Preparation Of Activated Carbon Research Articles

Electroadsorption Desalination Performance of Carbon Materials Derived from Coconut Shell without Membrane Separation

This study investigated coconut shells, an abundant and low-cost raw material, as the precursor for activated carbon preparation, and applied a carbonization activation method to prepare carbon materials under different activation conditions. The differences in the performance of biomass derived carbon materials as capacitive deionization (CDI) electrodes were studied under conditions of different activators, activator doses, and activation temperatures. Compared with commercial coconut shell activated carbon, studies have shown that biomass derived carbon electrodes obtained under the optimal preparation conditions of NaOH as the activator, a carbonizer to activator ratio of 1:3, and an activation temperature of 800 ℃ have an excellent electro adsorption performance and the potential to be used as a CDI electrode material. The salt adsorption capacity (SAC) of activated carbon made with coconut shell derived carbon materials after 20min of electro adsorption reached a maximum of 11.47mg/g. After 10 repeated uses, its SAC remained at the original 90.58%, demonstrating an excellent cycling stability.

Structural properties and adsorption performance relationship towards three categories of lignin and their derived biochar

The growing interest in utilizing lignin for dye removal has gained momentum, but there is limited information on the intricate relationship between lignin structural characteristics and adsorption efficacy, especially for its biochar derivatives. This study focused on three types of lignin and their corresponding biochar derivatives. Among them, ZnCl2-activated acidic/alkali densified lignin preparation of lignin-derived active carbon exhibited superior adsorption performance, achieving 526.32 mg/g for methylene blue and 2156.77 mg/g for congo red. Its exceptional adsorption capacity was attributed to its unique structural properties, including low alkyl and O-alkyl group content and high aromatic carbon levels. Furthermore, the adsorption mechanisms adhered to pseudo-second-order kinetics and the Langmuir model, signifying a spontaneous process. Intriguingly, lignin-derived active carbon also demonstrated remarkable recovery capabilities. These findings provide valuable insights into the impact of structural attributes on lignin and its biochar's adsorption performance.

Thermal behavior analysis and reaction mechanism in the preparation of activated carbon by ZnCl2 activation of bamboo fibers

In this study, bamboo powder (BP), bamboo parenchyma cells (PCs), and bamboo fibers (BFs) were used as precursors to prepare activated carbon by ZnCl2 one-step activation to investigate the differences in the pore structures of the three. The results showed that BFs-based activated carbon had a higher specific surface area (2129 m2/g). Subsequently, the activation reaction paths of the BFs-based activated carbon preparation process were analyzed and explored by TGA, XRD, TG-MS-FTIR, EA, and other analytical methods, and the reaction mechanism was inferred. The results showed that the main reaction below 220 °C was the breaking of molecular bonds of oxygen-containing functional groups on hemicellulose, and the pyrolysis by-products at this stage were dominated by small molecules such as H2O, CO2, CH4, CH3OH, and HCHO. The pyrolysis of cellulose and the activation reaction of ZnCl2 were the main reactions between 220 °C and 650 °C. ZnCl2 was a strong dehydrating agent that can form ZnOCl2·2 H2O with intramolecular water molecules, and gradually decompose to form ZnO with the increase in temperature, the main gaseous products in this temperature interval were mainly H2O, CO, CO2, C3H4, and CH4. Above 650 °C, pyrolysis was basically completed and continued to shift to the aromatic structure, with the gaseous products mainly being H2, H2O, CO2, CH4, CO, C3H4, and a small amount of CH3OH and HCHO.

