Hydrothermal treatment of hydroxycation precursor solutions

Low-temperature catalytic aqueous phase oxidation of microcystin-LR with iron-doped TiO2 pillared clay catalysts

TiO₂-PILCs and iron-doped TiO₂-PILCs were employed in order to destroy toxic microcystin-LR in the presence of H₂O₂ under the UV light. While less than 5% of the initial microcystin-LR and TOC disappeared in 240 min with the TiO₂-PILCs, almost complete conversion of microcystin-LR could be achieved in 180 min on the 10 wt% iron-doped TiO₂-PILC-A. On the exterior surface of the iron-doped TiO₂-PILCs were mainly located iron particles which had nano-sized diameter and Fe²⁺/Fe³⁺ cations together. Through Fenton-type oxidation on iron particles with H₂O₂, the big microcystin-LR molecules were converted primarily into smaller intermediate organic molecules of hydrocarbons, carboxylic acids and organic amines. The smaller intermediate molecules were believed to be diffused into the pores of the iron-doped TiO₂-PILCs and to be further mineralized into CO₂ and H₂O through the action of photocatalysis on the TiO₂ pillars. However, complete conversion of TOC could not be obtained due to the iron particle deactivation. XPS, TPO and TEM studies showed the continuous accumulation of carbonaceous materials onto the surface of iron particles.

Reuse of Pillaring Agent in Sequential Bentonite Pillaring Processes

This work describes the synthesis and characterization of pillared clays using a new pillaring method: the reuse of the pillaring solution. First, an Al pillared clay (PILC) was synthesized, and after filtration, the pillaring agent was stored and reused for an additional three pillaring procedures (P1, P2, and P3). The filtered pillaring solution was stored for one year and then reused for one additional pillaring procedure (P4). The samples were analyzed using XRD, N₂ physisorption measurements and chemical analysis (EDX). All of the samples exhibited basal spacings larger than 17 Å and BET surface areas greater than 160 m²/g. After the P4 pillaring, the pillaring agent was precipitated with a Na₂SO₄ solution, and the resulting solid was analyzed using XRD and SEM. The results indicated that even after a total of five pillaring procedures, Al₁₃ ions were still present in solution. Therefore, it is possible to reuse the pillaring solution four times and to even store the solution for one year, which is important from an industrial perspective.

Scale Up Pillaring: A Study of the Parameters That Influence the Process

Pillared clays (PILCs) are interesting materials mostly due to their high basal spacing and surface area, which make them suitable for adsorption and catalysis applications, for example. However, the production of these materials on industrial scale is dependent on research about what parameters influence the process. Thus, the objective of this work was to evaluate what parameters influence the pillaring procedure. For this, pillared clays were synthesized following three series of experiments. In the first series, the effect of the amount of water in a clay suspension was evaluated. The best results were obtained by using diluted suspensions (1 g of clay to 100 mL of water). In the second series, several pillaring methods were tested. In the third series, the amount of pillared clay was raised to 50 g. Fifty grams of pillared clay can be obtained using the pillaring agent synthesized at 60 °C with further aging for 24 h, and this material exhibited high basal spacing (17.6 Å) and surface area (233 m²/g). These values are comparable with the traditional pillaring method using only 3 g of clay.

Aplicação de Al-PILC na adsorção de Cu2+, Ni2+e Co2+ utilizando modelos físico-químicos de adsorção

Amostra de esmectita pertencente a Serra de Maicuru (Estado do Pará, Norte do Brasil, região amazônica) foi pilarizada com Al13, A Argila pilarizada com alumínio (Al-PILC) foi caracterizada por DRX, MEV e EDS. Para a análise textural foram utilizadas isotermas de adsorção-desorção utilizando o nitrogênio. Este artigo é dirigido ao estudo da adsorção de metais pesados. A adsorção dos íons de Cu2+, Ni2+e Co2+ foi realizadas com a matriz Al-PILC em temperatura ambiente com soluções aquosas contendo os íons metálicos. Os modelos de adsorção adotados foram os de Langmuir, Freundlich e Temkin que foram aplicados aos valores obtidos experimentalmente com regressão linear. A equação de Langmuir foi o melhor modelo de linearização com r = 0,999. A equação de Freundlich apresentou limitações em altas concentrações, mas foram obtidos valores (Kf e n) bastante aceitáveis utilizando este modelo. Os parâmetros foram utilizados para calcular a quantidade de Nf em função de Cs.