Ultrafine Cellulose Nanofibers as Efficient Adsorbents for Removal of UO22+ in Water

Cellulose-based materials in environmental protection: A scientometric and visual analysis review

As sustainable materials, cellulose-based materials have attracted significant attention in the field of environmental protection, resulting in the publication of numerous academic papers. However, there is a scarcity of literature that involving scientometric analysis within this specific domain. This review aims to address this gap and highlight recent research in this field by utilizing scientometric analysis and a historical review. As a result, 21 highly cited articles and 10 mostly productive journals were selected out. The scientometric analysis reveals that recent studies were objectively clustered into five interconnected main themes: extraction of cellulose from raw materials and its degradation, adsorption of pollutants using cellulose-based materials, cellulose-acetate-based membrane materials, nanocellulose-based materials, and other cellulose-based materials such as carboxymethyl cellulose and bacterial cellulose for environmental protection. Analyzing the distribution of author keywords and thoroughly examining relevant literature, the research focuses within these five themes were summarized. In the future, the development of eco-friendly and cost-effective methods for extracting and preparing cellulose and its derivatives, particularly nanocellulose-based materials, remains an enduring pursuit. Additionally, machine learning techniques holds promise for the advancement and application of cellulose-based materials. Furthermore, there is potential to expand the research and application scope of cellulose-based materials for environmental protection.

Amidoxime-grafted cotton fibers with anti-microbial sludge for efficient uranium recovery

Uranium as a nuclear fuel, its source and aftertreatment has been a hot topic of debate for developers. In this paper, amidoxime and guanidino-modified cotton fibers (DC-AO-PHMG) were synthesized by the two-step functionalization approach, which exhibited remarkable antimicrobial and high uranium recovery property. Adsorption tests revealed that DC-AO-PHMG had excellent selectivity and anti-interference properties, the maximum adsorption capacity of 609.75 mg/g. More than 85 % adsorption capacity could still be kept after 10 adsorption-desorption cycles, and it conformed to the pseudo-second-order kinetic model and the Langmuir adsorption isotherm model as a spontaneous heat-absorbing chemical monolayer process. FT-IR, EDS and XPS analyses speculated that the amidoxime and amino synergistically increased the uranium uptake. The inhibitory activities of DC-AO-PHMG against three aquatic bacteria, BEY, BEL (from Yellow River water and lake bottom silt, respectively) and B. subtilis were significantly stronger, and the uranium adsorption was not impacted by the high bacteria content. Most importantly, DC-AO-PHMG removed up to 94 % of uranium in simulated seawater and extracted up to 4.65 mg/g of uranium from Salt Lake water, which demonstrated its great potential in the field of uranium resource recovery.

Recent advances in TEMPO-oxidized cellulose nanofibers: Oxidation mechanism, characterization, properties and applications

Cellulose is the richest renewable polymer source on the earth. TEMPO-mediated oxidized cellulose nanofibers are deduced from enormously available wood biomass and functionalized with carboxyl groups. The preparation procedure of TOCNFs is more environmentally friendly compared to other cellulose, for example, MFC and CNCs. Due to the presence of functional carboxyl groups, TOCNF-based materials have been studied widely in different fields, including biomedicine, wastewater treatment, bioelectronics and others. In this review, the TEMPO oxidation mechanism, the properties and applications of TOCNFs are elaborated. Most importantly, the recent advanced applications and the beneficial role of TOCNFs in the various abovementioned fields are discussed. Furthermore, the performances and research progress on the fabrication of TOCNFs are summarized. It is expected that this timely review will help further research on the invention of novel material from TOCNFs and its applications in different advanced fields, including biomedicine, bioelectronics, wastewater treatment, and the energy sector.

