Study on Dispersion of Cement Grout in Sand considering Filtration Effect through the EDTA Titration Test

When grouting in a sand layer, the filtration of the layer on cement particles is an important aspect affecting the grout dispersion. However, few laboratory studies have been conducted to investigate the distribution of cement particles along the direction of dispersion. In this study, a group of laboratory tests were conducted by grouting in a sand layer under different levels of pressure. The distributions of cement particles in sand after curing were then measured using the EDTA titration test. The results show that, due to the filtration effect, the cement content along the radial direction of dispersion decreases nonlinearly in a reversed S shape. The filtration effect becomes more obvious when grouting with a higher grout concentration. With the decrease in grout concentration, the filtration effect becomes weak and cement particles could disperse farther in the sand layer, but the cement content in a farther location becomes lower and the improvement of the soil strength is limited. In the end, the measured results were compared with the calculated results according to an existing theoretical study and the trend reasonably matches with each other.

Cation Exchange Capacity of Zeolite X from Bagasse Ash against Magnesium(II)

<p class="BodyAbstract">Water is a substance crucial for human life and industries. The good water must be fulfill some criteria, such as absence of Ca²⁺ or Mg²⁺ cations. The cations can be reduced by ion exchange process. This study used synthesized zeolite X from bagasse ash as cation exchange for Mg²⁺. Mg ion was used as standard to determine hardness of water by EDTA titration. The analysis showed cation exchange capacity of zeolite X with molar ratio of Si/Al 1; 1,5 and 2 was 1,9. The value indicated zeolite X have high capability as cation absorbents for Mg²⁺ ion.</p><p class="BodyAbstract"> </p><strong><em>Keywords:</em></strong><em> bagasse ash, cation exchange capacity, magnesium(II), water hardness, zeolite X</em>

Factors on Leaching Zinc and Copper from Zinc Leach Residue

It is found that cuprous sulfite, zinc sulfate and zinc sulfide were the main phases of copper and zinc in zinc leach residue, through analyzing its composition and phase characteristics by XRF and XRD. The method that cooperate sulfuric acid leaching with oxidant was chosen. 60 g/L H2SO4 at 60 °C for 2 h with 4% KMnO4 and liquid/solid ratio of 5..1, 84.29 % of Cu and 92.02 % of Zn are extracted. The ion concentration of copper and zinc are tested by UV-VIS spectrophotometer and EDTA titration respectively. The results show that the amount of acid is sufficient for leaching at the condition of 60 g/L H2SO4 and liquid/solid ratio of 5..1. At the same time, copper change from low valence into high valence after adding KMnO4 which strengthen the leaching, and the chemical reaction can reach balance at 60 °C for 2 h. This method has good extraction effect on copper and zinc.

Property of Water-Reducing and Crystallization on Superplasticize of the Concrete

In this paper, the effects of the water-reducing agent on the hydration property and the formation of the ettringite crystal of the concrete C3A were studied. Based on the thermometry analysis, the experiments of the effection of the hydration temperature on such concrete with both naphthalene- and polycarboxylate-type superplasticizers were conducted. The results could be drawn that the additives could prevent the slurry being hydrated in 1h, and decrease the hydration temperature. With the increasing of the additives, the hydration-inhibitory action of the additives was improved, too. The effect of the naphthalene- and polycarboxylate-type superplasticizers on the solubility property of C3A was also studied with EDTA titration, and the results showed that they can suppress the crystallization of the ettringite.

Preparation and Characterization of Lanthanum Carbonate Octahydrate for the Treatment of Hyperphosphatemia

We proposed a new approach to prepare lanthanum carbonate via reactions between lanthanum chloride and NaHCO3. In the reaction, small amount of NaHCO3solution was firstly added to the acidic lanthanum chloride solution to generate lanthanum carbonate nuclei and then NaHCO3is added to the lanthanum chloride at a constant speed. This approach makes both precipitation reaction and neutralization reaction take place simultaneously. Consequently, lanthanum carbonate is produced at low pH environment (pH below 4.0) so that the risk of generating lanthanum carbonate hydroxide is reduced. The product of the above reaction is validated by EDTA titration, elemental analysis, and XRD characterization. In addition, we established a FTIR spectroscopic method to identify La(OH)CO3from La2(CO3)2·8H2O. Lanthanum carbonate exhibits considerable ability to bind phosphate.