received by the International Bureau on 06 April 2016 (06.04.2016)

We claim

1. A dewatering process using sustainable deep eutectic solvents (DES) with or without magnetic nanoparticles dispersion as. draw solutions through forward osmosis (FO) comprising the steps:

(i) preparing a deep eutectic solvent (DES) by adding choline chloride in ethylene glycol or glycerol in 1 :2 molar ratio to obtain a mixture and heating the mixture at a temperature in the range of 70° to 90°C;

(ii) optionally dispersing 0.5 to 1% iron oxide based magnetic nanoparticles in the above solvents as obtained in step (i);

(iii) utilising the solvent obtained in steps (i) or (ii) respectively as a draw solution in a membrane based forward osmosis (FO) processes to drive efficient dewatering of different feed solutions at room temperature and pressure in the range of 0-1 bar;

(iv) freezing the diluted draw solution obtained after step (iii) at a temperature in the range of -4 to -10°C to recover potable water and draw solution; and

(v) reusing the recovered draw solution obtained in step (iv) for subsequent forward osmosis (FO) process for dewatering until it loses its driving force.

2. The process as claimed in claim 1 , wherein the driving force is osmotic pressure.

3. The process as claimed in claim 1, wherein the deep eutectic solvent (DES) with and without magnetic nanoparticles have density in the range of 1.10 - 1.2 g.cm^-3; viscosity in the range of 25 - 250 cP; conductance at room temperature in the range of 4 - 15 mS; melting temperature in the range of -15 °C to -20 °C; freezing point in the range of -70 °C to -35 °C; water activity in the range of 0.1 - 0.12; osmotic pressure in the range of 300 - 400 atm; and chemical potential range in the range of 5 - 6 kJ.mol^-1.

4. The process as claimed in claim 1, wherein the membrane is a thin film composite polyamide membrane, whereas, forward osmosis (FO) process of dewatering is selected from the group consisting of desalination of brackish and seawater, water recovery from paint industry and leather industry's effluents, protein enrichment and DN A concentration.

5. The process as claimed in claim 1, wherein the draw solution to feed solution ratio in various forward osmosis (FO) processes is in the range of 1:5 - 1: 10.

6. The process as claimed is claim 1, wherein the potable water can be recovered in the range of 80 - 95% from tannery industry effluent.

7. The process as claimed in claim 1, wherein the recovered draw solution after forward osmosis (FO) containing 10-30 % (v/v) water is effective for subsequent dewatering processes with only 2 - 10 % decline of flux.

8. The process as claimed in claim 1, wherein the potable water can be produced simultaneously during recovery of draw solution obtained after forward osmosis (FO) through chilling.