Ultrasonic-assisted Impregnation Research Articles

An efficient ultrasound assisted approach for the impregnation of room temperature ionic liquid onto Dowex 1 × 8 resin matrix and its application toward the enhanced adsorption of chromium (VI)

The work discussed in this paper is based on the utilization of ultrasound in conjunction with an ionic liquid (Aliquat 336) impregnated Dowex 1×8 resin for the effective adsorption of chromium. Ionic liquids are known for their selectivity toward metal extraction and ultrasonic medium offers efficient energy transfer for impregnating the ionic liquid in the resin matrix. The molecular interaction between the ionic liquid impregnated resin and chromium was studied through various physicochemical and spectroscopic techniques. The influence of various analytical parameters on the adsorption of Cr(VI) such as pH, adsorbent dosage, temperature and interference of foreign ions was studied in detail. Chromium (VI) was quantitatively adsorbed in the pH range of 3.5–4, with a high adsorption capacity of 230.9mgg−1 in conformity with the Langmuir isotherm model. The study of thermodynamic parameters showed that the adsorption process is exothermic and spontaneous. The adsorbent could be regenerated using 1molL−1 HCl–0.28molL−1 ascorbic acid mixture. Chromium could be effectively detoxified from an industrial effluent and finally the developed method was validated with the analysis of a certified reference material (BCR-715). The obtained results indicated that the ultrasonic assisted impregnation of the room temperature ionic liquid significantly enhances and improves the removal efficiency of Cr(VI).

Ultrasonic-assisted sodium hypochlorite oxidation of activated carbons for enhanced removal of Co(II) from aqueous solutions

Ultrasonic irradiation was employed to assist the modification of activated carbons (AC) by sodium hypochlorite, and tested for their ability to remove Co(II) from aqueous solutions. Modification of the activated carbon significantly enhanced their Co(II) adsorption capacity, which increased with the increasing NaOCl impregnating concentration. Ultrasonic-assisted impregnation can enhance the oxidation ability of the NaOCl solution, thus gave a higher adsorption capacity of Co(II) compared with the use of impregnation only. The Co(II) removal was a combination of adsorption and chemical precipitation. The optimal adsorption pH range for the native and modified AC was pH 7.0–8.5 and 4.5–8.5 respectively, above which precipitation of copper hydroxide became the main contributor to the cobalt removal. Cation exchange, electrostatic interaction, and surface complexation were demonstrated as the major mechanisms for the adsorption. Based on the XPS and FTIR analyses, Co(II) irons were considered to form monodentate charged complexes with the oxygen functionalities on the native AC, while they primarily formed multidentate coordination complexes within the modified carbon. The enhanced Co(II) removal by the ultrasonic-assisted NaOCl modified carbons was probably derived from their improved cation exchange capacity and higher content of adjacent aliphatic functional groups, which provided more complexation sites for cobalt.

Adsorption of Thiophene on Pt/Ag-Supported Activated Carbons Prepared by Ultrasonic-Assisted Impregnation

This work mainly involved the investigation of the adsorption of thiophene on Pt/Ag-supported activated carbons (ACs) prepared by ultrasonic-assisted impregnation (UI). The adsorption capacity of t...

Experimental study on two-stage catalytic hydroprocessing of middle-temperature coal tar to clean liquid fuels

Special Mo–Co/γ-Al2O3 and W–Ni/γ-Al2O3 catalysts with different metal loadings were prepared applying new synthesis technologies that combine ultrasonic-assisted impregnation and temperature-programming methods. Clean liquid oil was obtained from middle-temperature coal tar via hydrogenation in two-stage fixed beds filled with the laboratory made catalysts. The Mo–Co/γ-Al2O3 catalyst with 12.59wt.% Mo and 3.37wt.% Co loadings, and the W–Ni/γ-Al2O3 catalyst with 15.75wt.% W and 2.47wt.% Ni loadings were selected. The effects of pressure and liquid hourly space velocity on hydrogenation performance were investigated while other experimental conditions remained constant. Gasoline (⩽180°C) and diesel (180–360°C) fractions were separated from the oil product and analyzed. The two-stage reacting system was capable of removing nitrogen and sulfur from 1.69 and 0.98wt.% in the feed to less than 10ppm and 100ppm, respectively in the products. The results indicated that the raw coal tar could be considerably upgraded through catalytic hydroprocessing and high-quality fuels were obtained.

Adsorption of Dibenzothiophene on Ag/Cu/Fe-Supported Activated Carbons Prepared by Ultrasonic-Assisted Impregnation

This work is mainly involved with study of the adsorption of dibenzothiophene (DBT) on Ag/Cu/Fe-supported activated carbons (ACs) prepared by ultrasound-assisted impregnation (UI). Ag/AC-UI, Cu/AC-UI, and Fe/AC-UI were separately prepared by using impregnation of different metal salt solutions under ultrasound irradiation (UIr) and characterized by X-ray photoelectron spectroscopy (XPS) and CO-chemisorption experiments. Isotherms of DBT on the modified ACs were separately measured, and the effects of different metal ions loaded on the ACs on the amount of adsorbed DBT on the modified ACs are discussed. Results indicated that (1) the DBT adsorption capacity of the ACs modified by using impregnation without UIr followed the order: Ag/AC > Cu/AC > AC > Fe/AC; (2) the modification methods have significant influence on the adsorption abilities of the modified ACs toward DBT. The application of UIr to prepare metal ion-impregnated ACs can make the metallic particles on the carbon surfaces become finer and dispe...

Efficient and stable oxidative steam reforming of ethanol for hydrogen production: Effect of in situ dispersion of Ir over Ir/La 2O 3

La 2O 3-supported Ir catalyst was prepared by wetness impregnation method for the oxidative steam reforming of ethanol (OSRE). Fresh, reduced, and used catalysts were characterized by N 2 adsorption, H 2 chemisorption, XRD, FT-IR, TEM, and XPS. La 2O 3 would transform into hexagonal La 2O 2CO 3 during OSRE, which suppress coking effectively. Reduced Ir metal can interplay with La 2O 2CO 3 to form Ir-doped La 2O 2CO 3. It dynamically forms and decomposes to release active Ir nanoparticles, thereby preventing the catalyst from sintering and affording high dispersion of Ir/La 2O 3 catalysts at elevated temperatures. By introducing ultrasonic-assisted impregnation method during the preparation of a catalyst, the surface Ir concentration was significantly improved, while the in situ dispersion effect inhibited Ir from sintering. The Ir/La 2O 3 catalyst prepared by the ultrasonic-assisted impregnation method is highly active and stable for the OSRE reaction, in which the Ir crystallite size was maintained at 3.2 nm after 100 h on stream at 650 °C and metal loading was high up to 9 wt%.