Adsorption of sulfur dioxide onto activated carbons prepared from oil‐palm shells impregnated with potassium hydroxide

Adsorption of sulfur dioxide (SO₂), a gaseous pollutant, onto activated carbons prepared from oil‐palm shells pre‐treated with potassium hydroxide (KOH) impregnation was studied. Experimental results showed that SO₂ concentration and adsorption temperature affected significantly the amount of SO₂ adsorbed and the equilibrium time. However, sample particle sizes influenced the equilibrium time (due to effect of diffusion rate) only. Desorption at the same temperature of adsorption and a higher temperature of 200 °C confirmed the presence of chemisorption due to pre‐impregnation. Impregnation with different activation agents was found to have limited effect on the inorganic components of the sample. Compared with the activated carbon pre‐treated with 30% phosphoric acid (H₃PO₄) that had larger BET and micropore surface areas, the sample impregnated with 10% KOH had a higher adsorptive capacity for SO₂, which was closely related to the surface organic functional groups of the sample. In general, the activated carbon prepared from oil‐palm shell impregnated with KOH was more effective for SO₂ adsorption and its adsorptive capacity was comparable to some commercial activated carbons. © 2000 Society of Chemical Industry     

The effect of activation method on the properties of pecan shell‐activated carbons

Pecan shell chars were activated using steam, carbon dioxide (CO₂), or phosphoric acid (H₃PO₄) to produce granular activated carbons (GACs). The GACs were characterized for select physical, chemical and adsorption properties. Air oxidation of the GACs was used to increase copper ion (Cu²⁺) adsorption. BET surface areas of pecan carbons were equal to or greater than commercial GACs. Carbon dioxide activation favored microporosity, while the other activations increased both mesoporosity and microporosity. Bulk densities and particle attrition of the pecan shell GACs were generally similar to the commercial carbons. Air oxidation of steam‐and CO₂‐activated GACs increased copper ion adsorption, although not to the same extent as GACs made by H₃PO₄ activation. Copper ion adsorption and the amount of titratable functional groups greatly exceeded the values for the commercial GACs. Steam‐and CO₂‐activated pecan shell carbons were similar to but in some cases exceeded the ability of commercial GACs to remove certain organic compounds from water. GACs from pecan shells showed considerable commercial potential to remove metal ions and organic contaminants from water. © 1999 Society of Chemical Industry     

Adsorption of hydrogen sulphide (H2S) by activated carbons derived from oil-palm shell

Adsorption of hydrogen sulphide (H₂S) onto activated carbons derived from oil palm shell, an abundant solid waste from palm oil processing mills, by thermal or chemical activation method was investigated in this paper. Dynamic adsorption in a fixed bed configuration showed that the palm-shell activated carbons prepared by chemical activation (KOH or H₂SO₄ impregnation) performed better than the palm-shell activated carbon by thermal activation and a coconut-shell-based commercial activated carbon. Static equilibrium adsorption studies confirmed this experimental result. An intra-particle Knudsen diffusion model based on a Freundlich isotherm was developed for predicting the amount of H₂S adsorbed. Desorption tests at the same temperature as adsorption (298 K) and at an elevated temperature (473 K) were carried out to confirm the occurrence of chemisorption and oxidation of H₂S on the activated carbon. Surface chemistries of the palm-shell activated carbons were characterized by Fourier transform infrared spectroscopy and Boehm titration. It was found that uptaking H₂S onto the palm-shell activated carbons was due to different mechanisms, e.g. physisorption, chemisorption and/or H₂S oxidation, depending on the activation agent and activation method.     

Improvement of the structural and chemical properties of a commercial activated carbon for its application in electrochemical capacitors

The present paper shows that the performance of an inexpensive activated carbon used in electrochemical capacitors can be significantly enhanced by a simple treatment with KOH at 850 °C. The changes in the specific surface area, as well as in the surface chemistry, lead to high capacitance values, which provide a noticeable energy density.The KOH-treatment of a commercial activated carbon leads to highly pure carbons with effective surface areas in the range of 1300-1500 m² g⁻¹ and gravimetric capacitances as high as three times that of the raw carbon.For re-activated carbons, one obtains at low current density (50 mA g⁻¹) values of 200 F g⁻¹ in aqueous electrolytes (1M H₂SO₄ and 6M KOH) and around 150 F g⁻¹ in 1M (C₂H₅)₄NBF₄ in acetonitrile. Furthermore, the resulting carbons present an enhanced and stable performance for high charge/discharge load in organic and aqueous media.This work confirms the possibilities offered by immersion calorimetry on its own for the prediction of the specific capacitance of carbons in (C₂H₅)₄NBF₄/acetonitrile. On the other hand, it also shows the limitations of this technique to assess, with a good accuracy, the suitability of a carbon to be used as capacitor electrodes operating in aqueous electrolytes (H₂SO₄ and KOH).     

