Gold phytomining using local plants enhanced by rhizobacteria and compost fertiliser

Abstract

Spent ore is a waste material produced during mineral processing, from which precious metals such as gold can potentially be recovered through phytomining. This study aimed to analyse the geochemical characteristics of spent ore and to test the effects of rhizobacterial inoculation and compost addition on the ability of local plants to extract and accumulate gold from spent ore at the site. The research comprised the following stages: spent ore sampling, sample preparation, geochemical characterisation of the samples, an on-site phytomining experiment (including the establishment of demonstration plots, plant propagation and acclimatisation, preparation of rhizobacteria, planting and plant maintenance, harvesting and determination of Au content), and data analysis involving the calculation of the bioaccumulation factor (BCF) and translocation factor (TF), as well as ANOVA. The results showed that rhizobacterial inoculation and compost addition affected the plants’ ability to absorb and accumulate Au, as reflected in their BCF and TF values. The most effective treatment comprised inoculation with Bacillus cereus RTKS and the addition of compost at a compost-to-spent-ore ratio of 1:1, which resulted in the highest BCF and TF values and a high Au content in the plants. This finding is significant because it indicates that rhizobacterial inoculation combined with compost in the appropriate proportion can increase plants’ ability to accumulate metals from the soil, including both precious metals and pollutant metals. Gold can be recovered as a valuable product through phytomining, whereas pollutant metals can be removed from the soil through phytoremediation.