Response surface modeling of the removal of methyl orange dye from its aqueous solution using two types of zeolite synthesized from coal fly ash

Coal fly ash (CFA) produced as a waste material in coal power plants was converted into Linde-type A (LTA) and Na-P type (ZP) zeolite using microwave irradiation. The prepared zeolites were characterized and modified using a cationic surfactant. The removal of methyl orange (MO) dyes from aqueous solution by LTA and ZP as adsorbent was studied by applying the response surface method (RSM). A quadratic model was developed to relate the MO removal rate to the main independent variables, namely the solution pH (in the 3-9 range), the initial MO concentration (in the 20-100 mg/L range), and the adsorbent mass (200-1000 mg/L). The modified MLTA was found to be a more effective adsorbent relative to the modified MZP. In addition, MLTA mass exerted the greatest influence on the MO removal process under the studied conditions. However, when MZP zeolite was used as an adsorbent, the pH of the solution was the most influential factor. The two quadratic models were found to be statistically significant.