Evaluation of Freundlich and Langmuir adsorption isotherm models for rice husk adsorbent in water salinity purification.

Quality water resources are limited. The use of biological adsorbents in reducing water salinity is a new and environmentally friendly method. The purpose of this article is to determine the amount of salinity removal by the rice husk adsorbent and estimate the amount of absorption by Freundlich and Langmuir adsorption isotherm models and their evaluation. In this study, a tank (part of the physical model) with a height of approximately 50 cm and a diameter of 20 cm was used, and it was divided into two parts based on the height of the tank. In the center of the location of the absorber under study, a specific thickness of 8 cm was considered. On both sides of the absorbent layer, either upwards (reservoir surface) or downwards (reservoir bottom), layers of silica sand with 0.3, 0.6 and 1 cm granularity were placed in a height of 5 cm. Water quality treatments including calcium and magnesium, sodium and chlorine (salinity) at four salinity concentrations of 0.2, 0.5, 0.7 and 1 dS/m were passed through the rice husk adsorbent and the amount of cat ions and anions absorbed by the adsorbent It was measured. The results showed that for different concentrations, absorption is very high at the beginning and decreases over time. The equilibrium time for qualitative parameters of calcium and magnesium, sodium and chlorine obtained between 60 and 90 (at a water temperature of 25 degrees Celsius and an acidity of 7.4) minutes. The results showed that on average, a high percentage of calcium, magnesium and sodium cat ions in water (about 50-60%) have been absorbed by rice husk. The results of the adsorption isotherm model showed that the adsorption isotherm model of the Freundlich has a better estimate than the Langmuir model (10 to 15 percent).