Adsorption of urea onto granular activated alumina: A comparative study with granular activated carbon

ABSTRACT

This study investigated the ability of granular activated alumina to remove urea from wastewater through adsorption, and compared its performance with granular activated carbon. XRF, EDX, XRD, and TGA were used to investigate the adsorbents. The removal of urea as a function of pH value was studied. The point of zero charge for activated alumina was found to be 8.8, while that for activated carbon was found to be 7.1. The experimental data of the adsorption process were explored by fitting to different kinetic models to determine the adsorption kinetics and mechanisms. Then, the equilibrium data were examined by fitting to various two-parameter and three-parameter isotherm models. Results showed that the removal efficiency increased with the increasing pH value. The maximum removal efficiencies were 24% and 31% for granular activated alumina and granular activated carbon, respectively, at pH?=?9.0. Kinetic studies showed that adsorption of urea onto both activated alumina and activated carbon can be expressed by pseudo second order kinetics. Equilibrium studies showed that the adsorption isotherms could be expressed by the Redlich-Peterson isotherm and Temkin isotherm for activated alumina and activated carbon, respectively. Adsorbents were investigated using FTIR and SEM, and results showed the occurrence of adsorption.     

Adsorption of 18-crown-6 from aqueous solution on granular activated carbon: a kinetic modeling study

Granular activated carbon was used for the removal of 18-crown-6 from aqueous solution by adsorption. The influence of two experimental parameters, initial 18-crown-6 concentration and temperature, on the adsorption kinetics was evaluated. The kinetics data obtained were modeled by pseudo-first-order and pseudo-second-order models, respectively. The process of adsorption follows a pseudo-second-order rate model. The most important result of the present study is that the correlation coefficient is not a sufficient criterion for selection of a kinetic model, and therefore several criteria are suggested for its selection.     

Thermoanalytical Study of activated carbon regeneration part IV. Adsorption equilibria for phenol,aniline and their nitro-derivatives on granular activated carbon

A linear correlation between adsorptive affinity and acidic properties of adsorbates is evidenced when phenol. aniline and their o-, m-, and p-nitro-derivatives are adsorbed on granular activated carbon. Thermodesorption energies appear to be empirically related to adsorptivity.     

Adsorption kinetic modeling of toxic vapors on activated carbon in the batch reactor

Research on Chemical Intermediates - The compound ortho-chlorobenzylidene malononitrile (OCM) is the defining component of tear gas commonly referred to as CS gas. In present work, at first, OCM...     

Adsorption of dyes on activated carbon and graphitic thermal carbon black

The adsorption of a basic dye (Methylene Blue; MB) and an acidic dye (Acid Orange; AO) has been studied on three activated carbons (ACs; FAS, SKD, and BAU) significantly differing in their porous structures and surface concentrations of ion-exchange groups and on graphitic thermal carbon black (GTCB). The effective specific surface area of FAS, SKD, and BAU determined by dye adsorption is, respectively, 60, 50, and 40% of the BET nitrogen adsorption surface area. The MB uptake on ACs and GTCB increases with rising pH, while the AO uptake decreases. Addition of an electrolyte (0.3 M NaCl) virtually does not effect the adsorption of dyes on ACs and GTCB. It is suggested that hydrophobic interactions, and not ionic ones, are the major contributors to the adsorption of dyes on ACs.     

Adsorption and selectivity of carbon dioxide with methane and nitrogen in slit-shaped carbonaceous micropores: Simulation and experiment

We have used the grand canonical Monte Carlo method to study the adsorption and selectivity of mixtures of carbon dioxide with methane and nitrogen at high (i.e., ambient) temperatures in model slit pores with graphitic surfaces. Experimental data, including new high pressure measurements for carbon dioxide and methane on a non-porous graphitic standard, were used to test the potential models. The mixture simulations predict that carbon dioxide is preferentially adsorbed in both systems. The results are discussed in terms of competing energetic and entropic effects and the underlying molecular mechanisms.     