Quantitative Determination of Metal Ion Adsorption on Cellulose Nanocrystals Surfaces

Nanocellulose is a bio-based material that holds significant potential in the field of water purification. Of particular interest is their potential use as a key sorbent material for the removal of metal ions from solution. However, the structure of metal ions adsorbed onto cellulose surfaces is not well understood. The focus of this work is to determine quantitatively the three-dimensional distribution of metal ions of different valencies surrounding negatively charged carboxylate functionalized cellulose nanocrystals (CNCs) using anomalous small-angle X-ray scattering (ASAXS). These distributions can affect the water and ionic permeability in these materials. The data show that increasing the carboxylate density on the surface of the CNCs from 740 to 1100 mmol/kg changed the nature of the structure of the adsorbed ions from a monolayer into a multilayer structure. The monolayer was modeled as a Stern layer around the CNC nanoparticles, whereas the multilayer structure was modeled as a diffuse layer on top of the Stern layer around the nanoparticles. Within the Stern layer, the maximum ion density increases from 1680 to 4350 mmol of Rb+/(kg of CNC) with the increase in the carboxylate density on the surface of the nanoparticles. Additionally, the data show that CNCs can leverage multiple mechanisms, such as electrostatic attraction and the chaotropic effect, to adsorb ions of different valencies. By understanding the spatial organization of the adsorbed metal ions, the design of cellulose-based sorbents can be further optimized to improve the uptake capacity and selectivity in separation applications.

Nanocellulose: A comprehensive review investigating its potential as an innovative material for water remediation

Rapid growth in industrialization sectors, the wastewater treatment plants become exhausted and potentially not able to give desirable discharge standards. Many industries discharge the untreated effluent into the water bodies which affects the aquatic diversity and human health. The effective disposal of industrial effluents thus has been an imperative requirement. For decades nanocellulose based materials gained immense attraction towards application in wastewater remediation and emerged out as a new biobased nanomaterial. It is light weighted, cost effective, mechanically strong and easily available. Large surface area, versatile surface functionality, biodegradability, high aspect ratio etc., make them suitable candidate in this field. Majorly cellulose based nanomaterials are used in the form of cellulose nanocrystals (CNCs), cellulose nanofibers (CNFs), or bacterial nanocellulose (BNC). This review specifically describes about a variety of extraction methods to produced nanocellulose and also discusses the modification of nanocellulose by adding functionalities in its surface chemistry. We majorly focus on the utilization of nanocellulose based materials in water remediation for the removal of different contaminants such as dyes, heavy metals, oil, microbial colony etc. This review mainly emphasizes in ray of hope towards nanocellulose materials to achieve more advancement in the water remediation fields.

Recent advancement in nanomaterials for the detection and removal of uranium: A review

Uranyl ions U(VI), are the common by-product of nuclear power plants and anthropogenic activities like mining, excess utilization of fertilizers, oil industries, etc. Its intake into the body causes serious health concerns such as liver toxicity, brain damage, DNA damage and reproductive issues. Therefore, there is urgent need to develop the detection and remediation strategies. Nanomaterials (NMs), due to their unique physiochemical properties including very high specific area, tiny sizes, quantum effects, high chemical reactivity and selectivity have become emerging materials for the detection and remediation of these radioactive wastes. Therefore, the current study aims to provide a holistic view and investigation of these new emerging NMs that are effective for the detection and removal of Uranium including metal nanoparticles, carbon-based NMs, nanosized metal oxides, metal sulfides, metal-organic frameworks, cellulose NMs, metal carbides/nitrides, and carbon dots (CDs). Along with this, the production status, and its contamination data in food, water, and soil samples all across the world are also complied in this work.

Electrospun nanofiber membrane diameter prediction using a combined response surface methodology and machine learning approach

Despite the widespread interest in electrospinning technology, very few simulation studies have been conducted. Thus, the current research produced a system for providing a sustainable and effective electrospinning process by combining the design of experiments with machine learning prediction models. Specifically, in order to estimate the diameter of the electrospun nanofiber membrane, we developed a locally weighted kernel partial least squares regression (LW-KPLSR) model based on a response surface methodology (RSM). The accuracy of the model's predictions was evaluated based on its root mean square error (RMSE), its mean absolute error (MAE), and its coefficient of determination (R²). In addition to principal component regression (PCR), locally weighted partial least squares regression (LW-PLSR), partial least square regression (PLSR), and least square support vector regression model (LSSVR), some of the other types of regression models used to verify and compare the results were fuzzy modelling and least square support vector regression model (LSSVR). According to the results of our research, the LW-KPLSR model performed far better than other competing models when attempting to forecast the membrane's diameter. This is made clear by the much lower RMSE and MAE values of the LW-KPLSR model. In addition, it offered the highest R² values that could be achieved, reaching 0.9989.

