活性炭的表面处理对二苯并噻吩催化氧化脱除的影响

将一种木质活性炭经过三种表面处理,即高锰酸钾稀硫酸溶液液相氧化、浓硝酸液相氧化和350℃低温气相氧化处理。实验所选活性炭及相应的表面改性炭使用氮气吸附和Boehm滴定分别进行了结构性质和表面化学表征。研究了所选活性炭和相应的表面改性炭催化过氧化氢氧化脱除二苯并噻吩（DBT）。实验结果表明,活性炭表面化学对二苯并噻吩的氧化脱除影响很大;炭表面化学对DBT吸附脱除的影响不同于对DBT氧化脱除的影响,表面酸性越强越有利于DBT的吸附;表面羰基能加速过氧化氢产生自由基,表面羰基量的增加明显有利于DBT的氧化脱除。活性炭经过热处理后,在二苯并噻吩的氧化脱除中催化活性明显增加,正辛烷溶液中硫的体积质量从0.556g·L-1降到0.009g·L-1。     

Synergistic effect of nitrogen and molybdenum on activated carbon matrix for selective adsorptive Desulfurization: Insights into surface chemistry modification

This study reports the synthesis of mesoporous metal-modified nitrogen doped activated carbon (AC-N-Mo) from date seeds by ZnCl₂ activation and its applicability for selective adsorptive desulfurization of dibenzothiophene (DBT). The AC-N-Mo exhibits higher adsorption capacity for DBT at 100 mg-S/L with the maximum removal percentage of 99.7 % corresponding to 19.94 mg-S/g at room temperature than the unmodified carbon with 17.96 mg-S/g despite its highest surface area and pore volume of 1027 m²g^?1 and 0.55 cm³g^?1 respectively. The adsorption capacity breakthrough follows the order AC-N-Mo > AC-Mo > AC > AC-N. Also, AC-N-Mo displays excellent selectivity in the presence of aromatics (toluene, naphthalene, and 1-methylisoquinoline). The enhancement in the DBT uptake capacities of AC-N-Mo is attributed to the synergistic effect of nitrogen heteroatom that aids the dispersion of molybdenum nanoparticles on carbon surface thereby improving its surface chemistry and promising textural characteristics. The kinetic studies showed that the DBT adsorption proceeds via pseudo-second order kinetics while the isotherm revealed that Langmuir fit the data more accurately for the adsorbents. The physical properties (surface area, pore volume, particle size, etc.) and chemical properties (carbon content, etc.) of as-prepared adsorbents namely; AC, AC-N, AC-N-Mo, and AC-Mo were characterized by N₂– physisorption, X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Spectroscopy/Energy Dispersive Spectroscopy (SEM/EDS), Raman Spectroscopy (RS), Fourier Transform Infrared Spectroscopy (FTIR) and Ammonia-Temperature-Programmed Desorption (NH₃-TPD).     

四氟硼酸改性活性炭的制备及其吸附脱除二苯并噻吩性能

采用浸渍法制备了四氟硼酸(HBF₄)改性活性炭,并研究了其对模拟油中二苯并噻吩(DBT)的吸附脱除性能。利用傅里叶红外光谱(FT-IR)、差示热分析仪(TG-DTA)、X射线光电子能谱(XPS)以及N₂吸附技术对吸附剂的表面态和孔结构进行了表征,考察了四氟硼酸浓度、热处理温度以及模拟油中DBT浓度对吸附脱硫效果的影响。结果表明,经质量分数0.5%的HBF₄溶液浸渍、140 ℃热处理后,在剂油比1:100条件下,活性炭的吸附容量为352 mg/g,较未改性活性炭提高了72.5%。     

Selective adsorption and removal ability of pine needle-based activated carbon towards Al(III) from La(III)

Rare earth elements are an important strategic resource. As one of the most valuable member, lanthanum plays a key role in lanthanide. However, trace Al(III) impurity in lanthanum materials can seriously damage the performance of lanthanum materials. In this paper, a nitrogen-containing activated carbon, AC-PN-700, was synthesized using pine needle as raw material and KOH as activator. The AC-PN-700 was characterized by surface area analyzer, elemental analysis and FT-IR. The adsorption and selective ability of AC-PN-700 towards Al(III) were investigated. The BET specific surface area of AC-PN-700 was 596.4 m².g^?1, and the average pore diameter was 2.7?nm. Depend on its large specific surface, well-developed internal pore structure and abundant nitrogen-containing functional groups, the AC-PN-700 possesses strong adsorption affinity and excellent recognition selectivity towards Al(III). The adsorption capacity of AC-PN-700 towards Al(III) could reach to 3.89?mg.g^?1, removal rate towards Al(III) was almost 100%, and relative selectivity coefficients with respect to La(III) is 9.5. The empirical Freundlich isotherm was found to describe well the equilibrium adsorption data. In addition, AC-PN-700 possesses better regeneration ability and reusability.     

