Adsorption of Furfural from Aqueous Solution onto Activated Carbon: Kinetic,Equilibrium and Thermodynamic Study

Abstract

The present study aims to evaluate the influence of various experimental parameters viz. initial pH (pH ₀), adsorbent dose, contact time, initial concentration and temperature on the adsorptive removal of furfural from aqueous solution by commercial grade activated carbon (ACC). Optimum conditions for furfural removal were found to be pH ₀ ≈ 5.9, adsorbent dose ≈ 10 g/l of solution and equilibrium time ≈ 6.0 h. The adsorption followed pseudo‐second‐order kinetics. The effective diffusion coefficient of furfural was of the order of 10^?13 m²/s. Furfural adsorption onto ACC was found to be best represented by the Redlich‐Peterson isotherm. A decrease in the temperature of the operation favorably influenced the adsorption of furfural onto ACC. The positive values of the change in entropy (ΔS ⁰); and the negatived value of heat of adsorption (ΔH ⁰) and change in Gibbs free energy (ΔG ⁰) indicated feasible, exothermic, and spontaneous nature of furfural adsorption onto ACC.     

Adsorption Kinetics of Fluroxypyr Herbicide in Aqueous Solution onto Granular Activated Carbon

Fluroxypyr is a widely used herbicide whose presence in natural waters has prompted research into its removal by adsorption. This article reports a kinetics study of fluroxypyr adsorption on a commercial activated carbon. The experimental study used a micro differential column batch reactor operated at three solution flow rates and two initial fluroxypyr concentrations, establishing a differential regime in order to obtain correct experimental data. Initial rates at zero coverage permitted the external transfer coefficient k _L to be calculated. Internal surface diffusion coefficients D _S were determined by using the Homogeneous Surface Diffusion Model running the FAST software and taking advantage of tabulated user-oriented solutions. This model satisfactorily fits the experimental data. D _S values were 2.5 × 10^?14 and 4.2 × 10^?14 m² s^?1 for initial concentrations of 30 and 50 mg/L, respectively. These values were confirmed by experiments in a widely used shaken batch reactor with a determined k _L value.     

Adsorption of N-Vinylpyrrolidone from Polyvinylpyrrolidone Solution onto Bamboo-Based Activated Carbon

The adsorption of N-vinylpyrrolidone from aqueous polyvinylpyrrolidone solution using bamboo-based activated carbon was studied. The adsorption isotherms of N-vinylpyrrolidone on the carbon were determined and modeled with the Langmuir, Freundlich, and Temkin models. The Langmuir model provides the best fitting for the equilibrium data and the maximum monolayer adsorption capacity was estimated to be 833.3 mg/g. The kinetics of the adsorption process of N-vinyulpyrrolidone were modeled using various equations including pseudo first-order, pseudo second-order, and intra-particle diffusion equations. The adsorption process follows the pseudo second-order kinetic model, suggesting that the adsorption mechanism is chemisorption. The activation energy for the adsorption is 86.4 kJ/mol. Thermodynamic parameters such as Gibbs free energy, enthalpy, and entropy were determined. The positive value of enthalpy change indicates that the adsorption process is endothermic.     

Removal of Acid Dyes from Aqueous Solutions using Chemically Activated Carbon

Abstract

Textile dyes (Acid Yellow 17 and Acid Orange 7) were removed from its aqueous solution in batch and continuous packed bed adsorption systems by using thermally activated Euphorbia macroclada carbon with respect to contact time, initial dye concentration, and temperature. The activated carbon was prepared using a cheap plant-based material called Euphorbia macroclada, which was chemically modified with K₂CO₃. Lagergren-first-order and second-order kinetic models were used to fit the experimental data. Equilibrium isotherms were analyzed by Langmuir and Freundlich isotherms. Equilibrium data fitted well the Langmuir model in the studied temperature (25–55°C) ranges. The maximum adsorption capacity of AY17 and AO7 onto activated carbon was found to be 161.29 and 455 mgg^?1, respectively by Langmuir isotherm at 55°C. Breakthrough curves for column adsorption have also been studied. The desorption of dyes has been experimentally investigated using NaOH solution of pH 11.     

