aqueous solutions

Hamdallah Bearat's picture

A Novel Approach to Mineral Carbonation: Enhancing Carbonation While Avoiding Mineral Pretreatment Process Cost

Journal Title, Volume, Page: 
Arizona State University, Department of Chemistry and Biochemistry, Center for Solid State Science, Science and Engineering of Materials Graduate Program, and Department of Mechanical and Aerospace Engineering Tempe, AZ 85287-1604
Year of Publication: 
2007
Authors: 
Andrew V. G. Chizmeshya
Michael J. McKelvy
Kyle Squires
Ray W. Carpenter
Hamdallah Bearat
Current Affiliation: 
Department of Materials Science, Faculty of Engineering and Information Technology, An-Najah National University, Nablus. Palestine
Preferred Abstract (Original): 

Known fossil fuel reserves, especially coal, can support global energy demands for centuries to come, if the environmental problems associated with CO{sub 2} emissions can be overcome. Unlike other CO{sub 2} sequestration candidate technologies that propose long-term storage, mineral sequestration provides permanent disposal by forming geologically stable mineral carbonates. Carbonation of the widely occurring mineral olivine (e.g., forsterite, Mg{sub 2}SiO{sub 4}) is a large-scale sequestration process candidate for regional implementation, which converts CO{sub 2} into the environmentally benign mineral magnesite (MgCO{sub 3}). The primary goal is cost-competitive process development. As the process is exothermic, it inherently offers low-cost potential. Enhancing carbonation reactivity is key to economic viability. Recent studies at the U.S. DOE Albany Research Center have established that aqueous-solution carbonation using supercritical CO{sub 2} is a promising process; even without olivine activation, 30-50% carbonation has been achieved in an hour. Mechanical activation (e.g., attrition) has accelerated the carbonation process to an industrial timescale (i.e., near completion in less than an hour), at reduced pressure and temperature. However, the activation cost is too high to be economical and lower cost pretreatment options are needed. We have discovered that robust silica-rich passivating layers form on the olivine surface during carbonation. As carbonation proceeds, these passivating layers thicken, fracture and eventually exfoliate, exposing fresh olivine surfaces during rapidly-stirred/circulating carbonation. We are exploring the mechanisms that govern carbonation reactivity and the impact that (1) modeling/controlling the slurry fluid-flow conditions, (2) varying the aqueous ion species/size and concentration (e.g., Li+, Na+, K+, Rb+, Cl-, HCO{sub 3}{sup -}), and (3) incorporating select sonication offer to enhance exfoliation and carbonation. Thus far, we have succeeded in nearly doubling the extent of carbonation observed compared with the optimum procedure previously developed by the Albany Research Center. Aqueous carbonation reactivity was found to be a strong function of the ionic species present and their aqueous activities, as well as the slurry fluid flow conditions incorporated. High concentration sodium, potassium, and sodium/potassium bicarbonate aqueous solutions have been found to be the most effective solutions for enhancing aqueous olivine carbonation to date. Slurry-flow modeling using Fluent indicates that the slurry-flow dynamics are a strong function of particle size and mass, suggesting that controlling these parameters may offer substantial potential to enhance carbonation. During the first project year we developed a new sonication exfoliation apparatus with a novel sealing system to carry out the sonication studies. We also initiated investigations to explore the potential that sonication may offer to enhance carbonation reactivity. During the second project year, we extended our investigations of the effects of sonication on the extent of carbonation as a function of the following parameters: particle size distribution, the mass of solid reactant, volume fraction of aqueous solution present, sonication power, time, temperature, and CO{sub 2} pressure. To date, none of the conditions investigated have significantly enhanced carbonation. Mechanistic investigations of the stirred ({approx}1,500 rpm) aqueous olivine carbonation process indicate the carbonation process involves both incongruent magnesium dissolution and silica precipitation, which results in robust silica-rich passivating layer formation. Secondary ion mass spectrometry observation of H within the passivating layer that forms during static carbonation suggests 2H{sup +}/Mg{sup 2+} ion exchange is associated with incongruent dissolution. Apparently, H{sub 2}O forms at or near the olivine/passivating-layer interface during the process and diffuses out through the passivating layers during the carbonation reaction. This is also consistent with the observation that magnesite nanocrystals form within the passivating layers, further indicating the layers offer significant permeability to the key solution reaction species present during carbonation (e.g., Mg2+, H+, H{sub 2}O, CO{sub 2}, and HCO{sub 3}{sup -}). Cracking of the passivating layer surface during carbonation is routinely observed and can be related to the tensile stress associated with the dramatic volume decrease as olivine forms silica at the reaction surface. In our YEAR 2 studies we also demonstrated that the addition of quartz particles as an abrasive slurry component significantly enhanced carbonation, further substantiating the importance of particle-particle abrasion in enhancing passivating layer exfoliation and carbonation.

