Highly efficient absorption of cationic dyes by nano composite hydrogels based on κ-carrageenan and nano silver chloride

Eco-friendly Lignin/N,N-dimethylacrylamide Hydrogel with Carrageenan and Polyvinylpyrrolidone for Amphoteric Adsorption of Methylene Blue and Congo Red: Optimization, Characterization, and Adsorption

This study presents a new approach for the preparation of N,N-dimethyl acrylamide (DMA), and lignin/DMA hydrogels using gamma radiation, highlighting the synergistic amphoteric adsorption of Methylene Blue (MB) and Congo Red (CR) facilitated by incorporating carrageenan and polyvinylpyrrolidone (PVP). The hydrogel formulation was optimized with a ratio of 2:1:0.75:5 for carrageenan:PVP:lignin:DMA and a radiation dose of 25 kGy, resulting in maximum gelation and adsorption efficiency. X-ray diffraction and spectroscopic analysis suggested that ionic interactions among carrageenan, PVP, and DMA and hydrogen bonding from lignin facilitated amphoteric adsorption via sulfate-mediated amide activation. The adsorption process followed a pseudo-first order kinetic model, with film-layer diffusion recognized as the primary transport mechanism. The maximum adsorption capacities were 405 mg·g-1 for MB and 417 mg·g-1 for CR, aligning with Freundlich isotherm behavior, while both the adsorptions were endothermic and thermodynamically spontaneous. The hydrogels were reusable for at least four adsorption-desorption cycles. Assessments of germination index indicated that the hydrogels are non-phytotoxic to Zea mays, with root elongation suggesting possible agricultural applications. Further research is necessary to evaluate the long-term viability of repurposing dye-desorbed hydrogels in agrarian systems. The findings indicate that gamma-irradiated hydrogels may serve as effective and reusable adsorbents for dye removal.

Nanocomposite magnetic hydrogel based on κ-carrageenan and acrylic acid for the removal of Cd(II), Co(II), Cu(II), and Ni(II); Efficient adsorption enhanced by activated carbon and magnetic nanoparticles

A novel nanocomposite magnetic hydrogel was synthesized based on κ-carrageenan, acrylic acid, and activated carbon as an absorbent for removing heavy metal ions from aqueous solution. FT-IR spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and vibration sample magnetometer (VSM) were employed to confirm the structure of the nanocomposite hydrogels. The effects of contact time, pH, particle size, temperature, and metal ion concentration on the metal ion adsorption were investigated. The selectivity of the nanocomposite hydrogel for metal ions adsorption was determined in the sequence of Ni2+ > Cu2+ > Co2+ > Cd2+. Adsorption of the heavy metal ions from aqueous solution by the nanocomposite magnetic hydrogel was analyzed using Langmuir and Freundlich models. The adsorption capacity by the Langmuir model was found to be 156.25, 294.11, 454.54, and 285.71 mg/g for Ni2+, Co2+, Cd2+, and Cu2+, respectively. The reusability experiments indicated that about 60 % of initial adsorption can be achieved after 6 cycles.

Waste treats waste: Facile fabrication of porous adsorbents from recycled PET and sodium alginate for efficient dye removal

Dye-contaminated water and waste plastic both pose enormous threats to human health and the ecological environment, and simultaneously solving these two issues in a sustainable and resource-saving way is highly important. In this work, a sodium alginate-polyethylene terephthalate-sodium alginate (SA@PET) composite adsorbent for efficient dye removal is fabricated using wasted PET bottle and marine plant-based SA via simple and energy-efficient nonsolvent-induced phase separation (NIPS) method. Benefiting from its porous structure and the abundant binding sites, SA@PET shows an excellent methylene blue (MB) adsorption capacity of 1081 mg g-1. The Redlich-Peterson model more accurately describes the adsorption behavior, suggesting multiple adsorption mechanisms. In addition to the electrostatic attractions of SA to MB, polar interactions between the PET matrix and MB are also identified as adsorption mechanisms. It is worth mentioning that SA@PET could be recycled 7 times without a serious decrease in performance, and the trifluoroacetic acid-dichloromethane solvent involved in the NIPS process has the possibility of reuse and stepwise recovery. Finally, the discarded adsorbent could be completely degraded under mild conditions. This work provides not only a composite adsorbent with excellent cationic dye removal performance for wastewater treatment, but also an upcycling strategy for waste PET.

