Adsorption of cadmium from aqueous solution by phosphogypsum

In the present study, the adsorption of cadmium on phosphogypsum, a waste material from the manufacture of phosphoric acid by wet process, was studied. Before batch adsorption study, phosphogypsum was pre-conditioned by milk of lime. Effect of initial pH on cadmium adsorption was investigated. It was found that cadmium adsorption was dependent on solution pH and maximum cadmium removal was observed in the pH range of 9.5 and 11.5. The Langmuir and Freundlich theories were used to describe the cadmium adsorption process, and the Freundlich isotherm showed the best fit to the process. Maximum adsorption capacity of lime-preconditioned phosphogypsum was found to be 131.58 mg/g.     

The use of low rank coal-based adsorbents for the removal of nitrophenol from aqueous solution

A range of Victorian brown coal based materials (Yallourn brown coal, grus, briquette char, power station char and an activated carbon) have been assessed as potential adsorbents for the removal of organics from aqueous wastes. The compound 4-nitrophenol has been used as the adsorbate. The influence of adsorbent dosage levels, particle size, and the presence of buffer solution components, other electrolytes, and pH on the kinetics of adsorption of nitrophenol have been investigated. For some adsorbents, pH changes in the acidic region appear to have little influence on adsorption rates of nitrophenol, but for chars, reduced pH conditions appear to reduce adsorption rates. In the alkaline pH range, leaching from some of the adsorbents occurs, with the extent of leaching reducing as the carbon content of the adsorbent increases. Adsorption capacities for Yallourn coal, grus, briquette char and power station char using nitrophenol in phosphate buffer have been measured. The technique of differential pulse polarography has been shown to be useful as a means of measuring nitrophenol adsorption in situ for concentrations up to 30 mg l⁻¹.     

Adsorption of alcohols from aqueous solution by ZSM-5

Isotherms have been measured for the adsorption from aqueous solution of water soluble alcohols onto the zeolite ZSM-5. For methanol and ethanol the amount of alcohol adsorbed increases with increasing percentage of Al₂O₃, whereas for n-butanol the amount adsorbed decreases as the amount of Al₂O₃ increases. Adsorption of alcohols is also dependent on the cation form. For the alkali metal ion forms, the amount of alcohol adsorbed decreases as the ionic size increases, the effect being particularly pronounced for Cs⁺. Subsequent alcohol desorption was studied by thermogravimetry and mass spectrometry which showed that the zeolite retained a portion of the alcohol to temperatures (ca 250°C) sufficiently high that catalytic breakdown occurred. This reduces its likely potential for commercial alcohol concentration.     

Adsorption of chromium by activated carbon from aqueous solution

Adsorption isotherms of Cr(III) and Cr(VI) ions on two samples of activated carbon fibres and two samples of granulated activated carbons from aqueous solutions in the concentration range 20–1000 mg/l have been studied. The adsorption isotherms have been determined after modifying the activated carbon surfaces by oxidation with nitric acid, ammonium persulphate, hydrogen peroxide and oxygen gas at 350°C and after degassing at different temperatures. The adsorption of Cr(III) ions increases on oxidation and decreases on degassing. On the other hand, the adsorption of Cr(VI) ions decreases on oxidation and increases on degassing. The increase of Cr(III) and the decrease of Cr(VI) on oxidation and the decrease of Cr(III) and the increase of Cr(VI) on degassing have been attributed to the fact that the oxidation of the carbon surface enhances the amount of acidic carbon–oxygen surface groups while degassing eliminates these surface groups. Thus while the presence of acidic surface groups enhances the adsorption of Cr(III) cations, it suppresses the adsorption of Cr(VI) anions.     

