Emin Erdem

THE EFFECTS OF PHOSPHOGYPSUM ON THE SETTING AND MECHANICAL PROPERTIES OF PORTLAND CEMENT AND TRASS CEMENT

Abstract Phosphogypsum, the by-product of phosphoric acid industry, consists of CaSO 4 .2 H 2 O and contains some impurities such as P 2 O 5 , F and organic substances. These impurities seriously restrict the industrial use of phosphogypsum in cement industry as a retarder. In this study, the effects of phosphogypsum and purified phosphogypsum on the hydration of Portland cement and trass cement were investigated by measuring setting time, strengths of pastes, and chemical analysis as well as the electron microscopic (SEM) observation of the hydration products. It was concluded that untreated phosphogypsum can be used as a retarder directly in trass cement, whereas Portland cement requires purified phosphogypsum.

The mechanical properties of supersulphated cement containing phosphogypsum

Abstract The use of phosphogypsum in the making of supersulphated cement (SSC) and mechanical properties of the SSC pastes were investigated. Setting times of SSC pastes were shortened with increasing phosphoanhydrite and Portland cement clinker content. The SSC pastes prepared using tap water were cured in both tap water and seawater for up to 90 days. The SSC pastes containing 85% slag, 10% phosphoanhydrite and 5% clinker were found to produce the highest strength values at 90 days. The SSC pastes cured in synthetic seawater generally showed much lower strength development. Volume changes of SSC pastes hydrated in both tap water and seawater differ significantly from each other.

LIQUID-LIQUID EXTRACTION OF TRANSITION METAL CATIONS BY DIAZO COUPLING CALIX[4]ARENE DERIVATIVES

ABSTRACT The selective liquid-liquid extraction of various alkaline, alkaline-earth and transition metal cations from the aqueous phase to the organic phase was carried out by using diazo coupling calix[4]arenes [p-(4-n-butyl-phenylazo)calix[4]arene(Ll), p-(4-phenylazophenyl-azo)calix[4]arene(L2), p-(4-acetamlidazo)calix[4]arene(L5)], p-(N′-2-thiazol-2-ylsulphanyl-azo)calix(4]arene(L4) and p-(2-thiazolazo)calix[4]arene(L5)] and the phenol derivatives [2-((5-bromo-2-pyridylazo)-5-diethylaminophenol(L6) and (2-chloro-4-nitrophenylazo)-5-sec-butyl-2-phenol(L7)]. It was found that compounds LI - L6 showed some selectivity towards Ag+, Hg+ and Hg2+, while extractability of all cations was observed with compound L2 containing double diazo groups.

Distribution of uranium in the production of triple superphosphate (TSP) fertilizer and phosphoric acid

In this study the distribution of uranium, which is one of the radioactive elements present in phosphate fertilizers was investigated in different steps of the triple superphosphate (TSP) production process. The uranium in phosphate rock, phosphoric acid, phosphogypsum and TSP was extracted into the organic phase by using the TOPO extraction method. The uranium contents of these materials were determined by measuring the absorbance of the formed (pH 7.6) uranyl bromo-PADAP [uranyl(2-(5-bromo-2-pyridylazo)-5-diethylaminophenol)] complex solutions at 574 nm against blank. It was found that 50% of the uranium is dissolved in the acid during the production of phosphoric acid while the remainder is precipitated with phosphogypsum residue. The observations showed that in the second step, the sum of uranium in phosphate rock and phosphoric acid completely passed into TSP in the TSP manufacturing process.

Synthesis and Spectral Characterization of Metal Complexes of 1‐(2‐Hydroxy‐4‐methylphenylazo)‐2‐naphthol

Abstract The o,o′‐dihydroxyazo dye, 1‐(2‐hydroxy‐4‐methylphenylazo)‐2‐naphthol (HMPAN), and its metal complexes (chromium, cobalt, and iron) having the ligand to metal ratio 2:1 have been synthesized, but manganese forms a 1:1 complex. The spectral characterization of HMPAN and its complexes by IR, UV–VIS, 1H and 13C NMR spectroscopic techniques, and elemental analyses are reported.

Reconstruction of large abdominal wall defects

Abstract Reconstruction of a large abdominal defect is a technically demanding procedure. A single flap is sometimes insufficient for cover. Compound procedures play an important role in solving this problem. The case of a 35-year-old man with a large abdominal hernia as a result of a traumatic defect on the right abdomen, previously covered by a skin graft, is presented. The reconstructive method was initially expansion of posterior and upper parts of the defect and also of the tensor fascia lata in situ and then deepithelization of the previous skin graft over the intestinal serosa. The defect was covered by Prolene mesh, the upper and dorsal expanded skin was approximated, and an expanded tensor fascia lata flap was transposed to complete the cover. During follow-up examinations, there were no complications such as infection or recurrence of the hernia.