Papers by Author: Pedro M. Büchler

Abstract: This paper presents a study of a stabilization/solidification (S/S) process of a tannery waste containing chromium. In this process a mixture of cement, water and the waste is solidified during hydration of the former. Stabilization occurs by the reaction of the chromium components of the waste with the calcium hydroxide formed during the process. A rigid block is obtained with low hazardous of contamination of soil and groundwater after its disposal into industrial landfill. Mixtures were prepared adding dried tannery waste in 10, 15 and 20% of the Portland cement mass. Sodium bentonite and organoclays in 5 % of cement mass were used as additives. Solidified specimens were analyzed after 28 days of hydration time by solid-state 29Si nuclear magnetic resonance (NMR) spectroscopy and unconfined compressive strength analysis. The increase of tannery waste content and the presence of the additives reduce silica polymerization as well as the mechanical strength of the solidified bodies.

Abstract: This paper reports an investigation on the effect of thermal activation of kaolinite. It is well known that during calcinations (400–650°C), kaolinite loses the OH lattice water and is transformed into metakaolinite or amorphous material. Arsenic is trace element that is toxic to animals including humans. The adsorption of arsenic on kaolinite was investigated at varying pH and thermal pretreatment. Calcination of sample is carried out at 650 °C for 3 h. The decomposition of kaolinite is recorded using methods of thermal analysis. The resultant product is identified by XRD. Laboratory experiments were conducted examining the effect of arsenic by thermally modified kaolinite. The Langmuir isotherm was used to describe arsenite and arsenate sorption by the calcined kaolinite. The equilibrium parameters used were based on experimental data obtained for the dynamic adsorption process of arsenic. Removal of arsenate using natural kaolinite was satisfactory, whereas arsenic was not removed by adsorption with thermally modified kaolinite. Moreover, the adsorption of arsenic by kaolinite and metakaolinite decreases with increasing pH.

Abstract: Municipal sludge waste combustion was studied by thermogravimetry (TG) and differential thermal analysis (DTA), to better understand the two main stages which occur during the combustion process, and to evaluate how much of the total and significant generated heat is released is during each combustion stage. A method to measure the lower heating value (LHV) on a dried basis was developed from the TG/DTA data and it was applied to the whole process and to each combustion stage. Chemical analysis of the residual products after each step shows that nitrogen organic compounds are burnt only from 350°C to 550°C, and that the organics which are released and burnt in the previous step, which begins by 150°C, present a heating value of about 32MJ/kg. The nitrogen containing compounds present a lower LHV.

Abstract: This study shows a possibility of using sewage sludge after thermal treatment (at 1050°C for 3h) in the production of a building material. The use of dehydrated sewage sludge as a component in building materials, like in the sludge-clay mixture employed in the manufacture of bricks, tiles and cements, has been frequently done around the world. During sludge-clay mixture firing, which was done by controlled heating at a temperature above of 1000°C for 3h, organic substances of the sludge were completely eliminated. After thermal treatment, the micropores formed due to the released expansive gases, are responsible for the acoustic and thermal isolation properties of the resulting material. A problem found in the ashes was the high concentration of toxic compounds like Zn, Ni, Cr, Cu, Al oxides. The aim of the present work was to observe through scanning electron microscopy (SEM), X-ray fluorescence (XRF) and inductively coupled plasma optical emission spectrometer (ICP-OES) the integration of these oxides into the sintered ceramic matrix of sludge. Oxide integration is an important factor in brick manufacturing used as building materials.

Abstract: The aim of this paper was to study the characterization of sludge affected by different thermal treatment, on selected physical and chemical properties. Sludge incinerated ash has been fired at different temperatures. This material was fired at 1050 °C for 3 h and until a peak of 1010°C. After thermal treatment the ash were screened at 200 mesh. The ash was characterized by X-ray fluorescence and trace elements like Cr, Pb, Zn, Cu, and some oxides like quartz(SiO2), Al2O3, P2O5, Fe2O3 were found. Scanning electron microscopy (SEM) has shown one change of particle between 2μm at 90μm and apparent porosity.

Abstract: The leather industry creates a large quantity of organic and inorganic waste containing chromium. This research examines stabilization of particulate tannery waste in type II Portland cement. Several clays, Brazilian polycationic smectite modified in laboratory and commercial clays were used as additives with the aim of optimizing chromium adsorption. Tannery waste was added in quantities of 10, 15 and 20% relative to cement mass. The solidification components were analyzed separately and in combination in the solidified mixes using X ray diffraction. The analysis showed that reactions between the waste and the cement occurred, and that the tannery waste modified the final compounds of the system. Calcium sulfate present in the waste increased ettringite formation. Chromium also reacted with cement, since compounds with chromium and calcium were identified. Substitution of aluminum and silicon by chromium was also observed.

Abstract: Disposal or reuse of hazardous waste is a major consideration in chemical manufacturing and processing. Waste residuals from the tannery industry can contain high levels of chromium. Considered as a hazardous waste by the Brazilian environmental laws, the chromium-containing waste requires treatment before final disposal. This paper proposes a solution for the disposal of tannery wastes, which are rich in chromium by solidification in a Portland cement matrix using combinations of sodium bentonite and organoclay admixtures. This research is part of a series of experimental studies where Brazilian sodium bentonite, and organoclay materials are used to adsorb both inorganic and organic chromium. The solidified matrix is formed by Type II Portland cement, in which the hydration process stabilizes the tannery waste. Wyoming sodium bentonite and a commercial organoclay are analyzed and compared with the Brazilian clays. X-ray Diffraction is used to characterize the samples and leaching tests are performed to analyze the chromium concentration in the extract solution. In terms of leachate tests, the stabilization by solidification with cement is a process that can be used in the treatment of tannery waste.

Abstract: Benzene, toluene, ethylbenzene, and the xylenes (BTEX) are the major water-soluble constituents of gasoline that may contaminate soils and natural waters, which can be sorbed by organoclays. This study investigates the sorption of toluene and xylene by organoclays produced from Brazilian bentonite (SVC) and from Wyoming bentonite (SSA) with hexadecyltrimethylammonium (HDTMA), as well as by a commercial organoclay (SCo). The organoclays were characterized by X-Ray Diffraction, Differential Thermal Analysis, Thermogravimetry. Isothermal sorption were performed. The efficiencies of the organoclays on removing toluene increased in the order: SVC-HDTMA < SSA-HDTMA < SCo. The xylene sorption by SVC-HDTMA and SSA-HDTMA organoclays was about two times higher than by the SCo. These organoclays may be used as permeable reactive barriers or in ceramic filters for petroleum waste-water treatment systems.