High adsorption of methylene blue by salicylic acid-methanol modified steel converter slag and evaluation of its mechanism

A novel adsorbent based on steel converter slag (SCS), useful for adsorbing cationic pollutants from water was prepared by a simple method. The characterization showed that salicylic acid-methanol (SAM) modification selectively removed calcium silicate minerals from the surface of SCS and lead to a prominent increase in the specific surface areas. The maximum adsorption capacity of SAM-modified SCS for methylene blue (MB) at initial pH of 7.0 and temperature of 293 K was 41.62 mg/g, which is 35.2-times higher than that of SCS (1.15 mg/g). Adsorption kinetics and isotherms of MB on the SAM-modified SCS can be satisfactorily fitted by pseudo-second order kinetic and Langmuir model, respectively, which suggest that single-layer chemical adsorption was mainly responsible for MB removal. Further studies showed that pH value and ionic strength of wastewater have minimal effects on the adsorption capacity of SAM-modified SCS. A small decrease (<10%) was found in the adsorption capacity of SAM-modified SCS after five cycles. These findings indicate that SAM-modified SCS is a promising adsorbent for the efficient removal of MB from aqueous solution due to its low cost, good thermal stability, excellent adsorption performance and simple separation. (C) 2018 Elsevier Inc. All rights reserved.