Preparation and characterization of poly(acrylic acid-co-acrylamide)/montmorillonite composite and its application for methylene blue adsorption

Highly effective removal of basic fuchsin dye using carboxymethyl konjac glucomannan grafted acrylic acid-acrylamide/montmorillonite composite hydrogel

This study developed a nanocomposite hydrogel, CAM4-MMT, for efficiently removing basic fuchsin dye from water. The hydrogel was prepared by grafting a copolymer of acrylic acid (AA) and acrylamide (AM) onto carboxymethyl konjac glucomannan (CMKGM), and doped with montmorillonite (MMT), exhibited excellent thermal stability, a porous inner structure, large specific surface area (1.407 m2/g), and high swelling capacity (107.3 g/g). The hydrogel achieved a maximum adsorption capacity of 694.1 mg/g and a removal rate of 99.5 %. The Langmuir isotherm and pseudo-second-order kinetic model best described the adsorption process. Regeneration and reuse tests confirmed that the hydrogel has excellent recyclability. In conclusion, the CAM4-MMT composite hydrogel efficiently removed basic fuchsin from water solutions, offering a new scheme for eliminating basic fuchsin using natural polysaccharides with promising applications.

Comparison of Structural, Water-Retaining and Sorption Properties of Acrylamide-Based Hydrogels Cross-Linked by Physical and Chemical Methods

Two series of hydrogels based on acrylamide and its copolymers with acrylonitrile and acrylic acid were synthesized by two cross-linking methods - chemical (using N,N'-methylene bis-acrylamide) and physical (using montmorillonite (MMT)) ones. The structure of the gels was characterized by Fourier Transform Infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The swelling and sorption properties were analyzed as a function of both the monomer composition and the cross-linking method. The shift of the band corresponding to Si-O (995-1030 cm-1 ) confirmed the formation of intercalation structures for MMT-cross-linked gels. Moreover, physically cross-linked gels demonstrated a non-monotonic dependence of the swelling degree on the MMT concentration, and acrylamide-acrylic acid copolymer MMT-cross-linked gels showed pH sensitivity and the highest swelling degree of 150 g/g. The highest sorption capacity towards cadmium(II) ions was demonstrated by acrylamide-acrylic acid copolymer gels, both covalently cross-linked (30 mg/g) and MMT-cross-linked (8.9 mg/g).

Removal of highly concentrated methylene blue dye by cellulose nanofiber biocomposites

The contamination of water by dyes in high concentrations is a worldwide concern, and it has prompted the development of efficient, economical, and environmentally friendly materials and technologies for water purification. The hydration and adsorption capacity for methylene blue (MB) in biocomposites (BCs) based on cellulose nanofiber (CNF) (0 to 2 wt%) were studied. BCs were synthesized through a simple and straightforward route and characterized by spectroscopy, microscopic techniques and thermogravimetric analysis, among others. Hydration studies showed that BCs prepared with 2 wt% of CNF can absorb large volumes of water, approximately 2274 % in the case of poly 2-acrylamide-2-methyl-1-propanesulfonic acid (PAMPS)-CNF and 2408 % in poly sodium 4-styrene sulfonate (PSSNa)-CNF. These BCs showed outstanding adsorption capacity for highly concentrated MB solutions (4536 mg g^-1 PAMPS-CNF and 11,930 mg g^-1 PSSNa-CNF). It was confirmed that the adsorption mechanism is through electrostatic interactions. Finally, BCs showed high MB adsorption efficiency after several sorption-desorption cycles and on a simulated textile effluent. Furthermore, the theoretical results showed a preferential interaction between MB and the semiflexible polymer chains at the lowest energy setting. The development and study of a new adsorbent material with high MB removal performance that is easy to prepare, economical and reusable for potential use in water purification treatments was successfully achieved.

Synthesis of activated carbon-surfactant modified montmorillonite clay-alginate composite membrane for methylene blue adsorption

In this research work, a novel composite membrane was synthesized from activated carbon (AC) derived from sesban, sodium benzyl dodycyel sulphate (SBDS) treated montmorillonite (MMT) clay and alginate (alg) for the adsorption of methylene-blue (MB) dye. The AC-MMT-alg composite membranes were characterized using analytical characterizations such as FTIR, SEM, EDX and TGA analysis. Several important factors like initial solution pH, contact time, membrane dose, MB concentrations and temperature effect on the adsorption efficiency of membrane were investigated. MB dye adsorption on the synthesized membrane was explained well by pseudo second order equation. Isotherm study showed that MB adsorption data followed Langmuir adsorption isotherm model. The adsorption capacity of membrane for MB was 1429 mg/g from aqueous solution. Thermodynamic study confirmed endothermic and spontaneous MB adsorption on the adsorbent. The mechanistic path way indicated that electrostatic forces were involved in this adsorption process. The synthesized membrane proved an efficient adsorbent for MB adsorption from aqueous media.

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.

