Ionic chitosan/silica nanocomposite as efficient adsorbent for organic dyes

Chitosan and silica nanoparticles-modified xanthan gum-derived bio-nanocomposite hydrogel film for efficient uptake of methyl orange acidic dye

In this contribution, a bio-nanocomposite hydrogel film (CS/XG.SiO2) of chitosan/silica NPs-modified xanthan gum was prepared via a facile solution casting blending approach and utilized to capture the anionic methyl orange (MO) from aqueous solution. A Taguchi standard method was used to optimize the hydrogel nanocomposite synthesis reaction conditions after comprehensive characterization using various techniques. Under various operating parameters, the hydrogel biofilm was tested for its effectiveness in adsorbing MO dye in a batch process. In agreement with Langmuir isotherm, the CS/XG.SiO2 biofilm was capable of adsorbing MO at a maximum capacity of 294 mg/g at pH 5.30, contact time 45 min, temperature 25 °C, and concentration (C0) 50 mg/L. Pseudo-second-order model and adsorption kinetics data well matched. The thermodynamic data indicate that adsorption occurred spontaneously and exothermically. The main mechanisms driving the adsorption are electrostatic interactions and hydrogen bonding between the CS/XG.SiO2 nanocomposite and the dye. Furthermore, the biofilm is regenerative, allowing for up to five reuses while maintaining a 75 % dye removal efficiency. This study highlights that the CS/XG.SiO2 hydrogel nanocomposite is an inexpensive, reusable, and eco-friendly bio-adsorbent that is capable of anionic dye adsorption.

Agro-Waste Valorization into Carbonaceous Eco-Hydrogel: A Circular Economy and Zero Waste Tactic for Doxorubicin Removal in Water/Wastewater

The existing work aims to evaluate the efficiency of eco-hydrogel for adsorption of pollutants prepared from biopolymeric matrix and agricultural waste-derived biochar. An efficient and reusable adsorbent, designed from the integration of maize stalk activated carbon into a gelatin-alginate composite (MSAC@GE-SA) was explored for removal of doxorubicin hydrochloride (Doxo.HCL) from polluted water. The structural properties, presence of surface functional groups, and elemental composition were explored using XRD, SEM, BET, FTIR, and XPS techniques. The key adsorption parameters such as Doxo.HCL concentration, MSAC@GE-SA amount, solution pH, and the contact time between adsorbate and adsorbents were successfully optimized for the effective removal of Doxo.HCL (qmax = 239.41 mg g-1). The kinetic mechanism of MSAC@GE-SA fits well with a pseudo-second-order rate model (R2 = 0.980), followed by mono- and multilayered Langmuir and Freundlich isotherms with R2 values 0.991 and 0.993, respectively. The recyclability of MSAC@GE-SA showed great stability without any physical damage and having sustained removal efficiency up to 10 cycles (96.32 to 55.66%). The versatility of MSAC@GE-SA was further investigated for river, canal, and sewage water samples under identical experimental conditions. The practicality of the MSAC@GE-SA was evaluated by spiking Doxo.HCL into industrial effluents via the standard addition method. Subsequently, the chemical oxygen demand (COD) of the treated pollutants exhibited a notable reduction, decreasing significantly from 128 to 80 mg L-1. Following 10 successful adsorption-desorption cycles, the spent MSAC@GE-SA was utilized as a fertilizer for Vigna radiata plants, positively contributing to overall plant growth without causing harm. Hence, proposed adsorbent (MSAC@GE-SA) emerges as a viable and sustainable solution, demonstrating features of reusability and cost-effectiveness. It holds significant promise for the removal of pharmaceutical pollutants, aligning with the principles of circular economy and zero-waste tactics.

Chitosan-polyvinyl alcohol-diatomite hydrogel removes methylene blue from water

Dye pollution in the aquatic environment can harm ecosystems and human health. Here, we developed a new green adsorbent by applying an improved drying process. Diatomite was embedded in a network structure formed between chitosan and polyvinyl alcohol without using any crosslinking agent to prepare chitosan-polyvinyl alcohol-diatomite hydrogel beads through alkali solidification. The beads were tested for removing a cationic dye (methylene blue (MB)) from water. The structure of the adsorbent beads was analysed using scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy. The adsorption capacity was investigated, and the results indicated excellent MB adsorption properties. The adsorbents had a rough surface and high swelling capacity of 66.9 g/g. The maximum MB adsorption capacity was 414.70 mg/g, and the adsorption followed the Freundlich isothermal and quasi-second-order kinetic models. The adsorption was an endothermic spontaneous process governed by both intra-particle and external diffusion processes. The proposed adsorption mechanisms involved hydrogen bonding and electrostatic interactions. These adsorbent beads have considerable application potentials owing to their high adsorption capacity, green composition, and non-polluting nature.

