Jacobs Journal of Civil Engineering

Study of The Mechanical Strength and Leaching Behavior of Phosphogypsum in a Sulfur in Matrix

*Mohamed CHOURA
Department Of Civil Engineering, Radioanalysis And Environment Laboratory, Tunisia

*Corresponding Author:
Mohamed CHOURA
Department Of Civil Engineering, Radioanalysis And Environment Laboratory, Tunisia
Email:chouramed@gmail.com

Published on: 2015-02-28

Abstract

This work suggests a treatment alternative to phosphogypsum, an industrial solid waste generated by the Tunisian Chemical Group in huge amounts, by sulfur waste from a natural gas purification plant in Tunisia, contaminated with heavy metals and mercury, used as a binder. Mixtures with different phosphogypsum contents were made at a temperature equal to 150°C and compacted at the paste phase with a pressure of 1.5 MPa. The mechanical strength and leaching behavior results were sought after a period of one month and then with an artificial ageing cycle of thermal shocks and humidity variation. The comparison between the solid PG-sulfur matrices shows that the mixture tested with 50% sulfur/50% PG had the best mechanical strength up to 40 MPa. The leaching behavior tests also proved that the mixture tested with 50% sulfur, 50% PG is most efficient, resulting in a total retention of copper, lead, cadmium and almost total retention of zinc and nickel. Artificial ageing cycles had an insignificant effect on the mechanical strength and chemical behavior of the tested matrices which proves the long term efficiency of the suggested treatment.

Keywords

Phosphogypsum; sulfur matrix; Chemical Fixation and Solidification; artificial ageing; leachability

Introduction

Phosphate rock currently accounts for over 90% of phosphoric acid (used as a fertilizer) production in the world. The processing of phosphate rock by the wet acid method generates a huge quantity of waste by-product, namely Phosphogypsum (PG). About 5 tons of PG are generated per ton of phosphoric acid production. World PG production is variously estimated to be around 100–280 Mt per year [1].