Ethanolamine- and amine-functionalized porous cyclodextrin polymers for efficient removal of anionic dyes from water

Efficacy of exopolysaccharide in dye-laden wastewater treatment: A comprehensive review

The discharge of dye-laden wastewater into the water streams causes severe water and soil pollution, which poses a global threat to aquatic ecosystems and humans. A diverse array of microorganisms such as bacteria, fungi, and algae produce exopolysaccharides (EPS) of different compositions and exhibit great bioflocculation potency to sustainably eradicate dyes from water bodies. Nanomodified chemical composites of EPS enable their recyclability during dye-laden wastewater treatment. Nevertheless, the selection of potent EPS-producing strains and physiological parameters of microbial growth and the remediation process could influence the removal efficiency of EPS. This review will intrinsically discuss the fundamental importance of EPS from diverse microbial origins and their nanomodified chemical composites, the mechanisms in EPS-mediated bioremediation of dyes, and the parametric influences on EPS-mediated dye removal through sorption/bioflocculation. This review will pave the way for designing and adopting futuristic green and sustainable EPS-based bioremediation strategies for dye-laden wastewater in situ and ex situ.

Preparation and application of the thermo-/pH-/ ion-sensitive semi-IPN hydrogel based on chitosan

Chitosan based hydrogels with multiple stimulus responses have broad application prospects in many fields. Considering the advantages of semi interpenetrating network (IPN) technology and the special temperature and ion responsiveness of polymers containing zwitterionic groups, a semi-IPN hydrogel was prepared through in situ free radical polymerization of N,N-dimethyl acrylamide and [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) ammonium hydroxide with polyethylene glycol dimethacrylate as a crosslinker and carboxymethyl chitosan as filler. The gel mass fraction and swelling ratio were measured, and the preparation conditions were optimized. The result indicated that the hydrogel possessed a unique thermo-/pH-/ ion-sensitive behavior. The swelling ratio increased with the increase of temperature and ion concentration, and showed a decreasing trend with the increase in pH. In addition, the hydrogel was stable when the stimuli changed. Adsorption behavior of the hydrogel to Eosin Y (EY) was systematically investigated. The adsorption process can be described well by the pseudo-second-order kinetic model and Langmuir isotherm model, indicating that it was a chemical adsorption. The experiments indicated that the hydrogel exhibited good antifouling and reusability features. Therefore, the semi-IPN hydrogel with antifouling properties and thermo-/pH-/ion-sensitivity can be easily manufactured is expected to find applications in water treatment fields.

Upgraded β-cyclodextrin-based broad-spectrum adsorbents with enhanced antibacterial property for high-efficient dyeing wastewater remediation

The dyeing wastewater contains amounts of refractory organic compounds, and severely endangers the ecosystem and human health. To alleviate this problem, in this study, the low-cost broad-spectrum nano-adsorbent (denoted as CD/CA-g-CS) with strong antibacterial activity has been synthesized by chemical binding of β-cyclodextrin (β-CD) with chitosan (CS) and citric acid (CA) for high-efficient dyes scavenger. Taking advantage of the extraordinary water insolubility, porous nature and abundant surface groups, the synthesized CD/CA-g-CS outperforms the previously reported adsorbents in terms of adsorption performance. The CD/CA-g-CS exhibits ultrahigh adsorption capacities of 801.66, 770.50 and 946.66 mg/g, respectively mg/g for the cationic dyes of malachite green (MG), basic red (BR) and methylene blue (MB), respectively, while 389.64, 619.60 and 429.22 mg/g for the anionic dyes of acid blue (AB), acid red (AR) and acid yellow (AY), respectively. The chemical monolayer absorption is further demonstrated by the analysis based on the pseudo-second-order adsorption kinetics and Langmuir isotherm models. The regenerable CD/CA-g-CS not only performs well in one-step removal of the mixed dyes in the simulated sewage, but also exhibits superior performance in purifying real industrial wastewater. Moreover, CD/CA-g-CS endowed with antibacterial activity leads to an inhibition rate of over 99.99 % for E. coli. The newly developed CD/CA-g-CS adsorbents are highly promising for high-efficient dyeing wastewater remediation.

