Investigation into the Use of Waste Polystyrene as an Adsorbent for Phenolic Wastewater in Oil Refineries

Waste polystyrene is a burden for the economy, especially when it spreads in environment due to incorrect waste management. In addition, there are toxic pollutants which should not end up in the natural environment. A good way to tackle these problems is to consider recycling polystyrene, through chemical transformation, into an adsorbent for pollutants. This study considers waste polystyrene (PS) and the materials synthetized from it as adsorbents for removal of the pollutant phenol. Dichloroethane polystyrene (DCEPS) and tetrachloromethane polystyrene (TCMPS) were synthesized in the laboratory by crosslinking polystyrene with dichloroethane and tetrachloromethane, using a Friedel–Crafts reaction. The materials were characterized by FTIR to observe the structural modifications induced by crosslinking. Then, the materials were compared for their adsorption capacity at 300 K. The experimental data proved that, for an initial concentration of phenol in water of 517 mg/L, the adsorption capacity is moderate and increases in the following order: PS (13.4 mg phenol/g) < TCMPS (15.7 mg phenol/g) < DCEPS (19.1 mg phenol/g). The adsorption isotherms at 300 K were determined for a large range of concentrations, and the parameters of Freundlich and Langmuir models were calculated, concluding that the Langmuir model fits better. The kinetics were studied and are represented by a pseudo-first order equation, confirmed by high coefficients of determination for all three materials. The adsorption of phenol from an industrial wastewater flux was performed in continuous flow over a laboratory column. PS and DCEPS were tested, with good results. For example, 1.595 L water containing 22 mg phenol/L was adsorbed on 3.76 g DCEPS; the bed capacity in equilibrium with the wastewater is 10 mg/g adsorbent, the removal efficiency was 95% for a treated volume of 1.595 mL, the breakthrough time was 240 min, and the exhaustion time was 270 min. The novelty of the work consists in demonstrating the possibility of applying polystyrene-based materials as adsorbents for the treatment of phenolic wastewater proceeding from oil refineries.