Simultaneous optimization of activation conditions of alperujo (two-phase olive mill waste) using a desirability function: Production of porous carbons for adsorption and energy storage

Abstract

Valorization of agro-industrial waste is considered an essential step towards a circular economy. The potentialreuse of these byproducts in practical applications requires feasibility assessments and optimization of variablesin order to be profitable. In the present study, an abundant and problematic residue from the olive oil industry,“alperujo” (two-phase olive mill waste), was used as precursor material for activated carbons. A simultaneousoptimization methodology was applied to maximize two response variables: energy storage capacity and lead(Pb) removal efficiency. The simultaneous optimum conditions were 3.66 g of KOH per g of carbonized residueand a temperature of 650 ◦C for 120 min. The result was a microporous activated carbon with an energy storagecapacity of 252 F/g and a lead removal from aqueous solutions of 68.8 %. These values are comparable withthose offered by commercial activated carbons, evidencing that porous materials obtained from alperujo usingunique activating conditions for both applications present a remarkable performance. The novelty of the presentstudy lies in the application of a useful statistical methodology for simultaneous optimization through the“desirability function”, resulting in a reduction in cost and time. Our results have demonstrated that it is possibleto generate activated carbons with the highest performance for two different applications using the samecombination of activation variables.