Isotopic and hydrochemical evidence for the source and mechanism of groundwater salinization in Kashan Plain aquifer in Iran.

Groundwater salinization and interaction between Playa Lake and regional groundwater were investigated using multi-chemo-isotopic evidences. Forty groundwater and 26 Kashan Playa Lake (KPL) water samples were collected and analyzed for their geochemical compositions. The evolution of hydrochemical facies in Kashan Plain Aquifer (KPA) to KPL is Ca-HCO3 (19%), Mix Ca-Cl (9%), Ca-Cl (17%), and Mix Na-Cl and Na-Cl (55%). Also, the Hydrochemical Facies Evolution Diagram (HFE-D) proposed cation exchange as the main process of salinization in KPA. Based on the binary hydrogeochemical diagrams of (Na+/Cl-)/Cl-, (Ca2+ + Mg2+)/HCO3- + SO42-, and Cl/Br, dissolution of halite and gypsum in the Miocene marlstone in the KPA is the main source of salinity. The δ18O of water in aquifer and playa water samples varies from -10.03 to 7.03‰ (VSMOW) with an average of -6.95‰ and -60.73 to 25.08‰ with average of -45.82‰ for δ2H. Based on the results, the relation between δ18O and δ2H, and δ18O and Br, approves discharge of saline water from KPA to KPL. Likewise, the isotopic composition of δ34SO4, varies from 5.95 to 22.55‰ CDT in KPA, and 5.95 to 9.99 ‰ CDT in KPL. Also, the relations between δ18O-δ34SSO4 and Cl-δ34S were non-linear, indicating that sulfur concentration in KPA and KPL changed due to sulfide oxidation and sulfate reduction in the freshwater and deep brines in the aquifer and mixed during the over-pumping in the KPA. Oxidation of sulfide minerals in the mineralized region in the western part of the aquifer (recharge zone) may have been the source of sulfur leached by seasonal runoff. Water-rock interaction, ion exchange, and hydraulic gradient have been the dominating factors in changing the water chemistry between aquifer and playa leading to saline groundwater discharged to the playa.

Heavy metal pollution status in surface sediments of the Khajeh Kory River, north Iran.

This study aimed at exploring the extent of likely sources of heavy metal pollution in sediments of the Khajeh Kory riverbed in the north of Iran. In order to assess the heavy metal contamination, samples from surface sediments in 10 stations covering the river were collected and analysed to determine heavy metal contents including Cd, Cu, Ni, Pb, Zn, Mn, Co, Al, and Fe. Three guidelines were applied to assess the heavy metal contamination. Compared with the global average values, the calculated enrichment factors indicated high values for Fe, Mn, Cd, Co, and Cu, and very high values for Pb and Zn. The results obtained from principal component analysis revealed that the geogenic and anthropogenic sources were the main causes of the widespread enrichment of heavy metals in the riverbed sediments. The results suggested that the riverbed sediments were contaminated with heavy metals, which contribute to the freshwater toxicity in the ecosystem of the Khajeh Kory River.

Optimization of influential parameters of hydrocarbon recovery from waste oily sludge by solvent extraction using solvent blend.

The influence of experimental factors in solvent extraction for hydrocarbon recovery from oil sludge was investigated using an orthogonal experimental design. The results indicated that temperature, solvent type, solvent blend, solvent to sludge ratio, and treatment duration had significant effects on hydrocarbon recovery. In this investigation, a response surface methodology used to optimize the conditions required to recover hydrocarbons from oily sludge. In addition, the effectiveness of solvent extraction using solvent blends of methyl ethyl ketone (MEK) and xylene for recovery and upgrading of oily sludge has been determined. Oily sludge used here consisted of 63% of its weight petroleum hydrocarbons. Based on the experimental data, a full quadratic model was generated. Optimization of influential parameters was conducted through the fitted model. As determined by the fitted model, the factors such as temperature, mixing time, MEK, and xylene to sludge ratios for optimum oil sludge recovery with solvent extraction method must be fixed at 49.28 °C, 22 min, 6.04 to 1, and 6.4 to 1, respectively. Under the optimum conditions, 64.04% extraction yield achieved using solvent blends of MEK and xylene according to the model. Using the combination of MEK and xylene for recovery of oil sludge, a maximum extraction yield of 61.44% as petroleum hydrocarbons obtained during experiments. Based on the results, combination of MEK and xylene as solvent blend demonstrated significant effect on hydrocarbon recovery in 6 to 1 and higher ratios.

A comparative study on the efficiency of polar and non-polar solvents in oil sludge recovery using solvent extraction.

Oily sludge is a stable emulsion of water in oil, containing solid particles, oily hydrocarbons, and metals with different compositions, which is greatly hazardous to the environment; as a consequence, they must be removed or recovered. Recovery methods are usually preferable because of the possibility of valuable oily hydrocarbons recovery as well as environmental protection. Liquid extraction is one of the most effective methods of oily sludge recovery. In this research, hydrocarbon recoveries from oily sludge using liquid extraction with methyl ethyl ketone (MEK) and toluene as polar and non-polar solvents have been studied and compared to each other. Different parameters will affect the quality of extraction process, among which the temperature, time, and solvent to sludge ratio are the most important ones. Response surface methodology was used as a method of experimental design to find the optimum conditions for obtaining maximum recovery. Then, the sludge recovery efficiencies under the optimum conditions for MEK and toluene were determined by gas chromatography and compared to each other. The results showed 30.41 and 37.24% hydrocarbon recovery for MEK and toluene respectively. Since the major composition of the sludge consisted of non-polar components, therefore, non-polar solvent (MEK) shows better efficiency. The optimum conditions of the studies were 20 °C, 19 min, and 6.4/4.2 for MEK and 55 °C, 17 min, and 3.6/3.6 for toluene.