ABSTRACT
Fe3O4 nanoparticles were embedded within a glauconitecalcium alginate (G/CA) matrix to create magnetic hybrid spheres (MNPs-G/CA), with the aim of purifying water from methylene blue (MB) at temperatures of 25, 40, and 50 °C. MNPs-G/CA adsorbent was characterized using numerous techniques, including elemental mapping, zeta potential, FTIR, FESEM, XRD, EDX, and TEM. The greatest amount of the removed MB was achieved under definite conditions of solution pH 8.0, MNPs-G/CA mass (25 mg), interaction time (2 h), and 200 mg/L of MB concentration. The MB uptake process kinetic followed a pseudo-second-order equation (R2 > 0.99) at all tested temperatures. The equilibrium data were fitted to a statistical physics multilayer model in conjunction with the Langmuir and Freundlich equations. The steric n parameter reveals that MNPs-G/CA adsorbent possesses a mixed adsorption orientation (i.e., ranging from 0.69 to 0.93) across various temperatures. The amount of MNPs-G/CA active positions (the NM parameter) was progressively increased from 245 mg/g to 419 mg/g. The measured adsorption capacities (Qsat) ranged from 466.49 to 664.37 mg/g, and the removal of MB molecules was consistent with an endothermic interaction. The interface between the MNPs-G/CA-MB was principally dictated by electrostatic attractions, as evidenced by the values of adsorption energies (∆E), which varied from 16.75 to 21.52 kJ/mol. The regenerated MNPs-G/CA offered over 80 % of its adsorption strength after the fourth adsorption-desorption cycle. This study contributes to our understanding of the physicochemical parameters controlling the MB adsorption mechanism on multifunctional hybrid adsorbents, like the interface between glauconite, alginate, and MNPs.
ABSTRACT
This study reports a potential approach for the valorization of glass waste (GW) that is mainly composed of amorphous silica to prepare lightweight foamed glass (FG). The preparation of FG was achieved by mixing sodium hydroxide with GW powder followed by sintering at a temperature of 800 °C. As-synthesized FG was characterized and applied as an effective adsorbent for the removal of hazardous organic water contaminants, in particular, methylene blue (MB) dye. FG exhibited porosity of 91%, bulk density of 0.65 g/cm3, compressive strength of 4 MPa, and thermal conductivity of 0.27 W/m·K. Theoretical treatment indicated that a monolayer model with one energy site was the best in fitting the removal of MB molecules. The number of MB molecules per active site (n) ranged from 2.20 to 1.70, suggesting vertical orientation and a multi-molecular adsorption mechanism. The density of FG receptor sites (DM) increased with the temperature, and this parameter played a vital role in the adsorption process. The adsorption capacity (Qsat) increased from 255.11 to 305.58 mg/g, which signifies endothermic interactions. MB adsorption on FG was controlled by physical forces such as electrostatic interactions (i.e., the adsorption energies were <20 kJ/mol). The results of this study prove the feasibility of glass waste as an effective and low-cost adsorbent for water remediation.
ABSTRACT
[This corrects the article DOI: 10.1021/acsomega.1c01514.].
ABSTRACT
Chitosan/diatomite nanocomposite (CS/D) was synthesized as a low-cost and highly porous structure of enhanced physicochemical properties to be applied as advanced carriers for ibuprofen drug (IB). The loading properties of CS/D were studied in comparison to diatomite as a separated phase and achieved a loading capacity of 562.6 mg/g. The loading reactions of IB into CS/D show pseudo-second-order kinetic behavior and Langmuir isotherm properties. This demonstrates homogeneous loading processes in monolayer forms and controlled essentially by physical mechanisms. This was confirmed by the calculated Gaussian energy (7.7 kJ/mol (D) and 7.9 kJ/mol (CS/D)) in addition to the thermodynamic parameters. The thermodynamic behavior for the IB loading process is related to spontaneous, favorable, and exothermic reactions. The CS/D composite is of promising IB release profile that extended to about 200 h with a maximum release of 91.5% at the gastric fluid (pH 1.2) and 97.3% in the intestinal fluid (pH 7.4). The IB release rate from CS/D can be controlled based on the ratio of the integrated chitosan in the composite. The IB release reactions from CS/D follow the assumption of Korsmeyer-Peppas kinetics with determined values for the diffusion exponent reflects complex diffusion and erosion as the affected mechanisms during the IB release process.