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.