Nonlinear Kinetic and Equilibrium Adsorption Isotherm Study of Cadmium (II) Sorption by Dacryodes edulis Biomass

The kinetics and equilibrium adsorption isotherm of cadmium (II) adsorption onto Dacryodes edulis (native peer seed) biomass was studied using a nonlinear approach, which is unpopular but proven in some literature to be more reliable and easier. In optimizing the process, about 98% removal of the cadmium ion was achieved within five minutes at pH 7 by contacting just 30 mg of the Dacryodes edulis seed biomass with the adsorbate solution of a concentration of 100 mg/L. Non-linear investigation of the kinetics and adsorption isotherms of the process was done using the R console statistical and computing software. The results indicated that the Elovich mechanism and the Freundlich adsorption isotherm most suitably described the kinetics and adsorption isotherm, respectively, of the process as provided by their least values of the sum of squared residuals (SSR). This outcome implied a chemical adsorption (chemisorption) mechanism and a multi-layer coverage by the cadmium ions on heterogeneous active sites of the biomass surface with a Freundlich constant or capacity factor, Kf of 27.83 mg g-1, heterogeneity factor, 1/n of 0.2614 and Elovich constants, α and β of 7.0 mg g−1 s−1 and 1.0 g mg-1, respectively. These findings indicate that Dacryodes edulis seed biomass has a good potential for cadmium (II) adsorption. Keywords: Dacryodes edulis, Elovich kinetic model, Freundlich isotherm, Langmuir isotherm, Nonlinear

Comparative Study on Potentiality of Polypyrrole composite as Adsorbent for the removal of Acidic and Basic dyes from Aqueous solutions

The potentiality of polypyrrole coated sawdust (PPy/SD) derived from the fruit of the gardening plant material of Cordia Sebestena to remove acidic dye and basic dye [Acidic Dye namely Acid Orange 7 (AO7) and Basic dye namely Basic Red 29 (BR29)] from aqueous solutions via adsorption was investigated. Adsorption experiments are carried out using batch system in order to do equilibrium adsorption isotherm, kinetics and thermodynamic studies. It is found that chemical modification of plant waste like sawdust coated with polypyrrole called polypyrrole composite is an efficient adsorbent for the removal of AO7 and BR29 from aqueous solutions. Finally, the performance of PPy/SD was compared with both the dyes. The experimental results indicated that adsorbent is effective and economically viable for the removal of both acidic (AO7) and basic (BR29) dyes and is most suitable for the removal of Acid Orange 7 from aqueous solutions than Basic Red 29.

A Porous Carbon with Excellent Gas Storage Properties from Waste Polystyrene

In this paper, we describe the synthesis and gas adsorption properties of a porous carbonaceous material, obtained from commercial expanded polystyrene. The first step consists of the Friedel-Craft reaction of the dissolved polystyrene chains with a bridging agent to form a highly-crosslinked polymer, with permanent porosity of 0.7 cm3/g; then, this polymer is treated with potassium hydroxide at a high temperature to produce a carbon material with a porous volume larger than 1.4 cm3/g and a distribution of ultramicro-, micro-, and mesopores. After characterization of the porous carbon and determination of the bulk density, the methane uptake was measured using a volumetric apparatus to pressures up to 30 bar. The equilibrium adsorption isotherm obtained is among the highest ever reported for this kind of material. The interest of this product lies both in its excellent performance and in the virtually costless starting material.

Adsorption of Ni(II) Ion onto Calcined Eggshells: A Study of Equilibrium Adsorption Isotherm

Adsorption is one of the most effective and economical method to treat heavy metals in water. In this study, we utilize waste chicken eggshells as biosorbent to adsorb Ni(II). Furthermore we study the effect of eggshell calcination on its adsorption performance. The effect of calcination on the characteristic of eggshell was observed using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope-Energy Dispersive X-ray Spectroscopy (SEM-EDS). It could be observed that CaCO3 in eggshell was converted into CaO, and from SEM images the calcined eggshell became more porous than the uncalcined one. The effect of various parameters such as initial Ni(II) solution pH and initial Ni(II) concentration was investigated using batch adsorption experiments. The data obtained then fitted to Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherms. The best pH for Ni(II) adsorption was found to be 6. From Langmuir and Dubinin-Radushkevich, it was found that calcined eggshells gave 60 times higher maximum adsorption capacity then uncalcined one. This increase was possible due to more porous structure of calcined eggshells. The adsorption process was found to be exothermic and physisorption. This result was confirmed by the decrease of % removal with increase of temperature. Furthermore, Langmuir isotherm was found to be the best model, indicating adsorption of Ni(II) was monolayer adsorption on homogenous surface.

Equilibrium Adsorption Isotherm Mechanism of Water Vapor on Zeolites 3A, 4A, X, and Y

Many researchers have analyzed the equilibrium adsorption isotherm mechanism of water vapor molecules on 4A, 3A, Y and X zeolites for decades. The demand for moisture removal continues to increase along with the increasing stringency of requirements for product quality control and production energy efficiency. Due to the negative charge of the zeolite framework, exchangeable compensation cations such as Na+, Li+, K+, Ba2+, Mg2+, and Ca2+ might be added. These cations are located at different sites within the framework and with different concentrations. Each cation shows a strong affinity to bond with water molecules. Adsorption sites must show a characteristic energy signature corresponding to the adsorbed amount. The values of enthalpies and entropies at each site are different since the bonding strength between the moisture molecules and cations of the site is also different. These exchangeable cations have a very important contribution in determining the zeolites adsorptive properties and selectivity. This investigation of the water vapor adsorption mechanism reveals that size, location, and type of exchangeable compensation cations have a concrete relationship to the adsorption process and zeolite cage capacity.

Kinetics and adsorption isotherm of lactic acid from fermentation broth onto activated charcoal

Activated charcoal was applied for the recovery of lactic acid in undissociated form from fermentation broth. Lactic acid was obtained from the fermentation of Lactobacillus casei TISTR 1340 using acid hydrolyzed Jerusalem artichoke as a carbon source. The equilibrium adsorption isotherm and kinetics for the lactic acid separation were investigated. The experimental data for lactic acid adsorption from fermentation broth were best described by the Freundlich isotherm and the pseudo-second order kinetics with R2 values of 0.99. The initial adsorption rate was 41.32 mg/g?min at the initial lactic acid concentration of 40 g/L.