2.4. Adsorption experiments
Batch adsorption study of water-soluble reactive dye Remazol Red RB-133 (RR RB-133) onto MgO nanomaterials was carried out in 250 mL beakers which contained 100 mg MgO and 100 mL dye solution of desired concentration. The solution in the beakers was kept stirred at the desired temperature and pH = 7. At various
time intervals, the solutions were centrifuged at 7000 rpm for 5 min and the absorbance of supernatant solution was recorded using UV–vis spectrophotometer (Jasco V-550, Japan). The corresponding concentration in the supernatant solution was obtained using a previously constructed calibration graph. The equilibrium
adsorption capacities (qe) were then obtained by using the following mass balance equation.