Adsorption of SO2 and chlorobenzene on activated carbon

Activated carbon is very effective for simultaneous removal of multiple pollutants. The adsorption of SO₂ and chlorobenzene modeling of VOCs on activated carbon was investigated in a fixed-bed reactor by four kinds of activated carbon. The results show that the SO₂ adsorption is affected by the BET surface and basic functional groups as C=O and π–π* groups of the carbon, while the chlorobenzene adsorption is strongly affected by the carbon pore structure, with the micropore volume deciding the adsorption amount and larger pores increasing the adsorption rate. The chlorobenzene adsorption is little affected by the chemical properties of activated carbon as the O/C ratio detected by XPS. The effect of SO₂ on the chlorobenzene adsorption was investigated, with the results showing the SO₂ seriously restricts the individual chlorobenzene adsorption and this effect becomes smaller in the presence of O₂. The adsorption products were analyzed by TPD-MS and the initial decomposition temperatures are 380 K for chlorobenzene and 500 K for SO₂, showing that SO₂ is much more stable adsorbed than chlorobenzene. The changes of the carbon functional groups that the CO₂ desorption peak emerges at 700 K and decreases at 1000 K with the chlorobenzene adsorption, were observed by TPD-MS, indicating that the lactone and quinone groups on the carbon are likely to combine with the chlorobenzene and form weakly chemisorbed chlorobenzene.     

超临界甲烷在活性炭上的吸附平衡分析

为分析由吸附平衡时的热力参数确定吸附量、吸附模型和等量吸附热精度的影响因素,选择在温度268.15~338.15 K和压力0~13.5 MPa测试的甲烷在Ajax活性炭上的吸附平衡数据,通过引入甲烷分子可进入活性炭吸附空间内的容积和可以不考虑甲烷在孔内吸附的临界孔宽的概念,依据甲烷在吸附平衡前后的总量守恒,确定甲烷在吸附池内的总量、绝对吸附量和过剩吸附量三者之间的关系式。结果表明,在引入吸附质分子可进入吸附空间内的容积和临界孔宽后,经由活性炭的孔径分布(PSD),可以准确计算甲烷在活性炭上的过剩吸附量;应用实验数据非线性回归Toth方程参数后,可由Gibbs关于吸附的定义确定甲烷在活性炭上的绝对吸附量。比较结果时发现,由于未考虑本体相中甲烷分子对吸附甲烷分子的影响,采用过剩吸附量的等量吸附线标绘确定的等量吸附热数值偏高,工程应用时应由绝对吸附量来确定等量吸附热。     

Bacterial attachment to iron-impregnated granular activated carbon

Bacterial attachment to iron-impregnated granular activated carbon (Fe-GAC) was investigated in this study using Enterococcus faecalis ATCC 10100 and charcoal-based GAC. Two sets of column experiments were performed under different ionic strengths and pH conditions. Breakthrough curves of bacteria were obtained by monitoring effluent. Mass recoveries and attachment rate coefficients were quantified from these curves. In addition, characteristics of Fe-GAC were analyzed using field emission scanning electron microscopy (FESEM) and X-ray spectrometry (EDS). Results show that Fe-GAC was characterized by mosaic-like deposition layers of iron oxides with about 2 μm in thickness. Color mapping with FESEM visualized the spatial distribution of carbon (yellow-green) and iron (red) on Fe-GAC. EDS indicates that iron was distinctly found from Fe-GAC at three peak positions. Results also reveal that bacterial attachment to Fe-GAC was affected by ionic strength and pH.Bacterial mass recoveries decreased from 62.9 to 41.7% with increasing ionic strength from 1 to 50 mM. This indicates that bacterial attachment to the surfaces of Fe-GAC was enhanced with increasing ionic strength. With increasing pH from 6.46 to 9.19, mass recoveries increased from 50.5 to 84.2%, indicating that bacterial attachment to Fe-GAC was reduced with increasing pH. This study demonstrates that iron oxides offer favorable attachment sites for bacteria on the surfaces of Fe-GAC and further improves the knowledge of bacterial removal in Fe-GAC.     

Interaction of monochlorinated phenols with granular activated carbon

The validity of an empirical model to estimate the adsorption affinity of a solute from its acidity constant (pKa) was confirmed through study of the adsorption of monochlorinated phenols on granular activated carbon.Neglecting possible adsorbate fragmentation, simplified desorption kinetic data were obtained for the massive thermal release of the investigated solutes. The resulting non-isothermal kinetic parameters confirm that thermal cleaning of the adsorbent surface is a phase-boundary controlled process involving the interruption of physical interactions according to the calculated activation energy values.