Selective Adsorption of Methyl Orange and Methylene Blue by Porous Carbon Material Prepared From Potassium Citrate

As the discharge amount of dye wastewater increases with the development of the textile printing and dyeing industries, the treatment of the dyes in the wastewater becomes more complex. The adsorption method is a commonly used method for treating dye wastewater. The adsorbent is the key factor affecting the adsorption performance. To develop a high-performance adsorbent, a porous carbon material prepared from potassium citrate by the calcination method was applied in the adsorption of dye-containing water in this study. The morphology and pore structure of the porous carbon materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and N2 adsorption/desorption isotherm. The porous carbon material with a specific surface area of 1436 m2 g-1, PC-900, was used as an adsorbent for the adsorption of methyl orange (MO) and methylene blue (MB). The results showed that the maximum adsorption capacity of PC-900 for MO and MB reached 927 and 1853.6 mg g-1, respectively. Studies on adsorption kinetics and adsorption isotherms showed that the pseudo-second-order kinetic model and the Langmuir isotherm model were more appropriate to describe the adsorption process of MO and MB by PC-900. In addition, the results of the mixed adsorption experiment of MO and MB dyes showed that PC-900 had selective adsorption for MB.

κ-Carrageenan/triazin-based covalent organic framework bionanocomposite: Preparation, characterization, and its application in fast removing of BB41 dye from aqueous solution

A novel and high efficient adsorbent was prepared based on an environmentally friendly substrate, κ-carrageenan, and a triazine-based covalent organic framework as a co-adsorbent component. Combining these two precursors leads to an effective nanocomposite for removing Basic blue 41 dye from aqueous media. After confirm the structural of prepared composite by various analysis, the adsorption properties were investigated. The optimum conditions were obtained in: pH: 7, temperature: 25 °C and contact time: 210 min; and adsorbent dosage of 10 mg. According to the isotherms study, the basic blue 41 dye adsorption was matched to the Longmuir model with single-layer mechanism. The kinetic of adsorption was studied and fitted with pseudo-second order model with R² = 0.971. From the results the maximum adsorption capacity of 833 mg/g was obtained in 15 min and the reusability tests showed 24% decrease in yield after three cycles.

A comprehensive review on the removal of noxious pollutants using carrageenan based advanced adsorbents

Rapid industrial development is associated with high discharge of toxic pollutants into the environment. The industries discharge their wastewater containing organic pollutants directly into the water system without treating them that has posed many serious threats to environmental protection. The use of bioadsorbents for the removal of such toxic pollutants from the waste water due to its simple synthesis, easy operation, effectiveness, and economic viability have emerged a new dimension in the wastewater treatment approaches. Various adsorbents have been prepared to examine their adsorption capacity against different adsorbates, but, to attain sustainability, biocompatibility, and biodegradation, bio-adsorbents have been found to won the battle. Seaweed derived polysaccharide; Carrageenan (CR) has been proven to be an excellent adsorbent for the wastewater treatment. It has been successfully modified with various components to form CR based-magnetic composites, hydrogels, nanoparticle modified CR composites and many others to enrich and diversify its properties. In this review, we have explained the adsorption behaviour of various carrageenan based adsorbents for the removal of different dyes. The influence of various parameters such as the effect of initial concentration, adsorbent dosage, contact time, pH, temperature, and ion concentration on dye adsorption is well explained. This paper also summarizes the structure, morphology, swelling ability, and thermal stability of carrageenan. The data also expounds on the adsorption capacity, kinetic model, isotherm model, and nature of the adsorption process. Different types of solvents are used for the regeneration and reusability of carrageenan adsorbents and their regeneration studies and desorption efficiency is well-explained. The adsorption mechanism of dyes onto carrageenan based adsorbents has been well described in this review. This review provides a deep insight about the use of carrageenan based adsorbents for the wastewater treatment.

