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The present work deals with the use of iron/sulfur-oxidizing bacterium Acidithiobacillus ferrooxidans for the desulfurization of a coal sample from Assam, India. The coal sample contains 3.87% w/w ...

New Plate Mill (NPM), a state of the art facility has been commissioned at Rourkela Steel Plant (RSP). Facilities like roll bending, roll shifting and plan view rolling are integral part of the mill. High pressure de-scaling, accelerated cooling control (ACC) with high capacity hot plate leveller (HPL) & cold plate leveller (CPL) are other process facilities of the NPM. A special feature of the NPM (New Plate Mill) is its high roll separating force of 90MN. This enables high shape factor rolling that leads to the rolling of metallurgically sound thicker steel plate. Therefore it is possible to apply modern thermo-mechanically processing routes for the development of tailor made properties like high strength, toughness, close dimensional tolerance and excellent surface finish in plate. Trials were carried out for the achieving target mechanical properties with leaner chemistry by thermo-mechanical control processing (TMCP). After rolling, plates are passed through the Accelerated Cooling Control (ACC) unit for achieving desired mechanical properties. After ACC, waviness is visible in the plates and hence HPL is used for flattened the plate profile. Plates get flattened after hot plate leveling but after several minutes some waviness again occurs in the plates on the cooling bed. Initially several factors were considered for possible reason and thermal images of the plates were taken for understanding thermal variations in the plates. Finally, improper descaling and temperature inhomogeneity was found major factors affecting plates shape.

Dissimilatory Iron Reducing Bacteria (DIRB) in specific has found wide range of application in bio-beneficiation for removal of iron impurities from different ores and in bioremediation for detoxification of heavy metals, hazardous pollutants, etc. Numerous research works have been reported for bio-beneficiation of kaolin, bauxite by IRB. This study aims at studying effect of anaerobic dissimilatory iron (III) reducing bacterial consortium on different phases of iron present in lateritic nickel ore. Such conversion in lateritic nickel ore is helpful in better recovery of sorbed metal values like Ni and Co by subsequent bioleaching or acid leaching. Over the past decade, the global demand-supply chain of nickel is constrained due to depletion of sulphidic nickel ores. However, with anticipated boom in electric vehicles (EVs), the forthcoming decade for battery demand is very bullish for nickel. Hence, there is an urgent need to extract nickel from lateritic nickel ores to meet its high demand. Application of conventional methods for nickel extraction from lateritic ores is challenging from metallurgical and technical viewpoint and requires high capital investments. There is ongoing search for alternative nickel extraction methods from lateritic ores to meet the high nickel demand loom. In India, nickel metal is concentrated in the Chromite overburden (COB) dumps of Sukinda Valley Jajpur, Odisha. The nickel metal is ingrained within the stable goethite matrix (oxidic mineral phase) which requires stringent actions (high energy and/or chemical attack) for its dissociation. 70% Ni and 81% Co was recovered on acid-leaching of DIRB-treated ore whereas only 54% Ni and 57% Co was recovered on acid leaching of untreated COB Hence, pre-treatment of COB with DIRB can enhance the recovery of nickel. Exploitation of competent indigenous microorganisms can thus formulate an eco-friendly approach for nickel extraction. This work discusses the various aspects of microbial application for nickel recovery from lateritic nickel ores.

Halophiles have been used as bioremediation agents in degradation of organic pollutants and acidophilic microorganisms are considered as efficient metal leaching agents for mineral-metal bearing wastes. In the present study, halophilic bacteria (Bacillus tequilensis CH) and a mixed culture of acidophilic bacteria were used for their visual detection over fluorescence microscope. With regards to B. tequilensis CH, bacterial presence and its biofilm formation was studied over glass cover slips; while for the acidophilic culture, comparisons were made to observe bacterial presence over glass cover slips and a sample ore surface. It was observed that for both the microbial cultures, green fluorescence was detected at different magnifications for the bacteria as well as the biofilm formed (better visualization in case of B. tequilensis); thus, confirming the adsorption of calcein-AM dye by the live bacterial cells. Furthermore, the 3D intensity plots, in case of the acidophiles, confirmed the presence of bacterial clusters and a possible formation of bacterial biofilm over the sample ore surface.

Mineralogically distinct coal samples respond differently to microbial attack. In the present study, a mixed meso-acidophilic bacterial consortium predominantly comprising of Acidithiobacillus ferrooxidans strain was investigated for its biodesulphurization abilities for three distinct sulphur bearing samples (Goa CPC, Rajasthan Lignite, Assam Coal) of Indian origin in iron (9K+) and iron-free (9K−) media. A media devoid of Fe (II) iron was more effective for sulphur removal with maximum desulphurization of 45.19% for Assam coal followed by 36.8% for Rajasthan Lignite and 23.38% for CPC respectively. The proximate analysis, FTIR patterns and XRD analysis of the samples provided better insights into understanding the mineralogical and compositional changes in the coal matrix. Owing to the higher efficiency, Assam coal was additionally subjected to further optimization studies and characterization of the treated coal through TGA. The study indicated that the gross calorific values for all the samples increased following microbial treatment in 9K− media thereby providing a scope for further scale-up studies.

