Integration of electrokinetic process and nano-Fe3O4/S2O82− oxidation process for remediation of phthalate esters in river sediment

• The EK-assisted oxidation process is viable for remediation of phthalates in sediment.
• Daily injection of S2O82− and nano-Fe3O4 slurry into the anode reservoir is appropriate.
• Precipitates of iron species formed in the pores of sediment would lower the EOF rate.
• Improper ORP in the system might result in a serious corrosion of the metal anode.

The main objective of this study was to evaluate the suitability of coupling nano-Fe3O4/S2O82− oxidation process and electrokinetic (EK) remediation process for degradation of phthalate esters (PAEs) in river sediment. Test results for the removal of PAEs from a Taiwan river sediment are given as follows: (1) in the test run of injecting nanoscale Fe3O4 slurry and sodium persulfate solution into the anode reservoir, the derived radicals and oxidant were transported into the sediment compartment by electroosmotic flow (EOF) to oxidize PAEs in contact; (2) an increase of the electric potential gradient from 1 V cm−1 to 2 V cm−1 was found to enhance the removal of PAEs in blank tests with no addition of chemicals to the EK remediation system; (3) Fe2+ and Fe3+ originated from nano-Fe3O4 dissociation and/or naturally occurring iron compounds in sediment were suggested to form precipitates in the pores of sediment near the cathode rendering a decrease of the EOF rate; and (4) a prolonged treatment resulted in an enhanced removal of phthalates from sediment. Based on the research findings obtained, the EK-assisted nano-Fe3O4/S2O82− oxidation process is a viable technology for remediation of PAEs-contaminated sediment in situ.