Structural and adsorption characteristics of potassium carbonate activated biochar

Abstract

Potassium carbonate activated biochar (450 C, 600 C and 750 C) and nonactivated biochar (600 C)were prepared by using corn stalk as the raw material. These biochar samples were labeled as KBC450, KBC600, KBC750 and BC600. The physical and chemical properties of the biochar were strongly influenced by the activation of potassium carbonate. After activation with potassium carbonate, the aromatic, hydrophobic and non-polar properties of the biochar were enhanced to form an aromatized non-polar surface, and the aromatic properties were enhanced with the increase of the pyrolysis temperature. The outside surface of the activated biochar was similar to that of porous sponge with a mesoporous-microporous composite structure inside. The specific surface area of KBC600 was 5 times that of BC600, and KBC750 had a maximum surface area of 815 m 2 g À1 . Batch adsorption experiments showed that the adsorption capacity of KBC for naphthalene increased with the increase of pyrolysis temperature. The adsorption capacity of the biochar for naphthalene showed a significant positive correlation with O/C and (O + N)/C. KBC750 with the strongest surface hydrophobicity and the largest specific surface area had the largest adsorption capacity of 130.7 mg g À1. Physical adsorption and p-p EDA were the main adsorption mechanisms.

One-pot activation and pyrolysis of Moroccan Gelidium sesquipedale red macroalgae residue: production of an efficient adsorbent biochar

“…A strong peak at 1028 cm −1 , which can be attributed to the stretching vibration of -C-O of the hydroxyl functions of the carbohydrate of raw residues of AG, decreased in intensity for all of the activated biochars due to the degradation of carbohydrate (Liu et al 2016). The peak around 1035-1050 cm −1 which is detected for AcBC-KOH (2.5 wt%), and AcBC-NaOH (2.5 wt%) corresponds to the angular deformation in plane of C-H bonds of the aromatic rings (Zhu et al 2018). While, the peaks around 1143 cm −1 correspond to C-O stretching vibration of esters bonds (Li et al 2017).…”

“…The FTIR spectra clearly indicate that the pyrolysis significantly modified the chemical surface of the AG. A wide band at 3284 cm −1 attributed to the -OH stretching vibration of hydroxyl groups (Aboulkas et al 2017;Zhu et al 2018); this band disappeared for the BC and all of the AcBC after the pyrolysis process, due to dihydroxylation during the pyrolysis. These findings were confirmed by the O/C ratio.…”

“…These characteristic bands of the aliphatic groups disappeared after the pyrolysis process for the BC and all of the AcBC. The peak at 1635 cm −1 , which can be assigned to C=O of carboxyl and C=C stretching vibrations, corresponds to carboxylic groups of hemicelluloses (Pandey 1999;Zhu et al 2018). This peak disappeared for the BC and all AcBC, due to decarboxylation reactions.…”

Preparation of KOH and H3PO4 Modified Biochar and Its Application in Methylene Blue Removal from Aqueous Solution

“…The main groups in CSBC included OH, aliphatic C, C=O and C=C, carboxyl anions (affected by C=O stretching), Si-O and C-H [30]. The main groups in KOH-CSBC included OH, C=O and C=C, substances in the phenolic O-H band, alkenes (affected by C-H bending), cellulosic ethers (affected by C-O-C stretching), aromatic C-H, and CH-of alkenes and alkane [31]. The modification of KOH led to the disappearance of aliphatic C and carboxyl anions due to the high pyrolytic temperature (700 • C).…”

“…C-H, and CH-of alkenes and alkane [31]. The modification of KOH led to the disappearance of aliphatic C and carboxyl anions due to the high pyrolytic temperature (700 °C).…”