Phosphate adsorption characteristics of alunite to be used as a cement additive

The adsorption of phosphate from aqueous solution by alunite has been investigated as a function of calcination temperature, particle size, pH, agitation time and initial phosphate concentration. Phosphate adsorption was seen to increase with increasing calcination temperature, decreasing adsorbent particle size and pH. The adsorption isotherm data were fitted to the Langmuir isotherm. The alunite exhibited the highest phosphate uptake capacity at 1073 K calcination temperature, at a particle size of 90-150 μm, at the initial pH of 5.0, at an equilibrium time of 60 min and at the initial phosphate concentration of 20×10⁻⁴ mol/l. The adsorption capacity, Q, was 4.697×10⁻³ mol/g at initial pH 5.0.     

Adsorption behaviors of mercury from aqueous solution using sulfur-impregnated adsorbent developed from coal

Adsorption of mercury from aqueous solution on sulfur-impregnated adsorbent has been studied. Raw coal was mixed with K₂S powder, and then heated at 800-1000 °C for 30 min in nitrogen to produce sulfur-impregnated adsorbent. The sulfur content and specific surface area of the adsorbent were determined, and the ability of the adsorbent to adsorb mercury in aqueous solution was examined. With increasing temperature of sulfur-impregnation, specific surface area of the adsorbent increases, while sulfur content of the adsorbent is almost constant. The adsorbent obtained at 900 °C shows the highest and fastest adsorption of mercury from aqueous solution at 25 °C, and the elution extents of adsorbed mercury are negligible in distilled water and 10% in 0.1 M HCl solution, respectively. Adsorption kinetics was tested for pseudo-first order and pseudo-second order reactions, and the rate constants of adsorption for these kinetic models were calculated. Adsorption experiments demonstrate that the adsorption process corresponds to pseudo-second-order kinetic model than pseudo-first-order model. With increasing temperature of aqueous solution, the kinetics of adsorption becomes faster and the amount of mercury adsorbed on the adsorbent increases. The thermodynamic values, ΔG⁰, ΔH⁰ and ΔS⁰, indicated that adsorption was an endothermic and spontaneous process.     

Li2O-CaO吸附剂吸附CO2的性能

采用机械混合法制备了Li2O-CaO吸附剂,在固定床管式反应器中研究了Li2O-CaO吸附剂的吸附性能,考察了吸附温度、空速及吸附剂粒径对静吸附容量的影响,确定了适宜的工艺条件,采用XRD和SEM对改进的钙基吸附剂进行了表征。结果表明,Li2O-CaO吸附剂对CO2有较好的吸附能力,在吸附温度600℃、空速8min-1、吸附剂粒径60～80目(0.18～0.28 mm)的条件下,静吸附容量达到了17.3891 mol/kg。     

The influence of adsorbent texture and adsorbate type on analytical functions describing the heterogeneity of active carbons surfaces

Analytical functions describing the heterogeneity of active carbons have been studied in relation to adsorbate type and adsorbent texture. It has been found that the maximum in the distribution functions shifts to higher energies with an increase in adsorbent microporosity. The position of the maximum on the curve determining active carbon heterogeneity is closely correlated with the value of the B parameter in the Dubinin-Astakhov equation. It has been shown that the shape and magnitude of the analytical functions studied depend on the type of adsorbate molecules bonded on the adsorbent surface.     

Use of Clinoptilolite in Ethanol Dehydration

Abstract

Clinoptilolite-type natural zeolite, which exists in various regions of Turkey, has been experimentally studied. For the ethanol-water-local clinoptilolite system, uptake and breakthrough curves were determined under a nitrogen gas atmosphere. In adsorption kinetics and adsorption equilibrium studies, the effects of particle size, temperature and, amount of zeolite on the uptake rate have been investigated. The breakthrough curves for four different flow rates of ethanol and three different bed heights were determined in dynamic column studies. The results of the experiments show that intraparticle diffusion is the main resistance. The local clinoptilolite is a promising adsorbent for water adsorption from aqueous ethanol.     

