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

Abstract

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.