The present study describes anoxic Mn bioleaching of low grade ferromanganese ores using a dissimilatory Mn reducing consortia (MRC). Effect of external addition of electron shuttles such as humic acid and anthraquinone sulphonic acid was studied under same conditions. The MRC were found to be capable of utilizing MnO2 as electron acceptor as evidenced by Mn dissolution in media. In the presence of electron shuttles, Mn extraction was found to be enhanced by 2 to 4 times compared to the case without. A maximum of 58 (±3%) Mn was found to be leached from an amorphous ore while 38 (±2%) Mn was leached from a crystalline ore, in 50 days in presence of 100 μM electron shuttle at 20 g/L S:L ratio. A significant finding was consistently low leaching of Fe under all conditions studied (

The ungenerous release of metals from different industrial, agricultural, and anthropogenic sources has resulted in heavy metal pollution. Metals with a density larger than 5 g cm−3 have been termed as heavy metals and have been stated to be potentially toxic to human and animals. Algae are known to be pioneer organisms with the potential to grow under extreme conditions including heavy metal-polluted sites. They have evolved efficient defense strategies to combat the toxic effects exerted by heavy metal ions. Most of the algal strains are reported to accumulate elevated metal ion concentration in cellular organelles. With respect to that, this review focuses on understanding the various strategies used by algal system for heavy metal resistance. Additionally, the application of this metal resistance in biosynthesis of metal nanoparticles and metal oxide nanoparticles has been investigated in details. We thereby conclude that algae serve as an excellent system for understanding metal uptake and accumulation. This thereby assists in the design and development of low-cost approaches for large-scale synthesis of nanoparticles and bioremediation approach, providing ample opportunities for future work.

A study was conducted in duck population of Nepal from August-2013 to March-2014 as to find out the seroprevalence of Low pathogenic Avian Influenza (LPAI) subtype H9. Altogether 300 blood samples were taken from avian influenza risk areas of Nepal by using purposive sampling method and were analyzed in virology laboratory, Animal Health Research Division, NARC, Khumaltar. The serum samples were processed for Haemagglutination Inhibition (HI). Of the 300 serum samples, 16 samples showed HI positive (at>3rd well) at two-fold dilution revealing revealing 5% Seroprevalence of LPAI H9 and overall average antibody titre 6.27. The seroprevalences of six districts were found to be Chitwan (10%), Sunsari (6%), Kathmandu (2%), Banke (8%), Bhaktapur (2%) and Jhapa (4%) with their mean antibody titres in log form were found to be 6.8, 6.3, 5, 6, 6 and 6.5 respectively. These samples when categorised into three divisions of influenza risk areas viz. Buffer zone, Border market area and Outbreak area, the seroprevalence were found to be 8%, 6% and 2% and their mean antibody titre in log2 form were found to be 6.6, 6.3 and 5.5 respectively. The statistical analyses revealed that there is significant difference (P0.05) occurred in prevalence by district, sex and influenza risk area.

In this study, we have demonstrated an integrated approach for utilization of microalga Scenedesmus sp. for fabrication of catalytic and antimicrobial silver nanoparticle composite. The algal biomass was harvested from an open raceway pond of 30,000 L scale used for CO2 sequestration. The dried biomass served as a green, nontoxic, reducing and immobilizing agent for synthesis of silver nanoparticles, producing biomass-silver nanoparticle composite. ICP-OES was used to monitor the uptake of silver ions by biomass and subsequent formation of nanoparticles. The composite was calcined at 400 °C to fix the nanoparticles and prevent fouling. The calcined biomass-silver nanoparticle (CB-AgNP) composite was characterized using FESEM-EDAX, XRD and TGA. The CB-AgNP composite was used for the first time, as a heterogenous catalyst for reduction of a prominent industrial pollutant, p-nitrophenol. The reduction was carried out in the presence of NaBH4 in aqueous medium under ambient conditions. Batch experiments were conducted to evaluate the effect of calcination temperature, load of material and its reusability, on the catalytic efficiency of material. It was found that as low as 5 mg mL−1 CB-AgNP material reduced more than 80% and 95% of p-nitrophenol within 1 min and 15 min of exposure, respectively. Rate of PNP reduction was 0.60 mg L−1 min−1. The composite was easily recovered and reused for continuous batches of p-nitrophenol reduction. The efficiency of catalysis decreased with ten cycles of reuse; however, with an intermittent overnight water wash, the material regained its catalytic activity. Furthermore, the CB-AgNP composite also possessed excellent antimicrobial activity against pathogenic microbes. Two strains each of gram + ve and gram − ve bacteria and three strains of pathogenic fungi were used in the antimicrobial studies using well diffusion method and it was found to be active against all the microbes. The CB-AgNP composite is a potential candidate for a reusable heterogenous catalyst for designing continuous flow system for remediation of industrial effluents rich in p-nitrophenol. Its efficacy against common pathogenic bacteria and fungi can be harnessed for simultaneous antimicrobial treatment of the water. Moreover, this antimicrobial property will further inhibit the biofouling and eventual clogging of the material used in a packed column when used for water treatment.

