Patricio Peralta-Zamora

Evaluation of ZnO, TiO2 and supported ZnO on the photoassisted remediation of black liquor, cellulose and textile mill effluents

Treatment of effluent from the cellulose and textile industries by applying a heterogeneous photocatalytic procedure using UV-light and free and supported catalysts is reported. When Krafi and textile effluents are submitted to UV-irradiation in the presence of free Ti02 and ZnO or silica gel supported ZnO, the colour fades progressively to reach substantial decolorization ratios. This decolorization process is accompanied by a considerable reduction of total phenol concentrations in the black liquor and final effluent. For bleaching mixture, the reduction of phenol concentration is not significant, and on the contrary, for textile effluents an increase of phenolic compound concentrations is observed during the initial phase of the photocatalytic process The progressive degradation of the different chemical species contained in the effluents was demonstrated by HPLC analysis and total organic carbon contents determination. This degradation permitted an important reduction of the acute toxicity of the effluents. 019% Elsevier Science Ltd

Effluent Treatment of Pulp and Paper, and Textile Industries using Immobilised Horseradish Peroxidase

Horseradish peroxidase immobilisation on several supports and its utilisation for decontamination of effluent from paper and textile industries was evaluated. Among the supports, Amberlite IRA-400 ion exchange resin showed the best results for enzyme immobilisation, efficiency of colour removal and degradation of phenolic species from Kraft E1 effluent (first alkaline extraction), bleaching mixture effluent and black liquor. Effluent decolorisations over 50% were obtained after 4 h of enzymatic treatment, without significant adsorption of coloured species by the support. Decolorisation in pre-irradiated Kraft E1 effluent was kinetically more efficient than in a non-irradiated one. For this reason, the combined photo-enzymatic decolorisation procedure appears to be an efficient decontamination method with great potential for industrial effluent treatment.

Pre-concentration of rare earths using silica gel loaded with 1-(2-pyridylazo)-2-naphthol (PAN) and determination by energy dispersive X-ray fluorescence.

The determination of a single rare earth element in a mixture with other species of this family is a very challenging problem in analytical chemistry due to the close similarity of their chemical properties. In this work, a liquid-solid extraction procedure for praseodymium, neodymium, samarium and yttrium mixtures and subsequent determination by energy dispersive X-ray fluorescence spectrometry is described. The pre-concentration procedure, which involves the use of silica modified with 1-(2-pyridylazo)-2-naphthol, permits complete recovery of the rare earths and significant sensitivity enhancement in comparison with direct determination in the aqueous phase. Determinations in quaternary mixtures show typical precisions and accuracies of 3% and 5%, respectively.

Hidrólise enzimática de casca de arroz utilizando-se celulases: efeito de tratamentos químicos e fotoquímicos

In the present work we reported the study of rice hull enzymatic hydrolysis using a commercial cellulase preparation. The results showed that previous treatment with light and sodium chlorite inhibits the enzymatic process (31.4 and 11.8%, respectively) while hydrogen peroxide and ozone favoured the enzymatic production of reducing sugars (5.9 and 54.9%, respectively). Studies performed by quimiluminescence showed that the chlorite treatment produced the most significant change in the structure of rice hull. Nevertheless, this treatment did not favour the subsequent enzymatic process. Photomicrographs obtained from rice hull hydrolysates showed that pre-treatment changed mainly the inner epidermis and parenchyma cell and that they did not change cellular organization of the hull.

Zirconium and hafnium determination by energy dispersive X-ray fluorescence with solid phase preconcentration

Two preconcentration methods has been developed for simultaneous determination of zirconium and hafnium by energy dispersive X-ray fluorescence (EDXRF). The first method is a liquid-solid extraction procedure with the use of an anionic exchange resin modified with xylenol orange. The second is a precipitation procedure carried out in the presence of lanthanum. Both methods permit significant enhancement of sensitivity in comparison with direct measurement in the aqueous phase. The applicability of both procedures for the preconcentration of Zr and Hf prior to their determination by EDXRF was demonstrated by analyzing synthetic mixtures and a sample of zirconium ore. The results obtained with the use of the modified resin show relative standard deviation of about 4% and good agreement with those obtained by spectrographic analysis.

