Experimental study on reinforcement and remediation of nickel-contaminated sludge using grouting vacuum preloading combined with electroosmosis

Traditional vacuum preloading, electroosmotic techniques face challenges such as poor removal efficiency, reinforcement and high energy consumption when treating contaminated sludge with high water content. This study investigates the reinforcement and remediation of nickel (Ni)-contaminated sludge with high water content using an approach combining grouting, vacuum preloading, and electroosmosis (GVE). Through laboratory model tests, the effects of grouting agents, vacuum preloading, and voltage loading modes on Ni removal efficiency, soil reinforcement, and energy consumption were evaluated. The results demonstrate that the grouting of sodium alginate can chelate Ni²⁺ in the soil, facilitating the removal of heavy metal ions during the electroosmosis process. The GVE combined with vacuum preloading significantly enhances Ni removal rates, achieving up to 94.52 % compared to 65.11 % with electroosmosis alone. Additionally, GVE reduced soil water content to 30.34 % and increased shear strength to 98 kPa, indicating improved soil reinforcement. The step loading further reduced energy consumption by over 35 % compared to constant voltage loading while enhancing both soil remediation and reinforcement. This study concludes that GVE, particularly with step loading and intermittent loading, is an effective and energy-efficient method for remediating and reinforcing heavy metal contaminated sludge.