Nitrate Removal from Groundwater Using Sodium Alginate Doped with Nano-Hydroxyapatite

Abstract

In the present work, the hydroxyapatite/alginate nano-composite adsorbent was prepared by incorporating nano-sized hydroxyapatite (nHAp) into alginate polymer and uses this adsorbent for removal of nitrate from groundwater. The synthesized nano-composite and pure alginate as well as the pure hydroxyapatite were characterized with Fourier Transform Infrared (FT-IR) spectroscopy to ascertain the functional groups. The adsorption characteristics of nitrate from groundwater on the HAp/Alg nano-composite were optimized under different operational parameters like contact time, pH, adsorbent dosage, initial concentration of nitrate and temperature in batch system. Maximum equilibrium capacity reached 99% of nitrate removal by using the HAp/Alg nano-composite after 240min at pH 3; adsorbent dosage, 2g; initial concentration, 100mg/l and temperature, 20°C. The kinetics studies revealed that the pseudo-second-order kinetic model was able to describe the dynamic behavior of the adsorption process by composite adsorbents used in this work. Also, the Langmuir isotherm model is very well fitted to the equilibrium data. The mechanism of NO 3-ions adsorption by the nano-composite adsorbent was described. So, it is concluded that HAp/Alg nano-composite is a relatively efficient and low cost as well as the results validated the feasibility of HAp/Alg nano-composite for highly effective removal of nitrate from an aqueous solution.