Synthesis and adsorption performance of functionalized chitosan and carboxyethylsilanetriol hybrids

A novel adsorbent from cationic chitosan derivative and anionic silica precursor was fabricated to remove methylene blue (MB). The hybrid material was prepared from N-guanidinium chitosan acetate (GChi) and carboxyethylsilanetriol sodium salt by a simple ionic interaction followed by sol-gel approach. Multiple characterization methods were used to analyze the morphology and the structure of the well-prepared functionalized material. Batch experiments were conducted to optimize the various operational parameters. The Langmuir isotherm was used to fit the data, and it predicted monolayer adsorption with a maximum capacity of 334 mg g^-1. A pseudo-second-order equation fit the adsorption process well. Chitosan/silica hybrids containing carboxylic groups are efficient and cost-effective adsorbents for cationic dyes adsorption from aqueous solutions.

Recent advances in nanomaterials based sustainable approaches for mitigation of emerging organic pollutants

Emerging organic pollutants (EOPs) are a category of pollutants that are relatively new to the environment and recently garnered a lot of attention. The majority of EOPs includes endocrine-disrupting chemicals (EDCs), antibiotic resistance genes (ARGs), pesticides, dyes and pharmaceutical and personal care products (PPCPs). Exposure to contaminated water has been linked to an increase in incidences of malnutrition, intrauterine growth retardation, respiratory illnesses, liver malfunctions, eye and skin diseases, and fatalities. Consequently, there is a critical need for wastewater remediation technologies which are effective, reliable, and economical. Conventional wastewater treatment methods have several shortcomings that can be addressed with the help of nanotechnology. Unique characteristics of nanomaterials (NMs) make them intriguing and efficient alternative in wastewater treatment strategies. This review emphasis on the occurrence of divers emerging organic pollutants (EOPs) in water and their effective elimination via different NMs based methods with in-depth mechanisms. Furthermore, it also delves the toxicity assessment of NMs and critical challenges, which are crucial steps for practical implementations.

Fabrication of a dual pH-responsive and photothermal microcapsule pesticide delivery system for controlled release of pesticides

BACKGROUND

The development of stimulus-responsive and photothermally controlled-release microcapsule pesticide delivery systems is a promising solution to enhance the effective utilization and minimize the excessive use of pesticides in agriculture.

RESULTS

In this study, an AVM@CS@TA-Fe microcapsule pesticide delivery system was developed using avermectin as the model drug, chitosan and tannic acid as the wall materials, and tannic acid-Fe complex layer as the photothermal agent. The optical microscope, scanning electron microscope, transmission electron microscope, and Fourier-transform infrared spectroscope were used to characterize the prepared microcapsule. The slow-release, UV-shielding, photothermal performance, and nematicidal activity of the microcapsule were systematically investigated. The results showed that the system exhibited excellent pH-responsive and photothermal-sensitive performances. In addition, the UV-shielding performance of the delivery system was improved. The photothermal conversion efficiency (η) of the system under the irradiation of near-infrared (NIR) light was determined to be 14.18%. Moreover, the nematicidal activities of the system against pine wood nematode and Aphelenchoides besseyi were greatly increased under the irradiation of light-emitting diode (LED) simulated sunlight.

CONCLUSION

The release of the pesticide-active substances in such a pesticide delivery system could be effectively regulated with the irradiation of NIR light or LED-simulated sunlight. Thus, the developed pesticide delivery system may have broad application prospects in modern agriculture fields. © 2022 Society of Chemical Industry.

Synthesis of hyperbranched polyamine dendrimer/chitosan/silica composite for efficient adsorption of Hg(II)

The pollution of water system with Hg(II) exerts hazardous effect to ecosystem and public health. Adsorption is considered to be a promising strategy to remove Hg(II) from aqueous solution. Herein, hyperbranched polyamine dendrimer/chitosan/silica composite (SiO₂-FP) was synthesized for the adsorption of aqueous Hg(II). The adsorption performance of SiO₂-FP was comprehensively determined by considering various influencing factors. SiO₂-FP displays good adsorption performance for Hg(II) with the adsorption capacity of 0.79 mmol·g^-1, which is higher than the corresponding chitosan functionalized silica (SiO₂-CTS) by 46.30 %. The optimal solution pH for the adsorption of Hg(II) is 6. Adsorption kinetic indicates the adsorption for Hg(II) can reach equilibrium at 250 min. Adsorption kinetic process can be well fitted by pseudo-second-order (PSO). Adsorption isotherm reveals the adsorption for Hg(II) can be promoted by increasing initial Hg(II) concentration and adsorption temperature. The adsorption isotherm indicates the adsorption process can be described by Langmuir model and the adsorption is a spontaneous, endothermic and entropy-increased process. SiO₂-FP displays excellent adsorption selectivity and can 100 % adsorb Hg(II) with the coexisting of Ni(II), Zn(II), Pb(II), Mn(II), and Co(II). Adsorption mechanism demonstrates -NH-, -NH₂, CN, CONH, -OH, and CO participated in the adsorption. SiO₂-FP exhibits good regeneration property and the regeneration rate can maintain approximately 90 % after five adsorption-desorption cycles.

