Exploring the Iron Oxide Functionalized Biobased Carbon-silica-polyethyleneimine Composites for Hexavalent Chromium Removal from Dilute Aqueous Solutions

The contamination of water resources by toxic hexavalent chromium remains a challenge. In this study, amino-functionalized iron oxide biobased carbon-silica composites were prepared through co-precipitation of Fe(II) and Fe(III) over Macadamia activated carbon and explored as feasible adsorbents for the removal of Cr(VI) from dilute aqueous solutions. The energy dispersive spectroscopy (EDS) elemental analysis confirmed the existence of Fe, Si, O, and C atoms, which form the backbone of the composite. The FTIR also showed the presence of Fe-O and Si-O-Si and Si-OH spectral bands, affirming the backbone of the adsorbents. Cr(VI) adsorption efficiency (5.76 mg/g) was achieved at pH 1 when an initial concentration of 2.5 mg/L, contact time of 90 min, and dosage concentration of 1.7 g/L were used. The data were best described by the Langmuir adsorption model and pseudo-second-order rate model. ΔG° (−3 to −12 kJ/mol) and ΔH° (46, 12 and 5 kJ/mol) values affirmed that the adsorption of Cr(VI) was spontaneous and endothermic and dominated by chemical interactions.

Aizoon Extract As a Novel Eco-friendly Corrosion Inhibitor For Stainless Steel430 in HCl Solution

Aizoon extract used as anti-corrosion for stainless steel430 (SS430) in 2M hydrochloric acid solution. The mass reduction, electrochemical impedance, and potentiodynamic polarization were carried out to demonstrate the performance of Aizoon extract as corrosion resistance for SS430. Polarization revealed that the Aizoon extract is mixed type inhibitor with superiority to inhibiting the cathodic reaction. The inhibition percentage reaches 93% at 300 ppm extract. Adsorption of the extract on SS430 surface is regular with Langmuir adsorption model. Thermodynamic factors for adsorption and activation processes for SS430 dissolution were estimated and discussed. Furthermore, the SS430 surface is characterized using different techniques. The surface morphology of SS430 was tested utilizing several techniques. The experimental data were supported by the theoretical data.

PREPARATION AND CHARACTERIZATION OF ACTIVATED CARBON FROM OIL-PALM FIBER AND ITS EVALUATION FOR METHYLENE BLUE ADSORPTION

A new type of activated carbon was produced from oil-palm fiber using steam activation. Scanning electron microscopy (SEM) was performed on the surface of oil-palm-fiber activated carbon (OPF-AC). The spectra of OPF-AC was investigated with Fourier-transform infrared (FTIR) spectroscopy. The effects of the temperature, adsorbent dose, adsorption time and pH on the adsorption properties of methylene blue on OPF-AC were discussed. The Langmuir adsorption model and Freundlich adsorption model were used to find the adsorption equilibrium isotherm. Adsorption kinetics were employed to explain the adsorption process and predict the adsorption efficiency. The Van’t Hoff equation was used to assess the impact exerted by the adsorption temperature on the adsorbing process. According to the results, the data of the adsorption equilibrium of OPF-AC fit well the Langmuir adsorption model and the kinetics data can be gathered into a pseudo-second-order kinetic model. The adsorption behavior of methylene blue on OPF-AC was endothermic and spontaneous. The total pore volume and BET surface area of OPF-AC reached 0.7809 cm3/g and 1018.84 m2/g, respectively. The maximum adsorption capacity of OPF-AC was 862.07 mg/g at 323 K. Accordingly, the gratifying adsorption of OPF-AC endows it with a promising prospect in the application field of agricultural adsorbents.

Solvent Extraction of Scandium and Yttrium Using Carboxylic Acid

Separation of scandium (Sc) from yttrium (Y) in aqueous chloride media by solvent extraction using Versatic acid 10 was investigated. Conventional slope analysis method revealed the extraction equilibrium formulation of the metals. Sc is more strongly extracted than Y by Versatic acid 10, and the separation factor of the metals is quite high at 1.93 × 104. Complete stripping of Sc from the loaded organic solution of Versatic acid 10 was achieved by 3M HCl solution. Then Versatic acid 10 was applied to solvent impregnated resin (SIR), separation of Sc was progressed via Langmuir adsorption model.

