Synthesis and characterization of magnetic β-cyclodextrin–chitosan nanoparticles as nano-adsorbents for removal of methyl blue

Photocatalytic degradation of methyl blue dye with H2O2 sensing

A condensation polymer (urea-formaldehyde resin) passivated ZnO nanoparticles were used as an efficient photocatalyst for methyl blue degradation in the presence of H2O2 involving a Fenton-like reaction. The formation of OH˙ radicals were attributed to the pivotal factor for the degradation process. The method was easy and recyclable. The dose of photocatalyst, initial dye concentration, pH variation, variations of the composition of the photocatalyst, and the effect of scavengers were gauged. The degraded product was highly fluorescent and fluorometric detection of H2O2 was achieved along with a colorimetric recognition pathway. No other dye could be degraded under similar experimental conditions, implying the novel utility of methyl blue for environmental remediation.

Highly fluorescent quinone-capped silver hydrosol for environmental remediation and sensing applications

A metal-enhanced fluorescence was achieved from in situ-generated Ag0 nanoparticles in the proximity of 2-hydroxy benzaldehyde (2HB). Such nanoparticles eliminated methyl blue (MB) dye from water exclusively in the presence of Zn2+ and were proven to be an efficient adsorbent for environmental remediation (maximum uptake capacity 1065 mg·g-1). Ag was zero valent in the absorbent, while Zn2+ was in Zn(OH)2 form. Fe3+ brought back MB in the aqueous medium due to the strong interaction of MB with Fe3+ and the regeneration of blue color helped to design a selective and sensitive Fe3+ sensing platform colorimetrically (linear detection range 10-4-10-6 M; linear detection limit 10-6 M). The silver nanoparticle-induced metal-enhanced fluorescence was quenched efficiently with MB. Pb2+ restored the quenched fluorescence by removing MB from the proximity of the metalized surface of silver, and Pb2+ sensing was performed fluorometrically (linear detection range; 10-5-5 × 10-8 M limit of detection 5 × 10-8 M). Iron and lead were also estimated in a variety of natural water sources, including rainfall, drinking water from taps, and water from the Ganga River via spiking method.

A Comparative Study of Removal of Acid Red 27 by Adsorption on Four Different Chitosan Morphologies

To investigate the relationship between structures and adsorption properties, four different morphologies of chitosan, with hydrogel (CSH), aerogel (CSA), powder (CSP), and electrospinning nanofiber (CSEN) characteristics, were employed as adsorbents for the removal of Acid Red 27. The structures and morphologies of the four chitosan adsorbents were characterized with SEM, XRD, ATR-FTIR, and BET methods. The adsorption behaviors and mechanisms of the four chitosan adsorbents were comparatively studied. All adsorption behaviors exhibited a good fit with the pseudo-second-order kinetic model (R2 > 0.99) and Langmuir isotherm model (R2 > 0.99). Comparing the adsorption rates and the maximum adsorption capacities, the order was CSH > CSA > CSP > CSEN. The maximum adsorption capacities of CSH, CSA, CSP, and CSEN were 2732.2 (4.523), 676.7 (1.119), 534.8 (0.885), and 215.5 (0.357) mg/g (mmol/g) at 20 °C, respectively. The crystallinities of CSH, CSA, CSP, and CSEN were calculated as 0.41%, 6.97%, 8.76%, and 39.77%, respectively. The crystallinity of the four chitosan adsorbents was the main factor impacting the adsorption rates and adsorption capacities, compared with the specific surface area. With the decrease in crystallinity, the adsorption rates and capacities of the four chitosan adsorbents increased gradually under the same experimental conditions. CSH with a low crystallinity and large specific surface area resulted in the highest adsorption rate and capacity.

β-cyclodextrin polymer composites for the removal of pharmaceutical substances, endocrine disruptor chemicals, and dyes from aqueous solution- A review of recent trends

Cyclodextrin (CD) and its derivatives are receiving attention as a new-generation adsorbent for water pollution treatment due to their external hydrophilic and internal hydrophobic properties. Among types of CD, β-Cyclodextrin (βCD) has been a material of choice with a proven track record for a range of utilities in distinct domains, owing to its unique cage-like structural conformations and inclusion complex-forming ability, especially to mitigate emerging contaminants (ECs). This article outlines βCD composites in developing approaches of their melds and composites for purposes such as membranes for removal of the ECs in aqueous setups have been explored with emphasis on recent trends. Electrospinning has bestowed an entirely different viewpoint on polymeric materials, comprising βCD, in the framework of diverse functions across a multitude of niches. Besides, this article especially discusses βCD polymer composite membrane-based removal of contaminants such as pharmaceutical substances, endocrine disruptors chemicals, and dyes. Finally, in this article, the challenges and future directions of βCD-based adsorbents are discussed, which may shed light on pragmatic commercial applications of βCD polymer composite membranes.

