Release and mobility of hexavalent chromium in contaminated soil with chemical factory waste: experiments, Cr isotope analysis and reactive transport modeling

CEBALLOS, ELINA; CAMA, JORDI; SOLER, JOSEP M.; FREI, ROBERT

JOURNAL OF HAZARDOUS MATERIALS.

ELSEVIER SCIENCE BV

Año: 2023

0304-3894

Our study focused on the leaching processes in soil contaminated with hexavalentchromium (Cr(VI)), traced to industrial waste from a disused site and resulting ingroundwater contamination. Mineral and geochemical characterization of the soil bymeans of XRD, SEM-EDS, total digestion and sequential extractions revealed that themain Cr content was from solid waste located in the upper meter of the soil profile.Flow-through and column experiments were carried out to investigate the processesresponsible for Cr(VI) release. Cr(VI) mobility along the soil profile was also assessed.Moreover, Cr isotope signatures were used to evaluate a potential Cr(VI) reductionprocess, which preferably could immobilize toxic Cr(VI) complexes. Onedimensional(1D) numerical simulations reproduced the Cr(VI) release from the flowthroughexperiment containing the Cr(VI) rich-solid waste and also the Cr(VI) mobilityalong the column experiment. These results enabled us to interpret quantitativelythe processes resulting in Cr(VI) contamination and mobility along the soil profile.Cr(VI) was released from dissolving Cr(VI)-rich phases (e.g., sodium chromate,Cr(VI)-hydrocalumite and Cr(VI)-ettringite) of the solid waste layer. Cr(VI) reductionand Cr(VI) adsorption did not take place along the column. Such accurate characterizationof these processes is necessary for the mitigation of Cr(VI) mobility in contaminatedsoils.