The most adverse outcome of increasing industrialization is contamination of the ecosystem with heavy metals. Toxic heavy metals possess a deleterious effect on all forms of biota; however, they affect the microbial system directly. These heavy metals form complexes with the microbial system by forming covalent and ionic bonds and affecting them at the cellular level and biochemical and molecular levels, ultimately leading to mutation affecting the microbial population. Microbes, in turn, have developed efficient resistance mechanisms to cope with metal toxicity. This review focuses on the vital tolerance mechanisms employed by the fungus to resist the toxicity caused by heavy metals. The tolerance mechanisms have been basically categorized into biosorption, bioaccumulation, biotransformation, and efflux of metal ions. The mechanisms of tolerance to some toxic metals as copper, arsenic, zinc, cadmium, and nickel have been discussed. The article summarizes and provides a detailed illustration of the tolerance means with specific examples in each case. Exposure of metals to fungal cells leads to a response that may lead to the formation of metal nanoparticles to overcome the toxicity by immobilization in less toxic forms. Therefore, fungal-mediated green synthesis of metal nanoparticles, their mechanism of synthesis, and applications have also been discussed. An understanding of how fungus resists metal toxicity can provide insights into the development of adaption techniques and methodologies for detoxification and removal of metals from the environment.

In this study, we report a novel application of valine-capped gold nanoparticles for colorimetric and visual detection of lead ions. The –COO− group of the hydrophobic valine molecules present efficient electrostatic repulsion resulting in generation of stable, well-dispersed and size-controlled GNPs. The GNPs were highly selective for Pb2+ ions and showed visible colour change in the assay mixture on addition of solution containing lead ions. Interestingly, a decrease in the intensity of original SPR peak at 530 nm was observed, with concomitant appearance of a new peak at longer wavelength due to agglomerated GNPs. The free –COO− groups on GNP surface interacted with Pb2+ and ion-dependent chelation mechanism lead to cross-linking of particles and subsequent agglomeration. Binding of Pb2+ ions and valine-capped GNPs occur in a stochiometric ratio of 1:2. The GNPs displayed colorimetric sensing in the range of 0 to 100 ppm concentration with a very high selectivity towards lead even in the presence of other metal ions. The minimum detection limit (MDL) for Pb2+ was 30.5 µM. We anticipate that these valine-capped GNPs may be employed for lead detection in polluted water/wastewater through a cost-efficient, one-step assay protocol as it does not require additional functionalization with specific ligand molecules.

A native isolate, 9C, identified as Rhodococcus ruber (Genbank Accession number – KY029073) was studied for dibenzothiophene degradation and subsequent bio-desulphurization of three different sulphur bearing materials (NE coal containing organic sulphur; lignite containing pyritic sulphur and a calcined petroleum-coke) of Indian origin. The isolate could degrade 0.25 mM DBT through the 4S pathway within 7 days. Preliminary studies for sulphur removal using the 9C isolate indicated NE coal to be more amenable (29% sulphur removal) followed by Lignite (15.87%) and CPC (14.83%) respectively. Characterization through XRD and FTIR along with the proximate and ultimate analysis of all the samples provided more insights into the changes in calorific values as well as the chemical constitution of the samples following microbial treatment. Owing to the amenability of NE coal, the effect of time, size fraction and pulp density were optimized. The best bio-desulphurization conditions for NE coal indicated 36% total sulphur removal (organic–53%, pyritic–18% and sulphate sulphur–14% respectively). Analytical characterization studies confirmed that the energy value of the NE coal was not affected due to biodesulphurization, rather it contributed towards an increase in gross calorific value from 6698 cal/g to 6812 cal/g following microbial treatment.

Rapid and high precision detection of toxic metal ions is one of the chief requirements today to combat environment pollution. Gold nanoparticles play a key role in this by assisting the development of smart sensors and detection agents. Their high surface to volume ratio and unique optical property facilitates the development of high sensitive analytical GNP based bio-sensing tools. Recently, a major research thrust area has been the design and development of smartly fabricated GNPs as probes for selective detection of toxic contaminates and metal pollutants. In this review we focus on the use of GNPs and its functionalization for colorimetric detection of metal ions. Colorimetric detection enables cost effective and simple monitoring of toxic ions accompanied with the advantages of on-site applicability, avoids complex instrumentation, ease of analysis and usage. We also discuss the promising prospects and future potentiality of GNPs to serve as next generation multi-functional sensing tools and “lab-on-chip” detection agents.

In the present study selective iron-free extraction of Cu, Ni, Co and Mn from Indian Ocean manganese nodules by manganese reducing consortium is described. The consortium isolated from manganese ore mines of Joda, Odisha (India) and enriched with Indian Ocean manganese nodules was used for bioleaching under facultative anaerobic conditions in mineral salt media using organic carbon source. Bioleaching was carried out at 30 °C without agitation. Recoveries of Mn, Ni and Co increased with time, while maximum Cu recovery occurred during the initial period followed by a decrease. A notable finding was that Fe dissolution remained extremely low, i.e. less than 42 mgL − 1 (3.0%), possibly due to in situ precipitation of iron. X-ray diffraction patterns of bioleach residues indicated formation of FePO 4 and MnCO 3 phases. Iron dissolution remained consistently low even with increasing pulp density and decreasing particle size. The Mn reducing consortia may thus help in selective leaching of Mn while preventing Fe from contaminating the leach liquor, which is desirable in downstream processing of metal production from Mn-nodule and ferromanganese ores.

