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Chitosan was commonly used with inorganic salt and organic compounds to prepare adsorption material for water treatment. Different materials were mixed for the preparation, leading to a high cost for water treatment. Sludge from papermaking has abundant fiber and inorganic salt, which can reduce the addition of raw materials in preparing the adsorption material and thus lower the cost. This work used recycled industrial paper sludge to prepare adsorption material to remove heavy metals from wastewater. The adsorption properties of the prepared sludge-chitosan material for Cu 2+ and Cr 3+ in wastewater were investigated. The impacts of adsorption time, pH, and initial concentrations of Cu 2+ and Cr 3+ on adsorption amount were studied and optimized. The saturated adsorption capacity of sludge-chitosan material for Cu 2+ and Cr 3+ can reach 114.6 and 110.3 mg/g. The adsorption kinetics satisfied the pseudo-second-order model, indicating two modes, physical diffusion, and chem-sorption, in the heavy metal adsorption by the sludge-chitosan materials. Physical distribution has little Effect on chemical adsorption. The materials can be applied to treating Cu 2+ and Cr 3+ containing wastewater with the proposed cheap and readily available sludge-chitosan material. The results confirmed that sludge-chitosan material possessed good regeneration performance and was an ideal adsorbent., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work presented in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

To mitigate the environmental impact of microplastics (MPs), the scientific community has innovated sustainable and biodegradable polymers as viable alternatives to traditional plastics. Chitosan, the deacetylated form of chitin, stands as one of the most thoroughly investigated biopolymers and has garnered significant interest due to its versatile applications in both medical and cosmetic fields. Nevertheless, there is still a knowledge gap regarding the impact that chitosan biopolymer films (CBPF) may generate in aquatic organisms. In light of the foregoing, this study aimed to assess and compare the potential effects of CBPF on the gastrointestinal tract, gills, brain, and liver of Danio rerio against those induced by MPs. The findings revealed that both CBPF and MPs induced changes in the levels of oxidative stress biomarkers across all organs. However, it is essential to note that our star plots illustrate a tendency for CBPF to activate antioxidant enzymes and for MPs to produce oxidative damage. Regarding gene expression, our findings indicate that MPs led to an up-regulation in the expression of genes associated with apoptotic response (p53, casp3, cas9, bax, and bcl2) in all fish organs. Meanwhile, CBPF produced the same effect in genes related to antioxidant response (nrf1 and nrf2). Overall, our histological observations substantiated these effects, revealing the presence of plastic particles and tissue alterations in the gills and gastrointestinal tract of fish subjected to MPs. From these results, it can be concluded that CBPF does not represent a risk to fish after long exposure., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The application of natural small molecule (NSM) in electrospun fibers is the key to achieving powerful functionality and sustainable development. However, the lack of understanding regarding the mechanism for loading NSM hinders the advancement of high-performance functional fibers. This work clarified the loading mechanism of NSM in polymer solution by comparing the different behaviors of curcumin (Cur), phloretin (PL), and tea polyphenols (TP) blended ethyl cellulose (EC) solutions. We found that TP may lead to the folding of polymer chains due to its strongest hydrogen bond, which in turn promoted the dispersion of TP along the polymer chain. Therefore, TP could achieve good electrospinnability at the highest loading capacity (16 times the Cur and 4 times the PL). Finally, chitosan was introduced into EC/TP to prepare tree-like nanofibers, achieving high-performance antibacterial air filtration. The filtration efficiency for 0.3 μm NaCl