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Zusammenfassung Die Gültigkeit eines empirischen Modells zur Abschätzung der Adsorptionsaffinität eines gelösten Stoffes auf Grund der Aciditätskonstante (pKa) wurde durch Untersuchung der Adsorption von monochlorierten Phenolen an granulierter Aktivkohle bestätigt. Unter Vernachlässigung einer möglichen Adsorbatfragmentierung wurden vereinfachte kinetische Daten für die thermische Desorption der untersuchten gelösten Stoffe erhalten. Die erhaltenen, nichtisothermen kinetischen Parameter zeigen, daß die thermische Säuberung der Adsorbentoberfläche ein phasengrenzflächenkontrollierter Prozeß ist, bei dem physikalische Wechselwirkungen entsprechend den berechneten Werten der Aktivierungsenergie aufgehoben werden.

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Adsorption of methyl mercaptan on surface modified activated carbon

The influence of surface modification of activated carbon on the adsorption of methyl mercaptan in N(2) was investigated. The modification of the activated carbon was carried out by treatment with HNO(3)/H(2)SO(4) solutions, heat-treatment in Ar, and adsorption of cetylamine. Acid-treatment increased the adsorption of methyl mercaptan compared with the original activated carbon, and the adsorbed amounts increased with ratio of H(2)SO(4) in HNO(3)/H(2)SO(4) solutions. This result suggests that hydrogen bonding between acidic groups formed by acid-treatment and thiol groups of methyl mercaptan plays a role in adsorption of methyl mercaptan on activated carbon.     

Adsorption properties of iodine-doped activated carbon fiber

Iodine-doped activated carbon fibers (ACFs) were prepared by the iodine immersion method on pitch-based ACF. Then iodine-doped ACFs were heated in argon at 523 K for 4 h and at 673 K for 2 h. The iodine structure of the resultant iodine-doped ACFs was examined using X-ray photoelectron spectroscopy. The micropore structures were determined by N(2) adsorption at 77 K. The surface area and micropore volume of iodine-doped ACFs are less than those of pristine ACFs. However, the pore width does not change with the iodine doping. The effects of iodine doping on adsorption properties of ACFs for H(2)O and NO at 303 K were examined. The iodine doping affected remarkably the adsorptivities of ACFs for H(2)O and NO. In particular, iodine-doped ACFs treated at 673 K show enhanced adsorptivities for H(2)O and NO. This result suggests that iodine molecules doped on the micropores should be charged by heat treatment at 673 K.     

甲烷在层状石墨烯和活性炭上的吸附平衡

以吸附式天然气（ANG）吸附剂的工程应用为目的,以0-10 MPa、283.15-303.15 K甲烷在层状石墨烯（GS（3D）,比表面积2062 m²/g）和活性炭SAC-01（比表面积1507 m²/g）上的吸附平衡数据作分析。首先,在77.15 K下由氮气吸附表征样品的孔径大小及分布（PSD）和比表面积。其次,选择极低压力下的吸附平衡数据标定亨利定律常数,确定甲烷在两吸附剂上的极限吸附热,并由维里方程和10-4-3势能函数计算甲烷与两吸附剂壁面之间的相互作用势。最后,依据测试的甲烷在吸附剂上的高压吸附平衡数据,比较了Langmuir系列方程的关联数据后的拟合精度,并由绝对吸附量计算了甲烷的等量吸附热。结果表明,甲烷在GS（3D）和活性炭SAC-01上的平均极限吸附热为23.07、20.67 kJ/mol;283.15 K下甲烷分子与GS（3D）和活性炭SAC-01之间的交互作用势ε_sf/k为67.19、64.23 K,与洛伦混合法则的计算值64.60 K相近;Toth方程关联甲烷在活性炭SAC-01和GS（3D）上吸附平衡数据的拟合累计相对误差为0.25%和2.29%;甲烷在活性炭SAC-01和GS（3D）上的等量吸附热平均值为16.8和18.3 kJ/mol。相对于活性炭SAC-01,比表面积和微孔容积均较高的GS（3D）对甲烷的吸附更具有优势。     

Adsorption of anthracene using activated carbon and Posidonia oceanica

The aim of this work was to examine the static capacity of adsorption of anthracene by Posidonia oceanica and activated carbon. The effect of experimental parameters pH and contact time on the anthracene adsorption onto cited materials was investigated in detail. The results showed that the anthracene removal on both P. oceanica and activated carbon was unaffected in the pH range of 2–12. The equilibrium data fit well to the Langmuir model with a maximum adsorption capacity of 8.35 mg/g and 0.14 mg/g, respectively with activated carbon and P. oceanica.     

