Understanding the factors affecting the adsorption of Lanthanum using different adsorbents: A critical review.

Over the past few decades, removal and recovery of Lanthanum (La) have received great attention due to its significance in different industrial processes. In this review, the application of various adsorbents viz. biosorbents, commercial and hybrid materials, nanoparticles, nanocomposites etc. have been summarized in terms of the removal and recovery of La. The influence of various operating parameters including pH, dosage, contact time, temperature, coexisting ions, adsorption kinetics, isotherm and thermodynamics were investigated. Statistical analysis of the obtained data revealed that 60% and 70% of the authors reported an optimum pH of 4-6 and a dose of 1-2 g/L, respectively. It can be concluded on the basis of an extensive literature survey that the adsorbent materials (especially hybrids nanocomposites) containing carboxyl, hydroxyl and amine groups offered efficient La removal over a wide range of pH with higher adsorption capacity as compared to other adsorbents (e.g., biosorbents and magnetic adsorbents). Also, in most cases, equilibrium and kinetics were followed by Langmuir and pseudo second-order model and adsorption was endothermic in nature. To evaluate the adsorption efficiency of several adsorbents towards La, desorption and regeneration of adsorbents should be given due consideration. The main objective of the review is to provide an insight into the important factors that may affect the recovery of La using various adsorbents.