Integrated photoelectrochemical (PEC)-forward osmosis (FO) system for hydrogen production and fertigation application

Abstract

This study proposes an integrated system that combines a photoelectrochemical (PEC) system and forward osmosis (FO) system in tandem operation to address water, energy, and food (WEF) scarcity. The system utilizes a combination of ammonium sulfite and ammonium sulfate solution to represent wet flue gas desulfurization products from the ammonia scrubbing process commonly used in oil and gas producing countries. Under simulated sunlight, the sulfurous solution in the PEC system is oxidized at a reduced titania nanotube array (TNA) working electrode to produce hydrogen, a clean energy source (Energy). The oxidized sulfurous solution entering the draw solution (DS) compartment of the FO unit was then diluted when the FO system operates against simulated brackish water as the feed solution (FS, Water). The DS effluent is recirculated to ensure continuous operation of both PEC and FO systems. At a certain point in time, the DS effluent is also used as a cultivation solution for basil plants, the growth is visually more favorable compared to those supplied with tap water (Food). A concentrated DS (0.8:0.2 ratio of (NH4)2SO3:(NH4)2SO4) showed excellent water desalination performance. It had a high water flux of 17 LMH with 11.8 % water recovery, highest salt rejection (98.6 % for Na+ and 98.3 for Cl−), and lowest reverse solute flux (RSF) (3.5 g‧m−2‧h−1 for SO42−, 5.25 g‧m−2‧h−1 for SO32−, 3.1 g‧m−2‧h−1 for NH4+) against 5 g‧L−1 NaCl FS for 5 h, with a cathodic current density of 0.15 A‧cm−2. Overall, this study demonstrates the successful implementation of a bench-scale integrated system that produces tangible outcomes for water, energy, and food.