Optimization of Turbidity and COD Removal from Pharmaceutical Wastewater by Electrocoagulation. Isotherm Modeling and Cost Analysis

摘要

The present work was conducted to optimize operating parameters for electrocoagulation treatment of a pharmaceutical effluent. Chemical oxygen demand (COD) and turbidity removals were monitored for each experiment since they are good indicators of wastewater quality The effects of three parameters such as pH (4-10), current density (i=20-80 mA/cm(2)), and time of reaction (t=10-30 min) were evaluated using a response surface methodology (RSM) and in particular a full factorial central composite face-centered (CCF) design. The obtained experimental data were fit to a second-order polynomial equation using multiple regressions and were also analyzed by variance analysis (ANOVA). The contour plots derived from the mathematical models were applied to determine the optimal conditions (pH of 5.31, current density of 46.83 mA/cm(2), and electrolysis time of 17.99 min). Under these conditions, the experimental COD and turbidity removals were found equal to 75.64 and 96.34%, respectively, which were in agreement with the values predicted by the models. The electrocoagulation mechanism was modeled using Freundlich and Dubinin-Radushkevich isotherms. The obtained results showed that the Freundlich isotherm correctly predicted the experimental data. Operating costs included energy and electrode consumption as performed for the process of treatment. It was noted that the general cost varied from 0.1053-2.8289 US$ for current densities ranging from 20-80 mA/cm(2) and electrolysis times from 10-30 min. Under optimal conditions, the general cost was found equal to 0.8113 US$/m(3).