Francisco Rolando Valenzuela-Díaz

Brazilian organoclays as nanostructured sorbents of petroleum-derived hydrocarbons

Organophilic clays were prepared using a bentonite from the town of Boa Vista, state of Paraiba, Brazil, and a quaternary ammonium salt (Genamin CTAC-50). The materials obtained were characterized by X-ray diffraction and infrared spectroscopy. The results showed a good gasoline, toluene, diesel fuel and kerosene adsorbing capacity.

Modification of a Brazilian smectite clay with different quaternary ammonium salts

In this work, a smectite clay from the State of Paraiba, Brazil, was treated with six different types of ammonium salts, which is an usual method to enhance the affinity between the clay and polymer for the preparation of nanocomposites. The clays, before and after modification, were characterized by X ray diffraction. The conformation of the salts within the platelets of the clay depended on the number of long alkyl chains of the salt. The thermal stability of the clays was also studied. The ammonium salts thermal decomposition was explained in light of their position within the organoclays.

Synthesis and characterization of zeolite NaP using kaolin waste as a source of silicon and aluminum

The synthesis of zeolite NaP using kaolin waste, from the Amazon region, as a predominant source of silicon and aluminum has been studied. The zeolitisation process occurred in hydrothermal conditions using static autoclaving and the effects of time, temperature, and the Si/Al ratio were investigated. The starting material and the phases formed as reaction products were characterized by XRD, SEM and FTIR. The results showed that pure zeolite NaP is hydrothermally synthesized, at 100 °C for 20 hours, using metakaolin waste material in alkaline medium in presence of additional silica. The XRD and SEM analyses indicate that the synthesized zeolite presents good crystallinity.

Tannery waste solidification and stabilization

The stabilization/solidification of tannery waste containing chromium was studied as an option for its treatment and final disposal, by using a Portland cement type II and two different commercial bentonites (sodium and organophilic) as additives. Different compositions were evaluated by compressive strength analysis, porosity measurement, leaching tests and thermal analysis. The effect on the compressive strength is directly related to the resulting effect of the components present in the original paste on the hydration degree of the cement, which can be evaluated by thermogravimetric analysis from the dehydration steps of tobermorite and ettringite phases of the pastes. The results show that this process is suitable for the treatment of the tanning waste and that the best conditions of stabilization are obtained when both additives are used.

Synthesis of Zeolitic Materials Using as a Source of SiO2 and Al2O3 Calcined Kaolin Waste

This paper has as main objective synthesize zeolitic materials in hydrothermal conditions using as the predominant source of Si and Al a waste in powder generated from kaolin processing industries for paper-coating from the Brazilian Amazon region, thus transforming a material of low commercial value in another with higher added value, and can thus be used in future in adsorption and catalysis. For this were tested compositions of the mixture with different molar ratios of Na2O/Al2O3 and SiO2/Al2O3 considering the effects time-temperature of crystallization. The starting material and the phases formed as synthetic products were characterized by XRD, SEM and FTIR. The results show that the methodology developed with metakaolinite from a thermically activated kaolin waste at 700 º C for 2h reacting in alkaline medium in the presence of an additional source of silica, zeolitic phases were obtained with structure FAU-type and GIS-type in the samples synthesized.

Comparative Study of Organophilic Clays to be Used in the Gas & Petrol Industry

Brasgel clay and Gray clay has been been subjected to modification through ion-exchange reaction by quaternary ammonium (cetyltrimethyl ammonium bromide, CTAB). The samples were studied by X-Ray Diffraction, Infrared Spectroscopy, Scanning Electron Microscopy (SEM) and the Foster’s Swelling test. The results indicated that the quaternary ammonium salts were intercalated between the layers of clay. The basal spacing of unmodified Brasgel clay, determined by XRD, was 1.329 nm and after modification it increased up to 2.101 nm. By analyzing the results obtained in this study, particularly those provided by infrared spectroscopy, it was concluded that the treated, organophilic sample (modified with CTAB) comprised CH2 and CH3 groups in its structure, which provides evidence of the efficiency of the organophilization process. Foster´s swelling was carried out with and without agitation in gasoline, diesel, toluene and lubricating oil. The results indicated the samples was organophilic materials, with improved efficiency of Brasgel clay in gasoline and diesel and when compared to Gray clay in the test of capacity for adsorption and Foster´s swelling, the results were similar to kerosene and lubricating oil.

Synthesis and characterization of modified clays as sorbents of toluene and xylene

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.

Nanocomposite Microcapsules from Powders of Polyhydroxybutyrate (PHB) and Smectite Clays

Drug delivery systems involving microcapsules provide an attractive way to improve the performance of many chemical and biological substances. These systems may be used for several industrial segments, especially medical, pharmaceuticals and cosmetics. PHB is a polyhydroxyalkanoate available in powder form, biocompatible, biodegradable and inert towards animal tissues. The obtained PHB/smectite clay nanocomposite improved the physical-chemical properties of PHB, including its biodegradability. In this work, we describe the preparation of microcapsules from two nanocomposites systems: a) PHB and Cloisite 20A organoclay (PHB1) and b) PHB and natural Brazilian green policationic clay (PHB2). When analyzed by XRD, the films and microcapsules did not show a d(001) peak, demonstrating an exfoliated structure for the nanocomposites. The films have shown by SEM an homogeneous distribution with the clay mineral particles spread homogeneously by the PHB film. The new microcapsules/nanocomposites showed an “hydrangea” morphology. The diameter of the microcapsules was variable between 0.5-15 µm.

Preparation, Physical and Mechanical Characterization of Montmorillonite/polyethylene Nanocomposites

In this paper, we report the preparation of polyethylene composites with organically modified montmorillonite. Three different Na+-montmorillonites were modified in order to obtain organoclays and two grades of high-density polyethylene were used as composite matrices. All composites were prepared by melt blending, and their physical and mechanical properties were thoroughly characterized. The extent of clay platelet exfoliation in the composites was confirmed by X-ray diffraction (XRD). Mechanical properties under static and impact conditions were evaluated to assess the influence of the reinforcement on the properties of polyethylene.

Characterization and Adsorption of Phenol by Organophilic Clays

Nowadays, increasing concern about pollution of groundwater by organic chemicals led to research on the use of various adsorbents. They can be applied to provide a barrier to the escape of organic contaminants from storage tanks and stabilization lagoons. This study investigated, experimentally, the adsorption of phenol by six organoclays, using phenol in aqueous solution. This is the way that wastewater is discharged. The organoclays were prepared with two different clays, a bentonite from the Brazilian State of Paraiba (SVC), sodium exchanged in laboratory and a Wyoming, bentonite (SWy) with three Brazilian quaternary ammonium salts. The cations exchanged were dialkyl dimethyl with the alkyls groups dodecyl (DADM), distearyl dimethyl (DSDM) and octadecyl trimethyl (ODTM). Through this technique the hydrophilic character is transformed into hydrophobic. Adsorption of phenol followed the order of ODTM-SVC > DADM-SVC > DSDM-SVC > DADM-SWy > DSDM-SWy > ODTM-SWy. Isotherms for DSDM-SVC, DSDM-SWy, DADM-SVC, DADMA-SWy, ODTM-SVC and ODTM-SWy followed a convex up pattern. The equilibrium curves obtained are well represented by the Freundlich isotherm model. The adsorption data showed that the prepared materials were effective to adsorb phenol, being the Brazilian clay the most efficient of the three materials.