Removal of Pb2+, Cd2+, Fe3+, and Sr2+ from Aqueous Solution by Selected Activated Carbons Derived from Date Pits

Date pits (DP) are a huge solid waste in Egypt and are of little or no economic value and in fact present a disposal problem. The quantity of DP has been estimated at a million tons per year. DP have been used for the preparation of physically and chemically activated carbons. The raw materials were physically activated with steam or chemically by impregnation with 10% ferric chloride or calcium acetate. The present study deals with the factors affecting the uptake of (Pb²⁺, Cd²⁺, Fe³⁺, and Sr²⁺) as pollutants from aqueous solution using activated carbon developed from locally available material DP, by a one‐step steam pyrolysis in a batch mode. The effect of various factors—carbon type, carbon dosage, pH, initial concentration, and temperature on the adsorption capacity were quantitatively determined. The two equilibrium models, the Langmuir and Freundlich equations, were discussed. In this work, analyses and batch adsorption experiments have been carried out to characterize and understand the adsorption mechanism by modeling the adsorption kinetics. Concurrently removal of these cations from the aqueous medium were found to be affected by the presence of some anions, NO₃ ^?, CO₃ ^?2, SO₄ ^?2 and masking agents, oxalic acid, and EDTA in solution.     

Regeneration of activated carbon after contact with sulfuric acid solution

This study deal's with the feasible use of a commercial activated carbon in the uptake of H₂SO₄ from aqueous solution and with the regeneration of the spent product. Thermogravimetry TG and FT‐IR spectroscopy are used in the analysis of samples. The activated carbon is a very effective material for the uptake of H₂SO₄. Using a 9.0 mol dm⁻³ H₂SO₄ solution, the mass increase is 37.8 wt%. From the sample obtained, the H₂SO₄ can be removed largely either by heating at 250 °C for 2 h in a N₂ atmosphere or by washing thoroughly with distilled water for 24 h. The mass loss in both cases amounts to 33.6 wt%. The FT‐IR spectroscopy results indicate that the surface chemistry of the carbon is not affected, noticeably, at least, after its contact with the H₂SO₄ solution. The behavior of H₂SO₄ toward carbon is compared with that of HNO₃. © 2000 Society of Chemical Industry     

Activated carbon from cherry stones

Fruit stones constitute a significant waste disposal problem for the fruit-processing industry. High-quality activated carbon can be produced from waste cherry stones: the activated carbon is low in impurities and has an adsorption capacity that compares favorably with commercial activated carbons. Activation at 800°C in steam for 2–3 hours, following initial carbonization, produces an activated carbon in about 10% yield (by weight) of the initial cherry stone. The activated carbons produced have surface areas (CO₂ adsorption) as high as 1200 m²/g and CCl₄ numbers of 70–80. Activation in carbon dioxide requires higher temperatures (900°C) and gives a carbon of slightly lower activity. Carbon from the hull, or hard outer portion of the fruit stone, provides essentially all of the adsorption capacity; the inner kernel does not form a microporous material. The hull structure is dominated by 0.4-micron pores which facilitate access to internal microporosity. This structure requires that the carbon be ground to less than 75 micron particles to achieve reasonable adsorption rates.     

Effects of chemical modification of petroleum cokes on the properties of the resulting activated carbon

Activated carbons have been prepared from petroleum cokes by the combination of a chemical treatment with HClO₄ or H₂O₂ and a chemical activation with KOH at a constant KOH/coke ratio of 3/1. The influence of different chemical treatments on the properties of the activated carbon precursors and final carbons activated with KOH was invested by using XRD, FTIR, and BET techniques. XRD results indicated that the value of interplanar distance d₀₀₂ increased by chemical treatment and the disappearance of the peak corresponding to 0 0 2 faces correlated to high specific surface area. FTIR studies showed that chemical modification promoted the formation of surface oxygen functionalities. Significant effects on BET surface area, pore texture and iodine adsorption capacity were evidenced. The results show that chemical modification prior to activation dramatically increased the BET surface area and total pore volume of the resulting activated carbon. Modified petroleum coke based activated carbon with chemical activation had higher specific surface area (2336 m²/g) and better iodine adsorption value (1998 mg/g).     

