Applicability and Extraction Characteristics of Aluminum Sulfate as Extractant of Harmful Heavy Metals for On-Site Treatment of Deep-Sea Mining Tailings

Abstract

This research was focused on the eco-friendly treatment of deep-sea mining tailings in the sea areas and mainly dealt with evaluating the optimal conditions by comparing aluminum sulfate (AS), which had been proven recently to have an effect as a heavy metal extractant, with ethylenediaminetetraacetic acid (EDTA) in terms of environmental and economic feasibility. Harmful heavy metals in the manganese nodules (2%, w/v) were chemically washed by mixing with each EDTA and AS concentration for 16 elapsed times. Copper, zinc, nickel, and cadmium, which could have a fatal effect due to their high total content or high bioavailable content, were selected as the primary treatment target materials. The content of harmful heavy metals was 293.2 times more for nickel when compared with environmental standards of various countries. When 1% AS was used as the extractant, the removal efficiency of harmful heavy metals compared to the bioavailable content was 32.77% on average. It has been verified that multi-stage treatment could be necessary, and the short treatment time could be an important factor. Within a short elapsed time (3 h), the remediation efficiency of zinc and nickel under the 1% AS condition was higher than with 0.1 M EDTA. In terms of environmental and economic feasibility, it was verified that the use of 1% AS would be reasonable. The results of this research could be valuably applied to process design and optimization as basic data presented before the development of remediation technologies in the future.