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Papers by Jose Casas

Catalysis Today, 2016

The degradation of chlorinated herbicides (MCPA and 2,4-D) and 4-chlorophenol (4-CP) by photocata... more The degradation of chlorinated herbicides (MCPA and 2,4-D) and 4-chlorophenol (4-CP) by photocatalytic oxidation (PCO) and the combination of catalytic hydrodechlorination (HDC) and photocatalysis, at ambient conditions, has been studied. Commercial TiO 2 (P25) and Pd/Al 2 O 3 catalysts were used for PCO and HDC, respectively. MCPA and 2,4-D were transformed upon photo-oxidation to intermediate products and almost total mineralization was achieved. However, in the case of 4-CP, a conversion of only 82% of chloride formation and 87% TOC were obtained. In spite of the fact that the HDC reaction resulted in a total dechlorination of organochlorinated pollutants combined with an important decrease of the effluent ecotoxicity, the percentage of mineralization obtained in the combined process (HDC-PCO) was slightly lower than in the PCO treatment. Thus, the HDC-PCO process is not justified versus a single PCO treatment.

Journal of the Science of Food and Agriculture, 2000

The viscosity of diluted guar gum solutions and the viscosity of xanthan and guar gum mixture sol... more The viscosity of diluted guar gum solutions and the viscosity of xanthan and guar gum mixture solutions have been studied. Guar gum solutions showed pseudoplastic behaviour. Apparent viscosity increased with gum concentration and decreased with the temperature at which viscosity was measured. A maximum in the plot of viscosity versus increasing dissolution temperature was observed at 60°C. This behaviour was related to differences in molecular structure of the polymers solved at different temperatures. Mixtures of xanthan and guar gum showed a higher combined viscosity than that occurring in each separate gum. This synergistic interaction was affected by the gum ratio in the mixture and dissolution temperature of both gums. The effect of polysaccharide concentration (1.0, 1.5 and 2.0 kg m À3), xanthan/guar gum ratio (1/5, 4/2, 3/3, 4/2 and 5/1) and dissolution temperature (25, 40, 60 and 80°C for both gums) on the viscosity of solutions of mixtures were studied. The highest viscosities were observed when 2.0 kg m À3 gum concentration was used together with a ratio of xanthan/ guar gum of 3/3 (w/w) and dissolution temperature of 40 and 80°C for xanthan and guar gum, respectively.

Journal of the Taiwan Institute of Chemical Engineers, 2018

Response surface methodology based on Box-Behnken design (BBD) was successfully applied for the o... more Response surface methodology based on Box-Behnken design (BBD) was successfully applied for the optimization of the UV-LED/FeTiO 3 activated persulfate (PS) process. Disperse Blue 3 (DB3) azo dye oxidation was carried out in a quartz jacketed stirred batch reactor using 405 nm UV at 10 W/m −2 as radiation source. The effects of temperature, catalyst concentration and persulfate dose upon the total organic carbon (TOC) removal were investigated. Optimum operating conditions were found to be: ilmenite: 320 mg/L −1 , PS: 1.56 g/L −1 and 67 °C. Under these conditions, 96% mineralization was achieved. Ecotoxicity of the final effluent was evaluated using Aliivibrio fischeri bacteria, finding a negligible toxicity.

Journal of Chemical Technology & Biotechnology, 2018

BACKGROUD: In the current study, two-step persulfate and Fenton oxidation has been investigated f... more BACKGROUD: In the current study, two-step persulfate and Fenton oxidation has been investigated for the mineralization of naphthenic acids at 80 o C and initial pH ≈ 8. This pH evolves during the persulfate oxidation step towards the optimum for Fenton oxidation (≈ 3). The effects of persulfate and H 2 O 2 doses, iron concentration, duration of the persulfate oxidation step and operating temperature have been assessed. RESULTS: The combined treatment allowed up to ≈ 80% mineralization of cyclohexanoic acid using fairly low relative amounts of reagents (20 and 30% of the stoichiometric for persulfate and H 2 O 2 , respectively). For mineralization of cyclohexanoic acid, 115 and 87 kJ mol-1 were obtained as representative values of the apparent activation energy for the persulfate and Fenton oxidation steps, respectively. The system was also successfully tested with other naphthenic acids, including cyclohexanebutyric acid, 2-naphthoic acid and 1,2,3,4-tetrahydro-2-naphthoic acid. Treatment of the naphthenic acids tested by this system gave rise to easily biodegradable This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as