A review on chitosan/metal oxide nanocomposites for applications in environmental remediation

A cleaner and safer environment is one of the most important requirements in the future. It has become increasingly urgent and important to fabricate novel environmentally-friendly materials to remove various hazardous pollutants. Compared with traditional materials, chitosan is a more environmentally friendly material due to its abundance, biocompatibility, biodegradability, film-forming ability and hydrophilicity. As an abundant of -NH2 and -OH groups on chitosan molecular chain could chelate with all kinds of metal ions efficiently, chitosan-based materials hold great potential as a versatile supporting matrix for metal oxide nanomaterials (MONMs) (TiO2, ZnO, SnO2, Fe3O4, etc.). Recently, many chitosan/metal oxide nanomaterials (CS/MONMs) have been reported as adsorbents, photocatalysts, heterogeneous Fenton-like agents, and sensors for potential and practical applications in environmental remediation and monitoring. This review analyzed and summarized the recent advances in CS/MONMs composites, which will provide plentiful and meaningful information on the preparation and application of CS/MONMs composites for wastewater treatment and help researchers to better understand the potential of CS/MONMs composites for environmental remediation and monitoring. In addition, the challenges of CS/MONM have been proposed.

Nickel-hydroxide-encapsulated polyacrylamide as a novel adsorptive composite for the capture of methylene blue from wastewater

The wastewater released from different industries is a major environmental issue that has grabbed significant attention lately. Thus, the implementation of suitable routes for the treatment of such water is strongly recommended to reach the level of possible reuse for either industrial or agricultural purposes. In line with such a concept, this research work introduces a new composite structure made via the coating of polyacrylamide by loading nickel hydroxide nanoparticles for use as an absorbent for the purification of wastewater from dye contaminants. High internal phase emulation (HIPE) polymerization was utilized to first prepare particles of polyacrylamide followed by their coating with particles of nickel hydroxide to ultimately obtain the designated adsorbent. The structural features and chemical composition of the synthesized composite were confirmed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and energetic dispersive X-ray (EDX) spectroscopy. Additionally, scanning electron microscopy (SEM) and N2 adsorption-desorption surface area analysis were employed to detect the textural characteristics of the composite. Subsequently, the efficiency of this structure, as an adsorbent for the disposal of methylene blue dye species from a wastewater sample, was studied. During the water purification process, several operating parameters, namely, retention time, solution pH, initial concentration, and absorbent dose, were investigated. The presented Ni-polyacrylamide composite achieved the promising removal of methylene blue dye. An increased adsorption capacity of 14.3 mg g-1 toward methylene blue was achieved by the composite, thanks to the presence of both organic and inorganic functional groups within its structure. Kinetic and isotherm studies for the adsorption of methylene blue species were found to fit pseudo-second-order and Langmuir models. Additionally, thermodynamic measurements indicated that the adsorption process of methylene blue is feasible, spontaneous, involves physisorption, and is endothermic.

Chitosan Nanoparticles as Potential Nano-Sorbent for Removal of Toxic Environmental Pollutants

Adsorption is the most widely used technique for advanced wastewater treatment. The preparation and application of natural renewable and environmentally friendly materials makes this process easier and more profitable. Chitosan is often used as an effective biomaterial in the adsorption world because of its numerous functional applications. Chitosan is one of the most suitable and functionally flexible adsorbents because it contains hydroxyl (-OH) and amine (-NH₂) groups. The adsorption capacity and selectivity of chitosan can be further improved by introducing additional functions into its basic structure. Owing to its unique surface properties and adsorption ability of chitosan, the development and application of chitosan nanomaterials has gained significant attention. Here, recent research on chitosan nanoparticles is critically reviewed by comparing various methods for their synthesis with particular emphasis on the role of experimental conditions, limitations, and applications in water and wastewater treatment. The recovery of pollutants using magnetic nanoparticles is an important treatment process that has contributed to additional development and sustainable growth. The application of such nanoparticles in the recovery metals, which demonstrates a "close loop technology" in the current scenarios, is also presented in this review.

Recent Advancements in Cyclodextrin-Based Adsorbents for the Removal of Hazardous Pollutants from Waters

Water is an essential substance for the survival on Earth of all living organisms. However, population growth has disturbed the natural phenomenon of living, due to industrial growth to meet ever expanding demands, and, hence, an exponential increase in environmental pollution has been reported in the last few decades. Moreover, water pollution has drawn major attention for its adverse effects on human health and the ecosystem. Various techniques have been used to treat wastewater, including biofiltration, activated sludge, membrane filtration, active oxidation process and adsorption. Among the mentioned, the last method is becoming very popular. Moreover, among the sorbents, those based on cyclodextrin have gained worldwide attention due to their excellent properties. This review article overviewed recent contributions related to the synthesis of Cyclodextrin (CD)-based adsorbents to treat wastewater, and their applications, especially for the removal of heavy metals, dyes, and organic pollutants (pharmaceuticals and endocrine disruptor chemicals). Furthermore, new adsorption trends and trials related to CD-based materials are also discussed regarding their regenerative potential. Finally, this review could be an inspiration for new research and could also anticipate future directions and challenges associated with CD-based adsorbents.

