Occurrence and distribution of organic compounds in landfill leachate and their influence on metal mobility and recovery.

Resource security has attracted increasing attention globally due to the growing demand for use in a wide range of products. Municipal solid waste landfills and leachate are significant untapped resources that can contribute to a sustainable and secure supply of raw materials. Recent studies reported heavy metals (HM) and rare earth elements within the waste mass buried in landfills that can theoretically be recovered and reintroduced within the material loop of the circular economy framework. However, metal recovery only cannot be visible economically due to its low concentration. Therefore, research is required to understand how metals can be effectively mobilised. This research is carried out to develop a methodology to demonstrate the metals in landfill leachate as a potential secondary source. The batch and column percolation tests are performed to establish the relationship between metals recovery rate and other parameters. This PhD project investigates the influence of factors to increase metal mobility. Firstly, pH value and depth effect on metal release were analysed. The pH value plays a critical role to increase metal recovery rate; however, no significant correlation between depth and metal release was observed. As the analysis shows that metal release is highly increased in acidic conditions, column percolation was conducted at the optimise pH values with leachate recirculation. Leachate recirculation accelerates the degradation of organic waste, consequently enhancing the hydrolysis rate that may reduce the pH value. Lastly, different humic concentration on the metal(loid)s release from landfill leachate was investigated. This thesis presents a high potential to help evaluate the environmental impact to control the pollution and recover metal(loid)s.