Electrovalent effects of sodium carboxymethyl cellulose and hydroxyethyl cellulose on regeneration of empty fruit bunch cellulose to a superabsorbent hydrogel.

The hydrogel regeneration process, involving various cellulose types, results in distinct chemical bonding patterns. Even minor variations in chemical interactions among polymers during regeneration significantly impact properties like hydrogel-forming ability, hydrophilicity, and swelling capacity. This study focuses on regenerating a superabsorbent hydrogel from the interplay of native empty fruit bunch cellulose (EFBC), sodium carboxymethyl cellulose (NaCMC), and hydroxyethyl cellulose (HEC) using epichlorohydrin (ECH) as a crosslinker. The hydrogel was formed from dissolved EFBC solutions in an aqueous NaOH/urea solvent, supplemented with different NaCMC and HEC weight ratios, and ECH chemically assisted the crosslinking process. EFBC provides the hydrogel's supporting skeletal structure, while NaCMC and HEC play vital roles in enhancing forming ability and its physical and mechanical properties through diverse chemical interactions based on their electrovalent properties. Notably, NaCMC imparts hydrophilicity, while HEC indirectly improves superabsorbent properties through the enhancement of the elastic network's retraction force. Hydrogels combining NaCMC and HEC show a remarkable water absorption capacity exceeding 30,000 %, surpassing those regenerated solely with EFBC and NaCMC. The highest swelling, over 130,000 %, is achieved with 0.75 % NaCMC and 0.25 % HEC. Regarding thermal stability, hydrogels with a higher NaCMC proportion outperform those with increased HEC content. The study highlights the critical role of tailored chemical interactions in successfully regenerating an improved superabsorbent hydrogel with enhanced water absorption properties.

Enhanced CO2 Capture Potential of Chitosan-Based Composite Beads by Adding Activated Carbon from Coffee Grounds and Crosslinking with Epichlorohydrin.

Carbon dioxide (CO2) capture has been identified as a potential technology for reducing the anthropic emissions of greenhouse gases, particularly in post-combustion processes. The development of adsorbents for carbon capture and storage is expanding at a rapid rate. This article presents a novel sustainable synthesis method for the production of chitosan/activated carbon CO2 adsorbents. Chitosan is a biopolymer that is naturally abundant and contains amino groups (-NH2), which are required for the selective adsorption of CO2. Spent coffee grounds have been considered as a potential feedstock for the synthesis of activated coffee grounds through carbonization and chemical activation. The chitosan/activated coffee ground composite microspheres were created using the emulsion cross-linking method with epichlorohydrin. The effects of the amount of chitosan (15, 20, and 25 g), activated coffee ground (10, 20, 30, and 40%w/w), and epichlorohydrin (2, 3, 4, 5, 6, 7 and 8 g) were examined. The CO2 capture potential of the composite beads is superior to that of the neat biopolymer beads. The CO2 adsorbed of synthesized materials at a standard temperature and pressure is improved by increasing the quantity of activated coffee ground and epichlorohydrin. These findings suggest that the novel composite bead has the potential to be applied in CO2 separation applications.

Silk fibroin wetting stability film induced by polyamide-amine-epichlorohydrin (PAE) for intelligent sensing system.

Protein materials gain new functions and applicability through redesigns in protein structure and engineering confer. However, the application and development of proteins for use in flexible devices that fit in flexible devices that fit the surface of human skin is hindered by their poor wet stability. Here, we described the design of wet-stable materials based on the reconstruction of silk fibroin (SF). The combination of polyamide-amine-epichlorohydrin (PAE) was used as a traction rope to bring SF molecular chains closer to each other, to facilitate the self-assembly of SF through branching and lengthening of molecular chains, and change its crystalline structure. SF/PAE composite films that exhibited huge improvement in ductility and wet stability were combined with flexible SF substrates via patterning and ion sputtering to prepare flexible sensors. In addition, the SF/PAE sensing system equipped with a microprocessor and Bluetooth module enabled the real-time remote acquisition of human health signals such as vocal cords, joints, pulse and meridians. This reconfiguration of the SF structure will advance the systematic exploration of protein structures and the development of protein materials for intelligent device applications.

Dissolving-co-catalytic strategy for the preparation of flexible and wet-stable cellulose membrane towards biodegradable packaging.