Synthesis of an affinity adsorbent based on silica gel and its application in endotoxin removal

An affinity media for endotoxin removal based on silica gel was prepared by activation with silane coupling agent and subsequent conjugation with histidine (His) as a ligand. The influence of pore size and particle dimension of the silica gel and the grafting conditions such as reaction temperature and concentration of His in solution on the grafting yield of His were studied by means of IR, thermogravimetric analysis and elemental analysis. The results show that the silica gel with a particle size of 200 μm and a pore size of about 12 nm was a good carrier material for the preparation of the affinity adsorbent. Under the optimal conditions, histidine was covalently immobilized on silica gel at about 20 mg/g, with a corresponding maximum endotoxin adsorption capacity q_m in contaminated water of about 1.2 mg/g and an apparent dissociation constant K_d of about 1350 μg/L. The adsorbent had little nonspecific adsorption from a protein-containing solution.     

Peat adsorption of herbicide 2,4-D from wastewaters

The possibility of utilizing peat as adsorbent for removal of the pesticide 2,4-D from contaminated wastewaters has been evaluated in this investigation. Batch tests were conducted at different conditions of initial solute concentration, pH, particle size of adsorbent, temperature and ratios of weight of adsorbent to solution volume, in order to determine the optimum range of these variables for the adsorption operation. Removal ratios for the 2,4-D of the order of 90% were obtained under optimum conditions. The adsorption of 2,4-D in peat is described adequately by the Freundlich isotherm. Continuous tests, utilizing adsorption columns, were then conducted in order to determine the design parameters for a proposed treatment plant. The column tests were adequately correlated by the Bohart-Adams equation.     

复合吸附剂的基质选择与动态吸附性能测试

用不同类型的粗孔硅胶与氯化锂盐复合制备了一系列复合吸附剂。测量了它们的含盐量,并观察其腐蚀性。对纯硅胶与复合吸附剂的孔结构进行分析。测试了纯硅胶和复合吸附剂吸附水蒸气的性能等。实验证明,作为复合吸附剂的基质,不同类型的硅胶对复合的吸附剂影响很大。纯硅胶中,粗孔粒度为0.5～1.5 mm的硅胶吸附性能相对最好,但吸附量很小;复合吸附剂中,微球粗孔硅胶以及片状大孔硅胶虽然吸附量得到了大大的提高,但不易液解表面的氯化盐,将导致复合吸附剂膨胀结块影响传质通道,并腐蚀吸附床。大于2 mm的粗孔硅胶复合了氯化盐后,吸水产生毛细力将撑破硅胶骨架。因此,最适合复合吸附应用的硅胶基质为小颗粒耐水硅胶。在复合氯化盐后,吸水性能有了很大提高。同时,长时间循环吸附不会造成硅胶粉碎。     

Comparison of removal of bromothymol blue from aqueous solution by multiwalled carbon nanotube and Zn(OH)2 nanoparticles loaded on activated carbon: A thermodynamic study

In this research Zn(OH)₂ nanoparticles loaded on activated carbon (Zn(OH)₂-NPs-AC) as novel adsorbent and raw multiwalled carbon nanotube (MWCNT) were applied for efficient removal of bromothymol blue (BTB). Both adsorbent has been characterized with different techniques such and SEM, XRD and UV–vis spectrometry. Their size was less than 100 nm. In the removal process the variables are pH, temperature, concentration of BTB, amount of adsorbent and contact time that their influence on removal of BTB was optimized using one at a time approach in batch procedure. Adsorptions of BTB on bath adsorbent depend highly on pH. Following the investigation of temperature effect, the thermodynamic parameters including change in entropy, enthalpy and free Gibbs energy were calculated. For both adsorbents, positive value of enthalpy and negative value of ΔG⁰ show routine feasibility of adsorption using energy. At optimum value of variables, the removal processes onto both adsorbent have high adsorption capacity for best fitting model Langmuir, i.e. for Zn(OH)2-NP-AC and 150 mg/g for PAC. The adsorption rates were well explained with pseudo second order and interparticle diffusion model. It is expected that there could an increase in the number of reactive sites due to their expected high volume, pore size and high surface area.     