A magnetically recyclable lignin-based bio-adsorbent for efficient removal of Congo red from aqueous solution

It has been always attractive to design a sustainable bio-derived adsorbent based on industrial waste lignin for removing organic dyes from water. However, existing adsorbent strategies often lead to the difficulties in adsorbent separation and recycling. Herein, we report a novel magnetically recyclable bio-adsorbent of Mg(OH)₂/Fe₃O₄/PEI functionalized enzymatic lignin (EL) composite (EL-PEI@Fe₃O₄-Mg) for removing Congo red (CR) by Mannish reaction and hydrolysis-precipitation. The Mg(OH)₂ and PEI functionalized EL on the surface act as active sites for the removal of CR, while the Fe₃O₄ allows for the easy separation under the help of a magnet. As-obtained EL-PEI@Fe₃O₄-Mg forms flower-like spheres and has a relatively lager surface area of 24.8 m² g^-1 which is 6 times that of EL. The EL-PEI@Fe₃O₄-Mg exhibits a relatively high CR adsorption capacity of 74.7 mg g^-1 which is 15 times that of EL when initial concentration is around 100 mg L^-1. And it can be easily separated from water by applying an external magnetic field. Moreover, EL-PEI@Fe₃O₄-Mg shows an excellent anti-interference capability according to the results of pH values and salt ions influences. Importantly, EL-PEI@Fe₃O₄-Mg possesses a good reusability and a removal efficiency of 92 % for CR remains after five consecutive cycles. It is illustrated that electrostatic attraction, π-π interaction and hydrogen binding are primary mechanisms for the removal of CR onto EL-PEI@Fe₃O₄-Mg. This work provides a novel sustainable strategy for the development of highly efficient, easy separable, recyclability bio-derived adsorbents for removing organic dyes, boosting the efficient utilization of industrial waste lignin.

A Novel P@SiO2 Nano-Composite as Effective Adsorbent to Remove Methylene Blue Dye from Aqueous Media

This work aims to prepare a novel phosphate-embedded silica nanoparticles (P@SiO₂) nanocomposite as an effective adsorbent through a hydrothermal route. Firstly, a mixed solution of sodium silicate and sodium phosphate was passed through a strong acidic resin to convert it into hydrogen form. After that, the resultant solution was hydrothermally treated to yield P@SiO₂ nanocomposite. Using kinetic studies, methylene blue (MB) dye was selected to study the removal behavior of the P@SiO₂ nanocomposite. The obtained composite was characterized using several advanced techniques. The experimental results showed rapid kinetic adsorption where the equilibrium was reached within 100 s, and the pseudo-second-order fitted well with experimental data. Moreover, according to Langmuir, one gram of P@SiO₂ nanocomposite can remove 76.92 mg of the methylene blue dye. The thermodynamic studies showed that the adsorption process was spontaneous, exothermic, and ordered at the solid/solution interface. Finally, the results indicated that the presence of NaCl did not impact the adsorption behavior of MB dye. Due to the significant efficiency and promising properties of the prepared P@SiO₂ nanocomposite, it could be used as an effective adsorbent material to remove various cationic forms of pollutants from aqueous solutions in future works.

Coupling of 3-Aminopropyl Sulfonic Acid to Cellulose Nanofibers for Efficient Removal of Cationic Dyes

A novel anionic nanostructured cellulose derivate was prepared through the coupling of TEMPO-oxidized cellulose nanofibers with 3-aminopropyl sulfonic acid (3-APSA). 3-APSA grafting was variously investigated by FT-IR spectroscopy and transmission electron microscopy (TEM) analysis, confirming a high reaction degree. The surface morphology investigated via scanning electron microscopy (SEM) revealed a more uniform organization of the nanofibers after the 3-APSA coupling, with improvements in terms of fiber packing and pore interconnectivity. This peculiar morphology contributes to improving methylene blue (MB) adsorption and removal efficiency at different operating conditions (pH, initial time, and initial concentration). The results indicated a maximum adsorption capacity of 526 mg/g in the case of 3-APSA grafted nanofibers, over 30% more than that of non-grafted ones (370 mg/g), which confirm a relevant effect of chemical modification on the adsorbent properties of cellulose nanofibers. The adsorption kinetics and isotherms of the current adsorbents match with the pseudo-second-order kinetic and Langmuir isotherm models. This study suggests the use of chemical grafting via 3-APSA is a reliable and facile post-treatment to design bio-sustainable and reusable nanofibers to be used as high-performance adsorbent materials in water pollutant remediation.

