IL-Functionalized Mg3Al-LDH as New Efficient Adsorbent for Pd Recovery from Aqueous Solutions.

Palladium is a noble metal of the platinum group metals (PGMs) with a high value and major industrial applications. Due to the scarce palladium resources, researchers' attention is currently focused on Pd ions recovery from secondary sources. Regarding the recovery process from aqueous solutions, many methods were studied, amongst which adsorption process gained a special attention due to its clear advantages. Moreover, the efficiency and the selectivity of an adsorbent material can be further improved by functionalization of various solid supports. In this context, the present work aims at the synthesis and characterization of Mg3Al-LDH and its functionalization with ionic liquid (IL) (Methyltrialkylammonium chloride) to obtain adsorbent materials with high efficiency in Pd removal from aqueous solutions. The maximum adsorption capacity developed by Mg3Al-LDH is 142.9 mg Pd., and depending on the functionalization method used (sonication and co-synthesis, respectively) the maximum adsorption capacity increases considerably, qmax-Mg3Al IL-US = 227.3 mg/g and qmax-Mg3Al IL-COS = 277.8 mg/g.

Development of New Efficient Adsorbent by Functionalization of Mg3Al-LDH with Methyl Trialkyl Ammonium Chloride Ionic Liquid.

The present paper describes a new way of obtaining an efficient adsorbent material by functionalization of Mg3Al layered double hydroxides (LDH) with methyl trialkyl ammonium chloride-ionic liquid (IL) using two methods: ultrasound and cosynthesis. Layered double hydroxides are good solid support for the functionalization with ionic liquids due to their well-ordered structure. The immobilization of the ILs in suitable solid supports combine the advantages of the ILs with the properties of the solid supports bringing more benefits such as use of lower quantity of ILs and avoiding of ILs loss in the aqua phase which overall decrease the treatment costs. In case of ultrasound method of functionalization is assured a uniform distribution of IL on the solid surface, but through immobilization by cosynthesis due to the tunable properties of LDH, is assured an intercalation of the ILs between the LDH layers. This fact was highlighted by the X-ray diffraction (RXD), scanning electron microscopy (SEM) analyses and Fourier-transform infrared (FTIR) spectroscopy of the obtained adsorbent. The added value brought by the functionalization of Mg3Al with the studied IL was underlined by the adsorption studies conducted in the treatment process of water with diclofenac content. Kinetic, thermodynamic, and equilibrium studies were performed. DCF adsorption onto the studied materials correspond to a chemisorption, the pseudo-second-order kinetic model describing the most accurately the experimental data. DCF adsorption onto the studied materials occurs as a heterogeneous process, with the experimental data fitting best with the SIPS isotherm. The sample obtained through cosynthesis developed a maximum adsorption capacity of 648 mg/g.

Adsorption of Orange II Onto Zn2Al-Layered Double Hydroxide Prepared From Zinc Ash.

The dye industry is one of the largest water consuming industries, and at the same time generates large quantities of wastewaters. The resulting wastewaters require proper treatment before discharge, because the dye contents have a negative effect on the water body and organisms present in it. The most efficient treatment method for water containing dyes is represented by adsorption processes. The challenge with these adsorption processes is to develop new, efficient, viable, and economic adsorbent materials. Therefore, in the present paper, the performance of Zn2Al-layered double hydroxide, prepared from an industrial waste (zinc ash) as a zinc source, was investigated in the Orange II dye adsorption process. The Zn2Al-layered double hydroxide prepared from secondary sources presents similar morphological and structural characteristics as those prepared from analytical grade reagents. The influence of initial dye concentration, adsorption time, solid:liquid ratio, pH, and temperature was evaluated in order to confirm the benefit of this waste valorization. A comparison with the reference Zn2Al-layered double hydroxide prepared from analytical grade reagents was performed and the results show that due to the small presence of impurities, the material prepared from zinc ash shows better adsorption capacities (qmax,exp = 42.5 mg/g at 293 K) than the material prepared from reagents (qmax,exp = 36.9 mg/g at 293 K), justifying the utilization of secondary sources for layered double hydroxides preparation. The proposed treatment process presents advantages from both economic and environmental protection point of view.