Production of liquid alum coagulant from local Saudi clays

Abstract EN

This study was carried out to investigate the use of local clays extremely abundant in the Kingdom for production of liquid alum.

Local kaolinitic clay containing 29.4 % Al2O3 was ground, activated by calcination and treated with sulfuric acid solution to extract alumina.

In the activation step, the effects of grain size of clay, temperature and period of calcination on the extraction of alumina and iron oxide are investigated.

Leaching experiments were conducted using the stoichiometric requirement of 40 wt.

% H2SO4 for one hour under boiling conditions.

Clay samples of particle size ranging from 8 to 200 mesh standard Tyler screens, calcined at different temperatures ranging from 450 to 1000 oC and for different periods ranging from 15 to 180 minutes were used.

The results revealed that 90.9% of Al2O3 can be extracted when using–65 mesh clay, calcined at 700 oC for one hour.

Experiments on the effect of acid concentration on alumina extraction from clay under the above conditions indicate that 40 wt.

% acid is the recommended as it gives high extraction of alumina and at the same time results in free flowing properties of the reaction mixture.

Leaching experiments were performed to investigate the effects of acid to clay ratio (50 to 120 %) and leaching period (0.25 to 3 hrs) on alumina extraction.

The results indicate that 88.6 % of Al2O3 could be extracted when using 88.1% of stoichiometric requirement of 40 wt.

% acid for two hours leaching period under boiling conditions.