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Functionalized polymethyl methacrylate-modified dialdehyde guar gum containing hydrazide groups for effective removal and enrichment of dyes, ion, and oil/water separation

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Abstract

In the study, a novel polymethacryloyl hydrazone modified guar gum adsorption material (GSA) was prepared via condensation between polyhydrazide and dialdehyde guar gum. GSA exhibited an abundant porous structure, higher selectivity for cationic pollutants in high-concentration wastewater like methylene blue (MB), malachite green (MG) dyes, and Cu²⁺. Under optimized experimental conditions, the maximum equilibrium adsorption capacity of MB, MG, and Cu²⁺ were 1418.36 mg/g, 1375.58 mg/g, and 196 mg/g, respectively. Adsorption isotherms and kinetics were well fitted with the Langmuir isotherm model and pseudo-second-order kinetic model. The thermodynamic analysis demonstrated that the adsorption process was endothermic, feasible, and spontaneous. Correspondently, the adsorption mechanism was explored by FTIR, SEM-EDS and XPS. The adsorbent was employed in disposing of local sewage water. Additionally, GSA successfully achieves efficient water/oil separation in different salt concentrations with a separation efficiency exceeding 99%.

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... [22] Modified GG has been reported as an adsorbent for heavy metal ions, [23] dyes, [24] and drug delivery. [25] The extraordinary viscosity, gelling ability, or thickening properties of GG are due to the presence of a large number of hydroxyl groups that undergo hydrogen bonding with water molecules, and the result is chain entanglement of galactose unit attached to the side chain of the mannose backbone. [26,27] In the literature, there are reports on the modification of GG for use in different applications. ...
... Citric acid modified sea weed 90 20 7.0 224.43 CV [77] 10 ZnCl 2 activated carbon 160 25 8.0 142.85 CV [78] 11 Activated carbon from Apricot stones 40 25 10.0 23.99 MG [79] 12 cumulative adsorption capacity were found to be 65.7 mg/g (after the seventh repeating cycle) and 552.76 mg/g, respectively ( Figure 14). A very small decrease in adsorption was observed in each cycle because of the blockade of some of the adsorption sites by the dye molecules even after desorption. ...
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To develop new sustainable and efficient materials for green technologies, we report the synthesis of guar gum (GG) and 2-Acrylamido-2-methylpropanesulfonic acid (AMPSA) based hydrogels for the removal of cationic dyes. GG was grafted with AMPSA and crosslinked with different concentrations (1, 2.5, and 5%) of ethyleneglycoldimethylacrylate (EGDMA) to obtain GG-g-poly(AMPSA)-cl-EGDMA hydrogels. The well-characterized hydrogels were investigated for adsorption of two cationic dyes, malachite green (MG) and crystal violet (CV). The hydrogel with 2.5% EGDMA showed the best dye uptake and was thus further investigated for the uptake of dyes. The selectivity of the hydrogels for cationic dyes was established by comparing the adsorption capacity of cationic and anionic dyes from their binary solutions. The role of the sulfonate group in the removal of the cationic dyes was established with two control experiments using pristine GG and GG hydrogel with 2.5% EGDMA but without AMPSA. The hydrogel showed tremendous dye adsorption with percent uptake up to 93.13% for MG, 91.50% for CV, and 91.8% for the mixture of dyes in 45 minutes. The adsorption followed pseudo-second-order kinetics and Langmuir adsorption isotherm with a maximum adsorption capacity of 354.6 mg/g and 163.39 mg/g for CV and MG, respectively. The adsorbent exhibited good regeneration and recyclability up to seven cycles. Finally, dye adsorption studies of the candidate hydrogel were carried out for real textile effluent. The reported GG-g-poly(AMPSA)-cl-EGDMA hydrogels possess great potential as cost-effective, sustainable, recyclable, and environmentally-friendly adsorbents for the selective and effective removal of hazardous cationic dyes from wastewater.
... Typically, hypochlorite ions are used as oxidizing agents in the presence of bromide and TEMPO catalysts (NaOCl-NaBr-TEMPO system) [142][143][144][145]. Additionally, O 2 oxidant can also be used with laccase enzymes and TEMPO mediator (O 2 -Laccase-TEMPO system) for the same purpose ( Fig. 4) [146][147][148][149]. In addition, oxidative cleavage of vicinal 1,2-diols on GG by periodate (periodate-mediated oxidation) could be readily performed on C 2 -OH and C 3 -OH of mannose backbone, and C 2 -OH, C 3 -OH and C 4 -OH of galactose side groups to produce different dialdehyde GG products [150][151][152][153][154][155][156][157]. Further oxidation of aldehyde groups in dialdehyde GG products to carboxylic acids by chlorite ions is also possible (Fig. 4) [158]. ...
... Meanwhile, a wide range of transition and heavy metal ions is soft acids and tend to interact more strongly with soft bases such as S-containing thiol, sulfide, xanthate and dithiocarbamate functional groups [152][153][154]. While dithiocarbamate can be easily introduced onto polysaccharides that contain amino groups such as chitosan [155][156][157][158], xanthate functional groups are of great interest to polysaccharides possessing hydroxyl groups [159,160]. ...
... Therefore, the K/S value of sample 13 is smaller than the rest of the samples. As a result, the use of urea and bicarbonate T A B L E 3 Characteristic of the printing paste for samples [13][14][15][16] Sample Thickener GOC (%) Amount of GOC (g) Reactive dye (g) Urea (g) Sodium bicarbonate (g) Ludigol Total (g) 13 1. in the printing paste version leads to the stabilisation of the reactive dye on the cotton fabric. Comparing the samples printed with modified GG and the sample printed with sodium alginate (sample 19), the amount of colour strength of the samples printed with modified GG is better than the results of sodium alginate. ...
... Therefore, the K/S value of sample 13 is smaller than the rest of the samples. As a result, the use of urea and bicarbonate T A B L E 3 Characteristic of the printing paste for samples [13][14][15][16] Sample Thickener GOC (%) Amount of GOC (g) Reactive dye (g) Urea (g) Sodium bicarbonate (g) Ludigol Total (g) 13 1. in the printing paste version leads to the stabilisation of the reactive dye on the cotton fabric. Comparing the samples printed with modified GG and the sample printed with sodium alginate (sample 19), the amount of colour strength of the samples printed with modified GG is better than the results of sodium alginate. ...
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The alginate thickener is the thickener frequently used for reactive printing of textile. The thickener responds with reactive pigments and thus does not lead to the fabric composition becoming stiffer. In this study, we prepared oxidised natural guar gum with hydrogen peroxide, sodium hypochlorite and sodium hydroxide. All other polysaccharides comprise reactive hydroxyl units with a stronger reactivity that must be replaced if they are to be used in reactive printing. Guar derivatives were synthesised and verified using Fourier‐transform infrared (FTIR) spectroscopy. Natural thickeners, synthetic guar gum derivatives, have been employed in textile printing technique. In comparison to other synthetic thickeners, modified environmental guar gum polymer has been shown to be an ecologically friendly and low‐cost thickener. Cotton fabric printed with modified guar thickening with hydrogen peroxide has even stronger colour strength than fabric printed with sodium alginate thickener, which is highly favourable. Penetration properties, colour value, colour strength, colour fastness to washing, light and rubbing was compared with alginate thickener (readily available on the market). Guar gum thickeners showed enhanced features versus sodium alginate for reactive printing. Partially replaced guar gum is an appropriate option due to the colour and physical properties.
... The MB dye and St-g-PMMAs have generated two different forms of interactions, i.e., electrostatic interaction and hydrogen bonding. The hydrogen bonds were generated between the lone pair of electrons of the nitrogen and sulphur of the structure of the MB dye and the hydrogen of the hydroxyl group of the St-g-PMMAs [46,47]. Additionally, the MB dye's positively charged nitrogen atom and negatively charged oxygen atoms on the starch backbone and the methyl methacrylate established electrostatic connections. ...
... Figure 8 depicts the various interactions between the St-g-PMMAs and the MB dye. and sulphur of the structure of the MB dye and the hydrogen of the hydroxyl group of the St-g-PMMAs [46,47]. Additionally, the MB dye's positively charged nitrogen atom and negatively charged oxygen atoms on the starch backbone and the methyl methacrylate established electrostatic connections. ...
Article
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In this research, a new biodegradable and eco-friendly adsorbent, starch-grafted polymethyl methacrylate (St-g-PMMA) was synthesized. The St-g-PMMA was synthesized by a free radical polymerization reaction in which methyl methacrylate (MMA) was grafted onto a starch polymer chain. The reaction was performed in water in the presence of a potassium persulfate (KPS) initiator. The structure and different properties of the St-g-PMMA was explored by FT-IR, 1H NMR, TGA, SEM and XRD. After characterization, the St-g-PMMA was used for the removal of MB dye. Different adsorption parameters, such as effect of adsorbent dose, effect of pH, effect of initial concentration of dye solution, effect of contact time and comparative adsorption study were investigated. The St-g-PMMA showed a maximum removal percentage (R%) of 97% towards MB. The other parameters, such as the isothermal and kinetic models, were fitted to the experimental data. The results showed that the Langmuir adsorption and pseudo second order kinetic models were best fitted to experimental data with a regression coefficient of R2 = 0.93 and 0.99, respectively.
... The adsorption kinetic data were analyzed using two different mathematical models (Eqs. (6) and (7)) in order to evaluate the possible mechanisms responsible for the TTC removal onto the examined materials [28,65]: ...
... Due to the potentially harmful consequences on the environment, the adsorption of dyes by PMMA and its modified materials has been the focus of numerous study (Cantarella et al. 2016;Rizzo et al. 2007;Wen et al. 2022). For the purpose of eliminating methylene blue (MB) from an aqueous solution, adsorption tests were conducted. ...
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The antibacterial activity of a variety of modified poly(methyl methacrylate) Schiff bases against common microbial infections and removal of methylene blue (MB) dye were screened. The Schiff bases were synthesized from the reaction of the modified (PMMA) with vanillin (PMMA)Van and cinnamaldehyde (PMMA)Cin. By using Fourier transformer infrared (FT-IR), X-ray diffraction analysis (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM), the structures of the nanofibers of the synthesized Schiff bases were confirmed. The modified Kirky–Bauer method was used to screen the antibacterial activities of all the obtained materials against various bacterial species, including gram-positive bacterial (Bacillus subtilis (4k1p), Staphylococcus aureus), Gram-negative bacteria (Escherichia coli (7ab3), Pseudomonas aeruginosa). Inhibition zones against gram-positive bacteria ranged in diameter from 7 to 14 mm, whereas for the Gram-negative bacteria, the inhibition zones found to be ranged between 6 and 13 mm. With a minimum bactericidal concentration (MBC) of 8 mg/mL and a minimum inhibitory concentration (MIC) of 2 mg/mL, (PMMA)Van shown the greatest antibacterial activity. Lastly, molecular docking research was done to better understand the interactions between this series' targets and inhibitors for (PMMA)Van and (PMMA)Cin (4k1p and 7ab3). Molecular modeling of these surface-adsorbed polymers indicated that (PMMA)Van binds more strongly with Nitrogen than does (PMMA)Cin through extra hydrogen-bonding interactions. All the developed materials were evaluated for the removal of 0.1 g/L methylene blue dye (MB) from an aqueous solution. The elimination percentage of MB dye ranged from 26.67% by using 0.05 g powder of (PMMA)Cin to 85.63% by employing 0.05 g nanofibers of (PMMA)Van. Graphical Abstract
... Improper disposal of these chemicals can lead to soil and water contamination, which can have severe consequences on the environment and human health. It has been shown that adsorbents based on guar gum can effectively remove oily contaminants from water sources [246,247]. For instance, researchers developed a modified form of guar gum (GG-SH) using a rapid condensation reaction between stearic hydrazide and polysaccharide [248]. ...