particles, pressure drop, and quality factor were 99.991 %, 85.5 Pa, and 0.1089 Pa -1 , respectively. The bacteriostatic rates against Escherichia coli and Staphylococcus aureus were all 99.99 %. This work will promote the application of NSM and the developments of multifunctional electrospun fibers and high-performance air filters., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Ultrafiltration (UF) is extensively used for algae removal because of its ability to retain algal cells with high efficiency, but it still faces the problem of membrane fouling and low retention capacity of dissolved organics. Hence, a strategy of coagulation with chitosan quaternary ammonium salt (HTCC) enhanced by sodium percarbonate (SPC) pre-oxidation was proposed to improve the UF performance. The fouling resistances were calculated by a resistance-in-series model based on Darcy's formula, and the membrane fouling mechanism was evaluated using a pore plugging-cake filtration model. The effect of SPC-HTCC treatment on the properties of algal foulants was explored, and the result showed that the water quality was improved with the maximum removal rates of 78.8 %, 52.4 % and 79.5 % for algal cells, dissolved organic carbon and turbidity, respectively. The SPC could achieve a mild oxidation effect that degraded the electronegative organics attached to algal cells without destroying the cell integrity, making the algal pollutants easier to agglomerate through subsequent HTCC coagulation by forming larger flocs. In terms of membrane filtration, the terminal normalized flux was increased from 0.25 to 0.71, with the reversible and irreversible resistances reduced by 90.8 % and 40.2 %, individually. The synergistic treatment reduced the accumulation of algal cells and algae-derived organics on the membrane surface as inferred from the interface fouling characteristics. The interfacial free energy analysis showed that the synergistic treatment reduced the adhesion of contaminants to the membrane surface, as well as the attraction among pollutants. Overall, the proposed process has high application prospects for algae-laden water purification., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

O-Carboxymethyl chitosan nanoparticles (O-CMC-NPs), which are organic pesticide carriers, have excellent application potential. Exploring the effects of O-CMC-NPs on non-target organisms, such as Apis cerana cerana, is critical for their effective application; however, such studies are limited. This study investigated the stress response of A. cerana Fabricius after O-CMC-NPs ingestion. The administration of high O-CMC-NP concentrations enhanced the activities of antioxidant and detoxifying enzymes in A. cerana, with the activity of glutathione-S-transferase increasing by 54.43 %-64.33 % after one day. The transit of O-CMC-NPs into the A. cerana midgut resulted in their deposition and adherence to the intestinal wall, as they cluster and precipitate in acidic conditions. The population of Gillianella bacteria in the middle intestine was remarkably reduced after 6 d of administration of high O-CMC-NP concentrations. Contrastingly, the abundance of Bifidobacteria and Lactobacillus in the rectum significantly increased. These results indicate that the intake of high concentrations of O-CMC-NPs causes a stress response in A. cerana and affects the relative abundance of crucial intestinal flora, which may pose a potential risk to the colony. This implies that even nanomaterials with favorable biocompatibility should be applied reasonably within a specific range to avoid adverse effects on the environment and non-target organisms in the context of large-scale research and promotion of nanomaterials., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Clay minerals are effective sorbents for toxic metal immobilization in contaminated soils and waters. However, their Cd immobilization efficiency is unclear when they are loaded with organics. In this study, sodium montmorillonite (Na-M) was successfully loaded with potassium humate, chitosan, and glycine to adsorb Cd(II) in solution. Potassium humate loaded Na-M (Na-M-HA), which had the highest specific surface area and