β-cyclodextrin and its derivatives: application in wastewater treatment

Water is one of the basic necessities of life and having clean water is extremely important for human health. In recent years, β-cyclodextrin (β-CD)-based polymers and nanosystems have been extensively studied as adsorbents for the purpose of water purification. They present high efficiency and capability to remove inorganic, organic, and heavy metal impurities from wastewater as compared to conventional methods of water purification. β-CDs are cyclic polysaccharides having specific dimension of hydrophobic cavities and hydrophilic functional groups. The hydrophobic cavities form inclusion complexes through host-guest interactions. The hydroxyl groups form sites of hydrogen bonding and electrostatic interaction with pollutants. Additionally, they are also the sites of modification to bring about different derivatisation and polymerization reactions in order to impart desirable properties for efficient adsorption material. This article comprises of various derivatives of β-cyclodextrins: their nanoparticulate systems and their characterization and applications to remove different types of impurities from wastewater. The chemical reactions for their synthesis and mechanism of adsorption are highlighted.

Preparation and applications of chitosan and cellulose composite materials

Chitosan is a natural fiber, chemically cellulose-like biopolymer, which is processed from chitin. Its use as a natural polymer is getting more attention because it is non-toxic, renewable, and biocompatible. However, its poor mechanical and thermal strength, particle size, and surface area restrict its industrial use. Consequently, to improve these properties, cellulose and/or inorganic nanoparticles have been used. This review discusses the recent progress of chitosan and cellulose composite materials, their preparation, and their applications in different industrial sectors. It also discusses the modification of chitosan and cellulose composite materials to allow their use on a large scale. Finally, the recent development of chitosan composite materials for drug delivery, food packaging, protective coatings, and wastewater treatment are discussed. The challenges and perspectives for future research are also considered. This review suggests that chitosan and cellulose nano-composite are promising, low-cost products for environmental remediation involving a simple production process.

Polyethyleneimine grafted starch nanocrystals as a novel biosorbent for efficient removal of methyl blue dye

In this paper, a novel biosorbent of SNCs-PEI was successfully prepared by grafting polyethylenimine (PEI) onto the starch nanocrystals (SNCs) using glutaraldehyde as a crosslinking agent. The optimal preparation conditions of SNCs-PEI were determined by the orthogonal experiments of the three-factor and three-level, and the SNCs-PEI was characterized by Fourier transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDAX), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The zeta potential of SNCs-PEI was +26.3 mV (pH 7), which had a good adsorption performance for the anionic dye methyl blue (MB). The adsorption kinetics and isotherm of MB by SNCs-PEI were studied. At the temperature of 25, 30 and 35 °C, its maximum adsorption capacity was 337.84, 377.36 and 383.14 mg g^-1, respectively. The adsorption of MB by the SNCs-PEI was a spontaneous and endothermic process according to the thermodynamic analysis.

A decade development in the application of chitosan-based materials for dye adsorption: A short review

The presence of dyes in the aquatic environment as a result of anthropogenic activities, especially textile industries, is a critical environmental challenge that hinders the availability of potable water. Different wastewater treatment approaches have been used to remediate dyes in aquatic environments; however, most of these approaches are limited by factors ranging from high cost to the incomplete removal of the dyes and contaminants. Thus, the use of adsorption as a water treatment technology to remove dyes and other contaminants has been widely investigated using different adsorbents. This study evaluated the significance of chitosan as a viable adsorbent for removing dyes from water treatment. We summarised the literature and research results obtained between 2009 and 2020 regarding the adsorption of dyes onto chitosan and modified chitosan-based adsorbents prepared through physical and chemical processing, including crosslinking impregnation, grafting, and membrane preparation. Furthermore, we demonstrated the effects of various chitosan-based materials and modifications; they all improve the properties of chitosan by promoting the adsorption of dyes. Hence, the application of chitosan-based materials with various modifications should be considered a cutting-edge approach for the remediation of dyes and other contaminants in aquatic environments toward the global aim of making potable water globally available.

Immobilization of lipase on β-cyclodextrin grafted and aminopropyl-functionalized chitosan/Fe3O4 magnetic nanocomposites: An innovative approach to fruity flavor esters esterification

The lipase from Bacillus licheniformis NCU CS-5 was immobilized onto β-cyclodextrin (CD) grafted and aminopropyl-functionalized chitosan-coated Fe₃O₄ magnetic nanocomposites (Fe₃O₄-CTS-APTES-GA-β-CD). Fourier transform infrared spectroscopy, thermogravimetry analysis, X-ray diffraction, scanning electron microscopy and transmission electron microscopy showed that not only the functionalized magnetic nanoparticles were synthesized but also the immobilized lipase was successfully produced. The immobilized lipase exhibited higher optimal pH value (10.5) and temperature (60℃) than the free lipase. The pH and thermal stabilities of the immobilized lipase were improved significantly compared to the free lipase. The immobilized lipase remained more than 80% of the relative activity at temperature of 60 ℃ and pH 12.0. The immobilized lipase also remained over 80% of its relative activity after 28 days of storage and 15 cycles of application. The application of the immobilized lipase in esterification of isoamyl acetate and pentyl valerate showed that maximum esterification efficiency was achieved in n-hexane having 68.0% and 89.2% respectively. Therefore, these results indicated that the Fe₃O₄-CTS-APTES-GA-β-CD nanoparticles are novel carriers for immobilizing enzyme, and the immobilized lipase can be used as an innovative green approach to the synthesis of fruity flavor esters in food industry.