Article
The increasing environmental concerns and regulatory requirements have led to the development of eco-friendly bio-adsorbents for wastewater remediation. Natural biopolymers have drawn significant attention in this field due to their renewable and biodegradable nature. Among the various natural biopolymers, polysaccharides such as alginate, cellulose, starch, chitosan, and natural gums have attracted significant attention due to their availability and low cost. The main objective of this review is to provide a detailed account of bio-adsorbents derived from polysaccharides, covering their practical application and effectiveness in removing a broad range of pollutants from aqueous media. Each polysaccharide is comprehensively discussed based on the type of pollutants it can remove. Specifically, research papers from 2021 and onwards have been reviewed to present the latest progress in this field. Additionally, the synthesis, adsorption mechanism, and recyclability of each polysaccharide are briefly discussed. Finally, insights into future directions and perspectives for the development of polysaccharide-based adsorbents for wastewater remediation are provided. Overall, this review emphasizes the potential of natural biopolymers, particularly polysaccharides, as eco-friendly and cost-effective bio-adsorbents for wastewater treatment. Moreover, it provides valuable insights into potential avenues for future investigations within this domain, thereby offering significant benefits to both novice and seasoned researchers engaged in the study of wastewater remediation.
... (e) Zeta potential of ZIF-67/LDH and ZIF-67/ LDH@C, and (f) FT-IR spectra of ZIF-67/LDH@C before and after adsorption of MG and CR. (g) Illustration of the mechanism of Pb 2+ , MG and CR capture by ZIF-67/LDH@C hydroxyl groups of adsorbents and nitrogen on dyes) and Yoshida H-bonding (between the aromatic ring of dyes and oxygen on − OH) (Wen et al. 2022). The conjugation interaction (π-π interaction) between ZIF-67/LDH@C (imidazole aromatic ring in ZIF-67) and dye molecules (conjugate aromatic structure moieties) is suggested by the fact that the adsorption peak at approximately 1585 cm −1 , attributed to the stretching vibration of aromatic ring shorted to 1589 cm −1 and 1593 cm −1 after MG and CR adsorption, respectively (Arabkhani and Asfaram 2020;Yan and Li 2021). ...
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A novel sorbent ZIF-67/LDH@C was synthesised using mild etching and co-precipitation and carbonization calcination for the elimination of lead ions (Pb ²⁺ ), malachite green (MG), and congo red (CR) from water. The three-dimensional hollow MOF structure and two-dimensional LDH nanosized layers of ZIF-67/LDH@C were demonstrated by scanning electron microscope (SEM), transmission electron microscopy (TEM), fourier transform infrared (FT-IR), X-ray diffraction (XRD), nitrogen adsorption/desorption, thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) characterization. The maximal adsorption capability of Pb ²⁺ , MG, and CR could reach 662.25, 1729.83 and 526.32 mg∙g ⁻¹ , respectively. The kinetic study proved that the adsorption was chemisorption or strong complexation and the rate-limiting step was intraparticle diffusion. The isotherms effectively indicated the monomolecular-type adsorption. Thermodynamic studies showed the spontaneous and endothermic nature of Pb ²⁺ , MG and CR adsorption onto ZIF-67/LDH@C. The adsorption mechanisms of ZIF-67/LDH@C may be attributed to electrostatic attraction, π-π interaction, hydrogen-bonding interaction, and surface complexation between ZIF-67/LDH@C and pollutants. Furthermore, favourable stability and negligible interference from other metal ions could promote the viability of the practical application of ZIF-67/LDH@C in wastewater purification. Graphical Abstract
... While phenolic moieties in DAGG-GH can enhance the reversible adsorption of cationic dyes [bromophenol blue (BrB), methyl orange (MeO), MB, RhB] via ionic and π stacking interaction, SH moieties in DAGG-SH are efficient adsorptive sites for metal cations such as Ni 2+ , Co 2+ and Cr 3+ . In addition, Wen et al. also used hydrazine to conjugate DAGG and MBAAm cross-linked copolymer of acrylic acid and methyl methacrylate [MBAAm-cl-P(AA-co-MMA)] to prepare a novel adsorbent [220]. Oxidation of GG was first carried out by periodate to yield DAGG with the degree of oxidation of 67.62 %. ...
Article
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Guar gum (GG) from seeds of cluster bean (Cyamopsis tetragonolobus) contains mainly non-ionic galactomannan polysaccharide. Due to fascinating properties, great natural abundancy, low cost, biocompatibility and biodegradability, natural GG polysaccharide has been studied and employed in various research fields and industries. To explore and extend full potentials of GG, further chemical functionalization of the material is essential. This review highlights recent progress in the chemical modification of GG and its derivatives based on nucleophilic reactions, partial oxidation, graft polymerization and cross-linking with diverse chemical reagents and reaction pathways. Moreover, further insights into structure-property relationships as well as potential applications of the materials are also provided and discussed.
... The grafted guar gum can also be used as a multifunctional material for oil-water separation and adsorption of metal ions. Wen et al. [137] prepared a multifunctional poly(methacryloyl hydrazone) modified guar gum adsorbent via the reaction of hydrazine hydrate-modified poly(acrylic acid-co-methyl methacrylate) with dialdehyde guar gum. This material can not only efficiently separate oil from water, but also efficiently adsorb dyes and heavy metal ions with the adsorption capacities of 1418.36 mg/g for methylene blue, 1375.58 mg/g for malachite green, and 196 mg/g for Cu(II) (adsorbent dosage: 1 g/L; initial concentration: 1000 mg/L for dyes, and 800 mg/L for Cu(II)), which greatly expands the application field of guar gum-based adsorption materials. ...
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The ubiquitous presence of contaminants in water poses a major threat to the safety of ecosystems and human health, and so more materials or technologies are urgently needed to eliminate pollutants. Polymer materials have shown significant advantages over most other adsorption materials in the decontamination of wastewater by virtue of their relatively high adsorption capacity and fast adsorption rate. In recent years, "green development" has become the focus of global attention, and the environmental friendliness of materials themselves has been concerned. Therefore , natural polymers-derived materials are favored in the purification of wastewater due to their unique advantages of being renewable, low cost and environmentally friendly. Among them, natural plant gums show great potential in the synthesis of environmentally friendly polymer adsorp-tion materials due to their rich sources, diverse structures and properties, as well as their renewable, non-toxic and biocompatible advantages. Natural plant gums can be easily modified by facile deri-vatization or a graft polymerization reaction to enhance the inherent properties or introduce new functions, thus obtaining new adsorption materials for the efficient purification of wastewater. This paper summarized the research progress on the fabrication of various gums-based adsorbents and their application in the decontamination of different types of pollutants. The general synthesis mechanism of gums-based adsorbents, and the adsorption mechanism of the adsorbent for different types of pollutants were also discussed. This paper was aimed at providing a reference for the design and development of more cost-effective and environmentally friendly water purification materials .
... While adsorption of anionic EBT onto the surface of GP-cl-P(AA-co-IT) majorly occurred by dipole-dipole hydrogen bonding followed by electrostatic interactions (Fig. 5 (b)). Very recently, Wen and co-workers [247] have successfully synthesized a novel polymethacryloyl hydrazone modified guar gum adsorption material (GSA). GSA exhibited an abundant porous structure and was found to be an excellent adsorbent for the selective adsorption of cationic dyes ((methylene blue (MB), malachite green (MG)) with high q max of 1418.36, and 1375.58 ...
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A variety of issues, such as those concerning the environment, economics, sustainability, biocompatibility and biodegradability have prompted an ever-increasing demand for environmentally friendly materials. This has given rise to new fields of study that place a strong emphasis on natural-based products. Among bio-based polymers, gum polysaccharides are one of the most prevalent materials. They often come from microbes or plants as exudates, and they are used in a variety of industries. Compared to their synthetic equivalents, hydrogels based on polysaccharides provide several advantageous characteristics. Natural gum-based hydrogels have the potential to provide ecologically friendly products while also reducing the environmental contamination. This article provides a comprehensive analysis of natural gum-based hydrogels as adsorbents for wastewater treatment. The purpose of this review is to provide: (1) general design principles for natural gum-based hydrogels as adsorbents, (2) different kinds of natural gums-based hydrogels, including polymerization techniques, (3) measurement techniques for hydrogels adsorption, (4) The significance of natural gums-based hydrogels in removing organic pollutants (dyes, oils, pharmaceuticals, and phenols) and inorganic pollutants (heavy metal ions and nutrients) from wastewater were addressed, (5) future directions for the development of natural gums-based hydrogels as wastewater adsorbents to comprehend research gaps and limitations. The authors also hope that this review will spark interdisciplinary debates that will revolutionize the use of hydrogels based on natural gums as wastewater adsorbents.
... Many technologies have been applied to treat wastewater dyes, including photo-degradation (Hosseini, Abbasi, & Masteri-Farahani, 2022), catalytic degradation (Pandey, Do, Kim, & Kang, 2020), coagulationflocculation (Lima Beluci et al., 2019), membrane separation (Pei et al., 2022), adsorption (Abd Malek, Jawad, Ismail, Razuan, & Alothman, 2021), chemical oxidation , electro-flotation (Szpyrkowicz, 2005), solvent extraction (Bukman et al., 2020), reverse osmosis (Jing et al., 2021), etc. Among these methods, adsorption has the advantages of high efficiency, low cost, simple operation, high reusability, and is effective against a variety of pollutants, which is considered to be one of the most ideal strategies to remove dyes (Pereira, Rodrigues, Paulino, Martins, & Fajardo, 2021;Wen et al., 2022). Various adsorbents including activated carbon (Xiao et al., 2021), electrospun fiber (de Farias et al., 2022), film , hydrogels (Shao et al., 2023;Wu, Shao, Xie, Xiang, & Zhou, 2021;Yang et al., 2021), and cryogels (Gun'ko, Savina, & Mikhalovsky, 2013) have been developed for dye removal. ...
Article
Adsorbents with high adsorption capacity, sustainability, and reusability are desired in wastewater treatments. Herein, covalently crosslinked microporous cryogels with efficient removal of cationic dyes are fabricated by freezing radical copolymerization using methacrylated alginate (AlgMA) and sodium p-styrenesulfonate (NaSS). The chemical structure, morphology, and thermal stability of the AlgMA/PNaSS cryogels are characterized. Compared with the AlgMA/PNaSS hydrogels with the same chemical composition fabricated by thermal-initiated polymerization, the cryogels show higher adsorption of methylene blue. The AlgMA/PNaSS (with a mass ratio of 1:2) possesses the maximum adsorption capacity for MB with 2300 mg/g under alkaline condition. In addition, the adsorption process of AlgMA/PNaSS cryogels fits the pseudo-second order model and Freundlich model, respectively. The AlgMA/PNaSS cryogels also reveal selective adsorption capacity and reusability after regeneration, which own unchanged corrected adsorption capacity during five adsorption-desorption cycles. The AlgMA/PNaSS cryogels show great potential for use in wastewater treatments and intelligent separation.
