This paper aims to explore the production of porous Nb2O5 pellets by pressing and adding anaerobic biomass (sludge) in order to evaluate the microstructure porosity. The thermal treatment temperature of the pellets varied between 300 ºC and 900 ºC. Their structural, morphological, and physical properties were measured, and the adsorption potential of Mn2+ and their reuse were evaluated. All samples had a monoclinic phase. Density average values of samples pressed using sludge ranged between 2.45 and 2.52 g.cm-3, while the one obtained without sludge pressing achieved higher values of around 2.72 g.cm-3. All samples presented high porosity values after the heat treatment (above 40%), which confirms the efficiency of sludge as a means to enhance porosity. These pellets were used for Mn2+ ions adsorption in aqueous medium. The Langmuir isotherm model was the one that achieved the best goodness-of-fit. In kinetic studies, the adsorption reaction was in accordance with second-order kinetics. Adsorbents in the form of pellets are environmentally friendly on account of their significant reuse and recycling potential. However, the particulate matter might become an environmental liability and incur high treatment costs. The samples proved to be reusable, promoting the adsorption of 67% of the Mn2+ after the fifth reuse cycle.

This research investigated the production of porous zinc oxide (ZnO) ceramics obtained by the replica method for water depollution by photocatalytic processes. Five photo-decolorization cycles were performed to analyze the reuse potential of the ceramics. Statistical analyses using R programming were conducted to investigate possible significant differences between them. The ceramics porosities were between 46.74 and 62.50% (depending on the composition). The most successful results were achieved in prepared ceramics from slurries containing 65% ZnO and 1% carboxymethylcellulose, in which the dye decolorization results reached 90.5% after 5 cycles, indicating a high reuse potential of these ceramics. Multivariate analysis proved the negative effect of increasing the heat treatment temperature on the evaluated properties. The best processing conditions to obtain porous ZnO ceramics by the replica technique were established through statistical tools, with very satisfactory results in the photo-decolorization potential of the investigated dye.

Plants absorb phosphorus from the soil, which has low levels of this element due to the poor solubility of these compounds in soil and high adsorption capacity of the element by soil particles. Therefore, the purpose of this study was to assess, using hydroxyapatite nanoparticles synthesized in the laboratory, the amount of phosphorus available under different conditions. The results showed that the phosphorus compound had highest solubility in hydroxyapatite sintered at 300°C in an oven for 2h and diluted to 0.05M with MilliQ water, corroborating the theory that the stronger the agglomeration of the nanoparticles, the fewer the pores and the poorer their solubility.