活性炭对单宁酸的吸附去除性能

三卤甲烷(THMs)是水中天然有机物在氯化消毒过程中产生的对人体有致癌作用的挥发性物质,腐殖酸是生成消毒副产物的主要前驱物。活性炭能够去除水中的多种有机污染物,其中对腐殖酸的去除性能可以通过单宁酸值来表征。通过间歇试验,研究了两种活性炭对单宁酸的吸附行为,探索其对单宁酸的吸附规律。结果表明308 K时,1#炭对单宁酸的饱和吸附量较大,为616.0 mg/g。升高温度有利于两种活性炭对单宁酸的吸附,表明吸附过程为吸热过程。此外,两种活性炭对单宁酸的吸附动力学可以用Largergren伪二级速率方程很好地拟合,吸附过程是双速过程。1#炭对单宁酸的吸附速率更快,比3#炭具有更高的单宁酸吸附性能。1#和3#炭对单宁酸的吸附活化能依次分别为17.5和3.9 kJ/mol,说明1#炭的反应速率随温度的升高增加得较快,符合Arrhenius的经验方程,吸附反应速率随温度升高而加快的规律,活性炭对单宁酸的吸附可认为是化学吸附。     

Removal of Phosphate from Aqueous Solution with Modified Bentonite

Bentonite combined with sawdust and other metallic compounds was used to remove phosphate from aqueous solutions in this study. The adsorption characteristics of phosphate on the modified bentonite were investigated, including the effects of temperature, adsorbent dosage, initial concentration of phosphate and pH on removal of phosphate by conducting a series of batch adsorption experiments. The results showed that 98% removal rate of phosphate was obtained since sawdust and bentonite used in this investigation were abundantly and locally available. It is concluded that modified bentonite is a relatively efficient, low cost and easily available adsorbent for the removal of phosphate from aqueous solutions.     

Removal of Methyl Orange from Aqueous Solution Using Activated Papaya Leaf

The present investigation describes the potential of acid activated papaya leaf for the adsorption of methyl orange (MO) dye from aqueous solution. The FT-IR analysis indicated the presence of a wide variety of functional groups on the surface of the activated papaya leaf. Scanning electron microscopy and Electron dispersion X-ray techniques indicated the morphological behavior of adsorption onto the adsorbent, and weight percentage of chemical compositions available on the surface of adsorbent. The parameters, such as pH, contact time, and agitation rate giving the highest adsorption efficiency were obtained at 2, 120 min, and 150 rpm, respectively. The Langmuir model was found to represent the isotherm data better than other isotherms studied. Batch adsorption studies, based on the assumption of a pseudo first-order, Elovich Equation, and the pseudo second-order showed that the kinetic data followed closely a pseudo second-order mechanism. The adsorption capacity of activated papaya leaf for the removal of MO dye was found to be 333.34 mg/g. These showed that papaya leaf could be considered as a good and economical substitute of commercial activated carbon.     

Evaluation of Phosphate Removal Efficiency from Aqueous Solution by Polypyrrole/BOF Slag Nanocomposite

The polypyrrole/basic oxygen furnace slag nanocomposite (PPy–BOFS) was synthesized and characterized by FTIR, SEM, ICP-AES, and X-ray diffraction studies and was employed as an adsorbent for the removal of phosphate ions from aqueous solution by the batch sorption method. The maximal amount of adsorption was found to be 9.13 mg/g (45°C). The Langmuir and Freundlich isotherms were used to describe the adsorption equilibrium. The kinetics of the adsorption process was investigated using the Lagergren rate equation and the Weber Morris intraparticle diffusion model. The FTIR and XRD pattern of the adsorbent before and after the adsorption was recorded to get better insight into the mechanism of the adsorption process. The results of equilibrium and spectral investigations revealed that the removal of phosphate by the nanocomposite involves various mechanisms followed by the nanocomposite and the constituents present in it.     