Synthesis and characterization of activated carbon and bioactive adsorbent produced from paper mill sludge

Adsorption capacity and bioactivity of a novel mesoporous activated carbon (IIT Carbon) and bioactive (BAC_IIT) catalyst produced from papermill sludge were evaluated. Conversion of paper mill sludge to useful activated carbons and biocatalysts is a significant process since it reduces environmental problems associated with disposal of waste sludge, enhances wastewater treatment using carbons produced from industrial waste itself, and promotes conservation of the naturally available primary resources currently used to make activated carbons. Analysis was conducted using synthetic wastewater containing phenol and a commercially available activated carbon, sorbonorite 4 (used as reference carbon). Phenol removal was accomplished in batch and fluidized bed reactors containing mesoporous activated carbon, sorbonorite 4, and the produced bioactive catalysts. Isotherm adsorption data indicated that mesoporous activated carbon has a higher adsorption capacity and molecular surface coverage than sorbonorite 4 for phenol concentrations less than 10 mg/l. The mass transfer limitation was accounted for the lower adsorption capacity of the microporous carbon (sorbonorite 4) in dilute solutions. The fluidized bed reactor study, however, indicated similar but slightly lower phenol removal capability for the produced mesoporous carbon. While phenol removal efficiency of the carbons studied was in the range 65–70%, the produced bioactive catalysts were able to remove up to 97% of phenol during first few hours of operation. These results suggest that mesoporous carbon will feasibly be a good substitute for other commercially available activated carbons produced from natural resources, not only in physical adsorption processes, but also in fluidized bed bioreactors (FBB), used in biodegradation processes.     

Treating contaminated soil by conversion into carbonaceous adsorbents: an investigation of activation procedures

The well established activated carbon manufacturing process has been investigated as a novel treatment for contaminated soil from gaswork sites by converting it into a porous carbonaceous solid with adsorbent properties. Several activation methodologies were evaluated: CO₂, air, ZnCl₂, H₂SO₄, H₃PO₄, FeSO₄ and HNO₃. Thermal analysis of the soil provided information regarding appropriate carbonisation and activation conditions. Bulk samples were prepared using contaminated soil samples, with ZnCl₂ being found to be the most effective agent for the process, producing an adsorbent which possessed a BET surface area of 131m²g⁻¹. The aqueous adsorption ability of the soil carbons was studied using phenol and 4‐nitrophenol as representative micropollutant organic molecules. The Langmuir monolayer capacity of the ZnCl₂‐activated soil was found to be 0.12 mmg⁻¹ for phenol and 0.23 mmg⁻¹ for 4‐nitrophenol. © 2000 Society of Chemical Industry     

Licorice residue and Pistachio-nut shell mixture: A promising precursor for activated carbon

As a continuation of previous research concerning preparation of activated carbon from agricultural by-products, applying a mixture of two kinds of lignocellulosic by-products with complementary properties as the parent material is investigated. Two kinds of activated carbons are prepared by chemical activation of the parent mixture – including residues of licorice and pistachio-nut shells – with H₃PO₄ and ZnCl₂ solutions, separately. The produced activated carbons have the surface areas comparable to the commercial ones. The lower ash content, higher bulk density and surface area of mix-based activated carbons in comparison with licorice-based ones, and also the highest mercury adsorption capacity of the mix-based ones confirm that it would be possible to modify the properties of an activated carbon using several complementary raw materials. The comparison of mercury adsorption capacities among mixed-based and the commercial activated carbons reveals that mix-based ones are effective and economical adsorbents for industrial wastewater treatment.     

Preparation of activated carbon from paper mill sludge by KOH-activation

The purpose of this study is the preparation of activated carbon using paper mill sludge collected from biological wastewater treatment plant. The char produced from pyrolysis of paper mill sludge was chemically activated with potassium hydroxide. A systematic investigation of the effect of activation agent ratio, activation temperature and time on the properties of the char was carried out in a rotary kiln reactor. The chemically activated carbons were characterized by measuring iodine and methylene blue number and specific surface area. The activated carbon prepared from char of paper mill sludge in this study had maximum iodine and methylene blue number of 726.0 mg/g and 152.0 mg/g, and specific surface area of 1,002.0 m²/g, respectively. The result of estimation on adsorption capacities of metals, the Freundlich isotherms, yields a fairly good fit to the adsorption data, indicating a monolayer adsorption of metals onto activated carbon prepared from char of paper mill sludge using a potassium hydroxide as the activating agents.     

