Effect of nitric acid modification on porous characteristics of mesoporous char synthesized from the pyrolysis of used cigarette filters

•Mesoporous carbon from used cigarette filters was chemically surface-modified.•A broad range of physical and chemical characterization has been performed.•The effects of acid concentration and reaction time on surface area were investigated.•Response surface method with three factors and three levels was successfully applied.•An RSM curve was developed leading to a mathematical equation for the obtained data.

Mesoporous char prepared through the pyrolysis of used cigarette filters was chemically modified with nitric acid to enhance its surface acidity. The effects of acid concentration and contact time on BET surface area of the synthesized char were investigated for the first time by applying a full factorial design of experiment with each parameter at three levels. The analysis of variance (ANOVA) showed that both acid concentration and contact time had significant effects on the BET surface area. Response surface method (RSM) analyses showed an excellent R2 value of 88.98% for the developed model. Nitrogen adsorption•desorption experiments revealed a certain but special degree of mesoporosity in the modified char with an average pore size of 3.24 nm. The proximate analysis confirmed a considerable reduction in total ash content of the surface-modified char compared to the non-modified char. A 57.8% increase in the surface acidity compared to the non-modified char was further confirmed by Boehm titration nominating the modified carbon for the adsorption of specific components such as heavy metals.