Study on the use of EDTA chelating agent and solid amendments to enhance natural phytoaccumulation of metals in a phytomining process

Raw materials are fundamental to Europe’s economy, growth and jobs and they are essential for maintaining and improving our quality of life. However, primary production of the 28 Member States of EU to overall materials supply can be estimated at around 9% [1]. The necessity to identify alternatives way of retrieving as firstly stated in 2008 when the European Commission launched the “Raw Materials Initiative” (RMI) whose aim was to define which were the critical raw materials for the EU’s economy considering the whole supply chain. In recent decades phytomining, a phytomanagement application focused on the recovery of metals, claimed the attention of many researchers because it appears to represent an innovative low-cost technology for the selective recovery of valuable trace elements from secondary resources. However, two decades after its inception and numerous successful experiments, commercial phytomining has not yet become a reality, that’s why a large-scale demonstration is needed to identify operational risks and provide a solid evidence of profitability. With the intention to set an important milestone in the possible implementation of this sustainable perspective and fulfilling the European initiative, in 2014 the project Bergwerk Pflanze was approved. The aim of this project is to test feasibility of a phytomining process growing metal-accumulating plants on a substrate made of waste incineration ash, harvesting the metal enriched biomass and using it as a form of bio-ore in metallurgic processes. In in this thesis are presented the results of 2 experimental researches that were set down from February 2015 to July 2015 at the Institute of Soil Research of the BOKU University of Vienna, that is a stakeholder partner of the project. The aims of the first test was to evaluate the effects of different inorganic amendments (ground bricks, zeolith, and pomice) as a substrate conditioning agents in order to improve the bioavailability of targeted elements mitigating the characteristics of high pH and electrical conductivity of the bottom ash. Second investigations were set down to identify the effects of addition of the chelating agent EDTA (Ethylenediaminetetraacetic acid) on enhancing the bioavailability of targeted metals in the substrate and consequently on henancing the phytoaccumulation yield in the tested plants.