Kinetic evaluation of phenol/aniline mixtures adsorption from aqueous solutions onto activated carbon and hypercrosslinked polymeric resin (MN200)

Kinetic adsorption of phenol and aniline from aqueous solution onto activated carbon and hypercrosslinked polymeric resin MN200 were evaluated in single and binary system. Larger phenol and aniline uptakes were observed for activated carbon in single as well as binary system, which can be attributed to the better physical properties of activated carbon, for instance larger surface area and micropore area. The kinetic experimental data was properly fitted by the pseudo-first and pseudo-second-order rate equations. A synergetic effect between solutes was observed since phenol and aniline sorption kinetic in binary system was faster than the individual sorption of each solute in single system, as well as a slight increase in the kinetic parameters obtained in binary system. The particle diffusion rate was defined as the rate limiting mechanism in the singles and binary system for phenol and aniline kinetic adsorption on both adsorbents. Two steps were markedly defined by the Weber and Morris intraparticle diffusion analysis for phenol and aniline onto both adsorbents. In binary systems, the intraparticle diffusion was influenced by the physical properties of adsorbents.     

Preparation and characterisation of demineralised tyre derived activated carbon

The effect of demineralisation and activation conditions on the physical and chemical properties of activated carbon adsorbents produced from waste tyre char has been investigated. Experimental data showed that hydrochloric acid treatment prior to the activation is able to remove certain mineral contents such as zinc, calcium, sodium and others from the tyre char. The removal of some of the components which have catalytic effect on the activation increase the yield of the activated carbon and at the same time lower the ash content of the tyre activated carbon. The tyre demineralised activated carbons are generally mesoporous with a surface area up to 960 m²/g and therefore are comparable to commercial products. The adsorption of phenol onto the tyre activated carbon was also tested and the Redlich–Peterson equilibrium isotherm model gave the best-fit to experimental data for the phenol using the non-linear error functions.     

海藻酸镧颗粒除氟研究：吸附剂物性和吸附机理

Lanthanum alginate bead is a new, highly active adsorbent. In the present study, we investigated its ad- sorption performance and its adsorption mechanism. The adsorption isotherm for fluoride onto lanthanum alginate b ead fits the Langmuir model well, and the maximum adsorption capacity is 197.2 mg·g-1. X-ray diffraction shows the amorphous nature of lanthanum alginate bead, which allows for better accessibility to fluoride and thus better activity. Infrared spectra of lanthanum alginate bead before and after adsorption confirm its stable skeletal structure. Scanning electron microscopy shows that the dense surface structure of the adsorbent appear cracks after adsorption. T he adsorption mechanism of lanthanum alginate bead is considered as an ion exchange between F- and Cl- or OH-, as verified from the adsorbent and the solution by pH effect, energy dispersive X-ray, and ion chromatography.     

Adsorption of lead and copper on bentonite and grapeseed activated carbon in single- and binary-ion systems

In this study, bentonite originating from Turkey (Eski?ehir province) and activated carbon obtained from grapeseed were used as adsorbents for the removal of lead (Pb²⁺) and copper (Cu²⁺) ions from aqueous solutions. Experiments were performed in single- and binary-ion systems at constant temperature of 298 K and pH value of 5. In order to describe the adsorption mechanism Langmuir, Freundlich and Temkin isotherms were used. The total adsorption capacity values of adsorbents were compared. It was observed that the total adsorption capacity values were changed depending on the type of adsorbent used, type of metal ion and interaction between metal ions.     

Binary component sorption of Cu(II) and Pb(II) with activated carbon from Eucalyptus camaldulensis Dehn bark

The objective of this work is to illustrate the potential in the use of activated carbon in the binary component sorption of copper and lead ions. Eucalyptus bark was used as a precursor for the activated carbon which was prepared through the phosphoric acid activation process. This activated carbon was then used for the sorption of copper and lead ions. The quantity of the metal ions in the solution was measured with the Flame & Graphite Furnace Atomic Adsorption Spectrophotometer. The results indicated that the optimal pH for sorption was 5. The maximum sorption capacities for Cu(II) and Pb(II) were 0.45 and 0.53 mmol g⁻¹. Carboxylic, amine and amide groups were found to involve in the sorptions of Cu(II) and Pb(II). A major mechanism for the uptake of both heavy metals was proven not to be ion exchange but adsorption. In binary component sorptions, activated carbon still could sorb Pb(II) in a greater amount than Cu(II). However, the presence of the secondary metal ions suppressed the sorption of the primary metal ions. There seemed to have a linear inverse dependency between the sorption capacity and the concentration of the secondary metal ion.     

