Nano-Mg/Al hydrotalcite: Physicochemical Characterization and Removal of As(III) from Aqueous solutions
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Nano-Mg/Al hydrotalcite: Physicochemical Characterization and Removal of As(III) from Aqueous solutions E. Ramos-Ramírez1, N. L. Gutiérrez-Ortega2, G. Rangel-Porras1, G. Herrera-Pérez3 1
Departamento de Química, División de Ciencias Naturales y Exactas de la Universidad de Guanajuato, Noria Alta s/n, Col. Noria Alta, C.P.36050, Guanajuato, Gto., México. 2 Departamento de Ingeniería Civil, División de Ingenierías de la Universidad de Guanajuato, Juarez No. 77, Col. Centro, C.P.36000, Guanajuato, Gto., México. 3 Departamento de Ingeniería en Materiales, Instituto Tecnológico Superior de Irapuato, Carretera Irapuato-Silao km 12.5, Irapuato, Gto., México. Email: [email protected]
ABSTRACT Arsenic is one of the most toxic elements that can be found. Arsenic is mainly emitted by the copper, lead and zinc production, in agriculture as pesticides and herbicides. Two forms of arsenic are common in natural waters: arsenite (AsO33−) and arseniate (AsO43−), referred to as As(III) and As(V). The nano-Mg/Al-hydrotalcites present ionic exchange and adsorbent capacities. In this work, the physic-chemical characterization of nano-Mg/Alhydrotalcites and his arsenic removal capacityis described. The solids were synthesized by the sol-gel method with Mg/Al=2 and 3 ratio. The solids and their thermal treated products were characterized by XRD, FTIR, DTA, TGA and N2 adsorption. The solids were used as adsorbents As(III) in aqueous solutions. Adsorption isotherm studies of As(III) from aqueous solution are described. The adsorbent capacity was determined using the Langmuir, Freundlich and Dubinin–Radushkevich adsorption isotherm models. The As(III) adsorption isotherm data fit best to the isotherm Freundlich model. The maximum As(III) uptake capacity by nano-Mg/Al-hydrotalcites and the heated solids were determined using the Freundlich equation and were found to 547.46, 660.15, 799.88 and 739.12 mg As(III)/g HTMg/Al=2, HT-Mg/Al=3, HT-Mg/Al=2 at 350°C and HT-Mg/Al=3 at 350°C respectively. In the kinetic studies using 40 mg/L concentration of As(III) solutions was obtained an excellent removal capacity in contact times less at one minute. Keywords: As, Sol–gel, Adsorption, Kinetics. INTRODUCTION There are many water contaminants that can enter in drinking water naturally or through human activities. Contamination of drinking water due to industrial pollution is a major concern in modern society. Contamination occurs from natural decomposition of minerals, and chemical products of antropogenic origin. Arsenic is one of the most common anionic water pollutants and possesses a serious health risk in many countries of the world. In water, it may appear in both organic and inorganic forms indifferent oxidation states. Environmental forms include arsenites, arsenates, arsenious acids, arsenic acids, methyl arsenic acid, dimethyl arsinic acid, arsine, etc. Inorganic forms of arsenic such as As(III) and As(V) are the most harmful to human health. As(III) is significantly more toxicand mobile than As(V) [1]. Arsenic is one of the most toxic elements
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