Novel draw solution system based on trisodium dicarboxymethyl alaninate for water desalination applications

In this study, a novel draw solution based on trisodium dicarboxymethyl alaninate and citric acid was evaluated for its potential to be utilized in forward osmosis water desalination systems. The effect of various operation parameters (including draw solution concentration, feed stream salination, and operation temperature) on desalination efficiency of the forward osmosis system utilizing such novel draw solutions was investigated, utilizing a bench-scale cross/tangential flow membrane testing system. In addition, images of membranes’ surfaces produced by scanning electron microscopes were also studied to determine the nature of fouling resulting from prolonged operations, and the effectiveness of applied cleaning procedures. Compared to the more well-established trisodium citrate-based draw solution, the novel draw solution exhibited higher water flux against deionized water, while also offering low reverse solute flux and good regeneration capability through low-pressure reverse osmosis. In particular, experiment results showed that at the initial concentration of 250 g L⁻¹, the forward osmosis system utilizing such novel draw solution could achieve specific water fluxes of up to 9.23 L m⁻² h⁻¹ against deionized water, and up to 4.95 L m⁻² h⁻¹ against feed streams of 20‰ salinity. Additionally, such system also has relatively low operational loss, with specific reverse solute flux and reverse osmosis recovery rate of 0.22 g L⁻¹ and 98.65%, respectively. Overall, the novel draw solution was proven to be effective for water desalination applications, while also being relatively cheap, readily-available in large quantities, low in toxicity, and relatively eco-friendly.

Graphical Abstract