Use of Iron Ore Tailing as Raw Material for Two Products: Sodium Silicate and Geopolymers

Abstract

In this work, iron ore tailing (IOT) was used for the production of two different materials: sodium silicate and geopolymers. Initially, reactions of IOT with NaOH were carried out by hydrothermal reaction in autoclave at 200 °C (1:1.5 and 1:2.5 SiO2:NaOH molar ratio) and reaction times of 4 and 8 h. X-ray fluorescence by dispersive energy (XRF), X-ray diffraction (XRD), Mössbauer spectroscopy, scanning electron microscopy (SEM-EDS) and titrations showed that IOT:NaOH ratios of 1:2.5 and reaction time 8 h completely dissolved the quartz from the IOT, obtaining a solid fraction consisting mainly of hematite and an aqueous phase of sodium silicate, which showed contents of ca. 23% SiO2 and 19% Na2O. This sodium silicate obtained was then combined with IOT (25 and 50 wt.%) to produce geopolimeric material with excellent physicochemical properties, fast curing time and very good compressive strength results, which ranged from 41 to 58 MPa and many potential applications.

Reuse of iron ore tailing to potassium silicate synthesis and to the production of geopolymers

“…Dissolution was studied by varying the reaction time (24, 48 and 72 h), the temperature (20, 75 and 90 °C) and the liquid–solid ratio used. Optimized temperature and reaction time conditions were 75 °C for 48 h. In the work developed by Prates et al , 10 sodium silicate was produced from the dissolution of silica present in iron ore tailings by a hydrothermal process. The reaction carried out at 200 °C for 8 hours dissolved all the silica present in the IOT, obtaining an aqueous fraction of sodium silicate that showed contents of ca.…”

“…Two different synthesis routes were used to produce potassium silicate from IOT, namely, the hydrothermal route (HR) and the solid route (SR). The methodology via the hydrothermal route was carried out by adapting the synthesis models proposed by Ismail et al, 25 Lu et al, 26 and Prates et al 10 The solid route was adapted from the work carried out by Vogt and Lameiras. 16 For the hydrothermal route (HR), 12 g of IOT were mixed with 15 g of potassium hydroxide (KOH) and 30 g of distilled water.…”

“…One of the numerous applications of K 2 SiO 3 , which has gained much prominence in recent years, is its use as an activator solution (AS) to produce geopolymers. 10,11 Therefore, in this work, solid potassium silicate SR18-3 h was the material used for the synthesis of geopolymers due to its higher silica content.…”

“…9 Moreover, due to its composition, different studies have incorporated iron ore tailings into the precursor matrix of geopolymers. 10,11 Geopolymers, also called alkali-activated materials, are produced from the alkaline activation of precursors rich in aluminosilicates. This activation can be defined as a process in which a material, generally amorphous and rich in silica and alumina, reacts with an alkaline activator solution, giving rise to a product capable of agglomerating and hardening.…”

“…17–19 In addition, several studies have addressed the use of iron ore tailings in the production of geopolymers and, in most cases, as a filler in the geopolymer matrix. 20,21 In the research developed by Prates et al , 10 iron ore tailings were used to produce sodium silicate by a hydrothermal process. The sodium silicate obtained was then combined with iron waste, which was used as a filler, to produce geopolymeric materials with high compressive strength, fast curing time and excellent physicochemical properties.…”