Agricultural Residues as Raw Materials for Pulp and Paper Production: Overview and Applications on Membrane Fabrication

The need for pulp and paper has risen significantly due to exponential population growth, industrialization, and urbanization. Most paper manufacturing industries use wood fibers to meet pulp and paper requirements. The shortage of fibrous wood resources and increased deforestation are linked to the excessive dependence on wood for pulp and paper production. Therefore, non-wood substitutes, including corn stalks, sugarcane bagasse, wheat, and rice straw, cotton stalks, and others, may greatly alleviate the shortage of raw materials used to make pulp and paper. Non-woody raw materials can be pulped easily using soda/soda-AQ (anthraquinone), organosolv, and bio-pulping. The use of agricultural residues can also play a pivotal role in the development of polymeric membranes separating different molecular weight cut-off molecules from a variety of feedstocks in industries. These membranes range in applications from water purification to medicinal uses. Considering that some farmers still burn agricultural residues on the fields, resulting in significant air pollution and health issues, the use of agricultural residues in paper manufacturing can eventually help these producers to get better financial outcomes from the grown crop. This paper reviews the current trends in the technological pitch of pulp and paper production from agricultural residues using different pulping methods, with an insight into the application of membranes developed from lignocellulosic materials.

Nanocellulose-Based Adsorbents for Heavy Metal Ion

Heavy metal ions in industrial sewage constitute a serious threat to human health. Nanocellulose-based adsorbents are emerging as an environmentally friendly material platform for heavy metal ion removal based on their unique properties, which include high specific surface area, excellent mechanical properties, and biocompatibility. In this review, we cover the most recent works on nanocellulose-based adsorbents for heavy metal ion removal and present an in-depth discussion of the modification technologies for nanocellulose in the process of assembling high-performance heavy ion adsorbents. By introducing functional groups, such as amino, carboxyl, aldehyde, and thiol, the assembled nanocellulose-based adsorbents both remove single heavy metal ions and can selectively adsorb multiple heavy ions in water. Finally, the remaining challenges of nanocellulose-based adsorbents are pointed out. We anticipate that this review will provide indispensable guidance on the application of nanocellulose-based adsorbents for the removal of heavy metal ions.

Effective Thallium(I) Removal by Nanocellulose Bioadsorbent Prepared by Nitro-Oxidation of Sorghum Stalks

Thallium(I) (Tl(I)) pollution has become a pressing environmental issue due to its harmful effect on human health and aquatic life. Effective technology to remove Tl(I) ions from drinking water can offer immediate societal benefits especially in the developing countries. In this study, a bio-adsorbent system based on nitro-oxidized nanocellulose (NOCNF) extracted from sorghum stalks was shown to be a highly effective Tl(I) removal medium. The nitro-oxidation process (NOP) is an energy-efficient, zero-waste approach that can extract nanocellulose from any lignocellulosic feedstock, where the effluent can be neutralized directly into a fertilizer without the need for post-treatment. The demonstrated NOCNF adsorbent exhibited high Tl(I) removal efficiency (>90% at concentration < 500 ppm) and high maximum removal capacity (Qm = 1898 mg/g using the Langmuir model). The Tl(I) adsorption mechanism by NOCNF was investigated by thorough characterization of NOCNF-Tl floc samples using spectroscopic (FTIR), diffraction (WAXD), microscopic (SEM, TEM, and AFM) and zeta-potential techniques. The results indicate that adsorption occurs mainly due to electrostatic attraction between cationic Tl(I) ions and anionic carboxylate groups on NOCNF, where the adsorbed Tl(I) sites become nuclei for the growth of thallium oxide nanocrystals at high Tl(I) concentrations. The mineralization process enhances the Tl(I) removal efficiency, and the mechanism is consistent with the isotherm data analysis using the Freundlich model.

Recent advances and future perspective on nanocellulose-based materials in diverse water treatment applications

Over the past few years, nanocellulose and its derivatives have drawn attention as promising bio-based materials for water treatment applications due to their high surface area, high strength, and renewable, biocompatible nature. The abundance of hydroxyl functional groups on the surfaces of cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) enables a broad range of surface modifications which results in propitious nanocomposites with tunable characteristics. In this context, this review describes the continuously developing applications of nanocellulose-based materials in the areas of adsorption, catalysis, filtration, and flocculation, with a special emphasis on the removal of contaminants such as heavy metals, dyes, and pharmaceutical compounds from diverse water systems. Recent progresses in the diverse forms of application of nanocellulose adsorbents (suspension, hydrogel, aerogel, and membrane) are also highlighted. Finally, challenges and future perspectives on emerging nanocellulose-based materials and their possible industrial applications are presented and discussed.

