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Abstract: A study on 4-chlorophenol (4CP) photodegradation has been carried out using UV radiation delivered from three different excimer lamps: XeBr, KrCl and Cl2, with maximum emission wavelengths of 283, 222 and 259nm, respectively. The influence of initial 4-chlorophenol concentration on the photodegradation process was examined with pollutant concentrations ranging from 50 to 500mgL−1, and degradation progress was followed by determining the residual 4-chlorophenol, as well as that of the main photoproducts, hydroquinone (HQ) and benzoquinone (BQ). All excilamps were able to degrade 4CP. XeBr and the KrCl excilamps achieved almost total 4-chlorophenol degradation, with the removal efficiency of the Cl2 excilamp being considerably lower. The KrCl excilamp, in spite of requiring longer exposure times compared with the XeBr, needed a much lower UV dose and, consequently, a lower energy consumption for degradation and, as a result, has been considered the most effective and efficient in 4CP removal. Additionally, and by defining the limit of 4-chlorophenol degradation, a modified pseudo-first order kinetic model was used to fit the kinetics of the 4-chlorophenol degradation process where good agreement between experimental data and those predicted by the model was found. Shielding effects are considered to have an influence on 4-chlorophenol degradation as there is a decrease in the pseudo-first order rate constant with increasing 4-chlorophenol concentrations for the three excilamps. In addition, there is a noticeable decrease in the maximum removal of 4-chlorophenol for the Cl2 excilamp due to the same effect. [Copyright &y& Elsevier]

Abstract: Excilamps are new UV sources with great potential for application in wastewater treatment. In the present work, a KrCl excilamp emitting radiation at 222nm has been used for the photodegradation of 4-chlorophenol within a range of concentrations from 50 to 500mgL−1. The photodegradation process has been shown to form two main photoproduct intermediates, benzoquinone and hydroquinone. Total removal of 4-chlorophenol was shown for all concentrations assayed, and, for both main intermediates, residual concentrations of 20–30% of the initial concentration of 4-chlorophenol remained. Their increasing presence with increasing initial concentrations of 4-chlorophenol had the effect of decreasing the removal efficiency of the photoproducts. In order to simulate the process and scale-up a simplified kinetic model has been developed and validated from the experimental data. [Copyright &y& Elsevier]

Abstract: A diffusion-reaction kinetic model is presented for the kinetic analysis of the removal process of phenolic compounds using hydrogen peroxide and immobilized peroxidase. The good results obtained in the fitting of the experimental data to the model confirm its validity, in the experimental range considered, as well as the one of the extended version of the Dunford mechanism proposed in a previous paper. The phenomenon of enzyme deactivation and/or sequestration by the precipitated olygomers/polymers, which has been widely described in the literature, is here modeled as the growth of a polymeric film over the external surface and inside the pores of the catalytic particles that contain the enzyme, thus determining the appearance of diffusional limitations and an increasing loss of activity. The deactivation phenomena, interpreted and modeled in terms of the effectiveness factor, are included in the kinetic model. To confirm the validity of the model, several series of experiments were carried out in a discontinuous tank reactor. Some of these experimental series were used to obtain the values of the kinetic parameters by numerical calculation and using an error minimization algorithm. Since the model reproduces the behavior of the system for the series of experiments not used for the determination of the parameters, it can be affirmed that the model is suitable for the kinetic analysis of the system under study. [ABSTRACT FROM AUTHOR]

Abstract: The presence of organic toxic solutes in industrial wastewater is a common environmental problem. Aniline is known to be a harmful and persistent pollutant and its presence in wastewater requires treatment before disposal. The performance of reverse osmosis to remove aniline from aqueous solutions is studied in this paper. The study has been carried out in a flat membrane test module using three thin layer composite membranes, two of polyamide, HR98PP and SEPA-MS05, and one of polyether sulphone, DESAL-3B. Recycling of both concentrate and permeate has been carried out in order to keep the feed concentration practically constant and so simulate a continuous process in a quasi-stationary state. The influence of different operational variables (pressure, feed volumetric flow rate, feed concentration and pH) on the performance of the aniline removal process is analyzed. [Copyright &y& Elsevier]

Abstract: Hydrogen peroxide and an immobilized derivative of soybean peroxidase, covalently bound to a glass support, were used in a continuous tank reactor to remove phenol from aqueous solutions. An efficiency of about 80% was attained in phenol removal in the best of the operational conditions assayed. With the aim of scaling up the process to pilot-plant scale, the influence of the main plant operational variables, enzyme and substrate concentrations and flow rate, on the removal efficiency was studied. The continuous reactor was operated under isothermal conditions at the optimal temperature established in the literature for this system. As a first approximation to the industrial application of the process, no buffer solutions were used. Additionally, and to check the validity of a generalized Ping Pong bisubstrate kinetics for the enzymatic reaction, obtained from an expanded version of the Dunford mechanism previously published, and assuming an ideal mixing flow for the continuous tank reactor, a transient design model was developed. By using the intrinsic kinetic parameters obtained in a previous work, where the kinetic model was developed, the reactor model was solved and the theoretical conversion values were calculated. The nearness of the experimental and calculated conversion values confirmed that the proposed kinetic equation and the design model, as well as the intrinsic kinetic parameters previously determined, can be used to predict the behaviour of the reactor under conditions of slow enzyme deactivation, although, for further applications, an improved version of the model deactivation equation is necessary. [Copyright &y& Elsevier]

Abstract: A continuous tank reactor was used to remove 4-chlorophenol from aqueous solutions, using soybean peroxidase and hydrogen peroxide. No buffer solutions and no protective additives were used. The influence of operational variables, both enzyme and substrate concentrations and spatial time, on the removal efficiency of 4-chlorophenol was studied. Assuming a Ping-Pong bisubstrate kinetic for the enzymatic reaction and an ideal mixing flow for the continuous tank reactor, a simplified steady-state model was developed. By using the intrinsic kinetic parameters obtained in a previous paper the reactor model was solved and the theoretical values of the steady-state conversion were calculated. The good approximation between the experimental and calculated values of the steady-state conversion confirmed that the proposed kinetic equation and the design model, as well as the intrinsic kinetic parameters previously determined, can be used to predict the steady-state behaviour of the reactor. [Copyright &y& Elsevier]