Browsing by Autor "Edwin Escalera"

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Adsorption of heavy metals on natural zeolites: A review
(Elsevier BV, 2023) Lisbania Velarde; Mohammad Sadegh Nabavi; Edwin Escalera; Marta‐Lena Antti; Farid Akhtar
Bolivian natural zeolite as a low-cost adsorbent for the adsorption of cadmium: Isotherms and kinetics
(Elsevier BV, 2024) Lisbania Velarde; Dariush Nikjoo; Edwin Escalera; Farid Akhtar
Population growth in recent years has led to increased wastewater production and pollution of water resources. This situation also heavily affects Bolivia, so wastewater treatment methods and materials suitable for Bolivian society should be explored. This study investigated the natural Bolivian Zeolite (BZ) and its NaCl-modified structure (NaBZ) as adsorbents for cadmium removal from water. The natural BZ and the modified form NaBZ were investigated by different physicochemical characterization techniques. Furthermore, XPS and FT-IR techniques were used to investigate the adsorption mechanisms. The cadmium adsorption on BZ and NaBZ was analyzed using various mathematical models, and the Langmuir model provided a better description of the experimental adsorption data with cadmium adsorption capacities of 20.2 and 25.6 mg/g for BZ and NaBZ, respectively. The adsorption followed the pseudo-second order kinetics. The effect of different parameters, such as initial cadmium concentration and pH on the adsorption was studied. In addition, the results of the regeneration test indicated that both BZ and NaBZ can be regenerated by using hydrochloric acid (HCl). Finally, the adsorption experiment of BZ and NaBZ on a real water sample (brine from Salar de Uyuni salt flat) containing a mixture of different heavy metals was carried out. The results obtained in this study demonstrate the effectiveness of natural BZ and modified NaBZ in the removal of heavy metals from wastewater.
High temperature phase evolution of Bolivian kaolinitic–illitic clays heated to 1250°C
(Elsevier BV, 2014) Edwin Escalera; Ragnar Tegman; Marta‐Lena Antti; Magnus Odén
Surfactant-Modified Bolivian Natural Zeolite for the Adsorption of Cr (VI) from Water
(Multidisciplinary Digital Publishing Institute, 2024) Lisbania Velarde; Edwin Escalera; Farid Akhtar
The present study reports the surfactant modification of Bolivian natural zeolite with hexadecyltrimethylammonium bromide (HTDMA-Br) for the adsorption of hexavalent chromium Cr (VI) anions from water. The surfactant-modified natural zeolite was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen adsorption/desorption isotherms, and Fourier-transform infrared spectroscopy (FTIR) to analyze the effect of its modification with HTDMA-Br and to verify its charge on the zeolite surface. We report a maximum adsorption capacity of 17 mg/g of Cr (VI) anions, surpassing the findings of some of the previous investigations on surfactant-modified natural zeolites of different geological origins. The analysis of the equilibrium data described the Cr (VI) anions adsorption by Langmuir isotherm and the pseudo second-order kinetic model. In addition, thermodynamics revealed an exothermic adsorption. Furthermore, anion exchange, electrostatic attraction, and chemical reduction were indicated to be dominating sorption mechanisms by X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) characterization techniques.
The production of porous brick material from diatomaceous earth and Brazil nut shell ash
(Elsevier BV, 2015) Edwin Escalera; Gustavo García; R. Terán; Ragnar Tegman; Marta‐Lena Antti; Magnus Odén