Adsorptive removal of methylene blue from aqueous solution on activated carbon prepared from Malawian baobab fruit shell wastes: Equilibrium,kinetics and thermodynamic studies

Baobab fruit shell (BFS), a renewable bio-waste from Malawian baobab tree was used as a precursor for the production of a low-cost activated carbon to remove methylene blue (MB) from aqueous solution. Parameters such as contact time, initial methylene blue concentration, adsorbent dose and temperature were studied. The adsorption process can be well described by both Langmuir isotherm and the pseudo-second-order kinetics. The maximum monolayer adsorption capacity of MB dye was ca. 334.45 mg/g. The negative value of the Gibb’s free energy and positive value of adsorption enthalpy showed the spontaneous nature and endothermic nature of the adsorption process, respectively.     

Removal of Basic Red 46 dye from aqueous solution by adsorption and photocatalysis: equilibrium,isotherms, kinetics,and thermodynamic studies

ABSTRACT

In this study, the main objective is the elimination of Basic Red 46 dye by coupling two processes, adsorption on activated clay followed by photocatalysis over ZnO as photocatalyst. The adsorption was investigated under different conditions of pH, adsorbent dose, dye concentrations, and temperature. The best adsorption yield occurs at neutral pH ~ 7 within 60 min with an uptake percentage of 97% for a concentration of 25 mg/L and a dose of 0.5 g/L. The results at equilibrium were successfully described by the Langmuir model with an adsorption capacity of 175 mg/g. To investigate the mechanism of dye adsorption characteristic, the adsorption constants were determined using pseudo first order, pseudo second-order and intraparticle diffusion model. It was found that the Basic Red 46 dye adsorption is well described by the pseudo second-order kinetic. The second part of this work was dedicated to the photodegradation onto ZnO under solar irradiation of the residual BR 46 concentration, remained after adsorption. For the remaining concentrations, the removal yields reach 100% under.     

Kinetic,equilibrium and thermodynamic studies on removal of Cr(VI) by activated carbon prepared from Ricinus communis seed shell

A study on the removal of hexavalent chromium ions from aqueous solution by using activated carbon prepared from Ricinus communis has been done. In this process, it was carbonised and activated by treating with concentrated sulphuric acid followed by heating for 5 h at 500°C. Batch adsorption experiments are also carried out as a function of pH, contact time, initial concentration of the adsorbate, adsorbent dosage and temperature. The experimental data are fitted well to the Freundlich adsorption isotherm. Thermodynamic parameters such as ΔH°, ΔS° and ΔG° are calculated, which indicated that the adsorption is spontaneous and endothermic in nature. Adsorbent used in this study is characterised by FT‐IR and SEM before and after the adsorption of Cr(VI). © 2011 Canadian Society for Chemical Engineering     

Adsorption of Lead by Geomaterial Matrix: Adsorption Equilibrium and Kinetics

Industrial activity generates huge amounts of waste, whose storage can lead to serious problems of groundwater pollution by infiltration of landfill leachates. Geomaterials used as water barriers may be a solution to this problem. This work is devoted to the elaboration of new geomaterials based on Algerian clay, activated carbon, cement, and polymer for containment of stored waste and the study of their performances towards inorganic pollutants. Thus we elaborated a set of three geomaterials GM1, GM2, and GM3 with various clay and activated carbon contents and whose polymer and cement compositions are maintained constant. The higher clay content (80%) was used in preparing GM1.

The retention properties towards lead were assessed by the adsorption isotherms of geomaterials and their minerals constituents. The study of lead adsorption isotherms on geomaterials showed mainly that GM1, with the highest clay and lowest activated carbon contents and with the highest specific surface area, is very effective for trapping lead. Moreover, its adsorption capacity is pH-dependant; the highest Pb²⁺ amount adsorbed is obtained for pH12. On the other hand, it has been shown that the retention of lead is a result of the components contribution: clay, activated carbonm and cement.     