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The importance of water for all living organisms is unquestionable and protecting its sources is crucial. In order to reduce water contaminants, like toxic metals and organic dyes, researchers are exploring different techniques, such as adsorption, photocatalytic degradation, and electrolysis. Novel materials are also being sought. In particular, biopolymers like guar gum and xanthan gum, that are eco-friendly, non-toxic, reusable, abundant and cost-effective, have enormous potential. Gum-based nanocomposites can be prepared and used for removing heavy metals and colored dyes by adsorption and degradation, respectively. This review explains the significance of gum-based nanomaterials in waste water treatment, including preparative steps, characterization techniques, kinetics models, and the degradation and adsorption mechanisms involved.
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Injectable hydrogel-based drug delivery has attracted more and more attention due to its sustained-release performance, biocompatibility, and 3D network. The present study showed whole pectin-based hydrogel as an injectable drug delivery system, which was developed from oxidized pectin (OP) and diacylhydrazine adipate-functionalized pectin (Pec-ADH) via acylhydrazone linkage. The as-prepared hydrogels were characterized by 1H NMR, FT-IR, and SEM techniques. The equilibrium swelling ratio of obtained hydrogel (i.e., sample gel 5) was up to 4306.65 % in the distilled water, which was higher than that in PBS with different pH values. Increasing the pH of the swelling media, the swelling ratio of all hydrogels decreased significantly. The results that involved the swelling properties indicated the salt- and pH-responsiveness of the as-prepared hydrogels. The drug delivery study presented that 5-FU can be persistently released for more than 12 h without sudden release. Moreover, the whole pectin-based hydrogel presented high cytocompatibility toward L929 cell lines, and the drug delivery system showed a high inhibitory effect on MCF-7 cell lines. All these results manifested that the acylhydrazone-derived whole pectin-based hydrogel was an excellent candidate for injectable drug delivery systems.
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Herein, Typha angustifolia was used as a charcoal source and chemically modified with a strong oxidizing agent, potassium permanganate (KMnO4), to obtain modified Typha angustifolia (MTC). Then, the green, stable and efficient CMC/GG/MTC composite hydrogel was successfully prepared by compounding MTC with carboxymethyl cellulose (CMC) and guar gum (GG) by free radical polymerization. Various variables that influence adsorption performance were explored, and optimal adsorption conditions were determined. The maximum adsorption capacity calculated from the Langmuir isotherm model was 805.45, 772.52, and 598.28 mg g-1 for Cu2+, Co2+, and methylene blue (MB), respectively. The XPS results revealed that the main mechanism of removing pollutants by adsorbent is surface complexation and electrostatic attraction. After five adsorption-desorption cycles, the CMC/GG/MTC adsorbent still exhibited good adsorption and regeneration capacity. This study provides a low-cost, effective and simple method for preparation of hydrogels from modified biochar, which has excellent application potential in the removal of heavy metal ions and organic cationic dye contaminants from wastewater.
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Pharmaceuticals and personal care products (PPCPs) are an emerging class of perilous pollutants due to their potential inimical impacts on ecosystems necessitating their abatement. Herein, an environmentally-affable and multifunctional acacia gum phthalate/ pectin hydrogel (AGP/PEC) was innovatively synthesised by microwave-assisted free-radical polymerisation for subsequent mefenamic acid (MFA) decontamination from synthetic wastewater. The physicochemical characteristics of AGP/PEC was studied through FTIR, XRD, BET, TEM, SEM-EDX and XPS characterisation techniques showing the existence of –OH and –COOH functionalities, rough surface with good surface area (18.95 m2/g) and porosity that contributed to high MFA uptake (93.45%) via hydrogen-bonding, electrostatic, pore-filling, π−π, and n−π interactions. The independent and interactive influences of operative variables on the adsorption capacity of AGP/PEC was statistically evaluated via central composite design of response surface methodology. The most-effective MFA uptake was attained at optimal operating conditions: initial solution pH (5.9), dosage (0.4 g/L), and time (28.5 min). Langmuir isotherm with Qm = 103.43 mg MFA/g and pseudo-second order kinetic models best-correlated the corresponding data. The Qm increased with temperature specifying an endothermic process, which was authenticated by positive ΔH⁰ (= 7.75 kJ/mol). The parameter, bT = 0.16 kJ/mol and ED = 2.12 kJ/mol, calculated from Temkin and Dubinin−Radushkevich isotherm models, respectively specified physisorption. The better adsorptive competence in real water along with an excellent reusable potential (87.1%) up to fifth cycle designated AGP/PEC as a potent adsorbent for practical purposes. These findings accentuated that AGP/PEC could be gainfully implemented as green and advanced multifunctional adsorbent material for removing residual MFA from wastewater.
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Environmental sustainability appraisal of adsorption for exclusion of the malachite green toxic dye was the center of attention in this work. The influenced goals were to analyze the consequences of novel composites fabricated by sodium alginate with guar gum and birm (SA@GG@B composites) by ion gelation. This work not only explains the feasibility of the sorbent and its application for the removal of dye stuff but also proclaimed various effects of different parameters affecting the removal efficiency. Adsorption processes were carried out in the batch process. The composite was characterized by SEM, which revealed that the irregular surface of composites has pores present for high adsorption, FTIR (for functional groups detection) reveals the presence of –OH group which provides attachment sites for dye, and BET (surface analysis) with a surface area of 5.01 m2/g shows that it has a wide surface area for greater adsorption process. Adsorption was performed on synthetic composites by varying different parameters like contact time, the concentration of sorbent and sorbate, and pH. Maximum adsorption was achieved (92.7%) at 100 ppm initial concentration, 120 min interaction time, and pH 9. Adsorption isotherms (Freundlich, Langmuir, Dubnin, and Elvoich isotherm) were applied in this work and evaluated the adsorption phenomenon and nature of adsorption. Freundlich adsorption capacity KF (9.45) reveals effective adsorption of dye by the proposed adsorbent. The kinetics models show that it was better with the pseudo-second-order reaction. Effective removal of malachite green by synthesized composites reveals their importance for the industrial water purification from hazardous dyes.
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Oily sewage poses a serious environmental risk normally; thus, herein, the modified guar gum (GG-SH) was prepared through rapid condensation reaction between polysaccharide and stearic hydrazide. GG-SH exhibited high removal efficiency of crude oil, the maximum adsorption capacity was calculated to be 2157.3 mg•g-1. The kinetics and isotherm statistical theories showed that the sorption of crude oil onto GG-SH was governed by pseudo-second-order, and Langmuir models, respectively. The removal rate was still high after six cycles of regeneration, indicating an outstanding technique to prepare polysaccharide-based material for the oily sewage treatment with high efficiency and recyclability.
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Rapid population growth and the resultant pollution of freshwater resources have created a water stress condition reducing the availability of safe and affordable water. Guar gum, a biocompatible macromolecule obtained from the endosperm of the seeds of Cyamopsis tetragonolobus, is a fascinating raw material for multifunctional adsorbents. This review assembled the work conducted by various researchers over the past few decades and discussed the structure, properties, and different modifications methods employed to develop versatile guar gum-based adsorbent. The paper also summarized the recent progress of guar gum-based nanocomposites for the remediation of multiple hazardous substances such as organic dyes, toxic heavy metal ions, oil-water separation as well as inhibiting the growth of bacterial pathogens. Thus, the important contribution of guar gum composites to safeguard the water quality is highlighted which will overcome the limitations and streamline the future course of innovative research.
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Herein the hydrazone-modified sodium alginate, being prepared with aldimine condensation through dihydrazide and dialdehydes sodium alginate, possessed extremely effective and selective removal of Pb²⁺, Cd²⁺, and Cu²⁺. Equilibrium adsorption data of biphthalate dihydrazidemodified sodium alginate was obeyed the Freundlich isotherm and pseudo-second-order kinetics models, which reflected that the adsorption process was mainly via the chemisorption, and the maximum adsorption capacities for Pb²⁺, Cd²⁺, and Cu²⁺ were found to be 668.42, 472.37, and 200.10 mg g⁻¹, respectively. The thermodynamic parameter for the sorption demonstrated the process was endothermic and spontaneous. Fourier Transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) analyses revealed combination of chelation interactions coordination and ion exchange of nitrogen and oxygen atoms with heavy metal ions, and the density functional theory (DFT) calculations confirmed that heavy metal ions formed a stable five membered ring coordination structure with the nitrogen and oxygen atoms in hydrazone groups. Moreover, the adsorption efficiency was not significantly reduced after 10 adsorption–desorption recycles. To sum up, this study provides a new strategy for the removal of heavy metal ions by hydrazone-modified sodium alginate with great potential for wastewater treatment.
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Herein, an ultralong polypyrrole nanowires-coated stainless steel mesh ([email protected]) was successfully prepared to cope with the on-demand separation of oil/water emulsions as well as dyes adsorption via electrodeposition. The as-prepared [email protected] could be switched from superhydrophilic to hydrophobic under electric field for at least 50 times. Benefiting from the high porosity and its selective wettability, the [email protected] exhibited excellent separation efficiency of up to 99.88 % and high filtration flux of up to 2984 L m⁻² h⁻¹ for both oil-in-water and water-in-oil emulsions, even for the high viscous crude oil-in-water emulsion. Thanks to the surface charge, abundant aromatic rings of PPy, and porous structure, [email protected] also achieved selective adsorption of cationic or anionic dyes with high efficiency (up to 99.28 %) under diverse pH conditions. Moreover, the [email protected] also displayed a strong chemical resistance and mechanical stability under harsh conditions such as extreme temperature, corrosive environments, and various friction tests. Combined with a simple and environmental-friendly fabrication process, the high-performance membrane [email protected] has promising applications in the separation of oil/water emulsions and the adsorption of dyes.
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Currently, fluorides and long-chain aliphatic compounds are the most frequent low surface energy chemicals utilized in the preparation of superhydrophobic coatings, but associated environmental risks and instability restrict their potential application in oil-water separation. This research described a superhydrophobic coating based on rosin acid and SiO2 modified cotton fabric to overcome this challenge. By means of spray impregnation and UV-assisted click reaction, sulfhydryl modified rosin acid (RA), Octavinyl-POSS, and SiO2 were grafted onto the surface of cotton fabric to obtain RA-SiO2 superhydrophobic coating with rough surfaces such as lotus leaf and low surface energy. The RA-SiO2 superhydrophobic coating had favorable self-cleaning ability, and also adsorbed various light and heavy oils to achieve efficient separation of oil-water mixtures. The separation efficiency was 96.3% and the permeate flux was 6110.84 (L⋅m⁻²⋅h⁻¹) after 10 repetitions. The RA-SiO2 superhydrophobic coating was found to be effective in separating oil-in-water and oil-in-water emulsions, and the separation mechanism was elaborated. In addition, it could effectively separate emulsions even after mechanical abrasion and chemical immersion, and had excellent stability. The fluorine-free and environmentally friendly low-cost superhydrophobic coating based on rosin acid is expected to play a significant potential in oil-water separation applications due to its excellent separation performance.
