Process Optimization and Adsorptive Mechanism for Reactive Blue 19 Dye by Magnetic Crosslinked Chitosan/MgO/Fe3O4 Biocomposite

A new biocomposite magnetic crosslinked glutaraldehyde-chitosan/MgO/Fe3O4 (CTS-GL/MgO/Fe3O4) adsorbent was prepared and applied for the removal of reactive blue 19 (RB 19) synthetic textile dye. The prepared CTS-GL/MgO/Fe3O4 was subjected to the several instrumental characterizations such as XRD, FTIR, SEM-EDX, pH-potentiometric titration, and pHpzc analyses. The influence of the input adsorption parameters such as A: CTS-GL/MgO/Fe3O4 dosage, B: initial solution pH, C: process temperature, and D: contact time on RB 19 removal efficiency was statistically optimized using Box-Behnken design (BBD). The analysis of variance (ANOVA) indicates the presence of five significant statistical interactions between input adsorption parameters i.e. (AB, AC, AD, BC, and BD). The adsorption kinetic and equilibrium study reveals a good to the pseudo-second-order model, and multilayer adsorption as proven by Freundlich isotherm model, respectively. The maximum adsorption capacity of CTS-GL/MgO/Fe3O4 towards RB19 was found to be 193.2 mg/g at 45 ºC. This work highlights the development of feasible and recoverable magnetic biocompsite adsorbent with desirable adsorption capacity towards textile dyes with good separation ability by using an external magnetic field.

Magnetic Chitosan-Glutaraldehyde/Zinc Oxide/Fe3O4 Nanocomposite: Optimization and Adsorptive Mechanism of Remazol Brilliant Blue R Dye Removal

A magnetic Schiff’s base chitosan-glutaraldehyde/Fe3O4 composite (CHT-GLA/ZnO/Fe3O4) was developed by incorporating zinc oxide (ZnO) nanoparticles into its structure to prepare an efficient adsorbent for the removal of remazol brilliant blue R (RBBR) dye. The CHT-GLA/ZnO/Fe3O4 was characterized by the following methods: CHN, BET, FTIR, XRD, SEM-EDX, pHpzc, and potentiometric titrations. Box-Behnken design based on response surface methodology was used to optimize the effects of the A: ZnO nanoparticles loading (0–50%), B: dose (0.02–0.1 g), C: pH (4–10), D: temperature (30–60°C), and time E: (10–60 min) on the synthesis of the magnetic adsorbent and the RBBR dye adsorption. The experimental data of kinetics followed the pseudo-second order model, while isotherms showed better fit to Freundlich and Temkin models. The maximum adsorption capacity of the target nanocomposite (CHT-GLA/Fe3O4 containing 25% ZnO or CHT-GLA/ZnO/Fe3O4-25) was reached of 176.6 mg/g at 60°C. The adsorption mechanism of RBBR onto CHT-GLA/ZnO/Fe3O4 nanocomposite can be attributed to multi-interactions including electrostatic attractions, hydrogen bonding, Yoshida H-bonding, and n-π interactions. This study offers a promising hybrid nanobiomaterial adsorbent in environmental nanotechnology to separate and remove the contaminants such as organic dyes from wastewater.

Adsorptive Desulfurization of Organic Sulfur from Model Fuels by Active Carbon Supported Mn (II): Equilibrium, Kinetics, and Thermodynamics

Mn (II)/AC adsorbents were prepared by ultrasonic impregnation. The 2 wt. % Mn/AC showed best adsorptive performance, and the optimal adsorption temperature was 313 K. Benzene, methylbenzene, and naphthalene were used to explore the adsorptive selectivity of Mn/AC, indicating that Mn could enhance the adsorptive capacity but could not improve the adsorptive selectivity. The adsorptive mechanism was mostly like to be π-complex. Adsorptive isotherms and kinetics were investigated, and the parameters were calculated. The R2, RMSE, and AICc were used to assess the optimal model. The results showed that Temkin adsorptive isotherm was more suitable to describe the isothermal data; the MPnO kinetics model was more superior to other kinetic models. The order of reaction was between 1 and 2. The outcome of adsorptive thermodynamics indicated that removal of DBT onto Mn/AC was a spontaneous and exothermic process.

Adsorptive removal of Ni2+ and Cd2+ from wastewater using a green longan hull adsorbent

The adsorptive removal of Ni2+ and Cd2+ at concentrations of approximately 50 mg L−1 in wastewater is investigated using an agricultural adsorbent, longan hull, and the adsorptive mechanism is characterized. The maximum adsorption capacity of approximately 4.19 mg g−1 Cd2+ was obtained under the optimized conditions of room temperature, pH 5.0, and a solid-to-liquid ratio of 1:30 in approximately 15 min. For Ni2+, the maximum adsorption capacity of approximately 3.96 mg g−1 was obtained at pH 4.7 in approximately 20 min. The adsorption kinetics for both metal ions on the longan hull can be described by a pseudo second-order rate model and are well fitted to the Langmuir adsorption isotherm. The adsorption mechanism of the longan hull to Ni2+ and Cd2+ ions is shown to be a monolayer adsorption of metal ions onto the absorbent surface. Thereinto, the longan hull adsorbent contains N–H, C–H, C=O, and C=C functional groups that can form ligands when loaded with Ni2+ and Cd2+, which reduces the fluorescence of the dried longan hull material.