Extraction and recovery of pectic fragments from citrus processing waste for co–production with ethanol

BACKGROUND: Approximately 0.7 ? 1 × 10⁶ dry tons of citrus processing waste (CPW) are produced annually in the United States. CPW is sold as animal feed but often the financial return does not exceed the production cost. Polysaccharides comprise 40% of the total dry matter of which pectin is the major component. CPW was steam treated to extract pectin fragments (PFs) as a value added co–product prior to fermentation of other sugars for biofuels production. RESULTS: PFs were extracted in high yields, along with polymeric arabinans, galactans and arabinogalactans. The extracted polysaccharides ranged in size from small oligomers to polymers of ～700 000 g mol^?1. Acidified treatments led to greater fragmentation of water soluble polysaccharides, but did not enhance fragmentation of pectins to small oligomers (> 30 mer). Methylesterified PFs, arabinans and galactans were recovered by ethanol precipitation while demethylesterified PFs were recovered and purified by precipitation with dilute HCl. CONCLUSION: Steam treatment of CPW provides for rapid, efficient fragmentation of protopectin into highly methylesterified PFs that could be recovered by precipitation. The steaming process for preparation of PFs is environmentally friendly. No toxic chemicals are introduced and the remaining CPW can be used in fermentations to produce ethanol and other compounds. © 2012 Society of Chemical Industry     

Removal of Rhodamine B from aqueous solutions and wastewater by walnut shells: kinetics,equilibrium and thermodynamics studies

An adsorption study of Rhodamine B (RB) dye from aqueous solutions was carried out using walnut shells pretreated by different methods. In addition to the effects of the pretreatment, the effects of various parameters like pH, adsorbent dose, contact time, initial dye concentration and temperature on the adsorption of RB was studied. The adsorption process was highly pH dependent and a maximum adsorption was achieved at pH 3.0. The best fit for the rates of dye adsorption was a pseudo-second-order kinetic model with good correlation coefficients (R²>0.99). Langmuir isotherms were used to determine that the maximum loading capacity of the different walnut shells and the RB capacities ranged from 1.451–2.292 mg·g^-1. The dye adsorption was also evaluated thermodynamically. Positive standard enthalpy (?H°) values were obtained indicating that the RB adsorption process is endothermic as well as ?G° and ?S° values showed that adsorption process is spontaneous with an increased randomness at the solid-liquid interface. Desorption studies were carried out to explore the feasibility of regenerating the used walnut shells and it was found that 97.71%–99.17% of the retained RB was recovered with 0.1 mol?L^-1 NaOH solution. The walnut shells were also successfully used to remove RB from industrial effluents.     

Preparation and Characterization of Activated Carbon from Chestnut Shell and its Adsorption Characteristics for Lead

Activated carbons were prepared from chestnut shell by phosphoric acid activation and the prepared activated carbons were used to remove lead(II) from aqueous solutions. The effects of impregnation ratio (IR) and activation temperature on activated carbon production were investigated. The produced activated carbons were characterized by N₂ adsorption, scanning electron microscopy (SEM), and atomic force microscopy (AFM) techniques. The highest surface area (1611 m²/g) and total pore volume (0.7819 cm³/g) were obtained at a carbonization temperature of 500°C with an impregnation ratio of 3/1. The resulting activated carbon was used for removal of lead(II) from aqueous solution. The effects of temperature, contact time, and adsorbent dosage were investigated. The adsorption isotherm studies were carried out and the obtained data were analyzed by the Langmuir, Freundlich, and Temkin equations. The rate of adsorption was found to conform to the pseudo-second-order kinetic model. The Langmuir isotherm equation showed better fit for all temperatures and the maximum adsorption capacities of lead(II) was obtained as 138.88 mg/g at 45°C.     

