Insight into activated carbon from different kinds of chemical activating agents: A review

Activation of waste MDF sawdust charcoal and its reactive dye adsorption characteristics

Characterization of nanoporous carbon fibrous materials obtained by chemical activation of plane tree seed under ultrasonic irradiation

Recycling of waste materials provides an economical and environmentally significant method to reduce the amount of waste. Bioash formed in the gasification process possesses a notable amount of unburned carbon and therefore it can be called a carbon residue. After chemical activation carbon residue could be use to replace activated carbon for example in wastewater purification processes. The effect of chemical activation process variables such as chemical agents and contact time in the chemical activation process were investigated. This study also explored the effectiveness of the chemically activated carbon residue for the removal of phosphate from an aqueous solution. The experimental adsorption study was performed in a batch reactor and the influence of adsorption time, initial phosphate concentration and pH was studied. Due to the carbon residue's low cost and high adsorption capacity, this type of waste has the potential to be utilised for the cost-effective removal of phosphate from wastewaters. Potential adsorbents could be prepared from these carbonaceous by-products and used as an adsorbent for phosphate removal.

Pressurized physical activation: A simple production method for activated carbon with a highly developed pore structure

Activated carbon has a larger surface area and well-developed porosity. It could be served as an absorbent to absorb unwanted materials. Synthesis of activated carbon is carried out via carbonization, physical activation, or chemical activation process. Precursors could be from agri-food industry wastes, municipal wastes, wood, and agricultural wastes. During the production of activated carbon, activating agent will be employed to develop porosity. Research findings indicated that an alkaline hydroxide was used for highly ordered (anthracites)whilezinc chloride and phosphoric acid were employed for low-ordered precursors (lignocellulosic), respectively. Freundlich model and Langmuir isotherm were applied to multi-layer and mono-layer adsorption, respectively. In conclusion, the adsorption capacity (dyes, heavy metals, carbon dioxide and organic pollutants) was strongly depended onto experimental conditions.

In this work, we present the preparation and characterization of biomass-derived activated carbon (AC) in view of its application as electrode material for electrochemical capacitors. Porous carbons are prepared by pyrolysis of chestnut seeds and subsequent activation of the obtained biochar. We investigate here two activation methods, namely, physical by CO2 and chemical using KOH. Morphology, structure and specific surface area (SSA) of synthesized activated carbons are investigated by Brunauer-Emmett-Teller (BET) technique and scanning electron microscopy (SEM). Electrochemical studies show a clear dependence between the activation method (influencing porosity and SSA of AC) and electric capacitance values as well as rate capability of investigated electrodes. It is shown that well-developed porosity and high surface area, achieved by the chemical activation process, result in outstanding electrochemical performance of the chestnut-derived porous carbons.

The preparation of active carbons from coal by chemical and physical activation

The main objective of this study was to produce, under pilot conditions, activated carbons (AC) from two different Caribbean by-products, specifically, sugarcane bagasse and vetiver roots. The produced activated carbons under both physical and chemical activation processes were characterised with respect to their texture and surface chemistry. The textural and chemical analyses showed that the nature of the precursor played a crucial role in determining the main characteristics of the activated carbon that was produced. Indeed, under the pilot production chemical activation conditions, bagasse-derived AC (“Bag-pilot”) showed the highest specific surface area (i.e. Brunauer, Emmett and Teller surface, SBET) with 1,030 m2/g compared to 555 m2/g for vetiver-derived AC (“Vet-pilot”). Porous texture analysis revealed that “Bag-pilot” developed more volume (0.807 cm3/g) than “Vet-pilot” (0.352 cm3/g), whereas “Vet-pilot” displayed more micropores (27 %). As for the surface chemistry, results showed that “Bag-pilot” contain more acidic and basic groups than “Vet-pilot” which makes it more interesting for adsorption purposes. The cost estimate of producing AC from vetiver roots in Haiti revealed that the chemically activated carbon presented the lowest cost at $1.17 per kg compared with 1.46$ per kg for physically activated carbon.

The effects of demineralization and swelling in producing active carbon from Turkish lignites

The use of Lufenuron 50-EC pesticide in oil palm crops affects water quality and aquatic life. This study investigated the adsorption of Lufenuron 50-EC from an aqueous solution using activated carbon derived from oil palm shells (OPSs). Activated carbon (AC) was prepared through physical and chemical activation processes in carbon dioxide environments, using potassium hydroxide (KOH) as a chemical activating agent. The resulting AC was characterized using standard techniques. The most favorable operating parameters were physical activation at 900 °C for 2 h, achieving a BET surface area of 548 m2/g. For chemical activation, at 800 °C, 1 h, and an impregnation ratio (KOH/biochar) of 2:1 (w/w), a BET surface area of 90 m2/g was obtained, which was smaller than that achieved by physical activation. The use of KOH reduced the surface area but generated a high presence of functional groups on the AC surface, which is important for adsorption processes. The AC produced achieved high Lufenuron adsorption yields, reaching a maximum of 96.93%. AC produced at 900 °C with 2 h showed the best performance. Therefore, OPS is an excellent precursor for producing AC with favorable characteristics for pollutant adsorption in aqueous solutions, especially for the insecticide Lufenuron.

