Hüseyin Afsar’s research while affiliated with Yıldız Technical University and other places

A modified Lassaigne method was developed for N determination based on fusion of the organic substance with metallic Na, conversion of the cyanide in the aqueous leachate to thiocyanate by ammonium polysulfide treatment, and colorimetric measurement of the thiocyanate formed by the addition of excessive ferric ions in acidic medium. The mean molar absorptivity of the Fe(NCS)2+ complex at 480 nm is 2.96 x 10(3) L/mol x cm, enabling quantitation of 0.25-7.72 ppm N (linear range) in the final solution. The relative amounts of Na, (NH4)2S2, and Fe(III) with respect to nitrogen in the analyte were optimized. The developed method was successfully applied to the determination of N in various brands of baby food, and it was compared statistically with the conventional Kjeldahl and elemental analysis methods. Protein nitrogen in a number of meat products was also precisely determined by the developed method. Thus, the total digestion time of the conventional Kjeldahl method was reduced considerably (e.g., to approximately 15 min for a dried sample) with a relatively simple spectrophotometric method requiring no sophisticated instrumentation.

The effects of several factors on the settling rate of aluminiumhydroxide were investigated during chemical coagulation using aluminium salts. Experimental variables were pH, aluminium (III) concentration and the order of addition of reagents. Experiments were carried out at pH 5–8 and rapid settling was achieved when aluminium (III) solutions were added to Na2CO3 solutions near neutral pH, close to the minimumsolubility pH of Al(OH)3. For a narrow range of total Al concentration where Al(III) species were supersaturated with respect to the solid phase, Al(III)-added-to-carbonate type mixtures yielded a higher settling rate than mixtures obtainedby the reverse order of reagent addition. The results were interpreted by comparing the rates of formation of polymer andsolid (amorphous Al(OH)3) phases. It was concluded that Al(III) coagulants should be added to water containing natural or artificially incorporated carbonate alkalinity for rapid settling of Al(OH)3 flocs.

Two laboratory-scale separation processes have been developed for the recovery of copper (II) from acidic and cyanide-containing alkaline wastewater of electroplating industries. Acidic bath wastes were treated with Dowex 50X8, a strongly acidic cation-exchange resin, and the retained copper was eluted with H2SO4. The cyanide-containing alkaline bath waste was first oxidized with excessive hypochlorite, then neutralized, and recovered by the use of Amberlite IRC-718 chelating resin. Copper was eluted with H2SO4.The two different valencies of chromium have been recovered from electroplating-industry wastewater by different separation processes: The predominant valency, Cr(VI), was retained on a strongly basic Dowex 1X8 resin and eluted with a NaCl and NaOH solution. Alternatively, Cr(III), either existing originally in electroplating-industry waste-rinse mixtures or converted from Cr(VI) by reduction with Na2SO3, could be recovered by a weakly acidic Amberlite IRC-50 resin and eluted with a solution containing H2O2 and NaOH. Where plating industry wastes contain high levels of organic contamination, Cr(VI) would be naturally reduced to Cr(III) upon acidification, and it may be more economical to recover all chromium as Cr(III).

A Spectrofluorometric method for microdetermination of H2O2 has been developed. The method is based on the oxidation of hydrogen peroxide with ceric ion in acid solution and measurement of the fluorescence during titration of the Ce(III) ions produced. The fluorescent species have excitation and emission maxima at 260 and 360 nm, respectively. The detection limit of measurement by this method was 0.1 ppm hydrogen peroxide.

A method is described for the determination of Cr(VI) and total chromium by FAAS. Cr(VI) is separated from Cr(III) by adsorption on melamine-formaldehyde resin. After elution of Cr(VI) with 0.1 mol/l NaAc solution, it is analysed by FAAS. Total chromium is determined by FAAS after conversion of Cr(III) to Cr(VI) by oxidation with hydrogen peroxide, total Cr(VI) is concentrated as above. If the total concentration of chromium is sufficient, the determination can be directly made by FAAS. Cr(III) can then be calculated by subtracting Cr(VI) from the total Cr. This method was successfully applied to the determination of chromium in lake water.

Ozone treatment of textile wastewater and recycling of this treated water as process water have been investigated. Effects of pH, temperature,dye concentration and UV radiotion on the treatment of some azo dyes such as N‐ROT‐GRE, N‐ORANGE and INDISOL‐RUBINOL with ozone were investigated. Temperature was found not to effect the decomposition rates of these dyes. The ozone treatment was found to be more ecomomical with the diluted dye solution than with concentrated solutions. No positive effect of U V radiotion on decomposition of dyes were observed. When the flow rate of ozone was 0.2 mg / sec. chemical oxygen demand ( COD ) decreases of 44 mg and 36.6 mg per minute were found for the wastewaters of cotton dying and wool dying respectively.

Various factor effect on removal of lead (II) by the water hyacinth (Eichhornia crassipes) were investigated. The plants were exposed to lead concentration ranging from 1 to 128 ppm. As the initial lead concentration increased, lead uptake was decreased. The uptake of lead was little effected by pH in the range of 4–8 but the effect of pH increased outside of this range. When the solution volume per plant was increased the total amount of lead uptake also increased. The effect of various concentration of EDTA on the lead uptake was examined. It was observed that removal of lead was decreased by increasing the concentration of EDTA. Stirring the solution increased removal of lead.

A method for the indirect spectrophotometric determination of H2O2 is based on its oxidation with chlorine in basic medium and measurement of the unreacted Cl2 by the colour reaction with o-tolidine at 438 nm. The effective molar absorptivity for H2O2 with o-tolidine is 5.37104 mol–1 cm–1 at pH 1.7. The lower limit of determination is 1.8510–7 mol/l or 6.29 ppb. Br–, I–, NO– 2, Pb2+ and Sn2+ interfere even in small amounts, but are not present in commercial H2O2.

The flotation of oxidized Amasra Coal which was collected between 1973–1978 and, stored in the atmospheric conditions was examined In this work. Coal samples were fractioned by wet screening to +0.560 mm, −0.500 + 0.140 mm, −0.140 mm particle sizes and first fraction was ground to −0.560 mm before flotation. Motorin and pine oil which had been heated at 125° C for 5 hours were used ns flotation reagents. The influence of impeller speed, aeration rate, solid concent of the pulp, reagent amounts were examined and optimum values were determined. Increase of the pine oil amount added to the pulp, increased the coal. recovery on the flotation of this oxidized coal.