Preparation of iron composite filler for PRB technology and its application in the removal of toxic metals(loids) from groundwater

Abstract

Iron-based materials have garnered significant research interest due to their high surface reactivity, exhibiting potential for remediating metal(loid)s in groundwater. However, agglomeration and blockage limit its long-term and stability performance in application in permeable reactive barrier (PRB) technology. In this study, three innovative and low-cost iron composite fillers were prepared using a mass-producible impregnation method and applied as fillers for PRB. Static sorption and dynamic column experiments were conducted to assess the long-term performance of these composites to remediate multiple toxic metals(loids) contaminated groundwater. The results showed that the iron composite fillers had the excellent adsorption capacities for Co(II), Cu(II), Cr(VI) and As(III) from simulated contaminated groundwater even under the interference of Fe(III) and Mn(II). The pH of the influent favored the adsorption of toxic metals(loids) by the iron composite fillers in the order of 3.00＞5.00＞8.00＞7.00＞9.00＞6.00. The overall adsorption process was more consistent with the quasi-secondary kinetic equation. The corresponding constant values of Cr, Co, Cu, and As on CZ were 0.022, 0.093, 0.756, and 0.342 h−1, respectively. And that of CP-I and CP-II were 0.004, 0.022, 0.001, 0.126, 0.008, 0.041, 0.001, and 0.154 h−1, respectively. The specific surface area of the composite zeolite (Na92Al92Si100O384) and composite pumice was 48.185 m2/g and 0.63 m2/g, respectively. The dynamic column experiment was run steadily for 40 days, during which the average removal rates of toxic metals(loids) were above 95% and approximate 20 times its own volume of contaminated water was purified. FeO(OH) on composite zeolite and Fe3O4 on composite pumice played a dominant role in the removal of toxic metals(loids). The toxic metals(loids) adsorbed in the PRB were mainly in a stable phase of residual fraction and Fe-Mn oxide fraction, making them less likely to cause secondary pollution problems.