Feasibility of using demolition waste as an alternative heavy metal immobilising agent.
Demolition waste consisting of cement paste, lightweight concrete and bricks is a worthless material generated by a growing city. However, research suggests that it may be applied as an alternative heavy metal immobilising agent. The diverse characteristics of demolition waste were examined. Cadmium was selected as there presentative heavy metal to investigate demolition waste adsorption capacity. The solid-liquid distribution coefficients (Kd) were observed. The adsorption isotherms were applied to investigate adsorption characteristics. Carbon content in the demolition waste materials was low and mainly in inorganic form. Cement paste and lightweight concrete had an alkaline pH with very high acid neutralising capacity (ANC). The surface area and cation exchange capacity (CEC) of these materials were low. Cement paste possessed the highest pH, ANC, CEC and surface area, with the highest Kd; however, its specific surface area and CEC were low compared to activated carbon and organic material. The adsorption isotherms indicated surface heterogeneity with favourable conditions for adsorption and the mean free energy suggested physisorption with multilayer formation. The Kdvalues of the tested materials were comparable to soil which was not effective in immobilising heavy metal via adsorption mechanisms. However, the high pH and ANC of cement paste and lightweight concrete can improve the heavy metal adsorption capacity of soil and soil ANC that help prevents and controls leaching by heavy metals.
Environmental Research Institute, Chulalongkorn University, Bangkok 10330, Thailand; Research Unit of Site Remediation on Metals Management from Industry and Mining (Site Rem), Chulalongkorn University, Bangkok 10330, Thailand. Electronic address: sdamrongsiri@gmail.com.
Seelawut
S
Damrongsiri
D000327:Adsorption; D002606:Charcoal; D019216:Metals, Heavy / Q000737:chemistry*; D012987:Soil; D012989:Soil Pollutants / Q000737:chemistry*
D019216:Metals, Heavy; D012987:Soil; D012989:Soil Pollutants; D002606:Charcoal
Acid neutralising capacity; Cement paste; Demolition waste; Heavy metal; Immobilising agent; Lightweight concrete