Adsorption of Pb(II) and Fe(II) by mesoporous composite activated carbon from Tithonia diversifolia stalk and Theobroma cacao pod

Mesoporous composite activated carbon (AC) prepared from cocoa (Theobroma cacao) pod and sunflower (Tithonia diversifolia) stalk were evaluated for the sorption of Pb(II) and Fe(II) from wastewater. The different biomasses were acid activated by wet impregnation with phosphoric acid and carbonised at 500 °C. Adsorbents studied were AC from Theobroma cacao (TC-AC) and Theobroma-Tithonia blend (TT-AC) in a mass ratio of 75–25 wt%. The adsorbent was characterised by FTIR, BET and SEM–EDS. The specific surface areas were 237.445 and 392.508 m²/g for TC-AC and TT-AC respectively. Parametric studies revealed that adsorbate uptake reduced with increased initial concentration and increased with increasing dosage and contact time. The monolayer adsorption capacities for Pb(II) sorption onto TC-AC and TT-AC were 47.17 and 46.95 mg/g and for Fe(II) sorption onto TC-AC and TT-AC was 37.45 and 37.04 mg/g respectively. Langmuir isotherm and pseudo-second-order kinetic models were the best fits for the adsorption process. From the study, it has been observed that high-quality mesoporous adsorbent can be obtained from the carbonisation of the cocoa pod and sunflower stalk for water treatment applications.