Nanocellulose as a promising substrate for advanced sensors and their applications

Nanocellulose has broad and promising applications owing to its low density, large specific surface area, high mechanical strength, modifiability, renewability. Recently, nanocellulose has been widely used to fabricate flexible, durable and environmental-friendly sensor substrates. In this contribution, the construction and characteristics of nanocellulose-based sensors are comprehensively reviewed. Various nanocellulose-based sensors are summarized and divided into colorimetric, fluorescent, electronic, electrochemical and SERS types according to the sensing mechanism. This review also introduces the applications of nanocellulose-based sensors in the fields of biomedicine, environmental monitoring, food safety, and wearable devices.

Nanocellulose for Sustainable Water Purification

Nanocelluloses (NC) are nature-based sustainable biomaterials, which not only possess cellulosic properties but also have the important hallmarks of nanomaterials, such as large surface area, versatile reactive sites or functionalities, and scaffolding stability to host inorganic nanoparticles. This class of nanomaterials offers new opportunities for a broad spectrum of applications for clean water production that were once thought impractical. This Review covers substantial discussions based on evaluative judgments of the recent literature and technical advancements in the fields of coagulation/flocculation, adsorption, photocatalysis, and membrane filtration for water decontamination through proper understanding of fundamental knowledge of NC, such as purity, crystallinity, surface chemistry and charge, suspension rheology, morphology, mechanical properties, and film stability. To supplement these, discussions on low-cost and scalable NC extraction, new characterizations including solution small-angle X-ray scattering evaluation, and structure-property relationships of NC are also reviewed. Identifying knowledge gaps and drawing perspectives could generate guidance to overcome uncertainties associated with the adaptation of NC-enabled water purification technologies. Furthermore, the topics of simultaneous removal of multipollutants disposal and proper handling of post/spent NC are discussed. We believe NC-enabled remediation nanomaterials can be integrated into a broad range of water treatments, greatly improving the cost-effectiveness and sustainability of water purification.

Cellulose Nanomaterials as a Future, Sustainable and Renewable Material

Cellulose nanomaterials (CNs) are renewable, bio-derived materials that can address not only technological challenges but also social impacts. This ability results from their unique properties, for example, high mechanical strength, high degree of crystallinity, biodegradable, tunable shape, size, and functional surface chemistry. This minireview provides chemical and physical features of cellulose nanomaterials and recent developments as an adsorbent and an antimicrobial material generated from bio-renewable sources.

Nanoarchitectonics for High Adsorption Capacity Carboxymethyl Cellulose Nanofibrils-Based Adsorbents for Efficient Cu2+ Removal

In the present study, carboxymethyl cellulose nanofibrils (CMCNFs) with different carboxyl content (0.99-2.01 mmol/g) were prepared via controlling the ratio of monochloroacetic acid (MCA) and sodium hydroxide to Eucalyptus bleached pulp (EBP). CMCFs-PEI aerogels were obtained using the crosslinking reaction of polyethyleneimine (PEI) and CMCNFs with the aid of glutaraldehyde (GA). The effects of pH, contact time, temperature, and initial Cu2+ concentration on the Cu2+ removal performance of CMCNFs-PEI aerogels was highlighted. Experimental data showed that the maximum adsorption capacity of CMCNF30-PEI for Cu2+ was 380.03 ± 23 mg/g, and the adsorption results were consistent with Langmuir isotherm (R2 > 0.99). The theoretical maximum adsorption capacity was 616.48 mg/g. After being treated with 0.05 M EDTA solution, the aerogel retained an 85% removal performance after three adsorption-desorption cycles. X-ray photoelectron spectroscopy (XPS) results demonstrated that complexation was the main Cu2+ adsorption mechanism. The excellent Cu2+ adsorption capacity of CMCNFs-PEI aerogels provided another avenue for the utilization of cellulose nanofibrils in the wastewater treatment field.

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.

