Surface Functional Groups Of Activated Carbon Research Articles

Experimental study on modified fruit shell carbon for methane adsorption and decarbonization

Modification of activated carbon has the potential to improve its adsorption and separation capacity. Different concentrations of ammonia (6%, 9%, 12%, 15%) and treatment times (4 h, 6 h, 8 h, 10 h) were used to modify jujube shell carbon and coconut shell carbon in ultrasonic washing equipment. Biogas adsorption experiments were carried out with modified activated carbon to study the effect of adsorption and decarbonization on activated carbon surface functional groups. After modification, the surface alkaline functional groups of activated carbon increased, the acidic functional groups decreased, and the adsorption performance of CO2 was enhanced. In addition, the specific surface area and total pore volume of activated carbon decreased, the average pore size increased, and the degree of graphitization increased. In the experimental research range, under ultrasonic conditions, jujube shell carbon impregnated with 12% ammonia water for 4 h and coconut shell carbon impregnated with 9% ammonia water for 10 h had the best modification effect. The adsorption capacity for CO2 was 1.83 and 1.745 mmol/g, respectively, which increased by 0.8 mmol/g and 0.599 mmol/g, respectively, compared with the unmodified sample.

Removal of Pb(II) ion by activated carbon synthesised from Musa Acuminate stem waste: surface properties, kinetics, adsorption mechanism, and reusability

ABSTRACT We present the synthesis of Activated Carbon (AC) by pyrolysis of Banana (Musa Acuminate) Stem Waste (BSW), and the ability of obtained AC for adsorptive removal of Pb(II) ions from water. Importantly, pyrolysis was performed at 750°C for 2.0 h in the presence of high surface area producing chemical activators such as NaOH, LiOH, H3PO4, ZnCl2, and KOH. BET-surface areas of AC produced with activators NaOH, LiOH, H3PO4, ZnCl2, and KOH were determined to be 908, 1531, 1670, 2245, and 2485 m2 g−1, respectively. Pore volume ascending order was determined as 0.59 (NaOH) < 0.68 (LiOH) < 0.86 (H3PO4) < 0.97 (ZnCl2) <1.18 (KOH) cm3 g−1. SEM and TEM images revealed the porous nature of the ACs. ACs produced with H3PO4, ZnCl2, and KOH exhibit type I adsorption isotherms, indicating their microporous nature. ACs prepared with NaOH and LiOH exhibit type II adsorption isotherms, indicating their macroporous nature. X-ray diffraction, X-Ray photoelectron, and Raman spectroscopy analysis revealed the graphitic structure of ACs. Pb(II) ion adsorption onto ACs surface obeyed the Langmuir model. It was found that the Pb(II) adsorption capacities of the ACs produced with NaOH, LiOH, H3PO4, ZnCl2, and KOH as the chemical activators were 220, 283, 326, 329, and 435 mg g−1, respectively, at the optimised conditions (pH = 6.6, contact time = 100 min, [ACs] = 0.125 g L−1, at 30°C). The interaction between surface functional groups of ACs and Pb(II) ions was confirmed by X-Ray photoelectron and FT-Infrared spectroscopy. The negative values of ΔGo and ΔHo reveal that the Pb(II) ion adsorption onto the ACs surface is spontaneous and exothermic. The Pb(II) ion adsorption capacity increased with an increase in BET-SA and pore volume of ACs, with AC obtained from BSW with KOH exhibiting the highest adsorption capacity of 435 mg g−1. Thus, the study highlights BSW, agricultural biomass waste is a low-cost and abundantly available carbon precursor to synthesise potential AC adsorbent for water treatment.

Removal of ammonia and hydrogen sulfide from livestock farm by copper modified activated carbon

