Preparation of new magnetic zeolite nanocomposites for removal of strontium from polluted waters

Efficient separation of strontium ions (Sr2+) from waters has become a critical technological requirement after the nuclear accident at Fukushima Daiichi power station. In the present investigation, new nanocomposites of zero valent iron nanoparticles-zeolite (nZVI-Z) and nano-Fe/Cu-zeolite (nFe/Cu-Z) were synthesized via a simple liquid-phase reduction approach and tested to determine their effectiveness in the sorptive removal of Sr2+ from aqueous solutions. The sorption of Sr2+ on both nanocomposites was studied in a batch sorption mode as a function of various environmental conditions such as initial Sr2+ concentration, contact time, pH, temperature, dosage of sorbent and competing cations (Na+, K+, Mg2+ and Ca2+). The results indicated that initial pH and temperature were significant for Sr2+ sorption on both nanocomposites. The Sr2+ sorption efficiency increases with the increase in nanocomposite dosage and decreases with the Sr+2 concentration. It was also found that although the sorption of Sr2+ was decreased by the presence of coexisting cations, the nanocomposites still exhibited high uptake capacity of Sr2+ ions. The Sr2+ sorption kinetics can be satisfactorily fitted by a pseudo-second-order kinetic model. The sorption isotherm data were well predicted using the Langmuir model. The maximum sorption capacity for nFe/Cu-Z was found to be 88.74 mg/g, which was greater than that for nZVI-Z (84.12 mg/g). In addition to the high sorption capacity, the nanocomposites could be easily separated from aqueous media after Sr2+ sorption using an external magnetic field. The calculated thermodynamic parameters such as Delta H degrees, Delta S degrees and Delta G degrees revealed the endothermic and spontaneous nature of the sorption process. The nanocomposites were also applied in a real seawater medium. The present study confirmed that the prepared nZVI-Z and nFe/Cu-Z nanocomposites could be employed as promising methods for the removal of Sr2+ from wastewater streams. (C) 2019 Elsevier B.V. All rights reserved.