ARTICLE | doi:10.20944/preprints202208.0289.v1
Subject: Chemistry, Applied Chemistry Keywords: layered double hydroxides; magnetic nanoparticles; phthalocyanines; antibiotics removal
Online: 16 August 2022 (11:12:42 CEST)
Considerable efforts have been made in recent years to identify an optimal treatment method for the removal of antibiotics from wastewaters. A series of supramolecular organic-inorganic magnetic composites containing Zn-modified MgAl LDHs and Cu-phthalocyanine as photosensitizer have been prepared with the scope to β-lactam antibiotics removal from aqueous solutions. The characterization of these materials confirmed the anchorage of Cu-phthalocyanine onto the edges of the LDH lamellae, with a negligible part inserted in the interlayer space. The removal of β-lactam antibiotics occurred via a concerted adsorption and photocatalytic degradation. The efficiency of the composites was depending on i) the LDH: magnetic nanoparticle (MP) ratio, that is strongly correlated to the textural properties of the catalysts, and ii) the phthalocyanine loading in the final composite. A maximum of the efficiency was achieved with a removal of ~93% of antibiotics after 2h of reaction.
ARTICLE | doi:10.20944/preprints202206.0109.v1
Subject: Chemistry, Chemical Engineering Keywords: Layered Double Hydroxides (LDH); mechano-chemical / co-precipitation synthesis; organic alkalis (tetramethylammonium hydroxides); memory effect; Claisen-Schmidt condensation; self-cyclohexanone condensation
Online: 8 June 2022 (03:23:29 CEST)
Using of the organic base tetramethylammonium hydroxides (TMAH) is a viable, cheap and fast route, for the MgZnAl-LDH type materials synthesis by both co-precipitation and mechano-chemical methods. TMAH provided several advantages as smaller quantity of water required in the washing step compared to the use of inorganic alkalis, prevention of LDH contamination with alkali cations, acting as template molecule in texture tailoring along with disadvantages as its presence in small quantities in the resulting layered materials. Regardless the use of organic / inorganic bases and co-precipitation / mechano-chemical methods, zincite stable phase was found in all the synthesized solids. The basicity of catalysts followed the trend: mixed oxides > reconstructed > parent LDH. The memory effect of LDH is supported only by the presence of Mg and Al cations, while Zn remains as zincite stable phase. The catalytic activities for Claisen-Schmidt condensation of benzaldehyde with cyclohexanone provided values higher than 90% after 2h, with a total selectivity in 2,6-dibenzylidenecyclohexanone, while in self-condensation of cyclohexanone no more than 7.29% after 5h. These behaviors depended on catalysts basicity as well as the planar rigidity of the compound.