Removal of manganese from water by electrocoagulation: Adsorption,kinetics and thermodynamic studies

The present study provides an electrocoagulation process for the removal of manganese (Mn) from water using magnesium as anode and galvanised iron as cathode. The various operating parameters like effect of initial pH, current density, electrode configuration, inter‐electrode distance, coexisting ions and temperature on the removal efficiency of Mn were studied. The results showed that the maximum removal efficiency of 97.2% at a pH of 7.0 was achieved at a current density 0.05 A/dm² with an energy consumption of 1.151 kWhr/m³. Thermodynamic parameters, including the Gibbs free energy, enthalpy and entropy, indicated that the Mn adsorption of water on magnesium hydroxides was feasible, spontaneous and endothermic. The experimental data were fitted with several adsorption isotherm models to describe the electrocoagulation process. The adsorption of Mn preferably fitting the Langmuir adsorption isotherm suggests monolayer coverage of adsorbed molecules. In addition, the adsorption kinetic studies showed that the electrocoagulation process was best described using the second‐order kinetic model at the various current densities. © 2012 Canadian Society for Chemical Engineering     

废弃物衍生分级多孔炭的制备及吸附应用进展

分级多孔炭因其高比表面积、大孔容及分级孔结构,目前广泛应用于超级电容器、锂离子电池、催化及吸附等领域。废弃物在热解气化过程中残留的碳基材料则是制备分级多孔炭很好的前体。本文根据废弃物来源及自身特性间的差异,对生物质和非生物质废弃物作为原料制备的分级多孔炭的特性及应用进行了综述及总结。并对不同制备方法的优劣及适用对象进行了比较。对分级多孔炭在挥发性有机物（VOCs）吸附、CO₂吸附捕集、染料吸附、抗生素以及酚类物质的吸附过程进行分析,总结出废弃物基多孔炭在孔径结构及表面杂原子掺杂情况下的优势能够增强这几类物质的吸附效果。结合已有文献,对废弃物基分级多孔炭的制备、孔径设计及表面官能团设计提出展望。     

Removal of crystal violet from wastewater using resorcinol-formaldehyde carbon xerogels

Resorcinol-formaldehyde activated carbon xerogels (RF-ACXs) were prepared at different conditions. RF-ACXs were characterized by Fourier transform infrared spectroscopy, surface area and porosity analyzer, X-rays diffraction, energy dispersive X-ray diffraction, and scanning electron microscopy. Batch adsorption was used to evaluate the ability of RF-ACXs to remove crystal violet (CV) from wastewater. CV adsorption capacities of RF-ACXs ranged from 66.47 to 121.53 mg·g^?1 for CV initial concentration ranged from 0 to 120 mg/L at 60°C. Kinetic and equilibrium adsorption data were analyzed using collection of models. The best results were achieved with the pseudo-second order kinetic model and Langmuir’s equilibrium model. Regenerability and reusability of RF-ACXs were investigated.     

A novel agricultural waste based adsorbent for the removal of Pb(II) from aqueous solution: Kinetics,equilibrium and thermodynamic studies

Fig sawdust was used as a precursor for the production of activated carbon by chemical activation with H₃PO₄. The developed Fig sawdust activated carbon (FSAC) was used as a biosorbent for the removal of Pb(II) from aqueous solution. Highest adsorption of Pb(II) (95.8%) was found at pH 4. Equilibrium data fitted very well with the Langmuir isotherm model. Maximum adsorption capacity was determined 80.645 mg g⁻¹ at pH 4. Kinetic studies demonstrated that the adsorption followed a pseudo second order kinetics model. The negative value of ΔG° confirmed the feasibility and spontaneity of FSAC for Pb(II) adsorption.     

Production of a producer gas from woody waste via air gasification using activated carbon and a two-stage gasifier and characterization of tar

Experiments were carried out with a woody waste fraction using a two-stage gasifier consisting of a fluidized bed zone and a tar cracking zone that was filled with activated carbon. In the experiments, the effects of experimental conditions such as the temperature and the equivalence ratio were investigated. In addition, the results of the experiments with virgin activated carbon, without activated carbon, and with spent activated carbon were compared. The producer gases that were obtained in the experiments were analyzed using GCs (FID and TCD) and a GC-MS system. The producer gas obtained with the application of activated carbon at an ER of 0.2 had high H₂ content (16 vol.%, N₂-free), and its lower heating value was above 10 MJ/Nm³. In addition, the total amount of the tar captured by the scrubbers and the electrostatic precipitator was reduced sixfold when activated carbon was applied.     

