Synthesis of highly effective absorbents with waste quenching blast furnace slag to remove Methyl Orange from aqueous solution

Water quenching blast furnace slag (WQBFS) is widely produced in the blast furnace iron making process. It is mainly composed of CaO, MgO, Al2O3, and SiO2 with low contents of other metal elements such as Fe, Mn, Ti, K and Na. In this study, WQBFS was treated with grinding, hydrochloric acid acidification, filtration, filtrate extraction by alkali liquor and a hydration reaction. Then BFS micropowder (BFSMP), BFS acidified solid (BFSAS) and BFS acid-alkali precipitate (BFSAP) were obtained, which were characterized by X-ray diffraction, scanning electron microscopy, X-ray fluorescence and Brunauer-Emmet-Teller (BET) specific surface area. The decoloration efficiency for Methyl Orange (MO) was used to evaluate the adsorptive ability of the three absorbents. The effects of adsorptive reaction conditions (pH and temperature of solution, reaction time, sorbent dosage and initial concentration) on MO removal were also investigated in detail. The results indicated that BFSAP performed better in MO removal than the other two absorbents. When the pH value of MO solutions was in the range 3.0–13.0, the degradation efficiency of a solution with initial MO concentration of 25 mg/L reached 99.97% for a reaction time of 25 min at 25°C. The maximum adsorption capacity of BFSAP for MO was 167 mg/g. Based on optimized experiments, the results conformed with the Langmuir adsorption isotherm and pseudo-second-order kinetics. Among inorganic anions, SO42 − and PO43 − had significant inhibitory effects on MO removal in BFSAP treatment due to ion-exchange adsorption.