Activated Carbon Samples Research Articles

Utilization of activated carbon as an additive for urea-formaldehyde resin in medium density fiberboard (MDF) manufacturing

In this study, the MDF sanding dust was examined as a precursor for synthesizing activated carbon (AC). For this purpose, MDF sanding dust was impregnated with KOH at two different weight ratios 1:0.50 and 1:1 (sanding dust/KOH). The process was done in one step at a temperature of 750 °C and a heating rate of 8 °C/min. The synthesized ACs at different content were added into urea-formaldehyde (UF) resin for medium density fiberboard (MDF) production. The laboratory MDF boards were produced using a hot press at a temperature of 190 °C and pressure of 40 MPa. The ACs content in UF resin was set at 0.25%, 0.50% and 1% based on the dry weight of the resin. The ACs were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The BET equation was used to determine the specific surface area of the AC samples. Water absorption, thickness swelling, internal bonding, flexural modulus and strength, and the formaldehyde emission from MDF boards were determined. The curing behavior of UF resins were evaluated using Differential Scanning Calorimetry (DSC). The results revealed that surface area and micropore volume of ACs increase with increasing KOH ratio; and the ACs exhibited three-dimensional porous network structures. The DSC results also showed that the ACs significantly increase the reaction enthalpy of UF resins. The addition of AC as an additive to UF resin significantly reduces formaldehyde release from MDF boards and improves their physical and mechanical properties.

An updated study on NO catalytic oxidation over activated carbon: The effect of pore structure and a dual-site mechanism

NO catalytic oxidation (NOCO) to NO2 is widely believed to be a fundamental step in selective catalytic reduction (SCR) over activated carbon (AC). Thus, the enhancement of NOCO over AC is significant. The effect of the pore structure on NOCO is discussed first. A series of microporous AC samples with various microporous surface areas were prepared, in which a strong positive correlation existed between NO conversion and the microporous surface area. With an increase in the microporous surface area, the NO conversion increased from 13.10% for MAC1 to 41.18% for MAC4. Concurrently, a hierarchical AC sample with an approximate hierarchy degree (the ratio of Vmes+mac to Vt) of 50% demonstrated higher NO conversion than microporous AC when the microporous surface areas were similar. HAC2 exhibited the largest NO conversion (51.58%). Therefore, the microporous surface area and degree of hierarchy are key factors that enhance NO conversion. NOCO has been demonstrated to be an O-enriched process. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) results revealed that carbonyl groups were generated during the NOCO process. Density functional theory calculations were then performed. Carbonaceous models with unsaturated C atom, carbonyl, and lactone groups were constructed, and the corresponding NOCO reaction paths were calculated. A dual-site NOCO mechanism was proposed by combining the experimental and calculation results. Two types of active sites existed: unsaturated C atoms and high-spin density C atoms that affected the kinetic and steady-state stages of NOCO, respectively. The total amount of high-spin density C atoms strongly depends on the microporous surface area. The study of NOCO was updated, which contributed to the preparation of highly efficient AC for NOCO.

Efficient removal of naproxen from aqueous solution by highly porous activated carbon produced from Grapetree (Plinia cauliflora) fruit peels

In this work, jabuticaba (Plinia cauliflora) fruit peels were pyrolyzed in the presence of zinc chloride to generate a novel porous adsorbent to remove naproxen (NPX) from aqueous solutions. The maximum adsorption capacity of the activated carbon for NPX was 167.03 mg g−1, achieved at 328 K. This remarkable result might be mainly assigned to the pore characteristics, such as high surface area (1033 m2 g−1) and large pore volume (0.520 cm3 g−1). The Langmuir model was the one that obtained the best values of statistical coefficients, indicating the occurrence of surface saturation. The adsorption process occurred spontaneously under endothermic conditions. The experimental adsorption kinetics was well described by the linear driving force model (qexp = 128.72 mg g−1; qpred = 130.80 mg g−1). The porous material showed high efficiency against a synthetic mixture containing various drugs and salts, removing 86.79%. Therefore, the activated carbon sample obtained from jabuticaba (Plinia cauliflora) fruit peels may be employed as an alternative adsorbent to treat wastewater-containing drugs effectively.