Removal of arsenic(III) from aqueous solution by concrete-based adsorbents

The present paper investigates the adsorption of arsenic(III) (As(III)) onto 2 concrete-based low-cost materials, i.e., Aerocrete and Vermiculite impregnated by ferric oxyhydroxide. Adsorption experiments were performed to study the effect of initial pH, initial concentration of As(III), contact time, and ions usually present in water. No significant effect of the initial pH on the adsorption of As(III) by Aerocrete and Vermiculite was observed at the pH range of 4–8. The As(III) removal efficiency decreased at a high initial pH (i.e., 10). The Langmuir isotherm showed that the maximum As(III) adsorption capacity of Aerocrete and Vermiculite is 15.15 and 13.51 mg/g, respectively, which is higher than that observed using titanium dioxide (i.e., 3.52 mg/g), at pH 7 and 24 ±1 °C. A pseudo-second order kinetic model fitted well the experimentally obtained kinetic data. This suggests that chemisorption most probably controls the adsorption of As(III) on Aeroctere and Vermiculite. Significantly, As(III) (1 mg/L) could be removed almost completely by both Aeroctere and Vermiculite (1 g/L) in 30 and 60 min, respectively at pH 7 and 24 ±1 °C. Importantly, Ca²⁺, Mg²⁺, Na⁺, HCO₃⁻, SO₄²⁻, and Cl⁻ ions had no significant effect on the adsorption of As(III) on Aeroctere and Vermiculite. The results showed that the proposed concrete-based adsorbents have the potential to remove As(III) from water.     

活性碳纤维吸附水溶液中的二价铅离子

对活性碳纤维(ACF)吸附水溶液中的二价铅离子进行研究。分别运用静态和动态方法来考察ACF吸附Pb^2 的性能，测定了吸附等温线，探讨了吸附时间、DH值等因素对吸附的影响，并进行了ACF的再生实验。结果表明，ACF对水中二价铅离子的吸附特性良好，且吸附剂易于再生，可作为去除水中离子态重金属的优良吸附剂。     

Improved phenol adsorption from aqueous solution using electrically conducting adsorbents

The electrically conducting and partially porous graphite based adsorbent (called NyexTM 2000) was tested for its adsorption capacity and electrochemical regeneration ability for the removal of phenol from aqueous solution. Nyex? 2000 was tested in comparison with Nyex? 1000, which is currently being used for a number of industrial waste water treatment applications. Nyex? 1000 exhibited small adsorption capacity of 0.1 mg g^?1 for phenol because of having small specific surface area of 1 m² g^?1. In contrast, Nyex? 2000 with specific surface area of 17 m² g^?1 delivered an adsorption capacity of 0.8 mg g^?1, which was eight-fold higher than that of Nyex? 1000. Nyex? 2000 was successfully electrochemically regenerated by passing a current of 0.5 A, charge passed of 31 C g^?1 for a treatment time of 45 minutes. These electrochemical parameters were comparable to Nyex? 1000 for which a current of 0.5 A, charge passed of 5 C g^?1 for a treatment time of 20 minutes were applied for complete oxidation of adsorbed phenol. The comparatively high charge density was found to be required for Nyex? 2000, which is justified with its higher adsorption capacity. The FTIR results validated the mineralization of adsorbed phenol into CO₂ and H₂O except the formation of few by-products, which were in traces when compared with the concentration of phenol removed from aqueous solution. The electrical energy as required for electrochemical oxidation of phenol adsorbed onto Nyex? 1000 & 2000 was found to be 214 and 196 J mg^?1, respectively. The comparatively low energy requirement for electrochemical oxidation using Nyex? 2000 is consistent with its higher bed electrical conductivity, which is twice that of Nyex? 1000.     

Acid Black 172 dye adsorption from aqueous solution by hydroxyapatite as low-cost adsorbent

The Acid Black 172 dye adsorption on the uncalcined hydroxyapatite nanopowder was investigated. The hydroxyapatite prepared by wet coprecipitation method has high specific surface area of 325 m²/g and crystal sizes smaller than 70 nm. The batch adsorption experiments revealed that under the optimum adsorption conditions (pH 3, hydroxyapatite dosage 2 g/L, initial dye concentration 400 mg/L and temperature 20 °C) the dye removal efficiency was 95.78% after 1 h of adsorption. The adsorption kinetics was best described by the pseudo-second order kinetic model. The intraparticle diffusion model shows that intraparticle diffusion is not the sole rate-limiting step; the mass transfer also influences the adsorption process in its initial period. The Langmuir isotherm model best represented the equilibrium experimental data, and the maximum adsorption capacity (q _m ) was 312.5 mg/g.     

Adsorption of methylene blue from aqueous solution by kaolin and zeolite

In the present study, kaolin and zeolite have been utilized as adsorbents for the removal of a cationic dye, methylene blue (MB), from aqueous solution within a batch process. Characterization of the two adsorbents was carried out by nitrogen adsorption–desorption experiments (specific surface area measurements by the BET method). The effects of various parameters such as initial MB concentration, contact time, adsorbent concentration, stirring speed, solution pH and salt concentration were examined and optimal experimental conditions were determined. The kinetic data were analyzed using pseudo-first-order and pseudo-second-order models. The mass transfer model in terms of interlayer diffusion was applied to the experimental data to examine the mechanisms of the rate controlling step. In order to determine the best-fit-isotherm, the experimental data were analyzed by the Freundlich, Temkin, and Dubinin–Radushkevich equation which are found to best represent the equilibrium data for kaolin and zeolite. The values of activation parameters such as free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) were also determined. The results indicate that kaolin and zeolite could be interesting alternative materials with respect to more costly adsorbents used for dye removal.     

