Manipulation of Morphology, Particle Size of Barium Sulfate and the Interacting Mechanism of Methyl Glycine Diacetic Acid

In this paper, methyl glycine diacetic acid (MGDA) was found to have great influence on the morphology and particle size of barium sulfate. The effects of additive, concentration, value of pH and reaction temperature on the morphology and particle size of barium sulfate were studied in detail. The results show that the concentration of reactant and temperature have little effect on the particle size of barium sulfate. However, the pH conditions of the solution and the dosage of MGDA can apparently affect the particle size distribution of barium sulfate. The particle size of barium sulfate particles increases and the morphology changes from polyhedral to rice-shaped with the decreasing of the dosage of MGDA. In solution with higher pH, smaller and rice-shaped barium sulfate was obtained. To investigate the interacting mechanism of MGDA, the binding energy between MGDA and barium sulfate surface was calculated. It was found that the larger absolute value of the binding energy would result in stronger growth inhibition on the crystal face. Finally, the experimental data and theoretical calculations were combined to elucidate the interacting mechanism of the additive on the morphology and particle size of barium sulfate.

Using Molecular Modelling to Understand and Predict the Impact of Organic Additives as Crystal Growth Modifiers

Empirical molecular modelling was used to investigate the impact of organic additives on crystal morphology and inhibition. The replacement energy was found to correlate reasonably well with the degree of inhibition as determined from conductivity data. The replacement energy was also able to predict the barium sulfate face on which additive adsorption was most likely. While the ability of the organic functional groups to sit in the vacant sulfate lattice positions (the so-called ‘lattice matching’ criteria) appears intuitively sensible, it was found that this is not a sufficient criterion to predict real behaviour. A better criterion is the overall replacement energy as it takes into consideration the number of Ba–Oorganic interactions and whether the adsorption process overall is energetically favourable (by including the hydration energy of the ions). Thus, the replacement energy can successfully predict the effect of organic molecules on the crystal growth modification of barium sulfate.

BaCO3 and NH3SO3 as precursors for the hydrothermal synthesis of BaSO4

BaCO₃ and NH₃SO₃ can be used as BaSO₄ precursors. The morphology, which can be obtained, spans different size and shapes.

Hierarchically nanostructured barium sulfate fibers

BaSO(4) nanostructures with controlled morphologies were successfully produced via one-step process through precipitation of BaSO(4) in aqueous and organic media. The synthesis is carried out by mixing solutions of BaCl(2) and Na(2)SO(4) in presence of EDTA (disodium ethylenediaminetetraacetic acid) at room temperature. The influence of the reaction conditions such as initial reactants concentration, pH, EDTA/[Ba(2+)] ratio and aging on the BaSO(4) nanoparticles organization is studied. Using EDTA in aqueous media, spherical secondary particles of 500 nm diameter are obtained, which are formed by 4 nm size primary particles. With dimethyl sulfoxide and small amounts of water (5%) and EDTA, the aging process allows the production of long homogeneous fibers, related to hierarchical organization of BaSO(4) nanoparticles. Direct observation of self-assembling of primary particles by HRTEM allows proposing a mechanism for fiber formation, which is based on multipolar attractions that lead to a brick-by-brick organization along a preferential orientation. Results evidence the role of EDTA as controlling agent of the morphology and primary and secondary mean particle size.

The interaction of EDTA with barium sulfate

Ethylenediaminetetraacetic acid (EDTA) is a known complexing agent that interacts with a host of cations. In this paper, various techniques are used to elucidate the mechanism of interaction between EDTA and barium sulfate surfaces. It is shown that complexation with metal ions is not sufficient to explain the inhibition of barite crystallization but that other processes such as chemisorption must also occur. EDTA is shown to always adsorb as the mono-protonated species - suggesting that the molecule is able to lose a proton when it adsorbs at lower pH. Molecular modelling shows that the interaction of the surface barium ions with the carboxylate group is an important one. Finally, in situ turbidity measurements provide information about the mechanism of nucleation/growth modification. It is found that the EDTA molecule inhibits barium sulfate nucleation and that this could be its primary means of inhibiting precipitation of barium sulfate.