In the realization of the goal of circular economy, cellulose as one of sustainable biomass resources, have attracted much attention because of their abundant sources, biodegradability and renewability. However, the mechanical and waterproof performance of cellulose-based materials are usually not satisfying, which limits their high-value utilization. In this study, cellulose membrane with high-performance from the aspects of mechanical properties, water-resistance ability, oxygen barrier capacity and biodegradability, was prepared from bleached hardwood pulp (HBKP) in a AlCl3/ZnCl2/H2O solution. The AlCl3/ZnCl2/H2O acted as both solvent and catalyst to dissolve cellulose and facilitate the chemical crosslinking of epichlorohydrin (EPI) with cellulose, thus improved the overall performance of the obtained cellulose membrane. The addition sequence, amount and crosslinking time of EPI during chemical crosslinking had important effects on the properties of the membranes. When 7 wt% EPI was crosslinked for 24 h, the tensile stress reached 133 MPa and the strain reached 17 %. Moreover, the membrane had excellent oxygen insulation down to (1.1 ± 0.31) × 10-4 cm3/m2·d·Pa, and good water-resistance ability, no obvious swelling behavior after 450 days of immersion in distilled water. Furthermore, the membrane could be degraded by microorganisms in about 20 days. This cellulose-based membrane offers a sustainable and biodegradable packaging material.

Construction of chitosan/alginate aerogels with three-dimensional hierarchical pore network structure via hydrogen bonding dissolution and covalent crosslinking synergistic strategy for thermal management systems.

To replace traditional petrochemical-based thermal insulation materials, in this work, the chitosan (CHI)/alginate (ALG) (CA) aerogels with three-dimensional hierarchical pore network structure were constructed by compositing CHI and ALG using a synergistic strategy of hydrogen bonding dissolution and covalent crosslinking. The structure and properties were further regulated by crosslinking the CA aerogels with epichlorohydrin (ECH). The CA aerogels exhibited various forms of covalent crosslinking, hydrogen bonding and electrostatic interactions, with hydrogen bonding content reaching 79.12 %. The CA aerogels showed an excellent three-dimensional hierarchical pore network structure, with an average pore size minimum of 15.92 nm. The structure regulation of CA aerogels obtained excellent compressive properties, with an increase of stress and strain by 137.61 % and 45.05 %, which can support a heavy object 5000 times its weight. Additionally, CA aerogels demonstrate excellent thermal insulation properties and low thermal conductivity, comparable to commercially available insulation materials. More importantly, CA aerogels have good cyclic insulation stability and thermal properties, and they have a flame retardancy rating of V-0, which shows the stability of insulation properties and excellent safety. CA aerogels provide new ideas for the development of biomass thermal insulation materials and are expected to be candidates for thermal management applications.

Preparation of (S)-epichlorohydrin using a novel halohydrin dehalogenase by selective conformation adjustment.

Chiral epichlorohydrin (ECH) is an attractive intermediate for chiral pharmaceuticals and chemicals preparation. The asymmetric synthesis of chiral ECH using 1,3-dicholoro-2-propanol (1,3-DCP) catalyzed by a haloalcohol dehalogenase (HHDH) was considered as a feasible approach. However, the reverse ring opening reaction caused low optical purity of chiral ECH, thus severely restricts the industrial application of HHDHs. In the present study, a novel selective conformation adjustment strategy was developed with an engineered HheCPS to regulate the kinetic parameters of the forward and reverse reactions, based on site saturation mutation and molecular simulation analysis. The HheCPS mutant E85P was constructed with a markable change in the conformation of (S)-ECH in the substrate pocket and a slight impact on the interaction between 1,3-DCP and the enzyme, which resulted in the kinetic deceleration of the reverse reactions. Compared with HheCPS, the catalytic efficiency (kcat(S)-ECH/Km(S)-ECH) of the reversed reaction dropped to 0.23-fold (from 0.13 to 0.03 mM-1 s-1), while the catalytic efficiency (kcat(1,3-DCP)/Km(1,3-DCP)) of the forward reaction only reduced from 0.83 to 0.71 mM-1 s-1. With 40 mM 1,3-DCP as substrate, HheCPS E85P catalyzed the synthesis of (S)-ECH with the yield up to 55.35% and the e.e. increased from 92.54 to >99%. Our work provided an effective approach for understanding the stereoselective catalytic mechanism as well as the green manufacturing of chiral epoxides.

Facile crosslinking methods for water-durable oven-dried cellulose nanofibril foams and their application as dye adsorbents.

