Chemical modification of microcrystalline cellulose with polyethyleneimine and hydrazine: Characterization and evaluation of its adsorption power toward anionic dyes

Bio-based adsorption foam composed of MOF and polyethyleneimine-modified cellulose for selective anionic dye removal

With the increase of sustainable development goal, the bio-based adsorption materials with high and selective dye removal are important for water treatment in the dyeing industry. In this paper, a bio-based adsorption foam composed of metal-organic frameworks (MOF) and polyethyleneimine (PEI)-modified cellulose was prepared by a three-step process, i.e., PEI modification of cellulose fibers (PC), MOF decoration of PEI-modified cellulose (MIL-53@PC), and in-situ foaming with polyurethane. PEI modification provides cellulose fiber with more active sites for both dye adsorption and MOF bonding. We found that MIL-53 crystals were tightly bonded on the surface of PC through hydrogen bonding. Because of the abundant adsorption sites (e.g., amines, iron oxide group), the MIL-53@PC demonstrated high adsorption capacity and selectivity for anionic dye (e.g., 936.5 mg/g for methyl orange) through electrostatic interaction and hydrogen bonding. Finally, MIL-53@PC particles were blended with a waterborne polyurethane prepolymer to prepare a three-dimensional hydrophilic foam (MIL-53@PC/PUF), which not only maintained high adsorption capacity and selectivity of MIL-53@PC and also improved its recyclability and reusability. The MIL-53@PC/PUF offers a promising solution for dye wastewater treatment.

A colorimetric and fluorescent probe of lignocellulose nanofiber composite modified with Rhodamine 6G derivative for reversible, selective and sensitive detection of metal ions in wastewater

Heavy metal ions have extremely high toxicity. As the top of food chain, human beings certainly will accumulate them by ingesting food and participating other activities, which eventually result in the damage to our health. Therefore, it is very meaningful and necessary to design a simple, portable, stable and efficient material for heavy metal ions detection. Based on the spirolactam Rhodamine 6G (SRh6G) fluorescent probe, we prepared two types of nanocomposite materials (membrane and aerogel) by vacuum filtration and freeze-drying methods with lignocellulose nanofiber (CNF) as a carrier, polyvinyl alcohol (PVA) and glutaraldehyde (GA) as the cross-linkers. Then the microstructure, chemical composition, wetting property, fluorescence intensity and selectivity of as-prepared SRh6G/PVA/CNF would be characterized and analyzed. Results showed that SRh6G/PVA/CNF nanocomposites would turn red in color under strong acidic environment and produced orange fluorescence under ultraviolet light. Besides, they were also to detect Al3+, Cu2+, Hg2+, Fe3+ and Ag+ through color and fluorescence variations. We had further tested its sensitivity, selectivity, adsorption, fluorescence limits of detection (LOD) to Fe3+ and Cu2+. The test towards real water samples (hospital wastewater, Songhua River and tap water) proved that SRh6G/PVA/CNF nanocomposites could detect the polluted water with low concentrations of Fe3+ and Cu2+. In addition, SRh6G/PVA/CNF nanocomposites have excellent mechanical property, repeatability, superhydrophilicity and underwater superoleophobicity, which may offer a theoretical reference for the assembly strategy and detection application of cellulose-based fluorescent probe.

Design of low-cost natural casein biopolymer based adsorbent for efficient adsorption of multiple anionic dyes and diclofenac sodium from aqueous solutions

The treatment of various organic pollutants from industrial wastewater using bio-based materials has gained significant attention owing to their excellent properties such as low-cost, eco-friendly, non-toxic, and biodegradability. In this perspective, casein (Cn), a protein-based biopolymer, was extracted from the cow milk as a low-cost adsorbent, and the adsorption performances were determined for the pristine Cn. The adsorbent was employed for the removal of two different classes of targeted pollutant anionic dyes such as Congo red (CR), Eriochrome Black T (EBT), Eosin Y (EY), and pharmaceutical waste i.e., diclofenac sodium (DS) and displayed better adsorption performances with the maximum adsorption capacity of 85.54, 31.72, 70.42 and 358.42 mg g-1 respectively. The interactions between Cn and pollutants are mainly ascribed to the electrostatic interaction, hydrogen bonding, hydrophobic interaction, and π-π interactions. Furthermore, to validate with realistic application the adsorbent proved with an excellent removal efficiency of 91.43% for fabric whitener i.e., Ujala Supreme®. These obtained results suggest that the Cn could be the potential adsorbent to effectively eliminate toxic pollutants from the aqueous solutions.

