Activated carbons application to remove non ionic surfactants drom wastewater produced by an italian metallurgic plant

摘要

The performance of different activated carbons for the removal of nonionicudsurfactants from metallurgic wastewater was assessed through lab scaleudexperiments. Two different matrices were used: a simple one, obtained byuddissolving different amounts of a single nonionic surfactant (Triton X100) inuddistilled water, and a complex matrix, prepared as above but using surfactantsfreeudwastewater from an Italian metallurgic plant as solvent. In this way the mainudoperative parameters that affect the adsorption process in the simple matrix haveudbeen studied avoiding the interference due to the complex matrix; then the resultsudwere utilized to define and optimize the tests carried out on the complex matrix.udThe adsorption equilibrium experimental data were best fitted with a Langmuirudisotherm, allowing defining the contact time and the proper design parameters forudthe adsorption column. The different tests were performed on four differentudactivated carbon types, and the removal efficiency and the treatment cycleudduration for each of the tested carbons were discussed and compared. Theexperimental results showed that the saturation adsorption capacity is notudnotably correlated either with the pH value or with the water matrix, whereas theudslope of the isotherm, defined by the Henry constant, is sensibly higher at strongudacidic or alcaline conditions, with a minimum value at nearly neutral pH.udTherefore, it was concluded that the removal efficiency is maximized when theudoperative pH was in the 2–4-unit value range. The best activated carbon, in termsudof removal efficiency, resulted to be a mineral activated carbon, characterized byudthe highest iodine number, and thus with the largest porosity. Removaludefficiencies were in the 60 to 80% range.