Adsorption studies on the treatment of textile dyeing effluent by activated carbon prepared from olive stone by ZnCl2 activation

This study aimed to investigate the removal of a reactive dye from aqueous solution by adsorption. Activated carbon prepared from olive stone, an agricultural solid by-product, was used as adsorbent. Different amounts of activating agent (ZnCl₂) and adsorbent particle size were studied to optimise adsorbent surface area. The adsorption experiments were conducted at different process parameters such as adsorbent dose, temperature, equilibrium time and pH. The experimental results showed that at equilibrium time 120 min, optimum pH ranged between 3 and 4, and adsorbent dosage was 2.0 g 200 ml⁻¹. While the kinetic data support pseudo-second order, a pseudo-first order model shows very poor fit. Adsorption isotherms were obtained at three different temperatures (288, 298 and 308 K). The fitness of adsorption data to the Langmuir and Freundlich isotherms was investigated. In addition, the thermodynamic parameters such as isosteric enthalpy of adsorption (Δ H _ads) _y , isosteric entropy of adsorption (Δ S _ads) _y and free energy of adsorption Δ G ⁰_ads were calculated. BET surface area measurements were made to reveal the adsorptive characteristics of the produced active carbon. The surface area of the activated carbon produced with 20% w/w ZnCl₂ solution was 790.25 m² g⁻¹.     

Adsorption of acid orange 7 dye in aqueous solutions by spent brewery grains

Spent brewery grains (SBG), a by-product of the brewing process, were tested as an adsorbent of acid orange 7 dye (AO7), a monoazo acid dye currently used in paper and textile industries. The presence of AO7 in these effluents causes obvious environmental problems.

Kinetics studies of adsorption of AO₇ to SBG (3.75%, m/v) were carried out at 20 °C, using aqueous solutions with different AO7 concentrations (30–834 mg/L). For every situations tested, no significant variation in residual AO7 concentration in solution was detected after 1 h contact between the dye and the adsorbent. The adsorption process followed a pseudo-first order model.

The equilibrium process showed to be well described by both Freundlich and Langmuir isotherm models, at 20 and 30 °C. The maximum adsorption capacity was estimated to be 30.5 mg AO7/g SBG, at 30 °C.

Free energy of adsorption (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) changes were calculated to predict the nature of adsorption. The estimated values for ΔG° were −22.78 and −24.53 kJ/mol, respectively, at 293.3 K (20 °C) and 303.3 K (30 °C), which are rather low indicating that a spontaneous process occurred. The enthalpy changes and entropy of adsorption were 28.66 and 175.36 J/mol K, respectively. The positive value for ΔH° indicates that the adsorption of AO7 dye to SBG is an endothermic process. The positive value of entropy reflects the affinity of the adsorbent for AO7 dye.

The obtained results are very promising since: (i) high levels of colour removal (>90%) were achieved with low contact times adsorbent/dye (less than 1 h contact); and (ii) the whole SBG can be successfully used as adsorbent of AO7 dye in aqueous solution without needing any previous treatments such as milling and/or sieving. Spent grains, being a cheap, and easily available material, can be an alternative for more costly adsorbents used for dye removal in wastewater treatment processes.     

STUDIES ON THE ADSORPTION OF FURFURAL FROM AQUEOUS SOLUTION ONTO LOW-COST BAGASSE FLY ASH

The present study deals with the sorptive removal of furfural from aqueous solution by carbon-rich bagasse fly ash (BFA). Batch studies were performed to evaluate the influence of various experimental parameters, namely, initial pH (pH₀), adsorbent dose, contact time, initial concentration, and temperature on the removal of furfural. Optimum conditions for furfural removal were found to be pH₀ ≈ 5.5, adsorbent dose ≈4 g/L of solution, and equilibrium time ≈4 h. The adsorption followed pseudo-second-order kinetics. The effective diffusion coefficient of furfural is of the order of 10^-13 m²/s. Equilibrium adsorption data on BFA was analyzed by Freundlich, Langmuir, Dubnin-Radushkevich, Redlich-Peterson, and Temkin isotherm equations using regression and error analysis. The Redlich-Peterson isotherm was found to best represent the data for furfural adsorption onto BFA. Adsorption of furfural on BFA is favorably influenced by a decrease in the temperature of the operation. Values of the change in entropy (ΔS⁰) and heat of adsorption (ΔH⁰) for furfural adsorption on BFA were negative. The high negative value of change in Gibbs free energy (ΔG⁰) indicates the feasible and spontaneous adsorption of furfural on BFA.     

