Bioflocculation of (Iron oxide – Silica) system using Bacillus cereus bacteria isolated from Egyptian iron ore surface

In mineral bio-beneficiation, it is very important to understand the microbial surface characteristics and its behaviour onto the mineral surface. Bacillus cereus bacterium has never been used before as a bio-reagent for separation of different mineral systems. In this work, complete characterization of such type of bacteria, isolated from Egyptian iron ore surface, including gram stain, growth curve, Biolog microbial identification, Zeta potential characterization, Fourier Transform Infrared Spectrometer, FTIR characterization as well as protein and polysaccharide analysis have been studied. The results confirmed that Bacillus cereus is a gram positive bacterium, rod shaped, smooth and circular with different types of by-products as polysaccharides, carboxylic acids and amino acids that gives an amphoteric behaviour on the cell surface. The results of zeta potential showed that the iso-electric points (IEP) of iron oxide (≈6.3) and silica (≈1.8) were significantly displaced to low values (≈2.2) and (≈1) respectively after treatment with the bacterial isolates. The results obtained showed a better affinity of Bacillus cereus to hematite mineral surface rather than silica surface and could be used in separation of such mineral from its associated gangue minerals. On applying B. cereus bacterial strain as a sole flocculating agent, to selectively separate hematite from its mixture with silica, succeeded in the removal of 80% of SiO2 as a concentrate containing about 2% SiO2 and 98% Fe2O3 with 82% flocculated by Wt. and a good recovery of 89.20%. Keywords: Bacillus cereus, Hematite, Silica, Surface modification, Adsorptio

Utilization of surface modified phyllosilicate mineral for heavy metals removal from aqueous solutions

The objective of this work is to enhance the adsorbing performance of the natural Egyptian phyllosilicate mineral, glauconite (greensand), through surface modification to obtain a particular combination of physical and chemical properties. It was found that Zn removal increased from 84% to 94%, while Pb removal varied from 96.67% to 99% by using 10–25 g/l modified glauconite in a solution having 50 mg/l Zn2+ and 30 mg/l pb2+ ions. Adsorption data were investigated using Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherms. Linear regression methods are used to determine adsorption capacities and optimum adsorption isotherms. R2 value of Langmuir isotherm model for pb2+ is higher than other models. The maximum monolayer coverage (Qo) from Langmuir isotherm model was calculated to be 15.363 and 21.654 mg/g and the separation factor indicating a favorable sorption experiment is 0.0324 and 0.13207 for Zn2+ and Pb2+ respectively. Also from Freundlich isotherm model, the intensities of adsorption (n) that indicated favorable sorption are 1.3036 and 1.364 for Zn2+ and Pb2+ respectively. The heat of sorption process was calculated from Temkin isotherm model to be 6.44101 and 4.1353 J/mol for Zn2+ and Pb2+ respectively, that indicated to the physisorption process which B < 20 kJ/mol so, Temkin isotherm is not fitted with experimental adsorption but the mean free energy was calculated from DRK isotherm which are 24.693 and 47.093 kJ/mol, where ED < 8 proved that the adsorption experiment followed a chemisorption process. So the relative adsorption capacity for metals was in the order Pb < Zn. Keywords: Adsorption, Heavy metals, Surface modification, Glauconite, Equilibrium isotherm

Surface modified bentonite mineral as a sorbent for Pb2+Pb^{2+} and Zn2+Zn^{2+} ions removal from aqueous solutions

Environmental pollution by lead ($Pb^{2+}$) and zinc ($Zn^{2+}$) ions has become an important issue due to its harmful effects on human health and environment. This work aims to evaluate the application of surface modified Egyptian bentonite mineral by acid activation using $H_2SO_4$ and thermal treatment as an adsorbent to remove lead ($Pb^{2+}$) and zinc ($Zn^{2+}$) ions from aqueous solution. X-ray diffraction (XRD), Fourier Transformed Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM) techniques were used to investigate the modified bentonite. The impact of organic and inorganic dispersants on rheological characteristics of bentonite suspensions was investigated. Adsorption of $Pb^{2+}$ and $Zn^{2+}$ ions using modified bentonite mineral was performed with different adsorbent doses and pH values. Removal efficiencies of lead and zinc are 99.67% and 99%, respectively with adsorbent dose of 25 g/l at pH of 6.2