Biomodulation of mineral surfaces for selective separation of pyrite from chalcopyrite: a ftir study

This paper discusses the utility of FTIR spectra in understanding the mechanism of selective separation of chalcopyrite from pyrite after biomodulation using Acidithiobacillus ferrooxidans cells. Consequent to interaction with bacterial cells, pyrite remained depressed even in presence of collector while chalcopyrite exhibited significant flotability. FTIR spectra indicated that the major species formed when pyrite and chalcopyrite were interacted with an aqueous solution of potassium ethyl xanthate was dixanthogen and copper (I)alkyl xanthate respectively. The observed difference in the flotability of the two minerals after interaction with the cells and collector is explained based on FTIR studies

Surface chemical and flotation behaviour of chalcopyrite and pyrite in the presence of Acidithiobacillus thiooxidans

Extraction of valuable metals and removal of sulfide minerals from abandoned mines holds the key for environmental protection. This paper discusses the utility of Acidithiobacillus thiooxidans for the selective removal of pyrite from chalcopyrite for the economic extraction of valuable copper. Interaction of bacterial cells with the sulfide minerals altered the surface chemistry of both the minerals and cells. The isoelectric point of both pyrite and chalcopyrite shifted to higher pH after interaction with cells. Adhesion kinetics of the bacterial cells to both the minerals was similar, however, the adsorption density on pyrite was higher compared to that on chalcopyrite. Interaction with cells rendered both the minerals hydrophilic. Flotation of minerals, preconditioned with cells, with potassium isopropyl xanthate as collector resulted in depression of pyrite and good flotation of chalcopyrite. The observed behaviour is discussed in detail. Poor selectivity achieved when the minerals were floated together was overcome by conditioning the collector interacted minerals with the bacterial cells prior to flotation. Thus it was possible to selectively depress pyrite from chalcopyrite at both acidic and neutral pH conditions

Catechin, epicatechin, curcumin, garlic, pomegranate peel and neem extracts of Indian origin showed enhanced anti-inflammatory potential in human primary acute and chronic wound derived fibroblasts by decreasing TGF-β and TNF-α expression

Abstract Background Although chronic wounds are devastating and can cause burden at multiple levels, chronic wound research is still far behind. Chronic wound treatment is often less efficient due to delay in diagnosis and treatment, non-specific treatment mainly due to lack of knowledge of wound healing or healing resistance genes. It’s known that chronic wounds do not progress towards healing, because it gets stalled in inflammatory phase of wound healing. Objective We aimed to use phytoextracts possessing excellent anti-inflammatory properties to regulate the unbalanced levels of cytokines responsible for increased inflammation. Methods Evaluation of anti-inflammatory activity of selected phytoextracts namely, Camellia sinensis (L.) Kuntze, Acacia catechu (L.f) Willd., Curcuma longa (L.), Allium sativum (L.), Punica granatum (L.) and Azadirachta indica A. hereafter, called as catechin, epicatechin, curcumin, garlic, pomegranate and neem extracts, respectively in Acute wound fibroblasts (AWFs) and Chronic wound fibroblasts (CWFs) using flow cytometry. Results The phytoextracts exhibited no cytotoxicity below 100 μg/ml on normal Human Dermal fibroblasts (HDFs), while garlic extract showed highest cell viability followed by catechin, epicatechin, curcumin, pomegranate peel and neem based on IC50 value. Garlic, catechin and epicatechin extracts showed highest anti-inflammatory activities for both TGF-β and TNF-α in both AWFs and CWFs treated cells. After treatment of AWFs with catechin, epicatechin and garlic extracts, TGF-β and TNF-α expression was significantly reduced compared to untreated AWFs and reached to almost normal HDFs level. Also, after treatment of CWFs with catechin, epicatechin and garlic extracts, TGF-β and TNF-α expression was significantly reduced compared to untreated CWFs and was lesser than untreated AWFs. Conclusion The present findings reveal the potential of catechin, epicatechin and garlic extracts for the treatment of acute and chronic wounds with excellent anti-inflammatory properties

