Supercritical carbon dioxide chelation extraction of heavy metal ions from drilling fluid waste: Experiment and simulation

Abstract

This study evaluates the application of supercritical carbon dioxide chelation extraction technology for treating heavy metal ions (Zn²⁺ and Cr³⁺) in drilling fluid waste. Through a combination of experimental and molecular dynamics simulation methods, the influence of extraction parameters (temperature, pressure, duration, and chelating agents) on the extraction efficiency are investigated. Findings show that increased duration and pressure significantly improve extraction efficiency, while temperature has a complex effect, initially increasing efficiency but plateauing and slightly decreasing at higher temperatures. The optimum extraction condition with pressure of 220 bar, temperature 348.15 K and an extraction duration of 70 min using ethylene diamine tetraacetic acid (EDTA) as the chelating agent has been determined. Importantly, molecular simulation analysis revealed that citric acid outperforms EDTA in terms of Zn²⁺ and Cr³⁺ aggregation by forming larger aggregates with greater numbers of molecules while reducing overall aggregate count. Furthermore, optimization of extraction pressure in the EDTA system shows potential benefits. These results suggest that supercritical carbon dioxide chelation extraction technology has strong potential for environmentally friendly and reliable waste management in the drilling industry. This study represents a significant step forward in developing sustainable solutions for heavy metal removal from drilling fluid waste.