The removal of radioactive strontium from wastewater has attracted considerable attention in recent years, in particular following the nuclear accident at Fukushima, Japan in March 2011.
To this end, Chinese researchers have developed a hydraulic pellet co-precipitation microfiltration (HPC-MF) process for the treatment of radioactive wastewater.
Strontium is removed by forming compact crystal particles when sodium carbonate, ferric chloride, and calcium carbonate are used as the precipitating agent, flocculating agent and seed crystal, respectively.
When the seed crystal concentration was 0.340 g/l, the mean and highest decontamination factors (DFs) were 842 and 1000, respectively. The concentration factor (CF) was greater than 2650.
The hybrid process eliminates difficulties associated with the mechanical equipment, radiation protection, and precipitate concentration. It also achieves efficient and stable strontium removal.
The strontium removal mechanism is also revealed: the transfer of Sr2+ to the solid phase is primarily completed in the hydraulic reactor. The microfiltration process is essential to not only ensure stable separation efficiency, but also further improve the decontamination factor.
Sr2+ is transferred from the liquid phase into the solid phase by being incorporated into the calcium carbonate crystalline lattice, which forms a strontianite solid solution that is removed by subsequent solid–liquid separation.
The strontium concentration exhibits an exponential decrease. A higher seed crystal concentration results in faster precipitation kinetics, a shorter equilibrium time, and a lower effluent strontium concentration.