Microwave pyrolysis of waste biomass and synthesis of micro-mesoporous activated carbons: The role of textural properties for CO2 and textile dye adsorption

Hierarchical porous activated carbons (ACs) were efficiently synthesized in less than 2 min using microwaves and phosphoric acid (H3PO4), exhibiting excellent potential as adsorbent for carbon dioxide (CO2) and Methylene Blue (MB). The method emphasizes the development of selective physicochemical and textural properties crucial for CO2 post-combustion capture and textile dye removal from water, using agricultural waste as carbon precursor to address the environmental and economic challenges associated with the preparation of ACs. Dielectric properties confirmed H3PO4 increased the microwave absorption properties of the biomass. Employing a single-step method, the resulting ACs exhibited large specific surface areas exceeding 1000 m2g−1, achieved in less than 2 min and relatively low energies (2.4 GJ ton-1). Sample 0.4H4 displayed a surface area of 1145 m2g−1 and a significant ultra-micropore (<0.7 nm) content, demonstrating a CO2 uptake of 4.1 and 2.8 mmolg−1 at 0 and 25 °C, with high CO2/N2 selectivity (>38). The sample exhibited rapid CO2 uptake in 5 min and efficient regeneration after 20 adsorption–desorption cycles. Sample 0.3H3 developed large mesoporosity and a high surface area of 1217 m2g−1 with less than 3 min of treatment. The maximum dye removal was 281 mgg−1 and adsorption mechanisms involved diffusion into the mesoporous matrix, electrostatic interactions, H-bonding between AC and MB acid groups, and π–π interactions. The experimental data best fitted the Freundlich model. The results confirmed that microwaves have the potential to convert waste to micro-mesoporous ACs that can be used for a wide range of applications with significant processing time reductions and superior product qualities compared to conventional technologies.

Bamboo and coconut shell based activated carbon: A Raman spectroscopic study

In this paper, we present a detailed report on Raman spectroscopic analysis of activated carbon (AC) samples obtained from two different biomass sources, namely, bamboo and coconut shell. The detailed analysis revealed that the local structure of the precursors was affected differently by the physical and chemical treatments prior to the preparation of AC. This leads to different structural features of the derived AC samples though processed under similar conditions. The influence of preparation methods and temperature on modifications in the D-, G-, and 2D-peak parameters of bamboo and coconut shell based AC (BAC and CSAC) such as peak positions, peak widths and peak intensity ratio were thoroughly described. We experimentally validate the stage-two of the three-stage Ferrari-Robertson phenomenological model of amorphous carbon for these biomass derived AC. We also show that the observed anomalies in the peak parameters are consistent with the stage-two process combined with the networking properties of biomass derived AC. Physically activated BAC and chemically activated CSAC prepared at a temperature of 600 °C showed greater disorder (ID/IG) values of 1.37 and 1.22 in their AC structures, respectively. Further analysis of 2D-peak indicated the greater turbostratic disorder (quasi 2D-continuous random network) in BAC compared to CSAC.

Activated carbon from waste fabrics as a catalyst for NaBH4 methanolysis

Hydrogen energy is attractive as a sustainable and clean energy. Chemical hydrides are being studied as a solution to the transportation and storage problems of hydrogen. Hydrogen can be produced by methanolysis reaction of sodium borohydride on a suitable catalyst. For this purpose, metal catalysts with high catalytic activity are generally used. Despite their high catalytic activity, the environmental impact and cost of metal-containing catalysts has led to increased interest in synthesizing metal-free catalysts. Activated carbons are advantageous materials for metal-free catalyst applications. In recent years, industrial wastes have attracted much attention for the synthesis of sustainable materials for activated carbon preparation. In this study, activated carbons are produced from waste fabrics by chemical activation method using H3PO4 and KOH chemical agents at different impregnation ratios (1:1, 2:1 and 3:1 % w:w) and different carbonization temperatures (400, 500, 600°C for H3PO4 and 600, 700, 800°C for KOH). These carbons are used as catalysts for hydrogen production and their catalytic activity is evaluated based on hydrogen generation rate (HGR). Therefore, the effect of different conditions used in the preparation of activated carbon was investigated to determine its impact on HGR. The increase in carbonization temperature decreases the HGR value of the catalyst. The increase in acid concentration increases the HGR value. The highest HGR value is obtained as 39600 mL/(min.gcat) with YKK1–800 activated carbon. Once the carbon with high activity is identified, the effect of reaction conditions such as NaBH4, methanol, catalyst amount, and temperature on HGR is investigated. The catalytic activities of the prepared activated carbons in NaBH4 electrooxidation are also investigated. YKK3–700 activated carbon shows the highest catalytic activity at 1.91 mA/cm2 at −0.63 V peak potential. This result is promising for the use of metal-free catalysts for direct sodium borohydride fuel cells.

