and summarized the current research status and shortcomings of the structure-activity relationship of antioxidant polysaccharides. This review provides a theoretical basis and new perspective for further research on the structure-activity relationship of antioxidant polysaccharides and the development of natural antioxidants.

Influences of carboxymethyl chitosan upon stabilization and gelation of O/W Pickering emulsions in the presence of inorganic salts

The objective of this study was to investigate the effects of carboxymethyl chitosan (CMCS) on the stabilization and gelation of oil-in-water (O/W) Pickering emulsions (PEs) with polyphenol-amino acid particles in the presence of inorganic salts. The results revealed that the CMCS-induced depletion interactions contributed to improving the emulsification ability and interfacial adsorption efficiency of polyphenol-amino acid particles as well as constructing the network structures in the continuous phase. These relevant changes collectively resulted in elevating stability, viscosity and moduli of PEs. The additional effects of different inorganic salts with varying additions were further investigated, and the addition-dependent phenomena were observed. At low additions of inorganic salts, the occurrence of the chelation of inorganic salts with CMCS consolidated the constructed network structure, favorable to the gelation of PEs. With increasing additions, this chelation effect became stronger which compromised the CMCS-induced depletion, gradually leading to destabilization of PEs. In terms of ion species, the more pronounced effect on emulsion stability was achieved with calcium ions than with potassium and iron ions. This study expects to provide a new perspective on the extending application of cationic CMCS for improving the stability of O/W PEs in the food industry.

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.

Powdered silk: A promising biopolymer for the treatment of dye contaminated water

Discharge of textile dye effluents into water bodies is creating stress to aquatic life and contaminating water resources. In this study, a new biopolymer adsorbent silk fibroin (SF) was prepared from Bombyx mori silk fibroin (SF) and used for removal of Solochrome Black-T (SB-T) from water. This innovative adsorbent exhibits an exceptional adsorption capacity of 20.08 mg/g, achieving a removal efficiency of approximately 98.6 % within 60 min. Notably, the powdered SF adsorbent demonstrates rapid kinetics, surpassing the performance of previously reported similar adsorbents in adsorption capacity and reaction speed. The molecular weight and particle diameter of the material were observed to be > 1.243 kDa and 3 μm, respectively. The experimental investigations were performed on different parameters, viz., adsorbent dosage, contact time, repeatability, and desorption-adsorption study. The experimental data well fit for the Langmuir model (R2 = 0.937, qmax = 20.08 mg/g) and the pseudo-second-order kinetics (R2 = 0.921 and qe = 1.496 mg/g). Compared to the adsorbents reported in the literature, the newly prepared SF showed high adsorption capacity and faster kinetics to address real-life situations. The novelty of this work extends beyond its remarkable adsorption capabilities. The SF adsorbent offers a cost-effective, sustainable solution and regenerable adsorption material with minimal negative environmental impacts. This regenerability, with its versatility and broad applicability, positions powdered SF fibroin as a transformative technology in water treatment and environmental protection.

Efficient photocatalytic remediation of lerui acid brilliant blue dye using radiation- prepared carboxymethyl cellulose/acrylic acid hydrogel supported by ZnO@Ag

Organic dye pollution from textiles and other industries presents a substantial risk to people and aquatic life. The use of photocatalysis to decolorize water using the strength of UV light is one of the most important remediation techniques. In the present study, a novel nanocomposites hydrogel including carboxymethyl cellulose (CMC), acrylic acid (AAc), Zinc oxide (ZnO), and silver (Ag) nanoparticles was produced using an eco-friendly γ-irradiation technique for photocatalytic decolorization applications. ZnO and Ag nanoparticles were distributed in the CMC/AAc hydrogel matrix without significant aggregation. SEM, XRD, EDX, TEM, and FTIR analyses were used to assess the physicochemical characteristics of the nanocomposite samples. Carboxymethyl cellulose/acrylic acid/Zinc oxide doped silver (CMC/PAAc/ZnO@Ag) nanocomposite hydrogels were developed and utilized in the photocatalytic decolorization of the lerui acid brilliant blue dye (LABB) when exposed to ultraviolet (UV) radiation. UV- Vis spectrophotometry was utilized to analyze the optical properties of the produced nanostructure. Regarding the decolorization of the LABB, the impacts of operational variables were investigated. The optimum conditions for decolorization (93 %) were an initial concentration of 50 mg/L, pH = 4, catalyst dosage of 50 g/L, and exposure time of 90 min. The results illustrated that the LABB acidic dye from wastewater was remarkably decolored.