Adsorption of phenol by oil-palm-shell activated carbons

Steam activated carbons from oil-palm shells were prepared and used in the adsorption of phenol. The activated carbon had a well-developed mesopore structure which accounted for 45% of the total pore volume. The BET surface area of the activated carbon was 1183 m²/g and a total pore volume of 0.69 cm³/g using N₂ adsorption at 77 K. The adsorption capacity of the activated carbon for phenol was 319 mg/g of adsorbent at 298 K. The adsorption isotherms could be described by both the Langmuir-Freundlich and the Langmuir equations. The adsorption kinetics consisted of a rapid initial uptake phase, followed by a slow approach to equilibrium. A new multipore model is proposed that takes into account of a concentration dependent surface diffusion coefficient within the particle. This model is an improvement to the traditional branched pore model. The theoretical concentration versus time curve generated by the proposed model fitted the experimental data for phenol adsorption reasonably well. Phenol adsorption tests were also carried out on a commercial activated carbon known as Calgon OLC Plus 12×30 and the agreement between these adsorption data and the proposed model was equally good.     

Preparation of Quercus mongolica leaf-derived porous carbon with a large specific surface area for highly effective removal of dye and antibiotic from water

Quercus mongolica leaf (QL), an easily available biomass, was used as the precursor for preparing the hierarchical porous carbon with a large specific surface area and high adsorption capacities toward the representative dye and antibiotic. After being carbonized, QL was further chemically activated, and potassium hydroxide was proved to be a better activator than sodium hydroxide. The QL-derived porous carbon (PCQL) exhibited abundant micro- and mesopores, and the specific surface area reached 3275 m² g^?1. The performances of PCQL were evaluated through adsorbing rhodamine B (RhB) and tetracycline hydrochloride (TC) from water. Four adsorption isotherm models (the Langmuir, Freundlich, Sips, and Redlich-Peterson models), three adsorption kinetic models (the pseudo-first-order, pseudo-second-order, and intra-particle diffusion models), and the thermodynamic equations were used to investigate the adsorption processes. The pseudo-second-order kinetic model and the Sips isotherm model fitted the experimental data well, which indicates that the adsorption processes were controlled by the amount of adsorption active sites on the surface of PCQL, and these adsorption active sites had different affinities for the adsorbates. The maximum adsorption capacities of PCQL toward RhB and TC were 1946.0 and 1479.6 mg g^?1, respectively, based on the Sips model. The thermodynamic analysis indicates that the adsorption of PCQL toward adsorbents was spontaneous physical processes accompanied by the increasing disorder degree. The adsorption mechanism was attributed to the combination of the pore-filling, hydrogen bond, and π-π interactions. Moreover, in the fixed-bed experiments, the Yoon-Nelson model fitted the breakthrough curves well, and about 8 L wastewater containing RhB (200 mg L^?1) may be effectively treated by 1.0 g of PCQL. Above results indicate that QL is a promising precursor for preparing functional porous carbon materials.     

Synthesis of Porous Material from Coal Gasification Fine Slag Residual Carbon and Its Application in Removal of Methylene Blue

A large amount of coal gasification slag is produced every year in China. However, most of the current disposal is into landfills, which causes serious harm to the environment. In this research, coal gasification fine slag residual carbon porous material (GFSA) was prepared using gasification fine slag foam flotation obtained carbon residue (GFSF) as raw material and an adsorbent to carry out an adsorption test on waste liquid containing methylene blue (MB). The effects of activation parameters (GFSF/KOH ratio mass ratio, activation temperature, and activation time) on the cation exchange capacity (CEC) of GFSA were investigated. The total specific surface area and pore volume of GSFA with the highest CEC were 574.02 m²/g and 0.467 cm³/g, respectively. The degree of pore formation had an important effect on CEC. The maximum adsorption capacity of GFSA on MB was 19.18 mg/g in the MB adsorption test. The effects of pH, adsorption time, amount of adsorbent, and initial MB concentration on adsorption efficiency were studied. Langmuir isotherm and quasi second-order kinetic model have a good fitting effect on the adsorption isotherm and kinetic model of MB.     