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In this work, a novel polydopamine and β-CD polymer co-decorated magnetic graphene oxide composite adsorbent (PDA/MGO/CA-CD) was facilely constructed, and systematically characterized by various characterization techniques. Subsequently, it was applied as a versatile adsorbent for purification of cationic dyes Methylene blue, Malachite green, and Crystal violet in wastewater. Under optimal conditions, the maximum adsorption capacities of PDA/MGO/CA-CD towards MB, MG, and CV were 1372.32, 822.39, and 570.79 mg/g, respectively. The adsorption kinetics investigate demonstrated that the adsorption experimental data fitted well with the pseudo-second-order kinetic model. Simultaneously, the adsorption isotherms data indicated good correlation coefficient and low error function for the Langmuir isotherm model. The thermodynamic consequences showed that the adsorption of cationic dyes on PDA/MGO/CA-CD was a spontaneous and endothermic process. Interestingly, the PDA/MGO/CA-CD can selectively capture cationic dyes from mixed cationic/anionic dye solutions. As-fabricated adsorbent possesses abundant functional groups which could adsorption cationic dyes via electrostatic interaction, hydrogen bonding, Yoshida H-bonding, π-π conjugation interaction, n-π interaction, and “host-guest” interaction. It was eventually revealed that the as-prepared PDA/MGO/CA-CD adsorbent was easy to be separated after adsorption and exhibited good reusability. More importantly, application on real water samples confirmed the high performance and potential of as-fabricated adsorbent for real cationic dyes remediation of environmental.
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Dyes and heavy metal ions are of great interest for environmental studies as they are common pollutants in industrial applications. Therefore, development of innovative adsorbents has received tremendous interest in wastewater treatment studies. In this study, a new hybrid adsorbent (g-C3N4/AFP) was prepared by modifying porous graphitic carbon nitride surface (g-C3N4) with 2-amino fluorene polymer (AFP) and investigated its adsorptive behaviour for removal of representative dyes and heavy metal from aqueous solution. Experimental data obtained from batch tests were analysed using two parameters (Freundlich, Langmuir and Dubinin–Radushkevich) and three parameters (Sips) isotherm models. Langmuir isotherms were the best model to describe the experimental results of Methylene blue (MB) and Malachite green (MG) dye adsorptions, while Freundlich isotherms were the best for Cu (II) ions. Sips isotherm model was found to have the highest regression coefficient (≥0.99) among the two-parameters isotherms studied. The maximum adsorption capacities of g-C3N4 and g-C3N4/AFP were found to be 226.88 and 327.83 for MG, 85.73 and 221.85 for MB and 184.51 and 452.19 mg g⁻¹ for Cu (II), respectively. This increase in adsorption capacity can be explained by the improved textural properties of the new hybrid adsorbent and the presence of multiple functional groups in its structure. A possible adsorption mechanism was suggested using FTIR and pHpzc data.
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Development of multifunctional materials for efficient treatment of complex effluents containing water-insoluble oils and water-soluble dyes is highly desired. In this work, a multifunctional Ag/AgCl decorated CO2-responsive cotton membrane (Ag/[email protected]) was successfully fabricated for simultaneous or successive removal of oils and dyes (both cationic and anionic dyes). Through achieving protonation and deprotonation in response to the CO2, the as-prepared Ag/[email protected] could reversibly switch from superhydrophobic (uncharged) state to superhydrophilic (charged) state. Moreover, the Ag/AgCl endowed the Ag/[email protected] with visible light photocatalytic activity. Based on these ingenious features, the as-prepared Ag/[email protected] could bidirectional separation of various oil/water mixtures with high separation efficiencies (≥97.50%), accompanying with satisfactory fluxes, due to controllable wettability upon CO2 stimulation. Moreover, the as-prepared Ag/[email protected] exhibited stable oil/water separation property, even under various adverse environmental conditions. Meanwhile, the Ag/[email protected] could eliminate the dyes in wastewater through adsorption for anionic dyes and photocatalysis for cationic dyes. The results presented that MB (anionic dye) could be efficiently removed by the Ag/[email protected] under both static and dynamic states in the presence of CO2. The maximum static adsorption capacity of the Ag/[email protected] toward MB reached 2168.47 mg g⁻¹ with a fast adsorption rate (12 min of adsorption equilibrium time). For the removal of cationic dyes, the photo-degradation efficiency of the Ag/[email protected] toward RhB (cationic dye) was up to 94.30% within 6 h. Most importantly, the as-prepared Ag/[email protected] exhibited photo-induced self-cleaning performance due to the existence of Ag/AgCl, which endowed it with excellent recyclability. Additionally, the as-prepared Ag/[email protected] displayed outstanding antibacterial activity. In summary, the Ag/[email protected] could be viewed as a satisfactory material for oil/water separation and dyes removal and exhibits great potential in wastewater remediation.
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In this study, the SDS/CTAB@Mt composite as a novel adsorbent has been prepared via a facile synergistic effect of cationic surfactant (CTAB) and anionic surfactant (SDS) for the modification of montmorillonite, and it was utilized to remove malachite green (MG) from aqueous solutions. The structure and the morphology of the SDS/CTAB@Mt composite were characterized by X-ray diffraction (XRD), Fourier Transform Infra-Red (FT-IR) spectroscopy, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive Analysis of X‐rays (EDAX), and N2 adsorption/desorption isotherms (BET method). The SDS/CTAB@Mt composite was found to be highly negatively surface charged, and showed good adsorption properties for MG molecules, reaching a maximum dye adsorbed amount of 1021.45mg/g. Further, at the equilibrium, the experimental adsorption isotherms were in good agreement with the theoretical predicted data by the Langmuir model (R2 = 0.99), indicating that the MG molecules were homogenously adsorbed and formed a monolayer on the SDS/CTAB@Mt surface. Moreover, the adsorption kinetics data were well fitted with pseudo-second-order model (R2 = 0.99). From the adsorption temperature effect study, the thermodynamic parameters, such as G, ΔH and ΔS were assessed, and their values revealed that the adsorption reaction was spontaneous, exothermic and resulted in a decrease of the MG adsorbed molecules randomness on the adsorbent surface. Finally, a new adsorption mechanism was proposed and confirmed that the MG molecules adsorption from water onto the SDS/CTAB@Mt adsorbent resulted from synergistic effect of the hydrophobic and the hydrophilic interactions.
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Adsorption of heavy metals by natural polymeric composites has attracted extensive attention due to their abundance, low cost, and eco-friendliness, but these composites tend to have low adsorption capacity, long response time and poor selectivity. Therefore, it is critically desired to develop an ecofriendly adsorbent that can remove heavy metal ions efficiently and quickly from aqueous solution. Here, a novel polyethyleneimine functionalized chitosan-lignin (PEI-CS-L) composite sponge adsorbent with nanowall-network structures is synthesized by cross-linking and lyophilization. Notably, the as-prepared adsorbent could remove Hg(II) ions selectively from aqueous solution with high efficiency at a very quick response time, reaching > 83.5% of the ultimate adsorption within just 1 min. This is attributed to the evenly interconnected porous structure of composite sponge with nanoscale-wall structures which increase the distribution of functional groups, and leading to the quick complexation of heavy metal ions with surface functional groups. It is worth noting that PEI-CS-L sponge has excellent reusability, and the adsorption capacity only decreased by 4.09% after 5 cycles of adsorption and desorption. Considering its eco-friendliness, high efficiency and low cost, the developed PEI-CS-L sponge holds great promise in removing Hg(II) ions from wastewater.
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A polyampholytic superabsorbent polymer (PASAP), sodium alginate-g-(polyacrylic acid-co-allyltrimethylammonium chloride) (SA-g-(PAA-co-PTM)), was prepared by free-radical graft copolymerization and characterized. The polymer exhibited pH-dependent swelling behaviors with extremely high swelling ratios, and was saline tolerant. The dye adsorption properties of SA-g-(PAA-co-PTM) were investigated using methylene blue (MB) as a cationic dye model. It was found that its dye adsorption capacity was significantly affected by the TM content in PASAP and pH of dye solution. The dye adsorption kinetics and isotherm obey the pseudo-second-order kinetic model and the Langmuir isotherm model, respectively, and the adsorption process is chemisorption in nature. In addition, SA-g-(PAA-co-PTM) exhibited high MB adsorption capacities in a wide pH range and reusability in at least five adsorption-desorption cycles, indicating its great application potentials as the adsorbent for dye removals from effluents.
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The extended Langmuir (EL) model is a popular multicomponent adsorption equilibria model, which can be based on single component Langmuir isotherms fitted on pure component data. Such explicit models are preferred over their implicit counterparts due to a lower computational requirement. An important shortcoming of the EL model is its inability to capture the adsorbate size effect occurring when the saturation capacities of pure component Langmuir isotherms are dissimilar. In contrast, this size effect is captured by the ideal adsorbed solution theory (IAST), which is centered on a set of implicit equations. In this work, we present an explicit multicomponent adsorption model for components with uneven saturation capacities obeying the Langmuir isotherm equation. This model predicts the expected change in selectivity with mixture composition, and even a selectivity reversal at high pressure when the adsorbates have significantly different molecular sizes. The model is extendable to any number of components, reduces to the Langmuir equation for pure components and to the EL equation when all saturation capacities are equal. The newly proposed model can be used to approximate the IAST and upgrade the EL model without introducing new parameters. Especially for binary mixtures, this model (Eqs. 12–14) offers a simple improvement of the EL model in predicting the experimental adsorption of light alkanes on 13X and 5A zeolites. The presented model is also applied to describe phase-changing adsorbents, in combination with the osmotic framework adsorbed solution theory (OFAST). Open image in new window
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Adsorption, a popular technique for removing azo dyes from aqueous streams, is influenced by several factors such as pH, initial dye concentration, temperature and adsorbent dosage. Any strategy that seeks to identify optimal conditions involving these factors, should take into account both kinetic and equilibrium aspects since they influence rate and extent of removal by adsorption. Hence rigorous kinetics and accurate equilibrium models are required. In this work, the experimental investigations pertaining to adsorption of acid orange 10 dye (AO10) on activated carbon were carried out using Central Composite Design (CCD) strategy. The significant factors that affected adsorption were identified to be solution temperature, solution pH, adsorbent dosage and initial solution concentration. Thermodynamic analysis showed the endothermic nature of the dye adsorption process. The kinetics of adsorption has been rigorously modeled using the Homogeneous Surface Diffusion Model (HSDM) after incorporating the non-linear Freundlich adsorption isotherm. Optimization was performed for kinetic parameters (color removal time and surface diffusion coefficient) as well as the equilibrium affected response viz. percentage removal. Finally, the optimum conditions predicted were experimentally validated.