Direct oxidation of hydrogen sulphide to sulphur using impregnated activated carbon catalysts

Low concentrations of H₂S were directly oxidized to sulphur and small quantities of SO₂, over seven different activated carbons with or without impregnation. The effectiveness of virgin activated carbon was tested at 175°C, 700 kPa, and O₂/H₂S ratio with 5% greater than stoichiometry. The conversion of H₂S was 99.9 mol% with SO₂ production of 3–6%, for 360 min runtime for Fisher coconut shell activated carbon and 648 min for Envirotrol bituminous (EB) activated carbon. Then the activated carbons became deactivated due to deposition of sulphur on the surface. Under these conditions mesoporous activated carbons such as EB and Hydrodarco had the longest breakthrough time. The addition of 5.5 wt% ammonium iodide, potassium iodide and potassium carbonate individually to EB decreased the production of SO₂ while having minimal effect on the overall H₂S conversion. The addition of 5.5 wt% NH₄I decreased the average SO₂ production from 2.5% to 0.9%. The activation energy for the H₂S oxidation on the 5.5 wt% NH₄I on EB activated carbon was determined to be 40 kJ/mol.     

Preparation and characterization of mesoporous activated carbon from waste tires

Activated carbons were produced from waste tires and their characteristics were investigated. Rubber separated from waste tires was first carbonized at 500 °C in N₂ atmosphere. Next, the obtained chars were activated with steam at 850 °C. As a result, fairly mesoporous activated carbons with mesopore volumes and BET surface areas up to 1.09 cm³/g and 737 m²/g, respectively, were obtained. To further improve the porous properties of the activated carbons, the char was treated with 1 M HCl at room temperature for 1 day prior to steam activation. This treatment increased mesopore volumes and BET surface areas of the activated carbons up to 1.62 cm³/g and 1119 m²/g, respectively. Furthermore, adsorption characteristics of phenol and a dye, Black 5, on the activated carbon prepared via acid treatment were compared with those of a commercial activated carbon in the liquid phase. Although the prepared carbon had a larger micropore volume than the commercial carbon, it showed a slightly lower phenol adsorption capacity. On the other hand, the prepared carbon showed an obviously larger dye adsorption capacity than the commercial carbon, because of its larger mesopore volume.     

Dynamic adsorption on activated carbons of SO2 traces in air: I. Adsorption capacities

Sulphur dioxide is an atmospheric pollutant which, among numerous others, has to be eliminated by habitacle filters. Breakthrough curves of low concentration SO₂ streams through beds of activated carbons have been obtained. Two carbons were studied, an activated PAN fiber (CF) and a granulated activated carbon (CN) under SO₂ concentrations lower than 100 ppm. Carbon CN used ‘as received’ is able to trap SO₂ in air at concentrations as low as 2.5 ppm. At this concentration, the adsorption of SO₂ is essentially irreversible. The fraction of reversibly adsorbed SO₂ rapidly increases when SO₂ content in air increases from 2.5 to 100 ppm. As expected, the amounts of SO₂ adsorbed per gram of carbon are much smaller than in the case of high SO₂ contents in air (>1000 ppm). The presence of water in carbon micropores enhances both reversible and irreversible adsorption of SO₂. The reversibly adsorbed part is physisorbed while the irreversibly adsorbed part results in oxidation of SO₂ at the carbon surface. This oxidation was evidenced by TPD from carbon samples after adsorption. The mechanism of SO₂ adsorption is discussed in relation to the mechanisms proposed in literature for high SO₂ contents (>1000 ppm).     

Adsorption of Hg(II) ions from aqueous chloride solutions using powdered activated carbons

Activated carbons were developed from Casurina equisetifolia leaves, by chemically treating with sulfuric acid (1:1) or zinc chloride (25%), at low (425 °C) and high (825 °C) temperatures. The resulting powdered activated carbons were applied for removing mercuric ions from aqueous solution at different agitation times and mercuric ion concentrations. The equilibrium data fitted well the Langmuir adsorption isotherm. The Langmuir adsorption capacities were 12.3 and 20.3 mg g⁻¹ for low temperature carbons and 43.9 and 38.5 mg g⁻¹ for high temperature carbons impregnated with H₂SO₄ and ZnCl₂, respectively. Studies of the effects of carbon dosage, NaCl concentrations and solution pH values were carried out for the more effective, high temperature carbons. Increasing NaCl concentration resulted in a significant decrease in the adsorption efficiency. Adsorption was high from solutions with low and neutral pH values and lower for solutions with alkaline pH values for the high temperature carbons.     