Adsorption of heavy metal ions from aqueous solution by fly ash

The removal characteristics of lead and copper ions from aqueous solution by fly ash were investigated under various conditions of contact time, pH and temperature. The influence of pH of the metal ion solutions on the uptake levels of the metal ions by fly ash were carried out between pH 4 and 12. The level of uptake of Pb²⁺ and Cu²⁺ ions by the fly ash generally increased, but not in a progressive manner, at higher pH values. The effect of temperature on the uptake of Pb²⁺ and Cu²⁺ ions was investigated between 30 °C and 60 °C, the adsorption of being enhanced at the lowest temperature. Rate constants were evaluated in terms of a first-order kinetics. The rate constant, k for uptake of Pb²⁺ and Cu²⁺ ions were 1.77 × 10⁻² s⁻¹ and 2.11 × 10⁻² s⁻¹, respectively. The experimental results underline the potential of coal fly ash for the recovery of metal ions from waste water. The main mechanisms involved in the removal of heavy metal ions from solution were adsorption at the surface of the fly ash and precipitation.     

氧化改性橡椀单宁对铜离子溶液的吸附性

以橡椀栲胶为原料,通过双氧水氧化降解改性,研究水解类橡椀单宁改性后对铜离子溶液的吸附沉淀以及pH值、金属溶液初始浓度对铜离子吸附沉淀容量的影响和规律。结果表明,氧化橡椀单宁对Cu2+的吸附平衡符合Freundlich方程。改性后吸附沉淀容量受初始浓度影响较大,初始浓度为20 mg/L时基本不发生吸附沉淀,试验最大初始浓度100 mg/L时吸附量达到39.300 mg/g。     

高炉渣吸附亚甲基蓝的性能研究

以高炉渣为吸附剂,探讨了高炉渣用量、吸附pH值、初始浓度及吸附时间等因素对亚甲基蓝的吸附性能影响.结果表明,高炉渣对亚甲基蓝的吸附过程与吸附pH值、初始浓度、吸附温度等密切相关,吸附pH值在6.0～8.0时吸附较为适宜,且高炉渣吸附亚甲基蓝在180 min即可达到吸附平衡状态.吸附等温线和吸附动力学研究表明,高炉渣吸附...     

活性炭对苯酚的吸附研究

进行了活性炭处理含苯酚废水的应用研究,考察了影响苯酚吸附效果的因素。确定了处理水中苯酚的最佳条件:吸附平衡时间为30 min;最佳pH值为6左右;苯酚初始浓度为10 mg/L;投炭量为20～25 mg/L;苯酚的吸附率高达97.4%;温度对苯酚吸附率的影响不明显。研究了活性炭对苯酚的吸附动力学特性,分别用伪一级动力学方程、伪二级动力学方程、修正伪一级动力学方程和颗粒内扩散模型进行拟合,对于不同浓度的苯酚废水都只有伪二级动力学方程拟合程度比较高,伪二级动力学方程更为真实地反映苯酚在活性炭上的吸附机理。     

Adsorption of glucose into zeolite beta from aqueous solution

Hydrophobic zeolites, including Ti‐ and Sn‐beta, have been found to adsorb and isomerize glucose into fructose. An experimental question has been the significance of the entropic contribution to the free energy of transfer of glucose from solution to zeolite. We here perform Gibbs ensemble Monte Carlo calculations to quantify the enthalpy, entropy, and free energy of transfer of glucose from the aqueous phase to the zeolite phase. We find that the entropic contribution is large and positive, nearly compensating for an unfavorable enthalpy of transfer in all‐silica zeolite beta. A significant component of the positive entropy of transfer from the aqueous phase to zeolite is the unstructuring of first coordination shell waters around glucose as it leaves the solution. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3523–3529, 2013     

Adsorption of rubidium ion from aqueous solution by surface ion imprinted materials

A new type of rubidium ion-imprinted polymer has been synthesized by the surface-imprinting technique using methacrylic acid as the functional monomer, the rubidium ion as the template, methanol as the solvent, and silica as a carrier. Ethylene glycol dimethacrylate and 2,2-azobisisobutyronitrile were used as acrosslinker and an initiator, respectively. In addition, based on the macrocyclic effect of crown ethers, the 18-crown-6 ligand was introduced as a ligand to fix the template ions better. ...     

