Preparation of poly(chitosan-acrylamide) flocculant using gamma radiation for adsorption of Cu(II) and Ni(II) ions

Targeted elimination of molybdenum ions from a leaching solution with the ability of radiated grafting GMA-PAN nanofibers

In this study, electrospun polyacrylonitrile nanofibers were effectively functionalized for enhanced molybdenum ion adsorption through a multi-step approach. Initially, glycidyl methacrylate was grafted onto the nanofibers via irradiation-induced grafting polymerization, followed by chemical modification with various amino groups, with triethylamine identified as the optimal modifier. The impacts of key synthesis parameters and reaction conditions on grafting level and adsorption capacity were thoroughly investigated, with a focus on achieving maximum efficiency. The resulting nanofibers were characterized using FTIR, SEM, and BET techniques, confirming the successful modification and structural features conducive to adsorption. Furthermore, a comprehensive experimental design, incorporating a central composite design, yielded optimal conditions for molybdenum adsorption, with key parameters including monomer concentration, irradiation dose, adsorbent mass, initial concentration, time, pH, temperature, and amine concentration. The adsorption kinetics were effectively described by the pseudo-second-order model, while the Langmuir isotherm model provided valuable insight into the adsorption behavior. Impressively, the adsorbent exhibited exceptional adsorption efficiency, surpassing 98% even after six adsorption-desorption cycles using 0.5 M HCl. Thermodynamic analysis revealed the exothermic nature of the adsorption process, along with decreased entropy and overall spontaneity, underlining the favorable conditions for molybdenum adsorption. Notably, the synthesized adsorbent demonstrated notable selectivity for molybdenum and achieved an impressive adsorption capacity of 109.79 mg/g, highlighting its potential for practical applications in molybdenum removal from aqueous solutions.

Chitosan-grafted hydrogels for heavy metal ion adsorption and catalytic reduction of nitroaromatic pollutants and dyes

Chitosan-grafted-poly(acrylic acid) (CS-g-PAA) and chitosan-grafted- poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (CS-g-P(AA-co-AMPS)) hydrogels were synthesized and then employed as adsorbents for the effective removal of Cu2+ and other heavy metal ions. The effect of hydrogel's composition on the Cu2+ adsorption was explored. The CS-g-PAA hydrogel demonstrated a superior adsorption capacity compared to pristine CS, PAA hydrogel, and CS-g-P(AA-co-AMPS) hydrogels. The adsorption followed the Langmuir isotherm model, and the pseudo-second order kinetic model. Additionally, the CS-g-PAA hydrogel exhibited relatively high adsorption performances toward Cr3+, Co2+, Ni2+, Pb2+, and Zn2+. Metal ions adsorbed within CS-g-PAA hydrogels underwent reduction to their corresponding metallic states and were reutilized as catalysts for the reduction of 4-nitrophenol. The comparative catalytic performances of the metal species in the hydrogel were in the order of Cu > Ni > Co > Zn. The reduction efficiency of Cu-CS-g-PAA increased with increased catalyst dosage, NaBH4 concentration, and temperature. A very low activation energy of 3.7 kJ/mol was observed. The catalyst maintained high catalytic performance even when subjected to real water samples and proved its reusability for up to three cycles. Moreover, the catalyst could effectively reduce 2-nitrophenol and methyl orange.

Development of a chitosan derivative bearing the thiadiazole moiety and evaluation of its antifungal and larvicidal efficacy

A new chitosan derivative bearing a new thiadiazole compound was developed, and its antifungal and larvicidal activities were investigated. The chitosan derivative (coded here as PTDz-Cs) was synthesized by the reaction between the carboxylic derivative of the thiadiazole moiety and chitosan. Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (1H/13C-NMR), gas chromatography–mass spectrometry (GC–MS), elemental analysis, X-Ray diffraction (XRD), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) were used to characterize the developed derivatives. Compared to chitosan, the PTDz-Cs derivative has a less crystalline structure and less thermal stability. The antifungal results revealed that PTDz-Cs exhibited potential activity against Rhizopus microspores, Mucor racemosus, Lichtheimia corymbifera, and Syncephalastrum racemosum where inhibition zones were 17.76, 20.1, 38.2, and 18.3 mm, respectively. The larvicidal efficacy of the PTDz-Cs derivative against A. stephensi larvae was tested, and the results exposed that the LC50 and LC90 values (first instar) were 5.432 and 10.398 ppm, respectively, indicating the high susceptibility of early instar mosquito larvae to PTDz-Cs. These results emphasize that this study provided a new chitosan derivative that could be potentially used in the biomedical fields.

