parameters for photocatalytic degradation from Chromium hexavalent to Chromium trivalent in a solar parabolic cylindrical from tanning

Published: 26 September 2023| Version 1 | DOI: 10.17632/7wdjjkwbvs.1
Maria Elizabeth Bejarano Meza, Carlos Herrera


It is possible to demonstrate the photocatalytic degradation of Cr+6 to Cr+3 in simulated liquid effluents and tanneries using a parabolic solar concentrator capturing solar radiation with a radiation intensity of 875 W/m 2. The effluent samples received from the tanneries that were subsequently analyzed with respect to the concentrations of Cr+6 and Total Cr were carried out in the outlet well; based on the results, a sample was prepared that served as a simulation. From the results, the Total Cr is approximately 819.245 mg/L and According to the legal framework, the maximum permissible limit of effluents for sewage from tannery activities. The independent variables of the simulated liquid effluent sample were pH, temperature (T), flow (Q), hexavalent chrome concentration and dependent variables were the efficiency of the results, solar radiation and titanium dioxide concentration [TiO2]. The optimum processing values were: pH= 3.75; Q= 8.2; T= 30; [TiO2]= 30g. The results of the simulated samples were decreasing from 0.183 mg/L to the values of the maximum permissible limits (MPL) of 0.4 mg/l. In the results carried out before the photocatalytic treatment of the actual tannery sample from the Rio Seco Industrial Park, 326.95 mg/L was obtained, the concentration of hexavalent chromium was 173.28 mg/L. After the photocatalytic treatment, 58.85 mg/L and 25.89 mg/L were obtained respectively, with a reduction of the efficiency from 3 to 1.


Steps to reproduce

To carry out the experimental tests, a 2k + 2 experimental design was applied where k is the number of variables, in this case three, that is, the number of experiments was eleven, the sample to be experimented was a solution of Chromic Acid with concentrations known in water and in the presence of the photocatalyst (TiO2), additionally some tests were carried out with samples of real tannery effluents, to verify the effectiveness of the process. The method used is photocatalytic degradation for a sample of high concentration of Cr+6 simulated from a tanning company, 11 tests were carried out and subsequently verified with a real sample of the effluent. The cylindrical surface of the reactor was made up of aluminum and iron plates that allowed the UV light to be concentrated so that it could hit the pipe that passes through the focus of the parabola and thus have a good level of efficiency. A small storage tank for prepared solutions (2000 ml capacity) was implemented in the solar parabolic cylindrical reactor, with its respective stopcocks attached to PVC and glass pipes; also with an electromagnetic pump to generate pressure on the prepared solution which gives rise to the recirculation and flow of the experimental solution. So that the temperature of the solution was maintained between 40 ± 20 o C, the Water Bath (Lab line Model 18050-1) coupled with a 0.6 mm diameter copper coil and a Thermometer (Giardino Italy) was added. The light source used in the demonstration was UV energy from the sun.


Universidad Catolica de Santa Maria de Arequipa


Industrial Water Treatment