Abstract Mullite, an intermediate phase of the binary alumina-silica system, is one of the most important phases of ceramic products containing alumina and silica in the initial composition. Its stoichiometry ranges from 3Al2O3.2SiO2 (3:2) to 2Al2O3.SiO2 (2:1) and its crystalline structure is orthorhombic, characterized by the presence of octahedral chains of AlO6 interconnected by tetrahedral chains of aluminum-oxygen and/or silicon-oxygen (AlO4/SiO4). Properties such as high chemical and thermal stability, low thermal expansion and conductivity, and good mechanical strength enable a wide range of applications. Due to the relevance of this material, it is important for the scientific community to understand its microstructural characteristics, properties, methods of synthesis, and various applications. Therefore, this article aimed to make a comprehensive review on the mullite to gather and present to the reader a series of relevant information that makes it possible to deepen the knowledge about mullite.

Abstract The performance of Salvinia natans macrophyte to recover lead and chromium from single and bicomponent solutions in batch and fixed bed systems was investigated. Equilibrium data were obtained through isotherms and fitted to Langmuir, Freundlich and D-R models for a single component system. In the fixed bed study the breakthrough curves were carried out at three different ratios of concentrations for the bicomponent study and at the concentration of 1 mmol.L-1 for the single system. In order to know the biosorption mechanism, FT-IR analyses were performed for S. natans before and after the uptake of metal ions. The results showed different functional groups in the biomass and the ability of these groups to bind Cr+3 and Pb2+. Studies of the binary system of Cr3+/Pb2+ are not common in the literature, which makes the experimental data obtained in this work very important for providing information that could be used in adsorption processes.

Batch experiments were carried out for biosorption of Remazol Brilliant Blue R dye onto the macrophyte Salvinia natans. Effects of parameters such as initial dye concentration, pH, biosorbent dosage, contact time and temperature were investigated. Chemical and morphological characteristics of the biosorbent were evaluated before and after the biosorption process using methods such as Optical Microscopy (OM), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TA), Differential Scanning Calorimetry (DSC) and Infrared Spectroscopy (FT-IR). Sorption kinetics were conducted and followed a pseudo-second order kinetic model. Equilibrium data were well represented by the Langmuir model. Salvinia natans exhibited a maximum uptake of 61.9 mg.g-1. The Dubinin-Radushkevich model indicated that the adsorption takes place by a physical process. Thermodynamic parameters were estimated. The negative values of the Gibbs energy indicated the spontaneous nature of the adsorption. The entropy was positive and the positive value of the enthalpy showed that the process is endothermic.