If the black particles are in colloidal range they will get dispersed during solution making otherwise they will settle down. And surely you can make dilute solutions in small vials to collect maximum particles through magnet if they are magnetic 

Try to dissolve the gel and then filtered

Thanks for answering Farid F. Orudzhev. Please suggest commonly available organic solvent  in which dissolution does not take metallic particles but selectively dissolve organic matter. Thanks

Make a solution and use a stronger Magnet along the side of wall of Falcon tube and discard the solution,you will get black ppts on the wall of falcon. and similarly  wash them 2 to 3 times.

Thanks for your valuable suggestion dear Muhammad Abbas, I usually do separation of my metallic magnetic particles when I synthesize it from different routes after grinding and separation works well; here sticky nature causes problem. Now OK! on your suggestion if  I make solution of this material say in water then what about black particles will they not be dissolved along with this water soluble Jell?

If the black particles are in colloidal range they will get dispersed during solution making otherwise they will settle down. And surely you can make dilute solutions in small vials to collect maximum particles through magnet if they are magnetic 

Thank you Muhammad Abbas for your answers. I really appreciate your understanding and solution providing to my problem.

I would appreciate if you upvote/recommend my answers.