2052's picture

Efficiency of Removal of Cadmium from Aqueous Solutions by Plant Leaves and the Effects of Interaction of Combinations of Leaves on Their Removal Efficiency

Journal Title, Volume, Page: 
Journal of Environmental Management Volume 87, Issue 3, May 2008, Pages 521–532
Year of Publication: 
2008
Authors: 
R. Salim
Department of Chemistry, Faculty of Science, An-Najah National University, Nablus, Palestine
M. Al-Subu
Department of Chemistry, Faculty of Science, An-Najah National University, Nablus, Palestine
Current Affiliation: 
Department of Chemistry, Faculty of Science, An-Najah National University, Nablus, Palestine
E. Dawod
Department of Chemistry, Faculty of Science, An-Najah National University, Nablus, Palestine
Preferred Abstract (Original): 

Removal of cadmium from aqueous solutions using 20 species of plant leaves and combinations of these leaves have been studied. Several factors affecting the removal efficiency have been studied. The most efficient types of plant leaves for the removal of cadmium are those of styrax, plum, pomegranate and walnut. The interaction effect of the combined leaf samples on the efficiency of removal of cadmium has been found to be additive in combinations involving styrax plant leaves but seems to be antagonistic in all other combinations. The optimum experimental conditions for removal of cadmium have been found to be at pH 4.1, using high concentrations of naturally dried plant leaves, using ground leaves and to remove cadmium from agitated aqueous solutions. The percentage of metal removed at an initial cadmium concentration of 10 mg/l by the most efficient types of leaves have been found to be 85% for styrax leaves, 85% for plum leaves, 80% for pomegranate leaves, 78% for walnut leaves and 77% for meddler leaves. The presence of foreign ions or complexing agents has been found to reduce the efficiency of removal of cadmium by plant leaves. About 80–85% of the cadmium in charged plant leaves has been released under the influence of changing the pH of the solution, addition of competing ions and the addition of EDTA. The results of removal of cadmium by plant leaves have been found to follow the Freundlich adsorption isotherm, first-order reaction with respect to cadmium and to have intra-pore diffusion as the rate-limiting step.

2052's picture

Removal of Zinc from Aqueous Solutions by Dry Plant Leaves

Journal Title, Volume, Page: 
Process Safety and Environmental Protection Volume 81, Issue 4, July 2003, Pages 236–242
Year of Publication: 
2003
Authors: 
R. Salim
Department of Chemistry, Faculty of Science, An-Najah National University, Nablus, Palestine
M. Al-Subu
Department of Chemistry, Faculty of Science, An-Najah National University, Nablus, Palestine
Current Affiliation: 
Department of Chemistry, Faculty of Science, An-Najah National University, Nablus, Palestine
I. Abu-Shqair
Department of Chemistry, Faculty of Science, An-Najah National University, Nablus, Palestine
H. Braik
Department of Chemistry, Faculty of Science, An-Najah National University, Nablus, Palestine
Preferred Abstract (Original): 

Removal of zinc from aqueous solutions by 15 species of plant leaves was studied. The maximum efficiency of removal was found to be by walnut and poplar leaves at pH 6 with a maximum removal of 82%. Increasing the concentration of plant leaves increased the removal of zinc up to a limit. Agitation of solution increased the efficiency of the removal process. The presence of competing and complexing agents affected the removal process negatively but also positively in few cases.

Ibrahim Diab Abu-Shqair's picture

Removal of Zinc From Aqueous Solutions by Dry Plant Leaves

Journal Title, Volume, Page: 
Process Safety and Environmental Protection, Volume 81, Issue 4, Pages 236-242
Year of Publication: 
2003
Authors: 
Ibrahim Diab Abu-Shqair
Chemistry Department, An-Najah University, Nablus, Palestine
Current Affiliation: 
Chemistry Department, An-Najah University, Nablus, Palestine
R. Salim
Chemistry Department, An-Najah University, Nablus, Palestine
Mohammed M. Al-Subu
Chemistry Department, An-Najah University, Nablus, Palestine
H. Braik
Chemistry Department, An-Najah University, Nablus, Palestine
Preferred Abstract (Original): 

Removal of zinc from aqueous solutions by 15 species of plant leaves was studied. The maximum efficiency of removal was found to be by walnut and poplar leaves at pH 6 with a maximum removal of 82%. Increasing the concentration of plant leaves increased the removal of zinc up to a limit. Agitation of solution increased the efficiency of the removal process. The presence of competing and complexing agents affected the removal process negatively but also positively in few cases.

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