Supported ionic liquids for the efficient removal of acetylsalicylic acid from aqueous solutions

Acetylsalicylic acid, commercially available as aspirin, is one of the most used drugs in the world, being detected in several environmental compartments, including drinking water supplies. Given its environmental impact, the development of a cost‐effective technology capable of removing this pharmaceutical from water samples is of high relevance, for which materials based on silica chemically modified with ionic liquids (SILs) can be foreseen as a promising alternative. In this work, four SILs (with the chloride anion and imidazolium or tetraalkylammonium cations of different alkyl side chain length) were synthesized and characterized, and their potential for the adsorption of acetylsalicylic acid appraised by adsorption kinetics and isotherms. Envisioning their use to treat drinking water, the toxicity of all SILs towards the liver cell line Hep2G was determined. The best identified SIL, comprising the dimethylbutylammonium cation, displays a maximum adsorption capacity of 0.08 mmol/g, being 1 g of this material sufficient to treat ca. 14,500 L of water containing 1 μg/L of acetylsalicylic acid (under ideal conditions). Furthermore, this material has a negligible toxicity towards the liver cell line Hep2G. The results obtained reinforce the potential of SILs as alternative adsorbents to effectively remove a cetylsalicylic acid from aqueous solutions, and may be envisioned as a promising strategy for the treatment of wastewater and drinking water.publishe

Sorption of cadmium (II) ion from aqueous solution onto sweet potato (Ipomoea batatas L.) peel adsorbent:characterisation, kinetic and isotherm studies

Sweet potato peels was used for the removal of Cd (II) from aqueous solutions. The residue was characterised using SEM, EDX, XRF, N2 BET, TGA and ATR-FTIR. Sorption of Cd (II) was carried out by varying pH, contact time and initial ion concentration at 25 °C and the results showed a strong dependence of the ion removal on the adsorbate pH with optimum observed at pH 7. Kinetics of Cd (II) sorption indicates optimum time of 180 min and the removal of Cd (II) occurred via a fast initial uptake. This was modelled using the pseudo first, pseudo-second and intraparticle diffusion models. The pseudo-first order gave a better description of the uptake kinetics than the pseudo-second order model with an r2 value of 0.99. The intraparticle-diffusion model showed that sorption had multi-linear steps indicating that the intraparticle-diffusion is not the only rate controlling step in Cd (II) sorption. FTIR analysis of the PTPS before and after adsorption of Cd (II) indicates that some functional groups such as hydroxyl, carbonyl and carboxylate groups may be involved in metal ion sorption. Isotherm modelling of Cd (II) sorption was carried out using the Langmuir and Freundlich isotherms using a non-linear optimisation. The Langmuir isotherm gave a better fit for Cd (II) sorption and maximum loading capacity (qmax) was 18 mg g−1 with an isotherm constant of 5.21 × 10−3 l mg−1 and r2 value of 0.99 at 25 °C. Hence, the PTPS residue was found to be a promising adsorbent for Cd (II) removal from aqueous streams