I assumed oily nature mainly due to extract oil materials from the plant. You can wash this synthesized materials with acetone, hexane, methanol or other organic solvent to remove the oily nature.

Efficiency of the water treatment will depend on your removal component. Due to oily nature, it act as hydrophobic material. Therefore, hydrophilic substances will not interact with. Without knowing the pollutant material, can't predict the efficiency.

Plants uptake iron in its oxidized forms, Fe2+ (ferrous form) or Fe3+ (ferric form).

Plants use various iron uptake mechanisms. One of these is the chelation mechanism - the plant releases compounds called siderophores which bind iron and enhance its solubility. Iron readily combines with phosphates, carbonates, calcium, magnesium and hydroxide ions. Therefore, in addition to what others may say, the precipitate obtained from extraction

Should undergo the following procedure for proper clean-up:

1) Centrifuge and wash the extract with deionized water and followed by ethanol.

2) Digest the product with hydrofluoric acid(HF)

3) 2. Dry extracts at 75◦C for 4 hours,

4) 3. Collected the powder and calcine slowly to 650◦C in air and cool for 2 hours.

5) 4. The resultant product of probably γ-Fe2O3 nanoparticles should be characterized.

6) Using scanning electron microscope (SEM) for structural composition.

7) The element composition of the product should be identified by an energy dispersive X-ray spectroscopy system (EDX) coupled to the SEM.

8) The crystallization phase analysis should be executed by a powder X-ray diffraction (XRD)

Thank you very much for your reply

The sticky nature of the iron oxide is purely due to the biological derived materials. Kindly inform me what type of iron oxide you prepared - Fe2O3 or Fe3O4.

For water treatment, best you prepare Fe3O4 in aqueous medium ( 1 mole FeCl2 and 2 mole FeCl3. All are hydrated). You can use ammonium hydroxide as precipitating agent and you can add the same upto pH 10-11. Biological materials only help to control the morphology and I hope it doesn't involve in the precipitation reaction. Since you are adding ammonium hydroxide along with the biological system in water medium, ammonia only precipitate the Fe salts.

        For the removal of sticky materials, you can wash with  warm water repeatedly (dont use filter paper) until the wash water shows pH.7.

I hope this may be very useful for your research.

All the best

I have synthesis iron oxide nanoparticles but they have sticky nature after centfuge with dionized water ...can some one please tell me the reason..

Yes , Sticky nature of biologically synthesized Iron Oxide Nanoparticles affect its efficiency for waste water treatment.You need a dry catalyst so the more surface area will be available for catalytic activity.

Biologically synthesized Iron Oxide Nano particles affect its efficiency for waste water treatment, in small scale. But for large scale you have to adopt cheaper methods.