The potential applications of cellulose nanofibril-based foam materials can be expanded by their enhanced water durability. This study proposes two crosslinking methods to improve the water durability of the oven-dried carboxymethylated cellulose nanofibril (CMCNF) foam. The first method involves the addition of a crosslinker, polyamideamine epichlorohydrin. The second method is the self-crosslinking of CMCNFs via heat treatment at 140 °C for less than an hour, which is a simple way to crosslink CMCNF-based materials. Both crosslinking methods resulted in excellent water durability and wet resilience of the foams, which also exhibited high water absorbency. Furthermore, neither method affected the structural nor mechanical properties of the oven-dried CMCNF foams. In particular, self-crosslinking by heat treatment proved to be as effective as using a crosslinking agent. Compared to the freeze-dried foam, the oven-dried foam exhibited slower methylene blue (MB) dye adsorption but a higher maximum adsorption capacity (238-250 mg/g), attributed to the closed pore structure and a larger specific surface area. In addition, the isotherm and reusability of the foam for MB adsorption were investigated. These crosslinking processes expanded the potential use of oven-dried CMCNF foams as adsorbents for cationic dyes.

Optimized design of quaternary amino-functionalized chitosan fibers for ultra-high diclofenac adsorption from wastewater.

The extraction of non-steroidal anti-inflammatory drugs (NSAIDs) from water bodies is imperative due to the potential harm to humans and the ecosystem caused by NSAID-contaminated water. Quaternary amino-functionalized epichlorohydrin cross-linked chitosan fibers (QECFs), an economical and eco-friendly adsorbent, were successfully prepared using a simple and gentle method for efficient diclofenac (DCF) adsorption. Additionally, the optimized factors for the preparation of QECFs included epichlorohydrin concentration, pH, temperature, and (3-chloro-2-hydroxypropyl) trimethylammonium chloride (CHTAC) concentration. QECFs demonstrated excellent adsorption performance for DCF across a broad pH range of 7-12. The calculated maximum adsorption capacity and the amount of adsorbed DCF per adsorption site were determined to be 987.5 ± 20.1 mg/g and 1.2 ± 0.2, respectively, according to the D-R and Hill isotherm models, at pH 7 within 180 min. This performance surpassed that of previously reported adsorbents. The regeneration of QECFs could be achieved using a 0.5 mol/L NaOH solution within 90 min, with QECFs retaining their original fiber form and experiencing only a 9.18% reduction in adsorption capacity after 5 cycles. The Fourier transform infrared spectrometer and X-ray photoelectron spectroscopy were used to study the characterization of QECFs, the preparation mechanism of QECFs, and the adsorption mechanism of DCF by QECFs. Quaternary ammonium groups (R4N+) were well developed in QECFs through the reaction between amino/hydroxyl groups on chitosan and CHTAC, and approximately 0.98 CHTAC molecule with 0.98 R4N+ group were immobilized on each chitosan monomer. Additionally, these R4N+ on QECFs played a crucial role in the removal of DCF.

Comparison of individual and ensemble machine learning models for prediction of sulphate levels in untreated and treated Acid Mine Drainage.

Machine learning was used to provide data for further evaluation of potential extraction of octathiocane (S8), a commercially useful by-product, from Acid Mine Drainage (AMD) by predicting sulphate levels in an AMD water quality dataset. Individual ML regressor models, namely: Linear Regression (LR), Least Absolute Shrinkage and Selection Operator (LASSO), Ridge (RD), Elastic Net (EN), K-Nearest Neighbours (KNN), Support Vector Regression (SVR), Decision Tree (DT), Extreme Gradient Boosting (XGBoost), Random Forest (RF), Multi-Layer Perceptron Artificial Neural Network (MLP) and Stacking Ensemble (SE-ML) combinations of these models were successfully used to predict sulphate levels. A SE-ML regressor trained on untreated AMD which stacked seven of the best-performing individual models and fed them to a LR meta-learner model was found to be the best-performing model with a Mean Squared Error (MSE) of 0.000011, Mean Absolute Error (MAE) of 0.002617 and R2 of 0.9997. Temperature (°C), Total Dissolved Solids (mg/L) and, importantly, iron (mg/L) were highly correlated to sulphate (mg/L) with iron showing a strong positive linear correlation that indicated dissolved products from pyrite oxidation. Ensemble learning (bagging, boosting and stacking) outperformed individual methods due to their combined predictive accuracies. Surprisingly, when comparing SE-ML that combined all models with SE-ML that combined only the best-performing models, there was only a slight difference in model accuracies which indicated that including bad-performing models in the stack had no adverse effect on its predictive performance.