New thiadiazole modified chitosan derivative to control the growth of human pathogenic microbes and cancer cell lines

The emergence of multidrug-resistant microbes and the propagation of cancer cells are global health issues. The unique properties of chitosan and its derivatives make it an important candidate for therapeutic applications. Herein, a new thiadiazole derivative, 4-((5-(butylthio)-1,3,4-thiadiazol-2-yl) amino)-4-oxo butanoic acid (BuTD-COOH) was synthesized and used to modify the chitosan through amide linkages, forming a new thiadiazole chitosan derivative (BuTD-CH). The formation of thiadiazole and the chitosan derivative was confirmed by FT-IR, ¹H/¹³C-NMR, GC-MS, TGA, Elemental analysis, and XPS. The BuTD-CH showed a high antimicrobial effect against human pathogens Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Staphylococcus aureus, and Candida albicans with low MIC values of 25-50 μg ml^-1 compared to unmodified chitosan. The in-vitro cytotoxicity of BuTD-CH was evaluated against two cancer cell lines (MCF-7 and HepG2) and one normal cell (HFB4) using the MTT method. The newly synthesized derivatives showed high efficacy against cancerous cells and targeted them at low concentrations (IC₅₀ was 178.9 ± 9.1 and 147.8 ± 10.5 μg ml^-1 for MCF-7 and HepG2, respectively) compared with normal HFB4 cells (IC₅₀ was 335.7 ± 11.4 μg ml^-1). Thus, low concentrations of newly synthesized BuTD-CH could be safely used as an antimicrobial and pharmacological agent for inhibiting the growth of human pathogenic microbes and hepatocellular and adenocarcinoma therapy.

Synthesis and characterization of new functionalized chitosan and its antimicrobial and in-vitro release behavior from topical gel

Recently, chitosan and its derivatives have been gaining more attention due to their high integration into various biomedical applications. Herein, a new chitosan derivative was prepared by linking the chitosan (Cs) with a novel heterocyclic compound, Benzoimidazolyl-thiadiazole (BzimTD) to form Cs-BzimTD. The synthesis of the new chitosan derivative was confirmed by Fourier-Transform Infrared (FT-IR) spectroscopy, proton nuclear magnetic resonance (¹H NMR), thermogravimetric (TGA-DTG) analysis, elemental analysis, and UV-Visible spectrophotometer. Data showed the high efficacy of functionalized Cs-BzimTD to inhibit the growth of pathogenic microbes, Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans, with inhibition zones of 15.3 ± 0.6 - 9.2 ± 0.3 mm. Also, Cs-BzimTD was applied in a topical gel formulation by using two different polymers, Carbopol 940 (CP) and Carboxymethyl Cellulose (CMC) to form three gel formulations: Cs-BzimTD-CP, Cs-BzimTD-CMC, and Cs-BzimTD-CP-CMC. The new gels were checked for physical appearance, viscosity, Cs-BzimTD release, pH, spread-ability, and drug content. The results showed that all formulations were clear, transparent, and homogeneous with non-irritant pH values for skin (6.4 - 6.8). The spread-ability was found in the range of 7.1 - 9.4 g.cm/s. The Cs-BzimTD-CP formula showed the maximal Cs-BzimTD content percentage (86.5%) and the Cs-BzimTD release varied from 89.9 to 81.6% after 8 h depending on the gel formulation, with a maximum release achieved for Cs-BzimTD-CMC.

Evaluating the performance of bridging-assembly chelating flocculant for heavy metals removal: Role of branched architectures

A novel chelating flocculant with branched architectures, polyacrylamide grafted maleoyl chitosan-mercaptoacetic acid (PAM-g-M(CS-MA)), was successfully fabricated using maleic anhydride as the "bridge" between chitosan and polyacrylamide. The functional groups and structural characteristic information of copolymers were obtained via characterization analysis. Flocculation performance was systematically investigated via purifying a series of simulated wastewater containing Cu or Cd. The properties of the flocs were studied to give in-depth evidences for the role of chelation groups and branched architectures in flocculation. Results indicated that PAM-g-M(CS-MA) showed excellent flocculation capacity for heavy metals in high concentrations and was superior to other chelating flocculants. The maximum flocculation efficiency of Cu (93.90%) and Cd (92.47%) was achieved by PAM-g-M(CS-MA) at pH 7, dosage of 100 mg L^-1 and stirring speed of 90 rpm. The flocculation mechanisms of PAM-g-M(CS-MA) were deeply explored through the analyses of floc properties. The strong synergistic chelation of mercapto, carboxyl, amide and hydroxyl groups predominated for the capturing of heavy metals; and the branched architectures facilitated the formation of large and stable flocs via adsorption and bridging-furl effect. This study provided a solid foundation for the fabrication of flocculants for heavy metal wastewater treatment.

