The aim of this article is to review current knowledge related to the synthesis and characterization of sol gel-derived SBA-16 mesoporous silicas, as well as a review of the state of the art in this issue, to take stock of knowledge about current and future applications. The ease of the method of preparation, the orderly structure, size and shape of their pores and control, all these achievable through simple changes in the method of synthesis, makes SBA-16 a very versatile material, potentially applicable in many areas of science and molecular engineering of materials.

This work informs on the green synthesis of a novel adsorbent and its adsorption capacity. The adsorbent was synthesized by the combination of iron nanoparticles and cellulose nanofibers (FeNPs/NFCs). Cellulose nanofibers (NFCs) were obtained from Moringa (Moringa oleifera Lam.) by a pulping Kraft process, acid hydrolysis, and ultrasonic methods. The adsorption method has advantages such as high heavy metal removal in water treatment. Therefore, cadmium (Cd) and lead (Pb) adsorption with FeNP/NFC from aqueous solutions in batch systems was investigated. The kinetic, isotherm, and thermodynamic parameters, as well as the adsorption capacities of FeNP/NFC in each system at different temperatures, were evaluated. The adsorption kinetic data were fitted to mathematical models, so the pseudo-second-order kinetic model described both Cd and Pb. The kinetic rate constant (K₂), was higher for Cd than for Pb, indicating that the metal adsorption was very fast. The adsorption isotherm data were best described by the Langmuir–Freundlich model for Pb multilayer adsorption. The Langmuir model described Cd monolayer sorption. However, experimental maximum adsorption capacities (q_{e exp}) for Cd (>12 mg/g) were lower than those for Pb (>80 mg/g). In conclusion, iron nanoparticles on the FeNP/NFC composite improved Cd and Pb selectivity during adsorption processes, indicating the process’ spontaneous and exothermic nature.

The contamination of groundwater by arsenic and fluoride is a major problem worldwide, causing diseases in the population that uses these waters for their consumption. Therefore, the removal of these types of pollutants from groundwater is a very important issue. In this work, the removal of arsenate and fluoride from aqueous solutions by using aluminum-modified guava seeds (Al-GSs) was evaluated. Batch-type adsorption experiments were carried out with aqueous solutions of As(V) and F⁻ and Al-GSs. The kinetic and equilibrium parameters of adsorption were determined, as well as the effects of adsorbent dose and pH. The adsorbent was characterized by scanning electron microscopy and infrared spectroscopy in order to determine its morphology and the functional groups present in the material. The results showed that hydroxyl and carboxyl are the main groups involved in the adsorption of As(V) and F⁻. The fluoride adsorption kinetics indicate that the equilibrium time was reached at 150 min and it can be described by the Lagergren model, while for As(V) the equilibrium time was lower (120 min) and the kinetic data were fitted well to the pseudo-second-order model. The Langmuir-Freundlich model can describe the adsorption equilibrium data in all cases. The fluoride adsorption capacity by Al-GS was 0.3445 mg/g, and for As(V) it was 4 mg/g. It can be established that the removal of arsenates and fluoride in Al-GSs is due to chemisorption on a heterogeneous surface.