Maria Lúcia Pereira Antunes

Adsorption of reactive dye on seawater-neutralised bauxite refinery residue.

This investigation has demonstrated the need for thermal treatment of seawater neutralised red mud (SWRM) in order to obtain reasonable adsorption of Reactive Blue dye 19 (RB 19). Thermal treatment results in a greater surface area, which results in an increased adsorption capacity due to more available adsorption sites. Adsorption of RB 19 has been found to be best achieved in acidic conditions using SWNRM400 (heated to 400°C) with an adsorption capacity of 416.7 mg/g compared to 250.0mg/g for untreated SWNRM. Kinetic studies indicate a pseudosecond-order reaction mechanism is responsible for the adsorption of RB 19 using SWNRM, which indicates adsorption occurs by electrostatic interactions.

Composição química das águas pluviais e deposição atmosférica anual na bacia do Alto Sorocaba (SP)

Two sampling points were chosen and forty samples were collected between January and December 2006 at Alto Sorocaba basin. The rainwater pH varied from 5.46 to 6.36 (Ibiuna) and 5.26 to 6.81 (Itupararanga), being Ca2+ the main ion responsible for controlling the rainwater pH. The ionic concentrations decreased in the following order: Ca2 +>Na+> Mg2+>K+ for cations and SO42->HCO3->NO 3->Cl- >PO43- for anions. The annual atmospheric deposition appeared to be controlled mostly by following sources: mining activities and cement factories (Ca2+ and HCO3-), natural soil dust (Na+, Mg2+ and HCO3-), fossil fuel burning (SO42-) and agriculture activities (K+, NO3- and PO43-).

Estudo da labilidade de Cu(II), Cd(II), Mn(II) e Ni(II) em substâncias húmicas aquáticas utilizando-se membranas celulósicas organomodificadas

In this work commercial filters papers were organomodified with tetraethylorthosilicate (TEOS) and 3-aminopropyltriethoxysilane (3-APTS), aiming at the development of a new analytical procedure for in-situ speciation of labile and inert metal species in aquatic systems. Parameters that exert influence on the metal lability such as pH, chelating time, concentration and characteristics of the organic matter were studied in the laboratory using tests for metal recuperation. The results showed slower kinetics for Cu ion than for Ni, Mn and Cd in the absence of aquatic humic substances (AHS). The relative lability observed for complexed metals in aquatic humic substances using organomodified filter papers was Cu>>Cd>Ni>Mn. The pH values, structural characteristics and concentration of AHS exert strong influence on the lability of the metals. The results obtained showed that the utilization of organomodified filter papers can be an interesting and promising alternative for in situ characterization of metal lability in aquatic systems.

Adsorção do corante Reativo Azul 19 em solução aquosa por lama vermelha tratada quimicamente com peróxido de hidrogênio

Adsorption of Reactive Blue 19 dye onto activated red mud was investigated. Red mud was treated with hydrogen peroxide (LVQ) and heated at both 400 oC (LVQ400) and 500 oC (LVQ500). These samples were characterized by pH, specific surface area, point of zero charge and mineralogical composition. Adsorption was found to be significantly dependent on solution pH, with acidic conditions proving to be the most favorable. The adsorption followed pseudo-second-order kinetics. The Langmuir isotherm was the most appropriate to describe the phenomenon of dye removal using LVQ, LVQ400 and LVQ500, with maximum adsorption capacity of 384.62, 357.14 and 454.54 mg g-1, respectively.

Removal of reactive dye from aqueous solution using thermally treated red mud

AbstractThe removal of color from wastewater is a major problem for textile industries. The best option to remove color is to combine conventional treatments with additional processes, such as adsorption. Industrial waste has been studied for use as adsorbents, specifically red mud (RM), which is an insoluble residue that is generated in large quantities during the processing of bauxite. In this study, a typical reactive dye, reactive blue 19 dye (RB 19), used in the textile industry was selected, and its ability to adsorb RM that was thermally treated at 500°C (RM 500°C) was evaluated. The adsorption of RB 19 was highest when the pH values were lower than the pHPCZ (7.0). The experimental adsorption capacity data were analyzed using the Langmuir and Freundlich models. The Langmuir model was more appropriate for describing this phenomenon in acidic conditions, with a maximum adsorption capacity of 178.4 mg g−1 (R2 of 0.84). Kinetics studies indicate that a pseudo-second-order reaction mechanism is respons...