Effect of epichlorohydrin treatment on the coating process and performance of high-barrier paper packaging.

The fabrication of coated papers using hydrophilic and biodegradable polymers is important for developing sustainable packaging materials with high barrier and superior mechanical properties. However, water, which is used as the solvent in the paper coating process using hydrophilic polymers, deforms the shape of the paper and deteriorates performance. Therefore, we propose a new coating process that treats Kraft paper (KP) with epichlorohydrin (ECH) as a binder before the coating process. Crosslinked polyvinyl alcohol is coated on the ECH-treated KP using a solution casting method. ECH maintains the shape of the paper and improves coating uniformity; significantly enhances interfacial interactions, which increases barrier properties and sealing strength; and extends the shelf life of biscuits by reducing oxygen and moisture permeability. An ecotoxicity test using Lolium multiflorum demonstrates an insignificant phytotoxicity level for the as-prepared coated papers. Thus, ECH-treated KP is a potential candidate for high-barrier food packaging.

Pd-loaded hierarchical titanosilicalite-1 catalysts on CO2 cycloaddition with epoxides: Experimental and DFT investigations.

This work presents the synthesis of Pd-loaded microporous titanosilicalite-1 (Pd/TS-1) and Pd-loaded hierarchical titanosilicalite-1 (Pd/HTS-1) with abundant mesopores (2-30 nm) inside the framework via hydrothermal method using polydiallydimethyl ammonium chloride as the non-surfactant mesopore template. XRD, N2 sorption, FT-IR, FESEM-EDX, TEM, XPS, and DR-UV techniques were used to characterize the morphological and physicochemical properties of the synthesized materials. These materials were tested as heterogeneous catalysts, along with tetrapropylammonium bromide as co-catalyst, for cycloaddition reactions of CO2 with epoxides to produce cyclic carbonates. It was found that the epoxide conversions were influenced by acidity and pore accessibility of the catalysts. Using Pd/HTS-1 facilitated bulky substrates to access active sites, resulting in higher conversions than Pd/TS-1. Over 85 % conversions were achieved for at least five consecutive cycles without significant loss in catalytic activity. The interaction between the Pd active surfaces and epichlorohydrin (ECH) was further studied by DFT calculations. The existence of Pd(200) was more influential on adsorbing epichlorohydrin (ECH) and subsequent formation of dissociated ECH (DECH) intermediate than Pd(111) surface. However, Pd(111) was dominant in enhancing the activity of DECH species for capturing CO2. Therefore, the co-existence of Pd(200) and Pd(111) surfaces was needed for cycloaddition of CO2 with ECH.

The Future of Municipal Wastewater Reuse Concentrate Management: Drivers, Challenges, and Opportunities.

Water reuse is rapidly becoming an integral feature of resilient water systems, where municipal wastewater undergoes advanced treatment, typically involving a sequence of ultrafiltration (UF), reverse osmosis (RO), and an advanced oxidation process (AOP). When RO is used, a concentrated waste stream is produced that is elevated in not only total dissolved solids but also metals, nutrients, and micropollutants that have passed through conventional wastewater treatment. Management of this RO concentrate─dubbed municipal wastewater reuse concentrate (MWRC)─will be critical to address, especially as water reuse practices become more widespread. Building on existing brine management practices, this review explores MWRC management options by identifying infrastructural needs and opportunities for multi-beneficial disposal. To safeguard environmental systems from the potential hazards of MWRC, disposal, monitoring, and regulatory techniques are discussed to promote the safety and affordability of implementing MWRC management. Furthermore, opportunities for resource recovery and valorization are differentiated, while economic techniques to revamp cost-benefit analysis for MWRC management are examined. The goal of this critical review is to create a common foundation for researchers, practitioners, and regulators by providing an interdisciplinary set of tools and frameworks to address the impending challenges and emerging opportunities of MWRC management.

Integrating experimental and theoretical studies in the development of a novel alginate-based bio-composite for copper anticorrosion in 3.5 % NaCl environments.

