Specific mechanism of Acidithiobacillus caldus extracellular polymeric substances in the bioleaching of copper-bearing sulfide ore.
ABSTRACT: This study aimed to reveal the specific mechanism of extracellular polymeric substances (EPS) in the bioleaching of copper-bearing sulfide ore by moderately thermophilic bacterium Acidithiobacillus caldus. The bioleaching performance of blank control (BC), planktonic cell deficient (PD), attached cell deficient (AD), and EPS deficient (ED) systems were compared, to investigate the specific functions of "non-contact" and "contact" (including direct contact and, EPS-mediated contact) mechanisms. The detailed mechanics of bioleaching were studied using ?x of cell growth, scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The ?x of cell growth demonstrated that EPS favors planktonic and attached cell growth. SEM observation revealed that intensive micro-pores on slag benefitted from the "EPS-mediated contact" mechanism. XRD identification indicated that additional chemical derivatives were produced via "EPS-mediated contact" mechanism, because of the active iron/sulfur metabolism. FTIR analysis revealed that the absorption peaks of C-O-S, sulfate, and S = O, which are closely associated with sulfur metabolism, have significant influences of EPS secretion. Taken together, the "EPS-mediated contact" mechanism contributed to almost half of the "contact" mechanism efficiency and a quarter of the total bioleaching efficiency. The proposed specific mechanism of EPS can deepen our understanding of similar bioleaching processes.
Project description:Extracellular polymeric substances (EPS) play important roles in regulating the dewaterability of sludge. This study sought to elucidate the influence of EPS on the dewaterability of sludge during bioleaching process. Results showed that, in bioleaching system with the co-inoculation of Acidithiobacillus thiooxidans TS6 and Acidithiobacillus ferrooxidans LX5 (A. t+A. f system), the capillary suction time (CST) of sludge reduced from 255.9 s to 25.45 s within 48 h, which was obviously better than the controls. The correlation analysis between sludge CST and sludge EPS revealed that the sludge EPS significantly impacted the dewaterability of sludge. Sludge CST had correlation with protein content in slime and both protein and polysaccharide contents in TB-EPS and Slime+LB+TB layers, and the decrease of protein content in slime and decreases of both protein and polysaccharide contents in TB-EPS and Slime+LB+TB layers improved sludge dewaterability during sludge bioleaching process. Moreover, the low sludge pH (2.92) and the increasing distribution of Fe in the solid phase were another two factors responsible for the improvement of sludge dewaterability during bioleaching. This study suggested that during sludge bioleaching the growth of Acidithiobacillus species resulted in the decrease of sludge pH, the increasing distribution of Fe in the solid phase, and the decrease of EPS content (mainly including protein and/or polysaccharide) in the slime, TB-EPS, and Slime+LB+TB layers, all of which are helpful for sludge dewaterability enhancement.
Project description:A method to prepare novel organic-inorganic hydrophobic nanocomposite films was proposed by a site-specific polymerization process. The inorganic part, the core of the nanocomposite, is a ternary SiO₂-Al₂O₃-TiO₂ nanoparticles, which is grafted with methacryloxy propyl trimethoxyl silane (KH570), and wrapped by fluoride and siloxane polymers. The synthesized samples are characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectrscopy, X-ray diffractometry (XRD), contact angle meter (CA), and scanning electron microscope (SEM). The results indicate that the novel organic-inorganic hydrophobic nanocomposite with a core-shell structure was synthesized successfully. XRD analysis reveals the nanocomposite film has an amorphous structure, and FTIR analysis indicates the nanoparticles react with a silane coupling agent (methacryloxy propyl trimethoxyl silane KH570). Interestingly, the morphology of the nanoparticle film is influenced by the composition of the core. Further, comparing with the film synthesized by silica nanoparticles, the film formed from SiO₂-Al₂O₃-TiO₂ nanoparticles has higher hydrophobic performance, i.e., the contact angle is greater than 101.7°. In addition, the TEM analysis reveals that the crystal structure of the particles can be changed at high temperatures.
