Zulfa Al Disi
Other affiliations: Florida State University College of Arts and Sciences
Bio: Zulfa Al Disi is an academic researcher from Qatar University. The author has contributed to research in topics: Dolomite & Carbonate minerals. The author has an hindex of 6, co-authored 14 publications receiving 112 citations. Previous affiliations of Zulfa Al Disi include Florida State University College of Arts and Sciences.
TL;DR: In this article, the Dohat Faishakh Sabkha in Qatar was investigated for evidence of the role for aerobic bacteria in mediating the formation of high magnesium carbonates and dolomite, two minerals that commonly occur in the sabkha sediments.
Abstract: Dolomite (MgCa(CO3)2) is an important petroleum reservoir rock mineral common in ancient sedimentary rocks which is infrequently found in modern environments. The mechanism of dolomite formation remains poorly understood, although recent research has focused on the contribution of microbial processes. Sabkha is the Arabic term for saline mudflats occurring in regions characterized by extreme environmental conditions (high temperature, salinity, light intensity, and aridity), where diverse halophilic and extremophilic microorganisms are found. The dynamic evaporitic systems characteristic of sabkhas are crucial for the precipitation of minerals and a role for microorganisms in sabkhas in the process of mineralization has been proposed. In this study the Dohat Faishakh Sabkha in Qatar was investigated for evidence of the role for aerobic bacteria in mediating the formation of high magnesium carbonates and dolomite, two minerals that commonly occur in the sabkha sediments. 29 strains of aerobic microbes were obtained through inoculation on agar plates from two different cores sampled from the sabkha and identified by 16S rRNA gene sequencing as belonging to the genera Bacillus, Salinivibrio, Staphylococcus and, primarily, Virgibacillus. All strains examined caused the pH of an artificial growth medium to increase from 7 to 8.5; however, not all were capable of mediating mineral formation. Only Salinivibrio and Virgibacillus spp. isolates mediated the formation of detectable solid phases within the agar plates. Light microscopy, scanning electron microscopy energy dispersive X-ray (SEM/EDX), and X-ray diffraction (XRD) analyses indicate that the solid phase produced in the presence of these bacterial strains is MgCa(CO3)2 with a MgCO3 mol% varying from 0% to 40%. The results of these laboratory experiments suggested that, in the Dohat Faishakh Sabkha, aerobic bacteria may contribute in the formation of very high Mg calcite, a mineral that is considered the precursor of ordered dolomite.
TL;DR: A difference in crystallinity and morphology of dolomitic phases was observed: dumbbell-shaped proto-dolomite in the mats dominated by cyanobacteria and rhombohedral ordered-dolia in the mat dominated by FAPB.
Abstract: This publication was made possible by NPRP Grant 7-443-1-083 from the Qatar National Research Fund (a member of Qatar Foundation). MD was supported by the National Sciences and Engineering Research Council of Canada (NSERC Discovery Grant) and the Canada Foundation for Innovation and Ontario Research Fund (Leaders Opportunity Fund, Grant Number 22404). The statements made herein are solely the responsibility of the authors. The authors would like to acknowledge Oleksandra Kaskun for performing alkalinity measurements, Dr. K. Tait at the Royal Ontario Museum for use of XRD and Sal Boccia at the Ontario Centre for the Characterizations of Advanced Materials (OCCAM) for the assistance with SEM imaging.
TL;DR: In this paper , the self-healing process in concrete through microbial-induced calcium carbonate precipitation (MICP) performed by an adapted indigenous strain of Bacillus cereus isolated from soils in Qatar was investigated.
TL;DR: In this article, the authors present the results of laboratory experiments in which they cultured different strains of microbes, characterized their extracellular polymeric substances (EPS) excreted by microbes include organic molecules that catalyze the incorporation of Mg in the carbonate mineral.
TL;DR: In this paper, the authors made use of UREP grant # (UREP 14-062-1-008 ) from the Qatar National Research Fund (a member of Qatar foundation).
01 Jun 2005
TL;DR: Criteria for choosing the optimum isotherm model is established through a critical review of different adsorption models and the use of various mathematically error functions such as linear regression analysis, nonlinear regressionAnalysis, and error functions for adsorption data optimization.
TL;DR: A review of the direct and indirect mechanisms by which microbes facilitate the nucleation and shallow burial diagenetic stabilization of dolomite in marine sediments is presented in this paper.
TL;DR: The real wastewater experiment and the desorption studies showed that the green and black olive stones were a cost-effective and promising adsorbents for MB remediation from wastewater on account of their high adsorption and desor adaptation removal capacities.
Abstract: In the current study, the mechanistic understanding of the adsorption isotherm and thermodynamic aspects of cationic methylene blue (MB) dye adsorption onto cellulosic olive stones biomass from wastewater were investigated. The batch adsorption of MB onto the olive stones (black and green olive stones) was tested at a variety of pH, dye concentrations, temperatures, and biomass particle sizes. The adsorption thermodynamics such as Gibbs free energy, enthalpy, and entropy changes were also calculated. Moreover, the desorption studies of MB from the spent olive stones were studied to explore the re-usability of the biomasses. The results revealed that under the optimum pH of 10, the maximum MB uptake was achieved i.e. 80.2% for the green olive stones and 70.9% for the black olive stones. The green olive stones were found to be more efficient in remediating higher MB concentrations from water than the black olive stones. The highest MB removal of the green olive stones was achieved at 600 ppm of MB, while the highest MB removal of the black olive stones was observed at 50 ppm of MB. Furthermore, for almost all the concentrations studied (50-1000 ppm), the MB adsorption was the highest at the temperature of 45 °C (P value < 0.05). It was shown by the Fourier transform infrared that the electrostatic interaction and hydrogen bonding were proposed as dominant adsorption mechanisms at basic and acidic pH, respectively. While the hydrophobic-hydrophobic interaction was a dominant mechanism at neutral pH. The thermodynamic studies revealed that the adsorption process was endothermic, spontaneous, and favorable. Moreover, the real wastewater experiment and the desorption studies showed that the green and black olive stones were a cost-effective and promising adsorbents for MB remediation from wastewater on account of their high adsorption and desorption removal capacities.
TL;DR: Generally, there are a few issues such as low selectivity and adsorption capacity, process efficiency, complexity in preparation or synthesis, and problems associated to recovery and reuse that require considerable improvements in research and process development.