Abstract
High microbial cell counts have been recorded in sewage waters employed as process water in mineral beneficiation plants across the world. The presence of these microbes can negatively impact flotation performance through mineral passivation, although some microbes improve flotation performance as investigated in various bio-flotation studies. The current study aims to understand the electrochemical behaviour of minerals in the presence of a sodium ethyl xanthate (SEX) collector and microbes originating from a sulphide ore processing plant in South Africa. The electrochemical response was correlated to observe flotation performance. Mixed potential measurements were conducted in parallel to microflotation tests, to assess the hydrophilicity or hydrophobicity induced on sulphide minerals adapted to microbe-laden synthetic plant water. Sulphide minerals’ mixed potentials and interactions of SEX with sulphide minerals were dramatically reduced in the presence of the mixed microbial community (MMC). The observations were correlated with poor flotation efficacy noted in microflotation tests. These fundamental results shed light on how the adsorption of thiol collectors on sulphide minerals is adversely affected by microbes, prompting a discussion on flotation process monitoring when mineral beneficiation is conducted using microbe-laden water.
Highlights
The use of raw or partially remediated, sewage effluent water for the flotation beneficiation of minerals has become increasingly popular
The zeta potentials of the microbial suspension at an initial cell concentration of 1 × 108 cells/mL, sulphide minerals and sulphide minerals after interaction with the microbial suspension are illustrated in Figure 1; Figure 2
It should be noted that the microflotation tests exclusively focused on pure minerals, there is a possibility of observing different flotation performance when a real ore is investigated in laboratory batch flotation or under plant conditions
Summary
The use of raw or partially remediated, sewage effluent water (grey water) for the flotation beneficiation of minerals has become increasingly popular. Sewage water serves to limit the mining industry’s dependence on freshwater sources, which could alternatively be channelled towards other economic and societal activities that require significantly higher water quality levels in comparison to mineral beneficiation. South Africa, where sewage water is the main source of process water employed in the flotation circuit. In addition to incoming sewage water, the microbes found in process plant water originate from recirculated tailings pond water and mineral surfaces. When microbes are present in a flotation circuit, they can act as surface modifiers, collectors or depressants, attaching onto minerals and rendering them hydrophilic or hydrophobic [1,2,3,4]
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