Increased As Adsorption on Maghemite-Containing Red Mud Prepared by the Alkali Fusion-Leaching Method

Andrei Shoppert,Denis Rogozhnikov,Irina Loginova,Kirill Karimov,Leonid Chaikin

doi:10.3390/min9010060

Abstract

This study investigates the use of red muds as adsorbents for As (V) removal. Red mud is a waste that contains a large amount of iron oxides and hydroxides, which are excellent adsorbents of arsenic, especially those possessing magnetic properties and a large specific surface area. The purpose of the experiments was to study the possibility of obtaining an effective adsorbent by the direct extraction of alumina from bauxite using the caustic alkali fusion method and to compare the arsenic removal effectiveness and other properties of these red muds with industrial samples. Red muds were described using methods such as X-ray diffraction spectrometry (XRD), X-ray fluorescence spectrometry (XRF), SEM, vibrating sample magnetometry (VSM), and the Brunauer–Emmett–Teller (BET) method. The main iron-containing phase of the red muds obtained by fusing bauxite with caustic alkali is maghemite, which has a large specific surface area. The specific surface area of the obtained samples varied in the range of 6.1–54.9 m2/g. Arsenic adsorption experiments were carried out using five different types of red muds: industrial Bayer, industrial sintering, and red mud obtained through bauxite alkali fusion at 300, 500, and 700 °C. The red muds obtained by fusing bauxite with caustic alkali at 300 and 500 °C had the highest effectiveness removing arsenic; their As(V) uptake capacity was over 30 mg/g.

Highlights

Red mud is a technogenic waste produced by the alkaline processing of bauxite into alumina using Bayer or sintering methods [1,2,3,4]
Most plants dispose of red mud in bauxite residue disposal areas as pulp, with the pH of the pulp reaching 13 units due to the caustic alkali used for processing
This paper proposes a red mud production method based on fusing bauxites with caustic alkali, as shown in our previous works and the works of other authors [61,62,63,64,65]

Summary

Introduction

Red mud is a technogenic waste produced by the alkaline processing of bauxite into alumina using Bayer or sintering methods [1,2,3,4]. Special chemical composition, and high pH, red mud causes great damage to the environment at the disposal sites. This was very clearly demonstrated by the environmental disasters that occurred in Eastern Europe over the past decades [7,8], which even resulted in human deaths, not to mention environmental damage. This makes red mud processing a challenge for the aluminum industry, which has yet to find a way to avoid its accumulation

Methods

Results

Conclusion