Jesus Beltran-Heredia

Henry's law constant for the ozone-water system

Abstract Ozone absorption in water in the presence of several salts has been studied in an agitated tank. The influence of the operating variables: ionic strength, temperature, pH, gas flow rate, ozone partial pressure and agitation speed, on the dissolved ozone concentration has been investigated. From an ozone balance in the reactor, the liquid phase volumetric mass transfer coefficient and the equilibrium ozone concentration were calculated. Finally, equations for the Henrys law constant as a function of temperature, pH and ionic strength for every salt have been deduced. These equations reproduce the experimental results with deviations less than ±15%. The equations allow us to know the ozone solubility for a given operating condition.

Contribution of free radicals to chlorophenols decomposition by several advanced oxidation processes

The chemical decomposition of aqueous solutions of various chlorophenols (4-chlorophenol (4-CP), 2,4-dichlorophenol (2-DCP), 2,4,6-trichlorophenol (2,4,6-TCP) and 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP)), which are environmental priority pollutants, is studied by means of single oxidants (hydrogen peroxide, UV radiation, Fentons reagent and ozone at pH 2 and 9), and by the Advanced Oxidation Processes (AOPs) constituted by combinations of these oxidants (UV/H2O2 UV/Fentons reagent and O3/UV). For all these reactions the degradation rates are evaluated by determining their first-order rate constants and the half-life times. Ozone is more reactive with higher substituted CPs while OH* radicals react faster with those chlorophenols having lower number of chlorine atoms. The improvement in the decomposition levels reached by the combined processes, due to the generation of the very reactive hydroxyl radicals. in relation to the single oxidants is clearly demonstrated and evaluated by kinetic modeling.

Aerobic degradation of olive mill wastewaters

Abstract The degradation of olive mill wastewater by aerobic microorganisms has been investigated in a batch reactor, by conducting experiments where the initial concentration of organic matter, quantified by the chemical oxygen demand, and the initial biomass were varied. The evolution of the chemical oxygen demand, biomass and the total contents of phenolic and aromatic compounds were followed through each experiment. According to the Contois model, a kinetic expression for the substrate utilization rate is derived, and its biokinetic constants are evaluated. This final predicted equation agrees well with all the experimental data.

Treatment of olive mill wastewaters by ozonation, aerobic degradation and the combination of both treatments

The degradation of the pollutant organic matter present in olive oil mill wastewaters (OMW) is carried out by a single ozonation, a single aerobic degradation, and the combination of two successives steps: an ozonation followed by an aerobic degradation, and an aerobic degradation followed by an ozonation. In both single processes, the removal of this contaminant load is followed by means of global parameters which are directly related to the concentration of organic compounds in those effluents: chemical oxygen demand and total aromatic and phenolic contents. In the ozonation, an approximate kinetic study is performed which leads to the evaluation of the apparent kinetic constants for the aromatic reduction, kA. In the aerobic degradation, the kinetic study is conducted by using the Grau model, which is applied to the experimental data, and leads to the determination of the kinetic parameters of this model, K2 and n. In the combined processes, a higher COD global reduction is obtained by the successive stages, and an improvement in the removal of the organic material during the second treatment of both processes due to the pretreatment conducted is also observed. This enhancement is shown by an increase of the kinetic parameters (K2 and n in the aerobic degradation of the pre-ozonated wastewaters; the apparent constant kA in the ozonation of the wastewaters preliminary fermented aerobically), in relation to the values obtained for them in the single processes carried out at the same operating conditions. © 1999 Society of Chemical Industry

Removal of sodium lauryl sulphate by coagulation/flocculation with Moringa oleifera seed extract.

Among other natural flocculant/coagulant agents, Moringa oleifera seed extract ability to remove an anionic surfactant has been evaluated and it has been found to be very interesting. Sodium lauryl sulphate was removed from aqueous solutions up to 80% through coagulation/flocculation process. pH and temperature were found to be not very important factors in removal efficiency. Freundlich (F), Frumkin-Fowler-Guggenheim (FFG) and Gu-Zhu (GZ) models were used to adjust experimental data in a solid-liquid adsorption hypothesis. Last one resulted to be the most accurate one. Several data fit parameters were determined, as Freundlich order, which was found to be 1.66, Flory-Huggins interaction parameter from FFG model, which was found to be 4.87; and limiting Moringa surfactant adsorption capacity from GZ model, which was found to be 2.13 x 10(-3)mol/g.