Adsorption of sulphur dioxide onto activated carbon prepared from oil-palm shells with and without pre-impregnation

Adsorption of sulphur dioxide (SO₂), a common gaseous pollutant, on oil-palm-shell activated carbon in a fixed bed was studied in this paper. Oil-palm shell is an abundant agricultural solid waste in tropical countries like Malaysia and Thailand. The effects of fixed-bed length, SO₂ gas superficial velocity, adsorbent particle size and internal pore structure on fixed-bed performance were investigated. Some characteristic parameters such as the breakthrough time, τ_0.05, exhaustion time, τ_0.95, length of mass transfer zone, L_MTZ, adsorptive capacity, W, and adsorption rate constant, K, were derived from the breakthrough curves. Tests of SO₂ adsorption onto activated carbons prepared from oil-palm shells pre-impregnated with potassium hydroxide (KOH) and phosphoric acid (H₃PO₄) of different concentrations were also carried out. It was found that the fixed-bed performance was not only dependent on the operating conditions and the textural properties of the adsorbent but was also influenced by the surface chemistry of the adsorbent, which was related to the type and concentration of the impregnating agent. In general, the quality of oil-palm-shell activated carbon prepared by CO₂ activation is comparable to that of a commercial product, and the samples prepared from oil-palm shell with KOH pre-impregnation are more suitable for the removal of SO₂ gas.     

Adsorption and desorption kinetics for hydrophilic and hydrophobic vapors on activated carbon

Adsorption dynamics are of fundamental importance in applications of adsorbents in real situations. The adsorption/desorption characteristics of a series of adsorbates, with varying hydrophilic/hydrophobic and structural characteristics, for activated carbon BAX950, were investigated for temperatures in the range 288-323 K. These data provide a comprehensive kinetic study of adsorption/desorption for an activated carbon. The results are discussed in relation to the adsorbent pore structure and functional group concentration, adsorptive structure and adsorption mechanism. The study provides evidence for a compensation effect where activation energy and ln(pre-exponential factor) parameters obtained from the Arrhenius equation exhibit a linear correlation.     

The role of adsorbent pore size distribution in multicomponent adsorption on activated carbon

The impact of adsorbent pore size distribution (PSD) on adsorption mechanism for the multi solute system was evaluated in this study. Anoxic and oxic adsorption equilibrium for the single solute (phenol), binary solute (phenol/2-methylphenol) and ternary solute (phenol/2-methylphenol/2-ethylphenol) systems on one granular activated carbon (GAC) F400 and two types of activated carbon fibers (ACFs), namely, ACC-10 and ACC-15, were determined. F400 has a wide PSD, while ACC-10 and ACC-15 have narrow PSD and their critical pore diameters are 8.0 Å and 12.8 Å, respectively. In single solute adsorption, the increase of adsorptive capacity under oxic conditions as compared to anoxic ones was related to the PSD of the adsorbent. Binary solute adsorption on ACC-10 and ternary solute adsorption on ACC-15 indicated no impact of the presence of molecular oxygen on the adsorptive capacity and the adsorption isotherms were well predicted by the ideal adsorbed solution theory (IAST). Significant differences between oxic and anoxic isotherms were noticed for other multicomponent adsorption systems. The narrow PSD of ACFs was effective in hampering the oligomerization of phenolic compounds under oxic conditions. Such a phenomenon will provide accurate predictions of fixed bed adsorbers in water treatment systems.     

甲烷在石墨烯和活性炭上的吸附

以研制新型吸附式天然气(ANG)吸附剂为目的,比较了甲烷在石墨烯和活性炭上的吸附平衡。首先,在温度区间273~293 K、压力范围0~8 MPa,测试甲烷在比表面积分别为300和2074 m²·g^-1石墨烯和活性炭上的吸附平衡数据。其次,应用格子理论导出的通用吸附等温方程,通过吸附平衡态能量分析及10-4-3相互作用势函数求解,确定甲烷分子在石墨烯平面和活性炭上的最大面密度、受到的壁面吸附作用势及其在吸附层内的作用能。结果表明,在相同温度下,吸附甲烷分子在石墨烯上吸附层内的相互作用能较其在活性炭上的大,甲烷分子在石墨烯平面上的集聚更为密集。提高石墨烯的比表面积将有效提高甲烷在其上的吸附容量。     

