Murat Torun

Mineralization of paracetamol in aqueous solution with advanced oxidation processes

Paracetamol is a common analgesic drug widely used in all regions of the world more than hundred tonnes per year and it poses a great problem for the aquatic environment. Its phenolic intermediates are classified as persistent organic pollutants and toxic for the environment as well as human beings. In the present study, the irradiation of aqueous solutions of paracetamol with 60Co gamma-rays was examined on a laboratory scale and its degradation path was suggested with detected radiolysis products. The synergic effect of ozone on gamma-irradiation was investigated by preliminary ozonation before irradiation which reduced the irradiation dose from 5 to 3 kGy to completely remove paracetamol and its toxic intermediate hydroquinone from 6 to 4 kGy as well as increasing the radiation chemical yield (Gi values 1.36 and 1.66 in the absence and presence of ozone, respectively). The observed amount of formed hydroquinone was also decreased in the presence of ozone. There is a decrease in pH from 6.4 to 5.2 and dissolved oxygen consumed, which is up to 0.8 mg l−1, to form some peroxyl radicals used for oxidation. Analytical measurements were carried out with gas chromatography/mass spectrometry and ion chromatography (IC) both qualitatively and quantitatively. Amounts of paracetamol and hydroquinone were measured with gas chromatography after trimethylsilane derivatization. Small aliphatic acids, such as acetic acid, formic acid and oxalic acid, were measured quantitatively with IC as well as inorganic ions (nitrite and nitrate) in which their yields increase with irradiation. GRAPHICAL ABSTRACT

(Sodium Alginate/Acrylamide) Semi‐Interpenetrating Polymer Networks and their Usability on Removal of Lead, Cadmium, Nickel Ions

In this study, (sodium alginate (NaAlg)/acrylamide (AAm)) interpenetrating polymer networks (IPN) have been prepared at three different compositions, where the sodium alginate composition varies 1, 2, and 3% (w/v) in 50% (w/v) acrylamide solutions. These solutions have been irradiated with a 60Co‐γ source at different doses. The percent conversion was determined gravimetrically and 100% gelation was achieved at the 10.0 kGy dose. The swelling results at pH 7.0 and 9.0 indicated that (NaAlg/AAm)3IPN hydrogel, containing 3% NaAlg showed maximum % swelling in water, with swelling increasing in the order of Ni2+>Cd2+>Pb2+. Diffusion in aqueous solutions of metal ions within (NaAlg/AAm)IPN hydrogels was found to be Fickian character. Diffusion coefficients of (NaAlg/AAm)IPN hydrogels in water and aqueous solutions of metal ions were calculated. The maximum weight loss temperature and half life temperature for NaAlg, PAAm, (NaAlg/AAm)IPN and (NaAlg/AAm)IPN‐metal ion systems were found from thermal analysis studies. In the adsorption experiments, the efficiency of (NaAlg/AAm)IPN hydrogels to adsorb nickel, cadmium and lead ions from water was studied. (NaAlg/AAm)IPN hydrogels showed different adsorption for different aqueous solution of metal ion at pH 7.0. Adsorption isotherms were constructed for the (NaAlg/AAm)IPN‐metal ion systems. S type adsorption in the Giles classification system was found.

Preparation and Characterization of Poly(N‐Vinylpyrrolidone‐co‐Methacrylic Acid) Hydrogels

In this study, N‐vinylpyrrolidone (VP)/methacrylic acid (MAA) copolymers have been prepared at three different mole percents, the methacrylic acid composition being around 5, 10, 15%. MAA and VP monomer mixtures have been irradiated in 60Co‐γ source at different irradiation doses and percent conversions have been determined gravimetrically. ∼80% conversion of monomers into hydrogels were performed at 3.4 kGy irradiation dose. These hydrogels were swollen in distilled water at pH 4.0, 7.0, and 9.0. P(VP/MAA) hydrogel which contains 5% methacrylic acid showed the maximum % swelling at pH 9.0 in water. Diffusion of water was found to be of non‐Fickian character. Diffusion coefficients of water in P(VP/MAA) hydrogels were calculated. Initial swelling rates of P(VP/MAA) hydrogels increased with increasing pH and MAA content in hydrogels. Swelling kinetics of P(VP/MAA) hydrogels was found to be of second order. Thermal behavior of PMAA, PVP and P(VP/MAA) hydrogel were investigated by thermal analysis. P(VP/MAA) hydrogel gained new thermal properties and the temperature for maximum weight loss and temperature for half‐life of P(VP/MAA) hydrogel were determined.

Caffeine degradation in water by gamma irradiation, ozonation and ozonation/gamma irradiation

Abstract Aqueous solutions of caffeine were treated with ozone and gamma irradiation. The amounts of remaining caffeine were determined after solid phase extraction as a function of absorbed dose and ozonation time. In addition to this, some important parameters such as inorganic ions, chemical oxygen demand (COD) dissolved oxygen and total acidity changes were followed. Caffeine (50 ppm) is found to be completely decomposed at 3.0 kGy and 1.2 kGy doses in the absence of H2O2 and in 1.20 mM H2O2 solutions, respectively. In the case of gamma irradiation after ozonation, 50 ppm caffeine was removed at 0.2 kGy when the solution was ozonized for 100 s at a rate of 10 g O3 h-1 in 400 mL 50 ppm paracetamol solution.

The Removal of Cationic Dyes from Aqueous Solutions by Using Poly(N-Vinylpyrrolidone-co-Methacrylic Acid) Hydrogel Adsorbents: Effects of pH and Composition on Adsorption

In this study, poly(N-vinylpyrrolidone-co-methacrylic acid) (P(VP/MAA)) hydrogels prepared with gammaradiation were used for swelling, diffusion, and uptake of some cationic dyes which are Janus Green B (JGB) and Magenta (M). P(VP/MAA) hydrogels irradiated at 3.4 kGy were employed for swelling and diffusion studies in water and cationic dye solutions. The influence of dose, pH, relative amounts of monomers in VP/MAA monomer mixtures on swelling properties were investigated. P(VP/MAA) hydrogels were swollen in distilled water at pH 4.0, 7.0, and 9.0. P(VP/MAA) hydrogel containing 5 mole% methacrylic acid showed the maximum % swelling at pH 9.0 in water. Adsorption isotherms were plotted for JGB and M in P(VP/MAA) hydrogel systems. Consequently, it may be concluded that crosslinked P(VP/MAA) hydrogels may be successfully used in the purification of waste water containing certain textile dyes.

Analytical studies on degradation mechanism of herbicide 4-chlorophenoxyacetic acid in water by gamma/H2O2 and gamma/ozone processes

ABSTRACT Radiolytic degradation of 4-chlorophenoxyacetic acid was followed in the presence of hydrogen peroxide and ozone. The synergic effect of ozone is found to be relatively high since the amounts of detected aromatic intermediates are lower as well as the amounts of small aliphatic acids are higher. Chloride ions are one of the most important mineralization products and splitted with a yield of more than 80%. The amounts of small aliphatic acids formed in the last step before mineralization (oxalic, acetic and formic acid) were followed and their formation from 4-chlorophenoxyacetic acid was confirmed. Dissolved oxygen was consumed to form reactive radicals during irradiation. Product analysis and confirmation are followed by gas chromatography/mass spectrometry and ion chromatography. The degradation path of 4-chlorophenoxyacetic acid was suggested with determined intermediates.