Resumen de Study on adsorption behavior of rare earth elements onto magnetic nanocomposites of carboxymethyl chitosan, alginate and novel biodegradable polyamide
Rare Earth Elements (REEs) are known as the remarkable components in many technologies that are driving the modern world. They are widely used in chemical engineering, permanent magnets, fluorescent lighting, sensors, cell phones, lasers, electronics, rechargeable batteries, etc., because of their unique physicochemical properties. In order to supply the required amounts of these elements and fulfil their increasing demands, it is necessary to recovery this elements from secondary sources. Despite many efforts that have been done on recycling REEs, only less than 1% of REEs is recycled which can be due to the numerous challenges, such as collection of different final products and separation of REEs from other contaminants/metals.
Among the different techniques used for separation and purification of REEs from aqueous solution, biosorption has received great attention in recent decades. In this sense, biopolymers have been vastly utilized for the treatment of solutions containing metals. Alginate and chitosan are two kinds of biopolymers that have been utilized by many researchers due to being environmentally-friendly and effective.
The purpose of this work was to study the adsorption of Nd+3, Tb+3, and Dy+3 ions from aqueous solutions by using new magnetic nanocomposites based on calcium alginate (CA) and carboxymethyl chitosan (CMC) biopolymers, a novel synthetic biodegradable polyamide named poly(pyrimidine-thiophene-amide) (P(PTA)), and magnetic nanoparticles (Ni0.2Zn0.2Fe2.6O4). The synthesis of the P(PTA) was performed in two steps. Firstly, a diamine-phenol monomer (TMAPD) was synthesized.
Secondly, the polymer was obtained by polycondensation of TMAPD in 1,3-dipropyl imidazolium bromide ionic liquid as a solvent to avoid the use of the toxic triphenyl phosphite/N-methylpyrolidone/pyridine/LiCl that is required in the conventional direct polycondensation. The magnetic nanoparticles (Ni0.2Zn0.2Fe2.6O4) were synthesized by hydrothermal technique. The magnetic nanocomposites named CA/CMC/Ni0.2Zn0.2Fe2.6O4, CA/P(PTA)/Ni0.2Zn0.2Fe2.6O4, CMC/P(PTA)/Ni0.2Zn0.2Fe2.6O4 were synthesized by gelation method, and P(PTA)/Ni0.2Zn0.2Fe2.6O4 was synthesized by hydrothermal method.
Different techniques were used to analyze the synthesized materials. XRD was used to confirm the formation of the Ni0.2Zn0.2Fe2.6O4 and determine the size of the particles. The P(PTA) synthesis was confirmed by NMR analysis. The morphologies of the Ni0.2Zn0.2Fe2.6O4 and magnetic nanocomposites was investigated by FE-SEM technique. TGA was used for determining the thermal stability of the P(PTA) and magnetic nanocomposites. EDX was used for elemental analysis of the Ni0.2Zn0.2Fe2.6O4, P(PTA), and magnetic nanocomposites. VSM analysis was applied to determine the magnetic properties of the Ni0.2Zn0.2Fe2.6O4 and the magnetic nanocomposites. To determine the functional groups of all products, FT-IR analysis was applied.
Finally, the adsorption of the REEs was investigated in single and ternary batches, and column experiments. For the batch experiments, the effects of main parameters such as pH, contact time, adsorbent dosage, initial concentration, ionic strength, and temperature on the adsorption of the REEs were investigated in details. In addition, ¿G¿, ¿H¿, ¿S¿ as thermodynamic parameters were determined. In ternary system, response surface methodology based on central composite design (RSM-CCD) was used for the ternary system to predict the adsorption efficiency of the REEs and the interactions among different parameters. The kinetic and isotherm models were applied to fit the experimental data of the REEs adsorption in batch system. Besides, the obtained data from column system were fitted by the models.
