Hüseyin Afşar

RECOVERY OF COPPER (II) AND CHROMIUM (III,VI) FROM ELECTROPLATING-INDUSTRY WASTEWATER BY ION EXCHANGE

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).

Decomposition of dyes in the textile wastewater with ozone

Abstract 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.

Spectrophotometric determination of selenium with 2-mercaptoethanol

Elemental Se, produced by the reduction of SeIV with 2-mercaptoethanol can form a zerovalent Se complex with the formula SeL6 with an excess of the ligand in basic medium. The complex is soluble in water and shows maximum absorption at 380 nm, and this was used as the basis for the spectrophotometric determination of Se. Beers law is obeyed over the concentration range 2.4–487 p.p.m. of Se. The molar absorptivity of the complex is 323 l mol–1 cm–1 and the working pH is between 10 and 13. As regards interfering ions, hydrolysable metal cations such as FeIII and CuII can be precipitated as their hydroxides prior to the analysis. Antimony(III), SbV, AsV and VV do not interfere with the determination of Se. Tellurium is also reduced by 2-mercaptoethanol, but the elemental Te formed can be filtered off. The major interferent, AsIII, can be oxidised with H2O2 to AsV prior to the analysis; the latter does not interfere with the determination of Se. The excess of H2O2 can be boiled off before the addition of 2-mercaptoethanol.

Spectrophotometric determination of hydrogen peroxide using tris(1,10-phenanthroline)iron(II)

Hydrogen peroxide reacts with iron(II) in acidic medium, and the unreacted iron(II) forms a stable complex with 1,10-phenanthroline that absorbs at 508 nm. This indirect spectrophotometric method, based on the absorbance reduction of tris(1,10-phenanthroline)iron(II) was utilised for the determination of hydrogen peroxide. The effective molar absorptivity for H2O2 is 2.22 × 104 l mol–1 cm–1. The proposed procedure is sensitive and has been applied to the analysis of commercial peroxide samples. Possible interferences are discussed.

Removal of lead by water hyacinth (eichhornia crassipes)

Abstract 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.

The Effect of the Order of Reagent Addition on the Settling Rate of Aluminium Hydroxide in the Al(III)-Na2CO3 System

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.

No-Aqueous Titrations: Potentiometric Titration of Some Primary Amines

Potentiometrie titrations of some primary amines; 1-aminobutane, 1aminopropane and 3-amino-l-phenylbutane were carried out with hydrochloric acid in toluene solvent. The same titrations were done with hydrochloric acid in methanol solvent to show the effect of amphiprotic solvent in the titrations with hydrochloric acid. For each weak base, an Sshaped Potentiometrie titration curve was obtained. As a result, toluene, which is an aprotic inert solvent, is a suitable solvent for titrating some of the weak bases potentiometrically.

Indirect spectrophotometric determination of hydrogen peroxide

SummaryA 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 5.37×104 mol−1 cm−1 at pH 1.7. The lower limit of determination is 1.85×10−7 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.

Reduction of selenium(IV) and complexation of selenium(0) with 2-mercaptoethanol

Selenium(IV) can be reduced to the elemental state with 2-mercaptoethanol in weakly acidic, neutral and alkaline media. In this redox reaction, 2-mercaptoethanol is oxidised to bis(2-hydroxyethyl) disulphide. The reaction rate for the reduction of H2SeO3 with 2-mercaptoethanol is directly proportional to the square of the ligand concentration and inversely proportional to the square root of the hydrogen ion concentration. When the ligand, L, is in excess, the elemental Se can re-dissolve in the form of a complex, i.e., SeL6, where the zero valency of Se is retained as in metal carbonyl compounds. The SeL6 complex is stable only in polar solvents. The maximum absorption of the complex in aqueous solution was measured at 380 nm.

Potentiometrie Titration of P-Anisidine and P-Toluidine in Non-Aqueous Media

Potentiometrie titrations of p-anisidine and p-toluidine were carried out with hydrochloric acid in toluene solvent. The same titrations were done with hydrochloric acid in methanol solvent to show the effect of amphiprotic solvent in the titrations with hydrochloric acid. For each weak base, an Sshaped Potentiometrie titration curve was obtained. As a result, toluene, which is an aprotic inert solvent, is a suitable solvent for titrating some of the weak bases potcntiometrically.