Investigating the effect of degree of compaction, initial water content, and electric field intensity on electrokinetic remediation of an artificially Cu- and Pb-contaminated loess

Given copper and lead mine enrichment and the high yield of North-Western China, the metallurgical industry attains prosperity. Metallurgical industrial waste which contains heavy metals can cause contamination and threaten the fragile loess environment. The disposal of hazardous waste is becoming a challenging and unavoidable task when land contamination consistently raises environmental concerns. Electrokinetic (EK) technology is an increasingly popular alternative to traditional approaches for contaminated soil remediation because of its high time effectiveness and low risk of secondary pollution. This study investigates the effect of degree of compaction, initial water content, and electric field intensity on the percentage removal of heavy metals in the loess. An EK reactor applied to the EK experiments is set up to measure pH, electric conductivity (EC), and electromigration of cation and heavy metal ions. The experimental results indicate that the lower degree of compaction promoted the formation of the agglomerate structure, and therefore, caused the electromigration path wider and straighter towards elevating the percentage removal of heavy metals. Furthermore, the slippage of the Gouy layer aggravated the electromigration of the cations and heavy metal ions when subjected to the higher initial water content, thereby enhancing the percentage removal of heavy metals. Moreover, the electromigration of the cations and heavy metal ions was notably accelerated by the higher electric current resulting from the higher electric field intensity. The removal of heavy metals was improved accordingly. These results, however, also highlighted the deteriorated percentage removal by the precipitation of heavy metal compounds at the cathode, induced by the alkaline front. A dynamic pH regulation during the EK remediation and a permeable reactive barrier to separate the heavy metal ions from the hydroxide ions are deemed as of great necessity for optimising the removal of heavy metals in the loess.

Automated summary

With the rich copper and lead mineral deposits and high production in North-Western China, the metallurgical industry has achieved prosperity. However, the metallurgical industrial waste containing heavy metals can cause contamination and pose a threat to the fragile loess environment. Electrokinetic (EK) technology, due to its high efficiency and low risk of secondary pollution, is becoming a popular alternative for remediating contaminated soil. This study investigates the impact of compaction, initial water content, and electric field intensity on the removal of heavy metals in loess. The experimental results show that lower compaction, higher initial water content, and higher electric field intensity can enhance the removal of heavy metals, but the precipitation of heavy metal compounds at the cathode can also deteriorate the removal efficiency. Dynamic pH regulation and the use of a permeable reactive barrier are considered necessary for optimizing heavy metal removal in loess.