Potential of nanocellulose for wastewater treatment

Wastewater management has significant interest worldwide to establish viable treatment techniques to ensure the availability of clean water. The specialities of nanocellulose for this particular application is due to their high aspect ratio and accessibility of plenty of -OH groups for binding with dyes, heavy metals and other pollutants. This review aggregates the application of nanocellulose for wastewater treatment particularly as adsorbents of dyes and heavy metals, and also as membranes for filtering various other contaminants including microbes. The membrane technologies are proven to be effective relating to their durability and separation effectiveness. The commercial scale application of nanocellulose based materials in water treatment processes depend on various factors like routes of synthesis, surface modifications, hydrophilic/hydrophobic, porosity, durability etc. The recent developments on production of novel adsorbents or membranes encourage the implementation of nanocellulose based cleaner technologies for wastewater treatment.

Recycling of Brewer's Spent Grain as a Biosorbent by Nitro-Oxidation for Uranyl Ion Removal from Wastewater

Developing biosorbents derived from agro-industrial biomass is considered as an economic and sustainable method for dealing with uranium-contaminated wastewater. The present study explores the feasibility of oxidizing a representative protein-rich biomass, brewer's spent grain (BSG), to an effective and reusable uranyl ion adsorbent to reduce the cost and waste generation during water treatment. The unique composition of BSG favors the oxidation process and yields in a high carboxyl group content (1.3 mmol/g) of the biosorbent. This makes BSG a cheap, sustainable, and suitable raw material independent from pre-treatment. The oxidized brewer's spent grain (OBSG) presents a high adsorption capacity of U(VI) of 297.3 mg/g (c 0(U) = 900 mg/L, pH = 4.7) and fast adsorption kinetics (1 h) compared with other biosorbents reported in the literature. Infrared spectra (Fourier transform infrared), 13C solid-state nuclear magnetic resonance spectra, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and thermogravimetric analysis were employed to characterize the biosorbents and reveal the adsorption mechanisms. The desorption and reusability of OBSG were tested for five cycles, resulting in a remaining adsorption of U(VI) of 100.3 mg/g and a desorption ratio of 89%. This study offers a viable and sustainable approach to convert agro-industrial waste into effective and reusable biosorbents for uranium removal from wastewater.

Starch, cellulose, pectin, gum, alginate, chitin and chitosan derived (nano)materials for sustainable water treatment: A review

Natural biopolymers, polymeric organic molecules produced by living organisms and/or renewable resources, are considered greener, sustainable, and eco-friendly materials. Natural polysaccharides comprising cellulose, chitin/chitosan, starch, gum, alginate, and pectin are sustainable materials owing to their outstanding structural features, abundant availability, and nontoxicity, ease of modification, biocompatibility, and promissing potentials. Plentiful polysaccharides have been utilized for making assorted (nano)catalysts in recent years; fabrication of polysaccharides-supported metal/metal oxide (nano)materials is one of the effective strategies in nanotechnology. Water is one of the world's foremost environmental stress concerns. Nanomaterial-adorned polysaccharides-based entities have functioned as novel and more efficient (nano)catalysts or sorbents in eliminating an array of aqueous pollutants and contaminants, including ionic metals and organic/inorganic pollutants from wastewater. This review encompasses recent advancements, trends and challenges for natural biopolymers assembled from renewable resources for exploitation in the production of starch, cellulose, pectin, gum, alginate, chitin and chitosan-derived (nano)materials.

Carbon-based sustainable nanomaterials for water treatment: State-of-art and future perspectives

The supply of safe drinking and clean water is becoming increasingly challenging proposition throughout the world. The deployment of environmentally sustainable nanomaterials with unique advantages namely high efficiency and selectivity, earth-abundance, recyclability, low-cost of production processes, and stability, has been a priority although several important challenges and constraints still remained unresolved. Carbon nanomaterials namely activated carbon, multi-walled- and single-walled carbon nanotubes, have been developed and applied as adsorbents for wastewater treatment and purification; graphene and graphene oxide-based nanomaterials as well as carbon and graphene quantum dots-derived nanomaterials have shown significant promise for water and wastewater treatment and purification, especially, for industrial- and pharmaceutical-laden wastes. This review encompasses advanced carbonaceous nanomaterials and methodologies that are deployed for the elimination of contaminants and ionic metals in aqueous media, and as novel nanosorbents for wastewater, drinking and ground water treatment. Additionally, recent trends and challenges pertaining to the sustainable carbon and graphene quantum dots-derived nanomaterials and their appliances for treating and purifying wastewater are highlighted.

