Lignin Based Activated Carbon Using H3PO4 Activation

Abstract

Activated carbon (AC) with a very high surface area of over 2000 m2/g was produced from low sulfur acid hydrotropic lignin (AHL) from poplar wood using H3PO4 at a moderate temperature of 450 °C (AHL-AC6). ACs with similar surface areas were also obtained under the same activation condition from commercial hardwood alkali lignin and lignosulfonate. Initial evaluation of AC performance was carried out using nitrogen adsorption-desorption and dye adsorption. AHL-AC6 exhibited the best specific surface area and dye adsorption performance. Furthermore, the adsorption results of congo red (CR) and methylene blue (MB) showed AHL-AC6 had greater adsorption capacity than those reported in literature. The dye adsorption data fit to the Langmuir model well. The fitting parameter suggests the adsorption is nearly strong and near irreversible, especially for MB. The present study for the first time provided a procedure for producing AC from lignin with Brunauer–Emmett–Teller (BET) surface area >2000 m2/g using low cost and low environmental impact H3PO4 at moderate temperatures.

Lignin Derived Porous Carbons: Synthesis Methods and Supercapacitor Applications

“…From the perspective of synthesis, the preparation of LDPC electrodes relies highly on the traditional carbonization-activation strategy. Chemical activation refers to activating lignin-derived chars using various traditional activation agents, such as KOH, [51] H 3 PO 4 , [52][53][54][55] metals carbonates, [56][57][58] and bicarbonates. [59,60] KOH activation methods could produce porous carbons with high SSAs of 1000-3000 m 2 g −1 [61] and developed micro/mesopores.…”

“…Lignin has become a popular precursor for the synthesis of LDPCs using H 3 PO 4 activation. [52][53][54][55] Lignin could form a phosphate linkage between the phenolic hydroxyl group and the phosphate ions, which could help the distribution of the H 3 PO 4 activation agent homogeneously. [52] KOH activation is commonly used to synthesize porous carbon materials with high SSAs ranging from 1000 to 3000 m 2 g −1 .…”

Lignin to value-added chemicals and advanced materials: extraction, degradation, and functionalization

“…The lignin-based activated carbon exhibited a large surface area of over 2000 m 2 g −1 and excellent adsorption capacity for Congo red and methylene blue. 213…”

“…The chemical activation of lignin-based carbon by activation agents such as KOH, H 3 PO 4 and ZnCl 2 can increase its porosity. 213 The activation agent plays a role in removing O and H from the lignin precursor in the form of water, resulting in the formation of porosity. 20 For example, using low sulfur acid hydrotropic lignin as the carbon precursor and H 3 PO 4 as the activation agent, lignin-based activated carbon was prepared by carbonizing a mixture of lignin and H 3 PO 4 .…”

“…The lignin-based activated carbon exhibited a large surface area of over 2000 m 2 g −1 and excellent adsorption capacity for Congo red and methylene blue. 213 Besides chemical activation, the freeze-drying process is used to prepare lignin-based activated carbon with a porous structure and high specific surface area. Lignin-derived carbon nanosheets were prepared as a rhodamine dye adsorbent via the freeze-drying of lignin and high-temperature carbonization.…”