Structurally Modified Polysaccharides: Physicochemical Properties, Biological Activities, Structure-Activity Relationship, and Applications

Polysaccharides are an important class of biomolecules derived from several sources. However, the inherent structure of polysaccharides prevents them from exhibiting favorable physicochemical properties, which restricts their development in agriculture, industry, food, and biomedicine. This paper systematically summarizes the changes in the primary and advanced structures of modified polysaccharides, and focuses on the effects of various modification methods on the hydrophobicity, rheological properties, emulsifying properties, antioxidant activity, hypoglycemic, and hypolipidemic activities of polysaccharides. Then there is a list the applications of modified polysaccharides in treating heavy metal pollutants, purifying water resources, improving beverage stability and bread quality, and precisely delivering the drug. When summarized and reviewed, the information above can shed further light on the relationship between polysaccharide structure and function. Determining the structure-activity relationship provides a scientific basis for the direction of molecular modifications of polysaccharides.

Dielectric Barrier Discharge Plasma-Assisted Preparation of Chitosan-Based Hydrogels

Chitosan is widely used in the production of various hydrogels due to its non-biological toxicity, good biocompatibility, and strong biodegradability. However, chitosan-based hydrogels have not been widely used in tissue engineering due to their poor mechanical strength, poor stability and high biotoxicity of cross-linking agents. As a green technology, low temperature plasma is rich in active groups that can be involved in various chemical reactions, such as replacing the components on the chitosan chain, contributing to the cross-linking of chitosan. In this study, a plasma-assisted preparation method of chitosan-based hydrogels was developed and the properties, including mechanics, water absorption, and degradation (or stability), were characterized and analyzed. It is proved that plasma treatment plays a significant role in improving the mechanical strength and stability of hydrogels.

Purslane (Portulacae oleracea L.) polysaccharide relieves cadmium-induced colonic impairments by restricting Cd accumulation and inhibiting inflammatory responses

This study aimed to assess the protective effects of purslane polysaccharide (PP) on colonic impairments in mice exposed to cadmium (Cd). C57BL/6 mice were administered with PP (200-800 mg/kg/day) by gavage for 4 weeks after treatment with 100 mg·L-1 CdCl2. PP significantly reduced Cd accumulation in the colon tissue and promoted the excretion of Cd in the feces. PP could reduce the expression levels of inflammatory factors (tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-6) and inhibit the activation of the TLR4/MyD88/NF-κB signaling pathway. In addition, the results of 16S rRNA analysis revealed that PP significantly increased the abundance of probiotics (Lactobacillus), while decreased the abundance of pathogenic bacteria (Lachnospiraceae_NK4A136_group). Following the augmentation of beneficial intestinal bacteria, the treatment with PP led to an increase in the levels of intestinal microbial metabolites, specifically short-chain fatty acids (SCFAs). The SCFAs are known for their anti-inflammatory properties, immune-regulatory effects, and promotion of intestinal barrier function. Additionally, the results suggested that PP effectively impeded the enterohepatic circulation by inhibiting the FXR-FGF15 axis in the intestines of Cd-exposed mice. In summary, PP mitigated the toxic effects of Cd by limiting its accumulation and suppressing inflammatory responses in colon.

Evaluation of heavy metal removal and antibiofilm efficiency of biologically synthesized chitosan- silver Nano-bio composite by a soil actinobacterium Glutamicibacter uratoxydans VRAK 24

