Perviz Sayan

Effect of ultrasonic irradiation on crystallization kinetics of potassium dihydrogen phosphate.

The ultrasound effect applied on potassium dihydrogen phosphate was investigated in a continuous crystallization system. The studied process variables were ultrasonic power (W) and residence time. The crystal size distributions of the final products obtained with and without ultrasonic power were determined and the data were evaluated by using modified form of Abegg, Stevens and Larson (ASL) model. The supersaturation limit decreased with ultrasonic waves and the crystal morphology was modified. The average crystal size decreased in the presence of ultrasonic power. An abrasive effect was observed at a high ultrasonic power input.

Experimental investigation of green brick shrinkage behavior with Bigot’s curves

ABSTRACT The objective of this work is to define the convenient drying parameters such that the energy consumption in the brick drying process is minimized. This is an experimental study where the challenge lies in the mechanical resistance of the dried bricks which must satisfy the quality standards despite the reduction of energy consumption and the drying time. Firstly, we run multiple drying process tests and gather experimental data, and then discover the most suitable drying conditions. Secondly, the overall drying rate is improved using a Bigot’s curve analysis on the most suitable drying conditions. The results show that the drying rate increases significantly in conjunction with shorter drying time and lower energy consumption.

Impact of glutamic acid on the transformation of calcium sulfate hemihydrate to dihydrate: Characterization, equilibrium, kinetics, and thermodynamics

ABSTRACT In this study, the characteristics and mechanisms of glutamic acid adsorption on the transformation process of calcium sulfate hemihydrate to calcium sulfate dihydrate were investigated in a batch-type crystallizer. The phase transformation was followed by conductivity measurements in both the absence and the presence of glutamic acid used as additive. The structure of the samples obtained during this process was characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Brunauer–Emmett–Teller, thermogravimetric analyzer-mass spectrometer, and ATR-FTIR analyses. From the results, it was shown that the uptake of glutamic acid caused a retarding effect in the transformation rate. It was also found that the thin- and weak-layered structure was replaced by a thick and compact plate-like structure. The adsorption isotherms, kinetics, and thermodynamics were also explored to describe the process. According to the results, the Langmuir isotherm model fit quite well, as demonstrated by the high R2 value, calculated using a linear and nonlinear procedure, and the maximum adsorption amount of 169.49 mg/g. The pseudo-first-order and pseudo-second-order kinetic models were applied to analyze the kinetic experimental data, and it was determined that the adsorption of glutamic acid followed the pseudo-second-order model, which indicates that the adsorption rate depended on chemisorption. The thermodynamic results illustrated that the adsorption of glutamic acid in the transformation process was spontaneous and endothermic.

Effect of ultrasonic irradiation on morphology and polymorphic transformation of glycine

The polymorphic phase transformation of β-glycine to α-glycine was analyzed in the absence and presence of three different intensities of ultrasonic irradiation in a batch system at 25 °C. The experiments were performed to explore the effects of ultrasonic irradiation and its intensity on phase transformation time, morphology, storage stability, and filtration characteristics. The crystals obtained with and without ultrasound were characterized by X-ray diffraction (XRD). The XRD results showed that the ultrasound tended to reduce the transformation time. According to the scanning electron microscopy (SEM) images, the ultrasound had a significant effect on the crystal morphology. The highest ultrasound power applied yielded more rounded crystals compared to the crystals prepared in the absence of ultrasound. In addition to SEM analysis, detailed crystal shape analysis was performed and shape factors, namely the circularity, elongation, and convexity values, were determined quantitatively to get more information about the morphological changes related to the variations in the size and shape of the end products. From the morphological point of view, the circularity values of the crystals obtained under ultrasound were higher but the elongation values were smaller compared to the crystals obtained in the absence of ultrasound. It was also found that higher ultrasound decreased the length and width of the crystals, and the application of ultrasound increased the aspect ratio value from 0.483 to 0.657.

Assessment of propionic acid adsorption performance on the phase transformation of calcium sulfate hemihydrate to dihydrate

ABSTRACT The adsorption of propionic acid during the transformation process of calcium sulfate hemihydrate to calcium sulfate dihydrate was studied in a batch-type crystallizer with respect to contact time, additive concentration and temperature in pure media, and in the presence of propionic acid used as an additive. The adsorbent was characterized by X-ray diffraction, scanning electron microscopy and thermogravimetric analysis combined with a Fourier-transform infrared spectrometer and a mass spectrometer. The adsorption characteristics were also investigated by means of evaluating the isotherm, kinetic and thermodynamic properties. The results of this investigation showed that propionic acid can serve as a good accelerator for the transformation process from calcium sulfate hemihydrate to dihydrate.