Copper sulfate as draw solute in forward osmosis desalination

• We calculate the osmotic pressure of copper sulfate draw solution as function of concentration.
• We use copper sulfate as draw solute in forward osmosis for brackish water desalination.
• Use of copper sulfate as draw solute does not require energy for the separation of product water from the diluted draw solution.
• We present a method to regenerate the copper sulfate draw solution.

Copper sulfate is presented as a viable draw solute in forward osmosis (FO) for brackish water desalination. In this study, the osmotic pressure of copper sulfate was calculated as a function of concentration. An investigation into the osmotic pressure revealed that copper sulfate draw solution cannot generate enough osmotic pressure to extract water from seawater feed. A laboratory-scale FO unit utilizing a commercial flat-sheet cellulose acetate membrane was used to desalinate brackish water using 200,000 ppm copper sulfate draw solution. An average water flux of 3.57 L/m2 h was observed. Product water with a salt content of 100 ppm was recovered from the diluted copper draw solution without using any energy. The product water was recovered by metathesis precipitation reaction of copper sulfate with barium hydroxide to remove the soluble chemicals as insoluble copper hydroxide and barium sulfate. At the end, copper sulfate draw solution was recovered by the reaction of copper hydroxide with sulfuric acid.