Effect of alkylamine immobilization level on the performance of hydrophobic activated carbon

Abstract

Activated carbon (AC) was prepared from date palm leaflets using NaOH activation. AC was oxidized using nitric acid, ammonium persulfate and hydrogen peroxide to produce ON, OS and OH, respectively. Oxidized activated carbons were surface functionalized using different alkylamines (methyl-, dimethyl-, ethyl-, diethyl- and diisopropylamines) to produce hydrophobic activated carbons via amide coupling. FTIR showed that –COOH group has either disappeared or decreased on functionalization. TGA showed that alkyl chains were immobilized chemically on carbon surface. Surface area was relatively high for AC (588 m2/g), however, it has decreased on oxidation following the order of ON < OS < OH < AC with a further decrease on surface functionalization. Surface area of ON hydrophobic carbon series (72–259 m2/g) was found higher than other functionalized carbons. ON carbons functionalized with ethylamine and diisopropylamine showed best performance for methylene blue adsorption. The percentage of alkyl chains immobilization plays an important role on hydrophobic carbon performance. Incomplete surface functionalization for ON carbons, due to surface crowdedness, shows better performance in terms of surface area and MB interaction than almost fully functionalized OH carbons.