A. Kadir Özer

Effect of ultrasound on the dissolution of colemanite in H2SO4

This paper deals with the dissolution of colemanite in sulfuric acid, in the absence and presence of ultrasound. By nonlinear regression analysis, a modified Avrami-typeA equation was fitted to kinetic data and the activation energy was found to be 30 kJ/mol in both cases. The effect of ultrasound is on the pre-exponential factor A in the Arrhenius equation. An empirical relation is also given, which relates the rate constant to ultrasound power.

Investigation of the Solubilities of Sulfated and Ground Phosphate Rock after Sulfation in H2SO4 Solution

Oz In this study, the effects of temperature and acid concentration on the dissolution of the sulfated and ground after sulfation phosphate samples in sulfuric acid solution obtained after flue gas desulfurization were investigated and the results were compared for both samples. It was observed that the dissolution rate increased as the temperature and acid concentration increased during the dissolution of sulfated and ground after sulfation phosphate samples. It was shown that the dissolution reaction can be divided into two regions, with different rate controlling steps for both samples. The controlling step was determined as pseudo-first order reaction at low conversions and diffusion through the product (ash) layer at high conversions.

Investigation of the Thermal Behavior of Polypyrrole/Carbon Nanotube Composites and Utilization as Capacitive Material or Support for Catalysts

In this study, polypyrrole (PPy)/carbon nanotube (CNT) composites were synthesized by in situ chemical oxidative polymerization of a pyrrole monomer on CNT. Two different types of CNT having different structural properties were used. The composites were characterized using BET surface area analysis, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) techniques. Thermal decomposition kinetics of PPy/CNT composites was studied by thermal gravimetric analysis techniques (TG/DTG (differential thermal gravimetric)) at different heating rates (2.5, 5, 7.5, and 10 K min−1). Kinetic parameters of the composites were obtained from the TG and DTG curves using the Kissinger–Akahira–Sunose (KAS) and Flynn–Wall–Ozawa (FWO) models. The electrochemical capacitive properties of the composites were investigated by the cyclic voltammetry (CV) technique. Pt nanoparticles were decorated on the plain CNTs and composite materials via the microwave irradiation method.

Fosfat Kayasının İzotermal Olmayan Bozunma Kinetiği

Mazıdağı fosfat kayasının inert ( N2) ortamda ısıl bozunma kinetiği 2, 5, 10 ve 20 K dak-1 ısıtma hızlarında termal analiz teknikleri (TG/DTG) ile incelendi. TG ve DTG ölçümlerinde 873-1173 K sıcaklık aralığında fosfat kayasının ısıl bozunmasının tek basamaklı bozunma olduğu görüldü. TG ve DTG eğrilerinden elde edilen verilere eş dönüşüm metotları Kissinger–Akahira–Sunose (KAS) ve Flynn-Wall-Ozawa (FWO)uygulanarak aktivasyon enerjileri sırasıyla 170 ve 187 kJmol-1 olarak bulundu. Fosfat kayasının ısıl bozunmasının çekirdeklenme ve büyüme (-ln(1-α)2/3) mekanizmasına göre meydana geldiği belirlendi. Ön üssel faktör (ln A) ise 20.47 olarak tespit edildi. The kinetics of thermal decomposition of the phosphate rock was studied by means of thermal analysis techniques (TG/DTG) in inert nitrogen (N2) atmosphere at heating rates of 2, 5, 10, and 20 K min-1. TG and DTG measurements indicated that calcination of the phosphate rock has single-stage degradation in between 873-1173 K. Kissinger– Akahira–Sunose (KAS) and Flynn-Wall-Ozawa (FWO) isoconversional methods were applied to the data obtained from TG and DTG curves and the activation energies were found as 170 ve 187 kJmol-1, respectively. It was determined that the thermal decomposition mechanism of phosphate rock was occurred via nucleation and growth (-ln(1-α)2/3) mechanism. Pre-exponentional factor (lnA) was determined as 20.47. Anahtar kelimeler: Fosfat kayası, Eş dönüşüm metotları, Aktivasyon enerjisi, İzotermal olmayan kinetik analiz.