In the current era, the alarming rate at which coal is being burned as a fuel is causing concern with regard to the release of sulphur oxides. According to reports, global coal consumption has increased by 0.4% in 2014. While countries like UK, Ukraine etc. have witnessed a decline in coal consumption, some others like India, China, Africa and North America have increased their use of coal to meet the energy requirements of the growing human population. The increasing use of coal has led to extensive investigations for finding an ecofriendly clean coal technology. Dibenzothiophene (DBT) and some of its alkylated derivatives present in the form of organic sulphur in coal have received a great deal of attention in the past few years because of their recalcitrant nature. Considering the economic and environmental prospects, biodesulphurization is being regarded as an effective tool for the degradation of DBT, with concomitant application towards sulphur removal from coal. Owing to the importance of microbial applications towards production of clean coal, the present review discusses some of the recent findings in the area of DBT biodegradation. In addition, current advances in coal biodesulphurization are reviewed, concluding with a consideration of future prospects for the rapidly growing energy sector.

Two ore samples, one obtained from a partially leached heap with suspended operations for about four years and the other through sonic drilling of a discarded dump were tested for the amenability/feasibility of copper extraction through reactor and column leaching. Mineralogical analysis of the samples indicated the dominant sulphide minerals to be chalcopyrite and pyrite. Various process parameters such as the effect of acid concentration, time, oxidant, pulverization and temperature were studied for the reactor leaching experiments. A maximum of 91% Cu extraction can be achieved while leaching the pulverized sonic drilled sample at 90 °C for 3 h. On the other hand, column leaching studies at 1 kg scale showed 65–70% Cu extraction with an acid concentration of 2.7% (v/v) for both the samples. Sequential leaching of the chemically leached residues of both sonic drilled and heap leached pad sample yielded additional 13.2% and 22.2% Cu, respectively in 20 days of bacterial leaching using a mixed culture of meso-acidophilic bacterial consortium. Column leaching studies showed that the heap leached pad sample was more amenable to leaching than the sonic drilled one. Further, during the downstream processing of the leach liquors, the solvent extraction efficiency was about 95% and the Cu metal deposited by electrowinning was of 99.9% purity. A tentative process flowsheet for the recovery of copper was also prepared.

Chalcopyrite is the primary copper mineral used for production of copper metal. Today, as a result of rapid industrialization, there has been enormous demand to profitably process the low grade chalcopyrite and “dirty” concentrates through bioleaching. In the current scenario, heap bioleaching is the most advanced and preferred eco-friendly technology for processing of low grade, uneconomic/difficult-to-enrich ores for copper extraction. This paper reviews the current status of chalcopyrite bioleaching. Advanced information with the attempts made for understanding the diversity of bioleaching microorganisms; role of OMICs based research for future applications to industrial sectors and chemical/microbial aspects of chalcopyrite bioleaching is discussed. Additionally, the current progress made to overcome the problems of passivation as seen in chalcopyrite bioleaching systems have been conversed. Furthermore, advances in the designing of heap bioleaching plant along with microbial and environmental factors of importance have been reviewed with conclusions into the future prospects of chalcopyrite bioleaching.

Silver nanoparticles are produced by a novel biosynthesis technique using fungus Penicillium purpurogenum NPMF (MTCC 7356). The biomass when subjected to heat treatment up to 700 °C produces the nanoparticles of silver due to the presence of free carbon which acts as encapsulation for silver nanoparticles. Increase in temperature above 700 °C causes a reduction in concentration of free carbon so that the nanoparticles come close to each other and form clusters in the shape of tetrapods to polypods. The micro-Raman analysis supports the formation of mesoporous carbon with increase in the calcined temperature. The formation of Ag nanostructures has been explained in terms of free energy diagram i.e., the crystal favors more to grow on (100) facet or (110) facet rather than on (111) facet by the addition of silver atoms and thereby, it releases more energy. The release of energy has been confirmed from the differential thermo gravimetric analysis. In fact, it is the dynamics of the minimization of the free energy of the system which governs the reorientation and rearrangement of Ag themselves leading to formation of various types of polypods. A formation mechanism is presented schematically.

Bacillus tequilensis strain CH had been previously shown to produce a biosurfactant. In this study, chemical structure of the purified biosurfactant was determined by using high performance liquid chromatography and liquid chromatography-mass spectroscopy as a 10 amino acid cyclic lipopeptide (CL). The cyclic lipopeptide was found to be active against Anopheles culicifacies larvae with a LC50 of 110 µg/ml in 2 days. 1 ppm cadmium (Cd) which had a profound mutagenic effect on the cell division of onion (Allium cepa) root tip cell resulting in abnormal metaphase, abnormal anaphase and nuclei elongation was partially reversed in the presence of 0.1 mg/ml of CL (52% cells dividing normally and 8% with abnormal division) and was comparable to control experiment where no Cd was present. Thus, the CL described in this report may have applications in eliminating larvae from water repository systems and in reversing the effects of cadmium pollution.

Since the sulfur specific cleavage is vital for the organic sulfur removal from fossil fuel, we explored potential bacterial strains of MTCC (Microbial Type Culture Collection) to desulfurize the Dibenzothiophene (DBT) through C-S bond cleavage (4-S pathway). MTCC strains Rhodococcus rhodochrous (3552), Arthrobacter sulfureus (3332), Gordonia rubropertincta (289), and Rhodococcus erythropolis (3951) capable of growing in 0.5 mM DBT were examined for their desulfurization ability. The presence of dsz genes as well as the metabolites was screened by polymerase chain reaction (PCR) and HPLC, respectively. All these strains showed > 99% DBT desulfurization with 10 days of incubation in minimal salt medium. From the HPLC analysis it was further revealed that these MTCC strains show differences in the end metabolites and desulfurize DBT differently following a variation in the regular 4-S pathway. These findings are also well corroborating with their respective organization of dszABC operons and their relative abundance. The above MTCC strains are capable of desulfurizing DBT efficiently and hence can be explored for biodesulfurization of petrochemicals and coal with an eco-friendly and energy economical process.