Simultaneous adsorption of phenol and Cu2+ from aqueous solution by activated carbon/chitosan composite

A multifunction adsorbent was synthesized by incorporating AC into CTS, and the ratio of AC to CTS was 1/1. The resultant was called activated carbon (AC)/chitosan (CTS) composite. The simultaneous adsorption of phenol and Cu²⁺ from aqueous solution onto AC/CTS composite was investigated by a batch procedure. The adsorption processes for both Cu²⁺ and phenol obeyed the pseudo second-order kinetic model. Phenol was prone to be adsorbed more quickly as compared with Cu²⁺ when they coexisted in solution. The adsorption behavior of both phenol and Cu²⁺ followed the Langmuir isotherm. The maximum adsorption capacities of phenol and Cu²⁺ were 34.19 mg/g and 74.35 mg/g at 293 K, respectively. No obvious competitive adsorption existed between phenol and Cu²⁺.     

Removal of Hg2+ from aqueous solution using a novel composite carbon adsorbent

A novel composite carbon adsorbent (GCA) has been prepared by immobilizing activated carbon and genipin‐crosslinked chitosan into calcium alginate gel beads via entrapment and applied to the removal of mercury (Hg²⁺) ions from aqueous solution (e.g., drinking water). Two bead sizes and two mixing ratios of components were obtained and characterized. Batch experiments were performed to study the uptake equilibrium and kinetics of Hg²⁺ ions by the GCA. The Hg²⁺ adsorption capacity of GCA was found to be dependent of pH and independent of size of the adsorbent. The Hg²⁺ adsorption rate of GCA increases with decreasing its bead size. However, both adsorption capacity and rate of GCA for Hg²⁺ increase with increasing its chitosan content. Otherwise, it was shown that the GCA has higher Hg²⁺ adsorption capacity and rate than activated carbon, which might be caused by the incorporation of chitosan into the GCA. The maximum Hg²⁺ adsorption capacity of GCA was found to be 576 mg/g, which is over seven times higher than that of activated carbon. Our results reveal the uniform distribution of activated carbon and chitosan within the alginate gel bead and that Hg²⁺ ions can diffuse inside the bead. It also demonstrated the feasibility of using this GCA for Hg²⁺ removal at low pH values. The Hg²⁺ absorbed beads of the GCA can be effectively regenerated and reused using H₂SO₄. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Hexavalent chromium adsorption on superparamagnetic multi-wall carbon nanotubes and activated carbon composites

Hexavalent chromium (Cr(VI)) adsorption from aqueous solutions on magnetically modified multi-wall carbon nanotubes (M-MWCNT) and activated carbon (M-AC) was investigated. M-MWCNT and M-AC were prepared by co-precipitation method with Fe²⁺:Fe³⁺ salts as precursors. The magnetic adsorbents were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscope (SEM). The effects of amount of adsorbents, contact time, initial pH, temperature and the initial concentration of Cr(VI) solution were determined. The adsorption equilibrium, kinetics, thermodynamics and desorption of Cr(VI) were investigated. Equilibrium data fitted well with the Langmuir isotherm for both of the adsorbents. The theoretical adsorption capacities are 14.28 mg/g of M-MWCNT and 2.84 mg/g of M-AC. Cr(VI) adsorption kinetics was modeled with pseudo-second order model, intra-particle diffusion model and Bangham model. Thermodynamic parameters were calculated and ΔG°, ΔH° and ΔS° indicate that the adsorption of Cr(VI) onto M-MWCNT and M-AC was exothermic and spontaneous in nature. Results revealed that M-MWCNT is an easily separated effective adsorbent for Cr(VI) adsorption from aqueous solution.     

Removal of copper (II) and phenol from aqueous solution using porous carbons derived from hydrothermal chars

The feasibility of hydrothermal char (HTC), a byproduct from biomass hydrothermal liquefaction for bio-oil production, as raw material for preparation of porous carbons was investigated in the present study. The resultant HTC-derived porous carbons were characterized and utilized as adsorbents for copper (II) and phenol removal from aqueous solution. Compared with porous carbons using pyrolytic char as precursor, the HTC-derived porous carbons exhibited unique textural features, e.g., narrow pore size distribution, high surface area and large pore size. In addition, FT-IR analysis confirmed that substantial amount of ketene groups existed on the surface of the HTC-derived porous carbons. As the adsorbents, the copper (II) adsorption onto HTC-derived carbons was strongly affected by the pH value of the solution in comparison with phenol adsorption. The carbons derived from pinewood and rice husk HTC exhibited high adsorption capacity of 83.88 and 39.30 mg/g for phenol and 25.18 and 22.62 mg/g for copper (II), respectively. The adsorption data for copper (II) and phenol onto the carbon adsorbents could be well described by Langmuir and Freundlich models. In comparison with pinewood sawdust HTC-derived carbon, the adsorption onto rice husk HTC-derived carbon preferentially followed Freundlich model due to the presence of silica on the surface.     