Variations of heavy metals, nutrients, POPs and particle size distribution during "sludge anaerobic digestion-solar drying-land utilization process": Case study in China

Sewage sludge was rich in pollutants such as heavy metals, nutrients and persistent organic pollutants. Anaerobic digestion can effectively degrade the pollutants while achieving sludge stabilization and reduction. This study took a sludge treatment plant located in Anhui Province, China as a case study, investigating the variations of multiple substances and particle size distribution during sludge anaerobic digestion-solar drying-land utilization process. The results demonstrated anaerobic digestion had a positive effect on the removal of heavy metals, nutrients and persistent organic pollutants, for polycyclic aromatic hydrocarbons, antibiotics and disinfection by-products with 41.38%, 62.26% and 68.68%, respectively, which were related to their molecular weight and structure. Large amounts of heavy metals would flow away with liquid digestate, in which Cr and Hg were the most and least, 90.44% and 41.95% respectively. The degradation of extracellular polymers in this process led to a decrease in particle size distribution, which caused the deterioration of sludge dewatering performance. Nutrients and water content increased and decreased respectively during solar drying along with the volatilization of organic matter under high temperature, which was beneficial for the final sludge product to subsequent land utilization. No significant correlation was demonstrated between heavy metals and sludge properties besides electrical conductivity. The study provided a new thinking on the variations of different substances and the way of actual treatment and disposal from the perspective of sludge anaerobic digestion-solar drying-land utilization process, which had a considerable significance for the further promotion and application of anaerobic digestion process in China's engineering community.

Synthesis and characterization of a novel benzothiazole functionalized chitosan and its use for effective adsorption of Cu(II)

Contamination of water with the copper(II) ions leads to serious diseases such as liver damage and cancer. This deadly effect prompted us to target the synthesis of a novel functionalized chitosan (Cs-BT) to be used as an adsorbent for removing the copper(II) ions from the aqueous solution. The functionalization was done by introducing benzothiazole moiety into the chitosan (Cs) chain and confirmed by the full disappearance of the NH₂ band in the FT-IR spectrum of the adsorbent. The TGA-DTG analysis revealed that the functionalization reduced the thermal stability of the adsorbent (Cs-BT) as compared with pure chitosan. The adsorption was evidenced by SEM and EDX analysis. The adsorption study demonstrated that the optimal adsorption conditions were 120 min contact time, pH = 6, and initial Cu(II) concentration 200 mg/L. At these conditions, the Cs-BT achieved a maximum copper adsorption capacity of 1439.7 mg/g. Consequently, Cs-BT could be a promising and efficient Cu adsorbent in water treatment. Study the adsorption kinetics and isotherms manifested that the pseudo-first-order was better than pseudo-second-order and Temkin isotherm was better than Langmuir, Freundlich, and Dubinin-Radushkevich for explaining the adsorption process. The calculated thermodynamic parameters implied the spontaneity and the endothermic nature of the adsorption process.

Facile fabrication of chitosan-based adsorbents for effective removal of cationic and anionic dyes from aqueous solutions

To develop chitosan-based adsorbents for the treatment of dye wastewater, poly acrylic acid (PAA) and poly acrylamide (PAM) were simultaneously grafted onto the chitosan (CTS) chain to obtain a grafted-crosslinked material g-CCTS, and then, Fe-g-CCTS was prepared via coordination of Fe(III) onto the prepared g-CCTS. Two adsorbents g-CCTS and Fe-g-CCTS were fully characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), Nitrogen adsorption and desorption, X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and thermogravimetric (TG) analysis. In adsorption experiment, g-CCTS exhibited effective adsorption towards cationic dye methylene blue (MB), and Fe-g-CCTS showed effective adsorption towards anionic dye reactive brilliant red (RBR). The effects of solution pH, salt concentration and temperature on the adsorption process were investigated. The maximum adsorption capacity of g-CCTS for MB was up to 79.09 mg/g at pH 12, and that of Fe-g-CCTS for RBR reached 918.53 mg/g at pH 2. It was observed that both adsorption processes were monolayer adsorption, and conformed to the pseudo-second-order model and the Langmuir isotherm model. This research provided a facile and accurate method for effective dyes removal from wastewater.

