Super-Adsorbent Hydrogels for Removal of Methylene Blue from Aqueous Solution: Dye Adsorption Isotherms, Kinetics, and Thermodynamic Properties
19 Nov 2021-Macromolecules (Multidisciplinary Digital Publishing Institute)-Vol. 1, Iss: 4, pp 256-275
TL;DR: In this paper, a super-adsorbent hydrogel based on sodium styrenesulfonate (NaSS) monomer was designed for removal of dyes like methylene blue (MB).
Abstract: Removal of dyes through adsorption from wastewater has gained substantial interest in recent years, especially in development of hydrogel based adsorbents, owing to their easy use and economical nature. The aim of the present study was to design a super-adsorbent hydrogel based on sodium styrenesulfonate (NaSS) monomer for removal of dyes like methylene blue (MB). NaSS displays both an aromatic ring and strongly ionic group in its monomer structure that can enhance adsorption capacity. Poly(sodium styrenesulfonate-co-dimethylacrylamide) hydrogels were prepared by solution free radical polymerization using gelatin methacryloyl (GelMA) as crosslinker, creating a highly porous, three-dimensionally crosslinked polymer network contributing to higher swelling ratios of up to 27,500%. These super-adsorbent hydrogels exhibited high adsorption capacity of 1270 mg/g for MB adsorption with above 98% removal efficiency. This is the first report for such a high adsorption capacity for dye absorbance for NaSS-based hydrogels. Additionally, the adsorption kinetics using a pseudo-first-order and the Freundlich adsorption isotherm models for multilayer, heterogeneous adsorption processes has been reported. The adsorbents’ reusability was confirmed through 4 repeated cycles of desorption-adsorption. The results discussed herein illustrate that NaSS based chemistries can be used as an efficient option for removal of organic dyes from contaminated wastewater.
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TL;DR: In this article , the authors give a thorough discussion on the derivation of thermodynamic equilibrium constant of solid-liquid adsorption process, and a reasonable explanation on the inconsistency of (direct and indirect) application of distribution coefficient (KD) or Freundlich constant (KF) for calculating the thermodynamic parameters.
Abstract: Adsorption processes often include three important components: kinetics, isotherm, and thermodynamics. In the study of solid–liquid adsorption, “standard” thermodynamic equilibrium constant
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; dimensionless) plays an essential role in accurately calculating three thermodynamic parameters: the standard Gibbs energy change (∆G°; kJ/mol), the standard change in enthalpy (∆H°; kJ/mol), and the standard change in entropy [∆S°; J/(mol × K)] of an adsorption process. Misconception of the derivation of the
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constant that can cause calculative errors in values (magnitude and sign) of the thermodynamic parameters has been intensively reflected through certain kinds of papers (i.e., letters to editor, discussions, short communications, and correspondence like comment/rebuttal). The distribution coefficient (KD) and Freundlich constant (KF) have been intensively applied for calculating the thermodynamic parameters. However, a critical question is whether KD or KF is equal to
K
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. This paper gives (1) thorough discussion on the derivation of thermodynamic equilibrium constant of solid–liquid adsorption process, (2) reasonable explanation on the inconsistency of (direct and indirect) application of KD or KF for calculating the thermodynamic parameters based on the derivation of
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, and (3) helpful suggestions for improving the quality of papers published in this field.
22 citations
TL;DR: In this article , a semi-interpenetrating network (semi-IPN) nanocomposite hydrogels were obtained by free radical copolymerization of acrylamide (AAm) and itaconic acid (IA) in the presence of chitosan (CS) as an environmentally friendly bio-adsorbent.
13 citations
TL;DR: In this paper , the adsorption mechanism of methylene blue (MB) onto olive waste (residue) treated with KOH (OR-KOH) and onto an OR-Koh and PEG-silica gel composite at various temperatures were investigated using a combination of experimental analysis and Monte Carlo ab-initio simulations.
Abstract: The adsorption mechanisms of methylene blue (MB) onto olive waste (residue) treated with KOH (OR-KOH) and onto an OR-KOH and PEG–silica gel composite (OR-KOH/PEG-SG) at various temperatures were investigated using a combination of experimental analysis and Monte Carlo ab-initio simulations. The effects of adsorption process variables such as pH, temperature, and starting adsorbate concentration were investigated. The experimental data were fitted to Langmuir and Freundlich models. The maximum adsorption capacities of MB onto OR-KOH and OR-KOH/PEG-SG adsorbents reached values of 504.9 mg/g and 161.44 mg/g, respectively. The experimental FT-IR spectra indicated that electrostatic attraction and hydrogen bond formation were critical for MB adsorption onto the adsorbents generated from olive waste. The energetic analyses performed using Monte Carlo atomistic simulations explained the experimental results of a differential affinity for the investigated adsorbents and confirmed the nature of the interactions between methylene blue and the adsorbents to be van der Waals electrostatic forces.
12 citations
TL;DR: In this article , cassava rhizome (CR) derived activated carbons (AC) and magnetic AC were fabricated by one-pot hydrothermal carbonization in the presence of ZnCl2 and ZnCL2/FeCl3 respectively, followed by pyrolysis at 800 °C.
Abstract: The development of sustainable adsorbent materials for removing pollutants from water is of great interest for environmental remediation and human safety. This work presents the beneficial use of cassava rhizome (CR) to produce economical and efficient carbonaceous adsorbents for dye removal. CR derived activated carbons (AC) and magnetic AC were fabricated by one-pot hydrothermal carbonization in the presence of ZnCl2 and ZnCl2/FeCl3 respectively, followed by pyrolysis at 800 °C. Porosity tuning and degree of magnetization of as-prepared carbons were achieved by varying the amount of ZnCl2 and FeCl3 as an activating agent and source of magnetic particles respectively. The result indicated that the optimal condition to obtain ACs with a high SBET (1405 m2/g) and the largest mesopore volume (0.54 cm3/g) was using the weight ratio of ZnCl2 to CR of 3 (3AC). While, the magnetic mesoporous carbon with the highest SBET (554 m2/g) was yielded when addition of FeCl3 into the reaction mixture with a FeCl3 to ZnCl2 weight ratio of 1(3AC-1M). 3AC and 3AC-1M were tested as adsorbents to investigate the adsorption efficiency of methylene blue (MB) in water. The adsorption behavior of MB on 3AC and 3AC-1M were monolayer adsorption based on the Langmuir isotherm model with R2 of 0.9993 and 0.9953, respectively. 3AC showed the MB adsorption capacity of 274 mg/g which is comparable to that of commercial ACs. 3AC-1M that adsorbs MB with the maximum capacity of 102 mg/g, was separated from aqueous solution easily using an external magnet. This study demonstrates that the carbon precursors from biomass waste as CR can be conveniently converted into efficient carbonaceous adsorbents and functionalized for example by adding magnetic properties into the carbon structure to enable manipulations in industrial operations.
References
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