Textile industries produce effluent wastewater that, if discharged, exerts a negative impact on the environment. Thus, it is necessary to design and implement novel wastewater treatment solutions. A sequential treatment consisting of ligninolytic co-culture with the fungi Pleurotus ostreatus and Phanerochaete crhysosporium (secondary treatment) coupled to TiO 2 /UV photocatalysis (tertiary treatment) was evaluated in the laboratory in order to discolor, detoxify, and reuse textile effluent wastewater in subsequent textile dyeing cycles. After 48 h of secondary treatment, up to 80 % of the color in the wastewater was removed and its chemical and biochemical oxygen demands (COD, and BOD 5 ) were abated in 92 % and 76 %, respectively. Laccase and MnP activities were central to color removal and COD and BOD 5 abatement, exhibiting activity values of 410 U L −1 and 1 428 U L −1 , respectively. Subjecting wastewater samples to 12 h of tertiary treatment led to an 86 % color removal and 73 % and 86 % COD and BOD 5 abatement, respectively. The application of a sequential treatment for 18 h improved the effectiveness of the wastewater treatment, resulting in 89 % of color removal, along with 81 % and 89 % COD and BOD 5 abatement, respectively. With this sequential treatment a bacterial inactivation of 55 % was observed. TiO 2 films were reused continuously during two consecutive treatment cycles without thermic reactivation. Removal percentages greater than 50 % were attained. Acute toxicity tests performed with untreated wastewater led to a lethality level of 100 % at 50 % in Hydra attenuata and to a growth inhibition of 54 % at 50 % in Lactuca sativa. Whereas sequentially treated wastewater excreted a 13 % lethality at 6.25 % and an inhibition of 12 % at 75 % for H. attenuata and L. sativa, respectively. Finally, sequentially treated wastewater was reused on dyeing experiments in which 0.86 mg g −1 adsorbed dye per g of fabric, that is equivalent to 80 % of dye adsorption. AM. A novel textile wastewater treatment using ligninolytic co-culture and photocatalysis with TiO 2,

Controlled doping of quaternary alloys of In x Ga 1−x As y Sb 1−y with tellurium is fundamental to obtain the n-type layers needed for the development of optoelectronic devices based on p-n heterojunctions. InGaAsSb epitaxial layers were grown by liquid phase epitaxy and Te doping was obtained by incorporating small Sb 3 Te 2 pellets in the growth melt. The tellurium doping levels were in the range 10 16 -10 17 cm −3 . We have used lowtemperature photoluminescence (PL) spectroscopy to study the influence of the Te donor levels on the radiative transitions shown in the PL spectra. The PL measurements were done by exciting the samples with the 448 nm line of an Ar ion laser with varying excitation powers in the range from 10 to 200 mW. For the low-doped sample the PL spectrum showed a narrow exciton-related peak centred at around 610 meV with a full width at half maximum (FWHM) of about 7 meV which is evidence of the good crystalline quality of the layers. For higher Te doping, the PL spectra show the presence of band-to-band and donor-to-acceptor transitions which overlap as the Te concentration increases. The peak of the PL band shifts to higher energies as Te doping increases due to a band-filling effect as the Fermi level enters into the conduction band. From the peak energy of the PL spectra, and using a model that includes the band-filling and band-shrinkage effects due to the carriers, we have estimated the effective carrier concentration due to doping with Te in the epilayers.

Evidences of the passivation effect are given when thin films of CdS are deposited on GaSb crystalline substrates, using a bath chemical deposition method. The passivation process is studied through photoacoustic and photoluminescence experiments. The surface recombination velocity calculated from photoacoustic measurements decreases and the radiative recombination rate as measured from photoluminescence spectra increases when the nominal S/Cd ratio in the layer deposition solution increases. The influence of the CdS layer thickness on the surface passivation of GaSb is also studied.

Objective. Removal and detoxification of azo dye by photocatalysis with TiO 2 . Materials and methods. TiO 2 films were prepared by sedimentation at pH 1.3, using as support a borosilicate glass, annealed for 1 hour at 450 °C. Physical characterization was performed by Scanning Electron Microscopy, X-ray diffraction and UV/VIS spectrometry. Dye Black Reactive 5 removal was carried-out in a quartz photo-reactor. Results. Optical characterization revealed the films displayed evident TiO 2 spherical particles of various irregular sizes, porous, and without fractures. The average crystal size was 77.5 nm and 77.7 nm for 50 °C (dried temperature) and 450 ºC (annealed temperature) respectively. The energy of the band gap (GAP) was 3.02 and 2.68 eV respectively. Maximum concentration of dye that negatively affected color removal was 80 mg/L (17%). At lower dye's concentrations (10, 50 and 70mg/L) decolorization was greater than 80%. TiO 2 films were reused for five consecutive cycles of 6 hours at 10 mg/L (>80%), and three cycles of 10 hours at 70 mg/L (> 80%). Toxicity results demonstrate that Daphnia magna was more sensitive than Lactuca sativa. Conclusions. TiO 2 films obtained by sedimentation demonstrated a high reactive black 5 decolorization and COD removal (86% and 100%), as well as toxicity reduction.Key words: photocatalysis with TiO 2 , sedimentation techniques, reactive black 5, Lactuca sativa and Daphnia magna. ResumenDecoloración simultánea y la desintoxicación de reactivo negro 5 con TiO 2 depositadas sobre el vidrio de borosilicato por la técnica de sedimentación. Objetivo. Decolorización y disminución de la toxicidad de un azo colorante usando fotocatálisis con TiO 2 . Materiales y métodos. Las películas de TiO 2 fueron crecidas por sedimentación a pH 1,3 empleando vidrio de borosilicato como sustrato. La caracterización física se realizó por medio de microscopía electrónica de barrido, difracción de rayos X y espectrometría de absorción UV/vis. Los estudios de remoción del colorante Negro Reactivo 5, se realizaron en un fotoreactor de cuarzo. Resultados. De acuerdo con la caracterización óptica, las películas de TiO 2 presentaron partículas esféricas, con diferentes tamaños, irregulares y sin fracturas. El tamaño del cristal fue 77,5 nm y 77,7 nm para 50 y 450º C y la energía de banda prohibida fue 3,02 y 2,68 eV, respectivamente. La concentración máxima del colorante que afectó negativamente la remoción de color fue 80 mg/L (17%). A concentraciones más bajas de NR5 (10, 50 y 70 mg/L) la decoloración fue superior al 80%. Las películas de TiO 2 se reutilizaron por 5 ciclos de 6 horas a 10 mg/L y 3 ciclos de 10 h a 70 mg/L. Los estudios de toxicidad en Lactuca sativa y Daphnia magna demostraron que D. magna fue más sensible que L. sativa. Conclusión. Las películas de TiO 2 crecidas por sedimentación decoloraron el colorante negro reactivo 5 en un 86% y removieron la demanda química de oxígeno en un y 100%, igualmente redujeron la toxicidad.Palabras clave: fotocatálisis con TiO 2 , técnica de sed...

No abstract