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Water-soluble hyperbranched polyamine functionalized multiwalled carbon nanotubes nanocomposite (WHPA-OMCNT) was successfully prepared and applied to water remediation in this paper. WHPA-OMCNT was characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), zeta potential, scanning electron microscopy (SEM) and transmission electron microscope (TEM) analyses. WHPA-OMCNT exhibited excellent adsorption performance for removal of organic dyes e.g., methylene blue (MB), malachite green (MG) and methyl violet (MV). The equilibrium adsorption capacity was 800.0 mg g⁻¹ for MB, 840.3 mg g⁻¹ for MG and 970.9 mg g⁻¹ for MV under the optimal conditions. The pseudo-second order equation and the Langmuir model exhibited good correlation with the adsorption kinetic and isotherm data for all three pollutants, respectively. The thermodynamic results (ΔG < 0, ΔH < 0, ΔS < 0) implied that the adsorption process of MB, MG and MV was feasible, exothermic and spontaneous in nature. A possible adsorption mechanism has been proposed, where H-bonding, electrostatic attraction and π-π stacking interactions dominated the adsorption of the organic dyes. In addition, the excellent reproducibility endowed WHPA-OMCNT with the potential for application in water treatment.
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Due to the unique physical and chemical characteristics of hydrogels, such as hydrophilicity, swellability, and modifiability, there is increasing research interest in the development and application of novel hydrogels in water and wastewater treatment. Hydrogels have exhibited superior performance in the adsorptive removal of a wide range of aqueous pollutants including heavy metals, nutrients, and toxic dyes. However, there remain certain challenges which need to be addressed in order to evolve hydrogel based treatment systems from the lab-scale to practical applications. This review provides a coverage of the latest developments in the application of hydrogels for the adsorptive removal of aqueous pollutants. A holistic overview of different steps involved in the hydrogel based treatment systems is provided, and the influencing factors and mechanisms of pollutants removal are reviewed. Major challenges pertaining to adsorption kinetics, operational pH range, interference, and hydrogel recovery are examined. Important considerations such as stability and reusability of hydrogels and resource recovery are also discussed, for economic and sustainability concerns.
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High salinity and natural organic matter are both known to facilitate migration of toxic or radioactive metals in geochemical systems, but little is known on their combined effect. We investigated complexation of Tb(III) and Eu(III) (as analogues for trivalent actinides) with fulvic acid and their adsorption onto a natural clay in the presence of NaCl, MgCl2 and CaCl2 up to very high ionic strengths. ¹⁶⁰Tb, ¹⁵²Eu and ¹⁴C-labelled fulvic acid were employed as radiotracers, allowing investigations at very low concentrations according to probable conditions in far-field scenarios of nuclear waste repositories. A combined Kd approach (Linear Additive Model) was tested for suitability in predicting solid–liquid distribution of metals in the presence of organic matter based on the interactions in the constituent subsystems. In this analysis, it could be shown that high ionic strength does not further enhance the mobilizing potential of humic matter. A quantitative reproduction of the influence of fulvic acid failed for most systems under study. Assumptions and limitations of the model are discussed.
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In this work, a porous multi-functional biomass carbon was prepared by acid-base modification method, which realized the reuse of waste cotton material. Then, the modified biochar was combined with the acrylic-based hydrogel by radical polymerization, and the biochar acrylic-based hydrogel (CS/EDTA/CBC) composite with chitosan and ethylenediamine tetraacetic acid was successfully prepared. This not only increases the adsorption performance of the adsorbent but also improves the stability of hydrogel. These characteristics provide high-efficiency adsorption capacity for pollutants (1105.78 mg g⁻¹ for Pb²⁺, 678.04 mg g⁻¹ for Cu²⁺, and 590.72 mg g⁻¹ for methylene blue (MB)), which is far superior to most reported adsorbents. Meanwhile, the adsorbent would have a strong chemical interaction with Pb²⁺ and Cu²⁺, can form a stable chelating structure, and showed stronger selective adsorption. The adsorption process is more suitable for the Langmuir isotherm and follows a pseudo-second-order kinetic model, which indicates that the adsorption is a single-layer adsorption, and the rate-limiting step is a chemical chelation reaction. XPS results confirmed that surface complexation and electrostatic attraction are the main mechanisms of the adsorption reaction. After five cycles, the adsorption capacity of the adsorbent and the recovery of heavy metal ions remained at a high level.
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Manufacturing multifunctional, stable, and recyclable adsorbents for treating contaminants with charge diversity from wastewater remains challenging. Herein, a β-cyclodextrin/magnetic graphene oxide/triethylenetetramine functionalized magnetically polyampholyte hydrogel adsorbent P(AA-MMA)/MGO/CA-CD/NH2 with high-density carboxyl and amino groups was prepared via simple one-pot polymerization and ammonolysis. The morphology structure, physicochemical, mechanical, and magnetic characteristics of as-resulting hydrogel adsorbent have been comprehensively investigated through various characterization methods. Its adsorption behaviors towards cationic/anionic dyes (Methylene blue (MB), Malachite green (MG)/Congo red (CR)) and heavy metal ion (Cu²⁺) were further systematically investigated through batch adsorption and column filtration experiments. The pseudo-second-order kinetic and Langmuir isotherm models were revealed to well describe the adsorption behaviors of hydrogel for dyes and heavy metal ion. Besides, by altering the solution pH could be endowing hydrogel with selective and simultaneous adsorption properties towards cationic and anionic dyes. Meanwhile, as-designed adsorbent has synergistic adsorption performance towards anionic dye and cationic heavy metal ion. The adsorption mechanism of hydrogel towards contaminants was studied by FTIR, Raman, and XPS analyses. Additionally, the as-prepared adsorbent displayed no significant adsorption capacity loss even after eight adsorption-desorption cycles, manifesting that it is of superb recyclability and stability. Finally, it was demonstrated that the adsorption column packed with hydrogel could quickly purify contaminants in the model textile wastewater through filtration.
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Many researchers focus on the conversion of waste into reusable materials in recent years. In this study, waste expanded polystyrene foam (WEPS) and 1,2,4-benzenetricarboxylic anhydride (BTA) were used as raw materials to prepare recyclable acylating waste expanded polystyrene adsorbent (WEPS-BTA) by Friedel-Crafts reaction and to recover dyes effectively. The WEPS-BTA was characterized by FT-IR, TGA, BET and SEM. WEPS-BTA showed good performance in a wide range of pH (2-12) and high concentration brine (0.2 M). The maximum adsorption capacity to methylene blue, safranine T, and malachite green were 859.9, 1036.7, and 1197.3 mg/g, respectively. It was found that Freundlich model and pseudo-second-order kinetics could describe the adsorption behavior. This is a heterogeneous, endothermic, and spontaneous multiple adsorption process. The plausible adsorption mechanism was explained by kinetic model, thermodynamic discussion, SEM-EDS, XPS and FT-IR. In addition, WEPS-BTA showed satisfactory reusability without significant loss of the removal efficiency of the three dyes after 5 cycles. Therefore, WEPS-BTA has the advantages of simple synthesis, efficient adsorption, easy recycling and reuse, and stable performance in a harsh environment. Converting waste polystyrene foam to an adsorbent is an economic way of handling waste and providing material for wastewater remediation simultaneously.
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Recently, the use of magnetic sorbents has gained a spread attention due to their eco-friendly characteristic, ease of separation and low cost. Herein, a novel biocomposite sorbent magnetic pine cone gel beads (MPCB) was synthetized and investigated for the single and the simultaneous removal of Cu(II) and Cr(VI) from aqueous solution. Pine cones waste materials were first magnetized with Fe3O4 nanoparticles then were encapsulated in calcium gel beads. The physicochemical properties of the prepared MPCB were characterized via scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction and Fourier transform infrared spectrometry (FTIR) analysis. The influences of pH, contact time and initial concentration of metal ions on the sorption process were examined. The adsorption mechanism was investigated; it mainly involved complexation/chelation with surface functional groups, electrostatic interaction and ion exchange. A physical model was adopted to attribute new physico-chemical interpretations of the adsorption mechanism. The kinetic results showed good correlation with pseudo second-order model and the equilibrium data were fitted well to the Langmuir isotherm model with maximum adsorption capacity of 68.64 and 212.22 mg g⁻¹ for Cu(II) and Cr(VI) respectively. In the multi-components system, both competitive and synergistic effects were observed. An antagonism effect was exerted by Cu(II) ions on Cr(VI) sorption while Cu(II) adsorption was not affected and even slightly enhanced by the presence of Cr(V) ions. The competitive sorption behavior of metal ions was analyzed by the modified competitive Langmuir model which provides good fit for the Cu experimental data. This study proves that the MPCB hold great promise for using as effective sorbent for potentially toxic metals remediation.
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In this work, we successfully synthesized novel polymer gel beads based on functionalized iron oxide (Fe3O4), activated charcoal (AC) particles with β-cyclodextrin (CD) and sodium alginate (SA) polymer (Fe3O4/CD/AC/SA), by a simple, reproducible and inexpensive method. These beads proved to be versatile and strong adsorbents with magnetic properties and high adsorption capacity. The composites were characterized by Fourier transform infrared, scanning electron microscopy – energy dispersive X-ray spectroscopy, vibrating sample magnetometry, adsorption at -196 ºC, high resolution transmission electron microscopy, thermogravimetric analysis and point of zero charge measurements. Two dyes, two drugs and one metal were used to test the adsorption capability of the prepared polymer nanocomposite. The adsorbent showed good removal efficiencies for the studied pollutants, especially the cationic dyes and the metal, when compared to other low-cost adsorbents. The saturated adsorption capacity of Fe3O4/CD/AC/SA reached 5.882 mg g⁻¹for methyl violet (MV), 2.283 mg g⁻¹for brilliant green (BG), 2.551 mg g⁻¹ for norfloxacin (NOX), 3.125 mg g⁻¹for ciprofloxacin (CPX), 10.10 mg g⁻¹ for copper metal ion (Cu(II)). The adsorption isotherm studies show that data fitted well with Langmuir and Temkin isotherms models. The kinetic data showed good correlation coefficient with low error function for the pseudo-second order kinetic model. The data analysis was carried out using error and regression coefficient functions for the estimation of best-fitting isotherm and kinetic models, namely: chi-square test (χ²) and sum of the squares of errors (SSE). The activation energy was found to be 47.68 kJ mol⁻¹ for BG, 29.09 kJ mol⁻¹ for MV, 28.93 kJ mol⁻¹ for NOX, 4.53 kJ mol⁻¹ for CPX and 17.08 kJ mol⁻¹ for Cu(II), which represent chemisorption and physisorption behavior of sorbent molecules. The polymer composites can be regenerated and easily separated from aqueous solution without any weight loss. After regeneration, the Fe3O4/CD/AC/SA beads still have good adsorption capacities up to four cycles of desorption and adsorption. The results indicate that the polymer gel beads are promising adsorbents for the removal of different categories of toxicants (like dyes, drugs and metal) in single adsorbate aqueous systems. Thus, the novel Fe3O4/CD/AC/SA beads can be effectively employed for a large-scale application as environmentally compatible materials for the adsorption of different categories of pollutants.