Application of the concentration-dependent surface diffusion model on the multicomponent fixed-bed adsorption systems

The ability of bone char to adsorb three metal ions, namely, cadmium, copper and zinc, from effluents in fixed beds has been studied. Two binary metal ion sorption systems, Cd+Cu and Cu+Zn, have been investigated. The variables studied include metal ion solution flowrate, initial metal ion concentration, and bone char particle size bed height. The experimental breakthrough curves for each binary system were measured at five bed heights.A multicomponent film-surface diffusion model has been developed to predict the breakthrough curves by incorporating the IAS for both the Langmuir and the Sips equations, since they both correlate the single component equilibrium isotherm data well. A novel development is the modification of the solution methodology, previously restricted to a constant diffusivity, to incorporate a variable diffusivity correlated with adsorbent coverage by the constant self-diffusivity. The self-diffusivities for the metal ions have been evaluated.     

Study of adsorption isotherms and kinetic models for Methylene Blue adsorption on activated carbon developed from Egyptian rice hull (Part II)

Adsorption of Methylene Blue (MB) from aqueous solutions on activated carbon prepared from Egyptian rice hulls (ERHA) is studied experimentally. Results obtained indicate that the removal efficiency of Methylene Blue at 25 °C exceeds 99% and that the adsorption process is highly pH-dependent. Results showed that the optimum pH lies between 5 and 9. The amount of Methylene Blue adsorbed form aqueous solution increases with the increase of the initial Methylene Blue concentration and temperature. Smaller adsorbent particle adds to increase the percentage removal of Methylene Blue.The results fit the BET model for adsorption of MB on ERHA, corroborating the assumption of that the adsorbate molecules could be adsorbed in more than one layer thick on the surface of the adsorbent.A comparison of kinetic models at different conditions (pH, Temperature, adsorbent particle size, adsorbent dose and adsorbate concentration) applied to the adsorption of Methylene Blue on the adsorbent was evaluated for the pseudo first-order, the pseudo second-order, Elovich and intraparticle diffusion kinetic models, respectively. Results showed that the pseudo second-order kinetic model correlate the experimental data well.     

New Adsorption Cycle for Upgrading the Ambient Heat

Adsorption (chemical) heat transformation (AHT) is a new energy conservation and environmentally friendly technology that allows efficient use of heat sources with low temperature potential. Recently, a new cycle, called “Heat from Cold” (or HeCol) has been proposed to upgrade the temperature potential of the ambient heat. In the HeCol cycle, a natural reservoir of water with a temperature above 0°C is used as a heat source, and ambient air at T = (–20)–(–50)°C as a heat sink. The cycle is designed to produce heat at a temperature of 30–50°C, which can be used for heating of dwellings. The aim of this work is to select the adsorbent for the HeCol cycle and to test the laboratory prototype with the selected adsorbent. The work consists of three parts: (a) formulation of requirements to adsorbent, specialized for the HeCol cycles under various conditions; (b) analysis of data on adsorption equilibrium of commercial activated carbons and selection among them the materials suitable for the new cycle; and c) study of the laboratory prototype HeCol with the chosen adsorbent to analyze the feasibility of the new cycle. The main findings of this study are (i) the experimental demonstration of the HeCol cycle feasibility and (ii) the achievement of the specific heat generation power 8 kW/kg, which is of practical interest.     