Facile preparation of EDTA-functionalized magnetic chitosan for removal of co(II) from aqueous solutions

In this study, an efficient adsorption and reusable magnetic ligand material (Fe₃O₄@Chitosan-EDTA) was synthesized by binding EDTA dianhydride onto magnetic chitosan, and it was employed in removal of Co(II) from aqueous solution. The maximum adsorption capacity of Co(II) onto Fe₃O₄@CS-EDTA was 48.78 mg/g at pH = 5 (303 K), which is much higher than that of Fe₃O₄@Chitosan as well as chitosan. The kinetics of Co(II) on the Fe₃O₄@CS-EDTA was consistent with the pseudo-second-order model. The equilibrium data were better fit with the Langmuir isothermal model than with the Freundlich isothermal model, suggesting that the adsorption mechanism was chemical monolayer homogeneous adsorption. The thermodynamic data showed that the sorption of Co(II) was spontaneous. Furthermore, after four cycles, the adsorption capacity of Co(II) onto the Fe₃O₄@CS-EDTA still retained 84.5% of the capacity of the fresh adsorbent, indicating that Fe₃O₄@CS-EDTA can be considered a promising recyclable adsorbent to remove heavy-metal ions from wastewater.

Highly Efficient Methylene Blue Dye Removal by Nickel Molybdate Nanosorbent

Removing methylene blue (MB) dye from aqueous solutions was examined by the use of nickel molybdate (α-NiMoO₄) as an adsorbent produced by an uncomplicated, rapid, and cost-effective method. Different results were produced by varying different parameters such as the pH, the adsorbent dose, the temperature, the contact time, and the initial dye concentration. Adsorbent dose and pH had a major removal effect on MB. Interestingly, a lower amount of adsorbent dose caused greater MB removal. The amount of removal gained was efficient and reached a 99% level with an initial methylene blue solution concentration of ≤160 ppm at pH 11. The kinetic studies indicated that the pseudo-second-order kinetic model relates very well with that of the obtained experimental results. The thermodynamic studies showed that removing the MB dye was favorable, spontaneous, and endothermic. Impressively, the highest quantity of removal amount of MB dye was 16,863 mg/g, as shown by the Langmuir model. The thermal regeneration tests revealed that the efficiency of removing MB (11,608 mg/g) was retained following three continuous rounds of recycled adsorbents. Adsorption of MB onto α-NiMoO₄ nanoparticles and its regeneration were confirmed by Fourier transform infrared spectroscopy (FTIR) analysis and scanning electron microscopy (SEM) analysis. The results indicated that α-NiMoO₄ nanosorbent is an outstanding and strong candidate that can be used for removing the maximum capacity of MB dye in wastewater.

Complexation of an Azo Dye by Cyclodextrins: A Potential Strategy for Water Purification

The chemistry of the host-guest complex formation has received much attention as a highly efficient approach for use to develop economical adsorbents for water purification. In the present study, the synthesis of three β-cyclodextrin (β-CD) inclusion complexes with the oil orange SS (OOSS) azo dye as a guest molecule and their potential applications in water purification are described. The complexes were synthesized by the coprecipitation method and characterized by Fourier transform infrared (FTIR) spectroscopy, UV-vis spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). FTIR and thermal analyses confirmed the encapsulation of OOSS dye within the hydrophobic cavity of β-CD. The encapsulation of hydrophobic dye inside the β-CD cavity was mainly due to the hydrophobic-hydrophobic interaction. The results showed that the stability of the OOSS dye had been improved after the complexation. The effect of three different compositions of the host-guest complexes was analyzed. The present study demonstrated that the hydrophobic dye could be removed from aqueous solution via inclusion complex formation. Thus, it can play a significant role in removing the highly toxic OOSS dye from the industrial effluent.

Cyclodextrin Polymers and Cyclodextrin-Containing Polysaccharides for Water Remediation

Chemical pollution of water has raised great concerns among citizens, lawmakers, and nearly all manufacturing industries. As the legislation addressing liquid effluents becomes more stringent, water companies are increasingly scrutinized for their environmental performance. In this context, emergent contaminants represent a major challenge, and the remediation of water bodies and wastewater demands alternative sorbent materials. One of the most promising adsorbing materials for micropolluted water environments involves cyclodextrin (CD) polymers and cyclodextrin-containing polysaccharides. Although cyclodextrins are water-soluble and, thus, unusable as adsorbents in aqueous media, they can be feasibly polymerized by using different crosslinkers such as epichlorohydrin, polycarboxylic acids, and glutaraldehyde. Likewise, with those coupling agents or after substituting hydroxyl groups with more reactive moieties, cyclodextrin units can be covalently attached to a pre-existing polysaccharide. In this direction, the functionalization of chitosan, cellulose, carboxymethyl cellulose, and other carbohydrate polymers with CDs is vastly found in the literature. For the system containing CDs to be used for remediation purposes, there are benefits from a synergy that arises from (i) the ability of CD units to interact selectively with a broad spectrum of molecules, forming inclusion complexes and higher-order supramolecular assemblies, (ii) the functional groups of the crosslinker comonomers, (iii) the three-dimensional structure of the crosslinked network, and/or (iv) the intrinsic characteristics of the polysaccharide backbone. In view of the most recent contributions regarding CD-based copolymers and CD-containing polysaccharides, this review discusses their performance as adsorbents in micropolluted water environments, as well as their interaction patterns, addressing the influence of their structural and physicochemical properties and their functionalization.

