Formulation of a Permeable Reactive Mixture for Groundwater Remediation Based on an Industrial Co-product: Permeability and Copper Retention Study

The objective of this research is to formulate a permeable material based on apatite gel having the ability to retain heavy metals, to be used in a permeable reactive barrier (PRB), an in situ passive groundwater treatment technology. This new material is produced from non-toxic waste in the research laboratory of a chemical company. It is characterised by a thixotropic behaviour and a high ion exchange capacity. The apatite gel is the active agent of the reactive material; it ensures the retention of heavy metals by ion exchange. Sand and an organic binder are also incorporated into the mixture, providing both high permeability and mechanical strength to the mixtures. An original experimental apparatus intended for measuring both water permeability and the retention of heavy metals has been specially designed and developed for this study. The mixture consisting of 95 % silica sand, 5 % apatite gel and 3 % epoxy was qualified as a suitable PRB mixture, due its high permeability, its good retention capacity and its acceptable mechanical strength.