Efficiency of air-dried and freeze-dried alginate/xanthan beads in batch, recirculating and column adsorption processes

Alginate (Alg) beads are low-cost adsorbents used for wastewater remediation. In this work, alginate (Alg) and alginate/xanthan (Alg/XG) blend beads were synthesized by gelation method into calcium chloride and freeze-dried to improve the porosity. Their adsorption efficiency was tested for methylene blue (MB) dye in batch, recirculating and column adsorption systems. The blend beads were characterized using by SEM, FTIR-ATR and X-ray microcomputer tomography (Micro-CT) analyzes. Freeze-dried Alg and Alg/XG beads presented porosity of 46 ± 5% and 77 ± 3%, respectively. Adsorption isotherms of MB on freeze-dried Alg/XG beads indicated better adsorption capacity in comparison to the air-dried ones. Adsorption kinetics and breakthrough curves based on recirculating and vertical column adsorption processes of MB on freeze dried Alg/XG and air-dried Alg/XG beads indicated higher efficiency for the vertical column system packed with freeze dried Alg/XG beads. The removal efficiency of 91% MB by the freeze-dried Alg/XG beads in vertical column remained even after four consecutive adsorption-desorption cycles, disclosing these beads as potential systems for the wastewater treatment.

Synthesis of glutaraldehyde-modified silica/chitosan composites for the removal of water-soluble diclofenac sodium

Composite materials are effective adsorbents for the removal of various types of contaminants, such as pharmaceutical products. However, they require improvement to achieve a good adsorption capacity. This study presents the development of a promising adsorbent: silica/chitosan modified with different proportions of glutaraldehyde, which involves the D-glucosamine units from chitosan. The developed materials were evaluated for their ability to remove diclofenac sodium. The adsorption data showed that the diclofenac adsorption efficiency increased with increasing degree of glutaraldehyde crosslinking. The equilibrium and kinetic data were well fit by the Liu and Elovich models, respectively, and the maximum adsorption capacity was 237.8 mg/g. Therefore, it can be assumed that the process is predominantly chemical and exothermic, with a high affinity between the adsorbents and diclofenac sodium. The adsorption mechanisms were investigated to better understand the interactions, and the predominance of covalent bonds with the self-polymerized glutaraldehyde was verified.

Mesoporous maltose/calcium oxalate hybrid material with abundant reaction sites and its efficient Pb(ii) removal from diverse water bodies

Maltose/calcium oxalate exhibits high capacity and selective adsorption of Pb(ii) due to the synergistic mechanism of ion exchange, electrostatic and complexation.

Nanocellulose-Based Materials for Water Treatment: Adsorption, Photocatalytic Degradation, Disinfection, Antifouling, and Nanofiltration

Nanocelluloses are promising bio-nano-materials for use as water treatment materials in environmental protection and remediation. Over the past decades, they have been integrated via novel nanoengineering approaches for water treatment processes. This review aims at giving an overview of nanocellulose requirements concerning emerging nanotechnologies of waster treatments and purification, i.e., adsorption, absorption, flocculation, photocatalytic degradation, disinfection, antifouling, ultrafiltration, nanofiltration, and reverse osmosis. Firstly, the nanocellulose synthesis methods (mechanical, physical, chemical, and biological), unique properties (sizes, geometries, and surface chemistry) were presented and their use for capturing and removal of wastewater pollutants was explained. Secondly, different chemical modification approaches surface functionalization (with functional groups, polymers, and nanoparticles) for enhancing the surface chemistry of the nanocellulose for enabling the effective removal of specific pollutants (suspended particles, microorganisms, hazardous metals ions, organic dyes, drugs, pesticides fertilizers, and oils) were highlighted. Thirdly, new fabrication approaches (solution casting, thermal treatment, electrospinning, 3D printing) that integrated nanocelluloses (spherical nanoparticles, nanowhiskers, nanofibers) to produce water treatment materials (individual composite nanoparticles, hydrogels, aerogels, sponges, membranes, and nanopapers) were covered. Finally, the major challenges and future perspectives concerning the applications of nanocellulose based materials in water treatment and purification were highlighted.