Sustainable carboxylated cellulose filters for efficient removal and recovery of lanthanum

Carboxylated cellulose filters were fabricated by oxidation of a cellulose fibrous mat via TEMPO-mediated oxidation. These carboxylated cellulose filters were employed as sustainable filters for removal and recovery of lanthanum ions (La (III)) with high adsorption capability. The surface chemistry of the carboxylated cellulose fibers before and after adsorption of La (III) was investigated systematically. The distribution of La (III) on carboxylated cellulose fibers were explored by EDX mapping approach, which revealed that the adsorption occurred on both the surface and the internal structure of the cellulose fibers. The kinetics and isotherms of the adsorption were conducted to understand the adsorption mechanism of the carboxylated cellulose filter and to learn the maximum adsorption capacity for La (III) which was as high as 33.7 mg/g. The adsorption selectivity of the carboxylated cellulose filter for La (III) was determined when interfering ions including mono- and di-covalent ions were involved. The carboxylated cellulose filter exhibited high adsorption capability and high permeation flux evidenced by the breakthrough curves of the dynamic adsorption of La (III) under an extremely low pressure of 0.07 kPa. A variety of desorption reagents were selected to recover lanthanum from the carboxylated cellulose filter, where the optimized conditions for recovery were explored. Finally, a spiral wound cartridge of the carboxylated cellulose fibrous mat was fabricated and the removal and the recovery of La (III, 2.5 ppm) from massive lanthanum-containing water were demonstrated. It was very impressive that the high rejection ratio of 94.3% was achieved under the low pressure drop of 3.0 kPa remaining throughout the separation process, and the treated solution volume was high up to 21.4 L, which was about six-times higher than that of commercially available nanofibrous adsorption membranes, indicating that the carboxylated cellulose filter could be used as a highly efficient adsorption medium for industrial recovery of rare earth metals.

Mild hydrothermally treated brewer's spent grain for efficient removal of uranyl and rare earth metal ions

The increasing concerns on uranium and rare earth metal ion pollution in the environment require sustainable strategies to remove them from wastewater. The present study reports an eco-friendly approach to convert a kind of protein-rich biomass, brewer's spent grain (BSG), into effective biosorbents for uranyl and rare earth metal ions. The employed method reduces the energy consumption by performing the hydrothermal treatment at a significantly lower temperature (150 °C) than conventional hydrothermal carbonization. In addition, with the aid of the Maillard reaction between carbohydrates and proteins forming melanoidins, further activation processes are not required. Treatment at 150 °C for 16 h results in an altered biosorbent (ABSG) with increased content of carboxyl groups (1.46 mmol g⁻¹) and a maximum adsorption capacity for La³⁺, Eu³⁺, Yb³⁺ (pH = 5.7) and UO₂²⁺ (pH = 4.7) of 38, 68, 46 and 221 mg g⁻¹, respectively. Various characterization methods such as FT-IR, ¹³C CP/MAS NMR, SEM-EDX and STA-GC-MS analysis were performed to characterize the obtained material and to disclose the adsorption mechanisms. Aside from oxygen-containing functional groups, nitrogen-containing functional groups also contribute to the adsorption. These results strongly indicate that mild hydrothermal treatment of BSG could be applied as a greener, low-cost method to produce effective adsorbents for uranyl and rare earth metal ion removal.

Effective biosorbent ABSG is obtained via hydrothermal treatment of BSG at low temperature without activation, minimizing energy consumption and environmental impact.

Arsenic(III) Removal by Nanostructured Dialdehyde Cellulose-Cysteine Microscale and Nanoscale Fibers