Microalgae are unicellular to multicellular simple autotrophic organisms with simple growth requirements like light, carbon dioxide, nitrogen, phosphorous, and potassium present dissolved in their aqueous ecosystem. During the course of their growth, they intake these elements present in a different compound form in the water system. This makes them beneficial for removal of such moieties from wastewater where these are present in high amount as pollutants and may cause havoc to the natural ecosystem if released untreated. In this chapter, we have discussed algae with respect to their properties related to uptake of carbon dioxide from flue gas as well as nitrogen and heavy metal from the wastewater. We have also discussed few systems where different algae are used in conjunction with or without bacteria for increasing the efficiency of waste treatment. Few pilot-scale studies used for wastewater remediation are also discussed.

Dumping of poor but metal containing industrial waste is associated with several environmental issues. Exposure of these wastes to the natural environment offers serious concerns for the mineral processing industries to utilize them for metal recovery and check environmental pollution. In the present study, a novel sequential bioreduction–bioleaching and bioreduction–chemical leaching route as a hybrid process is compared and discussed for the enhanced recovery of copper from an industrial concentrator plant ball milling unit rejected sample. A mixed consortium of metal reducing bacteria (DMRB) initially adapted to high Fe(III) concentrations was found to cause mineralogical/matrix alteration (possibly silicate weathering) including Fe(III) bioreduction in the sample and dissolute 29.73% copper during the first 35 days under facultative anaerobic conditions. Sequential leaching of the bioreduced waste sample (generated from the first step) using a mixed meso-acidophilic bacterial consortium predominantly Acidithiobacillus ferrooxidans showed additional 28.72% copper dissolution within 2 days using 1 gL − 1 Fe(II). On the other hand, a comparative chemical leaching of the same bioreduced sample using 0.5 M H 2 SO 4 yielded additional 32.17% copper within 4 days of leaching and indicated better performance than the bioleaching tests.

The ability of self-functionalized biogenic GNPs towards highly selective colorimetric detection of rare earth element cerium is being reported for the first time. GNPs underwent rapid aggregation on addition of cerium indicated by red shift of SPR peak followed by complete precipitation. Hereby, this concept of co-ordination of cerium ions onto the GNP surface has been utilized for detection of cerium. The remarkable capacity of GNPs to sensitively detect Ce without proves beneficial compared to previous reports of colorimetric sensing. MDL was 15 and 35 ppm by DLS and UV–vis spectroscopy respectively, suggesting DLS to be highly sensitive and a practical alternative in ultrasensitive detection studies. The sensing system showed a good linear fit favouring feasible detection of cerium in range of 2–50 ppm. Similar studies further showed the superior selectivity of biogenic GNPs compared to chemically synthesized counterparts. The sensing system favours on-site analysis as it overcomes need of complex instrumentation, lengthy protocols and surface modification of GNP.

The nickeliferous chromite overburden (COB) awaits a suitable technology to extract the obstinate nickel ingrained in its goethite matrix. In the present study, a novel Bio-Reduction Acid Leaching (BRAL) approach has been proposed using dissimilatory iron reducing bacteria (DIRB) which is inherently capable of transforming iron mineral phases via bio-reduction (BR). Mineralogical characterization of the bio-reduced COB using XRD and FTIR confirmed the phase transformation of goethite to hematite and magnetite with exposure of the nickel oxide peaks. Further, morphological characterization using FESEM vividly highlighted the changes of acicular goethite to granular magnetite deposits on the extra polymeric substance (a scaffold for electron transfer) secreted by DIRB consortium over the surface of COB. Further, enhanced nickel extraction was achieved with a reductive acid leaching (AL) approach with 6N sulfuric acid and 2% glucose ( reducing agent) at 65 degrees C for 6 h. A cumulative of 83.6% nickel was achieved through this BRAL approach. The pregnant leach solution (PLS) generated as a result of the AL approach was subjected to a hydrometallurgical route to recover metallic nickel. Solvent extraction (SX) of the PIS was performed using 0.5 M NaD2EHPA as extractant The pregnant nickel-loaded electrolyte was subjected to electrowinning (EW) to recover metallic nickel of 99.6% purity. The process flow-sheet is believed to provide a suitable eco-friendly, potential method to efficiently extract nickel from low grade nickel laterites to meet the ever growing demands caused by depletion of high grade nickel sulfidic ores. (C) 2015 Elsevier B.V. All rights reserved.

