Evaluation of adsorptive performance of Mn-doped Fe2O4 nanoparticles loaded on activated carbon in removal of boron ions from synthetic wastewater

Specific industrial activities such as hydraulic fracturing generate wastewaters containing boron which exceed the standard concentration limits. Removal or reducing the concentration of this pollutant through proper treatment prior to discharge into the environment has become a critical issue. As a novel composite adsorbent, Mn-doped Fe2O4 nanoparticles loaded on activated carbon was synthesized for the first time and used for the adsorption of boron ions from aqueous solutions. This novel adsorbent was characterized by FTIR, SEM, and XRD analyses. The effect of solution pH, adsorbent dosage, temperature, initial concentration of boron ions, and contact time was studied through adsorption batch experiments and an acceptable maximum removal efficiency which was equal to 96.44% was achieved in the following conditions: pH, 6.0; adsorbent dosage, 0.1 g/L; 298.15 K; initial concentration of 1 mg/L and 85 min. Furthermore, regeneration of the adsorbent approved its performance for 3 adsorption/desorption cycles. Additionally, it was shown that the adsorption of boron ions was well described by the Temkin isotherm model and the maximum adsorption capacity of 9.03 mg/g was also achieved. The values of R-L and n were 0.05 and 0.29 which denote that the adsorption was desirable, reversible, and chemical. Kinetic study showed that pseudo-second-order model (R-2 = 0.9997) explained the kinetic behavior of the process well and based on the thermodynamic analysis the current adsorption process was exothermic and spontaneous (Delta H degrees = -6.2 kJ/mol and Delta S degrees kJ/mol center dot K= -16.11). These results indicated that pretreatment of Mn-doped Fe2O4 nanoparticles loaded on activated carbon can optimize the removal of boron ions from aqueous solution since this novel adsorbent presented an acceptable adsorptive performance in this study and it can be recommended for the removal of similar pollutants from wastewaters.