&lt;p&gt;Ammonia (NH3) and hydrogen sulfide (H2S), as the main odorous substances in waste gas from livestock farm, have attracted more attentions rescently since their adverse effects. To remove NH3 and H2S efficiently, high-pressure hydrothermal modification (HPHM), metal salt solution impregnation modification (MSIM), and HPHM combined with MSIM are used to modify the activated carbon (AC). Meanwhile, the pore structure and surface functional groups of AC and MAC absorbents are characterized by BET, FTIR and Boehm titration method. The adsorption performance of activated carbon (AC) and modified activated carbon (MAC) are compared. The effects of modification and operation conditions on the adsorption performance of MAC for NH3 and H2S are studied in detail. It was found that the optimal adsorption performance of MAC can be achieved by high-pressure hydrothermal modification (HPHM) followed by the metal salt solution impregnation modification (MSIM). With gas space velocity of 900 h-1 and total inlet concentration of 550-650 mg m-3 at 50 oC, the adsorption capacities of NH3 and H2S of GS270CuCl6010 are 24.17 mg g-1 and 26.20 mg g-1, respectively. The adsorption of NH3 and H2S by MAC is the result of both physical adsorption and chemical adsorption.&lt;/p&gt;&#x0D;

Enhanced electrochemical double-layer capacitive performance with CO2 plasma treatment on activated carbon prepared from pyrolysis of pistachio shells

This study reports an original approach based on the CO2 plasma treatment on modification of the chemical or physical properties of activated carbon(AC) from the pistachio shells as a waste for application as electrochemical double-layer capacitors(EDLC). In the AC production experiments, impregnation ratio, impregnation pre-treatment temperature, activation temperature and activation time are investigated. In the AC modification experiments with plasma treatment, the effects of plasma gases, plasma power and plasma time are performed. The results of the different conditions indicated that the structural properties of the obtained AC were significantly dependent on the plasma and pyrolysis parameters. The surface properties of the raw AC and plasma-treated AC (PTAC) with X-ray photoelectron spectroscopy (XPS), nitrogen adsorption technique, and scanning electron microscope (SEM) are characterized. Surface area values for the raw AC and PTAC are 768 and 1250 m2 g−1, respectively. A change in the peak positions and an increase in the percentage of oxygen of the AC treated with CO2 plasma were obtained from XPS results. After 15 min of CO2 plasma activation, a significant increase in the capacitance of up to about 141% was obtained as a 118.4 F g −1 compared to 49.98 F g −1 for untreated AC. The results show that the plasma treatment on the specific surface area and surface functional groups of AC has a significant impact.

Modification of Activated Carbon by the Basic Ionic Liquid [Bmim]OH: A Feasibility Study

AbstractThe large amount of dye wastewater requires efficient techniques, e.g., adsorption by activated carbon (AC), for removal of dyes to decrease water pollution. AC was modified by the basic ionic liquid 1‐butyl‐3‐methylimidazolium hydroxide. The surface functional groups of AC changed evidently as detected by Fourier transform infrared spectroscopy and Boehm titration. To evaluate the influence of functional group change on adsorption performance, AC and modified activated carbon (MAC) were employed to remove methylene blue. The results indicated an increase of adsorbance with lapse of contact time. The adsorption capability of AC was distinctly higher than that of MAC. From kinetic studies it follows that the pseudo‐second‐order kinetic model can well describe the adsorption process.

Preparation of Activated Carbons from Walnut Shell by Fast Activation with H3PO4: Influence of Fluidization of Particles

AbstractActivated carbons were produced from walnut shell by fast activation with H3PO4in a spouted bed, and the influence of particles fluidization had been investigated. Experimental results showed that walnut shell particles with higher H3PO4impregnation ratios would be agglomerated in spouted bed, and difficult to fluidize. Therefore, an amount of quartz sands were added to assist fluidization of H3PO4impregnated walnut shell particles. The BET surface area of activated carbon prepared under fluidization would be obviously increased with H3PO4impregnation ratio, reaching 1549.6 m2/g for the mass ratio of H3PO4to walnut shell particles of 2 and activation temperature of 700°C. Meanwhile, both of the micro- and meso- pore volumes were increased. In addition, fluidization of particles had very little influence on activated carbon surface functional groups forming. It was found that the activated carbons contained more carbonyl groups (C = O), carboxyl groups (COOH) and some P-containing functional group.