Thin Films Produced on 5052 Aluminum Alloy by Plasma Electrolytic Oxydation with Red Mud-containing Electrolytes

In this paper, we propose the production of ceramic protective thin films by plasma electrolytic oxidation using red mud-containing electrolytes. The treatments were performed through the application of pulsed voltage (600 V, 200 Hz) during 300 seconds to aluminum samples immersed in electrolytic solutions with 5 g of red mud per liter of distilled water. The coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS) and contact angle and surface energy measurements. The final current density during the experiments was 0.05 A/cm2 and films as thick as 9.0 µm have been obtained. XRD patterns have clearly shown the incorporation of species from the red mud on the coating.

Adsorption of Cd2+, Ni2+ and Zn2+ in aqueous solutions using anhydrite and red mud

ABSTRACT Various minerals and industrial waste have been studied for use as an adsorbent, in particular the anhydrite and the red mud. The red mud is an insoluble residue that is generated in large quantities during the processing of bauxite. The anhydrite is a calcium sulfate (CaSO4), crystallized as a rhombic way, and used as raw material in the industry. In this study, the Cd2+, Ni2+ and Zn2+adsorption capacity by anhydrite and by red mud was evaluated using adsorption isotherms obtained by the Langmuir and Freundlich models. The materials used showed adsorption ≥75±1% for all metals in aqueous solutions with a concentration of 0.5 mmol.25 mL-1. The Langmuir isotherm was more appropriate to describe the phenomenon of Cd2+, Ni2+ and Zn2+ removal, with highest adsorption capacity at 0.47 and 0.51 mmol.g-1 for Cd2+, 1.18 and 1.56 mmol.g-1 for Ni2+, and 0.84 and 1.47 mmol.g-1 for Zn2+, respectively. These values were higher than those ones obtained for other materials described in previous studies.

X-Ray Image Comparison of Wind Turbine Blade Waste and EPS Waste Used as Aggregates in Portland Cement Concrete

Transforming industrial wastes into construction materials through recycling is a feasible alternative that contributes to reduce the consumption of natural resources. Besides, modern civil construction seeks strong lightweight building materials. Due to their low density, wind turbine blade manufacturing waste and EPS post-consumer packaging can be used for this purpose. Such work uses X-ray imaging to evaluate the spatial distribution of these wastes in Portland cement concrete. Test specimens were produced containing wind turbine blade waste replacing part of the gravel content, and EPS waste replacing part of the sand content. X-ray images of the test specimens reveal that the waste is distributed homogeneously in the matrix. Furthermore, the mechanical strength of these test specimens meets the requirements of the Brazilian technical standards for non-load bearing concrete blocks.

Feasibility of RF Sputtering and PIIID for production of thin films from red mud

. Brazil produces a third of the world’s bauxite, being surpassed only by Australia and China. The production of aluminum begins with the extraction of alumina from bauxite ore via the Bayer process, followed by its electrolytic reduction to metallic aluminium. The Bayer process separates aluminum oxides/hydroxides from iron, titanium and silicon oxide/hydroxide species present in bauxite, using a highly caustic solution of sodium hydroxide at elevated temperatures and pressures. During this process, the waste components of the bauxite ore are separated, generating an insoluble residue called Red Mud

Crystallization of nordstrandite in ethylene glycol / water solutions: electron microscopic studies

The present work shows the growth of nordstrandite microcrystals observed by transmission and scanning electron microscopy. Nordstrandite was synthesised from non-crystalline aluminium hydroxide reacted in 20% ethylene glycol/water solution, at room temperature. This material was characterized by TEM, SEM, SAED, XRD and EDS/TEM, during six month and revealed the formation and growth of nordstrandite. Fibrillar pseudoboehmite is the only aluminium hydroxide which could be identified during the first two weeks. The nuclei grow, from complete dissolution/recrystallization of pseudoboehmite fibrils, into platy rectangular microscrystals of nordstrandite. Some tabular microcrystals recrystallise, forming after six months only the multi-point nordstrandite stars. This electron-optical study suggest that the star shape results from the overlapping of rectangular plates, and pseudoboehmite fibrils act as the precursor of nordstrandite crystallisation in ethylene glycol/water solution.