Rapid Removal of Toxic Remazol Brilliant Blue-R Dye from Aqueous Solutions Using Juglans nigra Shell Biomass Activated Carbon as Potential Adsorbent: Optimization,Isotherm, Kinetic,and Thermodynamic Investigation

Recently, the treatment of effluent by agricultural waste biomass has significantly attracted wide interest among researchers due to its availability, efficacy, and low cost. The removal of toxic Remazol Brilliant Blue-R (RBBR) from aqueous solutions using HNO₃-treated Juglans nigra (walnut) shell biomass carbon as an adsorbent has been examined under various experimental conditions, such as initial pH, adsorbate concentration, adsorbent dosage, particle size, agitation speed, and type of electrolyte. The experiments are designed to achieve the maximum dye removal efficiency using the response surface methodology (RSM). The optimum pH, adsorbent dosage, and particle size were found to be 1.5, 7 g L⁻¹, and 64 μm, respectively for maximum decolorization efficiency (98.24%). The prepared adsorbent was characterized by particle size, Brunauer–Emmett–Teller (BET) surface area, pore volume, zero-point charge (pH_zpc), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy/energy dispersive X-ray spectroscopy (FE-SEM/EDX), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Based on fitting the experimental data with various models, the isotherm and kinetic mechanism are found to be more appropriate with Langmuir isotherm and pseudo-second-order kinetics. The adsorption mechanism can be described by the intra-particle diffusion model, Bangham, and Boyd plots. The overall rate of adsorption is controlled by the external film diffusion of dye molecules. The maximum monolayer adsorption capacity, (q_max) 54.38 mg g⁻¹ for RBBR dye, was obtained at a temperature of 301 K. From a thermodynamic standpoint, the process is endothermic, spontaneous, and the chemisorption process is favored at high temperatures. Desorption studies were conducted with various desorbing reagents in various runs and the maximum desorption efficiency (61.78% in the third run) was obtained using the solvent methanol. Reusability studies demonstrated that the prepared adsorbent was effective for up to three runs of operation. The investigation outcomes concluded that walnut shell biomass activated carbon (WSBAC) is a cost-effective, eco-friendly, and bio-sustainable material that can be used for synthetic dye decolorization in aqueous media.     

Removal of Selected Basic Dyes using Activated Carbon from Tannery Wastes

Activated carbon prepared from tannery leather waste (TLW-AC) has been studied for its efficiency of removal of basic dyes, namely rhodamine B (RB), methylene blue (MB), and malachite green (MG) from aqueous solutions. Factors influencing dye adsorption such as the concentration of dye, pH, contact time, and temperature were investigated. The adsorption was found to be strongly dependent on the pH and temperature. The maximum sorption capacity of RB was obtained at pH 3 and for MB and MG was obtained at pH 11. Various thermodynamic parameters such as ΔG°, ΔH°, and ΔS° were calculated. The kinetic studies reveal that the adsorption process follows the pseudo second-order kinetic model. The equilibrium data have been well-described by the Langmuir and Freundlich models, and the data fitted well in both model equations. The study revealed that wastes from leather industry is an economically viable option for dye removal.     

花生壳活性炭对Cu~(2+)的吸附性能研究

以花生壳为原料,磷酸为活化剂制备花生壳活性炭,采用高分辨电子扫描电镜(SEM)对花生壳活性炭进行了表征。从热力学和动力学的角度,研究了花生壳活性炭对Cu2+的吸附行为。热力学研究表明:花生壳活性炭对Cu2+的吸附符合Langmuir等温吸附方程,该吸附是自发吸热过程。动力学研究表明:花生壳活性炭对Cu2+的吸附符合二级反应动力学方程反应特征,颗粒内扩散为主要控速步骤。     

活性碳纤维对甲醛吸附转化性能的研究

用对胺基苯甲酸(PABA)浸渍粘胶基活性碳纤维(Rayon-ACF)和聚丙烯腈基活性碳纤维(PAN-ACF),考察了两者对甲醛吸附性能的差异。结果表明:PAN-ACF和Rayon-ACF经PABA溶液浸渍处理后,样品中的N含量都明显提高,但其比表面积、微孔容积和总孔容都有所下降;不过对甲醛溶液蒸汽的吸附容量都明显提高。这主要是归因于浸渍处理后样品中-NH2的增加,进而由于化学吸附而使得对甲醛吸附量增加。Rayon-ACF样品的甲醛吸附容量远高于PAN-ACF样品,这可能同Ray-on-ACF样品有较多表面含氧官能团以及较大的微孔容积有关。甲醛在ACF的微孔空间中易于形成高凝缩的三聚甲醛,从而其吸附容量相应提高。     