Activated carbon surface chemistry: Changes upon impregnation with Al(III), Fe(III) and Zn(II)-metal oxide catalyst precursors from NO3− aqueous solutions

Because of the relevance in heterogeneous catalysis, the changes produced in the surface chemistry of activated carbon (AC) upon impregnation with the Al3+, Fe3+ and Zn2+ ions from aqueous solution of NO3− salts at pH 2.91 for Al3+, 1.54 for Fe3+ and 5.16 for Zn2+ in two successive soaking and oven-drying steps are studied. The samples (A120, F120 and Z120) were analyzed in terms of elemental composition and by energy dispersive X-ray analysis (EDX), FT-IR spectroscopy, X-ray photoelectron spectroscopy (XPS), and measurement of pH of the point of zero charge (pHpzc). The process yield was 102wt% for A120, 114wt% for F120, and 103wt% for Z120. Chromene, pyrone and ether type structures are by far predominant in AC. The hydrolysis of metal ions markedly influences the pH of the impregnation solution and thereby the oxidation of surface functional groups of AC by O2 and NO3− dissolved in such a solution. The degree of AC oxidation is larger with the Fe3+ solution than with the Al3+ and Zn2+ solutions. Carboxylic acid groups for F120 and phenolic hydroxyl groups for Z120 and especially for A120 are formed from reducing structures of AC. The nitrogen content is higher by Z120>A120>F120>AC. pHpzc is 10.50 for AC, 5.20 for A120, 4.00 for F120 and 6.30 for Z120.

Effect of activated carbon surface functional groups on nano-lead electrodeposition and hydrogen evolution and its applications in lead-carbon batteries

The effect of activated carbon (AC) surface functional groups on the cycle performance of lead-carbon batteries was studied from hydrogen evolution and nano-lead electrodeposition on the surface of the AC. AC materials were modified by oxidation methods (hot air or acid treatment) to increase acidic groups and reduction processes (alkaline treatment or heat treatment in N2) to increase alkaline groups. The surface functional groups were characterized by X-ray photoelectron spectroscopy and Boehm titration method. We used cyclic voltammetry and a three-electrode system to prepare nano-lead deposits on the surface of the AC, and studied its influence on hydrogen evolution of AC. The results show that acidic groups are beneficial to lead electrodeposition. In addition, the lead deposits with high activity covering the surface of AC could inhibit hydrogen evolution and the irreversible sulfation in lead-carbon batteries, and then result in longer cycle life under High-rate Partial-state-of-Charge conditions.

Removal of potassium permanganate from water by modified carbonaceous materials

Potassium permanganate is commonly used in multidiscipline processes as a strong oxidizing agent for oxidative treatment of a great number of organic and inorganic compounds. In this work, a method is proposed for removal of KMnO4 from aqueous solutions and real water samples using treated and activated carbon (AC) sorbents with sulfuric acid. The potential applications of five modified AC sorbents for removal of KMnO4 were explored under different experimental controlling factors including pH, contact time, initial concentration of KMnO4, sorbent dosage, and competing ions by the batch equilibrium technique. The removal values of KMnO4 were found to be ≥99.56% in the examined solutions (pH 1.0–7.0). In pH 1.0–2.0, KMnO4 removal from aqueous solutions was found to proceed by an anion exchange and ion pair interaction mechanisms, while in pH ≥ 3.0–7.0, the uptake of KMnO4 was identified to take place by an initial surface reduction step for the formation of Mn(II) ion and followed by adsorption via a direct complex formation with the AC surface functional groups. The proposed method confirmed an efficient removal of ≥99% of residual KMnO4 from industrial wastewater, seawater, and drinking water in laboratory trials.

Synergistic Effect of Nitric Acid Modified and Cu(II)-Loaded Activated Carbon on Catalytic Ozonation

The surface properties and performance of activated carbon (AC) used for catalytic ozonation were investigated after nitric acid modification (N-AC) and Cu (II)-loaded (N-Cu-AC). The results showed that the nitric acid modification could increase the amount of surface functional groups of AC. As a result, the adsorption capacity and catalytic activity of AC could be improved. The surface functional groups and Cu (II)-loaded of N-Cu-AC showed a synergistic effect on catalytic ozonation, where the catalytic activity of Cu (II)-loaded was more stable. N-Cu-AC was an effective and reusable catalyst for catalytic ozonation. The highest TOC removal efficiency of 58.0% could be achieved when N-Cu-AC was used for 60 min-catalytic ozonation treatment of acid red 3R.

