Phosphate removal from aqueous solutions using red mud wasted in bauxite Bayer's process

ELSEVIER Resources, Conservation and Recycling 19 (1997) 11 20

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Phosphate removal from aqueous solutions using

red mud wasted in bauxite Bayer's process

B. Koumanova*, M. Drame, M. Popangelova

University of Chemical Technology and Metallurgy, Department qf Chemical Engineering,

8 Kliment Ohridski Str., 1756 Sq[ia, Bulgaria

Received 30 August 1995; revised 12 July 1996; accepted 3 August 1996

Abstract

The red mud wasted from the Guinean bauxite refinery was studied for phosphate removal

from model aqueous solutions of potassium orthophosphate (OPh) and sodium tripolyphos￾phate (TPPh). The red mud has been treated with concentrated sulphuric acid. After

filtration of the acid suspension, the activated mud was washed (pH 7), dried and ground to

powder. The influence of acid to mud ratio, and contact time between them, on the extent

of phosphate removal has been studied. The importance of the preliminary acid treatment of

the red mud was established by parallel experiments using both raw and activated red mud.

The dose of red mud added to the aqueous solutions, the contact time between them and

initial concentrations of phosphates in the solutions for the complete removal of phosphates

have been determined. Regression models describing the process for both types of phosphate

solutions have been deduced. Copyright © 1997 Elsevier Science B.V.

Keywords: Red mud; Phosphate removal: Orthophosphate; Tripolyphosphate

1. Introduction

Red mud is formed as a waste during bauxite refining known as Bayer's process.

Its main constituents are iron (giving the red colour), aluminium, sodium and silica,

and their amounts vary according to the bauxite location. The disposal of large

* Corresponding author. Tel: 4- 359 2 6254409; fax: + 359 2 685488:

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