Factorial experimental design for the removal of disperse dyes using hydroxyapatite prepared from Moroccan phosphogypsum

Azo dyes are the major group of synthetic dyes known and have given rise to many water and soil environmental problems, the most of this azo dyes were used in textile industry. The aim of this study is the removal of Disperse Blue 79 (DB 79) and Disperse Blue 165 (DB 165) as azo dyes by Hydroxyapatite (HAP). The adsorption experiments were carried out to investigate the factors that influence the dyes uptake by hydroxyapatite, such as the contact time under agitation, adsorbent dosage, initial dye concentration and size of HAP. To reduce the number of experiments, full factorial experimental design at two levels (2 4 ) was used to achieve optimal conditions for the removal of DB 79 and DB 165 from aqueous solutions.