A supported dendrimer with terminal symmetric primary amine sites for adsorption of salicylic acid.

The aim of this work is to evaluate the uptake of salicylic acid (SA), an emerging pollutant, using a nano-polar dendrimer containing highly branched terminal symmetric amine groups immobilized on mixed-oxide nanoparticles of SiO2-Al2O3. Several variables, including the effect of initial SA concentration, contact time, temperature, initial pH, adsorbent dosage, interfering ions, and the hydrophobicity of the adsorbent (SANP-G1.0) were studied. Because of the electrostatic and hydrogen bonding interactions between SA and the amine functional sites of the nano-polar dendrimer, the adsorbent featured a remarkable SA uptake capacity of over 254.5 mg/g after 5 min contact time. The solution pH had a considerable impact on SA uptake by SANP-G1.0, with optimal uptake occurring around pH 2-5. Kinetic and isotherm studies confirmed that SA removal could be fit with the Sips and pseudo-second-order kinetic models, respectively, implying that a chemical process dominates SA uptake by the SANP-G1.0. The uptake of SA decreased at elevated temperature, demonstrating that this is a chemically and naturally exothermic process between 15 and 80 °C. The uptake efficiency of the reused nanodendrimer was 54% after the tenth adsorption-desorption cycle. Moreover, the SANP-G1.0 showed a high capacity for adsorbing SA from Cayuga Lake water. We studied the possible mechanism of SA uptake, including the effect of interfering ions, using zeta potential, X-ray photoelectron spectroscopy, infrared spectroscopy, and the hydrophobicity of the nanodendrimer. The prepared supported dendrimer, featuring high chemical and mechanical stability, demonstrates good reusability for SA adsorption from aqueous media. An artificial neural network (ANN) model was also designed to simulate SA uptake by SANP-G1.0. The results revealed an excellent fit between the ANN-modeled and experimental data, with a correlation coefficient (R2) of 0.9841.