PH dependence of chlordecone adsorption on activated carbons and role of adsorbent physico-chemical properties

From the 1960s to the 1990s, the large-scale production of banana in the French West Indies required an intensive use of chlorinated pesticides, such as chlordecone (Kepone), resulting in the diffuse contamination of soil and surface waters in the banana-producing areas. For this reason, drinking water plants were equipped with filters containing commercial activated carbons, being one of the challenges to find local adsorbents for the sustainable management of water treatment plants. In this paper, the adsorption of chlordecone (CLD) on activated carbons (ACs) prepared from sugar cane bagasse is studied, aiming to understand the mechanism of CLD adsorption on the AC surface. First, textural, acido-basic and chemical characteristics of the ACs were determined by thermal desorption, X-ray photoelectron and Boëhm studies. Adsorption isotherms of CLD show that the adsorption capacity increases with the amount of carbon and acidic groups at the AC surface whereas basic groups, hydroxyl and ether groups are detrimental to adsorption. The adsorption capacity is maximized at a solution pH level equal to the pHpzc of the considered AC. From temperature programmed desorption studies, it is proposed that chlordecone adsorption mechanism onto ACs is mainly governed by interaction with carboxylic groups. These results were correlated to molecular modeling studies of CLD interactions with surface functional groups of AC. The models of preferential positions, corresponding to minimal value of association energy, of interactions between CLD and AC functional groups were obtained.

Effect of surface modification of activated carbon on its adsorption capacity for bromate

This study deals with bromate adsorption by using modified activated carbons (ACs), attempting to reveal the effect of different modification methods on bromate adsorption by performing kinetic and isotherm tests. Four carbon modification methods including thermal modification, HNO3 modification, H2O2 modification, and NaOH modification are applied. These modification methods change the porous structures and redistribute the surface functional groups of AC. The kinetic data have been analyzed using pseudo-second-order and intra-particle diffusion models, and the intra-particle diffusion model is found to be the best applicable model to describe the adsorption process. The isothermal test shows that the thermal and alkaline modified ACs, with lower acidic functional groups, present higher adsorption capacities, and there is a remarkable linear relationship between the maximum adsorption capacity and the proportion of the acidic groups. The presence of natural organic matters (NOM) lowers the capacities of these ACs in bromate adsorption, but the HNO3 modified AC was not as sensitive as other modified samples. The presence of other anions (NO3-, SO42-, Cl-) can reduce the bromate uptake and the selectivity order for the AC is NO3- > SO42- > Cl-.

Estimation of the influence of structural elements of activated carbons on the energetic components of adsorption

The general mechanisms for the adsorption of organic molecules on the surface of solids are well known for flat/smooth non-porous materials. They depend on low energy dispersive interactions (London–Van der Waals) responsible for reversible physical adsorption and specific forces of greater energy associated with dipolar or acid/base interactions. However in the case of activated carbons (ACs) the study of these mechanisms is considerably hindered by their microporosity. The pores increase the surface area considerably but impede the study of the surface itself. The comparative study of inverse gas chromatography (IGC) at infinite dilution and a capillary wetting method shows that the dispersive component of the surface energy is greatly influenced by the porosity. The specific adsorption forces liable to intervene in the adsorption of alkenes do not appear due to steric hindrance. However alcohols are better adsorbed than alkanes, even more so as the surface overlap increases. A method for estimating adsorption energy based on capillary wetting shows clearly that porosity is responsible for an increase in the dispersive adsorption energies and that the non-specific hydrophobic component is much more important than acid/base interactions susceptible to intervene with the surface functional groups of ACs.

Effect of water vapour on the porous structure of activated carbon from lignite

A Bulgarian lignite from the Chukurovo deposit was used to produce an activated carbon by one-step steam pyrolysis at 650 °C. The effects of the presence of water vapour on the yield and composition of the solid, liquid and gas products were investigated. The water vapour present during pyrolysis-activation contributes to distillation of low molecular weight products and reacts with the coal and the volatile products obtained during pyrolysis. These processes lead to an increase in the yield of liquid and gas products and a decrease in the solid yield. The resulting carbon is characterized by a more developed porous structure, a higher N 2 BET surface area and higher adsorption capacity for iodine and methylene blue compared to the solid product obtained after pyrolysis in an argon atmosphere. The concentration of the activated carbon surface functional groups is considerably higher than that of the char obtained by pyrolysis in an argon atmosphere under the same heating conditions.