Adsorptive Removal of Acid Blue 80 Dye from Aqueous Solutions by Cu-TiO 2

The adsorption performance of a Cu-TiO2 composite for removing acid blue 80 (AB80) dye from aqueous solutions was investigated in terms of kinetics, equilibrium, and thermodynamics. The effect of operating variables, such as solution pH, initial dye concentration, contact time, and temperature, on AB80 adsorption was studied in batch experiments. AB80 adsorption increased with increasing contact time, initial dye concentration, and temperature and with decreasing solution pH. Modeling of adsorption kinetics showed good agreement of experimental data with the pseudo-second-order kinetics model. The experimental equilibrium data for AB80 adsorption were evaluated for compliance with different two-parameter, three-parameter, and four-parameter isotherm models. The Langmuir isotherm model best described the AB80 adsorption equilibrium data. The thermodynamic data revealed that the AB80 adsorption process was endothermic and nonspontaneous. Kinetics, equilibrium, and thermodynamic results indicate that Cu-TiO2 adsorbs AB80 by a chemical sorption reaction

Chromium Biosorption from Cr(VI) Aqueous Solutions by Cupressus lusitanica Bark: Kinetics, Equilibrium and Thermodynamic Studies.

The present study investigated the kinetics, equilibrium and thermodynamics of chromium (Cr) ion biosorption from Cr(VI) aqueous solutions by Cupressus lusitanica bark (CLB). CLB total Cr biosorption capacity strongly depended on operating variables such as initial Cr(VI) concentration and contact time: as these variables rose, total Cr biosorption capacity increased significantly. Total Cr biosorption rate also increased with rising solution temperature. The pseudo-second-order model described the total Cr biosorption kinetic data best. Langmuir´s model fitted the experimental equilibrium biosorption data of total Cr best and predicted a maximum total Cr biosorption capacity of 305.4 mg g(-1). Total Cr biosorption by CLB is an endothermic and non-spontaneous process as indicated by the thermodynamic parameters. Results from the present kinetic, equilibrium and thermodynamic studies suggest that CLB biosorbs Cr ions from Cr(VI) aqueous solutions predominantly by a chemical sorption phenomenon. Low cost, availability, renewable nature, and effective total Cr biosorption make CLB a highly attractive and efficient method to remediate Cr(VI)-contaminated water and wastewater

Parameters of the Langmuir and Freundlich isotherm models for total Cr biosorption onto <i>C</i>. <i>lusitanica</i> bark.

<p>Parameters of the Langmuir and Freundlich isotherm models for total Cr biosorption onto <i>C</i>. <i>lusitanica</i> bark.</p

Variations of Cr(VI) (a), total Cr (b) and Cr(III) (c) concentration with respect to contact time at different solution temperatures.

<p>[Temperature (°C): (✳) 15, (⬜) 28, (▼) 35, (○) 45]. CLB concentration: 1 g L^-1; pH = 1.5±0.1; initial Cr(VI) concentration = 100 mg L^-1.</p

Variations of Cr(VI) (●), total Cr (○) and Cr(III) (✳) concentration with respect to contact time at different initial Cr(VI) concentrations.

<p>[Concentration (mg L^-1): (a) 20, (b) 60, (c) 80, (d) 150, (e) 200, (f) 300, (g) 400, (h) 800, (i) 1000]. CLB concentration: 1 g L^-1; pH = 1.5±0.1; temperature = 28±2°C.</p

Scanning electron micrographs of CLB at (a) 85×, (b) 500× and (c) 3000× magnification.

<p>Scanning electron micrographs of CLB at (a) 85×, (b) 500× and (c) 3000× magnification.</p

Influence of temperature on total Cr biosorption capacity of CLB.

<p>[Temperature (°C): (✳) 15, (⬜) 28, (▼) 35, (○) 45; — pseudo-second-order model prediction]. CLB concentration: 1 g L^-1; pH = 1.5±0.1; initial Cr(VI) concentration = 100 mg L^-1.</p

Dependence of separation factor (a) and surface coverage (b) on initial Cr(VI) concentration.

<p>Dependence of separation factor (a) and surface coverage (b) on initial Cr(VI) concentration.</p

Comparison of maximum total Cr adsorption capacity predicted by the Langmuir model for various adsorbents.

<p>Comparison of maximum total Cr adsorption capacity predicted by the Langmuir model for various adsorbents.</p

Kinetic parameters of the Elovich, fractional power, pseudo-first-order and pseudo-second-order models for total Cr biosorption onto <i>Cupressus lusitanica</i> bark at different temperatures. Initial Cr(VI) concentration: 100 mg L^-1.

<p>Kinetic parameters of the Elovich, fractional power, pseudo-first-order and pseudo-second-order models for total Cr biosorption onto <i>Cupressus lusitanica</i> bark at different temperatures. Initial Cr(VI) concentration: 100 mg L^-1.</p