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Contamination of water and soil with heavy metals poses serious risks and threats to human health and the environment, and therefore finding an effective solution to remove these metals is very necessary. In this research, magnetic nanoparticles MnFe₂O₄ @ SiO₂ functionalized with N-phosphonomethyl aminodiacetic acid with core-shell structure were synthesized. These nanoparticles were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, (TGA) thermal gravimetric analysis, transmission electron microscope (TEM), and (VSM) vibration sample magnetometer. The performance of this synthetic nanoadsorbent for removing Cr (VI), Cu (II) ions from aqueous solutions was evaluated by various parameters such as adsorbent amount, contact time effect on adsorption rate and pH effect. The results show that the adsorption efficiency increases with raising pH (2.5-5) and the best adsorbent performance in the adsorption process of Cr ((VI) and Cu (II) ions at pH 7 was observed. The amount of R in the Freundlich adsorption diagram of copper ion is higher than the Langmuir isotherm. As a result, the adsorption of copper ions on the adsorbent follows the Freundlich adsorption equation. In addition, the amount of R in the Freundlich adsorption diagram for chromium ion is higher than the Langmuir isotherm. Therefore, the absorption of chromium ions on the adsorbent follows the Freundlich adsorption equation. In conclusion, a high n value indicates a favorable and effective absorption in the Freundlich equation. The adsorption data were analyzed by the Langmuir and Freundlich isotherm model. In addition, the recyclability and reuse of the adsorbent was investigated. The results show that no significant reduction in adsorbent activity is observed.
 

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One of the main challenges facing the Agriculture Bank of Iran regarding lending loans is the high probability of default by farmers. Several factors could be involved in this issue and should be considered in order to control and reduce the risk in the failure of repayment. This study aimed to examine the factors affecting the repayment performance of agricultural loans in the city of Maragheh in East Azarbaijan Province of Iran. Required data were obtained from a sample of 779 individual farmers who had previously received loans from Agricultural Bank during the period 2004-2008. Nested Logit Model (NLM) was applied for analyzing the data and, for this purpose, STATA software was used in the study. Results revealed that having an activity besides farming, extension of the repayment period of the loan, and large volume of received loans are the factors that had significant negative impacts on loan repayment. On the other hand, factors including high interest rates of loans, having collateral of guarantor, services received from the banks, and long term maturity period for the loans increase the probability of timely loan repayment significantly.