Abstract: To tackle the problems of poor dehydration effect and unqualified removal of heavy metals in the traditional vacuum preloading for contaminated sludge treatment, we propose a vacuum preloading-radiation electroosmosis technology that integrates both dehydration and heavy metal removal capabilities. Through the theoretical derivation of the reinforcement mechanism of the radiation electrode and the removal mechanism of heavy metal ions, we discovered that, compared with the traditional vertical electrode, the radiation electrode substantially improves the drainage volume per unit time and shortens the consolidation time via two mechanisms: superimposing the transverse electric field to augment the overall electric field intensity, expanding the effective action area. Its consolidation and drainage performance surpasses that of the traditional vertical electrode. Moreover, the migration duration of heavy metal ions is longer in electroosmosis with traditional vertical electrodes than with radiation electrodes, proving that heavy metal ions at the identical position are subjected to a more intense electric field from the radiation electrode, leading to accelerated ion migration. To assess the dehydration and heavy metal removal efficacy of the vacuum preloading-radiation electroosmosis technology in treating contaminated silt, we conducted six sets of laboratory model tests, encompassing traditional vacuum preloading (VP), vacuum preloading + electro-osmosis (VP+EO), vacuum preloading + electro-osmosis with cathode-anode radiant electrode (VP+EOCAR), vacuum preloading + electro-osmosis with sustained power (VP+EOSP), vacuum preloading + electro-osmosis with intermittent power (VP+EOIP), and vacuum preloading + electro-osmosis with graded power (VP+EOGP). We analyzed indicators such as drainage volume, settlement, vane shear strength, water content, degree of consolidation, and Cu2+ content. The findings reveal that VP+EOGP yields the optimal dehydration results, with a 38.19% increase in drainage volume, a 26.63% rise in settlement, a 39.51% to 73.4% enhancement in vane shear strength, and a 3.41% to 5.36% reduction in water content compared to VP. For heavy metal removal, VP+EOSP performs best (with a Cu²⁺ removal of 224.04 mg/kg), followed by gradual power-on VP+EOGP (with a Cu²⁺ removal of 220.1 mg/kg). This finding offer a theoretical foundation for the improvement of vacuum preloading technology.

Key words: vacuum preloading, radiant electrode, laboratory model test, heavy metal removal, contaminated silt