The performance of two adsorption ice making test units using activated carbon and a carbon composite as adsorbents

The available adsorption working pairs applied to adsorption refrigeration system, which utilize activated carbon as adsorbent, are mainly activated carbon-methanol, activated carbon-ammonia, and composite adsorbent-ammonia. The adsorption properties and refrigeration application of these three types of adsorption working pairs are investigated. For the physical adsorbents, consolidated activated carbon showed best heat transfer performance, and activated carbon-methanol showed the best adsorption property because of the large refrigerant amount that can be adsorbed. For the composite adsorbents, the consolidated composite adsorbent with mass ratio of 4:1 between CaCl₂ and activated carbon, showed the highest cooling density when compared to the granular composite adsorbent and to the merely chemical adsorbent. The physical adsorption icemaker that employs consolidated activated carbon-methanol as working pair had the optimum coefficient of refrigeration performance (COP), volume cooling power density (SCP_v) and specific cooling power per kilogram adsorbent (SCP) of 0.125, 9.25 kW/m³ and 32.6 W/kg, respectively. The composite adsorption system that employs the consolidated composite adsorbent had a maximum COP, SCP_v and SCP of 0.35, 52.68 kW/m³ and 493.2 W/kg, respectively, for ice making mode. These results are improved by 1.8, 4.7 and 14 times, respectively, when compared to the results of the physical adsorption icemaker.     

Thermodynamic studies on hydrogen adsorption on the zeolites Na-ZSM-5 and K-ZSM-5

Adsorption of dihydrogen onto the zeolites Na-ZSM-5 and K-ZSM-5 renders the fundamental H–H stretching mode infrared active. The corresponding infrared absorption bands were found at 4101 and 4112 cm⁻¹ for H₂/Na-ZSM-5 and H₂/K-ZSM-5, respectively. Thermodynamic characterization of the adsorbed state was carried out by means of variable-temperature infrared spectroscopy; simultaneously measuring integrated band intensity, temperature and equilibrium pressure of the gas phase. For the H₂/Na-ZSM-5 system, the standard adsorption enthalpy and entropy resulted to be ΔH° = −10.3 (±0.5) kJ mol⁻¹ and ΔS° = −121 (±10) J mol⁻¹ K⁻¹. For H₂/K-ZSM-5 corresponding values were −9.1 (±0.5) kJ mol⁻¹ and −124 (±10) J mol⁻¹ K⁻¹, respectively.     

EQUILIBRIUM CONSTANTS FOR ETHYL tert-BUTYL ETHER LIQUID-PHASE SYNTHESIS

Thermodynamic equilibrium constants for the liquid-phase synthesis of ethyl terl-butyl ether (ETBE) were determined experimentally in the temperature range 40-80°C (313-353 K) at 1.6 MPa for an initial molar ratio of ethanol to isobutene ranging from 1 to 1.5. To reach etherification equilibrium a macroporous sulphonic acid resin (K-2631, Bayer) was used as a catalyst. The thermodynamic equilibrium constant and the enthalpy, free energy, and entropy changes are given as a temperature function. At 298 K, ΔH° = -34.8 kj mol^-1, ΔG° = -11.7kJmol^-1, and ΔS° = -77.3J mol^-1 K^-1. A comparison with the values obtained for MTBE is also included.     

Dilute solution properties of carboxymethylchitins in high ionic-strength solvent

The hydrodynamic characteristics in aqueous solution at ionic strength I=0.2  of carboxymethylchitins of different degrees of chemical substitution have been determined. Experimental values varied over the following ranges: the translational diffusion coefficient (at 25.0°C), 1.1<10⁷×D<2.9 cm² s⁻¹; the sedimentation coefficient, 2.4<s<5.0 S; the Gralen coefficient (sedimentation concentration-dependence parameter), 130<k_s<680 mL g⁻¹; the intrinsic viscosity, 130<[η]<550 mL g⁻¹. Combination of s with D using the Svedberg equation yielded ‘sedimentation–diffusion' molecular weights in the range 40 000<M<240 000 g mol⁻¹. The corresponding Mark–Houwink–Kuhn–Sakurada (MHKS) relationships between the molecular weight and s, D and [η] were: [η]=5.58×10⁻³ M^0.94; D=1.87×10⁻⁴ M^−0.60; s=4.10×10⁻¹⁵ M^0.39. The equilibrium rigidity and hydrodynamic diameter of the carboxymethylchitin polymer chain is also investigated on the basis of wormlike coil theory without excluded volume effects. The significance of the Gralen k_s values for these substances is discussed.     