Activated carbons from open air and microwave-assisted impregnation of cotton and neem husks efficiently decolorize neutral cotton oil

The decolorization of cottonseed oil with activated carbons (ACs) from neem and cotton husks has a dual interest: elimination of undesirable pigments in oil and valorization of the husks; by-products of neem and cottonseed processing, which would otherwise be dumped along riverbanks and farms causing environmental pollution. ACs were produced from neem and cottonseed husks after acid impregnation assisted by microwave heating and in ambient air for the decolorization of neutral cottonseed oil. The experimental data were analyzed by the intraparticle diffusion and the pseudo-second-order kinetic models as well as the Langmuir and Freundlich isotherm models. The method of impregnation and carbonization time had dramatic effects on the specific surface area (800–1500 g/m2), the quantity of burn-off (50–70 %), and methylene blue index (300–5000 mg/g) values which indicated the potential of the prepared activated carbons in the bleaching of vegetable oil and in other applications such as environmental clean-up and in agriculture. Pigment adsorption increased with temperature for all ACs indicating that the decolorization process was endothermic. The quantity of adsorbent equally had a significant effect on the pigment adsorption process for all ACs. All the activated carbons prepared in this work were 30–80 % more efficient in pigment adsorption than bleaching earth that is normally used in decolorizing neutral cotton seed oil in industries. All tested models are adequate to describe pigment adsorption by the ACs. Both methods of preparation of ACs were effective for oil decolorization, but microwave impregnation is more appealing because it requires only 1 h compared to 6 h for ambient air. Optimum decolorization conditions were 90 °C for 40min and adsorbent concentration of 2 %.

One-stage microwave-assisted activated carbon preparation from Langsat peel raw material for adsorption of iron, manganese and copper from acid mining waste

This study describes the efficacy of microwave technology for the preparation of an activated carbon from Lansium domesticum peel as an adsorbent to adsorb Fe, Cu, and Mn from acid mine waste. In contrast to the conventional pyrolytic carbonization technique, the described method demonstrated several unparalleled advantages, including superior energy efficiency and remarkably rapid processing. The reported microwave irradiation method was able readily to achieve a morphology and extensive surface area similar to that of a sample produced using the traditional pyrolytic carbonization method for 2 hours, and this was accomplished in just 10 minutes. The activated carbon obtained was characterized using SEM-EDX, BET-BJH, and proximate test and applied to adsorb metal ions from acid mine waste to evaluate the isothermal adsorption model. The best power for activated carbon production was 400 watts for 10 minutes, which met the requirements of ASTM D 4607 for determining the iodine value of activated carbon. Optimal mass for adsorbing Fe, Cu, and Mn from acid mine waste was 4 grams with the removal percentages of 94.08%, 83.69%, and 90.67%, respectively. BET surface area was 1367.0385 m2/g along with a BJH cumulative volume and an average pore diameter of 1.112 cm3/g and 2.25 nm, respectively. This suggests that it possesses mesoporous characteristics and adheres to the Langmuir model during the adsorption process, signifying monolayer adsorption. Meanwhile, kinetics followed the pseudo-second-order rate equation.

Preparation of sucrose-derived activated carbon in one pot with desirable hierarchically porous structure for efficient dyes removal

Sugar is an excellent raw material for activated carbon preparation because of its wide availability, sustainability, and low mineral content. Herein, we developed an easy method for preparing sucrose-derived activated carbon (SAC) with desirable hierarchically porous structures by combining the foaming of molten sucrose, dual-templating (K2C2O4·H2O and CaCO3), and sequential etching by dual-templating activators at elevated temperatures. As an adsorbent, SAC–800 has a high specific surface (1594 m2/g), with rich both micro- and mesopores (microsurface vs external surface area is 812 and 782 m2/g). As a result of its desirable hierarchically porous structures, it adsorbs dyes fast and efficiently, attributed to the rich specific surface area that favors adsorption capability and pore size distribution that affects mass transport and adsorption speed. The adsorption for Rhodamine B and Congo Red is spontaneous and endothermic process. The adsorption capacities reach 357 and 780 mg/g for Rhodamine B and Congo Red, respectively, while the rate constants for adsorption (ka) and desorption (kd) for Rhodamine B are 4.23 × 10–3 L/(mg·min) and 0.12 L/min, and 1.02 × 10–3 L/(mg·min) and 5.6 × 10–3 L/min for Congo Red. With the easy preparation procedure and the desirable hierarchically porous structures, sucrose-derived activated carbons are promising candidates for potential practical applications.

