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The content of heavy metals extremely exceeds from the international level due to the anthropogenic activities brought from point and nonpoint sources, soil and water contamination occurs and agricultural products become unhealthy for human consumption. This study aimed to apply modified bentonite for adsorption of cadmium (Cd2+), copper (Cu2+) and nickel (Ni2+) from an aqueous phase. The natural Iranian bentonite was mixed with anionic surfactants, and sodium dodecyl sulfate (SDS) to produce modified bentonite. Batch experiments were performed in two individual and competitive solutions of Cd2+, Cu2+, and Ni2+ (25-600 mg L-1) in the present of Na-B and SDS (10, 20, and 40 Mm). The results demonstrated that SDS modified bentonite (SDS-B) treatments enhanced the sorption capacity of natural adsorbents with increasing pH. The SDS-B in 40 mM is of more adsorption efficiency to adsorb Cd2+, Cu2+ and Ni2+ than are the other treatments. Among common and comprehensive isotherm models, Langmuir was well fitted to evaluate the data obtained from adsorption experiments. This is a novel study to compare the effect of modified bentonites into both single and comparative solution for heavy metal sorption. The maximum Langmuir adsorption capacity of Cd2+, Cu2+ and Ni2+ was 130.7, 94.4, and 83.06 as shown in SDS-B (40 mM) treatment. SDS-B treatments have the greatest affinity for Cd2+, but the Na-B adsorbs Ni2+ more than the other cations. Using SDS-B showed remarkable gain in enhancing the adsorption efficiency compared to the Na-B in both individual and competitive batch experiments. [ABSTRACT FROM AUTHOR]

This study investigated the removal of phosphorus (PO4−3-P) from water samples by SnO2 and WO3 nanoparticles (NPs). The effects of adsorbent dosage, pH, contact time and temperature with an initial concentration of 50 mg L−1 of P were investigated. SEM-EDX, FTIR, XRD, and BET analyses were performed to characterize these nanoparticles. The results indicated that the maximum adsorption capacity of SnO2 and WO3 NPs was 21.5 and 19.0 mg g−1, respectively and occurred at pH = 3. Within 40 min of operation, about 47.2% and 45.2% of P ion were removed from the solutions by SnO2 and WO3 NPs, respectively. The kinetics of P adsorption from solutions was analyzed by fitting the experimental data to the pseudo-first and second-order kinetic models. The result showed that the pseudo-second-order kinetics model provided much better R2 values. In the multi-component solutions, in the presence of Cl−, NO3− and Cr2O72− ions, the adsorption rates decreased to (26.2% and 28.5%), (27.2% and 30.0%), and (48.0% and 33.0%) by SnO2 and WO3 NPs, respectively. Thermodynamic data (ΔG°< 0) fitting showed that the reactions of adsorption of P were spontaneous. In general, the nanoparticles of SnO2 had better efficiency in the removal of phosphorous from water. [ABSTRACT FROM AUTHOR]

Fourteen street-dust samples were collected from Hamedan, western Iran. Street-dust samples received different amounts of heavy-metal pollution. The samples were analyzed for total cadmium (Cd), copper (Cu), lead (Pb), nickel (Ni), and zinc (Zn), and binding forms of heavy metal were determined in five fractions. The results showed Cd was the only metal present appreciably, 25.21% and 25.92%, in the exchangeable and carbonates fractions, respectively, and Cu was the only metal predominantly associated, 31.77%, with organic fraction. Zn, 45.84%, was present mainly in the Fe- Mn oxide fraction, and the residual fraction was the most dominant solid phase pool of Ni and Pb, respectively, with 42.56% and 41.31%. The order of apparent mobility and potential metal bioavailability for these contaminated street-dust samples is Cd > Zn > Cu > Pb > Ni. The riskassessment code results showed very high risk for Cd; medium risk for Cu, Pb, and Zn; and low risk for Ni. [ABSTRACT FROM AUTHOR]

Contamination of soil was investigated in this study from the Tehran Oil refining Co. of Iran. Fifteen soil samples were collected at several points in the Azimabad, 15 km south of Tehran City, Iran. Samples were collected at depths of 0-30 cm. Control sampleswere prepared to determinebackgroundlevels ofsoil contamination with petroleum hydrocarbons for comparison with contaminated sites. Total petroleum hydrocarbon (TPH) and poly-aromatic hydrocarbons (PAH) concentrations varied from 101334.0-101367.1 and 25321.1-25876.6 mg kg-1 respectively. The results elevated levels of TPH and PAH contents when compared with the control sample. Soil acidity (low pH of 5.3-5.9) and low electrical conductivity provided evidence of reduced metabolic activities on the affected site. Microbialgrowthrates for bacteria and fungi expressed as colony forming units were 2.62×109 and 4.14×106CFU/g soil, respectively for the contaminated and 5.76×109 and 6.83×106CFU/g soil, for the control treatments respectively. These drastic changes can have impact on the nutrient cycle and prevents the absorption of nutrients by plant root sand lead to a reduction in yield. [ABSTRACT FROM AUTHOR]

This study aimed to assess the quality of road runoff in heavy traffic and residential areas of Hamedan province, in the western region of Iran. To investigate the effects of salt pollution, 14 runoff samples were collected from streets during the winter and spring of 2009. Streets received different amounts of deicing salt depending on the traffic density. Results showed that deicing salt has major affects on sodium ( Na+), calcium ( Ca2+), magnesium ( Mg2+), chloride ( Cl−), bicarbonate ( [ABSTRACT FROM AUTHOR]