Characteristics of persulfate gel materials in groundwater remediation: Column and tank experiments investigations.

Using persulfate and environment-friendly gel solution as raw materials, persulfate gel sustained-release material (PGSR) and persulfate gelatin gel sustained-release material (G-PGSR) were developed. The main purpose of this study was to evaluate the potential of PGSR and G-PGSR in sustained release, migration and removal performance through column and tank experimental investigations. Results showed that the maximum release rates of PGSR and G-PGSR in water columns were 1.34 and 0.58 mg min-1 and the cumulative release amounts achieved 2950 and 2818 mg within 75 h, representing release efficiencies of 98.3 % and 93.9 %, respectively. In three sand columns, the maximum release rate was 0.32, 0.21, and 0.16 mg min-1 and the cumulative release achieved 473, 426, and 359 mg within 90 h with release efficiencies of 94.7 %, 85.3 %, and 71.7 %, respectively. Release time and rate of PGSR and G-PGSR are constrained by the permeability of porous media. G-PGSR in the sand tank exhibited migration and release characteristic with the slow-release diffusion effect. Lateral diffusion produced higher S2O82- concentration far beyond what was allowed in the tank. The saturated hydraulic conductivity decreased from 4.9 × 10-3, 1.1 × 10-3, and 4.9 × 10-4 cm s-1 to 2.4 × 10-3, 7.4 × 10-4, and 2.1 × 10-4 cm s-1 in columns filled with medium, fine, and silt, respectively. G-PGSR injection did not significantly change the order of magnitude of hydraulic conductivity. 2,4-dinitrotoluene removal performance was affected with the inlet flow rates, which decreased from 92 %, 82 %, and 78 % to 42 %, 28 %, and 8 % during 24 PV at the flow rate of 0.5, 1.5, and 4.5 mL min-1, respectively. Moreover, the removal efficiency was enhanced by G-PGSR with activated carbon as an activator. This study expands our understanding and ability of persulfate gel materials for groundwater remediation and provides a certain research basis for practical applications.