Adsorption of selected herbicides from aqueous solutions on activated carbon

The adsorption of MCPA and 2,4-D on the activated carbon Filtrasorb 300 was studied. The adsorption isotherms of herbicides from aqueous solutions were measured over a wide range of solute concentrations and at different temperatures. The experimental equilibrium data were analyzed by the Langmuir–Freundlich isotherm taking into account the energetic heterogeneity of adsorption system. The effect of temperature and herbicide properties on its uptake was discussed. The thermal analysis was applied in order to find the differences in herbicide interactions with carbon surface. The kinetic dependences were measured and the relations between solute properties and adsorption rate were discussed.     

Adsorption of carbon disulfide on activated carbon modified by Cu and cobalt sulfonated phthalocyanine

A series of adsorbents were studied for removal efficiency of carbon disulfide (CS₂) under micro-oxygen conditions. It was found that activated carbon modified by Cu and cobalt sulfonated phthalocyanine (CoSPc) denoted as ACCu–CoSPc showed significantly enhanced adsorption ability. Reaction temperature was found to be a key factor for adsorption, and 20 °C seems to be optimal for CS₂ removal. Samples were analyzed by N₂-BET, XRD, XPS, SEM–EDS and CO₂-TPD. The characterization results demonstrated that large quantities of SO₄ ^2? anions were formed and adsorbed in the reaction process. SO₂, CS₂ and COS were detected in the effluent gas generated from the temperature programmed desorption of ACCu–CoSPc–CS₂. Therefore, it can be concluded that ACCu–CoSPc most likely acted as a catalyst in the adsorption/oxidation process on the surface of the impregnated sample. The generated sulfide and sulfur oxide can cover the active sites of adsorbents, resulting in pronounced reduction of adsorbent activity. Finally, the exhausted ACCu–CoSPc can be regenerated by thermal desorption.     

Adsorption mechanism of arsenate by zirconyl-functionalized activated carbon

Arsenate [As(V)] and arsenite [As(III)] sorption at the solid-water interface of activated carbon impregnated with zirconyl nitrate (Zr-AC) was investigated using X-ray absorption spectroscopy (XAS) and surface complexation modeling. The XAS data at the Zr K-edge suggest that the structure of the zirconyl nitrate coating is built from chains of edge-sharing ZrO8 trigonal dodecahedra bound to each other through two double hydroxyl bridges. The 8-fold coordination of each Zr atom is completed by four O atoms, which share a bit less than the two theoretically possible bidentate nitrate groups. On impregnation, two of the O atoms may lose their nitrate group and be transformed to hydroxyl groups ready for binding to carboxylic or phenolic ligands at the AC surface. As K-edge XANES results showed the presence of only As(V) on adsorption regardless of the initial As oxidation state. Oxidation to As(V) is probably mediated by available carbon species on the AC surface as found by batch titration. Zr K-edge EXAFS data indicate that arsenate tetrahedra form monodentate mononuclear surface complexes with free hydroxyl groups of zirconyl dodecahedra, whereby each bidentate nitrate group is exchanged by up to two arsenate groups. The inner-sphere arsenate binding to the Zr-AC surface sites constrained with the spectroscopic results was used in the formulation of a surface complexation model to successfully describe the adsorption behavior of arsenate in the pH range between 4 and 12. The results suggest therefore that Zr-AC is an effective adsorbent for arsenic removal due to its high surface area and the presence of high affinity surface hydroxyl groups.     

Adsorption of eicosane and 1,2-hexanediol from supercritical carbon dioxide on activated carbon and chromosorb

Supercritical adsorption isotherms were measured for eicosane and 1,2-hexanediol on activated carbon and chromosorb 101 at 324.2 K and 11.45 MPa. Adsorption isotherms of both solutes on activated carbon have typical shapes and can be modelled by Langmuir or Freundlich equations. For chromosorb 101 the equilibrium loadings are a linear function of the concentration of the solute in the fluid phase. These results suggest that for chromosorb 101 a partition of the solute between two immiscible phases rather than adsorption occurs.