The development of new coatings based on a biopolymer, epichlorohydrin-modified alginate, and alginate-epichlorohydrin-SrTiO3 nanocomposites incorporating SrTiO3 (STO) nanoparticles in the alginate (Alg) matrix (Alg-Ep-STO), has been addressed in this study. Various characterization techniques were employed to analyze the prepared compounds, including X-ray diffraction spectroscopy (XRD), Fourier-transform infrared spectroscopy (FTIR), as well as surface analysis methods such as Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX). Furthermore, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarisation (PDP) methods were used to evaluate corrosion inhibition and protection durability. The results demonstrate that the incorporation of STO nanoparticles into the alginate matrix with epichlorohydrin significantly improved the metal's resistance to corrosion. The experimental findings received reinforcement from various computational methods, including density functional theory (DFT), Molecular Dynamics (MD) and Monte Carlo (MC) simulations, which were employed to investigate the interactions between the Alg-Ep-STO nanocomposite and the copper surface. The computational outcomes revealed that the Alg-Ep-STO nanocomposite exhibits robust adhesion to the copper surface, maintaining a flat orientation, with its alignment being notably influenced by the presence of STO nanoparticles.

Forsythoside B alleviates osteoarthritis through the HMGB1/TLR4/NF-κB and Keap1/Nrf2/HO-1 pathways.

Osteoarthritis (OA) is a joint pain and dysfunction syndrome resulting from severe joint degeneration. Inflammation and degeneration of the articular cartilage are two main features of OA and have tight interactions during OA progression. Conventional treatment with nonsteroidal anti-inflammatory drugs has been widely utilized clinically, whereas the side effects have restricted their application. Forsythoside B has been found with anti-inflammatory effects and antiapoptosis in inflammatory diseases, whereas in OA it remains poorly understood. Interleukin (IL)-1ß (10 ng/mL) was taken to induce an OA cell model on HC-A chondrocytes and an OA rat model was constructed for in vivo experiments. Forsythoside B was adopted to treat HC-A chondrocytes and OA rats. As shown by the data, Forsythoside B hampered IL-1ß-elicited rat chondrocyte apoptosis, oxidative stress, and facilitated proliferation. The profiles of inflammatory factors, NOD-like receptor family pyrin domain containing 3 inflammasomes, Kelch-like epichlorohydrin-associated protein-1 (Keap1), and nuclear factor-κB (NF-κB) phosphorylation were suppressed by Forsythoside B, whereas the nuclear factor E2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) levels were promoted. Further, Forsythoside B mitigated cartilage damage and degeneration. Moreover, the oxidative stress and inflammation mediators in the cartilage tissue of OA rats were remarkably abated. Collectively, Forsythoside B hinders the NF-κB and Keap1/Nrf2/HO-1 pathways to curb IL-1ß-elicited OA rat oxidative stress and inflammation both in vivo and ex vivo, ameliorating OA development. All over, this study provides an underlying strategy for treating OA, which might help the clinical treatment of OA patients.

Baicalein Alleviates Arsenic-induced Oxidative Stress through Activation of the Keap1/Nrf2 Signalling Pathway in Normal Human Liver Cells.

BACKGROUND: Oxidative stress is a key mechanism underlying arsenicinduced liver injury, the Kelch-like epichlorohydrin-related protein 1 (Keap1)/nuclear factor E2 related factor 2 (Nrf2) pathway is the main regulatory pathway involved in antioxidant protein and phase II detoxification enzyme expression. The aim of the present study was to investigate the role and mechanism of baicalein in the alleviation of arsenic-induced oxidative stress in normal human liver cells. METHODS: Normal human liver cells (MIHA cells) were treated with NaAsO2 (0, 5, 10, 20 µM) to observe the effect of different doses of NaAsO2 on MIHA cells. In addition, the cells were treated with DMSO (0.1%), NaAsO2 (20 µM), or a combination of NaAsO2 (20 µM) and Baicalein (25, 50 or 100 µM) for 24 h to observe the antagonistic effect of Baicalein on NaAsO2. Cell viability was determined using a Cell Counting Kit- 8 (CCK-8 kit). The intervention doses of baicalein in subsequent experiments were determined to be 25, 50 and 100µM. The intracellular content of reactive oxygen species (ROS) was assessed using a 2',7'-dichlorodihydrofluorescein diacetate (DCFHDA) probe kit. The malonaldehyde (MDA), Cu-Zn superoxide dismutase (Cu-Zn SOD) and glutathione peroxidase (GSH-Px) activities were determined by a test kit. The expression levels of key genes and proteins were determined by real-time fluorescence quantitative polymerase chain reaction (qPCR) and Western blotting. RESULTS: Baicalein upregulated the protein expression levels of phosphorylated Nrf2 (p-Nrf2) and nuclear Nrf2, inhibited the downregulation of Nrf2 target genes induced by arsenic, and decreased the production of ROS and MDA. These results demonstrate that baicalein promotes Nrf2 nuclear translocation by upregulating p-Nrf2 and inhibiting the downregulation of Nrf2 target genes in arsenic-treated MIHA cells, thereby enhancing the antioxidant capacity of cells and reducing oxidative stress. CONCLUSION: Baicalein alleviated arsenic-induced oxidative stress through activation of the Keap1/Nrf2 signalling pathway in normal human liver cells.

