Ali Akbar Safari Sinegani; Omid Noroozi
Abstract
Survival of enteropathogenic bacteria in soil is a key factor to control waterborne diseases. The significance of zeolite nanoparticles in comparison with natural size particles on the survival of Escherichia coli in soil was studied in sterile and unsterile conditions. The experimental mixtures prepared ...
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Survival of enteropathogenic bacteria in soil is a key factor to control waterborne diseases. The significance of zeolite nanoparticles in comparison with natural size particles on the survival of Escherichia coli in soil was studied in sterile and unsterile conditions. The experimental mixtures prepared by adding zeolite and nanozeolite at levels of 0, 5, 15% w/w to a loam textural soil to obtain 100 gr mixtures. Mixtures inoculated by a nalidixic acid resistance Escherichia coli (E.coli NAR) at a rate of 106 cells gr-1 soil. Results showed that in the unsterile soils, adding 5% zeolite had no significant effect on the survival of bacteria in soil and 15% nanozeolite reduced bacteria survival in soil especially at initial days of inoculation (about 3 log-unit). While adding 15% zeolite and 5% nanozeolite had a significantly positive effect on bacteria's time need to reach the detection limit (td). Sterilization of soil mixtures significantly enhanced bacteria survival in all treatments. The highest value of td obtained in sterile soil amended with 15% zeolite (46 days). In sterile mixtures adding nanozeolite caused an increasing in bacteria population at initial days after inoculation (about 1-1.5 log-units). Decreasing in the size of natural zeolite particles to nanoscale had a negative effect on survival of the studied bacterium in unsterile mixtures and E.coli NAR survived more in zeolite amended mixtures. While this negative effect was not observed in sterile soil. These results clearly showed that competition is the main factor that controls enteropathogenic bacteria's survival in soil.
Taher Yousefi; Meisam Torab-Mostaedi; Amir Charkhi; Abolfazl Aghaei
Abstract
An uptake of Cd(II) from aqueous solutions by ion exchange on Iranian natural zeolitic (TOSKA) has been studied. Experiments were carried out using batch method as a function of the initial concentration of metal ions, contact time, and temperature. The adsorbent is characterized using XRF, FTIR, TEM, ...
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An uptake of Cd(II) from aqueous solutions by ion exchange on Iranian natural zeolitic (TOSKA) has been studied. Experiments were carried out using batch method as a function of the initial concentration of metal ions, contact time, and temperature. The adsorbent is characterized using XRF, FTIR, TEM, and XRD. The TEM images showed that the zeolite particle sizes are reduced into the size range of less than 90 nm by means of ball milling. The characterization of sample indicates that the natural zeolite used in this study was classified into clinoptilolite. Equilibrium modelling data were fitted to linear Langmuir and Freundlich models. Thermodynamics parameters such as change in free energy (ΔG◦), enthalpy (ΔH◦) and entropy (ΔS◦) were also calculated. The negative values obtained for ΔG◦ indicated that the sorption of Cd(II) on natural zeolite was spontaneous at all studied concentrations. These results show that natural zeolites hold great potential to remove Cd(II) from industrial wastewater.