Preparation of eco-friendly adsorbent for enhancing CO2 adsorption capacity

ABSTRACT The aim of this study was to investigate the potential of adsorbent derived from agricultural by-product-based activated carbon (AC) functionalized by deep eutectic solvents (DESs) for CO2 capturing application. Three types of DES, namely Tetrabutylammonium Bromide (TBAB), Methyltriphenylphosphonium Bromide (MTPB), and Triethlyene Glycol (TEG) were synthesized and functionalized with AC using the impregnation method. The characteristics of the prepared adsorbents were analyzed, including the freezing/melting point, viscosity, surface morphology, elemental composition, and BET surface area. Following the characterization, the CO2 breakthrough adsorption analysis was performed in a packed-bed reactor. The results revealed that the modified AC with the combination of TBAB and TEG showed the maximum CO2 adsorption capacity of 16.5 mg/g compared to other adsorbents mixtures. The maximum adsorption capacity was achieved at a breakthrough time, temperature, gas flow rate and CO2 concentration of 11.5 minutes, 25◦C, 200 mL/min, and 10%, respectively. Furthermore, the adsorption process was thermodynamically favorable and spontaneous under exothermic reaction as indicated by the negative values of both the Gibbs free energy (∆G°) and enthalpy (∆H°). The regeneration evaluation also demonstrated that the modified AC sample was recyclable and reusable for more than nine cycles.

On charge distribution and storage in porous conductive carbon structure

The charge storage and distribution in a porous conductive carbon material, in the presence and absence of electrolyte, are studied using the Poisson-Nernst-Planck equations for the first time in the literature. By solving the Laplace equation, it is found that the charge distribution inside the pores is negligible in the absence of the electrolyte. In the presence of cations and anions of the electrolyte inside the pores, the charge distribution on the pore surfaces and ionic concentration gradients in the electrolyte are numerically evaluated by solving the Poisson-Nernst-Planck equations. The modelling results predict the classic electric double layer structure for meso‑ and larger pores. For smaller nano-level pores, however, the equations predict a structural shift from a classic electric double layer towards a near-uniform ion storage inside the pores, that is, a concentration of counter ions within pores. The accuracy level of the results is then analysed considering modified Poisson-Nernst-Planck equations, relative permittivity variations of the electrolyte, and the validity of the continuum assumption. The modelling predictions are experimentally tested by measuring the charge storage under different electrolyte concentrations in two activated carbon samples with different pore structure characteristics.

Thermophysical Characteristics of Novel Biomass-Derived Activated Carbon as a Function of Synthesis Parameters

Activated carbon signifies extensive carbonized materials of a high degree of porosity and has a wide range of applications. The porous and thermal properties of activated carbon (AC) are primarily dependent on the chosen raw material and synthesis conditions. In this article, the thermophysical properties of twelve waste biomass-derived AC samples are investigated and correlated. These AC samples are synthesized from mangrove and waste palm trunk. The samples are different in terms of carbonization temperature (500 and 600°C), activation temperature (600 to 900°C), and the mixing ratio (4 or 6) of the activation chemical, which is potassium hydroxide. The specific heat capacity of W-AC-C600-A900-K6 is found to have the lowest (0.843 to 1.14 kJ kg−1 K−1), and M-AC-C500-A900-K4 shows the highest (1.18 to 1.86 kJ kg−1 K−1) among the studied samples. Experimental data are fitted with the Green-Perry model with an error of less than 2%. This study also accounts for the comparison of specific heat capacity of studied samples and other adsorbents such as AC obtained from different precursors, silica gels, carbon-based consolidated composites, and metal-organic frameworks found in the literature. Moreover, this study gives the insight to synthesize high-quality AC from unknown biomass sources for a particular application.

Glycine functionalized activated carbon derived from navel orange peel for enhancement recovery of Gd(Ⅲ)