Adsorption of saccharides from aqueous solution onto activated carbon

The Freundlich's adsorption constants of 13 saccharides and 4 polyhydric alcohols from aqueous solutions onto an activated carbon have been determined and correlated with various physical constants. A good linear relationship is obtained between the adsorption constants and the physical constant such as molecular refraction or parachor. Further, the adsorption isotherms of saccharides can be predicted from the carbon atom number and the oxygen atom number in the molecular formula.     

Adsorption of silver complexes on carbon from aqueous solution

The adsorption of silver diammine complex on graphitized carbon black has been studied in aqueous ammonia solution. The carbon black has been gasified to various levels of burnoff in order to increase its active surface area (ASA). The effect of different parameters, ASA, concentrations of silver diammine and of ammonium cations on the silver adsorption has been investigated. The metal complex interacts specifically with the active sites located in the ASA where it undergoes a reduction to metallic silver. A phenomenological model of the adsorption and decomposition reactions of the silver complex is proposed.     

NaOH改性花生壳对亚甲基蓝染料吸附性能的研究

花生壳用5%的NaOH溶液改性作吸附剂处理亚甲基蓝染料废水,考察pH值、吸附剂投加量、染料浓度和温度及吸附时间对染料吸附性能的影响。结果表明,吸附最佳的工艺条件为:温度25℃,吸附剂投加量0.3 g,亚甲基蓝的初始浓度3.5 g/mL,反应时间135 min,pH值7。此时改性花生壳对亚甲基蓝的吸附率达99.57%。     

Adsorption of lead(II) from aqueous solution by activated carbon prepared from Eichhornia

Activated carbon prepared from Eichhornia was used for the adsorptive removal of Pb(II) from aqueous solution. As the raw material for the preparation of the activated carbon is an aquatic weed, the production of this carbon is expected to be economically feasible. Parameters such as agitation time, metal ion concentration, adsorbent dose and pH were studied. Adsorption equilibrium was reached in 100 min for a solution containing 15 mgdm^?3 and 125 min for solutions containing 20 and 25 mgdm^?3 Pb(II), respectively. Adsorption parameters were determined using both Langmuir and Freundlich isotherm models. The adsorption capacity was 16.61 mgg^?1 at pH 3.0 for particle sizes of 125–180 µm. Pb(II) removal increased as the pH increased from 2 to 4 and remained constant up to pH 10.0. Desorption studies were also carried out with dilute hydrochloric acid to recover both carbon and Pb(II). Quantitative desorption of Pb(II) from carbon indicates that adsorption of metal ion is by ion exchange. © 2002 Society of Chemical Industry     

Adsorption from aqueous solution by δ-manganese dioxide I. Adsorption of the alkaline-earth cations

The adsorption isotherms of M²⁺ ions (M = Mg, Ca, Sr or Ba) were determined at pH 7.0 and at different temperatures. The adsorbent, δ-MnO₂, was converted to the K⁺ form prior to adsorption and about 1.5 mol K⁺ ions were released per mol of M²⁺ ions adsorbed. The adsorption capacity at a given temperature increased in the series: Mg²⁺ < Ca²⁺ ≦ Sr²⁺ < Ba²⁺. This was explained by an ion exchange mechanism between hydrated ions: K⁺ ions in the outer Helmholtz layer and M²⁺ ions in the bulk of the solution. The radii of the hydrated ions decreased in the series: Mg²⁺ > Ca²⁺ > Sr²⁺ > Ba²⁺. The adsorption of M²⁺ ions at pH values below the point of zero charge (pH 3.3) was significant for Mg²⁺ ions only. Although adsorption was not strictly reversible, the results fitted the Langmuir isotherm and ‘apparent heats of adsorption’, Q, were calculated. The endothermic heats (Q = 20,18, 11 and 5 kJ mol^?1 for Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺ adsorption respectively) indicated positive entropy contributions which are expected for the adsorption mechanism suggested. The decrease in Q down the alkaline-earth group was correlated to the entropy effects and to the hydration numbers of the cations.