Long term leaching behavior of arsenic from cemented paste backfill made of construction and demolition waste: Experimental and numerical simulation studies.

The arsenic long-term leaching behavior of the cemented paste backfill obtained from the construction and demolition waste (CPB-CDW) is captured, which can be utilized in the potential engineering application. Laboratory studies were conducted on samples obtained from a mining site and the test results were imported into a numerical simulation model. It was found that the Elovich equation can describe well the As leaching behavior. Initially, the As concentrations decreased in the roadway in the mine and then increased along the roadway and attained a maximum concentration (8.149 × 10 mg/L) at the lower segment. When the groundwater was in the static mode, the As concentration increased dramatically followed by a gradual increase. Eventually, the concentration decreased gradually. For the dynamic condition, the As tended to move in a cluster form and the associated leaching and mass transfer process of As in the CPB-CDW were similar to those observed when the groundwater was in a static condition. However, the difference in the distribution of the amount of As in the leachate fluctuated continuously and the overall trend was to approach a steady state. As such, the time frame of such a mass transfer in the mobilized water is reduced significantly.