Biological synthesis of nanoparticles is cost-effective as well as safer than physical and chemical methods. This study focuses on the biological synthesis of silver nanoparticles using Glutamicibacter uratoxydans which remains still unexplored. The synthesized silver nanoparticles are encapsulated with chitosan to prepare nanobiocomposite. Actinobacteria were isolated from mesophilic soil and screened for heavy metal resistance. The potent heavy metal resistant isolate was identified by 16SrRNA sequencing and used for the biological synthesis of silver particles. The characterization of chitosan- silver nano-bio composite was carried out by UV-Vis spectroscopy, FTIR spectroscopy, and XRD. Morphology was analyzed by scanning electron microscopy. The particle size and stability were studied using Dynamic light scattering and Zeta potential analysis. The nano-bio composite was tested for lead removal efficiency and antibiofilm activity. The potent isolate was identified as Glutamicibacter uratoxydans and it was named as Glutamicibacter uratoxydans VRAK 24. The UV spectra showed maximum absorbance at 410 nm. The FTIR spectra and XRD confirmed chitosan encapsulation with silver nanoparticle. The size of nanobiocomposite was found to be 0.376. The stability of nanobiocomposite recorded a zeta potential value of -5.37 mV. The lead removal efficiency was found to be 87.69 %. In addition, the nanobiocomposite exhibited highest anti-biofilm activity against S.aureus when compared to E.coli. The research findings, concluded that the synthesized nanobiocomposite showed better anti-biofilm activity. Also, nanobiocomposite was found to be a good adsorbent for the removal of heavy metal lead.

Solvent-less carboxymethylation-induced electrostatic crosslinking of chitosan

The successful N-carboxymethylation and concomitant crosslinking of solid chitosan upon heating its mixture with solid monochloroacetic acid, without the use of solvents or catalysts, is reported. The N-carboxymethylation was confirmed through the analysis of the partially depolymerized product using NMR spectroscopy, as well as a control reaction with lysine. This transformation was facilitated by the nucleophilic nature of the free amine group in the repeating unit of chitosan, which possesses lone pair of electrons capable of attacking the carbon center bearing the leaving group and displacing the leaving group in a concerted manner. The crosslinking, on the other hand, was established by the observed insolubility in aqueous acidic solutions, even when subjected to prolonged heating at 60 °C. This crosslinking occurs due to the electrostatic interactions between the carboxylate groups and the adjacent ammonium groups, as supported by evidence from FTIR spectroscopy and a control reaction involving ethyl chloroacetate. The resulting crosslinked carboxymethyl chitosan demonstrated its usefulness in the adsorption of methyl orange and fluorescein, as well as functioning as an organic catalyst for aza-Michael addition, Hantzsch reaction, and substituted perimidine synthesis.

Label free electrochemical sensors for Pb(II) detection based on hemicellulose extracted from Opuntia Ficus Indica cactus

We aim to develop an electrochemical sensor for a divalent metal ion (lead II), a highly toxic water contaminant. We explore a sensor formed with a hemicellulose polysaccharide extracted from the Opuntia Ficus Indica cactus associated with agarose as a sensitive layer deposited on a gold electrode. This sensor combines the functional groups of hemicellulose that could form a complex with metal ions and agarose with gelling properties to form a stable membrane. The sensor demonstrated a loading ability of Pb2+, with higher affinity compared to other metal ions such as Hg2+, Ni2+, and Cu2+, thanks to the chemical structure of hemicellulose. The detection was measured by square wave voltammetry based on a well-defined redox peak of the metal ions. The sensor shows high sensitivity towards Pb2+ with a detection limit of 1.3 fM. The application in river and sea water using the standard addition method for lead detection was studied.

Green hydrophobic maltodextrin nanosponges for magnetic solid-phase extraction of hypothalamic peptides from plasma samples

In this work, for the first time, magnetic-phthalated maltodextrin nanosponges (M-PAMDNSs) were synthetized and introduced as efficient and green sorbents. The integration of phthaloyl groups as hydrophobic moieties into networks of maltodextrin nanosponges provided good enrichment for hypothalamic-related peptides (HRPs). The synthesized materials were characterized by 1H nuclear magnetic resonance spectroscopy, water contact angle, attenuated total reflection-Fourier transform infrared spectroscopy, dynamic light scattering, zeta potential, pH point of zero charge, acid-base titration, field-emission scanning electron microscopy, Brunauer-Emmett-Teller, and vibrating sample magnetometer. Under the optimized conditions (sorbent amount: 5.0 mg, desorption solvent volume and type: 300 µL of methanol: H2O: trifluoroacetic acid, extraction time: 15 min, and desorption time: 10 min), the developed magnetic solid-phase extraction (MSPE) method in combination with HPLC-UV was used as a novel and sensitive analytical method for the determination of HRPs in plasma samples. The proposed MSPE-HPLC-UV method provided good linearity (1.5-500 ng mL-1 R2 ≥ 0.9988), low limits of detection (0.1-0.2 ng mL-1) and quantification (0.4-0.8 ng mL-1), desirable precision (RSD ≤ 8.8%, n ₌ 5), satisfactory enrichment factor (EFs ≥ 66.0), and well relative recoveries (92.8-108.8%). Overall, the established method effectively expanded the analytical potential of MSPE approach for the quantification of HRPs in biological samples.