Arsenite (As(III)) contamination in drinking water has become a worldwide problem in recent years, which leads to development of various As(III) remediation approaches. In this study, two biomass-based nanostructured materials, microscale dialdehyde cellulose-cysteine (MDAC-cys) and nanoscale dialdehyde cellulose-cysteine (NDAC-cys) fibers, have been prepared from wood pulp. Their As(III) removal efficiencies and mechanism were determined by combined adsorption, atomic fluorescence spectrometry, microscopy (scanning electron microscopy, transmission electron microscopy, and atomic force microscopy), and spectroscopy (Fourier transform infrared, 13C CPMAS NMR) methods. The adsorption results of these materials could be well described by the Freundlich isotherm model, where the maximum adsorption capacities estimated by the Langmuir isotherm model were 344.82 mg/g for MDAC-cys and 357.14 mg/g for NDAC-cys, respectively. Both MDAC-cys and NDAC-cys materials were further characterized by X-ray diffraction and thermogravimetric analysis, where the results indicated that the thiol groups (the S content in MDAC-cys was 12.70 and NDAC-cys was 17.15%) on cysteine were primarily responsible for the adsorption process. The nanostructured MDAC-cys system appeared to be more suitable for practical applications because of its high cost-effectiveness.

Lead and cadmium adsorption by electrospun PVA/PAA nanofibers: Batch, spectroscopic, and modeling study

Water-stable PVA/PAA nanofibers were fabricated through electrospinning and evaluated for their performance in lead (Pb(II)) and cadmium (Cd(II)) removal from water in a batch experiment. The adsorption mechanism of Pb(II) was explored using the extended X-ray absorption fine structure (EXAFS) spectroscopic analysis. The PVA/PAA nanofibers showed a pH-dependent behavior for heavy metal removal, and its adsorption capacities for Pb(II) and Cd(II) could reach as high as 159 and 102 mg/g, respectively. The calcium ion (Ca(II)) had no effect on Pb(II) removal at pH 5.0 whereas it significantly reduced Cd(II) removal at pH 7.0. The adsorption of Pb(II) and Cd(II) was spontaneous and exothermic in nature with a decrease in randomness. The saturated PVA/PAA nanofibers could be regenerated using acidic solutions for reuse. The Fourier-transform infrared (FTIR) spectroscopic analysis indicated the formation of surface complexes between adsorbed Pb(II) and Cd(II) and carboxyl groups on PVA/PAA nanofibers. Moreover, EXAFS analysis suggested that a Pb(II) cation was chelated with three carboxyl groups on the nanofibers. This molecular-level adsorption structure was successfully implemented into a surface complexation model for the prediction of the macroscopic Pb(II) and Cd(II) adsorption behaviors. The results gained from this study provided complementary information on heavy metal removal by a new generation of adsorbents and improved the fundamental understanding for the removal process.

TEMPO-oxidized cellulose nanofiber (TOCN) decorated macroporous silica particles: Synthesis, characterization, and their application in protein adsorption

Effective protein adsorption has attracted attention for broad application in the biomedical field. In this study, we introduce the synthesis of a TEMPO-oxidized cellulose nanofiber (TOCN) decorated macroporous SiO₂ (TOCN@macroporous SiO₂) particle and its protein adsorption performance. The TOCN@macroporous SiO₂ particles have a unique cellulose nanofiber network structure on the macroporous, highly-negative zeta potential (-62 ± 2 mV) and high surface area (30.8 m²/g) for dried-state cellulose based particles. These characteristics provide sites that are rich in electrostatic interaction to exhibit an outstanding adsorption capacity of lysozyme (1865 mg/g). Furthermore, the TOCN@macroporous SiO₂ particles have remarkably high reusability (>90% adsorption capacity) and good release of adsorbate (>80%) after 10 times of use. The material proposed in this paper has the potential for application in drug delivery, protein adsorption, biosensors, and other biomedical fields.

Integrated Coagulation-Membrane Processes with Zero Liquid Discharge (ZLD) Configuration for the Treatment of Oil Sands Produced Water