Removal of ronidazole and sulfamethoxazole from water solutions by adsorption on granular activated carbon: equilibrium and intraparticle diffusion mechanisms

The equilibrium and intraparticle diffusion of ronidazole (RNZ) and sulfamethoxazole (SMX) during the adsorption on granular activated carbon (GAC) from aqueous solution was investigated in this work. The solution pH, temperature, ionic strength and water matrix affected the adsorption capacity of GAC towards SMX, but no effect was observed for the adsorption of RNZ. This behavior was due to the different mechanism involved in the adsorption of both antibiotics. The adsorption capacity of GAC towards RNZ was greater than that towards SMX. Molecular computation allowed the estimation of the binding free energy and confirmed that the adsorption of RNZ was more favorable than the adsorption of SMX. The adsorption mechanism of both antibiotics is governed by π–π dispersive interactions, and molecular simulation demonstrated that the coulombic interactions did not affect, but the solvation and nonpolar interactions play a significant role on the adsorption of both antibiotics. The application of diffusional models revealed that the overall adsorption rate of both antibiotics is controlled by intraparticle diffusion. Moreover, the surface diffusion was more predominant than the pore volume diffusion. Besides, surface diffusion coefficient, D_s, for RNZ was not a function of the aqueous matrix, whereas D_s for SMX was highly dependent on the water matrix.     

Template-derived mesoporous carbons with highly dispersed transition metals as media for the reactive adsorption of dibenzothiophene

Mesoporous carbons with highly dispersed copper, cobalt, and iron were obtained from an organic polymer within amorphous silica powder, alumina, and zeolite 13X. The materials were characterized using the adsorption of nitrogen, potentiometric titration, and elemental analysis. The small metal content (less than 1%) and its chelation in the precursor polymers ensure a high dispersion of metallic centers. The materials obtained are mainly mesoporous but differ significantly in their porosity and surface chemistry, which is linked to the effect of template constraints and chemistry and the kind of metal and is related to the differences in the carbonization mechanism. On the carbon obtained, the adsorption of dibenzothiophene (DBT) from hexane was carried out. The high capacities (up to 130 mg S/g) obtained were linked to the high volume of mesopores and specific interactions of DBT with surface acidic groups and strong interactions of metals with dibenzothiophene via S-M sigma bonds or, in the case of copper, via interaction of metals with disturbed pi electrons of aromatic rings of DBT.     

Synthesis and characterization of MFe2O4 sulfur nanoadsorbents

Nanoparticles of ferrites (Fe₃O₄, NiFe₂O₄, CuFe₂O₄, and MnFe₂O₄) were prepared by a reverse (water/oil) microemulsion method. The microemulsion system consisted of cetyltrimethylammonium bromide, 1-butanol, cyclohexane, and a metal salt solution. The procedure was carried out using aqueous ammonia as the coprecipitating agent. Nanosized particles were characterized by thermal analysis, X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and pyridine adsorption. The NiFe₂O₄ sample exhibited narrow mesoporous pore size distribution and high surface area ≈233 m²/g. It achieved good adsorption activity towards the dibenzothiophene (DBT) compound (166.3 μmol/g of DBT adsorbent). The structural properties obtained were very interesting for potential applications in the desulfurization process in petroleum refining.     

Development and tailoring of amino-functionalized activated carbon based Cucumerupsi manni Naudin seed shells for the removal of nitrate ions from aqueous solution

The removal of nitrate ions with ethylenediamine (EDA)-functionalized activated carbon (AC-NH₂) was studied in this work. Activated carbon prepared from Cucumerupsi manni Naudin seed shells using ZnCl₂ (ACZ) was functionalized with EDA via a nitric acid oxidation followed by acyl chlorination and amidation process. The effect of pH, contact time, initial concentration and co-existing ions on the adsorption of nitrate ions have been investigated. The FTIR and elemental analysis revealed that amino groups were successfully grafted onto the ACZ after functionalization. The surface area and average pore of ACZ were found to be 1008.99 m²/g and 2.02 nm respectively. However, it was noticed that, after functionalization (AC-NH₂), its surface area decreases to 113.43 m²/g meanwhile, its pore diameter increases to 2.48 nm. The experimental results of adsorption showed that AC-NH₂ exhibit excellent nitrate ions uptake performance compared to ACZ which is attributed to the presence of the grafted amino groups on the ACZ. Nitrate adsorption follows pseudo-first-order kinetic model while the equilibrium adsorption data was best fitted the Freundlich isotherm suggesting that the adsorption process was predominated by physisorption. This study demonstrates that the prepared AC-NH₂ is a promising adsorbent for nitrate ions removal from aqueous media.     