Application of cellulose to chromatographic media: Cellulose dissolution, and media fabrication and derivatization

As the cornerstone of chromatographic technology, the development of high-performance chromatographic media is a crucial means to enhance the purification efficiency of biological macromolecules. Cellulose is a popular biological separation medium due to its abundant hydroxyl group on the surface, easy modification and, weak non-specific adsorption. In this paper, the development of cellulosic solvent systems, typical preparation methods of cellulosic chromatographic media, and the enhancement of chromatographic properties of cellulosic chromatographic media by polymeric ligand grafting strategies and their mechanism of action are reviewed. Ultimately, based on the current research status, a promising outlook for the preparation of high-performance cellulose-based chromatographic media was presented.

Customizing Starch Properties: A Review of Starch Modifications and Their Applications

Starch has been a convenient, economically important polymer with substantial applications in the food and processing industry. However, native starches present restricted applications, which hinder their industrial usage. Therefore, modification of starch is carried out to augment the positive characteristics and eliminate the limitations of the native starches. Modifications of starch can result in generating novel polymers with numerous functional and value-added properties that suit the needs of the industry. Here, we summarize the possible starch modifications in planta and outside the plant system (physical, chemical, and enzymatic) and their corresponding applications. In addition, this review will highlight the implications of each starch property adjustment.

The antioxidant activity of polysaccharides: A structure-function relationship overview

Over the last years, polysaccharides have been linked to antioxidant effects using both in vitro chemical and biological models. The reported structures, claimed to act as antioxidants, comprise chitosan, pectic polysaccharides, glucans, mannoproteins, alginates, fucoidans, and many others of all type of biological sources. The structural features linked to the antioxidant action include the polysaccharide charge, molecular weight, and the occurrence of non-carbohydrate substituents. The establishment of structure/function relationships can be, however, biased by secondary phenomena that tailor polysaccharides behavior in antioxidant systems. In this sense, this review confronts some basic concepts of polysaccharides chemistry with the current claim of carbohydrates as antioxidants. It critically discusses how the fine structure and properties of polysaccharides can define polysaccharides as antioxidants. Polysaccharides antioxidant action is highly dependent on their solubility, sugar ring structure, molecular weight, occurrence of positive or negatively charged groups, protein moieties and covalently linked phenolic compounds. However, the occurrence of phenolic compounds and protein as contaminants leads to misleading results in methodologies often used for screening and characterization purposes, as well as in vivo models. Despite falling in the concept of antioxidants, the role of polysaccharides must be well defined according with the matrices where they are involved.

Starch-Based Polymer Materials as Advanced Adsorbents for Sustainable Water Treatment: Current Status, Challenges, and Future Perspectives

Over the past three decades, chemical and biological water contamination has become a major concern, particularly in the industrialized world. Heavy metals, aromatic compounds, and dyes are among the harmful substances that contribute to water pollution, which jeopardies the human health. For this reason, it is of the utmost importance to locate methods for the cleanup of wastewater that are not genuinely effective. Owing to its non-toxicity, biodegradability, and biocompatibility, starch is a naturally occurring polysaccharide that scientists are looking into as a possible environmentally friendly material for sustainable water remediation. Starch could exhibit significant adsorption capabilities towards pollutants with the substitution of amide, amino, carboxyl, and other functional groups for hydroxyl groups. Starch derivatives may effectively remove contaminants such as oil, organic solvents, pesticides, heavy metals, dyes, and pharmaceutical pollutants by employing adsorption techniques at a rate greater than 90%. The maximal adsorption capacities of starch-based adsorbents for oil and organic solvents, pesticides, heavy metal ions, dyes, and pharmaceuticals are 13,000, 66, 2000, 25,000, and 782 mg/g, respectively. Although starch-based adsorbents have demonstrated a promising future for environmental wastewater treatment, additional research is required to optimize the technique before the starch-based adsorbent can be used in large-scale in situ wastewater treatment.

