In this study, the production of porous carbon fibers from viscose fibers was investigated. The effects of final carbonization temperature (600–1000 °C) and heating rate (6–600 °C h⁻¹), which determine the carbonization process, on carbon yield, and specific surface area were investigated using a central composite design. The statistical models found were then used to optimize both the yield and the porosity of the carbonized fibers, which are the most important factors for further use as precursors for activated carbon fibers. Despite the contrary effects, porous carbon fibers with a yield of 21.2% could be produced, which at the same time have a specific surface area of 175 m² g⁻¹. The fibers produced were also characterized by SEM, FTIR and Raman spectroscopy, XRD and CHNS analysis.

Growing pollution is making it necessary to find new strategies and materials for the removal of undesired compounds from the environment. Adsorption is still one of the simplest and most efficient routes for the remediation of air, soil, and water. However, the choice of adsorbent for a given application ultimately depends on its performance assessment results. Here, we show that the uptake of and capacity for dimethoate adsorption by different viscose-derived (activated) carbons strongly depend on the adsorbent dose applied in the adsorption measurements. The specific surface areas of the investigated materials varied across a wide range from 264 m² g⁻¹ to 2833 m² g⁻¹. For a dimethoate concentration of 5 × 10⁻⁴ mol L⁻¹ and a high adsorbent dose of 10 mg mL⁻¹, the adsorption capacities were all below 15 mg g⁻¹. In the case of high-surface-area activated carbons, the uptakes were almost 100% under identical conditions. However, when the adsorbent dose was reduced to 0.01 mg mL⁻¹, uptake was significantly reduced, but adsorption capacities as high as 1280 mg g⁻¹ were obtained. Further, adsorption capacities were linked to adsorbents’ physical and chemical properties (specific surface area, pore size distribution, chemical composition), and thermodynamic parameters for the adsorption process were evaluated. Based on the Gibbs free energy of the adsorption process, it can be suggested that physisorption was operative for all studied adsorbents. Finally, we suggest that a proper comparison of different adsorbents requires standardization of the protocols used to evaluate pollutant uptakes and adsorption capacities.

The increasing usage of pesticides to boost food production inevitably leads to their presence in food samples, requiring the development of efficient methods for their removal. Here, we show that carefully tuned viscose-derived activated carbon fibers can be used for malathion and chlorpyrifos removal from liquid samples, even in complex matrices such as lemon juice and mint ethanol extract. Adsorbents were produced using the Design of Experiments protocol for varying activation conditions (carbonization at 850 °C; activation temperature between 670 and 870 °C; activation time from 30 to 180 min; and CO₂ flow rate from 10 to 80 L h⁻¹) and characterized in terms of physical and chemical properties (SEM, EDX, BET, FTIR). Pesticide adsorption kinetics and thermodynamics were then addressed. It was shown that some of the developed adsorbents are also capable of the selective removal of chlorpyrifos in the presence of malathion. The selected materials were not affected by complex matrices of real samples. Moreover, the adsorbent can be regenerated at least five times without pronounced performance losses. We suggest that the adsorptive removal of food contaminants can effectively improve food safety and quality, unlike other methods currently in use, which negatively affect the nutritional value of food products. Finally, data-based models trained on well-characterized materials libraries can direct the synthesis of novel adsorbents for the desired application in food processing.

Viscose fibers were impregnated with different concentrations of diammonium hydrogen phosphate (DAHP), carbonized, activated, and tested as high-performance electrode materials for supercapacitors. The yield of these activated carbon fibers (ACFs) could be increased by a factor of 14 by using DAHP compared to ACF without impregnation. These specific activation procedures yielded a high specific surface area of more than 2700 m²·g⁻¹ with a pore size distribution (PSD) suitable for use as a supercapacitor electrode. The electrode materials were implemented in symmetric supercapacitors using TEMA BF₄ as electrolyte and cyclic voltammetry measurements showed high specific capacitances of up to 167 F·g⁻¹. Furthermore, the devices showed high energy densities of up to 21.4 W·h·kg⁻¹ and high-power densities of up to 8.7 kW·kg⁻¹. The supercapacitors featured high capacity retention (96%) after 10,000 cycles. These results show that ACFs made of viscose fibers, previously impregnated with DAHP, can be used as high-performance electrodes in supercapacitors for energy storage applications.