Palladium,silver, and zinc oxide nanoparticles loaded on activated carbon as adsorbent for removal of bromophenol red from aqueous solution

The adsorption of bromophenol red (BPR) onto three adsorbents including palladium, silver and zinc oxide nanoparticles loaded on activated carbon (Pd-NP-AC, Ag-NP-AC and ZnO-NP-AC) in a batch system has been studied and the influence of various parameters has been optimized. The influence of time on removal of BPR on all adsorbent was investigated and experimental data were analyzed by four kinetic models including pseudo first and second-order, Elovich and the intraparticle diffusion equations. Following fitting the experimental data to these models, the respective parameters of each model such as rate constants, equilibrium adsorption capacities and correlation coefficients for each model were investigated and based on well known criterion their applicability was judged. It was seen that the adsorption of BPR onto all adsorbents sufficiently described by the pseudo second-order equation in addition to interparticle diffusion model. The adsorption of BPR on all adsorbent was investigated at various concentration of dye and the experimental equilibrium data were analyzed and fitted to the Langmuir, Freundlich, Tempkin, Dubinin, and Radushkevich equations. A single stage in batch process was efficient and suitable for all adsorbents using the Langmuir isotherm with maximum adsorption of 143 mg g^?1 for Pd-NP-AC, 250 mg g^?1 for Ag-NP-AC and 200 mg g^?1 for ZnO-NR-AC. Thermodynamic parameters such as ΔG°, ΔH°, and ΔS° for Pd-NP-AC adsorbent were calculated.     

Competitive adsorption of Pb, Cu and Cd ions from aqueous solutions by multiwalled carbon nanotubes

The individual and competitive adsorption capacities of Pb²⁺, Cu²⁺ and Cd²⁺ by nitric acid treated multiwalled carbon nanotubes (CNTs) were studied. The maximum sorption capacities calculated by applying the Langmuir equation to single ion adsorption isotherms were 97.08 mg/g for Pb²⁺, 24.49 mg/g for Cu²⁺ and 10.86 mg/g for Cd²⁺ at an equilibrium concentration of 10 mg/l. The competitive adsorption studies showed that the affinity order of three metal ions adsorbed by CNTs is Pb²⁺>Cu²⁺>Cd²⁺. The Langmuir adsorption model can represent experimental data of Pb²⁺ and Cu²⁺ well, but does not provide a good fit for Cd²⁺ adsorption data. The effects of solution pH, ionic strength and CNT dosage on the competitive adsorption of Pb²⁺, Cu²⁺ and Cd²⁺ ions were investigated. The comparison of CNTs with other adsorbents suggests that CNTs have great potential applications in environmental protection regardless of their higher cost at present.     

Adsorption of natural gas and biogas components on activated carbon

Experimental results are presented for the adsorption equilibria of methane, ethane, propane, butane, carbon dioxide, and nitrogen, as well as natural gas odorants tert-butyl mercaptan and tetrahydrothiophene, on an activated carbon with the desirable characteristics for use in a guard bed for adsorbed natural gas storage, but that can also be applied for separation of biogas components, such as carbon dioxide and nitrogen. The adsorption experiments were performed using both open- and closed-loop gravimetry over the pressure and temperature ranges of 0–9 MPa and 273–325 K, respectively. The two odorants were analyzed at the very low concentrations usually found in natural gas (0–25 mg/(N m³)). The experimental data were successfully correlated by the adsorption potential theory and collapsed into a single temperature-independent characteristic curve. This analysis allows for extrapolation of the adsorption data to higher alkanes, for which no experimental data are available, in order to span the global composition of a typical natural gas stream. The adsorption equilibrium data for methane, carbon dioxide and nitrogen were fitted to the Toth and Sips isotherm models and their isosteric heats of adsorption were determined. The preferential adsorption capacity for carbon dioxide indicates that the carbon can be used for methane purification from natural gas, carbon dioxide sequestration from flue gas, or biogas purification.     

