Amended compacted clay liner for containment of copper-laden leachate in tailings reservoirs

Tailings leachate poses significant environmental risks, particularly in areas surrounding mining operations and urban developments. Compacted clay liners (CCLs) are commonly used as barrier materials in tailings reservoirs. However, their limited adsorption capacity for Cu(II) and relatively high hydraulic conductivity reduce their effectiveness in preventing heavy metals from reaching groundwater. To address these issues and enhance the environmental sustainability of mining waste management, this study investigates the amendment of CCLs. with clinoptilolite and sodium polyacrylate polymer (Na-PAA) to improve both hydraulic and adsorption performance, specifically targeting the containment of copper-laden leachate. Hydraulic conductivity and adsorption capacity of amended CCL were systematically evaluated through flexible-wall hydraulic conductivity tests and batch adsorption tests. Additionally, numerical simulations were conducted to assess the transport behavior of Cu(II) within the amended CCLs and to investigate the impact of CCL thickness on Cu(II) breakthrough time. The results demonstrated that the amended CCLs exhibited improved hydraulic performance compared to unamended CCLs. In the 100 mg/L Cu(II) solution test, the hydraulic conductivity of unamended CCL was 3.24 × 10−10 m/s, while that of amended CCL was reduced to 7.09 × 10−11 m/s, indicating a decrease of approximately 78.1%. Furthermore, the amended CCL showed a much stronger adsorption capacity for Cu(II), with a maximum adsorption capacity that was 64.95% higher than that of unamended CCL. Based on numerical simulation results, the relationship between the thickness of the amended CCLs and their hydraulic and adsorption performance was analyzed.