Background and Objective: One of the main objectives of the adsorption isotherm models is to determine the maximum capacity of the adsorbent. The main purpose of this study is to investigate the chemical absorption rate of chromium from aqueous solution by rice stem, us More
Background and Objective: One of the main objectives of the adsorption isotherm models is to determine the maximum capacity of the adsorbent. The main purpose of this study is to investigate the chemical absorption rate of chromium from aqueous solution by rice stem, using physico-chemical adsorption isotherm model of Shamohammadi and to compare adsorption isotherm models for determining the maximum capacity of the adsorbent.
Method: The rice stem with particle sizes of 75, 300, 850 and 1200 micron, and the chromium solution with concentrations of 15 to 40 (mg/L) were used in this study.
Findings: The maximum adsorption efficiency of 96.30 % was obtained in in pH=2 using 10 (g/l) of rice stem with particle size of 75 micron. The maximum adsorption capacities of chromium by Langmuir model and Shamohammadi model for the rice stem were obtained as 2.918 and 4.926 (mg/g) in particle size of 75 microns, 2.206 and 3.310 (mg/g) in particle size of 300 microns, 1.838 and 2.617 (mg/g) in particle size of 850 microns and 1.037 and 1.322 (mg/g) in particle size of 1200 microns respectively.
Conclusion: Isotherm absorption studies showed that, based on Shamohammadi model, averagely 20.5% of adsorption occurs as initial adsorption. Moreover, by considering equilibrium adsorption (qe) as a function of initial concentration (C0), not only the precision of the model will be enhanced (according to evaluation criteria), but also the equilibrium capacity of adsorption increases to an average of 26.5% compared to the Langmuir model. Thus, application of the Shamohammadi model increases the capacity of chromium absorption by rice stem by an average of 47% compared to the Langmuir model.
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The purpose of this study was to investigate the effects of electricity tariff liberalization on value added and growth of different economic sectors based on designing a general equilibrium model that can be calculated for Iran and using the social accounting matrix in More
The purpose of this study was to investigate the effects of electricity tariff liberalization on value added and growth of different economic sectors based on designing a general equilibrium model that can be calculated for Iran and using the social accounting matrix in 2011. The government intended to organize the use of energy subsidies in addition to establishing justice in society by implementing the law on targeted subsidies. In this study, the policy of subsidy reform and electricity tariff liberalization has been studied in the form of two scenarios. The first scenario was a 50% reduction in subsidies paid in the electricity sector and the second scenario was the complete elimination of subsidies in the electricity sector. The results of this study showed that the change in electricity tariffs has led to an increase in value added growth in various economic sectors in both scenarios. Meanwhile, the sectors of oil and natural gas, food and electricity supply, water and gas have shown the highest growth in the second scenario compared to the first scenario, and the sectors of construction, wood and paper, non-metallic minerals and other industries.
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In the following paper, short-term interest rate is modeled using some of the most prevalent single factor equilibrium models in Iran. In this research, model’s performance is compared to each other using some indicators relating to model fitness, interest volatil More
In the following paper, short-term interest rate is modeled using some of the most prevalent single factor equilibrium models in Iran. In this research, model’s performance is compared to each other using some indicators relating to model fitness, interest volatility and interest level changes. For this purpose, Islamic treasury bill yield data were obtained from the period 1394 to 1395 and the models were estimated using generalized method of moments. The findings of this research illustrate that Brennan-Schwartz and CKLS models perform better in interest rate fitness compared to other restricted models. Also, Brennan-Schwartz model show more predictive power than other models. In addition, short-term interest rate of Islamic Treasury Bill exhibit some mean reverting feature and the level of long term mean is estimated as well. Although all the models perform poorly in interest rate volatility fitness, there are some evidences showing that it is sensitive to the level of interest rate.
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