A quantitive microscale dynamic column breakthrough apparatus for measurement of unary and binary adsorption equilibrium on milligram quantities of adsorbent

A microscale dynamic column breakthrough (μDCB) apparatus with the ability to measure unary and binary adsorption equilibrium on a milligram-scale quantity of adsorbent is described. The μDCB is a low cost system that can be constructed through minor modifications of a commercial gas chromatograph and uses a thermal conductivity detector. The small scale of the apparatus allows for the rapid collection of dynamic column breakthrough experiments. The mass balances for adsorption and desorption experiments were derived along with a description of the blank. The μDCB apparatus was tested with 238.9 mg of zeolite 13X and 180.2 mg of activated carbon with single-component N2/He and CH4/He adsorption and desorption measurements. The measured equilibrium data agreed well with volumetrically collected data. These measurements are both accurate and precise. Multicomponent adsorption was also studied on zeolite 13X and activated carbon for CH4/N2 and CO2/CH4 mixtures. This data was compared with ideal and adsorbed solution theory, extended dual-site Langmuir calculations and the literature.

Elucidation of Adsorption Mechanisms And Mass Transfer Controlling Resistances During Single And Binary Adsorption of Caffeic And Chlorogenic Acids

In this work, the potential of activated carbon to remove caffeic and chlorogenic acids was investigated. The study focused on evaluating the single and binary adsorption equilibrium, as well as investigating the mass transfer resistances present during the process by applying kinetic and diffusional models for a future scale-up of the process. For both compounds, the single adsorption equilibrium was studied at pH values of 3, 5, and 7. The experimental adsorption isotherms were interpreted using the Langmuir and Freundlich models, obtaining maximum adsorption capacities of 1.33 and 1.62 mmol/g for caffeic and chlorogenic acid, respectively. It was found that the adsorption mechanisms for both compounds was derived from π-π and electrostatic interactions. Also, the binary adsorption equilibrium was performed and the experimental data were interpreted using the extended multicomponent Langmuir model. The results evidenced that the binary adsorption of caffeic acid and chlorogenic acid is antagonistic in nature. The application of the first and second order kinetic models showed that the latter interpreted better the experimental data, obtaining R2 values close to one. Finally, the experimental adsorption rate data were interpreted by a diffusional model, finding the presence of different mass transfer resistances during the adsorption process. For both compounds, intraparticle diffusion mechanisms were meaningful.

Single and Binary Adsorption Systems of Rhodamine B and Methylene Blue onto Alkali-Activated Vietnamese Diatomite

Diatomite was slightly modified with a sodium hydroxide solution. The resulting material was characterized by using energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and nitrogen adsorption-desorption isotherms. The so-treated diatomite has a high specific surface area (77.8 m2/g) and a high concentration of isolated silanol groups on the surface, and therefore, its adsorption capacity increases drastically in both the single and binary adsorption systems for rhodamine B and methylene blue. The binary system is more effective than the single system, with methylene blue being adsorbed more than rhodamine B. The adsorption process is spontaneous and fits well with the Langmuir isothermal model, and it depends on pH significantly.

Energy-Saving and Sustainable Separation of Bioalcohols by Adsorption on Bone Char

The separation of ethanol, propanol, and butanol from aqueous solutions was studied using adsorption on bone char. Adsorption kinetics and thermodynamic parameters of this separation method were studied at different conditions of pH and temperature. Results showed that the maximum adsorption capacities of these bioalcohols were obtained at pH 6 and 20°C. An exothermic separation was identified, which can be mainly associated to hydrophobic interactions between bone char surface and bioalcohols. Binary adsorption studies were also performed using mixtures of these bioalcohols. An antagonistic adsorption was observed for all bioalcohols where the ethanol and propanol separation was significantly affected by butanol. A model based on an artificial neural network was proposed to correlate both single and binary adsorption isotherms of these bioalcohols with bone char. It was concluded that the bone char could be an interesting adsorbent for the sustainable separation and recovery of bioalcohols from fermentation broths, which are actually considered emerging liquid biofuels and relevant industrial chemicals.

Binary Adsorption Studies of Toxic Metal Ions of Lead and Copper from Aqueous Solution by Modified Foeniculum vulgaris Seeds (Fennel Seeds)

Discharge of copper(II) and lead(II) ions into rivers and streams by industries and other human activities has gained serious consideration from regulatory bodies. These toxic metals are harmful to human beings and aquatic life when in high concentrations. Therefore, their removal from wastewater is very important. Hence, this work reports the binary adsorption of toxic metal ions of Cu(II) and Pb(II) from aqueous solution by pristine and modified fennel seeds. Pristine fennel seeds (PFS) were treated with acidic and alkaline solutions to develop modified adsorbents designated ATFS and BTFS, respectively. SEM images revealed that PFS had an amorphous surface with irregular cavities. However, upon acid and base treatment, the surface was more refined. The ATFS had interconnected pores while BTFS had somewhat honeycomb pores. The UV-Vis results confirmed that some of the components were removed from PFS during acid and base pre-treatment. FTIR spectra revealed that the adsorbents had functional groups such as (-OH) and (-C=O), which were involved in the uptake of the metal ions. It was observed that the uptake of Cu(II) and Pb(II) ions onto all adsorbents progressively increased when the initial concentration of the solution was increased. The maximum adsorption capacity was obtained when the initial concentration of the solution was 100 mg/L. The uptake of Cu(II) and Pb(II) on PFS was 3.345 and 11.524 mg/g. While for ATFS 3.78 and 13.07 mg/g and BTFS 8.143 and 14.85 mg/g, respectively. It was observed that the isotherm data fitted Freundlich better for the uptake of both metal ions onto all adsorbents. It was observed that there was a rapid uptake when contact time increased from 5 to 60 min. However, when time increased above 60 min the uptake stabilized and reached equilibrium this was due to the saturation of active sites on the surface for all adsorbents. The kinetics study revealed that PSO fitted the data better than PFO. IPD data revealed that the uptake of metal ions was controlled by the synergistic of ESA and EPA. The ΔHº values for Cu(II) and Pb(II) uptake onto all adsorbents were all negative. This suggested that the reactions were exothermic.