Synthesis and Characterization of the Hybrid Clay‐Based Material Montmorillonite–Melanoidin: A Potential Soil Model

Abstract

The study of the interactions among metals, minerals, and humic substances is essential in understanding the migration of inorganic pollutants in the geosphere. A considerable amount of organic matter in the environment is associated with clay minerals. To understand the role of organic matter in the environment and its association with clay minerals, a hybrid clay‐based material (HCM), montmorillonite (STx‐1)–melanoidin, was prepared from l‐tyrosine and l‐glutamic acid by the Maillard reaction. The HCM was characterized by elemental analysis, nuclear magnetic resonance, x‐ray photoelectron spectroscopy (XPS), scanning transmission x‐ray microscopy (STXM), and thermal analysis. The presence of organic materials on the surface was confirmed by XPS and STXM. The STXM results showed the presence of organic spots on the surface of the STx‐1 and the characterization of the functional groups present in those spots. Thermal analysis confirmed the existence of organic materials in the montmorillonite interlayer, indicating the formation of a composite of melanoidin and montmorillonite. The melanoidin appeared to be located partially between the layers of montmorillonite and partially at the surface, forming a structure that resembles the way a cork sits on the top of a champagne bottle.

Sorption of Np(V) onto hybrid clay-based materials: Montmorillonite-melanoidin

“…With increasing pH, dissolution of organics was observed, which was confirmed by UV/Vis absorption spectroscopy [12]. Neptunium was also determined in the organic fraction >1 kDa, which was separated by ultrafiltration [14].…”

“…The results regarding functional groups in the studied HCMs indicate preferential formation of aliphatics as reaction products [12].…”

“…HCMs may be used as soil models in batch experiments. The preparation and characterization of the HCMs are described in detail elsewhere [12]. Basically HCMs are the solid residue obtained after separation of the condensation and dehydration products of glutamic acid (GHS) or tyrosine (THS) with xylose as a reducing sugar in the presence of STx-1 montmorillonite.…”

“…The composites were synthesized in a batch experiment starting from 16.5 g of xylose, 13.5 g of L-tyrosine or 11 g of glutamic acid, 3.2 g of Na-montmorillonite STx-1, and 150 ml of water, as described in detail elsewhere [12]. The results regarding functional groups in the studied HCMs indicate preferential formation of aliphatics as reaction products [12].…”

“…VICENTE VILAS,KRATZ 66 crease with pH, flattening out at pH 8-8.5 [17]. The presence of the melanoidins with a high content in carboxy groups in the montmorillonite (GHS) enhances the sorption up to pH of about 7.1; above this pH, the As we described in [12], the organic material present in the HCMs is released into the aqueous phase with increasing pH; therefore, the interaction of the released organics with neptunium was also studied. After the phase separation, a fraction of the supernatant was subjected to ultrafiltration with 1 kDa Microsep 1 kOmega membrane filters (Pall Life Sciences, USA) in combination with centrifugation (Fritz Bayet OHG, Frankfurt am Main, Germany) at about 2500 rpm for 20 min as described elsewhere [14].…”