Preparation of high surface area carbons from Corncob with KOH etching plus CO2 gasification for the adsorption of dyes and phenols from water

Carbonaceous adsorbents with controllable surface area and the microporous volume ratio (Vmicro/Vpore) were activated from carbonized corncobs (i.e., char) with KOH etching plus CO2 gasification in this work. Activated carbons derived from KOH/char ratio equal to 1 and CO2 gasification time from 0 to 60 min exhibited BET surface area increasing from 1071 to 1991 m2 g−1 and the Vmicro/Vpore values decreasing rapidly from 0.805 to 0.565. And those derived from KOH/char ratio of 4 and CO2 gasification time from 0 to 30 min exhibited high BET surface area from 2402 to 2844 m2 g−1. Scanning electron microscopic (SEM) results revealed that violent reactions took place on the surfaces of honeycombed holes in these carbons when the KOH/char ratio was equal to 1 and CO2 gasification was used. The adsorption of three dyes (MB, BB1, and AB74) and three phenols (phenol, 4-CP, and 2,4-CP) from water on all activated carbons at 30 °C were investigated. Adsorption kinetics was in agreement with the Elovich equation, and the values of the Elovich parameter (1/b) of the carbons with different CO2 gasification time were compared. The equilibrium isotherms were in agreement with the Langmuir equation, and they were used for comparing the amounts of adsorption corresponding to the monolayer coverage of the different carbons.