Enhanced Adsorption of Hexavalent Chromium onto Magnetic Calcium Ferrite Nanoparticles: Kinetic,Isotherm, and Neural Network Modeling

Calcium ferrite nanoparticles with super-paramagnetic behavior were synthesized via simple chemical precipitation method for effective removal of hexavalent chromium from aqueous media. The properties of synthesized nanoparticles were studied by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), Fourier transform infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller (BET), and vibrating sample magnetometer (VSM) measurements. The ferrite nanoparticles have shown polycrystalline nature and high BET specific surface area (229.83 m²/g) with active functional groups on the surface. The adsorption process follows second-order kinetics with the involvement of intra-particle diffusion and adsorption capacity as much as 124.11 mg/g was determined from the Langmuir isotherm. The thermodynamic analysis revealed that the adsorption process was feasible, spontaneous, and exothermic in nature. A three-layer feed-forward back-propagation artificial neural network (ANN) model was employed to predict the removal (%) of Cr(VI) ions as output. Optimal ANN network (4:8:1) shows the minimum mean squared error (MSE) of 0.00161 and maximum coefficient of determination (R²) of 0.984. The adsorption process is mostly influenced by solution pH and followed by adsorbent dosage, initial Cr(VI) concentration, and contact time as illustrated by sensitivity analysis. With small size and high surface area, biocompatibility, ecofriendly nature, easy magnetic separation, and enhanced adsorption capacity towards Cr(VI), calcium ferrite nanoparticles will find its potential application in wastewater remediation.     

Brilliant Blue R Adsorption from Aqueous Solution on Activated Carbon Produced from Corncob Waste

Brilliant blue R adsorption from aqueous solution on activated carbon produced from corncob waste was investigated. The carbon samples were characterized by XRD, SEM, EDS and FTIR methods. The surface functional groups (carboxyl, lactone or phenol, ether, hydroxyl) disappeared at high activation temperature, resulting in a high amount of carbon with respect to oxygen. The kinetic studies of the adsorption of brilliant blue R on carbon at 10 and 45 °C showed that the first order and intraparticle diffusion models apply to the data. The reaction rate increased with the increase in temperature of adsorption/activation. Thermodynamic parameters like ΔE^#, ΔH^# and ΔS^# for adsorption were calculated from the kinetic data. The positive value of ΔH^# shows the endothermic nature of adsorption which decreased with the increase in adsorption/activation temperature. The negative values of ΔS^# reflect a decrease in the disorder of the system at the solid‐solution interface during adsorption. Equilibrium studies showed that the data fits the Langmuir model.     

Correlation between pore-expanding and dye adsorption of platelet C/SBA-15 prepared by carbonization and oxidation of P123-TMB/SBA-15 composites

Platelet SBA-15 with significantly shortened and larger mesopores were prepared with different dosage of trimethylbenzene (TMB) in the assembly process, and then functionalized with acidic oxygen groups by oxidation of carbon layer that obtained by carbonization of P123-TMB organic species occluded in the silica pores. The preparation procedure involved three steps, namely, (a) synthesis platelet SBA-15 with larger mesopores, (b) carbonization, using P123 in the pore directly as the carbon source, and (c) oxidation with K₂S₂O₈. The resulting oxidation and carbonization of platelet SBA-15 (CST-ox, where C = carbon, S = SBA-15, T = trimethylbenzene, and ox refers to oxidation) composites contained of carbonaceous matter with acid oxygen groups (e.g. –COOH, –C=O and –OH) attached onto the deposited carbon layer. The structural characteristics of the parent silica were retained in the oxidized composite materials, which exhibit high surface area, large pore volume and well-ordered porosity. The oxygen-functionalized CST-ox composites with larger mesopores were found to be excellent adsorbents towards methylene blue. Especially, the adsorption equilibrium time was significantly reduced from 60 to 20 min, and the maximum adsorption capacity was increased from 379 to 420 mg/L, for which may be closely associated with the larger pore size, highly shortened meso-channels and the functionalized carbon layers. The adsorption kinetic data were analysed using pseudo-first-order, pseudo-second-order and Weber’s intraparticle diffusion models. Also equilibrium data were fitted to the Langmuir, Freundlich isotherm models and isotherm constants were determined. Thermodynamic parameters such as changes in the free energy of adsorption (ΔG ⁰), enthalpy (ΔH ⁰) and entropy (ΔS ⁰) were calculated.     

