Effect of Magnesium Ion on the Precipitation of Hollow Calcium Carbonate by Bubble Templating Method

2006 ◽  
Vol 317-318 ◽  
pp. 65-68 ◽  
Author(s):  
Gunawan Hadiko ◽  
Yong Sheng Han ◽  
Masayoshi Fuji ◽  
Minoru Takahashi
Keyword(s):  
Calcium Carbonate ◽  
Calcium Chloride ◽  
Flow Rate ◽  
Room Temperature ◽  
Crystal Phase ◽  
Magnesium Ion ◽  
Precipitation Condition ◽  
Templating Method ◽  
Hollow Particles

Hollow calcium carbonate (CaCO3) particles were synthesized by bubbling CO2 in the solution of calcium chloride (CaCl2) with the presence of ammonia at room temperature. In this method, CO2 bubble, besides as reactant, has an important role as a template for forming hollow particles. The precipitation was carried out by controlling the precipitation condition, such as pH, flow rate and additives. Hollow calcium carbonate particles were precipitated with the major crystal phase of vaterite. An interesting finding is that magnesium ion (Mg2+) can suppress the transformation of vaterite to calcite by inhibiting the growth of the calcite.

Study of Carbonizing Processes for Sintered Dolomite

2007 ◽  
Vol 336-338 ◽  
pp. 2552-2555 ◽  
Author(s):  
Jing Hua Xue ◽  
Min Fang Han ◽  
Qing Yun Wang
Keyword(s):  
Calcium Carbonate ◽  
Calcium Hydroxide ◽  
Magnesium Hydroxide ◽  
Room Temperature ◽  
Xrd Analysis ◽  
Magnesium Carbonate ◽  
Crystal Phase ◽  
Carbonization Process

It is the easy and widely used way to make light calcium carbonate and magnesium carbonate from dolomite by carbonizing process. During this process, the dolomite is calcined at different temperature, from 700°C to 950°C to get the mixture including either calcium carbonate and magnesia or calcia and magnesia. Then the mixture is blended with water in different temperature from room temperature to 80°C. As a result, it is supposed to get calcium hydroxide and magnesium hydroxide, but XRD analysis reveals that it is not accord with the theory. Magnesium hydroxide can not be obtained during this reaction. After the carbonization process, the calcium carbonate and a kind of mixture which is composed with different crystal phase of Mg5(CO3)4(OH)2[H2O]4 have been produced, instead of magnesium carbonate. The magnesia is gotten when the mixture is calcined at 450~750°C.

scholarly journals Pure hydroxyapatite synthesis originating from amorphous calcium carbonate

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Michika Sawada ◽  
Kandi Sridhar ◽  
Yasuharu Kanda ◽  
Shinya Yamanaka
Keyword(s):  
Calcium Carbonate ◽  
Calcium Phosphate ◽  
Room Temperature ◽  
Molar Ratio ◽  
Final Phase ◽  
Amorphous Calcium Carbonate ◽  
Phosphate Compound ◽  
Synthesis Strategy ◽  
Phosphorylation Reaction ◽  
Subsequent Calcination

AbstractWe report a synthesis strategy for pure hydroxyapatite (HAp) using an amorphous calcium carbonate (ACC) colloid as the starting source. Room-temperature phosphorylation and subsequent calcination produce pure HAp via intermediate amorphous calcium phosphate (ACP). The pre-calcined sample undergoes a competitive transformation from ACC to ACP and crystalline calcium carbonate. The water content, ACC concentration, Ca/P molar ratio, and pH during the phosphorylation reaction play crucial roles in the final phase of the crystalline phosphate compound. Pure HAp is formed after ACP is transformed from ACC at a low concentration (1 wt%) of ACC colloid (1.71 < Ca/P < 1.88), whereas Ca/P = 1.51 leads to pure β-tricalcium phosphate. The ACP phases are precursors for calcium phosphate compounds and may determine the final crystalline phase.

scholarly journals The role of bacterial urease activity on the uniformity of carbonate precipitation profiles of bio-treated coarse sand specimens

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Charalampos Konstantinou ◽  
Yuze Wang ◽  
Giovanna Biscontin ◽  
Kenichi Soga
Keyword(s):  
Calcium Carbonate ◽  
Calcium Chloride ◽  
Urease Activity ◽  
Coarse Sand ◽  
Carbonate Precipitation ◽  
Population Densities ◽  
Carbonate Cements ◽  
Microbially Induced Carbonate Precipitation

