Subcritical water extraction of trace metals from petroleum source rock

The extraction of trace metals from petroleum source rock by superheated water was investigated and the conditions for maximum yield were determined. The results showed that no significant extraction was attained at 100 °C but the extraction was enhanced at higher temperatures. The optimum temperature for superheated water extraction of the metals from petroleum source rocks was 250 °C. Extraction yields increased with enhanced extraction time. Exhaustive extraction time for all the trace metals determined in this study was attained at 30 min. Comparison of results of leaching these trace metals by superheated water with those of acid digestion revealed that cadmium, chromium, manganese and nickel had better yields with superheated water while vanadium had better yield with acid digestion. The results showed that the temperature and kinetic rates have significant effects on superheated water extraction of metals from petroleum source rocks. The results also revealed that effective leaching of some metals from petroleum source rocks by superheated water can be achieved without any modification except for vanadium.