Glycine functionalized activated carbon adsorption material (NOPAC-GLY-X) was successfully prepared by one-step thermal decomposition using agricultural waste navel orange peel as a precursor. Through batch adsorption experiments, it is found that the adsorption performance of Gd(III) on activated carbon can be significantly enhanced by glycine modification. The adsorption isotherms of the NOPACs conform to the Langmuir isotherm model, and the maximum adsorption capacity of the activated carbon sample NOPAC-Gly-60 is approximately 48.5 mg/g. The Gd(III) adsorption capacity of navel orange peel activated carbon can be doubled after glycine modification, and the adsorption efficiency of gadolinium can reach 99% at pH = 7. The physicochemical properties of the prepared adsorbents were characterized by Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FTIR), elemental analysis (EA), and X-ray photoelectron spectroscopy (XPS). The characterization test shows that the specific surface area of the sample increases from 1121 to 1523 m2/g, and the ratio of (N + O)/C increases from 10.8% to 30.0% by the glycine modification. After five cycles of adsorption–desorption, the adsorption capacity can still be maintained at 88% of the initial capacity. NOPAC-GLY-60 has excellent adsorption selectivity for Gd(III). With the obvious advantages of simple synthesis steps and low cost, the activated carbon modification method adopted in this study has great application value in the field of rare earth adsorption and recovery.

Characteristics of activated carbon prepared from flax shive by NH4NO3 and NH4Cl activation

The thermogravimetric method was used to study one-stage pyrolysis of finely ground flax shive chemically activated by NH4NO3 (AN) and NH4Cl (NAC). Activated carbons (AC) were obtained and the chemical activation mechanism was determined. The morphology, surface area and pore size distribution of the AC samples were studied by the methods of scanning electron microscopy, low-temperature nitrogen adsorption, energy-dispersive X-ray spectroscopy and X-ray diffraction. The maximum methylene blue adsorption capacity of the obtained AC samples was determined. The optimal parameters of activated flax shive pyrolysis (temperature, time) required for obtaining AC with the maximum specific surface area and adsorption capacity were identified.

Activated Carbon from the Peelings of Cassava Tubers (Manihot esculenta) for the Removal of Nickel(II) Ions from Aqueous Solution

Activated carbons were obtained from the peelings of cassava tubers (Manihot esculenta) by chemical activation using potassium hydroxide and phosphoric acid at impregnation ratios of 2 : 1 and 1 : 1, respectively, at 400°C for batch adsorption of nickel(II) ions from aqueous solution. Characterization of activated carbon samples was achieved via proximate analysis, Fourier-transform infrared spectroscopy, pH of zero-point charge, Boehm method, elemental analysis, scanning electron microscopy, and iodine number determination for each adsorbent. The effects of pH, contact time, initial adsorbate concentration, and adsorbent dose were studied at 27°C in order to optimize the conditions for maximum adsorption. Equilibrium was attained after 40 minutes of contact of both materials with activating solutions. Maximum adsorption capacities of 41.15 mg/g for ACPH, 47.39 mg/g for ACPA, 35.34 mg/g for NIC, and 34.48 mg/g for RM, respectively, were obtained at pH = 4. Equilibrium data showed that the Langmuir model best described the adsorption process with R2 closed to unity, indicative of monolayer adsorption on a homogeneous surface. Kinetic studies showed that the adsorption process is controlled by the pseudo-second-order model. These results show that activated carbon prepared from cassava peelings constitutes an effective low-cost material for the treatment of wastewater containing nickel(II) ions.

A systematic preparation mechanism for directional regulation of pore structure in activated carbon including specific surface area and pore hierarchy

Currently, the simultaneous and directional regulation of specific surface area (SBET) and pore hierarchy (the percentage of mesoporous and macroporous volume to total pore volume, Vmes+mac/Vt) of activated carbon (AC) lacks a systematic preparation mechanism. In this study, AC samples were prepared from coconut husks, and the effect of carbonization methods, activation methods, and process parameters on the development of the pore structure were explored. N2 adsorption–desorption results indicated that AC samples prepared via conventional carbonization were microporous. Hierarchical AC samples were obtained by the combination of hydrothermal carbonization at 240 °C and physical activation. CaCl2 impregnation was found to be beneficial to the preparation of meso-/macroporous AC samples. Based on these results, a series of AC samples with typically varied pore hierarchies (18.05–76.73 %) with similar specific surface areas (∼450.0 m2 g−1) were obtained. AC samples with similar pore hierarchies and different specific surface areas were also prepared, including microporous AC (SBET: 330.5–761.4 m2 g−1; Vmes+mac/Vt: 12.21–14.06 %), hierarchical AC (SBET: 445.9–780.7 m2 g−1; Vmes+mac/Vt: 51.04–54.89 %), and meso-/macroporous AC samples (SBET: 371.1–516.0 m2 g−1; Vmes+mac/Vt: 67.39–75.25 %). A systematic preparation mechanism for the directional regulation of the pore structure of AC is proposed, which is significant for the preparation of high-efficiency AC for different applications.