Green synthesis of nano silver-embedded carboxymethyl starch waste/poly vinyl alcohol hydrogel with photothermal sterilization and pH-responsive behavior

Bacterial wound infections remain a significant health issue of great concern. Hence, there is a need to develop a novel material with antibacterial properties and smart functions. In this study, the effects of silver nanoparticles content (AgNPs) on properties of photothermal and pH-responsive nanocomposite hydrogels were investigated. The nanocomposite hydrogel samples were prepared using cassava starch waste modified by carboxymethylation (CMS), and mixed with poly vinly alcohol (PVA) and tannic acid (TA). The presence of AgNPs in the hydrogel samples enhanced antibacterial activities and photothermal conversion ability. The use of as-prepared hydrogel using 200 mM silver nitrate (H-AgNPs-200) combined with near infrared (NIR) radiation produced 100 % antibacterial efficiency for Escherichia coli (E.coli) and 98.2 % for Staphylococcus aureus (S.aureus). Furthermore, the H-AgNPs-200 also provided the highest storage modulus at 87.9 kPa. The obtained nanocomposite hydrogel was shown to exhibit pH-responsive release of TA. Under NIR radiation, higher release of TA at different pH was observed. The cytotoxicity study indicated that the nanocomposite hydrogels had good biocompatibility. Hence, the development of nanocomposite hydrogel-based CMS from cassava starch waste/PVA/AgNPs is a promising and sustainable approach where agro-waste product is used as the base material for medical application in wound dressing.

Antioxidant and DNA protecting activity of carboxymethylated polysaccharides from Cortex periplocae

In this study, polysaccharide from Cortex periplocae (CPP) was modified and three carboxymethylation modification polysaccharides (CPPCs) were obtained, and their physicochemical characteristics and in vitro biological activities were investigated. Based on the ultraviolet-visible (UV-Vis) scan, CPPs (CPP and CPPCs) did not contain nucleic acids or proteins. However, the Fourier transform infrared (FTIR) spectrum showed a new absorption peak around 1731 cm^-1. In addition, three absorption peaks near 1606, 1421, and 1326 cm^-1 were enhanced after carboxymethylation modification. Based on UV-Vis scan, the maximum absorption wavelength of Congo Red + CPPs exhibited a red-shift compared to Congo Red meant CPPs had a triple helix conformation. Scanning electron microscopy (SEM) indicated that CPPCs exhibited more fragments and non-uniform-sized filiform than CPP. Thermal analysis showed that CPPCs degraded between the temperature 240 °C-350 °C and CPP in the 270 °C-350 °C. In addition, the antioxidant and DNA protecting activities of CPPCs were significantly enhanced compared to CPP. Overall, this study demonstrated the potential applications of CPPs in food and pharmaceutical industries.

Polysaccharide-based biopolymer hydrogels for heavy metal detection and adsorption

BACKGROUND

With rapid development in agriculture and industry, water polluted with heavy metallic ions has come to be a serious problem. Adsorption-based methods are simple, efficient, and broadly used to eliminate heavy metals. Conventional adsorption materials have the problems of secondary environmental contamination. Hydrogels are considered effective adsorbents, and those prepared from biopolymers are biocompatible, biodegradable, non-toxic, safe to handle, and increasingly used to adsorb heavy metal ions.

AIM OF REVIEW

The natural origin and easy degradability of biopolymer hydrogels make them potential for development in environmental remediation. Its water absorption capacity enables it to efficiently adsorb various pollutants in the aqueous environment, and its internal pore channels increase the specific surface area for adsorption, which can provide abundant active binding sites for heavy metal ions through chemical modification.

KEY SCIENTIFIC CONCEPT OF REVIEW

As the most representative of biopolymer hydrogels, polysaccharide-based hydrogels are diverse, physically and chemically stable, and can undergo complex chemical modifications to enhance their performance, thus exhibiting superior ability to remove contaminants. This review summarizes the preparation methods of hydrogels, followed by a discussion of the main categories and applications of polysaccharide-based biopolymer hydrogels.

