Phenol In Aqueous Suspensions Research Articles

The characteristics and photocatalytic activities of silver doped ZnO nanocrystallites

Silver ions doped ZnO nanocrystallites were synthesized from the precursor of Ag-doped Zn5(CO3)2(OH)6 applying hybrid induction and laser heating (HILH) techniques. The physical properties of prepared nanoparticles were characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and UV-Vis methods. The results of the photocatalytic degradation of methylene blue (MB) and phenol in aqueous suspensions showed that silver ions doping greatly improved the photocatalytic efficiency of ZnO nanocrystallites. This was attributed to the change of surface properties of metal ions doped semiconductor, such as O vacancies, crystal deficiencies, and increased specific surface area (SSA). Increasing the amount of silver ions resulted in increased lattice deficiency and hence enhanced the photocatalytic activity. The quantum confinement of silver ions doped ZnO nanocrystallites was also investigated in this study.

Influence of some aromatic and aliphatic compounds on the rate of photodegradation of phenol in aqueous suspensions of TiO 2

The influence of 3-nitrophenol, 4-nitrophenol, pentachlorophenol, ethanol, 2-propanol, ethanoic acid and ethanedioic acid on the photodegradation rate of phenol in an aqueous suspension of TiO 2 (anatase) irradiated in the near-UV region was investigated. Binary mixtures of organic compound and phenol in molar ratios of 1:1 and 10:1 were used for the photoreactivity experiments performed in a batch reactor. The mineralization rate of all the mixtures was also monitored by measuring the total organic carbon (TOC) concentration. The reactivity results indicate that the photodegradation rate of phenol is mainly determined by the total amount of aromatic substrates present in the reacting medium independently of their nature, while it is scarcely affected by the presence of aliphatic compounds. The TOC results indicate that the mineralization rate of aromatic compound-phenol mixtures is sensitive to the mixture composition, and the simultaneous presence of phenol and aliphatic compounds negatively affects the mineralization rate. A tentative explanation of the above behaviour is proposed by taking into account (i) the similar manner of photoadsorption of phenol molecules and of the other aromatic compounds on the active surface site(s), (ii) the different sites of photoadsorption for aromatic and aliphatic substrates and (iii) the possible formation of stable intermediate compounds from the degradation products of phenol and aliphatic compounds.

Light-induced oxidation of phenol over ZnO powder

The photo-oxidation of phenol in aqueous suspensions of ZnO was studied under different experimental conditions. It was observed that the yield of phenol decomposition decreases with increasing initial phenol concentration, decreasing oxygen concentration in solution and increasing pH. The amount of hydrogen peroxide formed during irradiation decreases with increasing phenol concentration over the range 10 −4 – 10 −2 M. On the other hand, ZnO shows a certain degree of instability. After 60 min of irradiation of a 10 −3 M phenol solution containing 8 g l −1 of ZnO in suspension. 0.24% of the initial ZnO was photodecomposed. From the results of the present work it can be concluded that in diluted solutions phenol is oxidized preferentially by homogeneous reaction with OH radicals, while for concentrated solutions the oxidation can proceed by reaction with photogenerated holes.