Activated carbons (ACs) are porous carbonaceous materials with high surface-to-volume ratios and improved chemical functionality. The physical and chemical properties of ACs and their performance in various technologies such as energy storage, solar cells, catalysis, and gas adsorption/separation is highly dependent on the carbon precursors and the activation/carbonization methods. Among the carbon precursors, biomass has become the essential precursor for producing ACs because it is renewable, low-cost, and readily available. The carbonization and activation of biomass precursors are usually performed via physical, chemical, mechanical, and electrochemical approaches. So far, many chemical activating agents (acidic, basic, and neutral) have been reported to synthesize ACs from biomass. This is because chemical activation offers the advantages of kinetic-controlled chemical reactions, low-activation temperature, and low cost. In particular, basic KOH and NaOH are widely used for synthesizing biomass-derived ACs, which are used in electrochemical supercapacitors (ESCs) and other potential applications. This chapter comprehensively discusses the general characteristics, methods, advantages, and imitations of ACs prepared from biomass and activated with KOH and NaOH activators by highlighting the fundamentals of ACs. Finally, the application and the performance of ACs produced by KOH and NaOH activation for ESCs application are discussed.

The use of an activating agent in chemical activation of activated carbon (AC) production is very important as it will help to open the pore structure of AC as adsorbents and could enhance its performance for adsorption capacity. In this study, a pyridinium-based ionic liquid (IL), 1-butylpyridinium bis(trifluoromethylsulfonyl) imide, [C4Py][Tf2N] has been synthesized by using anion exchange reaction and was characterized using few analyses such as 1H-NMR, 13C-NMR and FTIR. Low-cost AC was synthesized by chemical activation process in which rubber seed shell (RSS) and ionic liquid [C4Py][Tf2N] were employed as the precursor and activating agent, respectively. AC has been prepared with different IL concentration (1% and 10%) at 500°C and 800°C for 2 hours. Sample AC2 shows the highest SBET and VT which are 392.8927 m2/g and 0.2059 cm3/g respectively. The surface morphology of synthesized AC can be clearly seen through FESEM analysis. A high concentration of IL in sample AC10 contributed to blockage of pores by the IL. On the other hand, the performance of synthesized AC for CO2 adsorption capacity also studied by using static volumetric technique at 1 bar and 25°C. Sample AC2 contributed the highest CO2 uptakes which is 50.783 cm3/g. This current work shows that the use of low concentration IL as an activating agent has the potential to produce porous AC, which offers low-cost, green technology as well as promising application towards CO2 capture.

Fast and efficient adsorption of methylene green 5 on activated carbon prepared from new chemical activation method

Activated carbon (AC) was synthesized from oil palm shell(OPS)through physical (AC-800-2 and AC-900-2) and chemical (AC-750-1.5-3:1and AC-800-1-2:1) activation processes in a carbon dioxide atmosphere.KOH was used as an activating agent in the impregnation process inthe case of chemical activation. The synthesized ACs were characterizedby proximate and ultimate analysis, Fourier transform infrared (FTIR)spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, scanningelectron microscopy (SEM), and textural properties of the samples.The tested properties, including surface area (SBET), pore volume (VT), and average pore size (SP), were determined by the Brunauer-Emmet-Teller (BET) methodand the Barrett-Joyner-Halenda (BJH) model. Lufenuron adsorption resultsdemonstrated that AC-900-2 achieved the highest lufenuron removalyield of 96.9%. The samples were best represented overall by the pseudo-second-orderkinetic model, with R2 values between0.91 and 0.99. This suggests that the lufenuron adsorption processonto the activated carbons produced in this study was related to thechemisorption process. In addition, this adsorption process was spontaneous,exothermic, and exhibited a high probability of reversibility forsamples AC-900-2, AC-750-1.5-3:1, and AC-800-1-2:1, with van der Waalsforces and hydrogen bonds playing a significant role in the interactionbetween lufenuron and AC. In contrast, for sample AC-800-2, the adsorptionprocess required an increase in temperature to become spontaneous,and the process was endothermic and irreversible. In general, thehigh percentages of adsorption observed in the AC produced by physicaland chemical activation could be explained by the strong interactionsof the surface functional groups with lufenuron. In the case of physicallyactivated carbon, the high surface area provides more sites availablefor these interactions. In the case of chemically activated carbon, although the surface area is lower, the functional groups introducedusing KOH improve the adsorption capacity.

Corn stalks char from fast pyrolysis as precursor material for preparation of activated carbon in fluidized bed reactor