Ability of dissolved organic carbon from simulated leachate to extract Pb from mine tailing

Abstract

Food waste such as fruits and vegetables (waste from market) are the vast majority waste in Thailand. These kinds of waste are rich in organic matter and have a high water content resulting in higher biodegradation. This leachate should be used further for any valuable purpose such as environmental remediation. It has been known from previous researcher that landfill leachate has an ability to extract heavy metal. It may be used as extraction agent to separate heavy metal especially lead from mine tailings. In this study, simulated leachate was generated from biodegradation reactor of fruit and vegetable wastes. Simulated leachate was collected and many parameters were measured to investigate the properties of leachate and also degradation phases. The results showed that the very low pH of the system was not appropriate for anaerobic bacteria The system had insufficient buffering capacity. Therefore, alkalinity addition and also leachate recirculation were necessary for this system to enhance the degradation rate. Simulated leachate was used for extraction of Pb from mine tailings. The comparison of extraction ability of leachate with different ages and properties were conducted. Simulated leachate from first few weeks which had pH lower than 4 could extract Pb as high as 60-70%. When the leachate increased same time as increasing of its pH to 5-8, its extraction ability decreased dramatically until no extraction ability at all. However, it showed some extraction ability again when it came to methane phase with pH more than 8.5 but the extraction ability was still lower than 10% until the end of experiment. Then simulated leachate was fractionated into three fraction; humic acids(HA), fulvic acids(FA) and hydrophilic fraction(HyI). Leachate contained very low content of humic acids (0.48% and 0.92%) and fulvic acids (15-29%). However from Fourier Transform Infrared Spectroscopy and UV-visible results, its functional groups were similar to humic acids from other sources.