Efficiency assessment of ZVI-based media as fillers in permeable reactive barrier for multiple heavy metal-contaminated groundwater remediation

Four zero valent iron-based composites were prepared and applied as the reactive media of permeable reactive barriers. Batch tests and continuous-flow column experiments were conducted to assess the long-term performance of these composites for possible utilization as fillers for PRB. The experimental results of the batch tests revealed that in single-metal systems, the removal efficiency of Cu(II), Co(II), Cr(VI) and As(III) could reach 98% at equilibrium. Equilibrium data showed that composites displayed different selectivity values in binary and quaternary-component systems. For the continuous tests, column filled with chitosan-zero valent iron-based composites, exhibited optimal removal efficiency and achieved average removal values of 98.84%, 88.28%, 95.65% and 87.10% for Cu(II), Co(II), Cr(VI) and As(III) during the whole 30-day operation, respectively. Dynamic removal improvement of multiple metals was observed with further assembly media, with average removal of 99.11%, 90.05% and 87.34% for Cu(II), Co(II) and As(III), respectively. Combined with superficial characteristic analysis, the functional groups distributed on the surface of composites played a key role in metal sorption. Moreover, the adsorbed Cu(II), Co(II) and Cr(VI) gradually transferred to the mobile phase when the operational periods were prolonged, while As(III) became more stable.

Automated summary

The study demonstrated that using zero valent iron-based composites as fillers for permeable reactive barriers can effectively remove metal ions such as Cu(II), Co(II), Cr(VI) and As(III), showing potential application value. The composites exhibited different selectivity values in different metal systems, and also showed dynamic removal improvement for multiple metals.