Dumping of low-grade chalcopyrite encompasses several environmental problems. Despite slow dissolution rate, meso-acidophilic bioleaching is preferred for the extraction of copper from such ores. In the present study, meso-acidophilic bioleaching of a low-grade chalcopyrite in the presence of an acid-processed waste newspaper (PWp) is discussed for the first time. The study illustrated a strong catalytic response of PWp with enhanced bio-recovery of copper from acid-conditioned chalcopyrite. A maximum of 99.13% copper recovery (0.36% Cu dissolution/day) was obtained in 6 days of bioleaching in the presence of 2 gL- 1 PWp in contrast to only 5.7% copper in its absence. FTIR analysis of bioleached residues revealed similar spectral patterns to the original acid-conditioned ore in the presence of PWp, thus indicating less development of passivation layer which was also confirmed through a complementary Raman characterization of the bioleached residues. Further, a reaction mechanism (chemistry) was proposed suggesting the possible role of PWp as the electron donor under oxygen limiting conditions which facilitated microbial reduction of Fe (III). The resulting biochemical changes provided an energy source for the bacteria, thus allowing free flow of electrons through the ore surface, thus contributing towards enhanced bioleaching of copper.

Copper slag was subjected to in-depth mineralogical characterization by integrated instrumental techniques and evaluated for the efficacy of physical beneficiation and mixed meso-acidophilic bioleaching tests towards recovery of copper. Point-to-point mineral chemistry of the copper slag is discussed in detail to give better insight into the association of copper in slag. Characterization studies of the representative sample revealed the presence of fayalite and magnetite along with metallic copper disseminated within the iron and silicate phases. Physical beneficiation of the feed slag (similar to 0.6% Cu) in a 2 L working volume flotation cell using sodium isopropyl xanthate resulted in Cu beneficiation up to 2-4% and final recovery within 42-46%. On the other hand, a mixed meso-acidophilic bacterial consortium comprised of a group of iron and/or sulfur oxidizing bacteria resulted in enhanced recovery of Cu (similar to 92-96%) from the slag sample. SEM characterization of the bioleached slag residue also showed massive coagulated texture with severe weathered structures. FE-SEM elemental mapping with EDS analysis indicated that the bioleached residues were devoid of copper.

Biological sequestration of cadmium (Cd) and retention of adsorbed cadmium as cadmium sulphide (CdS) nanoparticles inside the cell by a lipid-producing green algae Scenedesmus-24 is reported. The microalga was able to grow in the growth media containing 30 mg L−1 of cadmium without any growth inhibition. Adsorption of Cd(II) was dependent on the pH of the medium, initial concentration of cadmium, density of algal biomass (biosorbent dose), and contact time. The adsorption follows Langmuir isotherm pattern with an estimated maximum cadmium adsorption capacity at 50 mg g−1. The kinetics of adsorption followed Lagergren’s pseudo-second-order model. FTIR analysis revealed the presence of different functional groups on the algal biomass which may be responsible for adsorption of Cd(II). After adsorption, the bound metal ions were retained in the microalgal biomass as CdS nanoparticles. Presence of CdS nanoparticle was confirmed by XRD and TEM analysis. The results of the present study conclusively demonstrate that the microalga Scenedesmus-24 may be a promising candidate for sequestration of cadmium from cadmium polluted water and also its recovery as precious CdS nanoparticles.

Advances in applied and industrial microbial biotechnology have opened up many new avenues for application of several microorganisms. A group of certain metal reducers such as the dissimilatory iron reducing microorganisms possess an inherent potential to reduce oxidized metals under strict anaerobic/facultative anaerobic condition, thereby opening possibilities to combat environmental pollution. This unique property has invited researchers towards understanding the metabolic regulatory pathways that enables the microbes to thrive under extreme environmental conditions. Currently, dissimilatory iron reducing bacteria (DIRB) is in the focus of researchers to elucidate the specific mechanisms responsible for microbial metal reduction. The recent advances towards understanding the metabolism of iron reduction in Shewanella and Geobacter, the model DIRB has been covered in this review. It is believed that the metabolic insights into the Fe (III) reduction systems of the model DIRB; Shewanella and Geobacter (as discussed in the review) can be a basis for metabolic engineering to provide improved practical applications. With the advancement of our existing knowledge on the metabolic processes of the model iron reducers, applications ranging from laboratory to field scale practices can be carried out. DIRB has gained immense interest for its application in the field of bioremediation, electrobiosynthesis, and bioelectronics in this decade. It can therefore be anticipated that the forthcoming years will see more applications of microbial iron reducers based on the existing as well as advanced metabolic informations available in open source literature.

Bacillus tequilensis strain CH had been previously shown to produce a biosurfactant. In this study, chemical structure of the purified biosurfactant was determined by using high performance liquid chromatography and liquid chromatography-mass spectroscopy as a 10 amino acid cyclic lipopeptide (CL). The cyclic lipopeptide was found to be active against Anopheles culicifacies larvae with a LC(50) of 110 µg/ml in 2 days. 1 ppm cadmium (Cd) which had a profound mutagenic effect on the cell division of onion (Allium cepa) root tip cell resulting in abnormal metaphase, abnormal anaphase and nuclei elongation was partially reversed in the presence of 0.1 mg/ml of CL (52% cells dividing normally and 8% with abnormal division) and was comparable to control experiment where no Cd was present. Thus, the CL described in this report may have applications in eliminating larvae from water repository systems and in reversing the effects of cadmium pollution.

