Functionalized thermo-responsive microgels for high performance forward osmosis desalination

Abstract

Stimuli-responsive hydrogels were recently proposed for energy-saving forward osmosis (FO) process. However, their low water flux and dewatering ability for reuse make them less attractive for industrial desalination process. In this work, the co-polymer microgels of N-isopropylacrylamide and acrylic acid with different mixing ratios were synthesized using surfactant-free emulsion polymerization to produce submicron-size hydrogels with high surface area and fast swelling-deswelling response. The microgels were employed as draw agents in a laboratory scale FO desalination system. The microgel-based FO process performed a high water flux up to 23.8 LMH and high water recovery ability of 72.4%. In addition, we explored a new conductivity measurement method to online analyze water flux of the FO system. This on-line conductivity analysis approach appeared to be an accurate and efficient method for evaluating microgel-based FO desalination performance. Our experimental data revealed that the stimuli-responsive microgel was an efficient draw agent for FO desalination.

1-Cyclohexylpiperidine as a thermolytic draw solute for osmotically driven membrane processes

“…The potential of thermolytic draw solutes has driven much of the recent interest in forward osmosis (FO) and osmotically driven membrane processes (ODMPs) in general [1,2]. The number of thermolytic draw systems reported in the literature has been rapidly expanding [3][4][5][6][7][8][9]. Previously our group reported the use of switchable polarity solvents (SPSs), specifically dimethylcyclohexylamine (DMCHA) [10], as a thermolytic draw solute, Reaction 1 [11].…”

Ag-loaded thermo-sensitive composite microgels for enhanced catalytic reduction of methylene blue

“…Furthermore, the colored form of MB cannot be biodegraded more easily as compared to its reduced colorless form. Several methods have been designed for the removal of MB and other organic pollutants from waste water such as adsorption desorption strategy [3][4][5][6], c-irradiation [7], ozonation [8][9][10], photocatalysis [11][12][13], ion exchange [14], membrane separation [2], reverse or forward osmosis [15], electrochemical methods [16,17], biochemical materials [18][19][20], but all these methods are either very expensive or cannot remove the pollutants completely. Chemical reduction method used to convert these dyes from toxic state to nontoxic or less toxic form is very easy and environmentally friendly, but the reduction of these dyes without catalyst takes much time.…”

Water desalination by forward (direct) osmosis phenomenon: A comprehensive review

“…Hartanto et al [230] used co-polymer microgel of Nisopropylacrylamide and acrylic acid as draw agent and at the same time developed a novel on-line conductivity method for water flux determination (Fig. 16 [230]).…”

“…The research interest FO desalination draw solutions grew rapidly after the use of ammonium bicarbonate as the draw solution by Elimelech et al [18,83,84]. Being highly soluble and capable of generating high osmotic pressures, the ammonium bicarbonate draw Hartanto Thermo-responsive microgels Centrifugation at 40°C High water recovery, high flux, but heating involved [230] solute resulted in high water flux. Pure product water was recovered by moderate heating up to 60°C which resulted in decomposition of ammonium bicarbonate to form ammonia and carbon dioxide gases.…”