Sepiolite/TiO2 and metal ion modified sepiolite/TiO2 nanocomposites: synthesis, characterization and photocatalytic activity in abatement of NOx gases

Effects of MnII and EuIII Cation Exchange in Sepiolite‐Titanium Dioxide Nanocomposites in the Photocatalytic Degradation of Orange G

“…Previous investigation of sepiolite cation exchange with Zn found improvement in photocatalytic activity, however, this was due to the formation of an intimately associated Zn-oxide co-catalyst rather than any modification of the electronic interface effect between sepiolite and titania. [39] Zinc is less redox sensitive than manganese and thus likely did not act as a h + scavenger as we suspect Mn did in our reaction and thus it performed well, albeit not as intended. This same study by Papoulis et al also found that Cu cation exchange into sepiolite inhibits catalytic activity due to enhanced recombination rate of the photogenerated charge carriers.…”

“…The photocatalytic activity of sepiolite-TiO 2 composite catalysts is influenced by a variety of factors, none quite so important as the surface area and microstructure. Knowing that Mn and Eu are unstable on the surface of sepiolite, corroborated by similar study of Cu and Zn, [39] we need to examine how this may have affected the physical surface area-promoting effect that sepiolite typically lends to TiO 2 . Nanoparticle agglomeration is largely a function of physical separation -the typical role of the support material -however, it can also can be influenced by the adjacent charge environment.…”

“…[36] Indeed, catalyst components with sub-optimal performance can be rendered highly active when composited, such as in BiSbO 4 /BiOBr and BiOCl/TiO 2 /sepiolite composite systems which enhance e À /h + separation and allow for rapid generation of superoxide radicals ( * O 2 À ), hydroxyl radicals ( * OH À ), and photo-generated holes (h + ). [37][38] Cation exchange has been shown to modify the net surface charge of clay minerals, and a recent study by Papoulis et al [39] investigated the role of cation exchange with Cu and Zn on sepiolite-TiO 2 nanocomposites for gas phase photocatalysis under UVR. The authors found that photocatalytic activity was enhanced in Zn-exchanged sepiolite-TiO 2 due to the combined effect of agglomeration inhibition by sepiolite and the in-situ formation of ZnO on the support surface, which acted as a cocatalyst.…”

“…Here, Eu and Mnexchanged sepiolites are produced and used as substrates for TiO 2 growth and deposition. Of interest are the potential different behaviors of Eu-and Mn-exchanged sepiolite compared to the Zn-and Cu-exchanged sepiolites prepared by Papoulis et al [39] with respect to photocatalytic activity. The catalysts were evaluated in the aqueous phase photocatalytic degradation of the azo dye, Orange G. Orange G was chosen as a model compound because azo dyes represent more than 50 % of the textile dyes on the market today; [1] these dyes and their precursors are suspected to be human carcinogens because they can form toxic aromatic amines.…”

Removing tar and nicotine from mainstream cigarette smoke using sepiolite-modified filter tips

“…Raw and modified sepiolite samples have found various applications (Galan, 1996; Murray, 1999): for example, as adsorbents (González-Santamaria et al , 2017), clarification agents (Erdoğan et al , 1996; Mirzaaghaei et al , 2017), bleaching earths (Tian et al , 2014; Laatikainen et al , 2015; Saneei et al , 2015) and catalysts (Al-Ani et al , 2018; Meşe et al , 2018). Acid activation (Çetişli & Gedikbey, 1990; Yebra-Rodriguez et al , 2003) and other chemical modifications (Shuali et al , 1991; Fitaroni et al , 2019; Papoulis et al , 2019) have a strong effect on the physicochemical properties of sepiolite, including on its crystal structure (Özdemir & Kıpçak, 2004), surface acidity (Bonilla et al , 1981), surface area (Jimenez-Lopez et al , 1978), nanoporosity (Rodriguez-Reinoso et al , 1981) and catalytic activity (Corma et al , 1984). The purpose of this study was to investigate the effects of mean particle size and the added mass of sepiolite granules as a filter additive for improving the removal of tar and nicotine in the MSS of cigarettes based on controlled experimentation.…”