Optimized preparation of activated carbon with high porosities based on puck shells (Afrostyrax lepidophyllus) by response surface methodology and physico-chemical characterization.

From recent research, lignocellulosic materials assert themselves as good precursors for the manufacture of highly carbonaceous and porous materials. Hence, the perspective of this work is the preparation of the low-cost activated carbons (ACs) based on puck shells (Afrostyrax lepidophyllus) with a large surface area. To achieve this, chemical activation using phosphoric acid and sodium hydroxide as an activating agent was carried out. The response surface methodology through Box-Behnken design was used to optimize the preparation conditions. Box-Behnken design was used to optimize the preparation conditions. The factors whose influences have been studied are the concentration of activating agent (0.5-1.5 mol l-1), the carbonization temperature (300-500°C) and the residence time (30-100 min). The AC obtained by phosphoric acid was named CRP and impregnated with sodium hydroxide CRB. The ideal conditions for the preparation of the ACs obtained from the maximum iodine number (647.29 for CRP and 575.15 mg g-1 for CRB) were: 1.5 mol l-1 for the concentration of activating agent at a carbonization temperature of 500°C during 62 min for CRP and 0.85 mol l-1 for the concentration of activating agent at a carbonization temperature of 500°C during 59 min for CRB. These two materials prepared were characterized by several techniques pH at the point of zero charge (pHpzc), Boehm titration, Fourier transform infrared spectroscopy, XRD analysis, BET method, Raman spectroscopy and scanning electron microscopy, which confirmed the acidic nature of CRP and the basic nature of CRB carbons. The specific surface of the micropores was 509.05 and 27.53 m2 g-1, respectively. It provides a new valorization of agricultural waste for the preparation of effective-cost microporous ACs as an adsorbent that can be applied in water treatment industries.

ADSORPTION OF DEEP RED ON AC PREPARED FROM CHESTNUT SHELL

Adsorption of Deep Red (DR) on activated carbon (AC) produced from chestnut shell has been studied. Chemical activation process with ZnCl2 was applied to the ground chestnut shells at 3:1 (ZnCl2/Raw Material) impregnation ratio, and then at 500 °C, the carbonization process was used to produce AC. The surface area of the AC was defined as 2187 m2/g. Effects of AC dose, contact time, pH, temperature and initial concentration on deepred adsorption have been studied. In experimental studies, 97.4% dye removal was achieved using 0.1 g AC at pH 2.5, 45°C and at 100 mg/L. Dye removal has been seen to increase at all initial concentrations as the temperature increased. The kinetic data are corresponding to the pseudo 2nd order kinetic model. The finding was that the adsorption process corresponding to the Freundlich isotherm model. According to ΔS, ΔH, and ΔG thermodynamic data, DR adsorption on AC is an endothermic and chemical adsorption. The study’s findings revealed that AC prepared from chestnut shell is suitable for removing DR from aqueous solutions.

Preparation of activated carbon based on synthetic and agricultural wastes: application to the adsorption of methyl orange

This study focus on the optimization of operating conditions for activated carbons preparation starting from synthetic waste (tires) and agricultural waste (date pits) by chemical activation. The experimental design was used in order to determinate the optimal conditions for the preparation of a precursor with high properties. The results show that a temperature of 550°C and particle diameter of 800 um are interesting. The specific surface area reached 770 and 1030m2/g respectively for the active carbons obtained from tires and date pits. In order to evaluate the efficiency of these adsorbents, we selected an anionic dye (orange methyl) as a pollutant. Kinetic results show that the adsorption equilibrium is reached at around 60 min with an adsorbed amount of 21.42 mg/ g and 38.83 mg/g for the TAC (Tire Activated Carbon) and the DPAC (Date Pits Activated Carbon) respectively. The different isotherms were well fitting by Freundlich model.