Production of low sulfur diesel fuel via adsorption: an equilibrium and kinetic study on the adsorption of dibenzothiophene onto NaY zeolite

The adsorption of dibenzothiophene (DBT) in hexadecane onto NaY zeolite has been studied by performing equilibrium and kinetic adsorption experiments. The influence of several variables such as contact time, initial concentration of DBT and temperature on the adsorption has been investigated. The results show that the isothermal equilibrium can be represented by the Langmuir equation. The maximum adsorption capacity at different temperatures and the corresponding Langmuir constant (K _L ) have been deduced. The thermodynamic parameters (ΔG ⁰,ΔH ⁰,ΔS ⁰) for the adsorption of DBT have also been calculated from the temperature dependence of K _L using the van’t Hoff equation. The value of ΔH ⁰,ΔS ⁰ are found to be −30.3 kJ mol⁻¹ and −33.2 J mol⁻¹ K⁻¹ respectively. The adsorption is spontaneous and exothermic. The kinetics for the adsorption process can be described by either the Langmuir model or a pseudo-second-order model. It is found that the adsorption capacity and the initial rate of adsorption are dependent on contact time, temperature and the initial DBT concentration. The low apparent activation energy (12.4 kJ mol⁻¹) indicates that adsorption has a low potential barrier suggesting a mass transfer controlled process. In addition, the competitive adsorption between DBT, naphthalene and quinoline on NaY was also investigated.     

Adsorption of Volatile Organic Compounds (VOCs) on Oxygen-rich Porous Carbon Materials Obtained from Glucose/Potassium Oxalate

To investigate the effects of oxygen-containing functional groups on the adsorption of volatile organic compounds (VOCs) with different polarity, oxygen-rich porous carbon materials (OPCs) were synthesized by heat treatment of glucose/potassium oxalate material. The carbon material had a large specific surface area (1697 m² g⁻¹) and a high oxygen content (18.95 at.%). OPC exhibited high adsorption capacity of toluene (309 mg g⁻¹) and methanol (447 mg g⁻¹). The specific surface area and total pore volume determined the adsorption capacity of toluene and methanol at the high-pressure range, while the oxygen-containing groups became the main factor affecting the methanol adsorption at the low-pressure range due to the hydrogen bond interaction through the density functional theory (DFT) calculations. This study provides an important hint for developing a novel O-doped adsorbent for the VOCs adsorption applications and analyzing the role of oxygen-containing groups in the VOCs adsorption under the low-pressure range.     

The Use of High Surface Area Mesoporous-Activated Carbon from Longan Seed Biomass for Increasing Capacity and Kinetics of Methylene Blue Adsorption from Aqueous Solution

Microporous- and mesoporous-activated carbons were produced from longan seed biomass through physical activation with CO₂ under the same activation conditions of time and temperature. The specially prepared mesoporous carbon showed the maximum porous properties with the specific surface area of 1773 m²/g and mesopore volume of 0.474 cm³/g which accounts for 44.1% of the total pore volume. These activated carbons were utilized as porous adsorbents for the removal of methylene blue (MB) from an aqueous solution and their effectiveness was evaluated for both the adsorption kinetics and capacity. The adsorption kinetic data of MB were analyzed by the pseudo-first-order model, the pseudo-second-order model, and the pore-diffusion model equations. It was found that the adsorption kinetic behavior for all carbons tested was best described by the pseudo-second-order model. The effective pore diffusivity (D_e) derived from the pore-diffusion model had the values of 4.657 × 10⁻⁷–6.014 × 10⁻⁷ cm²/s and 4.668 × 10⁻⁷–19.920 × 10⁻⁷ cm²/s for the microporous- and mesoporous-activated carbons, respectively. Three well-known adsorption models, namely the Langmuir, Freundlich and Redlich–Peterson equations were tested with the experimental MB adsorption isotherms, and the results showed that the Redlich–Peterson model provided the overall best fitting of the isotherm data. In addition, the maximum capacity for MB adsorption of 1000 mg/g was achieved with the mesoporous carbon having the largest surface area and pore volume. The initial pH of MB solution had virtually no effect on the adsorption capacity and removal efficiency of the methylene blue dye. Increasing temperature over the range from 35 to 55 °C increased the adsorption of methylene blue, presumably caused by the increase in the diffusion rate of methylene blue to the adsorption sites that could promote the interaction frequency between the adsorbent surface and the adsorbate molecules. Overall, the high surface area mesoporous carbon was superior to the microporous carbon in view of the adsorption kinetics and capacity, when both carbons were used for the removal of MB from an aqueous solution.     