Polyethyleneimine-functionalized magnetic sugarcane bagasse cellulose film for the efficient adsorption of ibuprofen

Polyethyleneimine-modified magnetic sugarcane bagasse cellulose film (P-SBC/Fe3O4 film) was simply fabricated for the removal of ibuprofen (IBP), a typical emerging organic contaminant. The P-SBC/Fe3O4 film exhibited an equilibrium adsorption amount of 370.52 mg/g for IBP and a corresponding removal efficiency of 92.63 % under following adsorption conditions: 318 K, pH 4, and 0.25 mg/mL dosage. Thermodynamic studies indicated that adsorption of IBP on the P-SBC/Fe3O4 film was spontaneous (∆G < 0) and endothermic (∆H > 0). The adsorption data conformed to the Freundlich isotherm model and multilayer adsorption model (two layers), and an average of 3-4 active sites on the P-SBC/Fe3O4 film share an IBP molecule. Both the EDR-IDR and AOAS models vividly described the dynamic characteristics of adsorption process. Model fitting results, theoretical calculations, and comprehensive characterization revealed that adsorption is driven by electrostatic interactions between the primary amine of P-SBC/Fe3O4 film and the carboxyl group of IBP molecule, while other weak interactions are also non-ignorable. Furthermore, quantitative calculations based on density functional theory (DFT) underscored the importance of PEI functionalization. In conclusion, P-SBC/Fe3O4 film is an environmentally friendly and cost-effective adsorbent with significant potential for effectively removing IBP, while maintaining its efficacy over multiple cycles.

Highly Efficient Biosorption of Cationic Dyes via Biopolymeric Adsorbent-Material-Based Pectin Extract Polysaccharide and Carrageenan Grafted to Cellulosic Nonwoven Textile

Water scarcity and contamination have emerged as critical global challenges, requiring the development of effective and sustainable solutions for the treatment of contaminated water. Recently, functionalized polymer biomaterials have garnered significant interest because of their potential for a wide range of water treatment applications. Accordingly, this paper highlights the design of a new adsorbent material based on a cellulosic nonwoven textile grafted with two extracted biopolymers. The layer-by-layer grafting technique was used for the polyelectrolyte multi-layer (PEM) biosorbent production. Firstly, we extracted a Suaeda fruticosa polysaccharide (SFP) and confirmed its pectin-like polysaccharide structure via SEC, NMR spectroscopy, and chemical composition analyses. Afterward, the grafting was designed via an alternating multi-deposition of layers of SFP polymer and carrageenan crosslinked with 1,2,3,4-butanetetracarboxylic acid (BTCA). FT-IR and SEM were used to characterize the chemical and morphological characteristics of the designed material. Chemical grafting via polyesterification reactions of the PEM biosorbent was confirmed through FT-IR analysis. SEM revealed the total filling of material microspaces with layers of grafted biopolymers and a rougher surface morphology. The assessment of the swelling behavior revealed a significant increase in the hydrophilicity of the produced adsorbent system, a required property for efficient sorption potential. The evaluation of the adsorption capabilities using the methylene blue (MB) as cationic dye was conducted in various experimental settings, changing factors such as the pH, time, temperature, and initial concentration of dye. For the untreated and grafted materials, the greatest adsorbed amounts of MB were 130.6 mg/g and 802.6 mg/g, respectively (pH = 4, T = 22 C, duration = 120 min, and dye concentration = 600 mg/L). The high adsorption performance, compared to other reported materials, was due to the presence of a large number of hydroxyl, sulfonate, and carboxylic functional groups in the biosorbent polymeric system. The adsorption process fitted well with the pseudo-first-order kinetic model and Langmuir/Temkin adsorption isotherms. This newly developed multi-layered biosorbent shows promise as an excellent adsorption resultant and cheap-cost/easy preparation alternative for treating industrial wastewater.

Novel soy protein isolate/sodium alginate-based functional aerogel for efficient uptake of organic dye from effluents

In response to the increasing global concern regarding water pollution, there is a growing demand for the development of novel adsorbents capable of effectively eliminating hazardous organic pollutants from effluents. In this study, we present a functional soy protein isolate (SPI)/sodium alginate (ALG)/polyethyleneimine (PEI) aerogel prepared via a facile chemical crosslinking process as a novel adsorbent with excellent capabilities for removing toxic methyl blue (MB) dye from effluents. Thanks to the synergistic dense oxygen and nitrogen-containing functional groups in the networks, the ALG/SPI/PEI (ASP) aerogel displayed high adsorption capacity for MB (106.3 mg/g) complying the adsorption kinetics and isotherm with the pseudo-second-order and Langmuir models, respectively. Remarkably, the MB adsorption capability of the ASP aerogel surpasses that of its pristine counterpart and outperforms recently reported adsorbents. Moreover, the aerogel maintained >80% of initial adsorption capability in the fourth regenerative cycle, indicating excellent reusability. The superior MB adsorbability coupled with high-efficiency regenerability in this study reveal the significant potential of ASP aerogel in efficiently eliminating organic dye from wastewater.

