Biomedical subjects

Olga Gimeno

Publications and source records attributed to Olga Gimeno.

8 recordsLinked to original sources

PubMed2005

Phenol and substituted phenols AOPs remediation.

The oxidation of phenol and two substituted species (4-nitrophenol and 4-chlorophenol) has been carried out by means of the O3, UV-vis, O3+UV-vis, TiO2+UV-vis, O(3)+UV-vis+TiO2 and O3+TiO2 systems. From UV-vis experiments, the quantum yield of these organics has been calculated (0.018, 0.005 and 0.017 mol per Einstein for phenol, 4-nitrophenol and 4-chlorophenol, respectively). Broadly speaking, the addition of titania powder results in a slight inhibition of the parent compound degradation rate, although a positive effect is experienced when measuring the chemical oxygen demand (COD) and total organic carbon (TOC) removals. Amongst the technologies investigated, those combining ozone and radiation show the best efficiency in terms of phenols elimination and also COD and TOC decay rates. A simple economy analysis of the processes illustrates how the combinations O3+UV-vis and O3+UV-vis+TiO2 are the most attractive technologies, although some additional considerations have to be taken into account.

Chlorophenols↗

PubMed2004

Stabilized leachates: sequential coagulation-flocculation + chemical oxidation process.

The combined sedimentation-chemical oxidation treatment of medium-stabilized landfill leachates has been investigated. The sequence of stages implemented was: (a) coagulation-flocculation by pH decrease (pH 2) to acidic conditions (COD removal approximately 25% related to COD0 approximately 7500 ppm); (b) coagulation-flocculation by Fe(III) addition (0.01 M) at pH 3.5 (COD removal approximately 40% related to COD of supernatant after step (a); (c) Fenton (Fe(III) = 0.01 M; H2O2 = 1.0 M) oxidation (COD removal approximately 80% related to COD of supernatant after step (a); and (d) coagulation-flocculation of Fenton's effluent at pH 3.5 (COD removal approximately 90% related to COD of supernatant after step (a). The use of Kynch theory allows for the design of clarifiers based on the amount of solids fed. For a general example of 1000 m3 day(-1) of a feeding stream, clarifier area values of 286,111 and 231 m2 were calculated for compacting indices of 3.7, 2.67 and 2.83 corresponding to the first, second and third consecutive sedimentation processes, respectively, (steps (a), (b) and (d)).

Environmental Pollution↗

PubMed2004

Aqueous ozone decomposition onto a Co2O3-alumina supported catalyst.

The aqueous ozone decomposition in the presence of a Co2O3-Alumina catalyst was investigated. Activity and estability assays were conducted by reusing the same catalyst in consecutive runs. The catalyst was shown to significantly increase the ozone abatement rate without loss in activity after five consecutive experiments. The process can be acceptably simulated by a double homogeneous-heterogeneous decomposition mechanism. An increase in the working temperature resulted in an opposite effect by increasing the extension of the homogeneous decomposition and lowering the extension of the heterogeneous decomposition. Similarly, different trends were observed by adding two distinct free radical scavengers (terc-butyl alcohol and carbonates).

Aluminum Oxide↗

PubMed2003

Treatment of brines by combined Fenton's reagent-aerobic biodegradation. II. Process modelling.

Process modelling of the integrated Fenton's reagent-aerobic biodegradation system has been carried out by considering a detailed reaction mechanism for the chemical oxidation step and the generalised Monod equation for the biological treatment. Chemical oxygen demand has been contemplated as a pseudo-component for simulation purposes. The proposed mechanism takes into consideration different features experimentally found. Thus, the inefficient hydrogen peroxide decomposition into oxygen and water, the influence of temperature and other operating variables and the role of oxygen have been considered. The aerobic biodegradation of the effluent after the chemical oxidation has taken place has been well simulated by Monod equation with no inhibitory terms. Dependency on temperature has been correlated by Arrhenius expression.

Bacteria, Aerobic↗

PubMed2003

Optimisation of Fenton's reagent usage as a pre-treatment for fermentation brines.

