Degradation and removal of p-nitroaniline from aqueous solutions using a novel semi-fluid Fe/charcoal micro-electrolysis reactor

p-Nitroaniline (PNA) is a common contaminant in the wastewater of oil refineries, the petrochemical industry and from production of pesticides, dyes and glue. The aim of this research was to determine the extent of degradation and removal of PNA from aqueous solutions by a novel semi-fluid Fe/charcoal reactor, process optimization, determination of the intermediate and final products and the degradation reaction path. The effective factors in the degradation process were contact time, aeration amount, initial PNA concentration, Fe/charcoal ratio, and initial pH of the solution. The intermediate products were determined by GC-MS. The kinetics of the degradation reaction also was determined. PNA removal efficiency in an actual sample from petrochemical industry wastewater was tested under optimal conditions. The maximum removal efficiency under the optimal conditions (pH: 7; contact time 120 min; aeration rate 10 L/min; Fe/charcoal ratio: 2/1; initial concentration of PNA: 10 mg/L) for the synthetic solution and in actual wastewater samples were 95% and 89%, respectively. In addition, the system stability was investigated in ten consecutive cycles of the electrode reuse. The removal efficiency decreased as low as 5%, which indicates the high stability of the system. The degradation process was determined to follow pseudo-first kinetics and the Langmuir-Hinshelwood model. Fe/charcoal micro-electrolysis is a relatively highly efficient system for removing PNA from wastewater and is suggested for this purpose.