Analysis of the deactivation of Pd, Pt and Rh on activated carbon catalysts in the hydrodechlorination of the MCPA herbicide

Applied Catalysis B: Environmental, 2016

Abstract The deactivation of a palladium on activated carbon (Pd/AC) catalyst in the hydrodechlor... more Abstract The deactivation of a palladium on activated carbon (Pd/AC) catalyst in the hydrodechlorination (HDC) of the organochlorinated herbicide 4-chloro-2-methylphenoxyacetic acid (MCPA) in water under ambient-like conditions has been studied. The loss of activity is attributed to the accumulation of organic species involved in the reaction on the catalyst surface. The analysis of the fresh and used catalysts indicated the possibility of regeneration by thermal or washing (water, NaOH solutions) treatments. Bimetallic catalysts, Pd-Rh/AC and Pd-Pt/AC, showed lower activity than the Pd/AC one but higher stability (slower deactivation). A Pd catalyst supported on an activated carbon modified upon oxidation (Pd/AC OX ) exhibited higher activity and stability which can be due to the high concentration of surface oxygen groups that reduced the uptake of fouling species.

Study of the deactivation of a Pd/AC catalyst in the hydrodechlorination of MCPA

Separation and Purification Technology, 2015

The production and application of ionic liquids (ILs) is often associated with the formation of a... more The production and application of ionic liquids (ILs) is often associated with the formation of aqueous effluents. Due to the well-known toxicity and poor biodegradability of those compounds, effective treatments for their removal from aqueous solutions are required. In this work, the Fenton oxidation methodology under optimum operating conditions (50 mg L-1 Fe 3+ , stoichiometric dose of H 2 O 2 , 70 ºC and pH 0 =3) was investigated in eleven different ILs, based in the imidazolium, phosphonium, quaternary ammonium, pyridinium and cholinium families, conjugated with various inorganic and organic anions such as chloride, cyanoborate, cyanamide, thiocyanate, dimethylphosphate and tosylate. The efficacy of the process was evaluated by the analysis of the chemical oxygen demand (COD), total organic carbon (TOC), the acids formed by ILs oxidation and the toxicity of the non-treated and treated aqueous effluents towards the Vibrio fischeri bacteria. It was possible to identify the main compounds produced upon Fenton oxidation in the final aqueous effluents (acetic, oxalic and formic acids) and the results seem to suggest that the Fenton oxidation is a good degradation methodology for most of the ILs tested, achieving TOC conversions in the range of 40-80% and 30-40% for aromatic and aliphatic ILs, respectively. Furthermore, non-toxic effluents were obtained at the end of the treatment for all the ILs investigated with the exception of the cyano-based ones due to the release of highly toxic cyanide species to the aqueous medium.

Tesis doctoral inédita. Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Quí... more Tesis doctoral inédita. Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química Física Aplicada, Sección de Ingeniería Química . Fecha de lectura: 17-07-2009 Bibliogr.: p.275-315

Water treatment by catalytic hydrodechlorination for the elimination of 4-chlorophenol

h i g h l i g h t s Au/AC is an active and efficient catalyst for CWPO of phenol. The Au/AC catal... more h i g h l i g h t s Au/AC is an active and efficient catalyst for CWPO of phenol. The Au/AC catalyst provided a good performance within a wide pH range (from acidic to neutral). The activity of Au/AC can be recovered by a thermal treatment at 200°C in air. A kinetic model including catalyst deactivation has been developed.

