Search

Environmental pollution is a serious problem in many parts of the world, especially in developing countries such as Iran. This study was conducted to investigate chemical pollution by selected heavy metals in the southern cities of Hamadan province, west of Iran including Malayer, Toyserkan, and Nahavand. A total of 90 soil samples were collected from a depth of 0 to 30 cm of agricultural lands. The state of soil pollution was analyzed using geochemical indicators, pollution coefficient, pollution level, and potential ecological risk indices. The highest concentration of arsenic and cadmium in the soil of city of Toyserkan with an average of 19.46 and 0.25 mg kg-1 respectively, and the highest concentration of iron, cobalt, chromium, and antimony in the soil of city of Malayer with an average of 4.36, 20.8, 114.67 and 4.62 mg kg-1 respectively, and the highest concentrations of manganese, copper, and nickel in the soil of city of Nahavand were 268.95, 38.58, and 81.83 mg kg-1, respectively. The results showed that there was a significant difference between the average concentrations of the measured metals in the three cities. In all the studied cities, Mueller's geochemical index was in the non-polluted category, the pollution coefficient was in the low to medium pollution category, the pollution index was in the very low to high pollution category, and the environmental risk index for metals was in the low to very high environmental risk category. Investigation of pollution indicators showed that the soils of the studied areas are about to be polluted with heavy metals. Therefore, it is necessary to consider environmental aspects to reduce and prevent irreparable damage to the soil and the environmental cycle in the long run. [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]

Experimental studies on the retention of cadmium (Cd2+), copper (Cu2+), nickel (Ni2+), and lead (Pb2+) by bentonite samples from Iran were conducted using single- and multiple-component solutions. Based on the sorption capacity of bentonite the following order was obtained for single- and multiple-component solutions: Pb2+ > Cd2+ > Ni2+ > Cu2+. The maximum adsorption capacities of bentonite with metals in single- and multiple-component solutions were 29.5%, 22.5%, 19.2%, and 17.1% and 13.5%, 13.4%, 12.1%, and 9.1% for Pb2+, Cd2+, Ni2+, and Cu2+, respectively. Desorption isotherms of Cd2+, Cu2+, Ni2+, and Pb2+deviated significantly from the sorption isotherms, thereby indicating irreversible or very slowly reversible sorption. Finally, soil solution saturation indices and metal speciation were assessed using the Visual MINTEQ 2.6 program and the probability of mineral precipitation was supported by scanning electron microscopy. [ABSTRACT FROM AUTHOR]