Removal Behavior of Nitrate Using Fe-Layered Double Hydroxide Derived from Bittern

Abstract

Nitrate contamination of surface and groundwater is one of the main problems associated with agricultural activities in many part of the world, and there is an urgent need to develop effective materials and process for efficiently removing excess nitrate from aquatic environment. On the other hands, bittern is one of the resources from seawater to be desired for a new utilization, and contains high amounts of Mg and Ca. In this study, we attempted to prepare the adsorbent with high removal performance for nitrate from bittern. The product including Fe-type layered double hydroxide (Fe-LDH), which has nitrate removal ability, was synthesized from bittern with addition of cheap agent, FeCl3. Fe-LDH can be synthesized from bittern with addition of FeCl3, and the product from the bittern has removal ability for nitrate ion. The equilibrium adsorption capacity of the product for nitrate were measured and extrapolated using Langmuir and Freundlich isotherm models, and experimental data are found to fit Freundlich than Langmuir. The calculated maximum adsorption capacity for nitrate is 0.32 0.47 mmol/g. Adsorption of nitrate increase within 30 min and then gradually decrease, due to the ion exchange reaction of Fe-LDH, and Ca is eluted from the product during the nitrate removal. The product can remove nitrate ion selectively in salty solution.