Adsorption of Lead(II) Ions using Coconut Fiber’s (Cocos nusifera L.) Activated by Sodium Hydroxide

The use of green coconut fiber waste to adsorb lead(II) ions has been successfully carried out. Coconut fiber was activated first using sodium hydroxide before being used as an adsorbent. The optimum time needed for green coconut fiber to adsorb lead(II) ions was 30 minutes with the percentage of ions adsorbed by 94.34%. The lead(II) adsorption kinetics on green coconut fiber model with R2 value of 0.999 and k value of 38.95 x 10-4 minutes-1. Adsorption isotherm from lead(II) on coconut fiber followed the Langmuir adsorption model with R2 value of 0.984 and adsorption capacity of 0.070 g.mg-1.

Solvothermal Synthesis of Humic Acid-Supported CeO2 Nanosheets Composite as High Performance Adsorbent for Congo Red Removal

Surface properties and structures of materials are essential for their adsorption of pollutants in water. Humic acids (HA)-supported CeO2 nanosheet composites are synthesised by solvothermal method. The size of CeO2 nanosheets are approximately 100–500 nm. The obtained composite exhibits superior adsorption ability for Congo Red (CR) in water, which can be attributed to its unique structure and highly dispersed CeO2 nanosheet. The composite’s adsorption behaviour of CR follows a pseudo-second-order mode and Langmuir adsorption model well, and the maximum adsorptive capacity for CR achieves 260 mg g−1. The presence of CeO2 nanosheets enhances surface area and enriches the mesoporous structure of the composites, thereby promoting CR adsorption capacity.

Adsorption of Ni2+ and Cu2+ from Aqueous Solution by Polyethylenimine Impregnation of Metal–Organic Frameworks

A series of UiO-66-PEI materials were obtained by impregnating UiO-66 with different amounts of polyethylenimine (PEI) with UiO-66 as the basic skeleton material. The materials were used as adsorbents to remove Ni[Formula: see text] and Cu[Formula: see text] from water. The prepared UiO-66-PEI-30 had good adsorption capacity on Ni[Formula: see text] and Cu[Formula: see text] at 30% PEI. The adsorption of Ni[Formula: see text] and Cu[Formula: see text] with UiO-66-PEI-30 was further studied. The role of eluent types, elution time, concentration and volume on the effect of Cu[Formula: see text] elution was investigated. The adsorption of Ni[Formula: see text] and Cu[Formula: see text] by UiO-66-PEI-30 followed the pseudo-second-order kinetic model and Langmuir adsorption model. The maximum adsorption capacities obtained by Langmuir fitting for Ni[Formula: see text] and Cu[Formula: see text] were 11.54[Formula: see text]mg[Formula: see text]g[Formula: see text] and 24.87[Formula: see text]mg[Formula: see text]g[Formula: see text], respectively. After four desorption/adsorption experiments, UiO-66-PEI-30 still showed good adsorption performance. UiO-66 impregnated with PEI was an adsorbent with adsorption potential.

Thermodynamics of adsorption of food colours

Thermodynamics of adsorption of two synthetic food colours, Tartrazine and Brilliant blue, was investigated. The adsorbent used was activated carbon, produced from saw dust waste. For each of the food colours, equilibrium studies were carried out at different temperatures (308 K, 318 K, 328 K and 338 K). The Langmuir adsorption model was employed for equilibrium studies. Amount of colour adsorbed per gram of adsorbent, at equilibrium, was influenced by molecular size of adsorbate and temperature. Adsorption at the tartrazine-adsorbent interface was exothermic, while that at the brilliant blue-adsorbent interface was endothermic. Adsorption of tartrazine was associated with a negative entropy change, while there was increased degree of disorderliness at the brilliant blue-adsorbent interface. Each of the adsorbate-adsorbent systems was associated with positive change in Gibbs free energy, within the range of temperature employed in this work.

A new method to determine varying adsorbed density based on Gibbs isotherm of supercritical gas adsorption

In the calculation of the absolute adsorption of supercritical gas adsorbed on the microporous materials, most existing methods regard the adsorbed density as a constant, which is very unreasonable. In this study, an extended pressure point method combined with Langmuir adsorption model is proposed in which the varying adsorbed density under different pressures is considered at the same time. The utility of the proposed method to correlate accurately the experimental data for supercritical gas adsorption system is demonstrated by high-pressure methane adsorption measurements on two groups of shale samples. Taking advantage of the proposed method, we can obtain the adsorbed density and the adsorbed volume corresponding to different pressures. Compared with the conventional methods under the assumption of fixed and parameterized adsorbed density, the proposed method yields better fitting results with the experimental data. Our work should provide important fundamental understandings and insights into the supercritical gas adsorption system.