Oil removing properties of exfoliated graphite in actual produced water treatment

Removal of oil from actual produced water (composed of mainly oil and water emulsion) by exfoliated graphite (EG) was investigated. Laboratory scale sorption columns of EG could reduce the oil concentration in produced water from 278 and 66 mg/L to 1.2 mg/L, and undetectable, respectively. A separate experiment with TOC (total organic carbon) demonstrated that TOC decreased from 566 mg/L in the feed solution to 1.5 mg/L in the effluent. Both results (oil densitometer and TOC) showed excellent ability of EG for oil removal from produced water. SEM and FT-IR observations confirmed the deposition of oily material on the surface of EG during the water treatment process. TG-DTA of oil-sorbed EG showed a gradual weight decrease in the temperature range between 100-600 °C, being considered to be the decomposition of sorbed oil. Raman spectroscopy and XRD measurements of EG samples, before and after the treatment, indicated no structural change of EG. Molecular dynamics simulations revealed that octadecane molecules are selectively adsorbed on the EG surface. Effect of isomer type of octadecane molecules on the sorption energy was also discussed.