Fenton法＋活性炭吸附处理苯海因生产废水的研究

苯海因生产废水中CODcr、挥发酚等污染物浓度都比较高,采用三级Fenton＋活性炭吸附处理后,CODcr、挥发酚均能达到国家一级排放标准。     

Determination of adsorption operating conditions in dynamic mode on basis of batch study: Application for Dimethylphthalate elimination on activated carbon prepared from Arundo donax

This study aims to determine the operating conditions to implement the Dimethylphthalate removal using an activated carbon prepared from Arundo donax, carbonized at 358?°C during 13?min. To achieve this objective, the study is conducted in batch and dynamic mode. Several kinetic models are applied, namely pseudo-first order, pseudo-second order, intragranular, and Bangham models. The pseudo-second-order model fits the data perfectly, the estimated regression coefficients >0.999. The intragranular diffusion takes place in two stages. The two-parameter (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich) and three-parameter models (Redlich-Peterson, Sips, and Toth) are applied to model the equilibrium isotherms. The nonlinear regression methodology based on the error functions (hybrid fractional error function, Marquardt’s percent standard deviation, average relative error, Sum of the absolute errors) is applied. The HYBRID fits properly the data showing that the Temkin model gives the best fitting (R²_adj = 0.992), and the Dubinin-Radushkevich model the worst (R²_adj = 0.793). The thermodynamic study shows that the adsorption occurs according to a physical process. The DMP desorption is more effective with a 5% NaOH solution. In dynamic mode, the runs are conducted in fixed bed column. The effect of the bed height, the DMP initial concentration, and the flow rate on the breakthrough curves is investigated, then these breakthrough curves are modeled using the Thomas and Bed Depth Service Time models. The regeneration of the exhausted Arundo donax activated carbon is performed in a column, after 5 cycles, the breakthrough time decreases from 65.3?to 26.8?h, however, the exhaustion time varies less rapidly.     

Isotherms,kinetics, and thermodynamic studies for adsorption of pigments and oxidation products in oil bleaching from catfish waste

Abstract

The aim of this work was to study the bleaching of oil extracted from the heads of the catfish by thermomechanical process through equilibrium, kinetics, and thermodynamics adsorption studies. The condition for the bleaching step was with 1% (w/w) adsorbent composed of 95% activated earth and 5% activated carbon (w/w). The pseudo-first order and pseudo-second order models were the most appropriate to represent the adsorption kinetics. The temperature of 80?°C increased the adsorption capacity of the two adsorbates, and the activation energies values were of 47.47 and 44.82?kJ mol^?1, respectively, for the adsorption of carotenoids and peroxides. The Langmuir model was the most appropriate to describe the bleaching equilibrium curves. The thermodynamic parameters revealed that the processes were endothermic, favorable, and spontaneous and the interaction between adsorbent and adsorbate was physical.     

Removal of pyridine derivatives from aqueous solution by activated carbons developed from agricultural waste materials