Sequestration of Pb(II) from Aqueous Environment by Palm Kernel Shell Activated Carbon: Isotherm and Kinetic Analyses

In this work, activated carbons were produced by the thermochemical treatment of palm kernel shells with different activation time. The developed products (activated carbon samples) were described by their surface area, porosity, and applied for lead(II) ions separation from liquid phase. By prolonging the activation time beyond 2h, some of the micropores collapsed to form mesopores without causing a significant transformation in the surface area. The influences of solution pH, mass of biosorbents, concentration of Pb(II) ions, and temperature on the entrapment of lead(II) ions explored. Based on experimental outcome, the best-suited condition for the Pb(II) uptake was 0.13 g AC-4, 250 mg L-1 concentration, and pH 4. The Pb(II) entrapment process is thermodynamically exothermic and spontaneous. The adsorption data fit the Langmuir monolayer adsorption model, with 222 mg g-1 as maximum sorption capacity, and the Ho-second-order kinetics model suitably described the process rate.

Controlling the emissive pathways of carbon nanoparticles by selective surface functionalization

Environmental friendly and biocompatible fluorescent carbon nanoparticles (CNPs) show great potential for various applications. The functional groups on the surface of the NPs dramatically influence the absorption and emission characteristics of the particles. However, a conclusive emission mechanism of CNPs and the exact role of functional groups are still lacking. Herein, a systematic investigation has been carried out by quantifying the oxygen-based function groups (–OH, –CHO, –COOH, –CO, –COO) present on the surface of activated carbon (AC) nanoparticles to identify their role in the emission characteristics. AC samples, prepared by the activation process of green waste of mandarin peels, were subjected to further treatments to achieve different levels of surface functionality with oxygen containing functional groups such as carbonyl, carboxyl, phenol and lactone. Various characterization techniques were employed to identify and quantify the functional groups. A detailed emission study revealed the role of specific functional groups in the emission process. Our results suggests that various emissive pathways in CNPs can be controlled by selective surface functionalization. This study shows significant results, which could shed more light on the emission mechanism of CNPs and the pivotal role of surface functional groups.

Effect of pore size in activated carbon on the response characteristic of electric double layer capacitor

The effect of pore size on the response characteristic of an electric double layer capacitor (EDLC) was closely examined. A series of phenol-resin-based activated carbon (AC) samples was prepared as average pore size from 0.94 to 1.68 nm by KOH activation by varying the activation temperature and KOH/carbonized phenol-resin ratio. The impedance properties of pouch-type EDLC cells prepared using AC samples were evaluated by applying an alternating current at 3 V between 10 mHz and 100 kHz for confirming the response characteristic. The cell based on the AC with a largest pore size (1.68 nm) showed fast response frequency, and had a high dielectric relaxation time constant as calculated from the response frequency value. The AC with the largest pore size, which consisted of both micropores (>1 nm) and mesopores (2–4 nm), was confirmed to facilitate extremely low electrolyte-diffusion resistance during the formation of the electric double layer, implying that the large pores lead to fast and stable response frequency. The presented findings suggest that AC with a largest pore size as the electrode leads to superior capacitance and response frequency characteristics in the alternating current than those of an AC with a smaller pore size.

Taguchi-based process optimization for activation of agro-food waste biochar and performance test for dye adsorption

The optimization of process parameters for biochar activation is crucial for enhancing its surface area and adsorptive potentials. This work attempts to investigate the influence of activating agent (e.g., steam and KOH), temperature (700–900 °C) and activation time (60–120 min) using Taguchi L18 (21 × 32) experimental design for the activation of biochar derived from food waste and agricultural crop residues such as canola hull and oat hull. Among all the factors, activating agent and temperature influenced surface area considerably. KOH-assisted chemical activation of biochar at 800 °C for 90 min was found to be optimal with higher specific surface areas of 1760, 1718 and 1334 m2/g for food waste, canola hull and oat hull derived biochar, respectively. Finally, the comparative evaluation of the performances of biochar and activated carbon samples was achieved through the adsorption of common dyes such as methylene blue, methyl violet and rhodamine B. Activated carbon samples derived from food waste biochar and canola hull biochar exhibited a complete removal of methylene blue and methyl violet from model aqueous solution within 1–2 h of contact time at room temperature, whereas in case of rhodamine B only 91–94% removal was achieved.