Oxidation of cosmetic wastewaters with H2O2 using a Fe/γ-Al2O3 catalyst

Water Science and Technology, 2010

A catalyst based on Fe supported on γ-Al2O3 has been prepared and tested for catalytic wet peroxi... more A catalyst based on Fe supported on γ-Al2O3 has been prepared and tested for catalytic wet peroxide oxidation (CWPO) of cosmetic wastewaters. The influence of the main operating conditions (space-time, temperature, and H2O2 dose) have been investigated. Working with this self-made Fe/γ-Al2O3 catalyst at 85°C, with a space-time of 9.4 kgcat h/kgCOD and a dose of H2O2, corresponding to 0.5 times the theoretical stoichiometric H2O2/COD ratio, a substantial COD reduction (around 80%) has been reached with a complete consumption of H2O2. The locally allowable limit of COD for industrial wastewaters discharge to the municipal sewer system can be achieved at lower temperature and space-time. The catalyst showed a high stability in 100 h time on stream tests, where COD and TOC reductions around 82 and 60%, respectively, were maintained working at 85°C and 9.4 kgcat h/kgCOD space-time. Fe leaching from the catalyst upon that time on stream was lower than 3% of the initial load.

Journal of Hazardous Materials, 2007

The removal of organic matter (TOC and COD) from a cosmetic wastewater by Fenton oxidation treatm... more The removal of organic matter (TOC and COD) from a cosmetic wastewater by Fenton oxidation treatment has been evaluated. The operating conditions (temperature as well as ferrous ion and hydrogen peroxide dosage) have been optimized. Working at an initial pH equal to 3.0, a Fe 2+ concentration of 200 mg/L and a H 2 O 2 concentration to COD initial weight ratio corresponding to the theoretical stoichiometric value (2.12), a TOC conversion higher than 45% at 25 • C and 60% at 50 • C was achieved. Application of the Fenton oxidation process allows to reach the COD regional limit for industrial wastewaters discharges to the municipal sewer system. A simple kinetic analysis based on TOC was carried out. A second-order equation describes well the overall kinetics of the process within a wide TOC conversion range covering up to the 80-90% of the maximum achievable conversion.

Highly stable Fe/γ-Al2O3 catalyst for catalytic wet peroxide oxidation

Journal of Chemical Technology & Biotechnology, 2010

ABSTRACT BACKGROUND: A highly stable Fe/γ-Al2O3 catalyst for catalytic wet peroxide oxidation has... more ABSTRACT BACKGROUND: A highly stable Fe/γ-Al2O3 catalyst for catalytic wet peroxide oxidation has been studied using phenol as target pollutant. The catalyst was prepared by incipient wetness impregnation of γ-Al2O3 with an aqueous solution of Fe(NO3)3· 9H2O. The influence of pH, temperature, catalyst and H2O2 doses, as well as the initial phenol concentration has been analyzed. RESULTS: The reaction temperature and initial pH significantly affect both phenol conversion and total organic carbon removal. Working at 50 °C, an initial pH of 3, 100 mg L−1 of phenol, a dose of H2O2 corresponding to the stoichiometric amount and 1250 mg L−1 of catalyst, complete phenol conversion and a total organic carbon removal efficiency close to 80% were achieved. When the initial phenol concentration was increased to 1500 mg L−1, a decreased efficiency in total organic carbon removal was observed with increased leaching of iron that can be related to a higher concentration of oxalic acid, as by-product from catalytic wet peroxide oxidation of phenol. CONCLUSION: A laboratory synthesized γ-Al2O3 supported Fe has shown potential application in catalytic wet peroxide oxidation of phenolic wastewaters. The catalyst showed remarkable stability in long-term continuous experiments with limited Fe leaching, < 3% of the initial loading. Copyright