Impact of inherent calcium in coal on the structure and performance of activated carbon in flue gas activation: The enhanced mechanism of calcite on the methylene blue adsorption

To investigate the correlation and mechanism of inherent calcium species in coal on the preparation and performance of activated carbon (AC) when using flue gas activation. In this study, XCaCO3/AC (X means calcite contents in coal, 0–8 wt.%) was successfully produced by mixing different contents of calcite and demineralized Taixi coal and then using flue gas activation. The textual evolution and methylene blue (MB) removal of AC were conducted by a series of characterizations and tests, and revealed its mechanism. Coal with a high content of calcium could result in a low yield of AC. Calcite could transform into calcium oxide. During AC preparation by flue gas activation, calcium oxide also could react with CO2 and transform into calcium carbonate. Calcite in coal reduced the degree of AC's graphitization. The calcite in coal promotes the increment of CO, COO, and π-π* of AC linearly as the calcite content increases. Due to the excessive catalytic effect of calcite, high-content calcium could result in inferior porosity through promoting the collapse of pore topology. Calcite in coal strengthens the methylene blue (MB) removal capacity of AC. The 5CaCO3/AC possesses the utmost MB adsorption capacity, up to 118.8 mg/g, which is higher by 122.9% than AC of 53.3 mg/g. The various kinetics models were also verified and data was well matched to Pseudo second-order kinetics (R2=0.9165 for AC and R2=9729 for 3CaCO3/AC). Calcite in coal increases the content of CO and π–π* of AC, which strengthens chemical adsorption by functional groups complexation and π–π* stacking. Meanwhile, the existence of calcium species, OH− and CO32− is beneficial for ion exchange and complexation, respectively. Thus, the removal ability of MB by AC is enhanced. The results of this investigation could cast novel light on the high-performance AC design by utilization of high-calcium coal, and further multiple pollutants treatment.

Novel insight into the behavior of carbon in the positive active material of the lead-acid battery

Low-cost wood sawdust was investigated as a primary source for preparing active carbon to enhance the lead-acid battery. This can give a scope to determine the suitable active functional groups required to develop that battery. The fraction, −1.0 mm in size, was a potential feedstock for the active carbon preparation using phosphoric acid activation. The resulting precursor/H3PO4 mixture was pre-activated by solidifying at 150 °C for 2 h to eliminate water, leaving it a black adhesive solid. The hardened mixture was heated at 450 °C for an hour at a rate of 10 °C min−1 to complete the carbonization process. The produced active carbon was washed repeatedly with deionized water, dried at 105 °C, and saved in plastic for analysis and use, it was called (oxid-AC). The resulting active carbon has been identified using different analytical methods such as; XRD, SEM, FTIR, and BET. Results obtained revealed that the activated carbon additive, with a 2.5 % weight percentage, can reduce effectively the accumulation of PbSO4 at the positive active material (PAM) of the lead-acid battery. The role of the active carbon in improving the PAM behavior can be explained based on lead (II) ion adsorption on the carbon surface.

Pyrolyzed mesoporous activated carbon preparation from natural rubber common effluent biosludge: Characterization, isotherms, kinetics, thermodynamics, and ANN modeling during phenol adsorption