油茶果壳活性炭对苯酚的吸附动力学研究

以油茶果壳制备的活性炭为吸附剂,探讨了温度、苯酚初始浓度对油茶果壳活性炭吸附苯酚性能的影响,并用两种动力学模型进行了拟合。结果表明:油茶壳活性炭对苯酚的吸附是一个较为快速的过程,60 min就可接近吸附平衡。油茶壳活性炭对苯酚的吸附动力学过程可以用准一级与准二级模型进行很好的描述,相关系数达到0.96以上。     

A Non-Conventional Adsorbent for the Removal of Clofibric Acid from Aqueous Phase

The adsorption of Clofibric acid, one of the most frequently prescribed high environmental risk drugs, was studied using H₃PO₄ activated Schumannianthus dichotomus (ASD). The chemical characteristics of the adsorbent were established by Bohem’s titration, pH_PZC, FTIR, SEM, XRD, porosity, and surface area analysis. It was observed that the adsorbent was microporous-mesoporous in nature with BET surface area of 1199.98 m².g^?1. The influence of temperature (303-323 K), pH (2-10), textural properties, adsorbent load, and contact time was studied. The Langmuir equation was found to best represent the equilibrium data for clofibric acid-adsorbent system, yielding monolayer adsorption capacity of 258.39 mg.g^?1 at 303 K. The pseudo-second order model best explained (R² > 0.999) the adsorption kinetics with rate constant 0.037 g.mg^?1min^?1. The thermodynamics parameters, ΔG°, ΔH°, and ΔS°, evaluated as ?8.14 kJmol^?1, ?34.07 kJmol^?1, and ?85.5 JK^?1mol^?1, respectively, revealed that the adsorption process is feasible, spontaneous, and exothermic in nature. In the column mode, the adsorption capacity of ASD (267.93 mg.g^?1) was found to be higher than the batch mode of operation (258.39 mg.g^?1). The cost incurred per kg of the developed adsorbent was USD 14.36.     

Peanut Shell Activated Carbon： Characterization,Surface Modification and Adsorption of Pb^2＋ from Aqueous Solution

Metal ion contamination of drinking water and waste water, especially with heavy metal ion such as lead, is a serious and ongoing problem. In this work, activated carbon prepared from peanut shell （PAC） was used for the removal of Pb^2＋ from aqueous solution. The impacts of the Pb25 adsorption capacities of the acid-modified carbons oxidized with HNO3 were also investigated. The surface functional groups of PAC were confirmed by Fourier transform infrared （FTIR） spectroscopy, X-ray photoelectron spectroscopy （XPS）, Boehm titration. The textural properties （surface area, total pore volume） were evaluated from the nitrogen adsorption isotherm at 77 K. The experimental results presented indicated that the adsorption data fitted better with the Langmuir adsorption model. A comparative study with a commercial granular activated carbon （GAC） showed that PAC was 10.3 times more efficient compared to GAC based on Langmuir maximum adsorption capacity. Further analysis results by the Langmuir equation showed that HNO3 [20% （by mass）] modified PAC has larger adsorption capacity of Pb^2＋ from aqueous solution （as much as 35.5 mg·g^-1）. The adsorption capacity enhancement ascribed to pore widening, increased cation-exchange capacity by oxygen groups, and the promoted hydrophilicity of the carbon surface.     

活性炭对丁酮的吸附动力学研究

研究了2种活性炭（木质活性炭和煤质活性炭）对丁酮的吸附,重点考察了活性炭的吸附时间、吸附温度和丁酮载气流量对丁酮吸附的影响,并用准一级、准二级、Elovich和Bangham 4种动力学模型对活性炭在不同温度条件下对丁酮的吸附行为进行了动力学拟合,确定其动力学吸附模型。实验表明：不同的活性炭对丁酮的吸附过程不同;活性炭对丁酮的吸附是一个吸附和解吸同时存在的过程,当吸附速率和解吸速率相等时,该过程达到吸附平衡;随着吸附温度的升高,活性炭对丁酮的饱和吸附量逐渐降低,说明活性炭对丁酮的吸附过程为放热反应;丁酮载气流量对活性炭吸附丁酮达到饱和的时间以及吸附速率有影响,对AC-1的最终饱和吸附量影响显著,对AC-2的最终饱和吸附量没有显著影响。这2种活性炭吸附丁酮最适宜的吸附温度均为303 K,最佳的载气流量为400 mL/min。在不同温度下对活性炭吸附丁酮的过程进行动力学分析,发现Bangham方程计算得到的相关系数R²大于0.99,因此,活性炭对丁酮的吸附动力学方程符合Bangham动力学方程。     