Carrageenan-based nano-hybrid materials for the mitigation of hazardous environmental pollutants

Fast industrialization and population growth are associated with the increased release of hazardous contaminants in the environment. These hazardous substances, including pharmaceutical, biomedical, personal-care products, heavy metals, endocrine-disrupters, and colorants, pollute the ecosystem by disturbing nature's balance. Nanotechnology has paved new horizons in biochemical engineering by designing novel approaches of integrating nanoscale science with biotechnology to construct improved quality materials for target uptake of pollutants. Recently, nanostructured materials have emerged as research and development frontiers owing to their excellent properties. The tailored designing of nanohybrids constructs with physicochemical alteration enables the nano-bioadsorbent with high target specificity and efficiency. The development of eco-friendly, biodegradable, cost-efficient, and biopolymer-based nanohybrid constructs is gaining attention to remove hazardous environmental pollutants. κ-carrageenan biopolymer is frequently used with different nanomaterials to design nanohybrid bio-adsorbents to remove various contaminants. Herein, the potentialities of carrageenan-based nanohybrid constructs in environmental remediation have been summarized. Different nanostructures, e.g., silica, non-magnetic/magnetic, carbon nanotubes/nanorods, nanoclay/nanomembrane, metal organic frameworks, graphene oxide, and other nanomaterials have been described in combination with carrageenan biopolymers focusing on environmental remediation.

Nanocomposite hydrogel based on sodium alginate, poly (acrylic acid), and tetraamminecopper (II) sulfate as an efficient dye adsorbent

In this study, a novel nanocomposite hydrogel (NCH) was prepared by in situ crosslinking and radical polymerization of acrylic acid (AA) in the presence of sodium alginate (Na-Alg), followed by loading of Cu²⁺ ions and reaction with ammonia. The main advantage of the synthesized NCH is the high adsorption of dye due to the large contact area. The structure of the NCH was studied by FT-IR spectroscopy, TEM, and SEM. TEM showed that the size of nanoparticles is about 5-30 nm. The adsorption of dye was studied by changing the different factors. The removal efficiency of Crystal Violet (CV) and Malachite Green (MG) was found to be more than 96% at concentration of 10 mg/L and pH = 6. The dye adsorption on the NCH is well described by Freundlich isotherm and pseudo-second-order kinetic models. The reusability experiments showed that about 95% of the initial adsorption was obtained after eight cycles.

Antimicrobial chitosan-agarose full polysaccharide silver nanocomposite films

The antibacterial and biocompatible films have attracted much attention due to their wide range of applications. Although a lot of work has been done in this area, research in this field is still very active and associated with the continuous development of new materials. In the present study full polysaccharide chitosan-agarose (CS-AG) films were produced by reaction of chitosan with periodate activated agarose, followed by reductive amination. Activated agarose was prepared by periodate oxidation of agarose, and then applied as a crosslinking agent to form a new polymeric network. The structure of periodate activated agarose was studied by nuclear magnetic resonances spectroscopy (¹H NMR) and Fourier-transform infrared spectroscopy (FT-IR). Rheological experiments showed that the viscosity of agarose solution changes rapidly by addition of periodate to the solution. Swelling, deswelling, and gel content of the films were determined at different pH. Chitosan-agarose silver nanocomposite (CS-AG/n-Ag) films were prepared by loading silver ions and subsequent reduction. The CS-AG/n-Ag films were characterized by FT-IR, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM).Transmission electron microscopy (TEM) image showed that the size of silver nanoparticles was about 2-7 nm. The bactericidal capacities (MBC/MIC) of the CS-AG/Ag films for Pseudomonas aeruginosa (P. aeruginosa), Escherichia coli (E. coli), and Staphylococcus aureus (S. aureus) were obtained 2.0, 1.0 and 2.0, respectively. The results demonstrate that the CS-AG/n-Ag films have good antibacterial activity against both the gram-negative and the gram-positive bacteria which make them suitable for food packaging and wound healing applications.