Oxide modified aluminum for removal of methyl orange and methyl blue in aqueous solution

Oxide modified Al exhibited a higher efficiency in removing organic dyes in aqueous solution than pristine Al.

Chitosan functionalized AgNPs for efficient removal of Imidacloprid pesticide through a pressure-free design

Wide dissemination of pesticides for protecting plants against pests has resulted in high production of un-infected crops but higher environmental pollution. High percentages of pesticides are released to the environment and finally use water as the final destination. The current study is concerning by removal of Imidacloprid pesticide from water using pressure-free passage through polymeric membrane integrated design. Both of chitosan and chitosan functionalized silver nanoparticles (AgNPs @chitosan) membranes were prepared, characterized and applied as adsorbent matrix for Imidacloprid. SEM, TEM and PSA analysis revealed the biosynthesis of AgNPs in the range of 25-50 nm. However, SEM and FTIR analysis revealed the proper formation of chitosan membrane and its proper functionalization with silver nanoparticles. Both of chitosan and AgNPs @chitosan membranes succeeded to remove 40 and 85% of Imidacloprid at slightly acidic pH, respectively. Moreover, the amount of removed Imidacloprid was proportional with the amount of its initial concentration indicating the successful removal of Imidacloprid by AgNPs @chitosan membrane even at higher pesticide concentrations. The obtained results indicate the promising use of AgNPs @chitosan membranes for removal of Imidacloprid pesticide from contaminated water depending on the pressure-free design that lacks external energy support.

Recyclable magnetic chitosan microspheres with good ability of removing cationic dyes from aqueous solutions

Sr_3.8Fe_25.7O_70.4-chitosan magnetic microparticles (Sr_3.8Fe_25.7O_70.4-CMNs) with a core-shell structure were synthesized, characterized and applied for the removal of two model cationic dyes. The results showed that these magnetic microparticles possess fast adsorption rate and high adsorption efficiency for both crystal violet (CV) and basic red 9 (BR9) at a temperature ranging 30 °C to 40 °C and suitable pH range (pH ≥ 7). The maximum removal efficiency for CV and BR9 attained to 94.5% and 97.5% in 30 min, which was significantly faster and higher than that of chitosan (<50% in 60 min) (P<0.01). And its maximum adsorption capacity for CV and BR9 reached 29.46 mg/g and 32.16 mg/g, respectively. The adsorption process of Sr_3.8Fe_25.7O_70.4-CMNs follows the Langmuir isotherm with a high correlation coefficient (R² > 0.97) and the pseudo-second-order model. Additionally, the synthesized Sr_3.8Fe_25.7O_70.4-CMNs were easy to regeneration and reuse, and the removal rate remained above 90% after 5 recycle times. This study would provide a new more environmental friendly material and method for the treatment of wastewater containing toxic dyes.

Iron Molybdate Fe2(MoO4)3 Nanoparticles: Efficient Sorbent for Methylene Blue Dye Removal from Aqueous Solutions

The present study investigated iron molybdate (Fe₂(MoO₄)₃), synthesized via a simple method, as a nanosorbent for methylene blue (MB) dye removal from aqueous solutions. Investigations of the effects of several parameters like contact time, adsorbent dose, initial dye concentration, temperature and pH were carried out. The results showed that MB removal was affected, significantly, by adsorbent dose and pH. Interestingly, lower values of adsorbent dose resulted in the removal of higher amounts of MB. At the optimum pH, the removal efficiency of 99% was gained with an initial MB concentration of ≤60 ppm. The kinetic study specified an excellent correlation of the experimental results with the pseudo-second-order kinetics model. Thermodynamic studies proved a spontaneous, favorable and endothermic removal. The maximum amount of removal capacity of MB dye was 6173 mg/g, which was determined from the Langmuir model. The removal efficiency was shown to be retained after three cycles of reuse, as proven by thermal regeneration tests. The presence and adsorption of the dye onto the Fe₂(MoO₄)₃ nanoparticle surface, as well as the regeneration of the latter, was ascertained by scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). These findings are indicative that the investigated nanosorbent is an excellent candidate for the removal of MB in wastewater.

Cytotoxic aquatic pollutants and their removal by nanocomposite-based sorbents

Water is an extremely essential compound for human life and, hence, accessing drinking water is very important all over the world. Nowadays, due to the urbanization and industrialization, several noxious pollutants are discharged into water. Water pollution by various cytotoxic contaminants, e.g. heavy metal ions, drugs, pesticides, dyes, residues a drastic public health issue for human beings; hence, this topic has been receiving much attention for the specific approaches and technologies to remove hazardous contaminants from water and wastewater. In the current review, the cytotoxicity of different sorts of aquatic pollutants for mammalian is presented. In addition, we will overview the recent advances in various nanocomposite-based adsorbents and different approaches of pollutants removal from water/wastewater with several examples to provide a backdrop for future research.