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Due to the rapid development of modern industry, the coexistence of antibiotics and inorganic heavy metals pollutants in wastewater has become a universal phenomenon. Therefore, developing efficient and eco-friendly photocatalyst for mixed pollutants degradation is significant. In this work, a well-designed phosphorus and sulfur co-doped g-C3N4 with feeble N vacancies catalyst (P/S-g-C3Nx) was fabricated by supramolecular self-assembly method, and was applied to remove berberine hydrochloride (BH) and Cr(VI) simultaneously with the synergy of adsorption-photocatalysis. A series of experiments was conducted to unveil the synergistic mechanism. The kinetic models indicated that the adsorption of P/S-g-C3Nx improved the BH removal process by accelerating the photo-degradation, because the adsorption rate > surface degradation rate > bulk degradation rate. Besides, the photo-degradation process improved the BH removal rate by regenerating the adsorption sites of P/S-g-C3Nx. Moreover, from the experiments in BH-Cr(VI) mixed solution system, the existence of BH also enhanced the surface adsorption of Cr(VI) in P/S-g-C3Nx sample, and the reduction rate of Cr(VI) was also promoted with the existence of BH. Overall, the results of this investigation suggest that the adsorption-photocatalysis synergy method is an efficient way to eliminate organic pollutant and Cr(VI) simultaneously.
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Herein, we reported the preparation of novel antibacterial nanocomposites based on biodegradable polymers. The nanocomposites were applied as capable adsorbent for removing of malachite green (MG) dye, as well as inhibiting of E. coli and S. aureus growth as the most common pollutants for water. The grafted xanthan gum with poly(vinylimidazole) (XG-g-PVI) nanocomposites were synthesized in the presence of different Montmorillonite (MMT) nanoclays concentrations (1%, 3% and 5%). The prepared modified XG nanocomposites were detected through XRD, SEM-EDX, FTIR and TEM. The maximum adsorption MG capacity was determined as 99.99% (909.1 mg/g) in basic medium at 30 o C for 90 min. The adsorption isotherm for removal of MG dye was studied against different models like Langmuir, Freundlich, Temkin, FloryHuggins isotherm models, however, the adsorption results were good fitted with Langmuir isotherm model (R2 = 0.9942). Additionally, various adsorption kinetic models: pseudo-first order, second order, pseudo-second order, and intra-particle diffusion models were studied for adsorption mechanism of MG dye on top of prepared nanocomposite surface. Finally, the antibacterial activity outcomes displayed that the prepared XG-g-PVI/MMT nanocomposites had excellent inhibition growth for bacteria and the antibacterial activity increased abruptly with the increased of MMT nanoclay concentrations.
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Chitosan-deep eutectic solvent (DES) beads were prepared from chitosan and DESs. The DESs used were choline chloride-urea (DES A) and choline chloride-glycerol (DES B). Both chitosan-DES beads were used to remove malachite green (MG) dye from an aqueous solution. The optimum pH for chitosan-DES A was recorded at pH 8.0 while optimum pH for chitosan-DES B was pH 9.0. The maximum adsorption capacity obtained for chitosan-DES A and chitosan-DES B were 6.54 mg/g and 8.64 mg/g, respectively. The optimum conditions for both chitosan-DES beads to remove MG were 0.08 g of adsorbent and 20 min of agitation time. Five kinetic models were applied to analyse the data and the results showed that the pseudo-second-order and intraparticle diffusion model fitted best with R2 > 0.999. For the adsorption capacity, results show that the Freundlich and Langmuir adsorption isotherms fitted well with chitosan-DES A and chitosan-DES B, respectively. The maximum adsorption capacities (qmax) obtained from chitosan-DES A and chitosan-DES B were 1.43 mg/g and 17.86 mg/g, respectively. Desorption indicated good performance in practical applications.
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The toxic heavy metals contamination in water bodies is one of the major concerns in many countries. Copper and lead are the two common toxic metals present in aquatic environments due to their extensive usage in various industries for diverse applications. The present study deals with the removal of these two toxic heavy metal ions using activated bentonite-alginate (ABn-AG) composite beads which are easily separated and recovered after adsorption reaction. The composite bead was prepared by adapting the ionic gelation method and the materials; i.e., raw bentonite (BnR), activated bentonite (ABn) and ABn-AG were characterized by XRD, BET surface area, TGA-DTA, FT-IR, SEM analyses. The nitrogen adsorption–desorption isotherm obtained for the materials were the type IV isotherm with characteristics H3 hysteresis loops indicating the presence of mesopores with slit-shaped pores. Batch experiments showed that reasonably high percent removal was achieved even at highly acidic conditions, i.e., 58% of Cu²⁺and 77% of Pb²⁺were removed at pH 2.0. The removal was fast during the initial contact time and the adsorption data obtained at various contact time were fit well to the pseudo-second order kinetic model. The maximum sorption capacity for Cu²⁺ was found to be 17.30 mg/g whereas Pb²⁺ was found to be 107.52 mg/g. The presence of MgCl2, NaCl and KCl did not cause significant influence on the removal of Cu²⁺ and Pb²⁺ using ABn-AG. Binary adsorption study suggested that Cu²⁺ and Pb²⁺ were removed through different binding sites present in ABn-AG. Reusability tests showed that removal of Cu²⁺ and Pb²⁺ decreased by 10% only after the same material was reused for 5 times indicating that ABn-AG is a highly robust material and can be reuse for several times without losing its efficiency. Thus, this study suggested that ABn-AG composite beads can be employed as an efficient adsorbent for the removal of Cu²⁺ and Pb²⁺ from aqueous waste.
Article
A novel bio-adsorbent named SA-PAM/GO hydrogel composites was synthesized through free radical polymerization. The structure and performance were characterized and analyzed by BET, SEM-EDS, FTIR and TGA. After modification, the BET surface area increased more than tripled, which was consistent with SEM results. Under optimal conditions, the maximum adsorption capacity of Cu²⁺ and Pb²⁺ were 68.76 mg/g and 240.69 mg/g, respectively. In addition, the research of kinetics and isotherms displayed that the pseudo-second-order kinetic model and the. Langmuir isotherm model fitted the data well. After further research, the different adsorption mechanism including physical adsorption, chemical adsorption and electrostatic interactions were discussed. The chemical adsorption accompanying the ion exchange process was confirmed as the staple adsorption mechanism. Furthermore, the adsorbent still maintained good adsorption capacity after 5 cycles of adsorption-regeneration. Therefore, the SA-PAM/GO hydrogel composites have potential to remove the heavy metal ions from water body effectively.
Article
In this paper, a new nanobiomaterial, alendronate hydroxyapatite (AL-HAP), was synthesized by the conventional co-precipitation method with alendronate (AL) as dopant, and applied in the removal of heavy metal contaminants for the first time. The characterization results showed that the crystallinity of the AL-HAP nanocomposite biomaterials after doping has been greatly deteriorated, and the pore volume and pore size increased. When the doping amount of AL was 10%, the maximum adsorption capacity of AL-HAP for Pb2+, Cd2+ and Cu2+ can reach 1431.8, 469 and 226.6 mg/g, respectively, which was much higher than that reported in other literature. Meanwhile, the adsorption mechanism of AL-HAP for heavy metal ions was discussed from both the views of experimental and Multiwfn program theoretical calculation based on density functional theory (DFT). Quantitative molecular surface analysis was carried out for the first time to study the minimum points and the positions of electrostatic potential (ESP) and average local ionization energy(ALIE), as well as the exact values, giving more accurate and reliable analysis conclusions for the reaction sites and binding mode. In addition, the independent gradient model (IGM) method was also firstly applied to investigate the interactions between AL and HAP or AL-HAP nanocomposite with metal ions. AL-HAP is a potential adsorption material for heavy metal wastewater treatment and soil remediation because of its advantages such as convenient synthesis, excellent adsorption performance and no secondary pollution.
Article
In this research, sulfonated chitosan (S-CS) was prepared by hydrothermal grafting reaction using 4-formyl-1,3-benzene disulfonate and glutaraldehyde as a cross-linker reagent. Batch adsorption experiments were performed to demonstrate the adsorptive properties of S-CS with a cationic dye (methylene blue; MB) as a model organic pollutant. The effect of the solution pH (3−12), initial dye concentration (50–200 mg L⁻¹), contact time (0–24 h) and temperature (30–50 °C) on the relative removal of MB were studied. The kinetics of adsorption for MB showed a good correlation with the pseudo-second order kinetic model, while the adsorption isotherm at equilibrium was conformed to the Temkin model (R² > 0.99). The maximum adsorption capacity, qm was 351.7, 326.1 and 302.4 mg g⁻¹ at 303, 313 and 323 K, respectively. Owing to the simpler preparation method, relatively high adsorption capacity and regeneration ability, S-CS represents a promising adsorbent for the controlled MB removal and for other related organic dye pollutants from aqueous solution.
Article
Chemical hydrogels have been extensively applied to the removal of heavy metal pollutants. However, most of chemical hydrogels inevitably contain toxic chemical crosslinker residues, which impose serious threats on the environment. Herein, a novel eco-friendly physically-crosslinked double-network hydrogel of chitosan/sodium alginate/calcium ion (CTS/SA/Ca²⁺ PCDNH) was prepared by the combination of the semi-dissolution acidification sol-gel transition method with the internal gelation method. The PCDNH is formed via the physical crosslinking of sustainable biopolymers, which avoids the excessive use of toxic chemical reagents. In addition, the PCDNH exhibits significantly better mechanical properties than the single-network physical hydrogel crosslinked via electrostatic interactions, which overcomes the weak mechanical properties of physical hydrogels. The formation mechanism and structure of the hydrogel were determined by Fourier-transform infrared spectroscopy (FTIR), ¹³C solid state nuclear magnetic resonance spectroscopy (¹³C-SSNMR) and scanning electron microscopy (SEM). The heavy metal ions adsorption mechanism was explored by X-ray photoelectron spectroscopy (XPS) analysis. The adsorption kinetics, isotherms and thermodynamics were further studied to understand the adsorption mechanism. Our work has provided a new method for the fabrication of natural polymers-based eco-friendly, low-cost and robust physical hydrogels for the heavy metal ions removal.
Article
Herein, porous sodium alginate/graphite based hybrid hydrogel was fabricated as an effective adsorbent for organic pollutant. Sodium alginate was modified through graft polymerization of acrylic acid and subsequently loaded with graphite powder to enhance its adsorption capability. The synthesized sodium alginate cross-linked acrylic acid/graphite (NaA-cl-AAc/GP) hydrogel composite was utilized in the removal of malachite green (MG) dye from aqueous solution using batch adsorption experiments. The NaA-cl-AAc/GP hydrogel composite was characterized by infrared spectroscopy, Raman spectroscopy, thermo-gravimetric analysis, scanning electron microscopy, x-ray photoelectron spectroscopy and x-ray diffraction. Under optimized experimental conditions, a maximum adsorption capacity of 628.93 mg g-1 was attained for malachite green dye. Moreover, the adsorption process could be well described by the Langmuir isotherm model and pseudo-second-order kinetic model. The hydrogel composite also showed 91% adsorption after three consecutive cycles of dye adsorption-desorption. Therefore, the NaA-cl-AAc/GP hydrogel composite is a potentially favourable material towards dye pollution remediation owing to its better swelling rate, environment friendliness, high adsorption potential and regeneration capability.
