Soil Chemistry and Pollution
Samira Alvani; ُSaeid Hojati; Ahmad Landi
Abstract
Introduction Pollution of the environment to heavy metals is one of the major problems of today's world. Following the development of industries, as well as increasing agriculture in response to the growing population, the overuse of chemical fertilizers, mining activities, the production and disposal ...
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Introduction Pollution of the environment to heavy metals is one of the major problems of today's world. Following the development of industries, as well as increasing agriculture in response to the growing population, the overuse of chemical fertilizers, mining activities, the production and disposal of waste waters and sewage sludge, etc., the entry and accumulation of heavy metals in the environment has increased. There are several methods for removing heavy metals from wastewaters. Among the common methods for removal of heavy metals, adsorption, in particular using inexpensive natural adsorbents, due to the ease of implementation and high efficiency is a cost-effective and economical technique. Palygorskite is a fibrous mineral common in clay fractions of soils of arid and semi-arid regions of the world. Although there are several studies applying palygorskite as a suitable mineral for cleaning of wastewaters, however, few studies have been carried out to evaluate the ability of nanosized particles of such clay minerals for removal of heavy metals from the environment. Therefore, this study was conducted to measure the ability of palygorskite nano- and micro-sized particles to adsorb lead and copper from aqueous solutions. Materials and Methods: Kinetic experiments were carried out at 11 different contact times (5, 10, 20, 30, 60, 120, 240, 480, 720, 1440, and 2880 min) using solutions containing 150 mg / l of lead and copper elements at pH=5. Palygorskite used in this study was purchased from Tulsa Co., Spain Then, micron (Results and Discussion The results illustrated that in the so-called samples as nanosized palygorskite, about 50% of the particles in the sample was found smaller than 100 nm in size, and in this case no samples of particle size of 100 nm and smaller were observed in those so-called palygorskite microparticles. The results indicated that by increasing the contact time and reducing the mineral particle sizes from micron to nanoscale, more amounts of lead and copper heavy elements adsorbed onto the mineral. This is due to an increase in the exposure of active sites on the adsorbent surfaces by the pollutant. When the data were fitted with the pseudo first order, pseudo second order and intraparticle diffusion kinetic models, it was revealed that the pseudo second-order kinetic model with a determination coefficient (R2) of 0.99 was the best model describing kinetics of study. Besides, the lower values of the chi-square (ᵡ2) in fit with the pseudo-second-order kinetic model as compared to those in the pseudo first-order model show a greater similarity between the pseudo-second-order kinetic model and the experimental data. The isotherm of Pb and Cu adsorption was also studied using Langmuir and Freundlich adsorption models. It was observed that the data had a better coordination with the Langmuir model with a determination coefficient of 0.99. By increasing the initial concentration of the lead and copper in the solution, their distribution coefficient (Kd) decreases. This suggests that although with increasing initial concentration of lead and copper, their adsorption increased by palygorskite mineral, however, by increasing the initial concentration of heavy metals, the remaining concentration of these elements also increased. The results also illustrated that both micro- and nanoparticles of palygorskite show more affinity to adsorb lean than copper from solutions. Conclusion: In general, it can be concluded from this study that adsorption of lead and copper by palygorskite nanoparticles depends on the contact time and the adsorbent size. Besides, the use of this mineral could be considered as a suitable, feasible and environmentally friendly way to remove lead and copper from aqueous solutions.
Sajedeh Sadinejad; Ali Jafarnejadi; Ali Gholami; Abdolamir Moezzi
Volume 36, Issue 2 , March 2014, , Pages 69-80
Abstract
One of the basic principles for sustainable production is improving the quality of soil with regard to soil fertility and soil nutrients status. This study was conducted to investigate spatial variation of copper and manganese elements in soil farms in the northern part of Khuzestan region (100,000 ha). ...
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One of the basic principles for sustainable production is improving the quality of soil with regard to soil fertility and soil nutrients status. This study was conducted to investigate spatial variation of copper and manganese elements in soil farms in the northern part of Khuzestan region (100,000 ha). Therefore, 95 soil samples were collected from studied regions according to their wheat cultivation area. The data were analyzed to determine spatial variation and interpolation using Kirging technique. The results revealed that the average soil manganese concentration was 6.75 mg/kg in the study regions. Also, more than 75% of studied soils had manganese concentrations less than 8 mg/kg (threshold value), the average of copper concentration was 1.35 mg/kg, and about 90% of soils had desirable copper concentration. According to the results, there were significant correlations between the soil's copper and phosphorus (r= 0.79*), clay (r= 0.78*) and salinity (r= 0.77*) and also between soil's manganese and pH (r=0.83*). The best model for study characteristics was the spherical model. The highest soil manganese concentration was on the northeast, and the highest soil copper was on the west of the study regions. Finally, in some parts of the study area in which manganese and copper levels were less than the threshold value, application of copper and manganese fertilizers can be recommended. It increases the yield and improves the soils and agricultural products quality.