Removal of Cresols From Water By Packed Beds of Cyclodextrin-Based Hydrogels

A cyclodextrin-based polymer was prepared by crosslinking β-cyclodextrin with epichlorohydrin to be assessed as a sorbent material for cresols in packed-bed columns. Both Langmuir and Freundlich isotherms were appropriate to describe the sorption equilibrium in the conditions tested, and the thermodynamic parameters obtained for this process confirmed its exothermic nature with similar enthalpies (between −6.8 and −8.3 kJ/mol) for the three isomers. The removal of cresols from water was carried out in nine cycles of sorption-desorption in fixed-column experiments with the cyclodextrin hydrogel, achieving sorption capacities of 6.2, 11.6, and 15.1 mg/g for o-, m-, p-cresol, respectively. The experimental data for the breakthrough and the elution curves have been successfully modeled by two effective two-parameter equations, a dose-response model for the sorption step and a pulse-peak model for the regeneration step. The cyclodextrin polymer matrix has been proven to be an effective a good sorbent material for removing cresols from water, exhibiting remarkable reusability performance and structural stability throughout the successive elution steps carried out with methanol.

Adsorption kinetic characteristics of molybdenum in yellow-brown soil in response to pH and phosphate

Molybdenum (Mo) adsorption by acidic yellow-brown soil was investigated as a function of a pH (1–13) and the equilibrium of P solution (0, 3.1, and 31 mg L−1) concentration. Mo adsorption by acidic yellow-brown soil increased within the pH range from 1 to 4. Above pH 4, Mo adsorption decreases with an increase in pH. The maximum adsorption was found between pH 2 and 4. Competitive adsorption experiments showed that the equilibrium sorption data fitted into Langmuir and Freundlich isotherms. The sorption data of Mo on the acidic yellow-brown soil fitted well with the Langmuir isotherm model due to the higher R2 value. A reduction in Mo adsorption by the acidic yellow-brown soil was noticed at higher addition levels of P (3.1 and 31 mg L−1). Therefore, P increasing the bioavailability of Mo and enhancing Mo uptake by plants might be related to the inhibition of Mo absorption by the acidic yellow-brown soil.

Clarification of Reprocessed Syrup and Use in the Formulation of Lollipop-Type Hard Candies

The objective was to evaluate the removal of dye using activated carbon, and apply the best condition in the removal of candy reprocessing syrup pigment, as well as to evaluate its influence in the visual aspect of a lollipop. Adsorption capacity tests were performed with the dye diluted with and without sucrose, and from the data, the linearization of the Langmuir and Freundlich isotherms were calculated. The lollipop was prepared with syrup treated with activated carbon and visually evaluated using a panel of untrained tasters. The Freundlich isotherm adjusted more appropriately to the experimental data of the adsorption of the dye diluted in distilled water, while for the dye diluted in sucrose solution, the most suitable model was Langmuir's. The experimental design condition showed the highest adsorptive capacity (26.91 mg.g-1) for the dye diluted in the aqueous solution was at a temperature of 60 ºC and pH 5.5, while for the sucrose-diluted dye solution, was 103.09 mg.g-1, under the same conditions. The visual evaluation of the lollipop indicated the possibility of adding up to 15% of reprocessing syrup. Thus, the use of activated carbon is an alternative to remove the coloring from candy syrup and enable its reuse within the industry.

A Study on Removal of Heavy Metal Chromium from Aqueous Chromium Solution Using Ipomoea carnea Root as Biosorbent

Pollution is the main problem due to heavy metal discharges from industries . In this study Ipomoea carnea (Family:Convolvulaceae) is selected to remove the heavy metal chromium from aqueous chromium solution using biosorbent . The present work focuses to evaluate the effectiveness of low cost absorbent Ipomoea carnea root powder. Various parameters like pH, biosorbent, dose, contact time and metal ion concentration are investigated using batch studies. A kinetic model study and isotherm model fitting study are studied using Langmuir and Freundlich isotherms. The Thermodyamic parameters ∆G, ∆H and ∆S are also seen. The results reveal that it follows pseudo first order kinetic model and also fit in the Langmuir and Freundlich isotherms. The results are very much encouraging. So, it can be used as low cost biosorbent in controlling the pollution. Keywords: Pollution, Heavy metal, chromium, Ipomoea carnea, Batch adsorption study, Kinetics Langmuir and Freundlich isotherms and Thermodynamic study.

Attachment of Acidithiobacillus ferrooxidans to pyrite in fresh and saline water and its fitting to Langmuir and Freundlich isotherms

Attachment of bacteria Acidithiobacillus ferrooxidans to pyrite was investigated in two different environment: fresh water and saline water (water with 35 g/L of NaCl), in both cases at pH 4. Adsorption isotherms were ?tted to the Langmuir and Freundlich models. The results showed that the bacteria adhere to pyrite to a greater extent in fresh water than in saline water. The Langmuir and Freundlich models ?tted well the data obtained in fresh water, showing a coeffcient of determination (R2) approximately equal to 0.8 for both models. On the other hand, in saline water the models did not show a good coeffcient of determination with a value approximately equal to 0.4 for both models.

Arsenic removal from water by Zr-γ- FeOOH nanoparticles

Zr-γ-FeOOH nanoparticle adsorbent for As(V) and As(III) removal was prepared by a chemical co-precipitation method. Compared with γ-FeOOH, the addition of Zr enhanced the adsorptive capacities of As(V) and As(III). The maximum adsorptive capacities for As(V) and As(III) were 69.81 and 94.25 mg/g, respectively (rate Fe:Zr =1:0.5) at pH= 7.0. The adsorption data accorded with Langmuir and Freundlich isotherms. The adsorption of As(III) by Zr- γ-FeOOH was found to be effective in wide pH range of 6–8. Competitive ions hindered the adsorption according to the decreasing sequence phosphate, sulfate, ammonium, chloride, magnesium and calcium. The high adsorptive capability and good performance on other aspects make the Zr-γ- FeOOH nanorods a promissing adsorbent for the removal of As(V) and As(III) from groundwater.

The maximum absorption capacities of γ-FeOOH, α-FeOOH, γ-Fe2O3 and α-Fe2O3 nanoparticles for As(V) and As(III)

γ-FeOOH, α-FeOOH, γ-Fe2O3 and α-Fe2O3 nanoparticle adsorbents for As(V) and As(III) removal were prepared by a chemical coprecipitation method. In the XRD diagrams the oxides appeared in the form of γ-FeOOH, α-FeOOH, γ-Fe2O3 and α-Fe2O3. These typical SEM images of the prepared samples were shown, which reveal that the nanoparticles were about 15 –30 nm. The maximum adsorption capacities of α- FeOOH for As(V) and As(III) were 77.28 and 78.65 mg/g; and γ-FeOOH were 63.75 and 88.99 mg/g respectively and higher than those of γ-Fe2O3 and α-Fe2O3 at pH= 6.0. The adsorption data accorded with Langmuir and Freundlich isotherms. The high adsorption capability and good performance on other aspects make the FeOOH nano particles being a promising adsorbent for the removal of As(V) and As(III) from groundwater.