Effect of particle size distribution on adsorption kinetics in stirred batch systems

The effect of different particle size distributions (PSD's) on kinetic behavior in stirred-batch adsorption systems was investigated by numerically modeling the uptake of p-nitrophenol from aqueous solution by granular activated carbon in a well-stirred batch type of environment. Four different Gaussian PSD'S, two different log-normal PSD's and one case of uniform particle size were studied. The model accounted for both external and internal mass transfer resistances, and for the highly nonlinear equilibrium relation which characterizes the p-nitrophenol/activated carbon system. All isotherm parameters and “base-case” kinetic parameters were experimentally determined values (from the literature). The kinetic parameter values were varied in some cases to assess their influence. Moreover, both infinite-bath and finite-bath situations were evaluated. The modeling results show that the different particle size distributions did not generally give kinetic behavior widely different from the uniform particle size case when an infinite bath was assumed. However, for the more realistic case of a finite bath, the different PSD's gave significantly more distinctive results, especially for fractional mass uptake values greater than about 0.7. It is concluded that, in finite bath experiments, the nature of the adsorbent PSD must be accounted for in interpreting data obtained at fractional mass uptake values greater than about 0.7, unless the adsorbent PSD is reasonably nar     

Mercury (II) adsorption by activated carbon made from sago waste

The preparation of activated carbon (AC) from sago industry waste is a promising way to produce a useful adsorbent for Hg (II) removal, as well as dispose of sago industry waste. The AC was prepared using sago industry waste with H₂SO₄ and (NH₄)₂S₂O₈ and physico-chemical properties of AC were investigated. Adsorptive removal of mercury (II) from aqueous solution onto AC prepared from sago industry waste has been studied under varying conditions of agitation time, metal ion concentration, adsorbent dose, particle size and pH to assess the kinetic and equilibrium parameters. Adsorption equilibrium was obtained in 105 min for 20 mg l⁻¹ and 120 min for 30, 40, and 50 mg l⁻¹ Hg (II) concentrations. The Langmuir and Freundlich equilibrium isotherm models were found to provide an excellent fitting of the adsorption data, with r² 0.9999 and 0.9839, respectively. The adsorption capacity of Hg (II) (Q_o) obtained from the Langmuir equilibrium isotherm model was found to be 55.6 mg g⁻¹ at pH 5.0 for the particle size range of 125-250 μm. The percent removal increased with an increase in pH from 2 to 10. This adsorbent was found to be effective and economically attractive.     

Effect of elevated temperature and silica sand particle size on minimum fluidization velocity in an atmospheric bubbling fluidized bed

The impact of temperature and particle size on minimum fluidizing velocity was studied and analyzed in a small pilot scale of bubbling fluidized bed reactor. This study was devoted to providing some data about fluidization to the literature under high temperature conditions. The experiments were carried out to evaluate the minimum fluidizing velocity over a vast range of temperature levels from 20 °C to 850 °C using silica sand with a particle size of 300–425 μm, 425–500 μm, 500–600 μm, and 600–710 μm. Furthermore, the variation in the minimum fluidized voidage was determined experimentally at the same conditions. The experimental data revealed that the U_mf directly varied with particle size and inversely with temperature, while ε_mf increases slightly with temperature based on the measurements of height at incipient fluidization. However, for all particle sizes used in this test, temperatures above 700 °C has a marginal effect on U_mf. The results were compared with many empirical equations, and it was found that the experimental result is still in an acceptable range of empirical equations used. In which, our findings are not well predicted by the widely accepted correlations reported in the literature. Therefore, a new predicted equation has been developed that also accounts for the affecting of mean particle size in addition to other parameters. A good mean relative deviation of 5.473% between the experimental data and the predicted values was estimated from the correlation of the effective dimensionless group. Furthermore, the experimental work revealed that the minimum fluidizing velocity was not affected by the height of the bed even at high temperature.     

