Selective lanthanum recovery in the presence of sodium ions by N-(trimethoxysilypropyl)ethylenediamine triacetic acid (TMS-EDTriA)-modified silica

This study presents a novel approach investigating the silica particle modification using N-(trimethoxysilypropyl)ethylenediamine triacetic acid to enhance the recovery of lanthanum in three mixtures; 20 ppm La 3+ , 20 ppm La 3+ with 20 ppm Na + , and 20 ppm La 3+ with 100 ppm Na + . The influence of pH during modification was also tested. Characterization via Fourier Transform Infrared, Energy-dispersive X-ray Spectroscopy, and Thermogravimetric Analysis confirms the successful coating of propylene-(ethylenediamine)triacetic acid molecules on the silica surface, with modification under the basic conditions exhibiting the more accessible and stable coating. As a result, the La 3+ adsorption capacity of the modification under the basic conditions has been increased, making it suitable for effective recovery. Particles modified with a few drops of acid (0.075 mL L −1 ) recovered 95.27 % of La 3+ in 20 ppm La 3+ solution, while the unmodified particles recovered 82.62 %. The particles modified with 1.5 mL L −1 of acid recovered only 11.18 %. In the mixed solutions, the performance of the basic-modified particles showed a selectivity of more than 98 %. The particles modified with 9 mL L −1 of acid did not exhibit detectable La 3+ recovery in all types of solutions. Kinetic experiments show that modified particles with a few drops of acid (0.075 mL L −1 ) reach equilibrium for La sorption in less than 2 h, compared to 20 h for unmodified silica. • La 3+ recovery from aqueous solutions with TMS-EDTriA modified silica is improved. • The adsorption efficiency of three modification techniques is evaluated. • La 3+ ion selectivity, in the presence of sodium ions, is improved. • Adsorption time decreased by around 20 h, verified by kinetic investigations. • Modification under basic conditions reduces the surface charge of adsorbents.