Coal collected from Meghalaya state situated in northeastern (NE) region of India contains about 6.17% total sulphur (4.7% organic) with a gross calorific value of 26,208 J/g. In the present study, the coal sample was subjected to biodesulphurization along with optimization of various process parameters using a bacteria isolated from the native coal mine site. The native bacterium was identified to be Sinomonas flava 1C and reported first time for the capability to remove about 40% of sulphur from the coal. An innovative two-step sequential leaching using S. flava 1C followed by Acidithiobacillus ferrooxidans was used in the present study to enhance desulphurization. Sequential leaching resulted in 50–53% of sulphur removal from the coal sample. Sequential leaching reduced the sulphur content to 3.08% (organic 2.15% + pyritic 0.1% and 0.85% of sulphate sulphur) in −500+300 μm size fraction of coal. Analytical characterization indicated that the energy value of coal was not affected adversely due to the biodesulphurization process rather its calorific value increased from 26,208 J/g to 29,481 J/g.

A biogenic route was adopted towards the synthesis of gold nanoparticles using the extract of a novel strain, Talaromyces flavus. Reduction of chloroauric acid by the fungal extract resulted in the production of gold nanoparticle, which was further confirmed by the concordant results obtained from UV–visible spectroscopy, energy dispersive spectroscopy (EDS), and dynamic light scattering (DLS) analysis. Morphology and the crystal nature of the synthesized nanoparticles were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD) and selected area electron diffraction (SAED). A direct correlation was observed between nanoparticle formation and the concentration of reducing agent present in the fungal extract. The time-dependent kinetic study revealed that the bioreduction process follows an autocatalytic reaction. Crystalline, irregular, and mostly flower-shaped gold nanoparticles with a mean hydrodynamic radius of 38.54 ± 10.34 nm were obtained. pH played a significant role on production of mono-dispersed nanoparticle. FTIR analysis partially deciphered the involvement of –NH2, −SH, and –CO groups as the probable molecules in the bio-reduction and stabilization process. Compared to the conventional methods, a time-resolved, green, and economically viable method for floral-shaped nanoparticle synthesis was developed.

Biosurfactants are amphiphilic molecules having hydrophobic and hydrophilic moieties produced by various microorganisms. These molecules trigger the reduction of surface tension or interfacial tension in liquids. A biosurfactant-producing halophile was isolated from Lake Chilika, a brackish water lake of Odisha, India (19°41'39″N, 85°18'24″E). The halophile was identified as Bacillus tequilensis CH by biochemical tests and 16S rRNA gene sequencing and assigned accession no. KC851857 by GenBank. The biosurfactant produced by B. tequilensis CH was partially characterized as a lipopeptide using thin-layer chromatography, Fourier transform infrared spectroscopy, and nuclear magnetic resonance techniques. The minimum effective concentration of a biosurfactant for inhibition of pathogenic biofilm (Escherichia coli and Streptococcus mutans) on hydrophilic and hydrophobic surfaces was found to be 50 μg ml(-1). This finding has potential for a variety of applications.

Meso-acidophilic bacterial leaching of ball mill spillage (containing chalcopyrite >80%) was carried out in an innovative two-step bioleaching method. The major drawback of meso-acidophilic bioleaching limiting industrial application is the passivation phenomenon over the ore surfaces in iron-sulfur rich environments. In the present study, we present a novel wash solution that efficiently removed the passivation layer. FTIR characterization of the bioleached sample indicated that the residues could be further leached to recover extra copper after wash solution application. XRD study indicated accumulation of sulfates (SO(4)(-)) of Na, K, Fe and oxy hydroxides of iron [FeO(OH)] in the form of jarosite outlining the passivation layer. SEM, FESEM-EDS studies indicated severe corrosion effects of the wash solution on the passivation layer. Two step bioleaching of the ore sample yielded 32.6% copper in 68days in the first interlude and post wash solution application yielded 10.8% additional copper.

Bioleaching of a low grade chalcopyrite (ball mill spillage material) was tested for copper recovery in shake flasks. The original samples (as received) were thermally activated (600°C, 30 min) to notice the change in physico-chemical and mineralogical characteristics of the host rock and subsequently its effect on copper recovery. A mixed culture of acidophilic chemolithotrophic bacterial consortium predominantly entailing Acidithiobacillus ferrooxidans strain was used for bioleaching studies and optimization of process parameters of both original and thermally activated samples. Mineralogical characterization studies indicated the presence of chalcopyrite, pyrite in the silicate matrix of the granitic rock. Field emission scanning electron microscopy coupled with Energy dispersive spectroscopy (FESEM-EDS) and X-ray Fluorescence (XRF) analysis indicated mostly SiO2. With pH 2, pulp density 10% w/v, inoculum 10% v/v, temperature 30°C, 150 r·min−1, 49% copper could be recovered in 30 days from the finest particle size (−1 + 0.75 mm) of the original spillage sample. Under similar conditions 95% copper could be recovered from the thermally activated sample with the same size fraction in 10 days. The study revealed that thermal activation leads to volume expansion in the rock with the development of cracks, micro and macro pores on its surface, thereby enabling bacterial solution to penetrate more easily into the body, facilitating enhanced copper dissolution.

Microbial extraction of nickel from lateritic chromite overburden (COB), Sukinda by Acidithiobacillus ferrooxidans has been investigated in this work. In anoxic environment, A. ferrooxidans reduced the ferric iron in goethite [Fe(O)OH] mineral of COB by using elemental sulphur as electron donor. Nickel embedded in the complex goethite matrix of COB was successfully recovered by cumulative action of sulphuric acid, generated by oxidation of elemental sulphur and reduction of ferric iron in goethite matrix by A. ferrooxidans. Forty one percent of the nickel present in COB was extracted in a 3 L scale bioreactor (pH of 1.8 ± 0.05, temperature of 28 ± 2°C) maintained in anoxic environment. In contrast, only 11% of the nickel present in COB was extracted with continuous supply of air to the bioreactor keeping all the parameters unchanged. Kinetics study of anoxic microbial processing of COB revealed that the chemical reaction rate control model fits to the rate of nickel dissolution (R(2)=0.975).