Novel chitosan-based flocculants for chromium and nickle removal in wastewater via integrated chelation and flocculation

Carboxylated chitosan (CPCTS) is used as substrates in the design and synthesis of CPCTS-based flocculants through UV-initiated polymerization techniques. The synthesized flocculants are applied to remove Cr and Ni ions from chromic acid lotion and electroplating wastewater through two-stage flocculation. This study investigates the effect of flocculant dosage, pH, reaction time, and stirring speed on the removal efficiency of Cr and Ni ions. Results indicated that the total Cr removal ratios by CPCTS-graft-polyacrylamide-co-sodium xanthate (CAC) and CPCTS-graft-poly [acrylamide-2-Acrylamido-2-methylpropane sulfonic acid] (CPCTS-g-P(AM-AMPS)) are 94.7% and 94.6%, respectively. The total Ni removal efficiencies by CAC and CPCTS-g-P(AM-AMPS) are 99.3% and 99.4%, respectively. The two-stage flocculation with CPCTS-based flocculants could reduce the total concentrations of Cr and Ni to 1.0 mg/L and 0.5 mg/L, respectively. The relationship of removal capacity and structural properties between the flocculants with different functional groups is established through Fourier transform infrared spectroscopy, nuclear magnetic resonance, scanning electron microscopy, and X-ray diffraction. The micro-interfacial behavior between the colloidal particles and the solution during the integrated chelation-flocculation are elucidated. Thus, CPCTS-based flocculants could be a potential material for the removal of high amounts of Cr and Ni ions in industrial wastewater.

Chitin/Chitosan: Versatile Ecological, Industrial, and Biomedical Applications

Chitin is a linear polysaccharide of N-acetylglucosamine, which is highly abundant in nature and mainly produced by marine crustaceans. Chitosan is obtained by hydrolytic deacetylation. Both polysaccharides are renewable resources, simply and cost-effectively extracted from waste material of fish industry, mainly crab and shrimp shells. Research over the past five decades has revealed that chitosan, in particular, possesses unique and useful characteristics such as chemical versatility, polyelectrolyte properties, gel- and film-forming ability, high adsorption capacity, antimicrobial and antioxidative properties, low toxicity, and biocompatibility and biodegradability features. A plethora of chemical chitosan derivatives have been synthesized yielding improved materials with suggested or effective applications in water treatment, biosensor engineering, agriculture, food processing and storage, textile additives, cosmetics fabrication, and in veterinary and human medicine. The number of studies in this research field has exploded particularly during the last two decades. Here, we review recent advances in utilizing chitosan and chitosan derivatives in different technical, agricultural, and biomedical fields.

Plasma-induced synthesis of chitosan-g-polyacrylamide and its flocculation performance for algae removal

Chitosan (CS)-g-polyacrylamide (PAM) is a highly efficient and environmentally friendly flocculant, which was synthesized through plasma-induced graft copolymerization of CS and acrylamide (AM). The effects of monomer concentration, AM:CS ratio, discharge power, discharge time, post-polymerization temperature, and post-polymerization time on the intrinsic viscosity, grafting ratio, and grafting efficiency of CS-g-PAM were investigated. The optimum conditions of graft copolymerization were as follows: 20% monomer concentration, 7:3 AM:CS ratio, 40 W discharge power, 90 s discharge time, 50°C post-polymerization temperature, and 24 h post-polymerization time. The structural characteristics of CS-g-PAM were characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction. CS-g-PAM exhibited better flocculation efficiency than the commercially available PAM in both diatomite-simulated wastewater and low-turbidity algal water. The optimal turbidity removal efficiency for the diatomite-simulated wastewater was 99.9%, which was obtained with 6 mg L^-1 of CS-g-PAM at pH 11.0 and 250 s^-1 of velocity gradient. In low-turbidity algal water, the optimal removal efficiencies for chlorophyll-a, turbidity, and COD were 93.6%, 94.5%, and 98.2%, respectively.

Preparation of diglycolamide polymer modified silica and its application as adsorbent for rare earth ions

Three novel diglycolamide monomers were synthesized and polymerized on silica. The diglycolamide polymer grafted silica were used as adsorbents for rare earth ions. The effects of acid concentration, structure of monomer, initial solution concentration, contact time and coexisting ions on adsorption of rare earth ions were investigated in detail. It was shown that the adsorption capacity increased with increasing acid concentration. Three adsorbents exhibited selectivity for middle and heavy rare earth over light rare earth in different extent. The adsorbent prepared from the monomer having the largest alkyl substituent showed the lowest adsorption capacity but the highest selectivity for different rare earth elements (REEs). Adsorption data were well fitted to the Langmuir isotherm and pseudo-second-order models. The presence of high concentrations (100 fold) of coexisting metal ions, K(I), Cr(II), Cu(II) or Fe(III), does not decrease the adsorption for rare earth ions seriously.

Synthesis of chelating polyamine fibers and their adsorption properties for nickel(ii) ions from aqueous solution

In this work, a novel fibrous material PA–PVAF has been prepared. In the adsorption experiments of Ni(ii), the fibrous material PA–PVAF showed excellent adsorption performance, which can be used as a promising adsorbent.