Removal of Al (III) and Fe (III) from binary system and industrial effluent using chitosan films.

Adsorption of Al (III) and Fe (III) onto chitosan films from individual and binary systems were investigated. The matrix effect was evaluated using an industrial effluent of the scrubber of gases from the production process of Al2(SO4)3. The adsorption study was carried out by response surface methodology to optimize the adsorption operation as a function of pH (3, 4.5 and 6) and film dosage (FD) (100, 200 and 300 mg L-1).The possible interactions film-ions were investigated by thermal analysis, X-ray diffraction, scanning electron microscopy and dispersive energy X-ray spectroscopy. The more suitable conditions for all experimental designs were the FD values in 100 mg L-1and pH 4.5.The adsorption capacity of Fe (III) in the individual and binary systems were 140.2 mg g-1 and 132.3 mg g-1 respectively; however, in the experiment conducted on the real effluent, the adsorption capacity was reduced to 66.30 mg g-1.Already to Al (III), the adsorption capacities in the individual and binary systems were 665.5 mg g-1 to 621.2 mg g-1 respectively, and when the operation was performed using real effluent the adsorption capacity was reduced to 275.7 mg g-1.

Chitosan scaffold as an alternative adsorbent for the removal of hazardous food dyes from aqueous solutions.

HYPOTHESIS: The dye adsorption with chitosan is considered an eco-friendly alternative technology in relation to the existing water treatment technologies. However, the application of chitosan for dyes removal is limited, due to its low surface area and porosity. Then we prepared a chitosan scaffold with a megaporous structure as an alternative adsorbent to remove food dyes from solutions. EXPERIMENTS: The chitosan scaffold was characterized by infrared spectroscopy, scanning electron microscopy and structural characteristics. The potential of chitosan scaffold to remove five food dyes from solutions was investigated by equilibrium isotherms and thermodynamic study. The scaffold-dyes interactions were elucidated, and desorption studies were carried out. FINDINGS: The chitosan scaffold presented pore sizes from 50 to 200 µm, porosity of 92.2±1.2% and specific surface area of 1135±2 m(2) g(-1). The two-step Langmuir model was suitable to represent the equilibrium data. The adsorption was spontaneous, favorable, exothermic and enthalpy-controlled process. Electrostatic interactions occurred between chitosan scaffold and dyes. Desorption was possible with NaOH solution (0.10 mol L(-1)). The chitosan megaporous scaffold showed good structural characteristics and high adsorption capacities (788-3316 mg g(-1)).

Biosorption of phenol onto bionanoparticles from Spirulina sp. LEB 18.

The biosorption of phenol onto bionanoparticles from Spirulina sp. LEB 18 was studied. Firstly, the bionanoparticles were prepared from Spirulina sp. strain LEB 18 and characterized. After, response surface methodology was employed to optimize the biosorption process as a function of pH (3.2-8.8) and bionanoparticles dosage (0.15-1.85 g L(-1)). Finally, equilibrium and thermodynamic studies were performed at different temperatures (298-328 K). The bionanoparticles presented hydrodynamic diameter of 232±3 nm and polydispersity index of 0.150. It was found that the more adequate condition for the phenol biosorption was pH of 6.0 and bionanoparticles dosage of 1.85 g L(-1). The Langmuir model presented satisfactory fit with the equilibrium experimental data. The maximum biosorption capacity was 159.33 mg g(-1), obtained at 298 K. The thermodynamic parameters showed that the biosorption was a spontaneous, favorable and exothermic process. Based on these results, it can be affirmed that the bionanoparticles are an alternative, renewable and eco-friendly biosorbent to removal phenol from aqueous solutions.

Statistical optimization, interaction analysis and desorption studies for the azo dyes adsorption onto chitosan films.

Chitosan films (CF) were applied to remove azo dyes (tartrazine and amaranth) from aqueous solutions by adsorption. CF were prepared by casting technique and characterized. Response surface methodology was employed to optimize the adsorption process as a function of pH (2, 3 and 4) and CF concentration (100, 150 and 200 mg L(-1)). The possible interactions CF-dyes were investigated by Fourier transform infrared spectroscopy, dispersive energy X-ray spectroscopy, thermogravimetric analysis and color parameters. Adsorption-desorption cycles were also performed. The more appropriate conditions for the adsorption of both dyes were pH of 2 and CF concentration of 100 mg L(-1). Under these conditions, the tartrazine and amaranth adsorption capacities were 413.8 and 278.3 mg g(-1), respectively. The interactions between the CF protonated amino groups and anionic form of the dyes at pH 2 were confirmed. Desorption experiments showed that the CF can keep its adsorption capacity maximum for two cycles.