Solvothermal synthesis of porous organic cage CC3 in the presence of dimethylformamide as solvent

Morphology, and crystal product of porous organic cage CC3, was modified by the use of a novel and non-traditional high dielectric constant solvent dimethyl formamide.

Development of Couette-Taylor Crystallizer in Cooling Crystallization: Promotion of Size Distribution of L-lysine

The Couette-Taylor (CT) crystallizer was developed to promote the size distribution of L-Lysine crystal product in cooling crystallization. When using the CT crystallizer, the size distribution of crystal product was much narrower than that of the conventional Stirred tank (ST) crystallizer. Here, the coefficient size distribution (n) in CT crystallizer was quite large as 3.43, while it was only 2.17 in ST crystallizer at the same 360 rpm of agitation or rotation speed. This result indicated that the CT crystallizer was much more effective than the ST crystallizer in terms of the size distribution of L-lysine crystal products in cooling crystallization. The advantage of CT crystallizer over the ST crystallizer was explained in terms of the high energy dissipation of Taylor vortices flow, where it was 7.6 times higher than that of random fluid motion in conventional ST crystallizer. As such, the supersaturation profile in the CT crystallizer was much more homogeneous than that in the ST crystallizer, which resulted in promotion of size distribution L-lysine crystal product.

Recovering phosphorus as struvite from the digested swine wastewater with bittern as a magnesium source

Recovering nitrogen and phosphorus through struvite (MgNH4PO4·6H2O) crystallization from swine wastewater has gained increasing interest. However, swine wastewater contains complex compositions, which may hinder the formation of struvite crystal and affect the purity of the precipitates by forming other insoluble minerals. In this work, experiments were carried out to evaluate struvite precipitation in the anaerobically digested swine wastewater, with dosing bittern as a low-cost magnesium source. Exceeded 90% phosphate removal and 23–29% ammonium reduction were obtained. FTIR, XRD and mass balance analysis were combined to analyze the species of precipitated minerals. Results showed that the precipitates were struvite, mixed with amorphous calcium phosphate (ACP) and brucite. The presence of Ca2+ diminished the percentage of struvite and gave rise to ACP formation. Controlling pH below 9.5 and bittern dosage above 1% (w/w) could inhibit ACP precipitation and harvest a highly pure struvite crystal product.

The Effect of Organic Macromolecules on the Vateritet to Calcite Transformation

ABSTRACTSmall quantities of acidic macromolecules were added to crystallizing calcium carbonate in an attempt to engineer crystal growth. The additives are simple analogs to those molecules found in close association with the mineral phase in biological ceramics. When 5 or 10 ppm of the four additives (poly-L-glutamate, poly-L-aspartate, polyacrylate and polymaleate) were added to aqueous suspensions of metastable vaterite, the transformation to calcite was markedly retarded, and the morphology of the final crystal product was altered. The two polypeptides were most effective in inhibiting calcite nucleation and growth; they also promoted vaterite aggregation, and caused the formation of large calcite crystals.

Particle size distribution of agglomerated crystal product from a continuous crystallizer

Relationships have been derived for the particle size distribution in a continuous crystallizer operating in a steady-state regime, where agglomeration of the primarily generated crystalline particles takes place. The derivation was made for a constant kinetic coefficient of agglomeration (independent of the particle size) and for a negligible particle growth rate. The relatioships are used to interpret the particle size distribution of calcium carbonate precipitated from 0.2 mol dm-3 solutions of calcium chloride and sodium carbonate in a laboratory continuous crystallizer. Anomalous shapes of the size distributions of small particles frequently observed in continuous crystallizers are discussed in terms of the agglomeration phenomenon.

Determination of crystallization kinetics from batch experiments II

Relations have been derived for the size distribution of crystal product of batch crystallization with constant and variable supersaturation, applicable where the distribution cannot be approximated by the relation holding for continuous MSMPR crystallizers. In the cases considered, relative kinetic data, but not the kinetic exponents of nucleation and crystal growth, can be evaluated for model experiments involving any variation of supersaturation with time. Application of the relationships is illustrated by treating data for potassium aluminium sulphate precipitation.