Removal of Lead (II) Ions from Aqueous Solution Using Eggplant Peels Activated Charcoal

The eggplant peel activated charcoal (EPPAC) was investigated as an adsorbent for the removal of lead II ions from aqueous solution. Three methods were tested for the production of eggplant peel activated charcoal (EPPAC) from eggplant peel charcoal (EPPC), yielding three different products; EPPAC-1, EPPAC-2, and EPPAC-3. The difference among the three methods lies in the primary physical mixing of the EPPC with the activating agent (potassium hydroxide) before heating the mixture in a furnace for activation. The removal efficiency of lead II ions by the three adsorbents was 57.7%, 70.0%, and 60.0% for EPPAC-1, EPPAC-2, and EPPPAC-3, respectively. The optimized activation parameters for EPPAC-2 were: activation time 2 hours, activation temperature 700°C, and activation ratio 1:2 (EPPAC: KOH). Scanning electron microscopy (SEM) revealed that EPPAC-2 has the most porous structure. The surface area of EPPAC-2 was measured to be 739 m²/g. Adsorption kinetics of lead (II) is best described by the pseudo-second-order kinetic model with second order rate constant of 1.70 × 10^?3 g/mg.h at room temperature. The adsorption of lead on EPPAC-2 is found to follow the Langmuir isotherm with a maximum adsorption capacity of 1.4 × 10² mg/g.     

改性坡缕石黏土对水中木质素磺酸钠吸附研究

用盐酸和焙烧处理的方法对坡缕石黏土进行了改性,制备了酸处理坡缕石黏土和热处理坡缕石黏土,用XRD和TEM对不同方法处理的坡缕石黏土进行了结构和形貌表征,并使用黏土对木质素磺酸盐废水进行了吸附研究。结果表明,在盐酸浓度为1.0 mol/L,60～70℃,改性处理6 h条件下制得的吸附剂相对于原土及热处理的坡缕石黏土吸附效果最好,动力学研究表明吸附过程符合准二级动力学模型,吸附等温线符合Langmuir吸附模型,其平衡吸附量可达到343.99 mg/g。实验证明该吸附过程是一个放热过程。     

Removal of Metanil Yellow from its Aqueous Solution by Fly Ash and Activated Carbon Produced from Different Sources

Abstract

The present study has been undertaken to observe the relative efficiency of removal of metanil yellow from its aqueous solution by using different adsorbents like fly ash and activated carbon produced from different sources i.e. coconut shell, mehagani saw dust, and rice husk. It has also been observed that the rate of adsorption is highly dependent on contact time, adsorbent dose, pH, and initial concentration of the dyestuff. Rate of removal has been observed to increase with increasing contact time and adsorbent dose but with decreasing initial concentration. Higher removal has been observed generally in acidic range. Adsorptions by the adsorbents under investigation follow the Freundlich and Langmuir isotherm models where Freundlich and Langmuir constants have also been determined at different temperatures. Isotherms have been used to obtain the thermodynamic parameters like free energy, enthalpy and entropy of adsorption. Kinetic studies showed that all the adsorbents follow first order adsorption rate model with respect to the dye solution concentration. Various kinetic parameters such as first order adsorption rate constant, mass‐transfer co‐efficient, pore‐diffusion constant, and activation energy of adsorption were evaluated to establish the mechanism. Adsorption processes were found to be endothermic, spontaneous, and pore‐diffusion controlled for all the adsorbents. Among the adsorbents used in this study, activated carbon produced from mehagani saw dust has been found to be the most effective, which remove almost 100% metanil yellow from its 1000 ppm aqueous solution.