Easy Preparation of Liposome@PDA Microspheres for Fast and Highly Efficient Removal of Methylene Blue from Water

Mussel-inspired chemistry was usefully exploited here with the aim of developing a high-efficiency, environmentally friendly material for water remediation. A micro-structured material based on polydopamine (PDA) was obtained by using liposomes as templating agents and was used for the first time as an adsorbent material for the removal of methylene blue (MB) dye from aqueous solutions. Phospholipid liposomes were made by extrusion and coated with PDA by self-polymerization of dopamine under simple and mild conditions. The obtained Liposome@PDA microspheres were characterized by DLS and Zeta potential analysis, TEM microscopy, and FTIR spectroscopy. The effects of pH, temperature, MB concentration, amount of Liposome@PDA, and contact time on the adsorption process were investigated. Results showed that the highest adsorption capacity was obtained in weakly alkaline conditions (pH = 8.0) and that it could reach up to 395.4 mg g⁻¹ at 298 K. In addition, adsorption kinetics showed that the adsorption behavior fits a pseudo-second-order kinetic model well. The equilibrium adsorption data, instead, were well described by Langmuir isotherm. Thermodynamic analysis demonstrated that the adsorption process was endothermic and spontaneous (ΔG⁰ = −12.55 kJ mol⁻¹, ΔH⁰ = 13.37 kJ mol⁻¹) in the investigated experimental conditions. Finally, the applicability of Liposome@PDA microspheres to model wastewater and the excellent reusability after regeneration by removing MB were demonstrated.

Green Electrospun Membranes Based on Chitosan/Amino-Functionalized Nanoclay Composite Fibers for Cationic Dye Removal: Synthesis and Kinetic Studies

Chitosan/poly(vinyl alcohol)/amino-functionalized montmorillonite nanocomposite electrospun membranes with enhanced adsorption capacity and thermomechanical properties were fabricated and utilized for the removal of a model cationic dye (Basic Blue 41). Effects of nanofiller concentrations (up to 3.0 wt %) on the morphology and size of the nanofibers as well as the porosity and thermomechanical properties of the nanocomposite membranes are studied. It is shown that the incorporation of the nanoclay particles with ∼10 nm lateral sizes into the polymer increases the size of the pores by about 80%. To demonstrate the efficiency of the adsorbents, the dye removal rate is investigated as a function of pH, adsorbent dosage, dye concentration, and nanofiller loading. The highest and fastest dye removal occurs for the nanofibrous membranes containing 2 wt % nanofiller, where about 80% of the cationic dye is removed after 15 min. This performance is at least 20% better than the pristine chitosan/poly(vinyl alcohol) membrane. The thermal stability and compression resistance of the nanocomposite membranes are found to be higher than those of the pristine membrane. In addition, reusability studies show that the dye removal performance of this nanocomposite membrane reduces by only about 5% over four cycles. The adsorption kinetics is explained by the Langmuir isotherm model and is expressed by a pseudo-second-order kinetic mechanism that determines a spontaneous chemisorption process. The results of this study provide a valuable perspective on the fabrication of high-performance, reusable, and efficient electrospun fibrous nanocomposite adsorbents.

A novel Fe3+-stabilized magnetic polydopamine composite for enhanced selective adsorption and separation of Methylene blue from complex wastewater

Herein, a novel Fe³⁺-stabilized magnetic polydopamine composite (Fe₃O₄/PDA-Fe³⁺) was facilely constructed, systematically characterized, and subsequently applied for the first time as a versatile adsorbent for treatment of Methylene blue (MB) in complex wastewater. Results showed that as-prepared material had prominent adsorption ability toward MB in its single dye solution over a wide pH range (3-10) with q_max value of 608.8 mg/g at 318 K. More interestingly, MB could be selectively captured by resulting adsorbent from mixed dye solutions (MB-cationic dye and MB-anionic dye) and complex aqueous solution with high ionic strength up to 0.5 mol/L NaCl. It was eventually revealed that the enhanced and selective adsorption of MB by as-resultant adsorbent was due to the synergistic effects between multiple uptake mechanisms. What's more, its adsorption efficiency toward MB in simulated wastewater still maintained higher than 80 % of its original uptake performance after several runs of adsorption-desorption. Additionally, it exhibited more superior uptake performance toward MB than commercial powder activated carbon (PAC) in column adsorption system. Thus, the outstanding sorption ability, unique capture selectivity, as well as excellent stability and recyclability for model wastewater endow it a promising candidate adsorbent for selective adsorption and separation of MB from complex wastewater.

Preparation and characterization of novel mesoporous chitin blended MoO3-montmorillonite nanocomposite for Cu(II) and Pb(II) immobilization

A novel mesoporous chitin blended MoO₃-Montmorillonite nanocomposite was prepared through three-steps synthesis. First, chitin was extracted from prawn shell then MoO₃-MMT was prepared, and lastly, chitin was blended with MoO₃-MMT. Chitin-MoO₃-MMT was applied for the removal of Cu(II) and Pb(II) from wastewater. XRD characterization revealed MoO₃ solubility in MMT interlayers, SEM showed a nanocomposite formation with sharp nanorods like-structure and length ranging from 60 to 77.7 nm. FTIR exhibited fundamental changes in the surface functional groups after adsorption. XPS analysis before and after adsorption showed the domination of chemical bonding with N and O. N₂ adsorption-desorption isotherm displayed H₃-type hysteresis loop and a pore size diameter of 10.67 nm confirming the mesoporous nature. Adsorption efficiency was studied as a function of pH, time, metal concentration and adsorbent mass. Adsorption capacity (Q_e) values were 19.03 and 15.92 mg.g^-1 for Cu(II) and Pb(II) respectively. The metal surface coverage mapping was 1.87 × 10^¹⁹ and 4.34 × 10^¹⁸ atoms/m² for Cu(II) and Pb(II) respectively. Adsorption followed Langmuir isotherm and pseudo-second-order (PSO) kinetics suggesting a monolayer chemisorption domination. Intraparticle diffusion (IPD) model showed a boundary layer control. Thermodynamically, the adsorption was spontaneous and endothermic with activation energies 25.94 and 29.37 kJ.mol^-1 for Cu(II) and Pb(II) respectively.