Article
Wastewater containing highly toxic, non-biodegradable and carcinogenic organic dyes and metal ions has been regarded as a severe threat to ecological environment and human health. Thus, it is of great significance to develop an effective approach to purify this kind of wastewater. Herein, novel magnetic adsorbent [email protected] was facilely prepared by coating anionic polyacrylamide-modified chitosan (CS-PAA) on the surface of silica-combined Fe3O4 (FS). The morphology, structure, physic-chemical and magnetic properties of as-prepared [email protected] were fully characterized by various characterization techniques. Its adsorption behaviors towards cationic dyes and metal ions were systematically investigated in single systems, binary systems, and model wastewater. [email protected] was proved to have superior adsorption capacities of 2330.17 and 1044.06 mg g⁻¹ respectively for crystal violet and methylene blue at 318.15 K, much higher than other reported adsorbents. Besides, [email protected] exhibited a pH-independent adsorption capability for metal ions, as demonstrated in single systems and in metal ion-dye binary systems, thus it could be used to treat a variety of metal ion wastewaters with different pH values. Moreover, [email protected] could be effectively and easily regenerated by HCl solution after the treatments of both synthetic wastewater and model wastewater. As revealed in FTIR and XPS analyses, the adsorption mechanism was mainly attributed to the electrostatic interaction, hydrogen bonding, cation exchange and chelating effect. With its excellent adsorption capacity for cationic dyes, pH-independent adsorption capability for metal ions, easy separation ability, satisfactory stability and good reusability, [email protected] can become an ideal candidate for wastewater treatment.
Article
In this work, hydroxyapatite modified by xanthan gum (XG) derivativematerial (XMH) was prepared and applied to remove methylene blue (MB) from water. The physicochemical properties of XMH were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-Ray spectroscopy and thermogravimetric analysis. Results showed the operating variables (pH, ionic strength and adsorbent dosage) were related to the MB removal efficiency. Adsorption kinetic and adsorption isotherm were well fitted by the pseudo-second-order model and the Langmuir isotherm model, respectively. It indicated that the adsorption process was a monolayer layer adsorption and chemisorption process. Besides, the result of intra-particle diffusion model demonstrated that the intra-particle diffusion was not the only rate determining step. The maximum adsorption capability on MB was 769 mg/g. Thermodynamic parameters (△G0, △H0, and △S0) showed that the adsorption was a spontaneous and endothermic process. Adsorption mechanisms of MB on XMH might be governed by electrostatic attraction and hydrogen-bonding. Furthermore, XMH could be regenerated well and retained MB removal efficiency of 81% after five cycles of adsorption and desorption. Therefore, XMH is a promising adsorbent for the efficient removal of MB from aqueous solution due to its low cost, good thermal stability and excellent adsorption performance.
Article
Herein, we report a simple two-step method combining adsorption and photoreduction toward the effective removal, separation, and recovery of Cu(II) and Cr(VI) from their hybrid wastewater. A solid solution photocatalyst consisting of TiO2-ZrO2 was utilized to photoreduce Cr(VI) in the absence of a sacrificial agent. The Cr(VI) removal rate reached 95%, whereas Cu(II) was substantially retained in the solution. Conversely, a commercial cation exchange resin, Lewatit TP207, only adsorbed Cu(II) without any notable change in the Cr(VI) concentration. After combining these two selective removal processes, both Cu(II) and Cr(VI) in wastewater can be removed to reach the wastewater discharge standard regardless of the treatment sequence used. However, the most effective sequence was photocatalysis after ion exchange. The residual Cu(II) concentration was 0.06 mg/L and the total Cr concentration was 0.74 mg/L without Cr(VI). The Cu(II)/Cr(VI) separation efficiency was 11,949 with 99.17% Cu(II) and 96.29% Cr(VI) recovered. This work provides a promising referable process for hybrid heavy metal ion wastewater treatment.
Article
This research demonstrates the capability of guar-gum modified with salicylhydrazine to remove Ni²⁺, Co²⁺ and Cr³⁺ from aqueous solution. Structural characterization showed that aldehydes guar gum was grafted with salicylhydrazine with morphology. The as-prepared nanocomposite had a large surface area and hydrophobicity, which ensured its good sorption ability and convenience of separation. The sorption equilibrium data were well fitted to the Langmuir model, and uniquely high adsorption capacities for nickel, chromium and cobalt, which are 1272.4 mg•g⁻¹, 748.86 mg•g⁻¹ and 521.81 mg•g⁻¹, remarkably, were achieved. The thermodynamic parameters for the sorption were also determined, and ΔG and ΔH values indicate exothermic behavior. Adsorption mechanism of capturing cation with GG-SH has been demonstrated through ¹H NMR titration experiments of model molecular and metal ions. The features make this carbohydrate-based material suitable in water purification and separation treatment.
Article
Modified cellulose hydrogels were prepared by blending and cross-linking with acrylamide and acrylic acid. The structure of hydrogels was characterized and analyzed with fourier transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Under the optimized conditions, the maximum absorption capacity in modified cellulose hydrogels of Cu (II), Pb (II) and Cd (II) ions were 157.51, 393.28 and 289.97 mg/g, respectively. In addition, the metal ion adsorption process accorded with pseudo-second-order rate equation and Langmuir adsorption isotherm. Based on the microstructure analysis and adsorption kinetics, the adsorption mechanisms such as physical, chemical, and electrostatic interactions are discussed. The adsorption process was controlled by the ion-exchange mechanism.
Article
Micellar enhanced ultrafiltration is widely used for separation of dyes and other dissolved organics from aqueous solutions. However, generation of reject water that contains highly concentrated dyes, surfactants and electrolytes is a major concern in this process. In this study, micellar enhanced ultrafiltration (MEUF) was integrated with vacuum membrane distillation (VMD) for effective removal of methylene blue dye from aqueous solutions with enhanced water recovery. Activated carbon loaded polyethersulfone (PES) ultrafiltration membrane was used in the process with sodium dodecyl sulphate as an anionic surfactant for micelle formation. The reject of MEUF was further processed via VMD for additional water recovery using a tetraethyl orthosilicate crosslinked polystyrene (PSt) membrane. Effect of feed dye concentration, surfactant concentration and feed pressure on MEUF process performance was evaluated. The effect of feed dye concentration, degree of vacuum and membrane thickness on VMD was also studied. A theoretical model based on modified resistance in series model was used to predict MEUF process flux. Also, an interesting model based on computational fluid dynamics was developed to predict the liquid entry pressure for dye solution which is an important parameter in VMD. The final concentrated dye in VMD retentate could directly be used as an emulsion in paint or textile industry, with simultaneous generation of utility water.
Article
Loose nanofiltration membranes with excellent dye rejection and high inorganic salt transmission are promising for dye/salt separation. Herein, a mussel-inspired organic solvent-free method was chosen to prepare loose nanofiltration membranes with tunable surface structures and properties. A low-cost material, 1,2-dihydroxybenzene (catechol), was used to replace dopamine for the mussel-inspired surface coating strategy. With the assistance of CuSO4/H2O2, a catechol/PEI coating layer was formed on the polyethersulfone (PES) substrate in only 10 min. Through constructing the coating layer based on polyethylenimine (PEI) with different molecular weights, catechol/PEI ratios and solution deposition times, different membranes were obtained. The separation performance of the membrane is tested by a lab-scale crossflow setup under the pressure of 4 bar. Especially, LNM-3 have an ultrahigh water permeability (24.5 LMH bar⁻¹) and an extremely low rejection for both NaCl and Na2SO4 in the concentrations between 1.0 and 50.0 g L⁻¹. Meanwhile, LNM-3 shows superior rejection for different types of dyes, demonstrating their great potential in practical applications. Overall, such an approach enabled by an organic solvent-free process and low-cost chemicals may offer a new strategy for the environmental-friendly and economical manufacturing of multifunctional loose nanofiltration membrane.
Article
PEI-ECH-CMCS microspheres (MPs) were first constructed via elaborately programmed procedures. Fourier transform infrared spectroscopy, conductometric titration, Brunauer−Emmett−Teller, X-ray diffraction, pH at zero point of charge (pH zpc ), scanning electron microscopy, X-ray photoelectron spectroscopy, and swelling results demonstrated that chitosan-based adsorbent had ample −NH 2 and −COOH, specific surface area of 29.040 m ² /g, porous 3D architectures, pH zpc of 4.2, uniform spherical surfaces, narrow size distribution (19–33 μm), and pH-responsive swelling features, advantageous to Cr(VI) and Pb(II) capture. Adsorption parameters were obtained from batch experiments and pH 3 and 5 were chosen for Cr(VI) and Pb(II) capture. Pseudo-second-order kinetic and Liu isotherm models well interpreted adsorption behavior, and thermodynamic, isotherm, and kinetic studies revealed an exothermic, spontaneous, monolayer, and chemical adsorption process. Maximum adsorption capacity for Cr(VI) or Pb(II) was 331.32 or 302.56 mg/g, exceeding CS-based adsorbents reported. Excellent reusability and feasibility were evidenced by adsorption capacity loss < 12.10% and high removal efficiency for Cr(VI) (95.79%) and Pb(II) (91.40%) in synthetic effluents. Finally, potential adsorption mechanisms were proposed.
Article
Sisal fibers were employed as cost-effective adsorbent material to remove methylene blue (MB) and reactive black 5 (RB5) dyes from aqueous solutions. The fibers were characterized and the effects of adsorbent dosage and pH were investigated. Kinetic, equilibrium, and thermodynamics were analyzed. Desorption studies were performed and simulated textile effluents were treated with the fibers. The results revealed that the homogeneous surface diffusion model (HSDM) for cylindrical geometry was able to explain the adsorption kinetics, being the diffusion coefficients (DS) of 3.45 and 1.94 × 10⁻¹⁴ cm² s⁻¹ for MB and RB5, respectively. The BET model was adequate to represent the equilibrium data for MB and RB5. Adsorption capacities reached 553.4 and 310.2 mg g⁻¹ for MB and RB5, respectively. Adsorption was spontaneous and favorable. Chemisorption was involved in the MB adsorption, while, physisorption was dominant for RB5 adsorption. Sisal fibers were efficient to decolorize a simulated effluent, reaching color removal percentage of 85%. It can be concluded that sisal fibers are a promising adsorbent to treat colored effluents, since has low cost, require little processing and possess high adsorption capacity for anionic and cationic dyes.
Article
Fe 3 O 4 nanoparticles functionalized activated carbon (Fe 3 O 4 /AC) as an adsorbent was prepared and used for fast and effectively removing rhodamine B (RhB) and methyl orange (MO) from aqueous solution. Its physical and chemical properties characterized indicate that the adsorbent possesses abundant surface functional groups, sensitive magnetic response and enhanced specific surface area. Batch experiments were carried out to investigate the adsorption capacity and mechanisms. The obtained experimental data fitted well with the general-order kinetic equation and Liu's isotherm model with a maximum adsorption capacity of 182.48 mg g ⁻¹ for RhB and 150.35 mg g ⁻¹ for MO, respectively. The thermodynamic parameter was analyzed further and it showed an exothermic and spontaneous adsorption process. This composite with high adsorption efficiency and rapid magnetic separation can be a promising and recyclable adsorbent for practical wastewater treatment and purification processes.
