Remediation of heavy-metal-contaminated soil with two organic acids: Washing efficiency, recovery performance, and benefit analysis

There remains a need to develop efficient and recoverable washing reagents to repair heavy metal-contaminated soil. However, the past study of recovery only considered conventional chelating agents, hindering the sustainable development of new reagents. In this study, two new-reagents, organic phosphonic acid (DTPMPA) and polycarboxylic acid (AA/AMPS/HPA), simultaneously investigated their ability to remove heavy metal and recover by electrochemical to improve reagent sustainability. Results indicated that the metal removals were influenced by the washing solution concentrations, pH, and contact time. The maximum removal by DTPMPA was 72% Cd and 33% Zn, were higher than those of AA/AMPS/HPA (concentration, 5%; pH, 3.0; and contact time, 120 min). The strong chelation of the phosphonic acid group of DTPMPA binds more metal ions. Characterization results demonstrated that both reagents were successfully recovered using electrochemical methods. While AA/AMPS/HPA had a better recovery performance because of electrostatic adsorption interactions with the metal ions, the rewashing ability of Cd and Zn was 88% and 64% of the fresh solution. Moreover, in benefit analysis, AA/AMPS/HPA showed better circular economy and long-term sustainability properties. Therefore, AA/AMPS/HPA is a feasible remediation reagents of the heavy-metal-contaminated soil with both efficiency and sustainability. The development of reagent takes into account efficiency and reuseable simultaneously, showing great economic benefits.