Treatment of black-olive wastewaters by ozonation and aerobic biological degradation

Abstract The degradation of the organic pollutants present in black-olive wastewater was carried out by ozonation, aerobic biological degradation, and the combination of two successive steps: an aerobic biological process followed by an ozonation. Contaminant removal was followed by means of global parameters directly related to the concentration of organic compounds in those effluents: chemical oxygen demand and total aromatic and phenolic contents. In the ozonation, an approximate kinetic study was performed to determine the apparent kinetic constants for the COD reduction, k COD , and for the total aromatic reduction, k A . In the aerobic biological degradation, the kinetic study was performed using the Monod model applied to the experimental data. In the combined process, a higher overall reduction in COD and aromatic content was achieved by the successive stages, and there was improved removal of the organic material during the second treatment. This enhancement was reflected in an increase in the apparent kinetic constants in the ozonation of the wastewater that had previously been treated aerobically, relative to the values obtained for the kinetic parameters in the single process experiment which were carried out under the same operating conditions.

Rate constants for the reactions of ozone with chlorophenols in aqueous solutions

The oxidation by ozone of several chlorophenols (CPs): 4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, 2,3,4, 6-tetrachlorophenol, tetracholorocatechol (3,4,5, 6-tetrachloro-2-hydroxy phenol) and 4-chloroguaiacol (4-chloro-2-methoxy phenol), is studied in order to provide values of the overall rate constant for the reaction between ozone and these chlorophenols. Single ozonation experiments of 4-chlorophenol were conducted in an homogeneous system, and ozonation reactions of CP mixtures were performed in a heterogeneous system, leading to the evaluation of the overall ozonation rate constants in acidic aqueous solutions. These second order rate constants increase several order of magnitude with the pH as does the degree of deprotonation of the dissolved compounds (i.e. from 10(3) to 10(9)l/(mols) for different CPs). The specific rate constants for the ozonation of the non-dissociated and dissociated forms of the studied CPs are also determined and reported. The values obtained allow calculation of the overall rate constants and prediction of the reactivities of the several CPs at different operating conditions in the whole range of pH.

Comparison of the degradation of p-hydroxybenzoic acid in aqueous solution by several oxidation processes

A comparative study is made of 12 methods of chemical oxidation applied to degrading p-hydroxybenzoic acid in aqueous solution. The oxidation processes tested were: UV, O3, UV/TiO2, O3/Fe2+, O3/H2O2, O3/UV, UV/H2O2, H2O2/Fe2+, H2O2/Fe2+/O3, UV/H2O2/O3, H2O2/Fe2+/UV and O3/UV/H2O2/Fe2+. The 12 processes were ranked by reactivity. In a kinetic study, the overall kinetic rate constant was split up into three components: direct oxidation by UV irradiation (photolysis), direct oxidation by ozone (ozonation), and oxidation by free radicals (mainly OH*).

Novel tannin-based adsorbent in removing cationic dye (Methylene Blue) from aqueous solution. Kinetics and equilibrium studies.

Natural tannin-based adsorbent has been prepared on the basis of the gelification of Quebracho bark extract. The resulting product, Quebracho Tannin Gel (QTG) was tested as cationic dye adsorbent with Methylene Blue (MB). Kinetics of adsorption process were studied out and a period of 15 days was determined for reaching equilibrium. The influences of pH and temperature were evaluated. As pH or temperature raise q capacity of QTG increases. Theoretical modelization of dye-QTG adsorption was carried out by multiparametric adjustment according to Langmuirs hypothesis. Values of the k(l1), k(l2) and activation energies were calculated.

Removal of Alizarin Violet 3R (anthraquinonic dye) from aqueous solutions by natural coagulants.

In this paper the ability of two natural products in removing dyes has been tested. After a preliminary screening for dye removal capacity, a tannin-based coagulant called ACQUAPOL C-1 and a vegetal protein extract derived from Moringa oleifera seed have been fully studied. The influence of several parameters such as pH, temperature or initial dye concentration (IDC) have been tested and the behavior of both coagulants has been compared. pH results to be an interesting variable and dye removal decreases as pH increases. This effect is higher in ACQUAPOL C-1 than in M. oleifera seed extract. Temperature seems not to be so affecting parameter, while IDC appears to be a very important variable in q(c) capacity, which is higher as IDC increases. Langmuir isotherm model fits very well in both cases of ACQUAPOL C-1 and M. oleifera seed extract dye removal.