AbstractProtocols for microbially induced carbonate precipitation (MICP) have been extensively studied in the literature to optimise the process with regard to the amount of injected chemicals, the ratio of urea to calcium chloride, the method of injection and injection intervals, and the population of the bacteria, usually using fine- to medium-grained poorly graded sands. This study assesses the effect of varying urease activities, which have not been studied systematically, and population densities of the bacteria on the uniformity of cementation in very coarse sands (considered poor candidates for treatment). A procedure for producing bacteria with the desired urease activities was developed and qPCR tests were conducted to measure the counts of the RNA of the Ure-C genes. Sand biocementaton experiments followed, showing that slower rates of MICP reactions promote more effective and uniform cementation. Lowering urease activity, in particular, results in progressively more uniformly cemented samples and it is proven to be effective enough when its value is less than 10 mmol/L/h. The work presented highlights the importance of urease activity in controlling the quality and quantity of calcium carbonate cements.

Enhanced room-temperature phosphorescence of triphenylphosphine derivatives without metal and heavy atoms in their crystal phase

RSC Advances ◽  
2016 ◽  
Vol 6 (57) ◽  
pp. 51683-51686 ◽  
Author(s):  
Pengchong Xue ◽  
Panpan Wang ◽  
Peng Chen ◽  
Jipeng Ding ◽  
Ran Lu
Keyword(s):  
Room Temperature ◽  
Crystal Phase ◽  
Room Temperature Phosphorescence ◽  
Heavy Atoms

Two simple triphenylphosphine derivatives have weak phosphorescence in solution, but the emissions were enhanced by 6.5 and 27 times, respectively, in crystals.

scholarly journals Pellet Softening Process for the Removal of the Groundwater Hardness; Modelling and Experimentation

2019 ◽  
Vol 12 (3) ◽  
pp. 135-143 ◽  
Author(s):  
Fatin Abdul_kareem Ashoor ◽  
Amer D. Zmat ◽  
Muthanna H. AlDahhan
Keyword(s):  
Calcium Carbonate ◽  
Removal Efficiency ◽  
Flow Rate ◽  
Solution Flow Rate ◽  
Pellet Size ◽  
Solution Flow ◽  
Bed Height ◽  
Naoh Solution ◽  
Softening Process ◽  
Calcium And Magnesium Ions

A lab scale pellet reactor (PR) was designed and fabricated to carry out extensive investigations on the removal efficiency of the hardness of groundwater.  The groundwater of 2200 – 2600 mg/L hardness was collected from Abdulla Ibnalhassan wells area located at the west desert of Al-Shinafiyah district (70 km to the southwest of Al-Dewaniyah city, Iraq). Both hydrodynamic parameters of the pellet reactor (porosity and fluidized bed height) and the parameters of calcium carbonate crystallization process (calcium carbonate equilibrium, pellet size, and density) were modeled and compared with the experimental results of the lab scale pellet reactor. The comparison showed that fair agreement between modeled and measured results was observed. The removal efficiency of both calcium and magnesium ions were 62.5-99% and 83-99% respectively. The removal efficiency was found to be strongly dependent on pH and the ratio of NaOH solution flow rate to the groundwater flow rate in the pellet reactor.

Study on the Effect of Magesium Ion on the Crystal Phase of Calcium Carbonate

2012 ◽  
Vol 554-556 ◽  
pp. 35-38
Author(s):  
Zhen Fa Liu ◽  
Mei Fang Yan ◽  
Li Hui Zhang ◽  
Hai Hua Li
Keyword(s):  
Magnetic Field ◽  
Calcium Carbonate ◽  
Inhibitory Effect ◽  
Crystal Phase ◽  
Strong Inhibitory Effect ◽  
Blank Solution

Morphology and crystal phase of calcium carbonate, which formed with the presence of Mg2+, were characterized by SEM and XRD. The effect of Mg2+ on crystallization and crystal phase of calcium carbonate was studied. The results showed that the crystal phase of calcium carbonate were mainly calcite and aragonite and the content of aragonite was higher after adding Mg2+ to the blank solution. With the increase of Mg2+ concentration, the content of aragonite increased. The calcium carbonate crystals grain became more fine and the content of aragonite was higher by synergistic treatment between Mg2+ and magnetic field. There was a strong inhibitory effect on calcite when the concentration of Mg2+ was more than 0.50mmol.L-1. The calcite could be transformed into aragonite in the presence of Mg2+ in solution.

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