Concentration Retention and Enrichment of Ammonia Bicarbonate Draw Solution in Forward Osmosis Desalination

Bikasha Chandra Panda1, Morgan Harry2, and Ashok Kumar Ghosh3

1. Department of Civil Engineering, IGIT Sarang, Dhenkanal-759146, Odisha, India

2. Department of Chemical Engineering, New Mexico Institute of Mining and Technology, Socorro, NM 87801, USA

3. Department of Mechanical Engineering, New Mexico Institute of Mining and Technology, Socorro, NM 87801, USA

Abstract: Following the presentation of the novel ammonia-carbon dioxide forward osmosis (FO) desalination method in 2005, ammonium bicarbonate has been used frequently for the preparation of draw solution. However, the ammonium bicarbonate (NH4HCO3) salt decomposes at higher temperatures and retains less concentration than the solute added for desired concentration. In this study, the concentration retention properties of NH4HCO3 draw solution, in relation to temperature, time and desired concentration have been investigated. In order to achieve the desired concentration, the solution was enriched either with additional amount of NH4HCO3 or ammonium hydroxide (NH4OH) solution. The results revealed that NH4OH is the good candidate to be added to the solution to get the targeted concentration.

Key words: desalination, forward osmosis, draw solution, ammonium bicarbonate, concentration retention, enrichment