Experimental and theoretical parametric study of forward osmosis system using NH4HCO3 and NaCl draw solutes

Abstract

Forward osmosis (FO), is an emerging membrane technology for water desalination, wastewater treatment and diverse other applications. The technology has known growing attention mainly due to its potential for energy costs reduction. Although FO performances, expressed in terms of water flux and reverse solute flux, have been investigated for individual draw solute (DS) under a certain fixed conditions of concentration and temperature, sensitivity analysis of the impact of the DS concentration and both feed and draw solutions temperature and flowrate on the process performance have not yet been extensively addressed in the literature. In this work, a simulation approach combined with an experimental study has been conducted to evaluate the effect of operating conditions on the process performance and internal concentration polarization phenomena (ICP) using ammonium bicarbonate and sodium chloride as draw solutes. Osmotic performances of the two considered DSs were contrasted throughout the entire ranges of concentration, temperature, and cross-flow velocity. Differences between predicted and experimental results for concentration-dependent, temperature-dependent, and flowrate-dependent fluxes [Jw, Js], expressed in terms of mean absolute error have been consecutively estimated at [3.24%, 6.54%], [3.43%, 4.22%], and [6.04%, 3.08%] for NaCl, and [4.15%, 3.33%], [2.27%, 6.8%], and [5.58%, 2.87%] for NH4HCO3. Regarding ICP, the increase of concentration has shown to induce severe ICP effects causing up to 70.25% of water flux decline at 2 M NaCl. Meanwhile, increasing operating temperature have demonstrated a slight reduction of ICP; 11.63% for NaCl DS and 10.15% for ammonium bicarbonate for an increase of temperature from 10 to 35 °C.