Uses of Ozone in a Three-Phase System for Water Treatment: Ozone Adsorption

A new technique of using ozone for water treatment is presented. This new technique consists of using a three-step-process composed firstly of ozone adsorption on an appropriate adsorbent, secondly water treatment, and thirdly regeneration of the adsorbent. Results regarding ozone adsorption (the first step) are presented in this paper. Different types of silica gel and a type of TiO₂ have been tested for ozone adsorption. It was found that the physical characteristics of the silica gel affect its capacity for ozone. Titanium dioxide has shown ozone decomposition instead of adsorption as it contains Lewis acid sites. An exponential decrease of the silica gel capacity with its moisture content has been found. Linear isotherms in the range of ozone concentrations less than 100?g/m³ NTP have been found. A particle diffusion model with linear equilibrium isotherm has been used to model the breakthrough curves in fixed bed columns.     

盐湖铝系提锂吸附剂成型条件的影响研究

铝系锂吸附剂成型颗粒在盐湖卤水提锂工业应用过程中存在吸附容量低、吸附速率慢和吸附剂粉末脱落等问题。基于现有反溶剂法挤压成型工艺,对盐湖铝系提锂吸附剂成型条件的影响进行了系统性研究。实验结果显示吸附剂成型颗粒粒径越小,达到吸附平衡越快,当颗粒直径d<1 mm时,吸附剂颗粒可在24 h左右达到吸附平衡;降低黏结剂浓度可有效加快吸附剂颗粒的吸附速率,但黏结剂浓度过低会导致其对粉末的包裹性下降;吸附剂颗粒的吸附速率与致孔剂添加比例成正比,当致孔剂添加比例为20%时,吸附剂颗粒能在4 h内完成快速吸附阶段,吸附平衡时对察尔汗高镁锂比盐湖卤水中锂的吸附容量可达4.97 mg·g^-1。     

天然沸石颗粒吸附剂对Cr3+的吸附性能及再生研究

将天然沸石粉与易燃微粉按一定比例混合,挤压造粒,灼烧成多孔质天然沸石颗粒吸附剂,然后用于吸附Cr3 .试验了溶液pH、Cr3 初始质量浓度和吸附时间等因素对吸附性能的影响,绘制的吸附等温线近似符合Freundlich吸附等温方程.     

Factors Affecting on the Sorption/Desorption of Eu (III) using Activated Carbon

Abstract

The sorption and desorption of Eu (III) on H‐APC activated carbon using a batch technique has been studied as a function of carbon type, shaking time, initial pH solution, temperature, particle size of carbon, and concentration of the adsorbent and the adsorbate. The influence of different anions and cations on adsorption has been examined. The experimental data have been analyzed by Langmuir, Freundlich, and Temkin sorption isotherm models and the adsorption data for Eu (III) onto activated carbon were better correlated to the Temkin isotherm and the maximum absorption capacities obtained was 46.5 mg g^?1. Anions of phosphate, carbonate, oxalate, and acetate were found to increase the adsorption of Eu (III), whereas nitrate, chloride and all studied cations, potassium, sodium, calcium, magnesium, and aluminum have a negative effect on the adsorption capacity. More than 99% europium adsorbed on H‐APC eluted with 0.5 M HCl solution. The activated carbon prepared from apricot stone using 70% H₃PO₄ could be considered as an adsorbent that has a commercial potential for Eu (III) treatment.     

The adsorption of dyestuffs from aqueous solutions using activated carbon. iv. external mass transfer processes

The parameters affecting the mass transfer coefficients for external transport of dyes from water on to activated carbon particles have been studied. The external mass transfer coefficients have been determined and correlated as the dimensionless mass transfer term, Sh/Sc^0.33. The dimensionless function has been found to vary linearly with agitation, initial dye concentration, particle size, adsorbent mass on log-log coordinates, while reciprocal variation was obtained with absolute temperature. Activation energies were determined for the surface process, for the adsorption of Deorlene Yellow, Victoria Blue, Telon Blue and Disperse Blue 7 and found to be 26.5, 24.5. 25.4 and 74.6 kJ mol^-l respectively.