Journal of Catalysis, 2012

Unsupported Pd nanoparticles of controlled size were tested as catalyst in liquid-phase hydrodech... more Unsupported Pd nanoparticles of controlled size were tested as catalyst in liquid-phase hydrodechlorination (303-323 K, 1 atm) using 4-chlorophenol (4-CP) as target compound. The Pd nanoparticles were synthesized by chemical reduction, using ethanol and methanol as reducing agents and poly(N-vinyl-2pyrrolidone) (PVP) as capping agent. The size of the nanoparticles and the Pd n+ /Pd 0 ratio decreased with increasing alcohol concentration and PVP/Pd ratio, both being lower for ethanol medium. High 4-CP conversion values (80-100%) were achieved at low Pd concentration (2.45 Â 10 À3 g/ L). Phenol was the only reaction by-product detected in contrast to the previous results with supported Pd catalysts, where the active phase-support interaction in 4-CP HDC led to obtain also cyclohexanone and cyclohexanol as by-products in equivalent experimental conditions. The smaller nanoparticles showed higher activity due to the higher available surface (m 2 /g cat). Thus, the smaller nanoparticles synthesized in ethanol medium ranged between 2.7 and 2.8 nm and yielded activity values between 16.7 and 39.1 mmol/g cat min, whereas the smaller particles obtained in methanol medium were in the 3.1-4.2 nm range and exhibited activity values of 20.1-25.7 mmol/g cat min. However, the large nanoparticles exhibited higher activity per unit of catalyst surface, for example, 0.34-0.43 mmol/min m 2 in the case of those synthesized in methanol medium. On the other hand, higher activity was observed for the nanoparticles synthesized in methanol medium when equivalent nanoparticle size was compared. Activation energy values around 100 kJ/mol were obtained for Pd nanoparticles of different characteristics, significantly higher than the value reported for supported Pd catalysts.

Modeling the Influence of pH, Temperature and Culture Medium Composition on the Kinetics of Growth and Cysteine Proteinase Production by Micrococcus sp. INIA 528 in Batch Culture

Food Science and Technology International, 2001

Kinetics of biomass and cysteine proteinase formation during growth of Micrococcussp. INIA 528 in... more Kinetics of biomass and cysteine proteinase formation during growth of Micrococcussp. INIA 528 in batch cultivation were studied. Modeling of cultivation data was carried out using an unstructured model. The logistic equation was found to be adequate to describe microbial growth. Production of cysteine proteinase was described by means of an equation including biomass and substrate concentrations. An overall model based on an equation of substrate consumption dependent on biomass formation and proteinase production was postulated. The kinetic parameters (specific growth rate, maximum biomass, proteinase production rate and proteinase formation yield) were obtained taking into account the influence of pH (6.0–8.0), temperature (28–41 ºC) and the addition of different supplements to the basal culture medium [yeast extract, MgSO 4,glucose, K2HPO4 and (NH4)2SO4]. Kinetic parameters were calculated by fitting experimental data by a nonlinear technique using the algorithm of Marquardt coupled to a fourth-order Runge-Kutta subroutine.

Chemical Engineering Journal, 2010

The hydrodechlorination (HDC) of diuron with hydrogen in aqueous phase was studied in a trickle b... more The hydrodechlorination (HDC) of diuron with hydrogen in aqueous phase was studied in a trickle bed reactor using different Pd, Cu and Ni catalysts supported on activated carbon. The reactor was fed with a diuron aqueous solution (2-30 mg/L) and a H 2 /N 2 (1:1) gas stream. Wide ranges of temperature (35-100 • C) and space-time (64.8-647.5 kg cat h/mol) were studied at a pressure of 1.4 bar. HDC of diuron with Pd on activated carbon (Pd/AC) catalyst with 0.5 wt.% Pd can be conducted successfully at 50 • C, reaching conversion values above 95%. The porous structure of the catalysts showed a significant effect on their activity. A nearly complete removal of diuron was achieved with the 0.5 wt.% Pd catalyst of high external (or non-microporous) area, whereas conversion values of around 70% were obtained with the highly microporous catalyst. The resulting effluents showed lower ecotoxicity values than the inlet diuron solution, thus indicating the evolution to less toxic species. Though the Pd catalysts showed a higher activity, the Cu and Ni ones also led to high conversions well above 80% at 2.5 wt.% metal load. Nevertheless, opposite to the Pd catalysts, a significant metal leaching was observed from the Ni and Cu ones, which affected negatively to the ecotoxicity of the final effluents, showing higher values than for the own initial diuron solution. To improve the anchorage of the active phase to the support, activated carbon was subjected to an oxidative treatment with HNO 3. A significant decrease of leaching was observed, leading to ecotoxicity values comparable to those obtained with the Pd catalysts.