Divalent metal ion removal from simulated water using sustainable starch aerogels: Effect of crosslinking agent concentration and sorption conditions

This paper evaluates corn starch aerogels, studying different crosslinking agent (trisodium citrate) concentrations (1:1, 1:1.5, and 1:2) and sorption conditions (contact time, adsorbent weight, and initial concentration) regarding the potentially toxic elements (PTEs) [Cd(II) or Zn(II)] adsorption of the aqueous systems. Besides, other properties of aerogels, such as structural properties, specific surface area, and mechanical performance, were evaluated. For adsorption results, better values were observed in adsorption capacity and efficiency for the initial concentration of 100 ppm. In addition, an adsorption time of 12 h and an adsorbent weight of 3.0 g obtained better results due to the possible balance in this time and the high specific surface area available for Cd(II) adsorption. As for the type of adsorbent, the Aero 1:1.5 sample (intermediate crosslinking agent concentration) obtained better results, possibly due to the high porosity, smaller pore sizes, high pore density, and high specific surface area (198 m²·g^-1). In addition, hydroxyl groups in the starch aerogel removed Cd(II) ions with 30 % adsorption efficiency. Lastly, Aero 1:1.5 obtained a high mechanical strength at compression and a satisfactory compressive modulus. In contrast, starch aerogels did not absorb the Zn(II) ion.

Does the presence of heavy metal and catechol contaminants in organic waste challenge the physiological performance of the bioconverter Hermetia illucens?

The increased human activities and the worldwide population growth are constantly increasing the production of solid wastes. Over the years, waste management has thus become a prominent issue for several companies and municipalities, and several engineering techniques have been developed over the years in order to convert wastes into other solid materials or fuels. Yet, several techniques are important contributors to environmental pollution, and biological-based solutions have thus become progressively very popular. In particular, insect-based conversion of organic wastes represent eco-friendly tools, and the growth and development of insect species such as the black soldier fly have been tested and improved for a large diversity of organic wastes. However, organic wastes, including food wastes, may contain several pollutants such as heavy metals and catechol which could affect the bioconversion efficiency by incurring physiological costs that would be undetectable at the organismal level, i.e. have null to little effects on the life cycle of Hermetia illucens. In this context, assessments of antioxidant capacities can provide a rapid and low-cost evaluation of the capability of insects to handle exposure to heavy metals and catechol. Here, we aimed at measuring the physiological responses of the black soldier fly H. illucens grown on food wastes (kitchen, fruit or vegetable wastes) contaminated by cadmium, iron, lead or catechol. Biomarkers of oxidative stress (concentrations of hydrogen peroxide and protein carbonyls), non-enzymatic total antioxidant capacity (ascorbic acid amounts) and activity of enzymatic antioxidants (activities of superoxide dismutase and polyphenoloxidase) were measured from the gut of the larvae. We found no evidence of deleterious impacts of food waste contamination by catechol or heavy metals on H. illucens. In most experimental treatments, the array of physiological endpoints we measured for evaluating the degree of oxidative stress experienced by the larvae remained similar to controls. Possible physiological effects were reported for cadmium and catechol only, which tended to increase the oxidation of proteins and hydrogen peroxide in the larvae. Finally, our results suggested that the nature of the food waste could equally affect the physiological responses of the insect.

Synthesis of Hydrogels and Their Progress in Environmental Remediation and Antimicrobial Application

As a kind of efficient adsorptive material, hydrogel has a wide application prospect within different fields, owing to its unique 3D network structures composed of polymers. In this paper, different synthetic strategies, crosslinking methods and their corresponding limitations and outstanding contributions of applications in the fields of removing environmental pollutants are reviewed to further provide a prospective view of their applications in water resources sustainability. Furthermore, the applications within the biomedical field, especially in wound dressing, are also reviewed in this paper, mainly due to their unique water retention ability, antibacterial ability, and good biocompatibility. Finally, the development direction of hydrogels in the fields of environmental remediation and biomedicine were summarized and prospected.

