Effect of power ultrasound on crystallization characteristics of magnesium ammonium phosphate

Abstract

Magnesium ammonium phosphate (MAP) crystallization could be utilized for the recovery of phosphorus from wastewater. However, the effectiveness of the recovery is largely determined by the crystallization process, which is very hard to be directly observed. As a result, a specific ultrasonic device was designed to investigate the crystallization characteristics of MAP under various ultrasonic conditions. The results demonstrated that the metastable zone width (MZW) narrowed along with the rising of the ultrasonic power. Similarly, for the 6mM MAP solution, with the ultrasonic power gradually enhanced from 0W to 400W, the induction time was shortened from 340s to 38s. Meanwhile, the crystallization rate was accelerated till the power reached 350W, and then remained a constant value. It can be observed from the scanning electron microscopy (SEM), the MAP crystal became bigger in size as well as the crystal size distribution (CSD) became broad and uneven, with the increase of ultrasonic power. The results indicate that the crystallization process enhanced by power ultrasound could be used as an effective method to eliminate and recover the phosphorus from wastewater.

Experimental Investigation of p-Xylene Crystallization Characteristics and Ultrasound Enhancement Mechanism

“…However up to now, no studies have been conducted on ultrasound-enhanced PX crystallization process, and the exploration of PX crystallization thermodynamics and nucleation mechanism is also not in-depth. The mechanism of ultrasound enhancement has not yet reached a consensus. − Many studies in the literature have only analyzed the apparent effect of ultrasonic on crystallization without detailed analysis of its mechanism. − These cause difficulties for ultrasonic-enhanced PX crystallization technology development.…”

Effect of magnetic field on sodium arsenate metastable zone width and crystal nucleation kinetics for crystallization

“…The metastable zone, which represented the interval between solubility and supersolubility curves, played a pivotal role in crystallization nucleation 15 . When the concentration of the solution is the same as the solubility of the solute, which usually referred as a saturated solution.…”

Nucleation triggering methods in supercooled phase change materials (PCM), a review

“…time from the start of ultrasonic irradiation to the appearance of the first crystal), on water [123,124,134], salt hydrates [125,126,[135][136][137] or sugar alcohols [138]. The time for heat release (recalescence) is also improved by ultrasonic irradiation [51,139,140], where the influence of a large number of ultrasonic parameters was studied. The choice of the solvent also appears to be critical for the efficiency of crystallization triggered by ultrasound [141].…”

“…where the nucleation appears at lower supersaturation degree, the induction time is shortened by an increase in ultrasonic power [139]. The crystal appearance probability was dependent on several parameters such as the supercooling degree before sonication [122,126], ultrasonic power [124,126,139,145], an excess of water in hydrated salts [126], the size of the probe [145], the immersion depth of probe [145], the test tube material [146], or the number of bubble nuclei [134]. A model was also developed by Zhang [134] to simulate the nucleation by ultrasound, and correlated with an experimental study on ice.…”