Fabrication and optimization calix[8]arene-PbS nanoadsorbents for the adsorption of methylene blue: Isotherms, kinetics and thermodynamics studies

Investigation on Methylene Blue Dye Adsorption in Aqueous by the Modified Mussel Shells: Optimization, Kinetic, Thermodynamic and Equilibrium Studies

This study assessed the methylene blue adsorption using natural and modified mussel shell powders in the aqueous solution. The mussel shell samples were processed in a NaClO solution then modified with sodium dodecyl sulfate and ethylenediaminetetraacetic acid. The characteristics of mussel shell samples before and after modification were demonstrated using infared spectroscopy, thermogravimetric analysis, scanning electron microscopy, nitrogen adsorption/desorption, energy dispersive X-ray, water contact angle, and dynamic light scattering methods. Some factors such as the pH of the medium, adsorption temperature, and adsorption time had a significant effect on the methylene blue adsorption of mussel shell samples. The adsorption isotherm models and kinetics of methylene blue adsorption by mussel shell samples were also studied. A quadratic regression equation was selected with experimental planning following the Box-Behnken model combined with Design Expert 11.1.0.1 software to optimize the methylene blue adsorption process by mussel shell samples. These results open a promising direction for using naturally derived materials to remove organic pollutants from contaminated water.

Preparation of Chitosan/β-Cyclodextrin Composite Membrane and Its Adsorption Mechanism for Proteins

A significant portion of the protein in food waste will contaminate the water. The chitosan/modified β-cyclodextrin (CS/β-CDP) composite membranes were prepared for the adsorption of bovine serum albumin (BSA) in this work to solve the problem of poor adsorption protein performance and easy disintegration by a pure chitosan membrane. A thorough investigation was conducted into the effects of the preparation conditions (the mass ratio of CS and β-CDP, preparation temperature, and glutaraldehyde addition) and adsorption conditions (temperature and pH) on the created CS/β-CDP composite membrane. The physical and chemical properties of pure CS membrane and CS/β-CDP composite membrane were investigated. The results showed that CS/β-CDP composite membrane has better tensile strength, elongation at break, Young's modulus, contact angle properties, and lower swelling degree. The physicochemical and morphological attributes of composite membranes before and after the adsorption of BSA were characterized by SEM, FT-IR, and XRD. The results showed that the CS/β-CDP composite membrane adsorbed BSA by both physical and chemical mechanisms, and the adsorption isotherm, kinetics, and thermodynamic experiments further confirmed its adsorption mechanism. As a result, the CS/β-CDP composite membrane of absorbing BSA was successfully fabricated, demonstrating the potential application prospect in environmental protection.

Sustainable phosphorylated microcrystalline cellulose toward enhanced removal performance of methylene blue

In this study, microcrystalline cellulose (MCC) was phosphorylated using phosphoric acid in the presence of urea and used as an adsorbent for methylene blue (MB) dye removal from an aqueous solution. The obtained products were characterized by different techniques. Batch adsorption experiments were conducted under varying conditions of incubation time, initial MB concentration, pH, and phosphorylation degree. All the samples exhibited similar and fast adsorption kinetics, described by pseudo-second-order model for MB adsorption, whereas the retention capacity depended significantly on the phosphate content and the surface charge of the adsorbents. The experimental adsorption data in the examined MB initial concentrations (0-2000 mg/L) were best suited by the Langmuir isotherm model. The study revealed that the presence of phosphates groups in the cellulose structure significantly enhanced the adsorption of the MB pollutant. The maximum dye removal capacity at pH of 7 was obtained for the phosphorylated microcrystalline cellulose (284.03 mg/g) with a high phosphorylation degree (1.92 % of P), which is 20 times higher than unmodified MCC (15.29 mg/g). This property increased from 284.03 to 328.32 mg/g when increasing the pH from 7 to 11. The MB adsorption mechanism involves hydrogen bonding, electrostatic and ion-dipole interactions. These findings are relevant to a better understanding of the role of cellulose phosphorylation in the recovery of organic dyes from the waste liquid of many industries.

Surface Characteristics of Electrospun p-Sulphonated Calix[4]Arene Functionalized Cellulose Acetate Nanofiber and Its Behaviour towards Methylene Blue Adsorption

p-sulphonated calix[4]arene (p-SOCX) functionalized cellulose acetate/graphene oxide (CA/GO) nanofibers were successfully prepared via the electrospinning technique. The presence of p-SOCX within the fiber matrix was ascertained using Fourier Transform Infrared spectroscopy and Carbon-Hydrogen-Nitrogen-Sulphur elemental analyses. Apparent changes in morphology of the samples were observed under scanning electron microscope where fiber diameters increased with increasing p-SOCX content. Preliminary dye removal test at different pH, dosage, and temperature of functionalized CA/GO nanofiber demonstrates enhanced adsorption capacity of methylene blue in presence of p-SOCX compared to pristine CA nanofiber and CA/GO nanofiber at an optimum pH 8. The highest removal efficiency obtained was 88.84% with initial methylene blue dye concentration of 10 mg/L, adsorbent dosage of 20 mg/10 mL, contact time of 30 min at room temperature ca. 293 K.

Study on a Hydrogel for Adsorption of Chloride Ions in Cementitious Materials

Chloride ions in the seaside environment can corrode the steel reinforcement in concrete, which greatly endangers the safety of seaside structures. As an excellent adsorption material, hydrogel is widely used in the field of water treatment but is rarely used in cementitious materials. In this study, a polyacrylamide–chitosan hydrogel (PAMC) was prepared with N,N-methylenebisacrylamide as the cross-linking agent and acrylamide as the monomer. The prepared PAMC gel could effectively adsorb chloride ions in simulated seawater and simulated sea sand environments, and the maximum adsorption capacity of chloride ions by PAMC-1 (prepared from 2.5 g acrylamide and 1% content of N,N-methylenebisacrylamide relative to acrylamide) gels in simulated seawater was 55.53 mg/g. The adsorption behavior of the PAMC gels in solution fit the Langmuir isotherm model. The composition and morphology of the PAMC gel were characterized, and the responsiveness of the PAMC gel to the environment was studied. The results showed that the PAMC gels adsorbed better in alkaline environments and thus could be used in alkaline cement-based environments. The mortar sample containing the PAMC-1 gel had higher resistance to chloride ion penetration, and the chloride ion content at 7.5–10mm from the surface of the sample cured for 28 days was reduced by 41.4% compared to the samples without the gel.