Priscila F. de Sales

Adsorption of etheramine on kaolinite: A cheap alternative for the treatment of mining effluents

The results of laboratory experiments aimed at determining the influence of physicochemical parameters on the adsorption of etheramine (adsorbate) on white, pink and yellow kaolinites (adsorbent) are presented. The adsorption of etheramine was favoured at pH 10.0 under conditions where the initial concentration of etheramine was 200 mg l(-1) and the ratio of adsorbent to volume of etheramine solution was 1:100 g ml(-1). Equilibrium adsorption was attained within 30 min and the efficiencies of removal of etheramine by white, pink and yellow kaolinite were 77%, 80% and 69%, respectively. The adsorption isotherms of the kaolinites were determined under optimum conditions and with adsorbate in the concentration range of 0-4000 mg l(-1). The amounts of etheramine adsorbed per unit mass of adsorbent were 33.03, 34.32 and 23.11 mg g(-1) for white, pink and yellow kaolinites, respectively. The adsorption of etheramine on kaolinites was better fitted to the Langmuir rather than the Freundlich isotherm, and could be explained by a pseudo-second-order kinetic model. It is concluded that kaolinites offer significant potential in the treatment of effluents originating from the processing of lower grade iron ores by froth flotation.

Study of chemical and thermal treatment of kaolinite and its influence on the removal of contaminants from mining effluents

The effects of chemical and thermal treatments on the structure of kaolinite were examined, as well as the influence of those changes upon the removal of etheramine, a cationic collector used in the processing of iron ore. The materials were characterized using XRD, XRF, specific surface area (SBET), FTIR, zeta potential and a test for determination of acid sites. The effects of the treatments on the structure of kaolinite were evaluated using chemometric tools developed from principal components analysis algorithms and hierarchical components analysis. The parameters evaluated in the kinetic study of adsorption were contact time, initial concentration of etheramine, quantity of adsorbent and pH. The adsorption of etheramine in the samples subjected to chemical treatments could be explained by a pseudo-second order model, whilst for the sample subjected to thermal treatment, better fit was with the pseudo-first order model. With regard to adsorption isotherms, it was shown that for the three adsorbents used, adsorption followed the Langmuir model. The maximum quantities adsorbed were 27 mg g(-1), 29 mg g(-1) and 59 mg g(-1), respectively, for the samples subjected to acid, thermal and peroxide treatments. The treatment with peroxide was found to be the most suitable for removal of etheramine.

Comparative analysis of tropaeolin adsorption onto raw and acid- treated kaolinite: Optimization by Response Surface Methodology

The comparative adsorption of Tropaeolin (TP) onto raw kaolinite (RK) and kaolinite submitted to acid treatment (AK) was studied. RK and AK were characterized by zeta potential and energy dispersive X-ray spectroscopy (EDS). The adsorption was investigated using Composite Central Design (CCD) and the parameters evaluated were initial TP solution concentration, quantity of adsorbent and the pH of the solution. The optimized parameters were: initial TP solution concentration of 75 mg L(-1), pH 4 and 0.12 g adsorbent. Kinetic data were evaluated by pseudo-first order, pseudo-second order and Avrami models. The equilibrium adsorption was analyzed by Langmuir, Freundlich and Sips isotherms. The kinetic data were best fitted to the pseudo-second order model. The Sips isotherm model gives the better correlation to predict the adsorption equilibrium. The maximum adsorption capacities were 18.3 mg g(-1) and 23.2 mg g(-1) for RK and AK, respectively. The calculated thermodynamic parameters showed that the process was spontaneous, endothermic and involving the disorganization of the adsorption system for both adsorbents. The desorption step showed that the AK sample was more suitable as an adsorbent.

Development and comparative analysis of single-drop and solid-phase microextraction techniques in the residual determination of 2-phenoxyethanol in fish

Solid-phase microextraction (SPME) and single-drop microextraction (SDME) in headspace mode, were used in the residual determination of the anesthetic 2-phenoxyethanol in fish fillets, to ensure food safety. For the optimization of the methodologies the experimental central composite design (CCD) was used, resulting in accurate evaluations with less amount of analysis. The developed methodologies presented good precision in the evaluated range, o limits of detection (LD) and quantification (LQ) for SDME were 0.2 and 0.62 μg mL-1 and for SPME were 0.18 and 0.56 μg mL-1, respectively. In the analyzed samples the determined elimination time of post-anesthesia 2-phenoxyethanol was 12 h for the SDME and 24 h for the SPME, at the anesthesia concentrations evaluated (450-1050 μg mL-1). The two techniques presented viability of application for the residual determination of 2-phenoxyethanol in fish, SPME being more sensitive and automated and SDME with lower operation cost.

Production, Characterization and Application of Activated Carbon Obtained from the Corncob: The Search for the Reuse of an Agroindustrial Waste

The production, characterization and application of activated carbon obtained from corncobs as an adsorbent was studied. Fresh material was submitted to thermal analysis (TG-DTA), and the carbon obtained from chemical activation was characterized by specific surface area (SBET), distribution of pore size (DFT), Scanning Electron Microscopy (SEM) and Infrared spectroscopy with Fourier transform (FT-IR). The adsorption of orange dye (OG) and methylene blue (MB) proved that data from isothermal adsorption were better adjusted to the Sips model. The maximum quantities, 86 mg g and 124 mg g, were obtained respectively for the adsorption of the dyes Orange G (OG) and Methylene Blue (MB). The results allow to conclude that the chemical activation of corncobs was responsible for the production of material, which is adequate to be applied as an adsorbent, enabling reuse of this agroindustrial residue.