The potential of using rice straw fly ash (RSFA) as low-cost adsorbents for the removal of hazardous 
azorhodanine (AR) dye from aqueous solution was investigated. The effects of different variables 
in the batch method as a function of solution pH, contact time, concentration of adsorbate, adsorbent 
dosage, and temperature were investigated, and optimal experimental conditions were 
ascertained: 0.05 g for initial dye concentration of 20–100 mg/L at pH 2. The experimental equilibrium 
data were tested by the isotherm models, namely the Langmuir and Freundlich ...