The effective removal of phenol from aqueous solution via adsorption on CS/β-CD/CTA multicomponent adsorbent and its application for COD degradation of drilling wastewater

The 3-chloro-2 hydroxypropyltrimethyl ammonium chloride was successfully introduced into the β-cyclodextrin-modified chitosan to create the multicomponent adsorbent O-HTACC-g-CD. The structure of sorbent was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. The adsorption capacity of O-HTACC-g-CD toward phenol was investigated as a function of pH, temperature, contact time as well as adsorbent dosage. The Box-Behnken response surface methodology was employed to optimize the effects of experimental parameters including adsorbent dose, pH, and time on the adsorption of phenol at 298.15 K. The obtained optimal values for adsorbent dose, pH, and time were 0.06 g, 6, and 200 min, respectively. The obtained experimental data follows the pseudo-second-order kinetic and Langmuir model. The thermodynamic parameters such as free energy change, enthalpy change, and entropy change were calculated, revealing that adsorption of phenol on O-HTACC-g-CD is a spontaneous and exothermic process. The prepared O-HTACC-g-CD displayed high adsorption capacity (39.98 mg g-1) and excellent removal rate (96%) for phenol from the aqueous solution at 288.15 K. The gained removal rates of chemical oxygen demand (CODCr) were in the range of 60.6-61.2%. Considerable results of sorption could be attributed to the multicomponent structure of the adsorbent with more active sites including the cavities, amino, and carboxyl functional groups which provided better sites for the phenolic pollutant to adsorb on the adsorbent via Van der Waals force, hydrogen bond, and the inclusion effect. Therefore, the results obtained strongly suggest that O-HTACC-g-CD could be an effective adsorbent for the removal of phenol and CODcr from drilling wastewater.

Sawdust-Based Cellulose Nanocrystals Incorporated with ZnO Nanoparticles as Efficient Adsorption Media in the Removal of Methylene Blue Dye

The continuous increase in the wastes generated from forestry, timber, and paper industries has engendered the need for their transformation into economically viable materials for the benefit of mankind. This study reports the preparation and application of sawdust-derived cellulose nanocrystals (CNC) incorporated with zinc oxide as a novel adsorbent for the removal of methylene blue (MB) from water. The CNC/ZnO nanocomposite was characterized using Fourier transform infrared, X-ray diffraction (XRD), and scanning electron microscopy. The amount of MB adsorbed was determined by a UV-vis spectrophotometer. The microscopic analysis revealed that the nanocomposite had a narrow particle size range and exhibited both spherical and rod-like morphologies. The XRD analysis of the nanocomposite showed characteristic high-intensity peaks in the range of 30-75° attributed to the presence of ZnO nanoparticles, which were responsible for the enhancement of the crystallinity of the nanocomposite. The results revealed a relationship between the MB removal efficiency and changes in solution pH, nanocomposite dosage, initial concentration, temperature, and reaction time. The adsorption equilibrium isotherm, measured in the temperature range of 25-45 °C and using a concentration of 20-100 mg/L, showed that the MB sorption followed the Langmuir isotherm with a maximum adsorption capacity of 64.93 mg/g. A pseudo-second-order kinetic model gave the best fit to the experimental data. Based on adsorption performance, the CNC/ZnO nanocomposite offers prospects for further research and application in amelioration of dye-containing effluent.

Cyclodextrin nanoparticle bound oral camptothecin for colorectal cancer: Formulation development and optimization

Chemotherapeutic drugs for colorectal cancer(CRC) which is currently the third most lethal cancer globally, are administered intravenously (iv) due to their low oral bioavailability resulting from their physicochemical properties. Non-selective biodistribution and difficulties of parenteral administration reduce treatment efficacy. The aim of this work is to develop cyclodextrin (CD) based cationic nanoparticles (NPs) for CRC treatment with model drug camptothecin (CPT) that can be administered orally, protecting CPT through gastrointestinal tract (GIT), accumulating at mucus layer and providing an effective local treatment for the tumor area. NPs using two different amphiphilic CDs were prepared and coated with polyethylenimine (PEI) or chitosan (CS) to obtain positively charged surface for all formulations. Pre-formulation studies resulted in optimal formulation, CPT loaded Poly-β-CD-C6 NPs, with 135 nm diameter and zeta potential of + 40 mV. In vitro release study was designed to represent gastrointestinal pH and transit time revealing 52% of encapsulated CPT successfully delivered all the way to simulated colon. CPT bound to Poly-β-CD-C6 NPs exhibited higher cytotoxicity on HT-29 cells compared to equivalent CPT in solution. Caco-2 cell permeability studies showed 276% increase in CPT permeability and significantly higher mucosal penetration in cationic CD nanoparticle form.

Adsorption of indigo carmine on functional chitosan and β-cyclodextrin/chitosan beads: Equilibrium, kinetics and mechanism studies

The present study was designed to produce novel cross-linked Chitosan and Chitosan/β-Cyclodextrin beads and study the adsorption of Indigo Carmine. Both adsorbents were characterized by SEM and FTIR techniques. Batch experiments were conducted in order to evaluate the effect of initial adsorbent's concentration, dye's initial concentration, initial pH and temperature. In all cases Chitosan/β-Cyclodextrin crosslinked beads exhibited higher removal efficiency of Indigo Carmine. Higher removal rates of Indigo Carmine were observed at low values of dye's initial concentration, pH and temperature, and high concentrations of adsorbent. The equilibrium adsorption data were a good fit for both Langmuir and Freundlich models and maximum adsorption capacity was 500.0 and 1000.0 mg_IC/g_adsorbent for Chitosan and Chitosan/β-Cyclodextrin crosslinked beads, respectively. Adsorption of Indigo Carmine was found to follow the pseudo-second order. The negative values of ΔG^o, ΔH^o and ΔS^o indicate that the adsorption process is exothermic, spontaneous and favorable at low temperatures.