Project description:We propose a simple and low-cost process for the preparation of porous Ti foams through a sponge replication method using single-step air sintering at various temperatures. In this study, the apatite-forming ability of air-sintered Ti samples after 21 days of immersion in simulated body fluid (SBF) was investigated. The microstructures of the prepared Ca-P deposits were examined by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FTIR) spectroscopy, and cross-sectional transmission electron microscopy (TEM). In contrast to the control sample sintered in vacuum, which was found to have the simple hexagonal α-Ti phase, the air-sintered samples contained only the rutile phase. High intensities of XRD peaks for rutile TiO₂ were obtained with samples sintered at 1000 °C. Moreover, the air-sintered Ti samples had a greater apatite-forming ability than that of the Ti sample sintered in vacuum. Ti samples sintered at 900 and 1000 °C had large aggregated spheroidal particles on their surfaces after immersion in SBF for 21 days. Combined XRD, energy-dispersive X-ray spectroscopy, FTIR spectroscopy, and TEM results suggest that the calcium phosphate deposited on the rutile TiO₂ surfaces consist of carbonated calcium-deficient hydroxyapatite instead of octacalcium phosphate.
Project description:A novel natural hydroxyapatite (HAp) bioceramic was extracted from the ostrich cortical bone by the thermal decomposition method. HAp was characterized by different analytical tools such as thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM). Removal of organic impurities from the bone powder was confirmed by TGA analysis. FTIR spectra of HAp confirmed the presence of the major functional groups such as phosphate (PO4 3-), hydroxyl (OH-), and carbonate (CO3 2-) in the bioceramic. The XRD data revealed that the HAp was the crystalline phase obtained by calcination of the bone powder at 950°C, and the SEM analyses confirmed the typical plate-like texture of the nanosized HAp crystals.
Project description:In this paper, we for the first time show the ability of the mesophilic fungus Fusarium oxysporum in the bioleaching of waste material such as Fly-ash for the extracellular production of highly crystalline and highly stable, protein capped, fluorescent and water soluble silica nanoparticles at ambient conditions. When the fungus Fusarium oxysporum is exposed to Fly-ash, it is capable of selectively leaching out silica nanoparticles of quasi-spherical morphology within 24 h of reaction. These silica nanoparticles have been completely characterized by UV-vis spectroscopy, Photoluminescence (PL), Transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Energy dispersive analysis of X-rays (EDAX).
Project description:High-degree functionalization of graphene oxide (GO) nanoparticles (NPs) using polydopamine (PDA) was conducted to produce polydopamine functionalized graphene oxide nanoparticles (GO-PDA NPs). Aiming to explore their potential use as nanofiller in membrane separation processes, the spectral and structural properties of GO-PDA NPs were comprehensively analyzed. GO NPs were first prepared by the oxidation of graphite via a modified Hummers method. The obtained GO NPs were then functionalized with PDA using a GO:PDA ratio of 1:2 to obtain highly aminated GO NPs. The structural change was evaluated using XRD, FTIR-UATR, Raman spectroscopy, SEM and TEM. Several bands have emerged in the FTIR spectra of GO-PDA attributed to the amine groups of PDA confirming the high functionalization degree of GO NPs. Raman spectra and XRD patterns showed different crystalline structures and defects and higher interlayer spacing of GO-PDA. The change in elemental compositions was confirmed by XPS and CHNSO elemental analysis and showed an emerging N 1s core-level in the GO-PDA survey spectra corresponding to the amine groups of PDA. GO-PDA NPs showed better dispersibility in polar and nonpolar solvents expanding their potential utilization for different purposes. Furthermore, GO and GO-PDA-coated membranes were prepared via pressure-assisted self-assembly technique (PAS) using low concentrations of NPs (1 wt. %). Contact angle measurements showed excellent hydrophilic properties of GO-PDA with an average contact angle of (27.8°).
Project description:In this paper, a wood-SiO2 composite material was prepared via in-situ polymerization using vacuum/pressure impregnation technology using commercial scale nano silica sol and Chinese Fir (Cunninghamia lanceolate (Lamb.) Hook.). Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TG), and water contact angle were used to study the changes in the microstructure and physical and mechanical properties of this composite. The results showed that silica sol can penetrate and distribute into the wood cell cavities and surface of cell walls and hence combine with the substances of wood materials. FTIR results indicated that the -OH groups of wood can polycondense in-situ with silica sol to form Si-O-C covalent bonds, and amorphous SiO2 formed from Si-O-Si bonds between the -OH groups of silica sol did not change the crystalline structure of wood cell walls. This in-situ formulating composite significantly improved the compact microstructure, thermal and mechanical properties, and hydrophobicity of the composites.
