Preparation of High-Surface-Area Carbon Adsorbents from Plum Seed Pods Via Thermochemical Activation

Abstract

Activated carbon is among the most widely used adsorbent materials because of its high specific surface area, developed pore structure, chemical stability, and capacity to adsorb various organic and inorganic pollutants. This study aimed to prepare and characterise activated carbon adsorbents from plum seed shells through thermochemical activation using KOH and NaOH as activating agents. Activated carbon adsorbents were prepared from plum seed shells by carbonisation followed by thermochemical activation with potassium hydroxide and sodium hydroxide. The raw biomass was washed, dried, crushed, carbonised at 500 °C, and subsequently activated under different alkali-treatment conditions. The prepared carbon materials were washed, neutralised, dried, and characterised using nitrogen adsorption–desorption analysis, BET surface area measurement, t-Plot and BJH methods, benzene vapour adsorption, scanning electron microscopy with energy-dispersive X-ray analysis, Fourier-transform infrared spectroscopy, and X-ray diffraction analysis. The untreated plum seed shell showed a very low BET surface area of 1.3444 m²/g, whereas carbonisation at 500 °C increased the surface area to 84.2376 m²/g. Steam activation further increased the BET surface area to 542.8618 m²/g. Among the chemically activated samples, the KOH-activated carbon prepared at a carbonizate-to-KOH ratio of 1:0.05 showed the highest BET surface area of 944.2450 m²/g, micropore surface area of 728.0441 m²/g, total pore volume of 0.497989 cm³/g, and micropore volume of 0.383966 cm³/g. Benzene vapour adsorption measurements also showed improved adsorption performance, with the highest adsorption capacity of 3.660 mmol/g and a benzene-derived surface area of 881.24 m²/g for the same sample. SEM observations confirmed the formation of irregular porous surfaces, while FTIR and XRD analyses indicated structural transformation towards a predominantly amorphous carbonaceous material. The results show that plum seed shells can be converted into porous activated carbon adsorbents, with KOH activation providing better textural and adsorption properties than NaOH activation under the studied conditions.