Diosmetin alleviates neuropathic pain by regulating the Keap1/Nrf2/NF-κB signaling pathway.

BACKGROUND: Neuropathic pain, a chronic condition with a high incidence, imposes psychological burdens on both patients and society. It is urgent to improve pain management and develop new analgesic drugs. Traditional Chinese medicine has gained popularity as a method for pain relief. Diosmetin (Dio) is mainly found in Chinese herbal medicines with effective antioxidant, anti-cancer, and anti-inflammatory properties. There are few known mechanisms underlying the effectiveness of Dio in treating neuropathic pain. However, the complete understanding of its therapeutic effect is missing. PURPOSE: This study aimed to evaluate Dio's therapeutic effects on neuropathic pain models and determine its possible mechanism of action. We hypothesized that Dio may activate antioxidants and reduce inflammation, inhibit the activation of Kelch-like epichlorohydrin-associated protein 1 (Keap1) and nuclear factor-k-gene binding (NF-κB), promote the metastasis of nuclear factor erythroid 2-related factor 2 (Nrf2) and the expression of heme oxygenase 1 (HO-1), thus alleviating the neuropathic pain caused by spinal nerve ligation. METHODS: Chronic nociceptive pain mouse models were established in vivo by L4 spinal nerve ligation (SNL). Different dosages of Dio (10, 50, 100 mg/kg) were intragastrically administered daily from the third day after the establishment of the SNL model. Allodynia, caused by mechanical stimuli, and hyperalgesia, caused by heat, were assessed using the paw withdrawal response frequency (PWF) and paw withdrawal latency (PWL), respectively. Cold allodynia were assessd by acetone test. RT-PCR was used to detect the content of interleukin-(IL)- 1ß, IL-6 and tumor necrosis factor (TNF)-a. Immunofluorescence and western blotting were employed to assess the expression levels of Glial fibrillary acidic protein (GFAP), ionized calcium-binding adapter molecule (Iba1), Keap1, Nrf2, HO-1, and NF-κB p-p65 protein. RESULTS: Dio administration relieved SNL-induced transient mechanical and thermal allodynia in mice. The protective effect of Dio in the SNL model was associated with its anti-inflammatory and anti-glial responses in the spinal cord. Dio inhibited both inflammatory factors and macrophage activation in the DRG. Furthermore, Dio regulated the Keap1/Nrf2/NF-κB signaling pathway. HO-1 and Nrf2 were upregulated following Dio administration, which also decreased the levels of Keap1 and NF-κB p65 protein. CONCLUSION: Mice with SNL-induced neuropathic pain were therapeutically treated with Dio. Dio may protect against pain by inhibiting inflammatory responses and improved Keap1/Nrf2/NF-κB pathway. These results highlight the potential therapeutic effect of Dio for the development of new analgesic drugs.

Spatial and temporal variation in toxicity and inorganic composition of hydraulic fracturing flowback and produced water.

Hydraulic fracturing for oil and gas extraction produces large volumes of wastewater, termed flowback and produced water (FPW), that are highly saline and contain a variety of organic and inorganic contaminants. In the present study, FPW samples from ten hydraulically fractured wells, across two geologic formations were collected at various timepoints. Samples were analyzed to determine spatial and temporal variation in their inorganic composition. Results indicate that FPW composition varied both between formations and within a single formation, with large compositional changes occurring over short distances. Temporally, all wells showed a time-dependent increase in inorganic elements, with total dissolved solids increasing by up to 200,000 mg/L over time, primarily due to elements associated with salinity (Cl, Na, Ca, Mg, K). Toxicological analysis of a subset of the FPW samples showed median lethal concentrations (LC50) of FPW to the aquatic invertebrate Daphnia magna were highly variable, with the LC50 values ranging from 1.16% to 13.7% FPW. Acute toxicity of FPW significantly correlated with salinity, indicating salinity is a primary driver of FPW toxicity, however organic components also contributed to toxicity. This study provides insight into spatiotemporal variability of FPW composition and illustrates the difficulty in predicting aquatic risk associated with FPW.