cation exchange capacity (CEC), showed the highest Cd(II) adsorption capacity (73.7 mg g -1 ), 22.5 % and 81.8 % higher than that of chitosan loaded Na-M (Na-M-CTS) and glycine loaded Na-M (Na-M-G), respectively. The pseudo-second-order kinetic model best described (R 2  > 0.98) the adsorption kinetics of Cd(II) on the three Na-Ms, indicating that the adsorption processes were of chemisorption nature. The adsorption isotherm of Cd(II) on Na-M-HA was of the Freundlich type, suggesting multilayer adsorption. In contrast, the isothermal adsorption of Cd(II) on Na-M-CTS (R 2  = 0.99) and Na-M-G (R 2  = 0.89) was better described by the Langmuir model, suggesting the dominance of monolayer adsorption in the adsorption process. High temperature, high pH, low background ionic strength, and low valence competing cations favored Cd(II) adsorption on Na-M-HA. The underlying mechanisms of Cd(II) sorption on Na-M-HA were electrostatic attraction, ion exchange and complexation. Na-M-HA was applied to a Cd polluted soil planted with lettuce (Lactuca sativa L.). in a pot experiment. Compared to the control with no adsorbent application, Na-M-HA application at 2 % effectively reduced the available Cd content in soil and Cd accumulation in plant by 36.0 % and 56.8 %, respectively. This work demonstrated that Na-M-HA is a green, low-cost and excellent adsorbent for Cd stabilization, and that its application in Cd-polluted soils can efficiently reduce Cd bioavailability and thereby Cd transfer along the food chain and eventually reduce the threat of Cd pollution to human health., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Chitosan is widely used as a dewatering flocculant, but whether it affects hydrogen production from sludge anaerobic fermentation is unclear. This study aimed to elucidate the role of chitosan in the dark fermentation of waste activated sludge for hydrogen production. The results showed that chitosan had a negative effect on hydrogen production from sludge. Chitosan at 30 g/kg total suspended solids reduced hydrogen accumulation by 56.70 ± 1.22 % from 3.94 ± 0.12 to 1.71 ± 0.10 mL/g volatile suspended solids. Chitosan hindered the solubilization of sludge by flocculation, which reduced the available substrate for anaerobic fermentation. In addition, chitosan interfered with the electron transport system by reducing cytochrome C and caused lipid peroxidation by inducing reactive oxygen species, thereby inhibiting the activity of enzymes involved in anaerobic fermentation. Hydrogen production was reduced because hydrogen-producing processes (i.e., hydrolysis, acidification, and acetification) were inhibited more strongly than hydrogen-consuming processes (i.e., methanogenesis, sulfate reduction, and homoacetogenesis). Furthermore, chitosan enriched the abundance of Spirochaetaceae sp. and Holophagaceae sp., which occupied the survival space of hydrogen-producing microorganisms. This study reveals the potential impact of chitosan on hydrogen production in dark fermentation of sludge and provide direct evidence that chitosan triggers oxidative stress in anaerobic fermentation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

To date, most existing engineering materials have difficulty simultaneously separating oil/water and removing heavy metals from complex oily wastewater. In response to this challenge, a novel multifunctional composite hydrogel membrane (named PVA-CS-LDHs) was fabricated by incorporating chitosan (CS) and nanohydrotalcite (LDHs) into a polyvinyl alcohol (PVA) hydrogel. This material was developed using an easy yet versatile strategy of freezing and salting-out, which can enable the formation of a PVA-CS-LDH hydrogel membrane in one step and endow the PVA-CS-LDHs with high strength, excellent stretchability, favourable shape recoverability, and an ideal 3D microstructure. The PVA-CS-LDH membrane can purify emulsified oil and metal ions simultaneously with a separation efficiency of 99.89 % for emulsified oil and a removal efficiency of 97.44 % for Pb2+ ions. Additionally, the high-efficiency, multifunctional, high-antifouling and eco-friendly properties of the PVA-CS-LDH membrane make it a promising hydrogel material for both emulsified oil separation and heavy metal ion removal. Thus, this material provides critical application potential that can address scientific and technological challenges in complex oily wastewater purification., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

