Comparison study of adsorption and nanofiltration methods for removal of total petroleum hydrocarbons from oil-field wastewater

Abstract

The aim of the current study was to investigate and study adsorption and nanofiltration systems for separation of total petroleum hydrocarbons (TPH) from wastewater generated by an oil refinery in Bushehr, Iran. In the first step (previous study), NaA zeolite nanoparticles (NaA-ZNPs) were synthesized and granulated using a hydrothermal method in which the silica source was extracted from oat bran and then modified by the surfactant hexadecyltrimethylammonium bromide (CTAB). In the second step, polyaniline membranes and nanocomposite membranes were synthesized containing polyaniline as the main polymer and clinoptilolite zeolite as the mineral. The NaA-ZNPs and membranes were characterized by gas chromatography-mass spectroscopy (GC-MS), Fourier transform infrared spectroscopy (FT-IR), scanning electron (SEM), and atomic force microscopy (AFM). In order to evaluate the absorption and nanofiltration process, adsorbents in both batch and continuous process in a fixed-bed column with upward flow were used to remove TPH. Time, pH, and adsorbent dosage were studied in the batch process, and flow rate and column height were evaluated for the continuous process. In the batch and continuous systems, when the parameters were optimized, the highest TPH removal efficiencies were 92.3% and 87.4% respectively. Furthermore, in the nanofiltration process, permeation flux and TPH rejection were 190.96 kg h−1 m−2 and 99.77%. Finally, the removal efficiency for the hybrid absorption and nanofiltration process was 99.83%. In the hybrid system, due to the combination of two absorption and nanofiltration processes, as well as the effects of NaA-ZNPs functioning as adsorbents, membrane deflation was minimized and the efficiency of removing of TPH increased to 99.83%.