Novel cyclodextrin-based adsorbents for removing pollutants from wastewater: A critical review

Over the past few decades, cyclodextrin-based adsorbents have drawn worldwide attention as new-generation adsorbents for wastewater treatment due to its extraordinary physicochemical properties. This review outlined the recent development in the synthesis of cyclodextrin-based adsorbents as well as highlighted their applications in the removal of heavy metals, dyes, endocrine disrupting chemicals (EDCs), and mixed pollutants from water. The cross-linked and immobilized cyclodextrin-based adsorbents exhibited excellent adsorption performances. The removal of dyes and heavy metals were effectively controlled by ion exchanging, mainly depending upon the pH; while the adsorptions of EDCs always occurred in cyclodextrin cavities and pH-independent. An easier separation process between aqueous and adsorbents could be achieved compared to native cyclodextrin, which promoted the application of cyclodextrin-based adsorbents in practical industry. This review could provide an inspiration for the advanced study in the development of cyclodextrin-based adsorbents for high efficiency wastewater treatment.

Cyclodextrin functionalized 3D-graphene for the removal of Cr(VI) with the easy and rapid separation strategy

As a useful heavy metal ion, chromium has seen its applications in various fields. While it is also a toxic contaminant in water and may cause serious threats to the environment and human health. To develop a novel material with good adsorption capacity and easy solid-liquid separation strategy was necessary and significant. In this paper, the β-cyclodextrin (β-CD) functionalized three-dimensional structured graphene foam (CDGF) was successfully synthesized with the facile and one-step hydrothermal method. The SEM, BET, XRD, FT-IR and XPS analysis were carried out and the results confirmed the successfully grafting of β-CD onto GF. The batch adsorption of Cr(VI) was also taken out and the CDGF possessed good selectivity compared with other metal ions at pH = 3. The adsorption capacity reduced gradually as the initial pH of the Cr(VI) solution grew higher, which was because the anionic species of Cr(VI) were partial to the positively charged surface of CDGF. The easy separation strategy of the CDGF was also demonstrated and the CDGF could be taken out easily with a tweezer after the adsorption of Cr(VI), which significantly simplified the separation procedure and reduced time. By comparing the FT-IR and XPD analysis results, the adsorption mechanism was explored and the hydroxyl groups on CDGF played the main role in the adsorption process. This work brings a novel material for the adsorption of Cr(VI) from water and provides an innovative direction for the easy and fast solid-liquid separation strategy in the adsorption and other application fields.

Characterization and adsorption performance of graphene oxide - montmorillonite nanocomposite for the simultaneous removal of Pb2+ and p-nitrophenol

Montmorillonite-graphene oxide composite (MGC) with their own advantages was successfully fabricated for the simultaneous treatment of the combined pollution wastewater containing heavy metal ions and organic pollutants. The features of MGC were analyzed by X-ray diffraction, transmission electron microscopy, atomic force microscopy and Fourier transform infrared spectroscopy. Subsequently, a series of batch experiments were carried out to investigate the adsorption performance of Pb²⁺ and p-nitrophenol (PNP) onto MGC in single and binary system. The results indicated that MGC exhibited a gossamer layer with spots and a larger interlayer spacing. In single adsorption experiment, the removal of PNP by MGC reached 96.82%, while Pb²⁺ removal reached 98.94%, which was maintained at the same level as montmorillonite. In binary acidic system of Pb²⁺ and PNP, the removal of Pb²⁺ reached 98.23%, while PNP removal dropped to 51.06% due to their competitive adsorption. The thermodynamic study indicated that the chemisorption was predominant in the adsorption of Pb²⁺ onto MGC, while physisorption was for PNP. It was exactly that the strong competitiveness of Pb²⁺ brought the remarkable reduction in PNP adsorption capacity in the simultaneous adsorption.

Recent advances for dyes removal using novel adsorbents: A review

Dyeing wastewaters are toxic and carcinogenic to both aquatic life and human beings. Adsorption technology, as a facile and effective method, has been extensively used for removing dyes from aqueous solutions for decades. Numerous researchers have attempted to seek or design alternative materials for dye adsorption. However, using various novel adsorbents to remove dyes has not been extensively reviewed before. In this review, the key advancement on the preparation and modification of novel adsorbents and their adsorption capacities for dyes removal under various conditions have been highlighted and discussed. Specific adsorption mechanisms and functionalization methods, particularly for increasing adsorption capacities are discussed for each adsorbent. This review article mainly includes (1) the categorization, side effects and removal technologies of dyes; (2) the characteristics, advantages and limitations of each sort of adsorbents; (3) the functionalization and modification methods and controlling mechanisms; and (4) discussion on the problems and future perspectives about adsorption technology from adsorbents aspects and practical application aspects.