Adsorption-Based Hydrogen Storage in Activated Carbons and Model Carbon Structures

The experimental data on hydrogen adsorption on five nanoporous activated carbons (ACs) of various origins measured over the temperature range of 303–363 K and pressures up to 20 MPa were compared with the predictions of hydrogen density in the slit-like pores of model carbon structures calculated by the Dubinin theory of volume filling of micropores. The highest amount of adsorbed hydrogen was found for the AC sample (ACS) prepared from a polymer mixture by KOH thermochemical activation, characterized by a biporous structure: 11.0 mmol/g at 16 MPa and 303 K. The greatest volumetric capacity over the entire range of temperature and pressure was demonstrated by the densest carbon adsorbent prepared from silicon carbide. The calculations of hydrogen density in the slit-like model pores revealed that the optimal hydrogen storage depended on the pore size, temperature, and pressure. The hydrogen adsorption capacity of the model structures exceeded the US Department of Energy (DOE) target value of 6.5 wt.% starting from 200 K and 20 MPa, whereas the most efficient carbon adsorbent ACS could achieve 7.5 wt.% only at extremely low temperatures. The initial differential molar isosteric heats of hydrogen adsorption in the studied activated carbons were in the range of 2.8–14 kJ/mol and varied during adsorption in a manner specific for each adsorbent.

Removal of Pb(II) ions from Tigris river wastewater in Mosul city by using modified commercial activated carbon

Background: The water pollution of Tigris river is considered the main increasing problem in Mosul city, Iraq. The divalent lead ions are direct or indirect toxic heavy metals ions contaminant confirmed as non-biodegradables and have a long half-life due to corrosions and sedimentation of these metal ions in storm sewer trunk mains, the critical issue is eliminating these heavy metal ions by treating wastewater via commercial activated carbon (CAC), which is the most effective used adsorbent in the adsorption process. Aim: This study aimed to eliminate divalent lead ions by treating wastewater using commercial activated carbon (CAC). Methodology: The surface of commercial activated carbon (CAC) was modified by using concentrated nitric acid. For this purpose, nitric acid in different concentrations (2, 4, 6, 8, and 10 M) and different temperatures (25, 50, 75, and 100( °C were used. Results and Discussion: The best results were observed at 50 °C in which it was used as a standard temperature. A 10 M nitric acid concentration was noticed as the best one. It could be observed that the high pore volume observed in modified activated carbon samples (estimated as the highest adsorption capacity towards iodine, using iodine number determination method) was (707.2 mg/g). This result was supported by methylene blue (190 mg/g). The modified activated carbon (MAC) at the chosen acid concentration was a useful filter to remove the methylene blue organic dye. The modified activated carbon (MAC) was used to adsorbed Pb2+ ions from the Mosul Tigris river wastewaters, the percentage of mean changed activated carbon (MAC) surface adsorption removal efficiency of divalent lead ions were increased by 219% compared with the commercial activated carbon (CAC). 1.1.1. Conclusions: Using the methods for iodine number, ash content, methylene blue and density determinations, it was proven that the excellent sorption properties, strong microporous structure, large pore volume, surface of the acidic character, and porosity are the most critical chemical characterization parameters

Co-pyrolysis of mixed date pits and olive stones: Identification of bio-oil and the production of activated carbon from bio-char