A modified chitosan-polyvinyl alcohol (PVA) hydrogel was developed by incorporating Fe 3 O 4 nanoparticles. Four chitosan-Fe 3 O 4 (ChFe) hydrogel types were developed based on chitosan:Fe 3 O 4 ratio as 1:0, 1:1, 1:0.5 and 1:0.25. Batch sorption experiments were conducted with different pH, dosage, kinetics, and isotherms. The exhausted ChFe hydrogels were evaluated for their regeneration and reuse capability with different acids and bases. The best hydrogel for arsenic (V) [As(V)] adsorption was 1:0.5 ratio ChFe hydrogel. The highest As(V) adsorption (89 %) was at pH 4 and the adsorption capacity gradually decreased with increasing solution pH. Within the pH 4-6 range, the hydrogel surface became positively charged due to protonation of NH 2 and OH groups in the polymer chain and the positive surface attracted H 2 AsO 4 - and HAsO 4 2- oxyanions. The experimental kinetic data was well-fitted to the Elovich model (R 2 of 0.99) while the Freundlich isotherm model best described the isotherm data (R 2 of 0.97). The models predicted chemisorption mechanisms on ChFe hydrogel composites. Electrostatic attractions with NH 3 + and OH 2 + , ligand-exchange inner-sphere complexes formation and bidentate corner-sharing ( 2 C) and bidentate edge-sharing ( 2 E) trimetric surface complexes formation have been proposed as the adsorption mechanism of As(V) into ChFe hydrogel. 0.1 M CH 3 COOH showed the best regeneration pattern with 75, 96, 81, 53 and 43 % of 1 st , 2 nd , 3 rd , 4 th and 5 th adsorption respectively. Because of this re-usable capability, the As(V) adsorption capacity is not a single value from one adsorption cycle, but a cumulative value of several adsorption cycles and it was 17.39 mg/g for five adsorption cycles. Open for regeneration and reuse, no post-treatment is needed for adsorbent-water separation, allow applications of the ChFe hydrogel composite in a wide range of applications such as water filtration and purification systems. The modification with ChFe further expands the application capacity since the ChFe can remove other contaminants as well., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Microalgal biomass harvesting and cell disruption are the main bottlenecks for downstream processing of microalgae such as high-value bioproducts extraction and biofuels production. In this study, we evaluated the performance of dual flocculation between cationic surfactants and bio-polymer of chitosan for simultaneous biomass harvesting and bioproducts extraction from Chlorella sorokiniana microalgae. First, the effects of individual natural flocculants of chitosan and two cationic surfactants: cetyltrimethylammonium bromide (CTAB) and dodecyltrimethylammonium bromide (DTAB) on biomass harvesting were studied. Next, the synergistic effect of dual flocculation between the cationic surfactants and chitosan on harvesting efficiency, time and flocculant dosage was investigated. Finally, we evaluated the potential of high value bioproducts extraction from microalgae after the individual and dual flocculation processes. Zeta potential analysis and microscopic images were employed to achieve mechanistic understanding. Maximum biomass harvesting efficiencies of 85 %, 88 % and 78 % were achieved using individual flocculants of chitosan, CTAB and DTAB, under their optimum dosages of 100, 400 and 4000 mg/L, respectively. A significant synergistic effect of dual flocculation between chitosan (C) and cationic surfactants on biomass harvesting efficiency (CTAB-C: 99 % and DTAB-C: 97 %), settling time (CTAB-C: 2 min and DTAB-C: 5 min) and optimum dosage of surfactants (CTAB-C: 100 mg/L and DTAB-C: 1000 mg/L) was observed. The synergistic effect was associated with multiple flocculation mechanisms of charge neutralization and bridging induced by cationic surfactants and chitosan, respectively. Furthermore, bioproducts recovery efficiencies of 12 %, 25 % and 15 % of cell dry weight were achieved for protein, carbohydrate and lipid, respectively by using dual flocculation of CTAB surfactant and chitosan at much lower dosage of 100 mg/L., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Chitosan, as a natural non-toxic biomaterial, has been demonstrated to enhance plant defense against oxidative stress. However, the general pattern and mechanism of how chitosan application modifies the amelioration of oxidative stress in plants have not been elucidated yet. Herein, we performed a meta-analysis of 58 published articles up to January 2022 to fill this knowledge gap, and found that chitosan application significantly increased the antioxidant enzyme activity (by 40.6 %), antioxidant metabolites content (by 24.6 %), defense enzyme activity (by 77.9 %), defense-related genes expression (by 103.2 %), phytohormones (by 26.9 %), and osmotic regulators (by 23.2 %) under stress conditions, which in turn notably reduced oxidative stress (by 32.2 %), and increased plant biomass (by 28.1 %) and yield (by 15.7 %). Moreover, chitosan-mediated effects on the amelioration of oxidative stress depended on the properties and application methods of chitosan. Our findings provide a comprehensive understanding of the mechanism of chitosan-alleviated oxidative stress, which would promote the application of chitosan in plant protection in agriculture., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

A novel adsorbent of carbon@chitosan@montmorillonite nanosheet (C@CS@ MTN) was successfully fabricated layer-by-layer assembly method to deal with cationic dye wastewater. Batch adsorption experiments showed that the adsorption capacities of MB and RhB were higher than 325 mg·g -1 and 236 mg·g -1 , respectively, indicating that C@CS@MTN exhibited an excellent adsorption performance. Through quantum chemistry simulations, the molecular electrostatic potential, electron density, differential charge density, molecular orbital distribution and adsorption binding energy were analyzed to reveal the adsorption reaction mechanism between C@CS@MTN and cationic dyes. The results indicated that SiO tetrahedron ring and AlO octahedron ring released from montmorillonite with inherent periodic structure was beneficial to electrostatic attraction, while cation-π interaction benefitted from the interaction between Al atoms of AlO octahedron ring and benzene ring. It was noteworthy that the electron transfer direction of electrostatic attraction was from O atoms of SiO tetrahedron ring to the benzene ring of dye molecules, but the electron transfer direction of cation-π interaction was from benzene ring of dye molecules to Al atoms of AlO octahedron ring. These results provide fundamental theoretical support for the functional design of mineral-based adsorbents and the efficient removal of cationic dyes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Cr (VI) exists in anion form and can be reduced to positive charged Cr (III) under certain conditions. Can positive charged Cr (III) be continually used for absorbing Cr (VI) to achieve cyclic accumulation of chromium? In this paper, an ion imprinting material for adsorption of Cr (VI) was prepared by dispersing polypyrrole (PPy) in a gelatin/chitosan (Gel/CS) hydrogel network, named Gel/CS/PPy. Based on the conversion of Cr (VI) to Cr (III), a cyclic enrichment process including adsorption-photoreduction-fixation-readsorption of Cr (VI) was established in Gel/CS/PPy hydrogel. The composition and structure of the Gel/CS/PPy were analyzed by scanning electron microscopy (SEM), Fourier transform-infrared spectroscopy (FT-IR), thermogravimetric (TGA), texture analyzer (Universal TA), zeta potential and ultraviolet-visible-near infrared spectra (UV-vis-NIR). The conversion of Cr (VI) and Cr (III) and its promoting effect on readsorption were verified by XPS. The results showed that Gel/CS/PPy has good adsorption capacity for Cr (VI) and excellent photocatalytic ability to reduce Cr (VI) to Cr (III). Cr (III)-loaded Gel/CS/PPy can be further used to adsorb Cr (VI) and showed good adsorption efficiency even after four cycles. The optimal operating condition for Cr (VI) adsorption is pH = 3; 2 g/L dose of Gel/CS/PPy; and the adsorption capacity of Cr (VI) was about 106.8 mg/g after six adsorption cycles. Since Gel/CS/PPy is composed of organic components, high purity chromium can be recovered by simple calcination method later. Therefore, the synthesized Gel/CS/PPy has great potential in the practical application of low concentration Cr (VI) treatment in water., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Selective and effective adsorptive removal of radiocesium is of great importance in terms of nuclear waste management and environmental remediation, but is still challenging because of its radioactive and non-complexing nature. Herein, metal hexacyanoferrates (MHCF, M = Cu, Co, or Ni) modified fibrous chitosan was prepared by multiple sequential adsorption and self-assembly approach, and applied for the selective and effective adsorption of Cs + . The physically supported MHCF in chitosan fibers showed good crystallinity and stability, and the obtained fibrous composite has high specific surface area (18.2-29.4 m 2 g -1 ). Moreover, MHCF crystals endowed the fibrous chitosan-based adsorbent with a high adsorption capacity and selectivity towards Cs + . Its adsorption kinetic and isotherm performance followed the pseudo second-order model and the Sips model. The q m value of three fibrous MHCF/chitosan (M = Cu, Co, or Ni) composites was 24.9-70.3 mg g -1 . The fibrous CuHCF/chitosan composite had the highest q m among the three composites. In summary, the modified chitosan can selectively and effectively remove Cs + from complicated aqueous solutions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

In this study, a novel fibrous chitosan biosorbent was prepared using LiOH/KOH/urea/H 2 O (4.5:7:8:80.5 by weight) as spinning solvent. The fibrous chitosan exhibited a higher adsorption capacity and a faster adsorption rate for Co 2+ and Sr 2+ , compared with spherical chitosan due to its high specific surface area (16.9 m 2 g -1 ), uniform fineness (24.1 μm), and good mechanical strength. The adsorption capacity of fibrous chitosan for Co 2+ and Sr 2+ was 31.3 mg g -1 and 20.0 mg g -1 , respectively, which was higher than that of spherical chitosan (22.5 mg g -1 for Co 2+ and 8.9 mg g -1 for Sr 2+ ). The coordination between -NH 2 /-OH of chitosan and the nuclide ions was the rate-limiting step. The improvement of adsorption performance was due to the higher specific surface area which increased the exposure degree of functional groups (adsorptive sites). This new wet-spun fibrous chitosan biosorbent showed great potential in the adsorptive removal of nuclides ions from aqueous solution., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The activity of micro-sized zero-valent iron (MZVI) material for nitrate removal in neutral pH and low C/N ratios water needs to be improved. In this study, micro-sized zero-valent iron@chitosan (MZVI@CS) material was synthesized through embedding MZVI particles into chitosan (CS) gel by sol-gel method, and was used for deep removal of NO 3 - -N in the absence of organic carbon sources and neutral pH. The NO 3 - -N removal rate of MZVI@CS was 0.37 mg-N·L -1 ·d -1 (dosage of 1%, initial pH = 7, 25 °C, initial nitrate concentration = 15 mg-N·L -1 ), which was 11.33 times higher than that of MZVI. The apparent activation energy (E a ) of MZVI@CS with nitrate was 38.23 kJ·mol -1 . MZVI@CS can remove nitrate effectively at a low concentration (15 mg-N·L -1 ). A stable denitration rate (0.37-2.28 mg-N·L -1 ·d -1 ) could be maintained under weak acidic, neutral and alkaline conditions (pH = 5-9). More than 80% of reduced nitrate was converted to N 2 , and only a small amount was converted to NH 4 + or NO 2 - . The gel structure of MZVI@CS eliminated the agglomeration between MZVI particles while the forming of Fe-CS chelates reduced the formation of iron oxide and solved the problems of passivation, hence successfully strengthened the NO 3 - -N removal efficiency of MZVI. Therefore MZVI@CS has great application potential in NO 3 - -N deep removal of water bodies with neutral pH and low C/N ratios., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier B.V.)

