Kinetic Investigation of Silica Gel Chemically Modified by Ethylenediamine Bis(Methylene Phosphonic Acid) for Adsorption of Au(Iii)

Kinetics and Isotherm for Adsorption of Hg(II) from Aqueous Solution by Silica Gel Encapsulated by Polyamine-Functionalised Polystyrene

This paper presents the synthesis of two novel composite adsorbents, namely (i) silica gel microspheres encapsulated with diethylenetriamine-functionalised polystyrene (SG – PS – SO2 – DETA) and (ii) silica gel microspheres encapsulated with triethylenetetramine-functionalised polystyrene (SG – PS – SO2 – TETA). Our objective was to design adsorbents with high adsorption capacities via different functional groups, and the results showed that SG – PS – SO2 – TETA has an excellent adsorption capacity for Hg(II) ions. A kinetic investigation of SG – PS – SO2 – DETA and SG – PS – SO2 – TETA for adsorption of Hg(II) is reported here and the results show that SG – PS – SO2 – DETA/SG – PS – SO2 – TETA could attain their saturation adsorption capacities within 4 h, and their excellent adsorption capacities for Hg(II) were 0.252 mmol g −1 and 0.383 mmol g −1, respectively. Moreover, the kinetic data indicated that the adsorption process is governed by the film diffusion. Langmuir and Freundlich isotherm models were applied to analyse the experimental data and the maximum adsorption capacities of SG – PS – SO2 – DETA and SG – PS – SO2 – TETA for Hg(II) were 46.54 mg g −1 and 113.47 mg g −1, respectively.

Kinetic and Thermodynamic Studies of Adsorption of Heavy Metal Ions from Fuel Ethanol

The cleaning treatment of fuel ethanol plays an important role in its effective utilisation, and adsorption is one useful process to remove heavy metal ions from fuel ethanol solutions. In this work, a novel silica gel adsorbent functionalised with an aminophosphonic acid (denoted as SG-T-P) was developed, characterised, and used to remove heavy metal ions from fuel ethanol solutions. The adsorption properties of SG-T-P for Hg(II), Cu(II), Mn(II), Co(II), Zn(II), Ni(II), Fe(III) and Cd(II) in ethanol solutions were studied, revealing that SG-T-P had an excellent adsorption capacity for Hg(II). Furthermore, the kinetic data indicated that the adsorption process was governed by film diffusion and followed a pseudo-second-order rate model for SG-T-P. The thermodynamic parameters Δ G, Δ H and Δ S were – 6.80kJ mol−1 (35°C), 55.49 kJ mol−1, and 203.92 J K −1 mol −1, respectively. Thus, SG-T-P is effective and useful for the removal of Hg(II) from fuel ethanol solutions, and its good adsorption ability make it a promising candidate material for mercury uptake.