The essential objective of this investigation is to inspect the possibility of exploiting an equivalent blend of locally available bio-wastes, namely date pits (DP) and olive stones (OS), for the production of bio-oil (BO) and bio-char (BC) through thermal pyrolysis route in a semi-batch lab-scale reactor. The pyrolysis products yields from mixed (DP + OS) were optimized by tuning the experimental variables. Co-pyrolysis of mixed (DP + OS) exhibited the maximum output of liquid products (51.11 %, with a BO yield of 37.17 %) at 500 °C using feed particle size of 60 mesh for 80 min at 20 °C/min heating rate. For comparison, the pyrolysis of DP or OS at the previously obtained conditions was also achieved. The liquid products yield from the pyrolysis of DP was (52.30 %, with a BO yield of 31.0 %) compared to (46.0 %, with a BO yield of 24.55 %). FTIR spectroscopy, GC–MS, and elemental analysis were employed to analyze the BO from mixed (DP + OS). The GC–MS outcomes revealed that the produced BO contains phenols, high molecular mass acids, fatty acid esters, aromatics, and alcohols. The BC produced by the pyrolysis of mixed (DP + OS) at the typical pyrolysis conditions mentioned above was exploited to create active carbon (AC) by the optimized ZnCl2 activation method. The AC was identified by BET surface area, FTIR, FESEM, EDX, and XRD. Also, it was exploited to remove dibenzothiophene (DBT) from model gasoline and commercial gasoline. The maximum removal efficiency of DBT reached (90.01 %± 0.50) using 25 mL of 200 mg/L DBT solution employing (0.30 g) of the as-created AC at 50 °C for 80 min. The DBT adsorption results by the AC obeyed the Freundlich isotherm, and best fit the pseudo-first-order kinetic model. For comparison, the BC samples produced through the pyrolysis of DP and OS individually at the typical pyrolysis conditions were also utilized to create AC at the optimal conditions obtained to prepare the best AC sample from mixed (DP + OS) by the ZnCl2 activation method. The so-prepared AC samples were identified for their iodine number and morphology using FESEM technique. The AC samples produced from the BC from DP and OS have also implemented to eliminate DBT from model gasoline using the optimum conditions obtained previously.

Scalable activated carbon/graphene based supercapacitors with improved capacitance retention at high current densities.

Scalable, highly stable supercapacitor electrodes were developed from the mixture of a tea factory waste based activated carbon (AC) and a low-cost electrochemical exfoliated graphene (EEG). The hybrid electrodes showed notably enhanced stability at high current densities. The AC sample was prepared by chemical method and exposed to a further heat treatment to enhance electrochemical performance. Graphene used in the preparation of hybrid electrodes was obtained by direct electrochemical exfoliation of graphite in an aqueous solution. Detailed structural characterization of AC, EEG, and hybrid material was performed. The original electrochemical performances of AC and EEG were examined in button size cells using an aqueous electrolyte. The hybrid materials were prepared by mixing AC and EEG at different mass percentage ratios, and tested as supercapacitor electrodes under the same conditions. Capacitance stability of the electrodes developed from AC:EEG (70:30) at high currents increased by about 45% compared to the original AC. The highest gravimetric capacitance (110 F/g) was achieved by this hybrid electrode. The hybrid electrode was scaled up to the pouch size and tested using an organic electrolyte. The organic electrolyte was preferred for scaling up due to its wider voltage ranges. The pouch cell had a gravimetric capacitance of 85 F/g and exhibited as good performance as the coin cell in the organic electrolyte.

Activated Carbon from Bamboo and Banana Wood Fibers as Adsorbent Materials for the Removal of Oil Samples

Over the past years and present, the expanding number of oil spills occurrences has gotten an overwhelming chemical test to the marine or oceanic environment, and the environmental issues around the globe are becoming more problematic and more acute, be it oil spills or effluents caused by oil and gas or petrochemical industries. The main point of this current investigation is the synthesis of activated carbon (AC) from various agricultural waste materials, bamboo, and banana fibers, as one of the most promising methodologies or applications in treating oil spills constitutes high sorption capacity. The physicochemical feature of the synthesized AC samples was analyzed by FTIR spectra and N2 physisorption. More specifically, the AC samples derived from bamboo (BAMB-AC) at activation temperature 550 ℃ indicate the highest specific surface area (2,760.47 m2/g), and sorption capacity at 3.3678 g/g with the total pore volume, mesopore volume, external surface area being 3.364 cm3/g, 1.811 cm3/g, and 1,601.634 m2/g, respectively, and maximum oil sorption capacity at 4.418 g/g for BANA-AC with activation ratio 7:1 (H3PO4), and surface area at 2,172.234 m2/g.

Construction and experimental study of Langmuir model for multi-molecular layer adsorption of porous materials

In this paper, a Langmuir isothermal adsorption model was developed based on the assumption of multi-molecular layer adsorption, and then adsorption experiments were carried out using coconut shell activated carbon samples as adsorbent. The results showed that multi-molecular layer Langmuir isothermal adsorption model is more widely used than the traditional single-molecular layer Langmuir adsorption model, and it is also more simple, more intuitive and more standardized than the BET adsorption equation based on the multi-molecular layer adsorption assumption, and its application is more convenient.