The selected adsorbent was a metal hydroxide sludge (WS) from an electroplating
industry. Direct Blue 85 dye (DB) was used in the preparation of the synthetic wastewater. Firstly, adsorption kinetics and equilibrium were studied, in respect to many factors (temperature, pH, WS dosage and
presence of salts and dyeing auxiliary chemicals in the aqueous media). At 25 ◦C and pH 4, 7 and 10, maximum DB adsorption capacities in aqueous solution were 600, 339 and 98.7 mg/g, respectively. These
values are quite considerable, compared to other reported in literature, but proved to be significantly
reduced by the presence of dyeing auxiliary chemicals in the wastewater. The simulated textile wastewater treatment in SBR led to BOD5 removals of 53–79%, but color removal was rather limited (10–18%).
The performance was significantly enhanced by the addition of WS, with BOD5 removals above 91% and
average color removals of 60–69%.