Efficient adsorption of methylene blue from aqueous solution by hydrothermal chemical modification phosphorus ore flotation tailings

Phosphorus ore flotation tailings (POFTs) are solid wastes produced in the phosphorus flotation process, and most of the POFTs are directly discharged into the tailing yard without treatment. In this study, modified phosphorus ore flotation tailings (MPOFTs) were synthesized by a hydrothermal chemical modification method as an efficient adsorbent to remove MB. The MPOFTs, the effect of initial MB concentrations, reaction time and pH on the MB characterization, and the adsorption mechanism of MB were studied. The results showed that modification of POFTs had a great BET specific surface area (151.26 m2/g). The maximum adsorption capacity of MPOFTs for MB was 321.5 mg/g at an initial pH of 5.94, the initial MB concentration was 1400 mg/L, and the reaction time was 60 min and 293 K. Moreover, the kinetic adsorption data were well described by both Elovich and pseudosecond order models, while the isotherm data were best fitted by Langmuir model. A thermodynamic analysis indicated that the adsorption process was spontaneous and exothermic adsorption. This study provides a new method for the resource utilization of POFTs.