In an article recently published in the open access journal Polymersresearchers discussed the wood-based microporous activated carbon fiber preparation and its usefulness for copper ion removal.
Study: Synthesis of activated carbon fiber based on wood with dominant microporosity for the elimination of copper ions. Image Credit: andriano.cz/Shutterstock.com
Several heavy metals are being transferred to surface and ground waters due to rapidly expanding industrial activity, posing significant environmental hazards. Copper is a widely used metal in a variety of industries. These companies generate a lot of wastewater and sludge with Cu2+ ions it contains, which has a negative impact on the aquatic environment.
Heavy metals are toxic and non-biodegradable, they affect human health and cause central nervous system disorders. As a result, develop effective solutions to clean Cu2+-polluted wastewater before it is discharged into the environment is critical.
In the context of environmental protection, activated carbon fiber (ACF) is the most suitable porous carbon material. Liquefied wood-derived ACF (LWACF) is successfully synthesized and used as supercapacitor electrodes and potential adsorbents. However, due to the difficulty of adjusting the pore size distribution (PSD), it has not yet been used in heavy metal adsorption.
The synthesis and use of mesoporous LWACF with ZnCl2 and H3Purchase order4 activation are widely documented as a matrix phase at this time, but research on microporous LWACF for heavy metal adsorption is limited. Steam activation has become a popular approach for carbon activation, and it can help carbon compounds increase their PSD.
Summary course of the LWACF series. Image Credit: Jin, Z et al., Polymers
About the study
In the present study, the authors presented the use of steam activation treatments to increase the surface area of ACF made from LWACF and to increase the pore size distribution. The effects of various preparation conditions on the pore architectures were also illustrated. Single-factor analysis studies were used to explore the synthesis parameters of LWACF, and static adsorption experiments were used to study the adsorption capabilities of this adsorbent.
The hook was pulverized and sieved to produce the precursor fibers, which were obtained by a number of procedures including melt spinning, liquefaction and hardening. By adding a stream of water combined with a stream of nitrogen, the liquefied wood precursor fiber (LWPF) was activated at 800°C for 60, 140 and 220 minutes.
Then they were cooled in a stream of nitrogen to room temperature. X-ray photoelectron spectroscopy (XPS) measurements were used to analyze the surface chemistry, and scanning electron microscopy was used to examine the morphology of the prepared LWACF. At 196°C, the porous structure of LWACF was investigated using a volumetric adsorption analyzer. The specific surface (SBET) and the average pore size (Da) were calculated using the Brunauer-Emmett-Teller (BET) model.
The t-plot approach was used to measure the specific surface area of micropores (Smid), while density functional theory (DFT) was used to determine the volume of mesopores (Vme), micropore volume (Vmid) and DSP. Cu2+ solutions with pH = 5.5 were made by dissolving 0.078125 g of CuSO4H2O in 1000 mL of distilled water. An atomic absorption spectrophotometer was used to determine the amounts of heavy metal ions in the filtrates.
SEM images of LWACF activated for 60 min (A,B), 140 minutes (VS,D) and 220 minutes (E,F) at 800°C. Image Credit: Jin, Z et al., Polymers
The average fiber diameter of LWACF increased from 27.2 μm to 13.2 μm as the activation time increased, while the specific surface area increased from 1025 to 2478 m2/g. Steam activation accelerated the development of microporosity while causing minimal pore enlargement. Due to an increase in the number of micropores and acid-oxygen groups, increasing the steam activation period exponentially increased the Cu removal efficiency2+ at a constant dose of adsorbent.
Moreover, when the porous carbon fiber dose was increased from 0.1 to 0.5 g/L, the Cu removal efficiency2+ was incremented from 55.2% to 99.4% for LWACF activated for 220 minutes at 800°C. The average fiber diameter of LWACF decreased from 27.2 µm to 13.2 µm.
When the porous activated carbon fiber dose was increased from 0.1 to 0.5 g, the Cu removal efficiency2+ increased from 43.6% to 66.1% for LWACF-140 and from 55.2% to 99.4% for LWACF-220. Controlled steam activation of the carbon surface introduced acidic functional groups like carboxyl and carbonyl, as well as rendered the carbon surfaces hydrophilic, which promoted strong attractive contacts between Cu2+ and the active surface of the LWACF. Cu2+ removal efficiency has been improved by increasing activation time while maintaining a fixed adsorbent dosage.
Cu removal efficiency2+ at constant adsorbent dose for LWACF with different activation times at 800°C. Image Credit: Jin, Z et al., Polymers
In conclusion, this study presented the development of a series of LWACF samples that could be used to remove Cu2+ ions of aqueous solutions. The effects of steam activation pretreatment were investigated to determine the adsorption capabilities of generated samples for heavy metal removal.
Longer activation times improved the Cu of LWACF2+ ion removal efficiency. The maximum removal efficiency was 99.4%. The synthesized LWACF proved to be a very efficient adsorbent for Cu2+ treatment of wastewater contaminated with ions.
Overall, the authors believe that the results of this study will encourage the widespread use of activated carbon fiber from biomass in the field of environmental protection.
Jin, Z., Zeng, Z., Hu, S., et al. Synthesis of activated carbon fiber based on wood with dominant microporosity for the elimination of copper ions. Polymers 14(6), 1088 (2022). https://www.mdpi.com/2073-4360/14/6/1088