Project description:As a nano-adsorbent, magnetic graphene oxide (GO/Fe3O4) was synthesized to potentially adsorb propranolol (PRO) from water. The synthetic material was characterized by SEM, TEM, VSM, FTIR, XRD, zeta potential, and XPS. The environmental factors, such as pH, humic acid concentration, PRO concentration, and contact time, were investigated regarding their effect on the adsorption process. The kinetics data fitted the pseudo first-order and second-order kinetics equations. The Langmuir equation, the Freundlich equation, and the Sips equation were used to analyze the adsorption isotherms. Electrostatic attraction, hydrogen bonding, and the ?-? interaction all contributed to the adsorption process of PRO onto GO/Fe3O4. The discovery of this study emphasized the feasibility of GO/Fe3O4 removal of PRO and expanded the scope of the application of GO.
Project description:An exopolysaccharide (EPS) producing strain CC30 was isolated from raw milk and identified as Streptococcus thermophilus with morphological and 16S sequencing analysis. The strain was shown to produce 1.95?g/L of EPS when grown in skim milk lactose medium at 30°C by increasing the viscosity of the medium. The EPS was isolated and purified, and it was shown to consist of glucose and galactose in 1?:?1 ratio, with molecular weights ranging from 58 to 180?kDa. FTIR spectroscopy indicated the EPS to have amide, hydroxyl, and carboxyl groups. Under Atomic Force Microscopy, EPS showed spike-like lumps of EPS. Scanning Electron Microscopy (SEM) studies showed that it had irregular lumps with a coarse surface. The EPS displayed pseudoplastic nature. Thermogravimetric analysis (TGA) reported a degradation temperature of 110.84°C. The purified EPS exhibited reducing activity, hydrogen peroxide radical scavenging activity, and emulsification activity. The results of the present study indicated that EPS producing Streptococcus thermophilus could serve as a promising candidate for further exploitation in food industry.
Project description:Herbal drug delivery is limited by poor solubility and bioavailability which can be overcome with suitable nanomaterials that will enhance their pharmacokinetics and performance.This study aimed to analyze the synthesis, characterization, and biological activities of silver nanoparticles (AgNPs) from three spices.AgNPs were prepared using 0.1 M silver nitrate and aqueous extracts of Allium sativum L. (garlic), Zingiber officinale Rosc. (ginger), and Capsicum frutescens L. (cayenne pepper). The AgNPs were characterized using ultraviolet-visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray, X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy.The AgNPs were formed within an hour of the reaction and showed maximum UV-Vis absorption in the 375-480 nm range. SEM and TEM revealed well-dispersed spherical particles with little agglomeration, average sizes of 3-6 nm, 3-22 nm, and 3-18 nm for garlic, ginger, and cayenne pepper, respectively. FTIR showed that amine, protein, phenolic, aromatic, and alkynes groups contributed to AgNP synthesis and XRD confirmed their crystalline and face-centered cubic nature. Antibacterial action of the AgNPs was in the following order: ginger (minimum inhibitory concentration [MIC] <25 μg/mL) > garlic> cayenne pepper (MIC 125 μg/mL). Antioxidant action showed cayenne pepper > ginger > garlic (inhibitory concentration 50% [IC50]: 40, 240, and 250 μg/mL, respectively) against 2,2-Azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) and garlic > cayenne pepper > ginger (IC50: <31.25, 40, and 120 μg/mL, respectively) against 1,1-diphenyl-2-picrylhydrazyl.Optimization of this green synthesis would support the production of AgNPs with great therapeutic potentials.The synthesis, characterization, and biological activities of silver nanoparticles (AgNPs) from garlic, ginger and cayenne pepper were evaluatedThe AgNPs formed were characterized using UV-Vis spectroscopy, SEM and TEM microscopy, as well as EDX, XRD and FTIR spectroscopy AgNPs were well dispersed with spherical shapes and average sizes of 3-6nm, 3-22nm and 3-18 nm for garlic, ginger and cayenne pepper respectivelyAmine, protein, phenolic and alkyne groups were revealed as the capping agents for the nanoparticlesThe silver nanoparticles were confirmed to be crystalline with characteristic face centred cubic natureThe antibacterial and antioxidant activities of the AgNPs confirmed the therapeutic potential of the AgNPs. Abbreviations used: AgNPs: Silver nanoparticles; UV-Vis: ultraviolet-visible; SEM: Scanning electron microscopy; TEM: Transmission electron microscopy; EDX: Energy dispersive X-ray; XRD: X-ray diffraction; FTIR: Fourier transform infrared; GaNPs: Garlic nanoparticles; GiNPs: Ginger nanoparticles; C.PeNPs: Cayenne pepper nanoparticles; FCC: Face centred cubic; SPR: Surface Plasmon resonance; ABTS-2: 2-Azino-bis (3-ethylbenzthiazoline-6-sulfonic acid); DPPH-1: 1-diphenyl-2-picrylhydrazyl.