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Double refractory gold ore was sequentially pretreated to oxidize sulfides by thermophilic archaeon Acidianus brierleyi and then to decompose carbonaceous matters using the cell-free spent medium (CFSM) from white-rot fungus Phanerochaete chrysosporium. The pretreatment by A. brierleyi significantly improved the gold recovery from 25% to 77%. Additionally, the crude lignin-degrading enzymes in the CFSM converted the carbonaceous matters into more easily degradable substances, which were removed by alkaline washing, leading to a final gold recovery of 92%. These mineralogical alterations were confirmed by differential thermogravimetric analysis and quantitative evaluation of minerals with scanning electron microscopy. Based on the results, gold grains were mostly liberated after bio-oxidation of sulfides, and in following CFSM treatment, large particles of carbonaceous aluminosilicate were formed from the aggregation of clay minerals, gold grains and with partially decomposed carbonaceous matters acting as binders.

Sequential treatment was applied to carbonaceous Au-Ag-bearing ore concentrate to maximize the Au and Ag recovery. In the preliminary test, the present carbonaceous ore had well liberated and exposed type of gold grains, which are not refractory, but included mainly three types of Ag presented as electrum, hessite (Ag2Te) and Ag-bearing other minerals. Au recovery was ∼100% without any treatment, meanwhile Ag recovery was only 33.3%. The sequential treatment comprises two oxidation steps: (a) mixed culture of iron- and sulfur-oxidizing microorganisms at pH 1.2, followed by (b) cell-free spent medium (CFSM) at pH 4.0 from a white rot-fungus, Phanerochaete chrysosporium, which includes lignin-degrading enzymes. As a result, Ag recovery was 55.5% after the first step and greatly improved to ∼100%, including the dissolved Ag+ concentration in the first step of acid treatment. Although the acidophilic iron-oxidizing microorganisms were inhibited by dissolved Ag+ and Cd2+ ions, the strong acidic conditions dissolved hessite and Ag-bearing oxide minerals. However, the remaining carbonaceous matter acted to sorb Ag(CN)2− in cyanidation, causing the recovery loss. In the next step the lignin-degrading enzymes degraded carbonaceous matter in the ore. This step is necessary to avoid the adsorption of Ag(CN)2− on graphitic carbonaceous matter, leading a mostly perfect recovery of the remaining Ag in the solid residues, without necessity of alkaline washing. The sequential treatment including enzymatic lignin-degrading process was also effective in carbonaceous silver ore avoiding the emission of air pollutants.

Carbonaceous matter in refractory gold ore is known to be one of the primary causes of gold recovery loss. Model experiments were conducted to simulate the bio-modification of carbonaceous matter using powdered activated carbon (PAC) as a surrogate and cell-free spent medium (CFSM) of Phanerochaete chrysosporium. The CFSM was used because of the lignin peroxidase and manganese peroxidase secreted by the microbe during its incubation. In the present work, an investigation was conducted to determine the physical and chemical alterations in PAC after enzymatic treatment and its effect on Au(CN)2− uptake. Characterization of the solid residues of PAC by 13C NMR and N2 adsorption after bio-modification revealed that the treatment had decomposed poly-aromatic carbons into aliphatic carbons and also reduced the specific surface area from 1430 m2/g to 697 m2/g in 14 days. As a result, Au(CN)2− uptake decreased from 100% (0.048 mmol/g) to 43% within 12 h primarily due to the enzyme treatment and adsorption of CFSM components. It further decreased to 26% due to surface passivation by bio-chemicals derived from CFSM and/or decomposed aliphatic hydrocarbons from aromatic carbons between 7 days and 14 days. These findings may contribute to efforts to decrease preg-robbing in hydrometallurgical processing of refractory gold ores.

The detailed mechanism behind the bio-decomposition of carbonaceous matter in refractroy goold ore byPhanerocheate chrysosporiumto facilitate improved cyanidation of gold is as yet undersdtood. To gain a better understanding of this mechanism, the present work model experiments using powdery activated carbon (PAC) and cell-free extracts ofP.chrysosporiumto simulate and focus on the biotransformation of carbonaceous matters in refractory gold ores. The results of solid characterization using SEM and XRD indicated a more non-uniform surface and smaller crystal sizes for PAC treaded with cell-free extracts for 72 hours. The significant decomposition of aromatic compounds into aliphatic compounds were observed in13C-NMR and FTIR results for the high ratio of cell-free extract volume to mass of PAC. This results support the theory that one of the fundamental mechanisms behind the bio-decomposition process is aromatic bond cleavage by biomolecules produced byP.chrysosporium.

Sulfides and carbonaceous matter in double refractory gold ore (DRGO) were bio-treated sequentially using an iron-oxidizing archaeon Acidianus brierleyi followed by lignin peroxidase-dominating crude enzymes released from the white-rot fungus Phanerochaete chrysosporium to significantly improve gold recovery from 24% to 92%. Transformation of the carbonaceous matter in the sequential bio-treatment was interpreted with Quantitative Evaluation of Materials by Scanning Electron Microscopy (QEMSCAN), Raman spectroscopy and three-dimensional fluorescence spectrometry. Firstly, microbiological sulfide oxidation did not affect carbonaceous matter but decreased the arsenic content in the solid residue, facilitating the following enzymatic reaction. Next, the crude enzymes predominantly decomposed the defect-bearing graphitic carbon into humic-like substances. The humic-like substances were not completely soluble under pH 4 but were instead retained in the solid residue as a part of a newly formed carbonaceous aluminosilicate (C–Si–Al) phase. Due to a wide pKa range of humic-like substances, it is proposed that at pH 4, electrostatic interaction between humic substances and illite, with and without heavy metals, might have enabled the agglomeration of fine aluminosilicate particles. Some gold grains trapped in C–Si–Al agglomerates were released by the dissolution of humic-like substances in 1 M NaOH, resulting in a further increase in gold recovery of approximately 15%.

The idea of attaching moral depravity to the fall of the tragic heroes (according to Aristotle, those men who enjoy prosperity and high reputation like Oedipus and Thyestes etc.) did not start with the three tragic poets, namely; Aeschylus, Sophocles and Euripides, but rather it dates back even to Homer. This idea is, of course, influenced by the old Greek tradition of Koros, Hubris, Nemesis and Ate. The totality of this traditional view and its application is equated to the phrase ‘hubristic principle’, in the scheme of this work. The hubristic principle makes specific that the fall of the hero is as a result of a sin or wrong that he committed. The commission of this wrong must not go unpunished. In effect, the hand of Justice, what they call nemesis, no matter how delayed must fall on the hero. The problem is how then do you reconcile situations where the fall of the hero is not his making? In other words, where do you place undeserved misfortune that befalls the hero? Apparently, it is this inadequacy of the hubristic syndrome that Aristotle proposes hamartia (Greek, for error) as the appropriate means in accounting for the fall of the tragic hero. This paper discusses first, the hubristic principle and its application and second, assesses the reliability of the theory in accounting for the fall of the tragic hero.