Characterization of oil shale kerogen semi-coke and its application to remove chemical pollutants from aqueous solutions

Abstract

An alternative adsorbent from oil shale semi-coke material for removing chemical pollutants from aqueous solutions was investigated. For this purpose, enriched oil shales with different kerogen contents (57, 79 and 90 wt%) were pyrolyzed in nitrogen atmosphere at 600–900 °C at a heating rate of 10 °C/min and a hold time of 60 min. The surface properties of semi-cokes, namely Brunauer-Emmett-Teller (BET) surface area, pore volume and pore size distribution (PSD), were determined by nitrogen adsorption. The studied semi-cokes were found to be micro- and mesoporous. The highest semi-coke BET surface area, 160 m2/g, was obtained at a pyrolysis temperature of 700 °C, which corresponds to 519 m2/g of char, excluding the minerals. This porous carbon material was tested as an adsorbent to remove pesticides and phenolic compounds from aqueous solutions. Three kinds of phenolic compounds (resorcinol, 5-methylresorcinol, 4-nitrophenol) and three kinds of organophosphorus pesticides (dimethoate, parathion, malathion) were tested to study the adsorption on the semi-coke material. Different contact times were tested for the adsorption of the compounds of interest. The results showed that with an adsorbent dosage of 10 mg/mL over 98% of pesticides were removed from the solution within 30 min at an initial concentration of 100 µM (corresponding to 23–33 mg/L depending on the compound). More than 97% of the phenolic compounds were adsorbed from water within six hours at an initial concentration of 10 µM (1.1–1.4 mg/L).

Keywords

• estonian oil shale
• kerogen
• semi-coke
• pyrolysis
• adsorbent.