Nitrate removal from aqueous solutions by adsorption onto hydrogel-rice husk biochar composite

In the present study, we investigated the performance of hydrogel-rice husk biochar composites, as low-cost, alternative, and biocompatible adsorbents for separating nitrate ions from aqueous solutions. Hydrogel-biochar composite was synthesized at dosages of 2.5%, 3.6%, 4.8%, and 9.6% weight ratios of biochar. The composite was characterized by several common methods including FTIR, SEM, TEM, TGA, and DSC. In addition, the effect of contact time, initial concentration of nitrate ions, and solution pH were considered. The maximum removal of nitrate was about 34.3% at acidic pH (pH = 3) using 0.02 g of adsorbent in 25 ml of nitrate solution with the initial concentration (20 mg/L) and temperature of 25°C for 60 min. Based on the findings, 5% biochar in the composite was the optimal dosage. Adsorption kinetic study revealed that this process followed the first-order kinetic model. The experimental equilibrium adsorption data were tested by the Temkin isotherm model with R²  > 0.97. Based on the thermodynamic studies, the adsorption process was endothermic and spontaneous. Overall, the results suggested that the obtained composite can be specifically employed for removal of contaminations from aqueous solutions. PRACTITIONER POINTS: Hydrogel-biochar composite provides a biocompatible and cost-effective adsorbent. Hydrogel-biochar composite was applied to eliminate nitrate from aqueous solutions. Nitrate removal increased in the synthesized composite upon elevation of the weight ratio of biochar to 0.2 g.

Processing and modification of hydrogel and its application in emerging contaminant adsorption and in catalyst immobilization: a review

Due to the wonderful property of hydrogels, they can provide a platform for a wide range of applications. Recently, there is a growing research interest in the development of potential hydrogel adsorbents in wastewater treatment due to their adsorption ability toward aqueous pollutants. It is important to prepare such a hydrogel that possesses appropriate robustness, adsorption capacity, and adsorption efficiency to meet the need of water treatment. In order to improve the property of hydrogels, much effort has been made by researchers to modify hydrogels, among which incorporating inorganic components into the polymeric networks is the most common method, which can reduce the product cost and simplify the preparation procedure. Not only can hydrogel be applied as adsorbent, but it also can be used as matrix for catalyst immobilization. In this review, the key advancement on the preparation and modification of hydrogels is discussed, with special emphasis on the introduction of inorganic materials into polymeric networks and consequential changes in the properties of mechanical strength, swelling, and adsorption. Besides, hydrogels used as adsorbents for removal of dyes and inorganic pollutants have been widely explored, but their use for adsorbing emerging contaminants from aqueous solution has not received much attention. Thus, this review is mainly focused on hydrogels' application in removing emerging contaminants by adsorption. Furthermore, hydrogels can be also applied in immobilizing catalysts, such as enzyme and photocatalyst, to remove pollutants completely and avoid secondary pollution, so their progress as catalyst matrix is overviewed.

Response surface methodology directed synthesis of luminescent nanocomposite hydrogel for trapping anionic dyes

The present research work reveals semi-interpenetrating network (semi-IPN) synthesis using response surface methodology-central composite design (RSM-CCD) based optimization. The maximum swelling of 362.11% was obtained with monomer, crosslinker and initiator concentrations 4.39 mol L^-1, 1.52 mol L^-1 and 4.58 mol L^-1, respectively, temperature 70 °C, time 3 h and pH 4.0. The synthesized hydrogel showed 94.16% and 95.62% removal for eosin yellow (EY) and eriochrome black-T (EBT) dyes, respectively. The incorporation of cadmium sulphide nanodots into the hydrogel network enhanced the % dye removal (96.82% EY and 98.73% EBT) along with fluorescent behavior. Various conditions optimized for EY and EBT dye removal with respect to semi-IPN were: 0.4 g adsorbent dose each, dye concentrations 10 mg L^-1 and 120 mg L^-1, contact time 24 h each, respectively. Adsorption studies followed langmuir theory for both dyes. Second order and first order kinetics along with intraparticle diffusion of dye molecules were favorable to EY and EBT, respectively. Thermodynamic study reveals exothermic nature of adsorption. Recyclability of the adsorbent is superior as tested by desorption-adsorption tests.