This study explores the feasibility of implementing five hybrid coagulation-membrane processes for the treatment of the boiler blow-down (BBD) water from an oil sands steam assisted gravity drainage (SAGD) operation. The processes involved (1) direct nanofiltration (NF) of the BBD water, (2) pre-treatment of the NF retentate using ion exchanger regeneration wastewater (IERW) as a chemical coagulant followed by NF, (3) pre-treatment of BBD water using IERW followed by NF, (4) dual pre-treatment of BBD water using IERW and soda ash (sodium carbonate, Na2CO3) followed by NF, and (5) forward osmosis (FO) treatment of the BBD water using IERW as a draw solution followed by NF treatment of diluted draw solution. These scenarios were compared based on total flux decline ratio (DRt), flux recovery ratio (FRR), and total dissolved solids (TDS) removal over the final NF treatment to suggest an efficient treatment technique to avoid an undesired increase in the capital and operating expenses. It was found that process-1 provided the highest selectivity toward dissolved solids (80%) with a flux decline and recovery ration of 89.6% and 97.4%, respectively. Considering the permeation flux, process-4 exhibited the lowest flux decline (86.1%) and highest recovery ratio (97.5%) compared to other processes, proving the successful role of soda ash softening, as a chemical pretreatment method, in improving the performance of membrane filtration. Process-2 presented a mediocre performance with DRt, FRR, and TDS rejection of 93.3%, 97.3%, and 74%, respectively. Finally, process-3 and process-5 showed the lowest performance among all the scenarios with low flux recovery and low permeability, respectively. In addition, process-3 was expected to be cost-efficient since it only uses an on-site generated waste as a coagulant for the chemical pretreatment of the membrane filtration unit. The optimum scenario was proposed to be the two-stage membrane process, with direct NF of BBD followed by the post-treatment of the retentate via a hybrid chemical conditioning using IERW and soda ash softening, followed by a second NF. Overall, this integrated process offered a highly efficient mean with a zero liquid discharge (ZLD) system for the treatment of high pH wastewaters into an uncontaminated stream for the boilers.

Structural control of cellulose nanofibrous composite membrane with metal organic framework (ZIF-8) for highly selective removal of cationic dye

Highly durable cellulose nanofibrous composite membranes were prepared by in-situ growing of zeolitic imidazolate frameworks (ZIF-8) as spacers in the presence of TEMPO oxidized cellulose nanofibers (TOCN) as their anchoring points. The obtained composite membranes showed three-dimensionally networked nanofibers with ZIF-8 to generate porous structures, which gave high durability without critical compaction of the membrane under pressure (1∼3 bar). The 20 μm thick ZIF-8/TOCN membrane showed most superior water flux (84 Lm^-2 h^-1 bar^-1) without critical flux drop for 24 h operation. Interestingly, the composite membrane exhibited highly selective removal of cationic dyes in the presence of anionic dyes due to strong interaction through negatively charged TOCN networks. The experimental results in the study reveal a novel strategy for durable cellulose nanofibrous membrane via introduction of metal organic frameworks for highly selective filtration.

Current State and New Trends in the Use of Cellulose Nanomaterials for Wastewater Treatment

Nanotechnology has been identified as having great potential for improving the efficiency of water prevention and purification while reducing costs. In this field, two applications of nanocellulose have generated attention and have proven to be a sound strategy as an adsorbent and as a membrane for the removal of contaminants. This potential is attributed to its high aspect ratio, high specific surface area, high capacity retention, and environmental inertness. In addition to the aforementioned advantages, the presence of active sites allows the incorporation of chemical moieties that may enhance the binding efficiency of pollutants to the surface. This review paper intends to understand how nanocellulose affects the adsorption behavior of water pollutants, e.g., heavy metal ions, microbes, dyes, and organic molecules, and is divided in two parts. First, a general overview of the different strategies for the preparation of nanocellulose is described, and its specific properties are reported. The second section reports some of its application as adsorbent nanomaterial or separation membrane. It appears that the use of nanocellulose for these applications is very promising for wastewater treatment industries.

Wood-Based Nanotechnologies toward Sustainability

With over 30% global land coverage, the forest is one of nature's most generous gifts to human beings, providing shelters and materials for all living beings. Apart from being sustainable, renewable, and biodegradable, wood and its derivative materials are also extremely fascinating from a materials aspect, with numerous advantages including porous and hierarchical structure, excellent mechanical performance, and versatile chemistry. Here, strategies for designing novel wood-based materials via advanced nanotechnologies are summarized, including both the controllable bottom-up assembly from the highly crystalline nanocellulose building block and the more efficient top-down approaches directly from wood. Beyond material design, recent advances regarding the sustainable applications of these novel wood-based materials are also presented, focusing on areas that are traditionally dominated by man-made nonrenewable materials such as plastic, glass, and metals, as well as more advanced applications in the areas of energy storage, wastewater treatment and solar-steam-assisted desalination. With all recent progress pertaining to materials' design and sustainable applications presented, a vision for the future engineering of wood-based materials to promote continuous and healthy progress toward true sustainability is outlined.