Water Research, 2009

This work investigates the Fenton oxidation of phenol in a semicontinuous reactor where the overa... more This work investigates the Fenton oxidation of phenol in a semicontinuous reactor where the overall amount of H 2 O 2 is distributed as a continuous feed upon the reaction time. The experiments were carried out at 25 C and atmospheric pressure, with 100 mg/L initial phenol concentration and iron dosages from 1 to 100 mg/L. H 2 O 2 aqueous solution was continuously fed during 4 h reaction time up to an overall dose varying within the range of 500-5000 mg/L. The results in terms of evolution of phenol, H 2 O 2 and intermediates, as well as TOC abatement were compared with those obtained in conventional batch operation. It was found that the oxidation rates for phenol and intermediates were lower when adding the H 2 O 2 continuously. However, a higher abatement of TOC was reached at the end of the 4-h reaction time, in spite of a similar overall H 2 O 2 consumption. This is the result of a more efficient OH generation throughout the semicontinuous process, favouring the reaction with the organic species and reducing the occurrence of competitive scavenging reactions involving Fe 2þ , H 2 O 2 and OH. Two kinetic models were proposed, one for describing the evolution of phenol, aromatics and H 2 O 2 and the other for TOC. The influence of the operating conditions on the kinetic constants was also studied, looking for the optimal conditions in terms of both, environmental and economic points of view.

Journal of Chemical Technology & Biotechnology, 2009

BACKGROUND: Lactobacillus reuteri is unable to grow on glycerol as sole carbon and energy source ... more BACKGROUND: Lactobacillus reuteri is unable to grow on glycerol as sole carbon and energy source hence, glycerol is used as an alternative hydrogen acceptor during growth on available carbohydrates. Thus, glycerol is converted to reuterin and 1,3-propanediol (1,3-PDL), both products with interesting industrial applications. These compounds are commonly produced by using resting cells in two-step fermentation processes. RESULTS: The glycerol/glucose cofermentation by L. reuteri yields reuterin and 1,3-PDL at a glycerol concentration higher than 100 mmol L −1. An increase of glycerol concentration from 200 to 400 mmol L −1 showed no additional stimulatory effect on ethanol and acetate production but consistently reduced the lactate concentration. It was also found that reuterin concentration reached a maximum value and subsequently decreased due to its conversion to 1,3-PDL. An unstructured kinetic model was proposed to describe simultaneously microbial growth, substrates consumption and products formation. A multi-response nonlinear regression analysis based on Marquardt algorithm combined with a Runge-Kutta integration method was used to obtain the values of the fitting parameters. CONCLUSIONS: The optimum concentration of glycerol for maximum reuterin and 1,3-PDL production was 200 mmol L −1. The complete process was satisfactorily described by the kinetic model proposed.

Apparent yield stress in xanthan gum solutions at low concentrations

... Permissions & Reprints. Apparent yield stress in xanthan gum solutions at low concentrati... more ... Permissions & Reprints. Apparent yield stress in xanthan gum solutions at low concentrations. F. García-Ochoa and JA Casas. ... At these concentrations, no direct method of yield stress measurement is available. Therefore, an indirect method fitting to a Carson model was used. ...