Hydrochars based on cigarette butts as a recycled material for the adsorption of pollutants

Abstract This paper reports the synthesis of hydrochair from cigarette butts (CBs) via low-temperature hydrothermal carbonization without using inert gas. The processing time and applicability of the material for removal of methylene blue (MB) was also examined. The proposed material exhibited significant capacity for adsorption in a basic environment, owing to excess OH − ions that enhanced the negative potential of the adsorbent surfaces, resulting in greater removal of MB. The amount of MB adsorbed on the activated samples was approximately three-times higher than on the non-activated coals. The obtained kinetic data were better fit with pseudo-second order and Elovich models. The Langmuir model best correlated with the equilibrium data suggesting that the adsorption of MB on the hydrochars occurred predominantly via chemisorption. The thermodynamic parameters indicated the spontaneity of the adsorption process of MB (ΔG°   0). The positive entropy values (ΔS° > 0) indicated increasing irregularity at the solution-solid interfaces, demonstrating high affinity of adsorption owing to the effectiveness of adsorbent-adsorbate attraction forces. The CB-prepared hydrochars have great potential in applications aimed at the removal of organic pollutants from aqueous solutions.