Adsorption of 2‐Chlorophenol on the Surface of Silica‐ and Alumina‐Supported Iron Oxide: An FTIR and XPS Study

Abstract

Abstract2-chlorophenol (2-CPh) adsorption on the surface of silica, alumina, silica-and aluminasupported iron oxides at 30 °C and 250 °C was examined. The formation of a carbanion chlorophenolate/chlorophenoxy radical intermediate on the surface of silica and alumina surfaces is identified by in-situ FTIR analysis. The IR spectra of 2-CPh adsorbed on the supported iron oxide at 250 °C highlight significant differences in the adsorption complex between 2-CPh and the two supported iron oxides ( silica and alumina).Under conditions of low coverage of 2-CPh on the surface of these catalysts, FTIR analysis suggests that the adsorption of 2-CPh on the surface of silica-supported iron oxide commences with the formation of a chlorophenolate species, where in contrast 2-CPh creates a surface formate species on alumina-supported iron oxide. Moreover, stronger bonds of 2-CPh, and higher concentration of the carbonate species, are evident on the alumina surfaces, based on both FTIR and XPS analyses.

Adsorption Configurations of 2-Chlorophenols on Colloidal Silica

“…Upon adsorption of 2-CP, new bands appeared at 1280, 1482 and ~3030-3070 cm −1 with an observation of complete disappearance of the isolated O-H groups at 3743 cm −1 while all the other bands of untreated silica showed significant losses in their intensities. These observations suggest that the 2-CP chemisorbed on the surface [33,34]. This behavior of chemisorption is further explained in Figure 4(b) where the difference spectrum (2-CP adsorbed-bare silica) is depicted.…”

“…The new bands appeared at 1280, 1482 and 3050 cm −1 are assigned to the C-O stretching, C〓C stretching of the benzene ring, and aromatic C-H stretching modes, respectively, of 2-CP [31]. It should note here that the 1280 cm −1 band appeared at pH 9 is more intense compared to that observed at pH 5 even though the amount adsorbed (64%) was lesser than that observed at pH 5 (74%) [33,34].…”

“…Though the pH 9 of the medium is higher than pKa of 2-CP (8.52) the above observations clearly show the supportive information for the proposed adsorbed species. When the pH is higher than pKa, anionic species formed may have a high tendency towards interacting with silica by the elimination of H 2 O and HCl molecules [33]. However, previous studies on the adsorption of 2-CP on fly ash and Ca-montmorillonite showed the reduction in the adsorption capacity when the pH was higher than pKa where the dissociated organic molecules experience the repulsion from the negatively charged surface [38].…”

Complementary Bifunctional Unique Properties of (α,β)‐PbO Nanoparticles for Efficient Catalysis and Adsorption for Water Remediation

“…Further, the better correlation of q e and q max values (within ±0.89% error limit) calculated from the Langmuir model with the respective experimentally calculated values suggested monolayer adsorption of RR‐120 on the homogenous surface of [PbO] b adsorbent. Furthermore, Langmuir parameter, R L was calculated as 0.0129 signifying favourable adsorption of the dye on the adsorbent (0< R L <1) . Similarly, the values of and n calculated as 236.66 and 6.91 from the Freundlich isotherm model indicated the favourable adsorption process, although it suffered from inferior quality in correlation.…”

Surface catalysed PCDD/F formation from precursors - high PCDF yield does not indicate de novo mechanism!

“…Also, some researchers specified that the presence of other combustion by-products (present in large excess, compared to these two typical PCDD/F precursors) is critical in the formation of PCDD/F: by their in-situ transformation to such precursors they further increase the PCDD/F output (De Jong et al, 2004; Cieplik et al, 2006). However, such conversions require the presence of active metals, as pure silica or aluminas do not yield a significant conversion of precursors (Mosallanejad et al, 2016, 2015, 2014). …”