Surface Modification and Characterization of Coconut Shell-Based Activated Carbon Subjected to Acidic and Alkaline Treatments

Abstract

Activated carbon derived from agricultural biomass has been increasingly recognized as a multifunctional material for various applications according to its physicochemical characteristics. The application of activated carbon in adsorption process mainly depends on the surface chemistry and pore structure which is greatly influenced by the treatment method. This study aims to compare the textural characteristics, surface chemistry and surface morphology of coconut shell-based activated carbon modified using chemical surface treatments with hydrochloric acid (HCl) and sodium hydroxide (NaOH). The untreated and treated activated carbons were characterized for their physical and chemical properties including the Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and textural characterization. The FTIR spectra displayed bands confirming the presence of carboxyl, hydroxyl and carbonyl functional groups. The Brunauer–Emmett–Teller (BET) surface area of the untreated activated carbon was 436 m2/g whereas the surface area of the activated carbon modified using 1M NaOH, 1M HCl and 2M HCl was 346, 525 and 372 m2/g, respectively. SEM micrographs showed that many large pores in a honeycomb shape were clearly found on the surface of 1M HCl sample. The pore structure of the activated carbon treated with 2M HCl and NaOH was partially destroyed or enlarged, which decreased the BET surface area. The modification of the coconut shell-based activated carbon with acidic and alkaline treatments has successfully altered the surface functional groups, surface morphology and textural properties of the activated carbon which could improve its adsorptive selectivity on a certain adsorbate.

Recycling of Hazelnut Shell: Synthesis of Boron Carbide by Carbothermic Reaction

“…After sulfuric acid treatment of hazelnut shells (Procedure 2), nearly all groups of lignocellulosic compound vibrations disappeared in the FTIR spectrum (Figure 2a). However, aromatic C = C and C-O (C=O) groups stretching in G rings (1569 and 1253 cm -1 , respectively) were still observed [21][22][23][24]. In addition, a similar result (Figure 2b) was obtained in Procedure 1.…”

Characterization of bioadsorbent produced using incorporated treatment of chemical and carbonization procedures

“…The surface structures of the non-treated PKS have burnt out the pores with tunnel or honeycomb-like structures. The inconsistent pore structure and honeycomb structure on the surface of the adsorbent will lead to smaller surface area [54]. On the other hand, significant cracks were shown on the surface of H 3 PO 4 pretreated PKS bioadsorbent.…”

“…Li et al [51] had mentioned that chemical activator inhibits the formation of volatile matter and other liquid that might deposit in the pore. When the chemical is removed by exhaustive washing, huge amount of porosity was formed [54,55]. With reference to table 7, the highest BET specific surface area 204.64 m 2 g −1 was achieved by CS bioadsorbent treated with H 3 PO 4 at 80°C and further carbonized with the temperature of 700°C.…”

“…The thermal stress (carbonization) resulted in the development of cracks, crevices and slits in the matrix of the ultimate carbon material, as shown in figure 2d. Some researchers had also reported that the activation stage produced an extensive external surface (mesopore and macropore surface area) on the activated carbon with quite a number of irregular cracks and pores [54][55][56]. These pores result from the evaporation of the chemical reagent H 3 PO 4 during carbonization leaving empty spaces [57,58].…”

“…When the chemical is removed by exhaustive washing, huge amount of porosity was formed [54,55]. With royalsocietypublishing.org/journal/rsos R. Soc.…”