Microbially-induced separation of arsenopyrite and bioremediation of arsenic

This paper discusses the role of the mineral-adapted acidiphilic microorganism Acidithiobacillus ferrooxidans in the beneficiation of arsenopyrite-containing multisulfides (pyrite and chalcopyrite) and the bioremediation of the resulting arsenical waste water. It was found that adaptation to minerals alters the surface properties of the microorganism. Bacterial adaptation to arsenopyrite and controlled bacterial adhesion to mineral surfaces lead to selectivity in arsenopyrite separation. Bioremoval of arsenic ions (both arsenite and arsenate ions) by Acidithiobacillus ferrooxidans is also discussed

Imaging of acidithiobacillus ferrooxidans by AFM and analysis of AFM curves

The aim of the present investigation is to obtain tapping mode images of Acidithiobacillus ferrooxidans and interfacial forces between Acidithiobacillus ferrooxidans cells and silicon nitride tip of AFM. The effect of exposure of cells to toxic metal ions like arsenic on the morphology of the cells was investigated by the section analysis of the AFM images obtained. Effect of glutaraldehyde fixation on force curves is also analyzed

Mechanism of arsenic tolerance and bioremoval of arsenic by Acidithiobacilus ferrooxidans

This paper reports the studies on mechanism of arsenic tolerance and bioremoval of arsenic ions (arsenite or arsenate) by Acidithiobacillus ferrooxidans. Exposure of cells to arsenic ions resulted in increased cell surface hydrophobicity, decreased electrophoretic mobility and stronger adsorption affinity towards arsenopyrite. The mechanism of tolerance to arsenic ions were specific and could be attributed to the changes in specific protein expression in the outer membrane and cytosolic membrane fractions. Biosorption studies showed decrease in solution arsenic concentration only with ferrous–grown cells indicating that presence of ferric ions in the EPS was necessary for binding or entrapment of arsenic ions in the EPS. Bacterial EPS of ferrous–grown wild cells were able to uptake arsenate ions due to the strong affinity of ferric ions towards arsenate ions. Neither cells nor the ferric ions were capable of precipitating or oxidizing arsenite ions directly. Both arsenate ions and arsenite ions were co–precipitated with ferric ions formed during the growth of the bacteria

Soft-particle model analysis of effect of LPS on electrophoretic softness of Acidithiobacillus ferrooxidans grown in presence of different metal ions

The effect of surface lipopolysaccharides (LPS) on the electrophoretic softness and fixed charge density in the ion-penetrable layer of Acidithiobacillus ferrooxidans cells grown in presence of copper or arsenic ions have been discussed. The electrophoretic mobility data were analyzed using the soft-particle electrophoresis theory. Cell surface potentials of all the strains based on soft-particle theory were lower than those estimated using the conventional Smoluchowski theory. Exposure to metal ions increased the surface electrophoretic softness with decrease in the fixed charge density. Effect of cell surface lipopolysaccharides on the model parameters are investigated and discussed

Microbially induced mineral beneficiation

The divergent role of microbes in the field of mineral processing starting from mining and beneficiation to efficient waste disposal has been well recognized now. The roles of various microorganisms and bioreagents in the beneficiation of minerals are illustrated in this paper. Various types of microorganisms useful in bringing about selective flotation and flocculation of various oxide and sulfide minerals are illustrated. Interfacial phenomena governing microbe-mineral interactions are discussed with reference to bacterial cell wall architecture, cell surface hydrophobicity, electrokinetic data, and adsorption behavior on various minerals. Applications of microbially induced mineral beneficiation are demonstrated with respect to beneficiation of iron ores, bauxite, limestone, and complex multimetal sulfides

Selective separation of pyrite and chalcopyrite by biomodulation

Selective separation of pyrite from other associated ferrous sulphides at acidic and neutral pH has been a challenging problem. This paper discusses the utility of Acidithiobacillus ferrooxidans for the selective flotation of chalcopyrite from pyrite. Consequent to interaction with bacterial cells, pyrite remained depressed even in the presence of potassium isopropyl xanthate collector while chalcopyrite exhibited significant flotability. However, when the minerals were conditioned together, the selectivity achieved was poor due to the activation of pyrite surface by the copper ions in solution. The selectivity was improved when the sequence of conditioning with bacterial cells and collector was reversed, since the bacterial cells were able to depress collector interacted pyrite effectively, while having negligible effect on chalcopyrite. The observed behaviour is analysed and discussed in detail. The separation obtained was significant both at acidic and alkaline pH. This selectivity achieved was retained when the minerals were interacted with both bacterial cells and collector simultaneously