Enhancement of magnesium phosphate cement solidification of Pb2+ by K-struvite whisker in lead-contaminated solution

Lead pollution represents a serious environmental issue, especially has both adverse effects on human health and ecosystem. Magnesium phosphate cement (MPC) as a novel matrix was developed for the treatment of the toxic lead-contaminated water, however, the immobilization efficiency on heavy metals by the MPC was limited. To enhance the immobility efficiency of the MPC on Pb2+ in the lead-contaminated solution, MgKPO4·6H2O (K-struvite) whiskers (one of hydration products from MPC) were successfully synthesized and incorporated into the MPC. The phase composition and microstructure of the K-struvite whisker were characterized via XRD, XRF, FTIR and SEM method. The immobilization process of MPC was carried out by isothermal calorimetry, inductively coupled plasma (ICP), pH/conductivity, XRD, TG/DTG, SEM and EDS analysis. The results indicate that K-struvite whisker could improve the immobilization efficiency of the MPC on Pb2+, resulting in 3.3% higher immobilization efficiency compared to the MPC without K-struvite whisker enhancement. Isothermal calorimetry results showed that K-struvite whisker accelerated the hydration process of MPC and advanced immobilization reaction stage. K-struvite whisker could provide alkaline environment and additional nucleation sites, resulting in more hydration products and higher immobilization efficiency, as well as traces of Pb(OH)2 and Pb3(PO4)2. The final conclusion is that solidification enhancement of MPC of Pb2+ by K-struvite in the lead-contaminated water is efficient, in line with an environmental sustainable development.