Novel fabricated low-cost hybrid polyacrylonitrile/polyvinylpyrrolidone coated polyurethane foam (PAN/PVP@PUF) membrane for the decolorization of cationic and anionic dyes

Dyes are recalcitrait organic pollutants threatening the aquatic environment and human health. In the present study, a novel low-cost hybrid membrane was fabricated by coating polyurethane foam (PUF) with polyacrylonitrile/polyvinylpyrrolidone (PAN/PVP) via phase inversion technique from casting solutions consisting of PAN and PVP with Dimethyl formamide (DMF) and applied for removal of cationic (Methylene Blue (MB)) and anionic (Methyl Orange (MO)) dyes from aqueous solutions. The as-prepared membrane was first characterized by Scan Electron Microscope (SEM), Fourier Transform Infrared (FTIR), Energy Dispersive Spectrometry (EDS), etc. Then, batch experiments were conducted to optimize the adsorption conditions, including contact time, adsorbent dose, dyes concentration, and pH. The dye removal results fitted with pseudo first and second-order kinetics; Langmuir, Freundlich, and Temkin isotherms' models. The maximum dye decolorization was approximately 97% and 95% within 60 and 120 min using 0.5 and 1 g of the fabricated composite for MB and MO, respectively. The kinetic studies showed rapid sorption dynamics following a second-order kinetic model. In addition, dye adsorption equilibrium data fitted well to the Freundlich isotherm with monolayer maximum adsorption capacity of 6.356 and 3.321 mg/g for MO and MB dye, respectively. Thus, the novel hybrid membrane is promising as a cheap and efficient adsorbent for the removal of both cationic and anionic dyes from wastewater. The current study demonstrated a new avenue to achieve efficient management of dyes in aquatic environments.

Adsorption of cationic dyes onto carrageenan and itaconic acid-based superabsorbent hydrogel: Synthesis, characterization and isotherm analysis

Polysaccharide-based hydrogels offer a great overlook for environmental applications and help in the elimination of various noxious pollutants from the water system. Novel carrageenan and itaconic acid-based superadsorbent hydrogel having appreciable swelling properties and adsorption capacity towards Methylene blue (MB), Crystal violet (CV), and Methyl Red (MR) was synthesized by suspension polymerization technique. The swelling study showed the dependency upon the temperature in which the swelling rate increased with increasing temperature with a maximum swelling rate of 417% at 318 K. For ascertaining the maximum adsorption capacity, various influential parameters such as contact time, adsorbent dose, dye concentration, and temperature were systematically studied. Maximum adsorption capacity as calculated from the Langmuir isotherm was 2439.02, 1111.11, and 666.68 mg/g for MB, CV, and MR, respectively. Thermodynamic studies revealed the spontaneous nature of the undertaken dye adsorption experiment. Overall, the present study reveals that the synthesized superadsorbent hydrogel can be used as an efficient adsorbent for the removal of dyes from an aqueous solution.

The preparation of novel poly(ether-amide)s based on spiro[fluorene-9,9′-xanthene] and a polyamide/polymer-coated ZnO nanocomposite: thermal, optical, biological, and methylene blue dye adsorption attributes

Novel thermostable, photoactive, and solvable polyamides containing fluorene and xanthene groups were synthesized, as was a ZnO-based composite. These compounds were used as antibacterial and anticancer agents and as absorbents to remove MB dye.

Modification of cyclodextrin and use in environmental applications

Water pollution, which has become a global problem in parallel with environmental pollution, is a problem that needs to be solved urgently, considering the gradual depletion of water resources. The inadequacy of the water treatment methods and the materials used somehow directed the researchers to look for dual character structures such as biocompatible and biodegradable β-cyclodextrin (β-CD). β-CD, which is normally insoluble in water, is used in demanding wastewater applications by being modified with the help of different agents to be water soluble or transformed into polymeric adsorbents as a result of co-polymerization via cross-linkers. In this way, in addition to the host-guest interactions offered by β-CD, secondary forces arising from these interactions provide advantages in terms of regeneration and reusability. However, the adsorption efficiency and synthesis steps need to be improved. Based on the current studies presented in this review, in which cross-linkers and modification methods are also mentioned, suggestions for novel synthesis methods of new-generation β-CD-based materials, criticisms, and recent methods of removal of micropollutants such as heavy metals, industrial dyes, harmful biomolecules, and pharmaceutics wastes are mentioned.

Emerging novel polymeric adsorbents for removing dyes from wastewater: A comprehensive review and comparison with other adsorbents

Dye molecules are one of the most hazardous compounds for human and animal health and the excess intake of these materials can create toxic impacts. Several studies show the practicality of the adsorption process for dye uptake from wastewaters. In recent years, various adsorbents were used to be efficient in this process. Among all, polymeric adsorbents demonstrate great applicability in different environmental conditions and attract many researchers to work on them, although there is not enough reliable and precise information regarding these adsorbents. This study aims to investigate some influential parameters such as their type, physical properties, experimental conditions, their capacity, and further modeling along with a comparison with non-polymeric adsorbents. The influence of the main factors of adsorption capacity was studied and the dominant mechanism is explained extensively.