Characteristics of granular boehmite and its ability to adsorb phosphate from aqueous solution

In this study, we investigated the surface properties of granulated boehmite with vinyl acetate (G-BE20) and measured the amount of phosphate it adsorbed and the effect of contact time and solution pH on the adsorption process. The specific surface area (144.9?m²/g) and the number of surface hydroxyl groups (0.88?mmol/g) of G-BE20 were smaller than those of virgin boehmite (BE), which gave a specific surface area and number of surface hydroxyl groups of 297.0?m²/g and 1.08?mmol/g, respectively. The amount of phosphate adsorbed increased with the temperature. The isotherm model of Langmuir was used to fit experimental adsorption equilibrium data for phosphate adsorption onto G-BE20. The calculated thermodynamic parameters show the spontaneous and endothermic nature of the adsorption process. The equilibrium adsorption onto G-BE20 was reached within 16?h and the amount of phosphate adsorbed was 8.4?mg/g. The kinetic mechanism of phosphate uptake was evaluated with two different models: the Largergren pseudo first- and pseudo second-order models. The data obtained showed a better fit to the pseudo second-order model (0.991) than to the pseudo first-order model (0.967), as indicated by the r values. The rate constants for the adsorption of phosphate onto G-BE20 were calculated as 0.481?1/h and 0.029?g/mg?h. The adsorption of phosphate onto G-BE20 was the maximum in the pH range 3.0-4.0.     

Evaluation of adsorption and kinetics of neem leaf powder (Azadirachta indica) as a bio-sorbent for desulfurization of dibenzothiophene (DBT) from synthetic diesel

The need for a sustainable environment has necessitated the development of a green adsorbent that is efficient, cheap, and readily available to serve as an alternative adsorbent for the removal of the refractory sulfur-containing compound from diesel. In this current study, neem-leaf powder (NLP) was activated using H₂SO₄ and tested in desulfurization adsorption experiments of synthetic diesel containing Dibenzothiopene (DBT) during a batch operation. The synthetic diesel contained 0.1 g of DBT in 100 mL of hexane. Before testing, physio-chemical characteristics of the adsorbent were checked via Fourier transmission infrared (FTIR) spectroscopy for surface chemistry; via N₂ physisorption at 77 K for textural properties; SEM quipped with EDX for morphology and elemental composition; and XRD for purity and crystallinity. The results showed that the physico-chemical nature of the adsorbent played a significant role in enhancing the adsorption capacity of the material for DBT. Activated NLP displayed DBT removal of 65.78% at 30 °C using 0.8 g of the adsorbent. Furthermore, the behaviour of the adsorbent during the adsorption could be adequately described using the Freundlich isotherm model. Pseudo-first-order and pseudo-second-order kinetics model describe well the adsorption kinetics of DBT onto the activated NLP.     

Multi-Walled Carbon Nanotubes and Powder-Activated Carbon Adsorbents for the Removal of Nitrofurazone from Aqueous Solution

Multi-walled carbon nanotubes (MWCNTs) and powder-activated carbon (PAC) were used as adsorbents for adsorption of nitrofurazone, a veterinary medicine, from aqueous solutions. The adsorbents were characterized using FTIR transform infrared spectroscopy, N₂ adsorption/desorption isotherms, and scanning electron microscopy. The effects of initial pH, contact time, and temperature on adsorption capacity of the adsorbents were investigated. For MWCNT and PAC, the result showed that when the pH value was ranged from 2.0 to 10.0, the dosage of adsorbent was 0.02 g, and adsorptive time is 4 hours, the removal efficiencies for nitrofurazone were 96.8% and 94.7%, and the corresponding maximum capacities at 283 K were close to 50.8 mgg^?1 and 59.9 mgg^?1, respectively. For nitrofurazone, the pseudo-second-order kinetic model provided the best fit to the experimental data. The Boyd model indicated the mechanism for adsorption processes was mainly external mass transfer, while the effect of particle internal diffusion was relatively weak. Liu model could best fit to the experimental data of isothermal adsorption. The data of adsorption thermodynamics showed that the adsorption process was spontaneous.