Pre-treatment of fermentation brines from green olives has been carried out by the Fe(II)/Fe(III)/H(2)O(2) system. Reagent concentration exerted a positive influence on chemical oxygen demand (COD) removal. Hydrogen peroxide uptake showed values in the range 0.3-1.6mol of COD eliminated per mol of H(2)O(2) consumed depending on operating conditions. The optimum working pH was found to be in the interval 2.0-3.5. Reaction temperature increased the COD degradation rate, although similar COD conversion values were obtained after 5h of treatment regardless of the value of this parameter. An analysis of the biodegradability of this type of effluent demonstrated the beneficial effect of the chemical pre-oxidation. According to the experimental results, it is suggested that there is an inhibitory effect of the wastewater due to its COD content and nature rather than attributable to the presence of high amounts of sodium chloride. Biodegradation efficiency increased as temperature was raised up to 30 degrees C. A further increase of this parameter up to 40 degrees C resulted in the death of the microorganisms.

Bacteria, Aerobic↗

PubMed2003

Stabilized leachates: ozone-activated carbon treatment and kinetics.

Ozone has been used as a pre-oxidation step for the treatment of stabilized leachates. Given the refractory nature of this type of effluents, the conversion of some wastewater quality parameters has been moderate after 1 h of ozonation (i.e. 30% chemical oxygen demand (COD) depletion). Ozone uptake was calculated in the interval 1.3-1.5 g of ozone per gram of COD degraded. An optimum dose of ozone has been experienced in terms of biodegradability of the processed effluent (60 min of treatment, 1 x 10(-3) mol L(-1) ozone inlet feeding concentration and 50 L h(-1) gas flow-rate). pH and other typical hydroxyl radical generator systems exerted no influence on the efficiency of the process, suggesting the negligible role played by the indirect route of oxidation (generation of hydroxyl radicals). The ozonated effluent was thereafter treated in a second adsorption stage by using a commercial activated carbon. Removal levels up to 90% of COD in approximately 120 h were experienced for adsorbent dosages of 30 g L(-1). Both steps, the single ozonation and the adsorption stage have been modelled by using different pseudoempirical models.

Carbon↗

PubMed2003

Fenton-like oxidation of landfill leachate.

The treatment of stabilized leachates by means of Fenton's like reagent [Fe(III)-H2O2] has been studied. It has been demonstrated that the oxidation state of the catalyst does not influence the efficacy of the process in terms of chemical oxygen demand depletion profiles. The abrupt increase in temperature experienced in oxidation experiments involves a wastage of hydrogen peroxide diminishing the fraction of this reagent addressed at removing COD. If temperature is kept constant, the hydrogen peroxide uptake is 10 mg of H2O2 consumed per mg of COD abated (from 15 to 30 degrees C). Working temperatures above 30 degrees C does not lead to additional COD conversion, contrarily, the percentage of wasted H2O2 is increased. A rough economic analysis of the process indicates that this treatment can be a suitable alternative to deal with this type of effluents.

Hydrogen Peroxide↗

PubMed2002

Co-oxidation of p-hydroxybenzoic acid and atrazine by the Fenton's like system Fe(III)/H2O2.

The system Fe(III)/H2O2 has been used to oxidise an aqueous solution of p-hydroxybenzoic acid (pHB) in the absence of light. In the process, typical operating variables such as reagent concentration exert a positive influence in the pHB degradation rate. Optimum pH has been found to be around 3. The kinetic study suggests that the mechanism involved in this system differs to some extent from that reported for the classic Fenton's chemistry in pure water. Thus, formation of a complex Fe(III)-pHB seems to be a key step to initiate the oxidising mechanism. Stoichiometric measurements of the H2O2 consumption per mole of pHB degraded indicate a possible reduction of complexed Fe(III). Simultaneous oxidation of pHB (and other similar compounds such as tyrosol (Ty) or p-coumaric acid (pCu)) and atrazine have shown a synergistic effect of the first substance to remove the pesticide.

Atrazine↗