Experimental and theoretical studies on nitrate removal using epichlorohydrin-modified cross-linked chitosan derived from shrimp waste.

Nitrates level in water is a worldwide problem that represents a risk to the environment and people's health; efforts are currently devoted to the development and implementation of new biomaterials for their removal. In this study, chitosan (Ch) from shrimp waste and the related epichlorohydrin-modified crossover chitosan (Ch-EPI) were used to remove nitrates from aqueous solutions. The mechanism of selective nitrate removal was elucidated and validated by theoretical calculations. The physicochemical performance of Ch and Ch-EPI was investigated through the main parameters pH, adsorption capacity, contact time, initial nitrate concentration, coexisting anions, and temperature. The experimental data were fitted to widely used adsorption kinetic models and adsorption isotherms. The maximum percentage of nitrate adsorption was reached at an equilibrium pH of 4.0 at an adsorbent dose of 2.0 g/L after a contact time of 50 min. Competing anion experiments show that chloride and sulfate ions have minimal and maximal effects on nitrate adsorption by Ch-EPI. Experimental adsorption data are best fitted to pseudo-second-order kinetic and isothermal Langmuir models. The maximum adsorption capacities of Ch and Ch-EPI for nitrate removal were 12.0 mg/g and 38 mg/g, respectively.

Synergic binding of rhodamine-B and heavy metal ions onto polyethyleneimine grafted freeze-dried chitosan/epichlorohydrin composite beads and possible mechanism.

This paper reports a synergic binding technique of dye and cadmium/lead ions onto freeze-dried modified chitosan beads (GCCS), in this work modified chitosan beads was applied in binary solution. Chitosan beads (CS) composite was produced and polyethyleneimine was grafted onto the backbone of the developed composite. The beads were analyzed utilizing different analytical techniques such as Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscope (SEM). The model applied in pH equilibrium was found to justify the adsorption of pollutants onto the adsorbent. The model was established from 2 equilibrium calculations, one justifying the acid-base attributes of the modified beads, the other elucidating the adsorption of the adsorbates onto the beads, and a mass balance of the various arrangement of nitrogen in the adsorbent. The excellent fit of the Pseudo-second order and intra-particle diffusion kinetic model shows that chemical binding might be the rate-limiting step. The adsorption isotherms were well represented by the Langmuir and Temkin models at a temperature of 45 °C. The maximum binding capacities (Qmax) from the Langmuir model were observed to be 390, 315 and 278 mg/g for the adsorption of dye, lead and cadmium ions respectively`. However, it was found to be higher in the binary system with the same applicable conditions. The correlation was analyzed utilizing various models and lines of best fit were obtained. Synergic effect was observed from the experimental results acquired from the adsorption of Rhodamine B (RHB) and adsorbates. These findings show the formation of fresh binding sites during simultaneous binding process.

Chitosan cross-linked and grafted with epichlorohydrin and 2,4-dichlorobenzaldehyde as an efficient adsorbent for removal of Pb(II) ions from aqueous solution.

Epichlorohydrin-modified chitosan-Schiff base composite (CS/24Cl/ECH) prepared via the one-pot reaction as characterized by Fourier transform Infra-Red spectroscopy (FT-IR), X-ray powder diffraction (XRD), Differential scanning calorimetry (DSC) and Scanning electron microscope (SEM). Its removal ability of Pb(II) ions from aqueous solution was investigated. The adsorption of Pb(II) ions carried out at different initial pH, dose of CS/24-Cl/ECH, contact time and co-existing ions. The maximum adsorption capacity of Pb(II) ions was 170 mg/g. Finally, based on the absorption results, the adsorption of Pb(II) ions was fitted by single-layer Langmuir isotherm model and the pseudo-second-order (PSO) kinetics model. The absorption mechanism of Pb(II) ions was controlled by chemical coordination Pb(II) ions with the active sites on the surface of CS/24Cl/ECH composite. Also, CS/24Cl/ECH showed excellent recyclable efficiency up to 5 cycle and potential sorbent for other heavy metal ions.