ABSTRACT
The treatment of pharmaceutical industrial wastewaters, containing the antibiotic amoxicillin (218.29â mg L-1), via some advanced oxidation processes (POA), was studied. The H2O2 photolysis process presented the highest percentage of mineralization (97%), after the total reaction time (180â min). However, the photo-Fenton process showed the highest organic carbon removal rate, mineralizing 65% of the initial concentration, in 30â min. Because of this fact, this process was studied in more detail. The initial concentration of ferrous ions (0.03-1.00â mmol L-1) did not affect the performance of the photo-Fenton process, possibly operating using concentrations of below 15â mg L-1 (0.27â mmol L-1), that is the iron content limit for discharging wastewaters established in the Brazilian environmental legislation. Furthermore, experiments were performed according to the composite experimental design technique (Doehlert matrix), analyzing the following variables: (i) the inlet molar flow rate of H2O2 (FH2O2 ) and (ii) the initial concentration of ferrous ions ([Fe2+]). Besides that, the initial mineralization rate and the total organic carbon removal percentages, measured at 5, 10, 15 and 30â min of reaction, were chosen as the response variables. It was observed that FH2O2 was the most important variable in relation to the initial degradation rate. In the optimal conditions (FH2O2 = 3.27â mmol min-1 and [Fe2+] = 0.27â mmol L-1), the photo-Fenton process achieved a percentage of organic carbon removal of 84%, in only 30â min of reaction, presenting an interesting potential for real industrial applications, combined, or not, with conventional technologies (as biological treatments, for example).
Subject(s)
Pharmaceutical Preparations , Water Pollutants, Chemical , Amoxicillin , Anti-Bacterial Agents , Hydrogen Peroxide , Oxidation-Reduction , Waste Disposal, Fluid , WastewaterABSTRACT
A highly concentrated aqueous saline-containing solution of phenol, 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4-dichlorophenol (2,4-DCP) was treated by the photo-Fenton process in a system composed of an annular reactor with a quartz immersion well and a medium-pressure mercury lamp (450 W). The study was conducted under special conditions to minimize the costs of acidification and neutralization, which are usual steps in this type of process. Photochemical reactions were carried out to investigate the influence of some process variables such as the initial concentration of Fe(2+) ([Fe(2+)](0)) from 1.0 up to 2.5 mM, the rate in mmol of H(2)O(2) fed into the system (FH(2)O(2);in) from 3.67 up to 7.33 mmol of H(2)O(2)/min during 120 min of reaction time, and the initial pH (pH(0)) from 3.0 up to 9.0 in the presence and absence of NaCl (60.0 g/L). Although the optimum pH for the photo-Fenton process is about 3.0, this particular system performed well in experimental conditions starting at alkaline and neutral pH. The results obtained here are promising for industrial applications, particularly in view of the high concentration of chloride, a known hydroxyl radical scavenger and the main oxidant present in photo-Fenton processes.
Subject(s)
2,4-Dichlorophenoxyacetic Acid/chemistry , Chlorophenols/chemistry , Herbicides/chemistry , Hydrogen Peroxide/chemistry , Iron/chemistry , Phenol/chemistry , Waste Disposal, Fluid/methods , Catalysis , Ferrous Compounds/chemistry , Hydrogen-Ion Concentration , Oxidation-Reduction , Sodium Chloride/chemistry , Waste Disposal, Fluid/economicsABSTRACT
The photo-Fenton process (Fe(2+)/Fe(3+), H(2)O(2), UV light) is one of the most efficient and advanced oxidation processes for the mineralization of the organic pollutants of industrial effluents and wastewater. The overall rate of the photo-Fenton process is controlled by the rate of the photolytic step that converts Fe(3+) back to Fe(2+). In this paper, the effect of sulfate or chloride ions on the net yield of Fe(2+) during the photolysis of Fe(3+) has been investigated in aqueous solution at pH 3.0 and 1.0 in the absence of hydrogen peroxide. A kinetic model based on the principal reactions that occur in the system fits the data for formation of Fe(2+) satisfactorily. Both experimental data and model prediction show that the availability of Fe(2+) produced by photolysis of Fe(3+) is inhibited much more in the presence of sulfate ion than in the presence of chloride ion as a function of the irradiation time at pH 3.0.
ABSTRACT
The application of the photo-Fenton process for the treatment of wastewaters contaminated with diesel oil was investigated. This particular process has been widely studied for the photochemical degradation of highly toxic organic pollutants. Experiments were performed according to a factorial experimental design at two levels and two variables: H(2)O(2) concentration (5-200 mM) and Fe(2+) concentration (0.01-1 mM). Experimental results demonstrated that the photo-Fenton process is technically feasible for the treatment of wastewaters containing diesel oil constituents, with total mineralization. A combination of factorial experimental design and gradient descent techniques was employed to optimize the amount of the Fenton reagents, resulting in Fe(2+) (0.1 mM) and H(2)O(2) (50 mM). These optimized levels did not exceed the limit for disposal of ferrous ions (0.27 mM) proposed at the local environmental legislation.
Subject(s)
Gasoline/analysis , Hydrogen Peroxide/chemistry , Iron/chemistry , Water Pollutants, Chemical/analysis , Water Purification/methods , Photochemistry , Water Purification/instrumentationABSTRACT
The photo-Fenton process utilizes ferrous ions (Fe2+), hydrogen peroxide (H2O2), and ultraviolet (UV) irradiation as a source of hydroxyl radicals for the oxidation of organic matter present in aqueous effluents. The cost associated with the use of artificial irradiation sources has hindered industrial application of this process. In this work, the applicability of solar radiation for the photodegradation of raw gasoline in water has been studied. The photo-Fenton process was also applied to a real effluent, i.e., oil-field-produced water, and the experimental results demonstrate the feasibility of employing solar irradiation to degrade this complex saturated-hydrocarbon-containing system.
Subject(s)
Gasoline , Solar Energy , Waste Disposal, Fluid/methods , Water Pollutants, Chemical , Chromatography, Gas , Hydrogen Peroxide , Iron , Photolysis , Sodium Chloride , Time Factors , Ultraviolet Rays , Waste Disposal, Fluid/economics , Waste Disposal, Fluid/instrumentationABSTRACT
The application of the photo-Fenton process to the treatment of saline wastewater contaminated with hydrocarbons is investigated. Aqueous saline solutions containing raw gasoline were used as a model oil-field-produced water. The dependence on concentrations of the following reagents has been appropriately evaluated: hydrogen peroxide (100-200 mM), iron ions (0.5-1 mM), and sodium chloride (200-2000 ppm). The reactions were monitored by measurement of the absorption spectra and total organic carbon (TOC). Experimental results demonstrate that the photo-Fenton process is feasible for the treatment of wastewaters containing hydrocarbons, even in the presence of high concentrations of salt. The effect of the salt in this process is described through a series of reactions. A simple feedforward neural network model was found to correlate well the observed data for the degradation process.