Study of isotherm and kinetic models of lanthanum adsorption on activated carbon loaded with recently synthesized Schiff’s base

A new effective adsorbent was developed for a selective extraction and determination of lanthanum from aqueous media by use of inductively coupled plasma-optical emission spectrometry. The new adsorbent was based on activated carbon modified with Schiff’s base derived from diethylenetriamine and 3,4-dihydroxybenzaldehyde (AC-DETADHBA). Isotherm and kinetic models were systematically investigated to evaluate the analytical potential of the AC-DETADHBA phase toward La(III) by employing a batch adsorption technique. Surface properties of AC-DETADHBA were characterized by Fourier transform infrared spectrometry. The maximum static adsorption capacity was determined to be 144.80 mg g−1 at pH 6, providing that the adsorption capacity of La(III) was improved by 61.79% with the AC-DETADHBA phase as compared to the carboxylic acid derivative of activated carbon after only 1 h contact time. Adsorption isotherm results demonstrated that the adsorption process was mainly monolayer on a homogeneous adsorbent surface, confirming the validity of Langmuir adsorption isotherm model. Data obtained from kinetic models study indicated that the adsorption of La(III) onto the AC-DETADHBA phase obeyed a pseudo second-order kinetic model. In addition, results of thermodynamic investigation also revealed that the adsorption mechanism of AC-DETADHBA toward La(III) is a general spontaneous process and favorable. The effect of several coexisting metal ions displayed that the recovery of La(III) was not affected by the medium composition containing either individual or mixed metals. Finally, the newly proposed method gave satisfactory results for the determination of La(III) in environmental water samples.