Article
The chitosan/poly vinyl alcohol membrane was modified by addition of some amine group to the membrane structure utilizing polyethyleneimine (PEI) in order to increase ionic metals adsorbent properties of the membrane. The removal percentage of the modified membranes was compared with the pristine membrane and activated carbon as common adsorbents. The membranes were characterized by FTIR, SEM, swelling degree and porosity measurement. The removal percentage of the membrane containing 0.5 wt.% PEI was more than 60% higher than the activated carbon and more than 40% higher than the pristine membrane. The modified membrane showed excellent adsorption capacity of 112.13, 86.08, and 75.5 mg/g for Cd²⁺, Cu²⁺and Ni²⁺, respectively at 25 °C and pH 6. Adsorption kinetics and equilibrium adsorption isotherm fitted pseudo-second-order kinetic model and Langmuir isotherm model well, respectively. The membrane could be regenerated successfully in Na2EDTA aqueous solution with no significant reduction in its adsorption efficiency.
Article
Magnetic particle is a promising class of materials to absorb harmful contaminants for their easy collecting property with magnetic response. Here, we report a novel kind of polycarboxylic magnetic polydopamine sub-microspheres (Fe3O4@PDA-COOH) facilely synthesized by coating polydopamine (PDA) onto the surface of magnetic nanocrystal clusters (Fe3O4). Then the sub-microspheres were modified with mercaptosuccinic acid (MSA) to have polycarboxylic groups on their surface. Fourier transform infrared spectroscopy (FT-IR) was used to demonstrate the desired chemical structure. The unique morphology and particle size distribution were confirmed by Transmission electron microscopy (TEM). Malachite green (MG) was used as a model to test the adsorption capacity of the magnetic sub-microspheres. Besides, factors such as initial MG concentration, initial solution pH, and contact time were systematically studied for this adsorption process. Results showed that the maximum adsorption capacity of Fe3O4@PDA-COOH could reach up to 331.0162 mg/g (MG/ sub-microspheres), much higher than that of Fe3O4@PDA. The adsorption kinetics and adsorption isotherms could be well described by pseudo-second-order kinetic model and Freundlich isothermal model. Moreover, Fe3O4@PDA-COOH sub-microspheres can retain the high adsorption ability after five using-cycles. Therefore, the synthesized Fe3O4@PDA-COOH can be a high-efficiency adsorbent in the field of wastewater treatment.
Article
Chemically modified fibrous bio-adsorbent extracted from banana trunk was synthesized for potential application in adsorption of heavy metal from wastewater. Glycidyl methacrylate (GMA) polymer graft was first introduced onto the fiber through electron beam irradiation technique. GMA-grafted fiber was subsequently functionalized with imidazole (IMI) group through epoxide ring-opening reaction where amine density of 2.00 mmol/g was achieved. The adsorbent was characterized with Scanning Electron Microscopy (SEM), Fourier Transformed Infrared Spectroscopy (ATR-FTIR), and Thermogravimetric Analyzer (TGA). An extensive kinetic and mechanistic study on the adsorptive removal of metal ions (Cu²⁺, Pb²⁺ and Zn²⁺) by IMI-functionalized GMA-grafted banana fiber is presented. The effects of pH and initial concentration on adsorption capacity were investigated. The adsorption data were correlated with pseudo-first and second order model and the isotherms were analyzed with Langmuir and Freundlich model in order to explain the kinetics and adsorption mechanisms of different metal ions. The thermodynamic studies revealed that the adsorption process for metal ions was exothermic. We also demonstrated that the IMI-GMA-grafted fiber can be regenerated using dilute HNO3 solution, and can be recycled up to 10 times while maintaining satisfactory adsorption performance. Lastly, the chemically modified bio-sorbent was used to treat a local domestic sewage water.
Article
As a natural clay mineral with fascinating nano-structure, halloysite nanotube (HNT) has been widely used as raw materials for the fabrication of HNT-based adsorbents for environmental remediation. However, the current application of the HNT-based adsorbents always suffers from shortcomings such as the use of toxic chemicals during fabrication, a relatively low adsorption capacity, and the limitation in the types of adsorbed pollutants. Therefore, in this study, a multifunctional HNT@carbon with rich carboxyl group (HNT@CRC) was prepared using a facile and cost effective method, and the adsorbent was further used for the removal of pollutants with different features like Pb(II), Cr(VI) and methylene blue (MB). Results show that the increased amount of carboxyl group can enhance the adsorption performance of the modified HNT@CRC, and the HNT@CRC-8 exhibited superior and multifunctional adsorption ability for Pb(II), Cr(VI) and MB with the maximum adsorption capacity of 184.95 mg g⁻¹ at pH 6.0, 140.87 mg g⁻¹ at pH 2.0 and 690.45 mg g⁻¹ at pH 5.5, respectively. By a combination of various techniques (eg.: X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy) and an extensive comparative analysis, the carboxyl group on the surface of HNT@CRC-8 has been identified to play the most critical role in the efficient removal of Pb(II), Cr(VI) and MB. Through this work, a new and cost effective method was proposed for the fabrication of a multifunctional HNT@CRC adsorbent with excellent performance for the efficient removal of a variety of pollutants with different features.
Article
Adsorptive removal of dyes from industrial effluents has attracted intensive interests in the treatment of water pollution. Though the adsorbents have witnessed great development in treating dyeing waste water, super-adsorbent...
Article
The micro-mechanism of heavy metal cations adsorption onto biochar is critical for the renovation of heavy metal contamination. In this work, we prepared three mesoporous cellulose biochar (MCB) adsorbents with different surface area, O and N functionalities content properties through a 300 °C carbonization-KOH activation-700 °C carbonization-HNO3 oxidation process. The Cd(II) adsorption performance of three MCB was compared, the MCB-1h exhibited best Cd(II) adsorption capacity (368.8 mg/g), and even remained 89% after 5 cycles. DFT calculations identified that MCB-1h had comparatively stronger Cd(II) binding ability, and the results were well consistent with the experimental data. The adsorption micro-mechanism was analyzed in the view of classical theory and electron-scale. The classical theory results proposed that the adsorption process was dominated by chemisorption, and electron sharing or exchange between Cd(II) and biochar occurred. Electron-scale mechanism analysis found that the functional groups and aromatic could provide lone pair electrons and π electrons for the Cd(II) adsorption, respectively. The N functionalities such as amino, pyridine and pyrrole groups could raise the adsorption ability of the biochar adsorbent. Overall, our results not only provide new insights into the heavy metal adsorption, but also has significant reference value for the subsequent biochar adsorbent preparation.
Article
A novel hybrid adsorbent, anionic polypeptide poly(γ-glutamic acid)—(γ-PGA) functionalized magnetic Fe3O4-GO-(o-MWCNTs) hybrid nanocomposite was successfully prepared via a simple one-pot reaction. The as-prepared γ-PGA-Fe3O4-GO-(o-MWCNTs) composites were characterized via SEM, TEM, FTIR, XRD, TGA, AFM, zeta potential analysis and magnetic properties analysis. The results indicate that the addition of o-MWCNTs solves the serious aggregation problem of GO and thus makes the GO exposed more grafted sites bonded to large amount of γ-PGA molecule chains. The prepared γ-PGA-Fe3O4-GO-(o-MWCNTs) composites not only have a higher specific surface area to offer abundant surface adsorption sites, but also can be separated more easily from solution systems. Furthermore, the adsorption tests of the γ-PGA-Fe3O4-GO-(o-MWCNTs) were analyzed in Cd(II), Cu(II) and Ni(II) solutions at various pH values, contact time, and initial concentrations of ions. This work indicates that the hybrid adsorbent can be the suitable absorbent materials for various types of heavy metal ions pollution removal and exhibit higher adsorbing capacities in the pH range of 2–10. Its maximum removal capacity calculated by Langmuir model under the optimal conditions toward Cd(II), Cu(II) and Ni(II) is 625.00, 574.71 and 384.62 mg/g, respectively. The adsorption process was well described by the pseudo-second-order kinetics model and the Langmuir isotherm model, respectively. The adsorption mechanism may involve characteristic coordination bonding and electrostatic attraction between γ-PGA-Fe3O4-GO-(o-MWCNTs) and metal ions. Additionally, anionic polypeptide γ-PGA-Fe3O4-GO-(o-MWCNTs) composite can be easily regenerated and recycled at least for three adsorption–desorption recycles. The unique characteristics render the composite highly promising as an advanced adsorbent material for the removal of heavy metal ions.
Article
Activated carbon prepared from custard apple (Annona squamosa) shell by K2CO3 (ACCO3) and H3PO4 (ACPO4) activation were used to study the removal of methyl red (MR) from aqueous medium. The BET surface area, pore volume and pore size of the ACCO3 was 431.3 m²/g, 0.054 cm³/g and 21.63 Ǻ and that of ACPO4 was 1065.0, 0.269 cm³/g and 31.91 Ǻ, suggesting mesoporous nature of the activated carbons. The FT-IR spectra established the occurrence of –COOH and –OH functional groups. SEM images suggested porous and heterogeneous surface. The contact time, adsorbent dose, initial concentration of MR, initial solution pH and temperature were optimized by batch method. The isotherm modeling of the adsorption data over the concentration range (80–130 mg/L) at 303, 313 and 323 K was performed using non-linear regression analysis. The data best described by Langmuir isotherm over the entire concentration range. The negative ΔG° and positive ΔH° values indicated spontaneous and endothermic adsorption process. The kinetic modeling revealed that the experimental data followed the pseudo-first order and pseudo-second order rate equations for ACPO4 and ACCO3, respectively.
Article
The sodium alginate-g-poly(acrylic acid-co-acrylamide)/rice husk ash (NaAlg-g-P(AA-co-AAm)/RHA) superabsorbent nanocomposite was synthesized by the free-radical graft copolymerization of alginate (NaAlg), acrylic acid (AA), acrylamide (AAm), and RHA in aqueous solution. FTIR spectra revealed that the monomers were grafted onto NaAlg chains, and the nanocomposite was formed successfully. Incorporation of RHA into hydrogel matrix formed porous interlinked channels within hydrogel network. Superabsorbent nanocomposite showed greater equilibrium swelling capacity (1070 g/g) compared with neat hydrogel (830 g/g). Moreover, water transport mechanism of all hydrogels was non-Fickian diffusion type. Rheological measurements confirmed effective role of RHA in improving gel strength of superabsorbent nanocomposite. The influence of various factors, such as different loads (0.3, 0.6, 0.9 psi), solution pH, saline solution, and temperature on the swelling behavior of hydrogels was also assessed. Superabsorbent nanocomposite exhibited good pH-dependent swelling reversibility and high water retention capability, making it more efficient water-saving material for agricultural and horticultural applications.
Article
The pursuit of sustainable functional materials requires development of materials based on renewable resources and efficient fabrication methods. Hereby, we fabricated all-polysaccharides multilayer films using cationic guar gum (CGG) and anionic cellulose nanofibrils (i.e. TEMPO-oxidized cellulose nanofibrils, TOCNs) through a layer-by-layer casting method. This technique is based on alternate depositions of oppositely charged water-based CGG and TOCNs onto laminated films. The resultant polyelectrolyte multilayer films were transparent, ductile and strong. More importantly, the self-standing films exhibited excellent gas (water vapor and oxygen) and oil barrier performances. Another outstanding feature of these resultant films was their resistance to various organic solvents including methanol, acetone, N, N-dimethylacetamide (DMAc) and tetrahydrofuran (THF). The proposed film fabrication process is environmentally benign, cost-effective and easy to scale-up. The developed CGG/TOCNs multilayer films can be used as a renewable material for industrial applications such as packaging.