Enormous research work and feasibility studies have been carried out on the Jordanian OS. This indigenous natural fossil fuel remains without utilization. Huge OS reserves are reported to cover large area of the country [1]. The most studied OS in Jordan is that located in central part which has favorable mining conditions [2]. Jordanian OS is kerogen-rich bituminous limestone of the Muwaqqar Chalk–Marl Formation formed within anoxic environment during the Maastrichtian and Paleocene times [3] [4]. Ke- rogen in OS yields petroleum-like hydrocarbons via destructive distillation by heat at about 500 ̊C [5].
Oil shale development in Jordan requires complex and expensive facilities. Serious economic, environmental, and social implications for Jordan and its people are ex- pected [6]. Among the most important utilization methods of OS are retorting and di- rect burning. The OS ash produced via such methods resulted in significant environ- mental problems. One major environmental problem is the heavy metal release [5]. Oil shale ash management is a wide field and the disposal of OS ash is costly, therefore, re- search is focusing on the benefit from OS ash in wide range of applications such as as- phalt pavement construction and concrete industry. An example on the use of Jorda- nian oil shale ash in Portland cement concrete is that study reported by Smadi and Haddad [7]. Atmospheric emissions of CO2 produced from the oil shale combustion processes are considered as a serious problem [8]. The OS ash is found to be very effi- cient in removing most of Pb2+ ions from influent solutions [5].
Heavy metals found in OS ash could be released to the surrounding environment in- cluding surface and groundwater recourses [9]-[12]. Leachability of these heavy metals is closely related to the phases to which they are associated in addition to pH of the leaching environment [13]. Al-Harahsheh et al. [14] studied the leachability of heavy metals and major anions from Jordanian El-Lajjun spent oil shale after combustion and they reported that the level of heavy metals increases as the temperature of the ashing process increases. Based on their study, no significant metal release from the ashed OS has reported. Compared with the EPA limits for drinking water, El-Lajjun OS ash has low concentrations of trace elements [14]. The OS in the southern part of Jordan has not been studied from the ashing and leachability point of view. It is the aim of this re- search paper to investigate the ashing of OS form Isfir Al-Mahata subsurface OS and to study its leachability. The effect of some parameters such as particle size, mixing time, temperature and pH on OS ash leachability is considered.