Remediation of heavy metal-organic compound-contaminated soil by a new curing agent HCM

• A new curing agent, HCM, is used to treat contaminated soil. • An improved potential ecological risk assessment method is proposed. • The differences between cement and HCM are discussed. • The mechanism of HCM remediation is analyzed. • The prediction formulas, optimal dosage considering economic benefits are obtained. Remediation using cement performs poorly in high-concentration heavy metal-organic compound-contaminated soils and exhibits high levels of alkalinity, making it unsuitable for the survival of soil organisms. This study developed a novel curing agent, HCM, composed of hydroxypropyl methylcellulose (HPMC), calcium salts and magnesium salts. The soils used in this study were collected from a chemical enterprise site. Laboratory tests were conducted to investigate the changes in pollutant content, pH value, California bearing ratio (CBR) and unconfined compressive strength (UCS) of the soils before and after the application of HCM. The results, evaluated using an improved potential ecological risk assessment method, demonstrated that HCM showed the best performance in reducing the ecological hazard index for Cr, with a reduction of 86.7 %. The CBR values of the remediated soils all meet regulatory requirements, with the maximum UCS exceeding 600 kPa. From an economic perspective, the optimal concentration of HCM is 3.2 %. Microscopic analysis revealed that the primary mechanism of remediation using HCM involves aggregation of soil particles to adsorb heavy metals and the increase in pore spaces to adsorb VOCs. Additionally, HPMC forms granular colloids, constructing a strength framework for the soil body to enhance its overall strength.