Due to the presence of several hydroxyl and amino groups on the surface, chitosan (CS) has been reported to be a potential candidate to solve the pollution caused by dyes in different industrial wastewater. However, it is associated with the recycling issues. Nano-Fe 3 O 4 has the advantages of easy magnetic separation and surface functionalization, which can improve the efficiency as well as selectivity of separation. However, its tendency for agglomeration can reduce the adsorption capacity. MXene can provide suitable support for both CS and Fe 3 O 4 to construct new MXene@Fe 3 O 4 @CS composites. In this study, MXene@Fe 3 O 4 @CSmagnetic nanosphere was synthesized by ultrasonic self-assembly to remove Congo red (CR). Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Fourier Transform Infrared (FT-IR) spectroscopy were employed to characterize the nanocomposites. According to the batch experiments, the adsorption kinetics were found to predominantly follow quasi-secondary rate kinetics. The adsorption followed Langmuir isotherm model. The adsorption process was found to be endothermic, entropy-driven, and thermodynamically spontaneous process. The adsorption capacity for CR was estimated as 620.22 mg·g -1 ., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Flocculation has been widely employed in treatment of mineral tailings and water management. In this study, a chitosan-graft-poly(acrylamide-dimethyl diallyl ammonium chloride) (Chi-g-P(AM-DMDAAC)) was synthesized in-house. The adsorption and interaction mechanisms of Chi-g-P(AM-DMDAAC) and an anionic polyacrylamide (APAM) in a two-step flocculation process of kaolinite were explored using settlement tests, zeta potential measurement, quartz crystal micro-balance with dissipation (QCM-D) and atomic force microscopy (AFM) technique. The type of primary flocculant was critical for the two-step flocculation process. The treatment of the kaolinite suspension using 1 mg/L of Chi-g-P(AM-DMDAAC) followed by adding 2 mg/L of APAM displayed more efficient flocculation performance. QCM-D results showed that three dissipative layers were assembled on model kaolinite surface after sequentially injecting 3.5 mg/L of Chi-g-P(AM-DMDAAC), 0.05 wt% kaolinite suspension and 2.5 mg/L of APAM. The above total adsorption amount (Δf of -64.9 Hz) was much higher than that of using the two flocculants in reverse order (Δf of -23.1 Hz). This result indicated that the adsorption layer of the positively charged Chi-g-P(AM-DMDAAC) on kaolinite surface provided active adsorption sites for APAM. Further AFM measurement confirmed that the average adhesion between the silicon tip adsorbed Chi-g-P(AM-DMDAAC) and model kaolinite surface in 2.5 mg/L APAM solution increased from 0.25 ± 0.1 nN to 4.2 ± 0.3 nN with the effective interaction range of 700 nm, which was stronger than that measured between a bare silicon tip and silica substrate in single-component-flocculant solutions. The highly efficient two-step flocculation process could be ascribed to the strong electrostatic attraction between the kaolinite and the oppositely charged Chi-g-P(AM-DMDAAC) and APAM. Findings in this study will benefit the development of environmentally friendly flocculant for mineral tailings and water treatment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Manures, storages for antibiotic resistance genes (ARGs), pollute soil and water as well as endanger human health. Recently, we have been searching a better solution to remove antibiotics and ARGs during aerobic composting. Here, the dynamics of chitosan addition on the profiles of 71 ARGs, bacterial communities, chlortetracycline (CTC), ofloxacin (OFX) were investigated in chicken manure composting and compared with zeolite addition. Chitosan addition effectively reduces antibiotics contents (CTC under detection limit, OFX 90.96%), amounts (18) and abundance (56.7%, 11.1% higher than zeolite addition) of ARGs and mobile genetic elements (MGEs) after 42 days composting. Network analysis indicated that a total of 27 genera strains assigned into 4 phyla (Firmicutes, Proteobacteria, Actinobacteria and Bacteroidetes) were the potential hosts of ARGs. Redundancy analysis (RDA) demonstrated that bacterial community succession is the main contributor in the variation of ARGs. Overall, chitosan addition may effect bacterial composition by influencing physic-chemical properties and the concentration of antibiotics, Cu 2+ , Zn 2+ to reduce the risk of ARG transmission. This study gives a new strategy about antibiotics and ARGs removal from composting on the basis of previous studies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)