活性炭纤维对Cu2+的吸附性能研究

活性炭纤维(ACF)作为一种新型活性炭吸附材料已引起了化学家们的极大关注。孔结构分析表明:活性炭纤维的孔径分布窄,孔径比较均匀。本文以活性炭纤维作为去除水中重金属离子Cu2+的吸附剂,吸附实验表明,活性炭纤维对Cu2+的最大吸附量为148.50mg.g-1,吸附平衡时间短,当接触时间为50min时,即可达到吸附平衡,吸附过程符合Langmuir和Freundlich模型。动态吸附结果表明,活性炭纤维对Cu2+的吸附量随着流速的增加而降低。     

Synthesis of a novel functional group-bridged magnetized bentonite adsorbent:Characterization,kinetics, isotherm,thermodynamics and regeneration

A novel magnetic adsorbent was synthesized by magnetizing bentonite by APTES-Fe_3O_4 via a functional groupbridged interaction. The characterization of APTES-Fe_3O_4/bentonite was conducted via transmission electron microscope(TEM), X-ray diffraction(XRD), Fourier transform infrared spectrophotometer(FT-IR), thermal gravimetric analysis(TGA), vibrating sample magnetometer(VSM), zeta potential analysis and Brunner–Emmet–Teller(BET). The APTES-Fe_3O_4/bentonite was assessed as adsorbents for methylene blue(MB) with a high adsorption capacity(91.83 mg·g~(-1)). Factors affecting the adsorption of MB(such as p H, equilibrium time, temperature and initial concentration) were investigated. The adsorption process completely reaches equilibrium after 120 min and the maximum sorption is achieved at p H 8.0. The adsorption trend follows the pseudosecond order kinetics model. The adsorption data gives good fits with Langmuir isotherm model. The parameter factor RLfalls between 0 and 1, indicating the adsorption of MB is favorable. The adsorption process is endothermic with positive ΔH~0 values. The positive values of ΔG~0 confirm the affinity of the adsorbent towards MB, and suggest an increased randomness at the solid–liquid interface during the adsorption process. Regeneration of the saturated adsorbent was easily carried out via gamma-irradiation.     

Microporous activated carbon prepared from coconut shells using chemical activation with zinc chloride

Microporous activated carbon samples were prepared from coconut shells (low-cost lignocellulose waste), using chemical activation with zinc chloride followed by physical activation. Textural characterization was performed using nitrogen adsorption at 77 K. The sample that presented the best characterization results was then evaluated for methane adsorption at pressures between 0.1 MPa and 7 MPa and temperatures in the range 283–333 K. At 298 K and 40 bar, a capacity of ca. 122 mg of methane/g of carbon (80 v/v) was observed, just short of the target established in Brazil for ANG in remote sites transportation (100 v/v). These results suggest that activated carbons prepared from coconut shells, using chemical activation followed by physical activation, may be further developed as potential adsorbents for natural gas storage applications.     

Conversion of Malaysian low-rank coal to mesoporous activated carbon: Structure characterization and adsorption properties

Malaysian Selantik low-rank coal (SC) was used as a precursor to prepare a form of mesoporous activated carbon (SC-AC) with greater surface area (SA) via a microwave induced KOH-activation method. The characteristics of the SC and SC-AC were evaluated by the iodine number, ash content, bulk density, and moisture content. The structure and surface characterization was carried out using pore structure analysis (BET), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), elemental analysis (CHNS), thermogravimetric analysis (TGA), and determination of the point of zero charge (pH_PZC). These results signify a mesoporous structure of SC-AC with an increase of ca. 1160 times (BET SA=1094.3 m²·g^-1) as compared with raw SC without activation (BET SA=1.23 m²·g^-1). The adsorptive properties of the SC-AC with methylene blue (MB) was carried out at variable adsorbent dose (0.2-1.6 g·L^-1), solution pH (2-12), initial MB concentrations (25-400 mg·L^-1), and contact time (0-290 min) using batch mode operation. The kinetic profiles follow pseudo-second order kinetics and the equilibrium uptake of MB conforms to the Langmuir model with a maximum monolayer adsorption capacity of 491.7 mg·g^-1 at 303 K. Thermodynamic functions revealed a spontaneous endothermic adsorption process. The mechanism of adsorption included mainly electrostatic attractions, hydrogen bonding interaction, and π-π stacking interaction. This work shows that Malaysian Selantik low-rank coal is a promising precursor for the production of low-cost and efficient mesoporous activated carbon with substantive surface area.     