In the current research, a natural rubber common effluent biosludge (NRCEBS) was utilized for the first time to prepare activated carbon (NRCEAC) as a prominent adsorbent for removing phenol from aqueous solutions. FTIR, XRD, EDS, FESEM, BET, and AAS were used to characterize both NRCEBS and NRCEAC. As per BET results, the prepared adsorbent (NRCEAC) has a specific surface area of 52.52 m2/g. Batch adsorption studies were performed by varying initial concentration (10–60 mg/L), pH (1–12), NRCEAC dosage (2–25 g/L), temperature (20–50 °C), and adsorption time (15–300 min). The optimal value of adsorption operating parameters including pH, initial concentration, adsorbent dosage, and contact time were identified to be 6, 10 mg/L, 20 g/L, and 300 min, respectively. The highest phenol removal efficiency was reported to be around 86%. In addition, the maximum adsorption capacity of NRCEAC was estimated to be 1.142 mg/g. The adsorption outcomes were evaluated through the implementation of different kinetic, isotherm, and thermodynamic models. Nonlinear plotting and statistical analysis showed that pseudo-second-order kinetic model and Liu isotherm are the best fitted with the experimental kinetic and equilibrium data. Weber-Morris diffusion model suggested that both intra-particle and external diffusions contribute to the adsorption mechanism. Findings of thermodynamic study exhibited the endothermic, spontaneous, and random nature of adsorption. Finally, artificial neural network (ANN) modeling has been successfully applied to predict the phenol removal efficiency using 5-8-1 arrangement. The findings (R2 = 0.9972 and MSE = 2.131) obtained from ANN model showed good alignment between predicted response with experimental data. The study suggests that the inexpensive, natural bio-adsorbent (NRCEAC) is suitable for phenol remediation in refineries and other associated chemical industries.

Optimization of Physical Activation Process by CO2 for Activated Carbon Preparation from Honduras Mahogany Pod Husk.

In this work, the Honduras Mahogany (Swietenia macropnylla King, SMK) seed husk was used as a novel biomass resource for producing activated carbon by physical activation. The texture characteristics and chemical characterization of resulting products were investigated in correlation with the process parameters. Based on the thermochemical properties of the SMK biomass, the process conditions were set to a rate of about 10 °C/min under nitrogen (N2) flow of 500 cm3/min heated to 500 °C, then switched to carbon dioxide (CO2) flow of 100 cm3/min in the specified activation conditions (i.e., temperature of 700-850 °C for holding times of 0-60 min). Our findings showed that the texture characteristics (i.e., surface area and pore volume) increased with an activation temperature increase from 700 to 800 °C for a holding time of 30 min but gradually decreased as the temperature increased thereafter. Similarly, the texture characteristics also indicated an increasing trend with the residence time extending from 0 min to 30 min but slightly decreased as the time was extended to 60 min. Therefore, the optimal activation conditions for producing SMK-based activated carbon should be set at 800 °C for a holding time of 30 min to obtain the maximal texture characteristics (i.e., BET surface area of 966 m2/g and total pore volume of 0.43 cm3/g). On the other hand, the chemical characteristics were analyzed by energy dispersive X-ray spectroscopy (EDS) and Fourier Transform infrared spectroscopy (FTIR), showing oxygen complexes contained on the hydrophilic surface of the resulting activated carbon.

Activated carbon obtained from coffee husk waste activated by CaCl2 as support of TiO2 for the enhanced photocatalytic degradation of Victoria Blue B dye

In this study, we demonstrated the viability of the production of activated carbon (AC) from coffee husk waste and their activation using CaCl2. In addition, the prepared AC was used as support for TiO2, and the TiO2/AC composite was employed as a photocatalyst in the Victoria Blue B (VBB) photodegradation. Specifically, the coffee husk was carbonized at 800 °C for 1 h and then activated with CaCl2 at 850 °C, varying the heating time by 0.5, 1, 2, and 4 h. The activated carbons (ACs) treated within 1 and 2 h presented the highest surface area and were used to support TiO2 prepared by the sol-gel method. The surface area did not decrease after dispersion, keeping about 700 m2.g−1, which suggested the uniform distribution of TiO2 onto the surface of the ACs, confirmed by SEM and TEM analysis. In addition, TEM analyses revealed a small particle size distribution of TiO2 nanoparticles (3.4 nm for TiO2/AC_1_350 and 4.8 nm for TiO2/AC_2_350), indicating that they do not have enough dimensions to block the AC pores structure. X-ray diffraction, TGA, and XPS analyses revealed the combination of TiO2 nanoparticles with AC, generating a hybrid material. The photocatalytic activity of the TiO2/AC composite is very fast, removing about 99 % of the VBB dye after 120 min of photocatalytic degradation. The recyclability of the TiO2/AC catalyst was also evaluated in three consecutive reactions, showing that the nanocomposite could be used for multiple degradations without a decrease in photocatalytic activity. Thus, this study proved the feasibility of using coffee husk wastes for AC preparation and its use as a photocatalyst in conjunction with TiO2.

