Porosity characteristics of activated carbons derived from olive oil wastes impregnated with H3PO4

Locally discarded olive oil waste was tested as a potential raw material fo r the preparation of activated carbons. Chemical activation by impregnation with H3PO4 was employed using acid solutions of varying concentration in t he range 30-70% followed by thermal treatment at 50-700 degrees C. The deve lopment of porosity was followed from an analysis of the nitrogen adsorptio n isotherms obtained at 77 K by applying standard BET and t-plot methods. C arbons with low to moderate surface areas (273-827 m(2)/g) and total pore v olumes (0.27-0.69 ml/g), containing essentially micropores with diameters o f 8.2 Angstrom, up to 12.4 Angstrom were obtained. Increasing the concentra tion of impregnant led to the development of porosity with the optimum bein g attained at 60% H3PO4. Phosphoric acid is visualized as acting both as an acid catalyst promoting bond-cleavage reactions and the formation of new c rosslinks and also as a reactant which combines with organic species to for m phosphate and polyphosphate bridges which connect and crosslink biopolyme r fragments. The present study suggests many applications for environmental pollution control, firstly by utilizing accumulating low-cost agricultural by-products and secondly by producing a multi-purpose high-capacity adsorb ent useful in the remediation of micropollutants in various water courses.