改性活性碳纤维对CO2的吸附性能

为了进一步提高活性碳纤维的CO₂吸附量和抗水性能,采用浸渍法将活性碳纤维进行改性处理,得到一系列改性样品,并对其进行了SEM和FTIR表征。研究了活性碳纤维种类、浸渍试剂（NaOH溶液、ZnCl₂溶液及离子液体）等对吸附剂孔结构、CO₂吸附量、循环使用性和抗水性能的影响,并探讨了CO₂在改性活性碳纤维内的动力学吸附扩散行为。研究结果表明：改性活性碳纤维的CO₂吸附性能和抗水性能均显著改善,其中CO₂最高吸附量达24.4%（0.1MPa和25℃）,吸湿率减小到1.33%,且具有良好的吸附/脱附循环使用性。均相扩散模型（HSDM）描述了实时吸附数据,此模型能够较好地反映CO₂在样品内的扩散行为,改性活性碳纤维仍能保持良好的扩散速率,扩散系数D_s值数量级为10^-5m²/s,与空白活性碳纤维相当。     

Lipid adsorption capacities of magnesium silicate and activated carbon prepared from the same rice hull

This study is a comparison of the lipid adsorption capacities of synthetic magnesium silicate and activated carbon produced from rice hulls of the same origin. The lipids examined were the free fatty acids, diacylglycerols and monoacylglycerols of frying oils. Pure oleic acid, an unused sunflower frying oil and a used sunflower frying oil were used in the experiments. The produced adsorbents, magnesium silicate and activated carbon, have surface areas of 680 and 43 m²/g, respectively. The lipid adsorption capacity of the produced magnesium silicate was found as 644 mg polar compounds/g adsorbent and it is higher than the capacities of the industrial adsorbents, Magnesol XL and activated carbon. This value is only 368 mg polar compounds/g adsorbent for the activated carbon produced from the same‐origin rice hull.     

黏胶基活性碳纤维吸附吡啶

采用黏胶基活性碳纤维(rayon-based ACF)吸附焦化尾水中的典型有机物吡啶, 考察了在不同时间、投加量、温度以及有机物影响的条件下, 黏胶基活性碳纤维对吡啶的静态吸附效果。从动力学、热力学和分子结构等方面来判断吸附类型, 并从理论上分析黏胶基活性碳纤维对模拟焦化尾水典型有机污染物的吸附过程。实验结果表明, 当吡啶废水的初始浓度为25mg/L时, 黏胶基活性碳纤维对吡啶的吸附在60min基本达到平衡, 最大吸附量为17.66mg/g;随着温度的升高, 吸附效率下降;共存有机物喹啉会抑制吡啶的吸附效率, 使黏胶基活性碳纤维对吡啶的吸附率显著降低;活性碳纤维吸附吡啶的过程符合Lagergren准二级动力学模型, 其相关系 数>0.999, 在22℃的液相温度下, 吸附等温式为q=2.3138c_e^0.9540。热力学参数ΔH⁰、ΔG⁰均为负值, 表明该吸附是一个自发的放热过程。     

Separation of Toxic Organotin Compounds from Aqueous Solution by Adsorption

Abstract

The adsorption characteristics of organotin compound (tributyltin oxide) are established on activated carbons, polymeric adsorbent, and synthetic carbonaceous adsorbents. Maximum adsorptive capacity is obtained with activated carbon containing high percentage of macropores (100–500 Å). For this carbon the adsorptive capacity (g organotin adsorbed/g of adsorbent) at breakpoint is 0.30 and the capacity at exhaustion (with 30 mg/L organotin solution) is 0.50.     

活性炭-疏水硅胶复合吸附剂吸附油气

开发出一种上层为活性炭、底层为疏水硅胶的复合吸附剂,并与活性炭、硅胶单独吸附汽油蒸气进行比较,发现不同吸附剂及油气质量浓度对吸附容量及吸附热有大的影响。研究活性炭与硅胶不同体积比对吸附质量比和温度的影响,得出最佳体积比为1∶1。这样高质量浓度油气先被底层的硅胶吸附,低质量浓度的油气再被上层的活性炭吸附,从而综合利用了硅胶的不燃烧及活性炭吸附质量比高的特点,从工艺技术上降低了活性炭吸附放热的安全问题,进而还可适当提高活性炭有效吸附容量。