Activated carbon with high mesopore ratio derived from waste Zanthoxylum bungeanum branches by KNO3-assisted H3PO4 staged activation for toluene adsorption.

Waste Zanthoxylum bungeanum branches were used to prepare activated carbon adsorbents with high mesopore ratio by H3PO4 staged activation method with adding KNO3 additive. The prepared activated carbon adsorbents were characterized by SEM, BET, FT-IR, and XRD. The adsorption properties of the prepared activated carbon adsorbents were evaluated by the toluene adsorption/desorption in air. The quasi-first-order, quasi-second-order, and Bangham models were used to fit the obtained toluene adsorption results. The oxidative etching of KNO3 additive improved the pore-forming ability of the H3PO4 activator to enhance the activation pore-forming effects of the selected biomass raw material. The secondary pore-forming effects of K atoms promoted the effective expansion of the pore diameter in the activated carbon preparation process to prepare activated carbon adsorbents with high mesopore proportion. The specific surface area and mesopore proportion of the activated carbon adsorbents prepared by adding KNO3 additive exceeded 1100 m2/g and 71.00%, respectively, and the toluene adsorption capacity exceeded 370.00 mg/g. The rich mesopore structures can effectively reduce the toluene mass transfer resistance, which can promote the corresponding activated carbon adsorbent to be regenerated by low-temperature (40 °C) thermal desorption. The toluene adsorption on the prepared activated carbon adsorbents includes surface adsorption and diffusion in pore structures, and the toluene adsorption mechanism is more consistent with the Bangham kinetic model.

A review on Activated Carbon Prepared from Agricultural Waste using Conventional and Microwave Activation

In the recent years the research on the activated carbon preparation from agro-waste and byproducts have been increased due to their potency for agro-waste elimination. This paper presents a literature review on the synthesis of activated carbon from agro-waste using microwave irradiation method for heating. The applicable approach is highlighted, as well as the effects of activation conditions including carbonization temperature, retention period, and impregnation ratio. The review reveals that the agricultural wastes heated using a chemical process and microwave energy can produce activated carbon with a surface area that is significantly higher than that using the conventional heating method.

Activated carbon preparation based on the direct molten-salt electro-reduction of CO2 and its performance for VOCs adsorption

The conversion of CO2 into activated carbon (AC) for the adsorption of volatile organic compounds (VOCs) is a green strategy to treat waste by waste. In this study, CO2 was converted into a series of mesopore-enriched AC (MS-AC500, MS-AC550, and MS-AC600) by molten salt (MS) electrochemical method under different temperatures, and the prepared adsorbents were employed for the rapid adsorption of VOCs. The results showed that MS-AC500, MS-AC550, and MS-AC600 had a rich internal pore structure with specific surface area and pore volume of 816.70, 1062.05, 1255.50 m2/g and 0.58, 0.73, 0.84 cm3/g, respectively. The pore structures and surface chemistry of the adsorbents were positively correlated with the adsorption capacity, the adsorption amounts of MS-AC500, MS-AC550, and MS-AC600 were 244.89, 306.38, 414.39 mg/g for toluene and 279.29, 366.19, 460.10 mg/g for chlorobenzene, respectively. The superior adsorption capacity for chlorobenzene is mainly because chlorobenzene is a polar molecule and the C-O bonds inside the adsorbents have an attractive effect on the unpaired electrons inside the polar molecule. Simulation of the adsorption process of the adsorbents confirmed that the adsorption of both toluene and chlorobenzene was a physical adsorption process. Moreover, the adsorption-desorption cycle of chlorobenzene was more stable than that of toluene, and the durability of the adsorbent was above 95% after 5 cycles. This study can remove VOCs while reducing CO2 greenhouse gas, providing a feasible green route to treat waste by waste.