Sorption of mercury by activated carbon in the presence of flue gas components

The purpose of the current study is to evaluate the mercury removal ability of F400 and Norit FGD activated carbons, through fixed bed adsorption tests at inert atmosphere (Hg° + N₂). Additionally, adsorption tests were realized on F400 activated carbon, in the presence of HCl, O₂, SO₂ and CO₂ in nitrogen flow. The obtained results, revealed that F400 activated carbon, with a high-developed micropore structure and increased BET area, exhibit larger Hg° adsorptive capacity compared to Norit. HCl and O₂, can strongly affect mercury adsorption, owing to heterogeneous oxidation and chemisorption reactions, which is in accordance with the assumptions of some researchers. Additionally, SO₂ presence enhances mercury adsorption, in contrast with the conclusions evaluated in other studies. The above result could be attributed to the possible formation of sulphur spaces on activated carbon surface and consist of a clarification for the role of SO₂ on mercury adsorption. On the contrary, the mercury adsorption efficiency of F400 activated carbon showed a decrease at about 25%, with increasing CO₂ concentration from 0 to 12%.     

SYNTHESIS OF ACTIVATED CARBON FROM JATROPHA SEED COAT AND APPLICATION TO ADSORPTION OF IODINE AND METHYLENE BLUE

This article provides evidence that jatropha seed coat residues can be used as a carbon source for preparing activated carbons that have good adsorption properties for iodine and methylene blue. Activated carbons were prepared using three different methods of activation, physical, chemical, and physico-chemical, for a range of activation temperatures (600°, 700°, 800°, and 900°C) and activation hold times (1, 2, and 3 h). The highest BET surface area (1479 m² g^?1) and the highest iodine adsorption (1511 mg g^?1) were obtained with physico-chemical activation at a temperature of 900°C and a hold time of 2 h. This activated carbon gave higher BET surface area and iodine adsorption than commercial activated carbon (1169.1 m² g^?1 and 1076 mg g^?1). The activated carbons prepared by physico-chemical activation at 900°C and 2 h were then tested for adsorption of methylene blue at a range of concentrations of methylene blue (100, 200, 300, 400, and 500 mg L^?1). It was found that a Langmuir isotherm gave a better fit (R ² = 0.999) to the observed adsorptions than a Freundlich isotherm (R ² = 0.884). For the adsorption kinetics, a pseudo-second-order model gave a better fit (R ² > 0.998, Δq _e  = 3.7%) than a pseudo-first-order model (R ² ≈ 0.95, Δq _e  = 85.6%). These results suggest that chemisorption is the rate-controlling step for the adsorption of methylene blue. The experimental results show that jatropha seed coat is a lignocellulosic waste precursor for preparation of activated carbon that is an alternative source for preparation of commercial-grade activated carbons.     

SO2 and NO selective adsorption properties of coal-based activated carbons

The aim of this paper is to study binary gas adsorption on the activated carbon in the fixed-bed reactor. Coal-based granular activated carbons can selectively adsorb SO₂ and NO. Physically adsorbed NO is replaced and desorbed by SO_2. Chemically adsorbed NO can promote the absorption of SO₂. The presence of SO₂ and NO can enhance the chemical adsorption of NO and SO₂, respectively. When the diameter of granular activated carbon decreases and the specific surface area increases, both the penetration time of the activated carbon bed and SO₂ removal efficiency increase. The whole removal efficiency of SO₂ is more than 99% in the penetration time, but the whole removal efficiency of NO is only 55% in the coexistence of SO₂ and NO. SO₂ adsorption capacity of HNO₃ dipped granular activated carbon is higher than that of non-treated one. The two experimental results are agree with each other.     

Indoor formaldehyde removal over CMK-3

The removal of formaldehyde at low concentrations is important in indoor air pollution research. In this study, mesoporous carbon with a large specific surface area was used for the adsorption of low-concentration indoor formaldehyde. A mesoporous carbon material, CMK-3, was synthesized using the nano-replication method. SBA-15 was used as a mesoporous template. The surface of CMK-3 was activated using a 2N H₂SO₄ solution and NH₃ gas to prepare CMK-3-H₂SO₄ and CMK-3-NH₃, respectively. The activated samples were characterized by N₂ adsorption-desorption, X-ray diffraction, and X-ray photoelectron spectroscopy. The formaldehyde adsorption performance of the mesoporous carbons was in the order of CMK-3-NH₃ > CMK-3-H₂SO₄ > CMK-3. The difference in the adsorption performance was explained by oxygen and nitrogen functional groups formed during the activation process and by the specific surface area and pore structure of mesoporous carbon.