Low-temperature aerobic carbonization and activation of cellulosic materials for Pb2+ removal in water source

Targeting the removal of Pb²⁺ in wastewater, cellulosic materials were carbonized in an aerobic environment and activated via ion exchange. The maximum adsorption capacity reached 243.5 mg/g on an MCC-derived adsorbent activated with sodium acetate. The modified porous properties improved the adsorption capacity. The capacity could be completely recovered five times through elution with EDTA. Because of the negative effects of Ni, Mg, and Ca elements, the adsorption capacities of activated carbonized natural materials were lower than that of pure cellulose. N₂ adsorption measurement showed that the adsorbent had a large specific surface area as well as abundant micropores and 4-nm-sized mesopores. FTIR and surface potential results proved that carboxyl group was generated in the aerobic carbonization, and was deprotonated during ion exchange. This adsorbent consisted of C-C bonds as the building blocks and hydrophilic groups on the surface. XPS results demonstrated that the Pb 4f binding energies were reduced by 0.7-0.8 eV due to the interaction between Pb²⁺ and the activated adsorbent, indicating that the carboxylate groups bonded with Pb²⁺ through coordination interactions. Pseudo-second-order and Elovich kinetic models were well fitted with the adsorption processes on the pristine and activated carbonized adsorbents, indicative of chemisorption on heterogeneous surfaces. The Freundlich expression agreed well with the data measured, and the pristine and activated adsorbents had weak and strong affinities for Pb²⁺, respectively. The Pb²⁺ adsorption process was exothermic and spontaneous, and heat release determined the spontaneity. The adsorption capacity is attributed to the carboxylate groups and pores generated in the aerobic oxidation and ion exchange procedures.

Hydrogel Beads of Amidoximated Starch and Chitosan as Efficient Sorbents for Inorganic and Organic Compounds

The synthesis of hydrogel beads involving natural polymers is, nowadays, a leading research area. Among natural polymers, starch and chitosan represent two biomolecules with proof of efficiency and low economic impact in various utilization fields. Therefore, herein, the features of hydrogel beads obtained from chitosan and three sorts of starch (potato, wheat and rise starches), grafted with acrylonitrile and then amidoximated, were deeply investigated for their use as sorbents for heavy metal ions and dyes. The hydrogel beads were prepared by ionotropic gelation/covalent cross-linking of chitosan and functionalized starches. The chemical structure of the hydrogel beads was analyzed by FT-IR spectroscopy; their morphology was revealed by optical and scanning electron microscopies, while the influence of the starch functionalization strategies on the crystallinity changes was evaluated by X-ray diffraction. Molecular dynamics simulations were used to reveal the influence of the grafting reactions and grafted structure on the starch conformation in solution and their interactions with chitosan. The sorption capacity of the hydrogel beads was tested in batch experiments, as a function of the beads’ features (synthesis protocol, starch sort) and simulated polluted water, which included heavy metal ions (Cu²⁺, Co²⁺, Ni²⁺ and Zn²⁺) and small organic molecules (Direct Blue 15 and Congo red).

The Adsorption of Heavy Metal Ions by Poly (Amidoamine) Dendrimer-Functionalized Nanomaterials: A Review

Rapid industrialization has resulted in serious heavy metal pollution. The removal of heavy metal ions from solutions is very important for environmental safety and human health. Poly (amidoamine) (PAMAM) dendrimers are artificial macromolecular materials with unique physical and chemical properties. Abundant amide bonds and amino functional groups provide them with a high affinity for heavy metal ions. Herein, PAMAM-functionalized adsorbents are reviewed in terms of different nanomaterial substrates. Approaches in which PAMAM is grafted onto the surfaces of substrates are described in detail. The adsorption isotherms and kinetics of these adsorbents are also discussed. The effects of PAMAM generation, pH, adsorbent dosage, adsorption time, thermodynamics, and ionic strength on adsorption performance are summarized. Adsorption mechanisms and the further functionalization of PAMAM-grafted adsorbents are reviewed. In addition to the positive results, existing problems are also put forward in order to provide a reference for the optimization of PAMAM-grafted adsorbents of heavy metal ions.

Hydrogel Adsorbents for the Removal of Hazardous Pollutants—Requirements and Available Functions as Adsorbent

Over the last few decades, various adsorption functions of polymer hydrogels for the removal of hazardous pollutants have been developed. The performance of hydrogel adsorbents depends on the constituents of the gels and the functions produced by the polymer networks of the gels. Research on hydrogels utilizing the characteristic functions of polymer networks has increased over the last decade. The functions of polymer networks are key to the development of advanced adsorbents for the removal of various pollutants. No review has discussed hydrogel adsorbents from the perspective of the roles and functions of polymer networks in hydrogels. This paper briefly reviews the basic requirements of adsorbents and the general characteristics of hydrogels as adsorbents. Thereafter, hydrogels are reviewed on the basis of the roles and functions of the polymer networks in them for the removal of hazardous pollutants by introducing studies published over the last decade. The application of hydrogels as adsorbents for the removal of hazardous pollutants is discussed as well.