Insights of CMNPs in water pollution control

The various toxic contaminants such as dyes, heavy metals, pesticides, rare-earth elements, and hazardous chemicals are the major threats to all the flora and fauna. Owing to the harmful ill effects caused by the toxic contaminants, it is necessary to eliminate these compounds from the authors' ecosystem. The chitosan magnetic nanomaterials (CMNPs) are one of the superior materials used in the wastewater treatment through various conventional technologies. The chitosan is a natural source obtained from the crustacean shells of crabs, prawns etc. The magnetic nanomaterial prepared by the reinforcement of chitosan is highly effective in the removal of heavy metals, dyes, organic matter, and harmful chemicals. It is used in various technologies such as adsorption, flocculation, immobilisation, photocatalytic technology, and bioremediation. This possesses unique surface and magnetic characteristics, Moreover, it is simple, economically feasible, and eco-friendly material used efficiently in wastewater treatment. This review paper depicts the overview of CMNP in the industrial effluent treatment.

Novel porous magnetic nanospheres functionalized by β-cyclodextrin polymer and its application in organic pollutants from aqueous solution

Magnetic β-cyclodextrin (β-CD) porous polymer nanospheres (P-MCD) was fabricated by one-pot solvent thermal method using β-CD immobilized Fe₃O₄ magnetic nanoparticles with tetrafluoroterephthalonitrile as the monomer. Compared with the β-CD polymerization method reported in the literature,_ENREF_1 the synthetic route is effective and simple, thereby overcoming the harsh conditions that require nitrogen protection and always maintain anhydrous and oxygen-free. Moreover, the immobilization of β-CD on magnetic nanoparticles is combined with the cross-linking polymerization of the cross-linker, leading to a good synergistic effect on the removal of contaminants. Meanwhile, the dispersibility of the magnetic carrier enhances the dispersion of the β-CD porous polymer in the aqueous phase, and improves the inclusion adsorption performance and the adsorption process. P-MCD exhibited superior adsorption capacity and fast kinetics to MB. The maximum adsorption capacity of MB for P-MCD was 305.8 mg g ^-1, which is more than β-CD modified Fe₃O₄ magnetic nanoparticles (Fe₃O₄@β-CD). Moreover, the material had a short equilibrium time (5 min) for MB, high recovery and good recyclability (the adsorption efficiency was still above 86% after five repeated uses).

A novel colorimetric immunosensor based on platinum colloid nanoparticles immobilized on PowerVision as signal probes and Fe3 O4 @β-cyclodextrin as capture probes for ractopamine detection in pork

BACKGROUND

A novel colorimetric immunosensor was developed for the simple, sensitive and selective detection of ractopamine (RAC) based on using β-cyclodextrin-modified Fe₃ O₄ particles (Fe₃ O₄ @β-CD) as capture probes and complex platinum colloid nanoparticles (PtNPs-PV) composed of platinum colloid nanoparticles (PtNPs) and polymerase chelate PowerVision (PV) as signal probes.

RESULTS

PtNPs-PV double catalyzed the chromogenic substrate 3,3'-diaminobenzidine (DAB), which induced changes in the color of DAB and chromogenic absorbance. Incubation temperature, pH and incubation time were systematically optimized and, under optimum conditions, the measured absorbance values showed a linear relationship with the RAC concentrations in the range 0.03-8.1 ng mL^-1 . The detection limit was 0.01 ng mL^-1 . The sensor exhibited high sensitivity and specificity, as demonstrated by testing structurally similar organic compounds such as salbutamol, clenbuterol and dopamine. The practicality of the developed colorimetric immunosensor was supported by the successful detection of RAC in pork samples with recovery ranging from 94.00% to 106.00%.

CONCLUSION

We designed a novel sandwich-type noncompetitive colorimetric immunoassay for the detection of trace levels of RAC in pork. The proposed method can also be used for the detection of toxins in food products via PtNPs-PV amplification. © 2018 Society of Chemical Industry.

Preparation of graphene oxide-montmorillonite nanocomposite and its application in multiple-pollutants removal from aqueous solutions

It is of interest to develop a novel fabrication method of a mineral adsorbent for wastewater treatment to remove the combination of heavy metal ions and refractory organic contaminants. The crosslinking agent stearyl trimethyl ammonium chloride was added into a suspension of montmorillonite and graphene oxide to implement their recombination to fabricated graphene oxide-montmorillonite nanocomposite (GMN). The fabricated nanocomposite was characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller analysis and zeta potential. Results indicated that GMN exhibited a honeycomb texture, providing the chemical reaction site for the simultaneous adsorption of Pb²⁺ and p-nitrophenol (PNP). Factors including pH value, contact time, contact temperature and GMN dosage in the adsorption process were crucial for both Pb²⁺ adsorption and PNP adsorption. The optimum adsorption capacities of Pb²⁺ and PNP onto GMN were 19.39 mg·g^-1 and 14.90 mg·g^-1 under the condition of pH = 6, contact temperature 55 °C, contact time 60 min and GMN dosage 0.10 g, respectively. Data from experimental studies on simultaneous adsorption was well described by the pseudo-second-order model. The implementation of this work shows that GMN is a promising material for application in the simultaneous removal of heavy metal ions and refractory organic contaminants.