Abstrac t Th is study aims at studying effect of anaerobic dissimilatory iron (III) reducing bacterial consortium on different phases of iron present in lateritic n ickel ore. Such conversion in lateritic nickel ore are helpful in better recovery of sorbed metal values like Ni and Co by subsequent bioleaching or acid leaching. Here properties of thermally and microbially reduced lateritic nickel ore are co mpared vis-a-v is orig inal ore. An anaerobic d issimilatory iron (III) reducing bacterial consortium capable of using glucose as carbon source and laterit ic n ickel ore as terminal electron acceptor was used for microbial reduction of ore under anaerobic condition. M icrobial reduction changes the initial light bro wn colour of the lateritic n ickel ore to dark bro wn. The change in colour is due to the conversion of goethite to magnetite, wh ich is confirmed fro m the XRD pattern. The FTIR spectra and the UV-Visib le spectra support the presence both goethite and hematite. The study shows that changes in phases brought about by microb ial treat ment are d ifferent than those by thermal treat ment. The carrier mediated exchange interaction between Fe 2+ and Fe 3+ ions in lateritic n ickel o re samp le treated with IRB consortium is responsible for higher ferro magnetic ordering. The thermal reduction of the same sample showed lowering of ferro magnetic ordering due to the decreasing percentage of Fe 2+ and Fe 3+ ions.

Oxalic acid is a prominent metabolite secreted by several fungi under specific conditions, which acts as a metal chelating agent. Amongst different fungal species, Aspergillus niger is favored as the best option for microbial production of oxalic acid. The present study deals with the oxalic acid over production by A. niger in response to manganese supplement to its growth medium, which in turn improves the recovery of nickel from pre-treated chromite overburden(COB) during fungal bioleaching. The metabolic pathway in oxalate bio-synthesis by A. niger involves one prominent cytoplasmic enzyme oxaloacetate acetylhydrolase (OAH), which catalyzes the breakdown of oxaloacetate metabolic intermediate to oxalate and acetate. Oxalic acid production was increased due to supplement of manganese to the culture medium of the A. niger. Manganese acts as cofactor for OAH enzyme; further, it enhances the catalytic activity of OAH to produce more oxalate. With oxalic acid production by A. niger, nickel recovery from pre-treated COB was improved. During the study, a maximum of nickel recovery was achieved up to 38.6% from pre-treated COB by adding 80 ppm of manganese to the culture media, whereas 24.0% of nickel was recovered without supplement of manganese (experiments were performed at 30 °C and the COB pulp density 2% w/v).

In recent years microalgae have been proved as the potential source for biodiesel production due to high oil content. In the present study three brackish water microalgal strains (Chlorococcum sp., Chlorella sp. and Scenedesmus sp.) of Odisha coast were screened for the suitability for biodiesel production. Among all, Scenedesmus sp. seems to be the best one for high lipid productivity (24.66mg/L/day) with high biomass yield of 0.9g/L at stationary phase. Also the Scenedesmus sp. possesses the most adequate fatty acid profile. The present study suggested that Scenedesmus sp. is appropriate for biodiesel production for its high lipid content; this strain was selected for higher scale studies.

Heap bioleaching of low grade chalcopyrite (CuFeS 2 ) was carried out in 1000 tons scale over a time period of 383 days. Bacterial solution was prepared and re‐circulated in specially designed BACFOX (BACterial Film OXidation) tank. The micro‐organisms used in the pilot scale were a mixed culture of acidophilic bacteria predominantly of the Acidithiobacillus ferrooxidans strain. Effect of rest period, solution recirculation, acid concentration, frequency of solution transfers and seasonal effects on copper recovery were monitored. The leaching studies showed a cumulative copper dissolution rate of 0.14% per day (2.37 kg d − 1 ). The overall recovery of the heap was 30%. Variation in leaching efficiency and some of the precautionary measures to improve performance of heap bioleaching are also discussed.

Low grade copper ore (ball mill spillage) obtained from Malanjkhand Copper Mine was processed through heap bioleaching at pilot scale. Bioleach liquor (Pregnant Leach Solution) from the heap contains (g/L of) Cu (II) 0.45, Fe (III) 0.838, Zn (II) 0.006, Ni (II) 0.0014, Mn (II) 0.011 and Pb (IV) 0.004. Solvent extraction of copper from Pregnant Leach Solution was carried out using LIX 984N-C. Effect of different operational factors such as equilibrium pH (pHe), extractant concentration, strip solution concentration, phase ratio was examined to optimize the condition for selective and quantitative extraction of copper. Based on the results of extraction as well as stripping isotherm, a 6-cycle counter current simulation study (CCS) was conducted for the conformational study. The extraction of copper was quantitative in 2-stages using 1.5% (v/v) LIX 984N-C at A: O ratio of 1:2 and pHe 1.85. The CCS condition (two stages, phase ratio A:O = 1:4) obtained from the stripping isotherm study, further attributes to the enrichment (4 folds) of copper concentration in the strip solution.