Removal of metal ions from aqueous solution by adsorption onto activated carbon cloths: adsorption competition with organic matter

Activated carbon cloths are recent adsorbents whose adsorption properties are well known for monocomponent solutions of organics or metal ions. However, to treat wastewaters with these materials, their performance has to be determined in multicomponent solution. This work studies adsorption competition between metal ions (Cu²⁺, Pb²⁺) and organic matter (benzoic acid). The first part investigates adsorption equilibrium of monocomponent metal ions solutions and shows the dependence of adsorption capacities on adsorbent porosity and metal ions chemical properties (molecular weight, ionic radius and electronegativity). The influence of pH is also demonstrated. The second part focuses on adsorption competition: (1) between both metal ions (a decrease of adsorption capacities is observed, whose value is related to adsorption kinetics of metal ions); (2) between metal ions and organic matter, in solution or adsorbed onto the activated carbon cloth (a strong influence of pH is shown: when benzoic acid is under benzoate form, in both cases adsorption is increased due to the formation of ligands between adsorbed benzoate ions and metals).     

Adsorption of copper and lead species at electrochemically activated glassy carbon electrodes

The adsorption behaviors of Cu²⁺ and Pb²⁺ species at electrochemically activated glassy carbon obtained by different activation methods have been studied. Micropore structures were developed by cyclic polarization while small void space located at the bottom of the large void space was resulted from potentiostatic activation. The adsorption of the adsorbents would depend on the relative sizes of both the adsorbents and the void space created by electrochemical pretreatment. Different quinone derivatives would adsorb to different adsorption sites at the activated electrode, and consequently, affected the uptake of metal ions at the activated electrode incorporated with different quinone derivatives. Electrostatic and hydrophobic interactions between the adsorbents and the graphite oxide film might be involved.     

Boron removal from water and its recovery using iron (Fe) oxide/hydroxide-based nanoparticles (NanoFe) and NanoFe-impregnated granular activated carbon as adsorbent

This study presents information obtained by the synthesis of Fe(3) oxide/hydroxide nanoparticles sol (NanoFe) and NanoFe-impregnated granular activated carbon as adsorbents for boron removal from solutions. The research describes an adsorption method for cleaning a solution containing boron contaminants followed by recovery of the adsorbent and the adsorbed material for safe removal or further reuse. The technology provides an efficient method of boron removal from water. A marked effect of NanoFe and NanoFe-impregnated GAC adsorbents concentration and pH level on boron removal efficiency was demonstrated. At least 95–98% boron recovery efficiency is possible using NanoFe sol and Fe-impregnated GAC that in fact also recover the adsorbent for reuse. Boron adsorption onto the NanoFe-impregnated GAC adsorbent may be described by pseudo-second-order reaction kinetics and the Langmuir isotherm model. The boron adsorption capacity on iron (3) oxide nanoparticles and Fe-impregnated GAC at an equilibrium concentration of 0.3 mg/dm³ as B in the solution is much higher than these values for similar adsorbents reported in the literature.     

Comparison of textile dyeing effluent adsorption on commercial activated carbon and activated carbon prepared from olive stone by ZnCl2 activation

Adsorption of Remazol Red B on activated carbon prepared from olive stone and commercial activated carbon from aqueous solutions was compared. Different activating agent (ZnCl₂) amounts and adsorbent particle size were studied to optimize adsorbent surface area. The adsorptive property of commercial activated carbon and activated carbon prepared from olive stone were investigated in terms of adsorbent dose, temperature, equilibrium time and pH. Then the obtained results were compared for all parameters, According to the results, the equilibrium time, optimum pH, adsorbent dosage were found 60 min, pH < 3–4 and 1.0 g/50 ml respectively. Lower adsorption capacity for RRB on activated carbon prepared from olive stone was found. The kinetic data for both adsorbents supports pseudo-second order model (r² > 0.99) and intra-particle model (r² > 0.95) but the first order kinetic model did not adequately fit to the experimental values (r² < 0.76). The equilibrium adsorption data were interpreted using Langmuir and Freundlich models. The adsorption of Remazol Red B was better represented by the Langmuir equation. In addition, the thermodynamic parameters, standard free energy (ΔG°), standard enthalpy (ΔH°), standard entropy (ΔS°) of the adsorption process were calculated for both adsorbents. To reveal the adsorptive characteristics of the produced active carbon, surface area measurements were carried out and structural analysis was performed using SEM-EDS.     