Aminothiol supported dialdehyde cellulose for efficient and selective removal of Hg(II) from aquatic solutions

The increasingly serious problem of mercury pollution has caused wide concern, and exploring adsorbent materials with high adsorption capacity is a simple and effective approach to address this concern. In the recent study, dialdehyde cellulose (DAC), cyanoacetohydrazide (CAH), and carbon disulfide (CS2) are used as raw materials for the (DAC@CAH@SK2) preparation material through the three-steps method. By utilizing the following characterization techniques; thermogravimetric analysis (TGA), N2 adsorption-desorption isotherm (BET), elemental analysis, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD), 1HNMR and Energy Dispersive X-ray Spectroscopy (EDS) of DAC@CAH@SK2 composite. The point of zero charge (pHPZC) for the prepared DAC@CAH@SK2 also was examined. From the batch experiments, the optimum conditions were found to be pH (5-8), an Hg2+ concentration of 150 mg/L, a DAC@CAH@SK2 dose of 0.01 g, and a contact time of 180 min with a maximum adsorption quantity of 139.6 mg/g. The process of Hg2+ adsorption on the DAC@CAH@SK2 material was spontaneous exothermic, monolayer chemisorption, and well-fitted to Langmuir and pseudo-2nd-order models. The DAC@CAH@SK2 selectivity towards the Hg2+ was examined by investigating the interfering metal ions effect. The DAC@CAH@SK2 was successfully applied for the Hg2+ removal from synthetic effluents and real wastewater samples with a recovery % exceeding 95%. The prepared DAC@CAH@SK2 was regenerated using a mixture of EDTA and thiourea. Also, FT-IR analysis indicates that the synergistic complexation of N and S atoms on DAC@CAH@SK2 with Hg(II) is an essential factor leading to the high adsorption capacity.

Schiff base synergized with protonation of PEI to achieve smart antibacteria of nanocellulose packaging films

Microbial growth and reproduction can cause food spoilage. Developing the controlled release packaging films for food is an ideal solution. In this study, polyethyleneimine (PEI) was grafted to cellulose nanofibers (CNF) films by Schiff base, and when the CNF/PEI films were stimulated by pH, PEI released from the CNF/PEI films due to Schiff base hydrolysis, improving the antibacterial efficiency of PEI. Stimulated by acid with pH of 4, the PEI cumulative release rate of the CNF/PEI₈₀₀ and the CNF/PEI₂₀₀₀ films reached to 92.90 % and 87.28 %, respectively. At the same time, the amino groups of PEI protonated by obtaining H⁺, the charge density increased, and PEI molecular chains extended, enhancing the antibacterial activity of films. The Zeta potential value on the surface of the CNF/PEI film increased with the decrease of pH value. Schiff base synergized with protonation of PEI to achieve smart antibacteria of CNF packaging films. The antibacterial rates of the film against L. monocytogenes and E. coli were 94.7 % and 90.6 % at pH 4, but 29.5 % and 23.6 % at pH 8, respectively. The developed films also had good barrier properties of oxygen, visible light and mechanical properties, and had an attractive application prospect in food preservation to control release of antibacterial agent.

A novel electrochemical aptasensor based on eco-friendly synthesized titanium dioxide nanosheets and polyethyleneimine grafted reduced graphene oxide for ultrasensitive and selective detection of ciprofloxacin

Developing a rapid, sensitive, and efficient analytical method for the trace-level determination of highly concerning antibiotic ciprofloxacin (CIP) is desirable to guarantee the safety of human health and ecosystems. In this work, a novel electrochemical aptasensor based on polyethyleneimine grafted reduced graphene oxide and titanium dioxide (rGO/PEI/TiO2) nanocomposite was constructed for ultrasensitive and selective detection of CIP. Through the in-situ electrochemical oxidation of Ti3C2Tx nanosheets, TiO2 nanosheets with good electrochemical response were prepared in a more convenient and eco-friendly method. The prepared TiO2 nanosheets promote charge transferring on electrode interface, and [Fe(CN)6]3-/4- as electrochemical active substance can be electrostatically attracted by rGO/PEI. Thus, electrochemical detection signal of the aptasensor variates a lot after specific binding with CIP, achieving working dynamic range of 0.003-10.0 μmol L-1, low detection limit down to 0.7 nmol L-1 (S/N = 3) and selectivity towards other antibiotics. Additionally, the aptasensor exhibited good agreement with HPLC method at 95% confidence level, and achieved good recoveries (96.8-106.3%) in real water samples, demonstrating its suitable applicability of trace detection of CIP in aquatic environment.

Fractionation of depectinated sugar beet pulp into cellulose, hemicellulose, and lignin with NaOH/urea/H2O and ionic liquid

This study proposes a novel and feasible dissolution and fractionation method of depectinated sugar beet pulp (SBP) in NaOH/Urea/H₂O, ionic liquid (IL) and alkaline treatment processes. Interestingly, the complicated structure of SBP can be treated with 30 % H₂SO₄ to increase the dissolution rate. Scanning electron microscope (SEM) analysis confirmed that the appearance of cellulose and hemicellulose obtained by two methods were different. At the same time, two lignin fractions showed irregular high-density clusters, which were composed of a large number of submicron particles. The crystal structure of two cellulose fractions changed from cellulose I to cellulose II. The thermal stability of cellulose and lignin obtained by ionic liquid was slightly better than that obtained by NaOH/urea/H₂O. Results of Fourier transform infrared (FTIR) and ¹³C NMR showed that the chemical structures of SBP cellulose, hemicellulose and lignin regenerated from NaOH/urea/H₂O and ionic liquid were similar.