The Use of Chitosan and Starch-Based Flocculants for Filter Backwash Water Treatment

Inorganic aluminum or iron salts supported with synthetic polymers are commonly used to eradicate colloidal particles from water in coagulation and flocculation processes. Nevertheless, these agents have several disadvantages, such as large volumes of sludge produced or environmental toxicity. Recently biodegradable polymers have been suggested as eco-friendly flocculants for water treatment. This study aimed to investigate the possibilities of using starch and chitosan and their oxidized derivatives as flocculants for filter backwash water treatment. Dialdehyde starch (DST) and dialdehyde chitosan (DCT) were synthesized by periodate oxidization of natural starch from corn and low molecular weight chitosan. The obtained materials have been characterized with scanning electron microscopy (SEM), ATR-FTIR spectroscopy, and thermogravimetric analysis (TGA). Furthermore, we studied the flocculation properties of polysaccharide flocculants in a series of jar tests. The effectiveness of chitosan and starched-based flocculants was compared to synthetic polymers commonly used to treat iron ions-rich filter backwash water. The environmental aspects of these chemicals, particularly the biodegradability of post-flocculation residues, were also addressed. It was found that oxidized starch and chitosan derivatives can be used as ecological flocculating materials to treat potable water or sludge.

Nanoarchitectonics for High Adsorption Capacity Carboxymethyl Cellulose Nanofibrils-Based Adsorbents for Efficient Cu2+ Removal

In the present study, carboxymethyl cellulose nanofibrils (CMCNFs) with different carboxyl content (0.99-2.01 mmol/g) were prepared via controlling the ratio of monochloroacetic acid (MCA) and sodium hydroxide to Eucalyptus bleached pulp (EBP). CMCFs-PEI aerogels were obtained using the crosslinking reaction of polyethyleneimine (PEI) and CMCNFs with the aid of glutaraldehyde (GA). The effects of pH, contact time, temperature, and initial Cu2+ concentration on the Cu2+ removal performance of CMCNFs-PEI aerogels was highlighted. Experimental data showed that the maximum adsorption capacity of CMCNF30-PEI for Cu2+ was 380.03 ± 23 mg/g, and the adsorption results were consistent with Langmuir isotherm (R2 > 0.99). The theoretical maximum adsorption capacity was 616.48 mg/g. After being treated with 0.05 M EDTA solution, the aerogel retained an 85% removal performance after three adsorption-desorption cycles. X-ray photoelectron spectroscopy (XPS) results demonstrated that complexation was the main Cu2+ adsorption mechanism. The excellent Cu2+ adsorption capacity of CMCNFs-PEI aerogels provided another avenue for the utilization of cellulose nanofibrils in the wastewater treatment field.

Fluorescence response mechanism of green synthetic carboxymethyl chitosan-Eu3+ aerogel to acidic gases

Industrial waste acidic gases are huge hazards to the environment and human health, so a material that can detect and remove them is needed. In this paper, CM chitosan-Eu³⁺ fluorescence aerogel was prepared via a green method by combining the carboxymethyl chitosan biomass polymer with Eu³⁺ ions, the structure and properties of this aerogel were characterized by SEM, TG, and stress-strain curves. The coordination of Eu³⁺ ions and carboxymethyl chitosan was analyzed with XPS and the difference in luminescence intensity of aerogel prepared at different pH values was analyzed. The monitoring of the aerogels revealed different responses to different acidic gases, and the fluorescence intensity of the aerogel showed a linear decrease with the adsorbed hydrogen chloride gas (HCl), while acetic acid gas (HAc) enhanced fluorescence. The adsorption system of the CM chitosan-Eu³⁺ aerogel was simulated using pseudo-second-order kinetics, which showed that the maximum adsorption capacity of HCl is 9.16 mmol/g. The different response mechanisms of HCl and HAc gas were analyzed with FT-IR, fluorescence lifetime imaging and Judd-Ofelt theory. This fluorescence aerogel was found to have potential applications in ensuring industrial production safety.