Removal of Cu2+ and Pb2+ ions from aqueous solutions by starch-graft-acrylic acid/montmorillonite superabsorbent nanocomposite hydrogels

In this study, the removal of copper(II) and lead(II) ions from aqueous solutions by Starch-graft-acrylic acid/montmorillonite (S-g-AA/MMT) nanocomposite hydrogels was investigated. For this purpose, various factors affecting the removal of heavy metal ions, such as treatment time with the solution, initial pH of the solution, initial metal ion concentration, and MMT content were investigated. The metal ion removal capacities of copolymers increased with increasing pH, and pH 4 was found to be the optimal pH value for maximum metal removal capacity. Adsorption data of the nanocomposite hydrogels were modeled by the pseudo-second-order kinetic equation in order to investigate heavy metal ions adsorption mechanism. The observed affinity order in competitive removal of heavy metals was found Cu²⁺ > Pb²⁺. The Freundlich equations were used to fit the equilibrium isotherms. The Freundlich adsorption law was applicable to be adsorption of metal ions onto nanocomposite hydrogel.     

Powdered activated carbon and carbon paste electrodes: comparison of electrochemical behaviour

Commercial activated carbon (Norit R3ex), de-mineralised with conc. HF and HCl, was oxidised (conc. HNO₃) and heat-treated at various temperatures (180, 300 and 420 °C). The physicochemical properties of the samples obtained were characterised by selective neutralisation and pH-metric titration of surface functional groups (acid–base properties), thermogravimetry (thermal stability—TG), FTIR spectroscopy (chemical structure) and low-temperature nitrogen adsorption (BET surface area). Thermal treatment of the carbon materials caused the surface functional groups to decompose; in consequence, the chemical properties of the carbon surfaces changed. Cyclic voltammetric studies were carried out on all samples using a powdered activated carbon electrode (PACE) and a carbon paste electrode (CPE), as were electrochemical measurements in aqueous electrolyte solutions (0.1 M HNO₃ or NaNO₃) in the presence of Cu²⁺ ions acting as a depolariser. The shapes of the cyclic voltammograms varied according to the form of the electrodes (powder or paste) and to the changes in the surface chemical structure of the carbons. The electrochemical behaviour of the carbons depended on the presence of oxygen-containing surface functional groups. The peak potentials and their charge for the redox reactions of copper ions depended on their interaction with the carbon surface.     

Adsorption of 1,2-Dichlorobenzene from the Aqueous Phase onto Activated Carbons and Modified Carbon Nanotubes

This study aimed to describe the adsorption process of ortho-dichlorobenzene (o-DCB) onto activated carbons (ACs) and modified carbon nanotubes (CNTs) from the aqueous phase. The starting material NC_7000 carbon nanotubes were modified by chlorination (NC_C) and then by the introduction of hydroxyl groups (NC_C_B). The concentration of o-DCB in solutions was performed by UV-VIS spectrophotometry. After adsorption, the activated carbons were regenerated by extraction with organic solvents such as acetone, methanol, ethanol, and 1-propanol; the carbon nanotubes were regenerated by methanol. The degree of adsorbate recovery was determined by gas chromatography (GC) with flame ionization detection, using ethylbenzene as an internal standard. The equilibrium isotherm data of adsorption were satisfactorily fitted by the Langmuir equations. The results indicate that carbon adsorbents are effective porous materials for removing o-DCB from the aqueous phase. Additionally, activated carbons are more regenerative adsorbents than carbon nanotubes. The recoveries of o-DCB from ACs were in the range of 76–85%, whereas the recoveries from CNTs were in the range of 23–46%. Modifications of CNTs affect the improvement of their adsorption properties towards o-DCB compared to unmodified CNTs. However, the introduction of new functional groups on carbon nanotube surfaces makes the regeneration process less effective.     

Adsorption of phenol by oil–palm-shell activated carbons in a fixed bed

Steam-activated carbons from oil–palm shells were prepared and used in the adsorption of phenol. The activated carbon had a well-developed non-micropore structure which accounted for 55% of the total pore volume. The largest Brunauer–Emmett–Teller (BET) surface area of the activated carbon was 1183 m²/g with a total pore volume of 0.69 cm³/g using N₂ adsorption at 77 K. Experimental tests on the adsorption of phenol by the activated carbons were carried out in a fixed bed. The aqueous phase adsorption isotherms could be described by the Langmuir equation. The effects of the operation conditions of the fixed bed on the breakthrough curve were investigated. A linear driving force model based on particle phase concentration difference (LDFQ model) was used to simulate the fixed bed adsorption system. The model simulations agreed with the experimental data reasonably well.