Decolorization of Pulp Mill Effluents with Immobilized Lignin and Manganese Peroxidase from Phanerochaete Chrysosporium

The immobilization of lignin and manganese peroxidase produced by Phanerochaete chrysosporium on Amberlite IRA-400 resin and its utilization on the remediation of effluents from the pulp and paper industry was evaluated. The ion exchange resin shows great efficiency for the enzyme immobilization, allowing almost total enzymatic activity retention in a short period at (30 min). The immobilized enzyme was very efficient to removing colour and phenolic species from Kraft E1 effluent with insignificant adsorption of coloured species by the support. Effluent decolorization of over 50% for 3 h of enzymatic treatment was obtained. For bleaching mixture effluent and black liquor, substantial decolorization ratios were also observed. Unfortunately, a considerable fraction of this decolorization was due to adsorption on the resin surface.

Chemometric alternatives for resolution of classical analytical problems: Spectrophotometric determination of lanthanide mixtures

The simultaneous determination of lanthanide family elements is one of the greatest problems in analytical chemistry, due to the close similarity of their chemical properties. Spectrophotometric methods are generally of limited use, due to the various mutual spectral interferences involved. By using multivariate calibration methods (partial least-squares regression, PLSR), it was possible to obtain a model that adjusts itself perfectly to the values of the mixture concentrations used in the calibration. The model used absorption spectra in the 290-800 nm range for a set of 20 different mixtures of Ce, Pr, Nd and Sm, and made possible the determination of Ce, Pr and Nd concentrations of a commercial rare-earth product, with significantly greater precision than the conventional univariate calibration method. Determination of the Sm concentrations was not possible, since its concentration was below the concentrations used in the model definition.

Remediação de efluentes derivados da indústria de papel e celulose: tratamento biológico e fotocatalítico

The contribution of the industrial activities to the environmental contamination phenomena is evident. Great efforts are dedicated to the establishment of methodologies which permits an adequate treatment of the produced effluents, as a manner of minimizing the environmental impact of these wastes. The methodologies based on photocatalytic processes are very promise alternatives, because permits degradation of a great number of chemical substances of high toxic potential, without the use of other chemicals. The present work is an overview about the principal environmental aspects related with the paper and cellulose industry and the main alternatives employed for the reduction of environmental impact produced for its residues. The principal results of the photocatalytic treatment of this kind of effluents using metallic semiconductors is also showed.

Alternativas quimiométricas para a resolução de problemas analíticos clássicos: determinação espectrofotométrica de misturas de zircônio e háfnio

The determination of zirconium-hafnium mixtures is one of the most critical problem of the analytical chemistry, on account of the close similarity of their chemical properties. The spectrophotometric determination proposed by Yagodin et al. show not many practical applications due to the significant spectral interference on the 200-220 nm region. In this work we propound the use of a multivariate calibration method called partial least squares ( PLS ) for colorimetric determination of these mixtures. By using PLS and 16 calibration mixtures we obtained a model which permits determination of zirconium and hafnium with accuracy of about 1-2% and 10-20%, respectively. Using conventional univariate calibration the inaccuracy of the determination is about 10-25% for zirconium and above 57% for hafnium.

Heterogeneous photocatalysis treatment of Kraft and textile effluents using metallic and polymeric semiconductors (ZnO and polyaniline)

SummaryWhen Kraft E1 and textile effluents are illuminated with UV light in the presence of polyaniline, the color fades gradually until decolorization ratios of over 80% are attained for a single step of irradiation (1 hour). A chemometrics study show very little influence of pH, mass of polyaniline and presence of oxygen on the efficiency of this process. Complementary experiments indicated that the great intensity of preliminary adsorption of chromophores prevent the subsequent photocataytic destruction when UV light is used.