Biodegradable air filter from date palm and method of fabrication thereof

A method of fabricating a biodegradable air filter, comprising:

• isolating cellulose nanofibers from a bleached date palm tree composition obtained by treating date palm solids with a solution comprising NaOH at a temperature of 125 to 175° C.;
• preparing a first carbon by heating a date processing waste under an inert atmosphere at a temperature of 500 to 600° C.;
• heating the first carbon with NaOH under an inert atmosphere at a temperature of 700 to 800° C. to form a second carbon;
• washing the second carbon with water and drying to form an activated carbon;
• mixing the cellulose nanofibers with water and sonicating for 1 to 5 minutes at 300 to 700 watts (W) to form a first suspension;
• mixing the activated carbon with the first suspension to obtain a second suspension;
• adding an aqueous solution of a polyalkylene glycol binder to the second suspension to obtain a solvent mixture;
• sonicating the solvent mixture for 2 to 10 minutes at 300 to 700 W;
• filtering the solvent mixture on a porous substrate to obtain a layer;
• and
• drying the layer at a temperature of 100 to 120° C. for 0.5 to 2 hours to obtain the biodegradable air filter in the form of a solidified structure.