## 4 Conclusions  
In this study, based on a detachable vacuum electro-osmotic indoor model experiment system, dredged sediment from Tai Lake was used to conduct vacuum, electro-osmosis, and vacuum electro-osmosis reduction, and remediation experiments with and without copper contamination. The experimental rules are summarized in three dimensions: reduction (drainage, moisture content, strength, settlement, and cracks), remediation (contaminant concentration, substance composition, and electrical conductivity), electrodynamic characteristics, and electrical energy losses (current and potential). The operating properties of vacuum and electro-osmosis under the integrated conditions of reduction and remediation were illustrated, and the interaction between reduction and remediation was characteristically analyzed. Furthermore, under this circumstance, considering the difficulty of contaminant concentration determination, a prediction model of contaminant concentration based on conductivity and moisture content was given.  
The following conclusions are specifically drawn:  
1. For different methods, regardless of the sediment with or without copper, the law of reduction is similar, and the effect of vacuum electro-osmosis is optimal. However, the copper in the contaminated sediment will generate precipitation to block the sediment pore space during the treatment process, which in turn leads to the effect of reduction on contaminated sediment being worse than that on the pollution-free sediment with the counterpart method. The contaminants have the most significant effect on the electro-osmosis method, indicating that the applied electric field is the main reason for the precipitation.
2. The electric field enables the directional migration of copper contaminants from the anode to the cathode, while the vacuuming at the cathode facilitates the discharge of copper ions from the cathode position. Vacuum electro-osmosis can accomplish the migration and discharge of copper contaminants by combining the benefits of both methods. The removal rate at the anode can reach 45.1% and the removal rate at the cathode can reach 50.0%. After the test, the content of sodium, aluminum, and silicon underwent different degrees of reduction. Sodium plays a critical part in both  
Figure 17: Voltage distributions at different times.  
electro-osmosis and electro-migration, while calcium and copper are more preferable to aluminum and silicon for the formation of precipitates.
3. The presence of copper ions in the contaminated sediment improves the electrodynamic properties of the sediment. The conductivity of dredged sediment is strongly related to the moisture content and contaminant concentration. Based on the relationship between conductivity and moisture content of pollution-free soil, the correlation equation of conductivity with moisture content and contaminant concentration is established by considering the contaminant concentration correction. This equation can be applied to predict the dynamic changes in copper contaminant concentrations under reduction and remediation conditions.
4. Electro-migration is the dominant factor in governing the remediation process. Nevertheless, the reduction will lead to a decrease in sediment moisture content, which will influence the electric field distribution of the sediment and weaken the remediation effect. The current in the sediment attenuates exponentially, whereas the effective potential rises transiently and then falls rapidly. Although the electrical parameters of contaminated sediment may be better, the sediment is susceptible to precipitation due to the alkaline environment. For the single electro-osmosis method, the electrodynamic parameters attenuate more rapidly and the inhomogeneity of electric field distribution is more obvious, which affects the effect of reduction and remediation.