The paper investigates the ability of activated carbons developed from coconut shell to adsorb α-picoline, β-picoline, and γ-picolin from aqueous solution. The developed carbons are designated as SAC (activated carbon derived from coconut shells with out any treatment) and ATSAC (activated carbon derived from acid treated coconut shells). The carbons were, characterized and utilized for the sorption of α-picoline, β-picoline, and γ-picoline at different temperatures, particle size, pH and solid to liquid ratio. All the studies were performed by batch method to determine various equilibrium and kinetic parameters. The Langmuir and Freundlich isotherm models were applied and the Langmuir model was found to best report the equilibrium isotherm data. The adsorption of α-, β-, and γ-picoline followed the pseudo-second order rate kinetics. On the basis of kinetic studies, various rate and thermodynamic parameters such as effective diffusion coefficients, activation energy and activation entropy were evaluated. It was concluded that in majority of cases, the adsorption is controlled by particle diffusion at temperatures 10° and 25 °C while at 40 °C it is controlled by film diffusion mechanism. Similarly at concentrations 25 and 50 mg/l the adsorption was governed by particle diffusion in most of the cases while at >50 mg/l it was film diffusion controlled. The overall capacity of ATSAC was higher than SAC. The sorption capacity of γ-picoline was found more followed by β-picoline and α-picoline.     

活性炭纤维吸附石化废水中苯酚的吸附平衡及动力学

以活性炭纤维(ACF)为吸附剂,研究了ACF对石化废水中苯酚的吸附平衡及动力学。在25、40、55及65℃下测定了吸附平衡等温线,采用Langmuir、Freundlich和Redlich-Peterson等温方程对吸附平衡数据进行了拟合,结果表明吸附平衡数据更符合Langmuir与Redlich-Peterson方程。体系温度从25、40、55升高到65℃时,ACF对模拟废水中苯酚的吸附能力随温度升高而降低,而ACF对石化废水中苯酚的吸附能力并不完全随温度升高而降低。ACF对石化废水与模拟废水中苯酚的吸附过程均符合拟二级动力学方程。颗粒内扩散模型对吸附动力学实验数据的拟合结果表明,吸附初期吸附速率主要受颗粒内扩散控制且石化废水中苯酚吸附的k_id随温度升高而增大,吸附中后期吸附速率除了受颗粒内扩散控制外还受到外扩散的影响。热力学分析表明,石化废水中ACF吸附苯酚过程的ΔG<0,由于石油类物质对苯酚吸附的影响,温度升高ΔG的数值变化不大。     

Adsorption equilibrium of copper ion and phenol by powdered activated carbon, alginate bead and alginate-activated carbon bead

The adsorption equilibrium characteristics for single and binary components of copper ion and phenol onto powdered activated carbon, alginate bead and alginate-activated carbon (AAC) bead were studied. Adsorption equilibrium data of phenol and copper ion onto the adsorbents could be represented by Langmuir equation. The adsorption capacity of Cu²⁺ onto different adsorbents was in the following order: alginate bead > AAC bead > powdered activated carbon (PAC). On the other hand, that of phenol was: PAC > AAC bead > alginate bead. Multi-component equilibrium data were correlated by three different models. Among them the ideal adsorbed solution theory (IAST) gave the best fit to our data. And the adsorption amount of Cu²⁺ onto AAC bead was greater than that of phenol in the binary components.     

New carbon composite adsorbents for the removal of textile dyes from aqueous solutions: Kinetic,equilibrium, and thermodynamic studies

New carbon composite materials were prepared by pyrolysis of mixture of coffee wastes and red mud at 700 °C with the inorganic: organic ratios of 1.9 (CC-1.9) and 2.2 (CC-2.2). These adsorbents were used to remove reactive orange 16 (RO-16) and reactive red 120 (RR-120) textile dyes from aqueous solution. The CC-1.9 and CC-2.2 materials were characterized using Fourier transform infrared spectroscopy, Nitrogen adsorption/desorption curves, scanning electron Microscopy and X-ray diffraction. The kinetic of adsorption data was fitted by general order kinetic model. A three-parameter isotherm model, Liu isotherm model, gave the best fit of the equilibrium data (298 to 323 K). The maximum amounts of dyes removed at 323 K were 144.8 (CC-1.9) and 139.5 mg g^?1 (CC-2.2) for RO-16 dye and 95.76 (CC-1.9) and 93.80 mg g^?1 (CC-2.2) for RR-120 dye. Two simulated dyehouse effluents were used to investigate the application of the adsorbents for effluent treatment.