Experimental and Theoretical Studies of Methyl Orange Uptake by Mn–Rich Synthetic Mica: Insights into Manganese Role in Adsorption and Selectivity

Abstract

Manganese–containing mica (Mn–mica) was synthesized at 200 °C/96 h using Mn–carbonate, Al–nitrate, silicic acid, and high KOH concentration under hydrothermal conditions. Mn–mica was characterized and tested as a new adsorbent for the removal of methyl orange (MO) dye from aqueous solutions. Compared to naturally occurring mica, the Mn–mica with manganese in the octahedral sheet resulted in enhanced MO uptake by four times at pH 3.0 and 25 °C. The pseudo–second order equation for kinetics and Freundlich equation for adsorption isotherm fitted well to the experimental data at all adsorption temperatures (i.e., 25, 40 and 55 °C). The decrease of Langmuir uptake capacity from 107.3 to 92.76 mg·g−1 within the temperature range of 25–55 °C suggested that MO adsorption is an exothermic process. The role of manganese in MO selectivity and the adsorption mechanism was analyzed via the physicochemical parameters of a multilayer adsorption model. The aggregated number of MO ions per Mn–mica active site ( n ) was superior to unity at all temperatures signifying a vertical geometry and a mechanism of multi–interactions. The active sites number (DM) of Mn–mica and the total removed MO layers (Nt) slightly changed with temperature. The decrease in the MO adsorption capacities (Qsat = n·DM·Nt) from 190.44 to 140.33 mg·g−1 in the temperature range of 25–55 °C was mainly controlled by the n parameter. The results of adsorption energies revealed that MO uptake was an exothermic (i.e., negative ΔE values) and a physisorption process (ΔE < 40 kJ mol −1). Accordingly, the adsorption of MO onto Mn–mica was governed by the number of active sites and the adsorption energy. This study offers insights into the manganese control of the interactions between MO ions and Mn–mica active sites.

Polyaniline nanofibers, a nanostructured conducting polymer for the remediation of Methyl orange dye from aqueous solutions in fixed-bed column studies

“…q max (mg/g) References Amino-crosslinked hypromellose (AHM) 15.56 [34] Blast furnace slag acid-alkali precipitate (BFSAP) 167 [94] Protonated cross-linked chitosan 180.2 [95] Coffee ground activated carbon 658 [96] Waste ash 35.614 [36] Chitosan-coated montmorillonite clay 7.34 [97] Alkali-Activated Polypyrrole-Based Graphene Oxide 520.8 [98] Manganese-containing mica (Mn-mica) 107.3 [35] PANI NFs 312.8 Present study of MO ions within the column bed in higher bed lengths may result in the observed bed capacity upsurge, hence larger volumes of MO solution could be treated. Presented in Table 3 are the values of the amount of solution treated at breakthrough point, (V b ) which were found to be 8.64 L, 17.64 L, and 29.16 L for bed lengths of 3, 5.5, and 9 cm, respectively.…”

“…To date, multiple natural and artificial sorbents have been employed for MO remediation from wastewater. These include polypyrrole nanofibers [ 28 ], activated carbon [ 30 ], modified coffee waste [ 31 ], chitosan hydrogel beads [ 32 ], magnetic iron oxide/carbon nanocomposite [ 33 ], amino-crosslinked hypromellose [ 34 ], bentonite and coffee grounds activated [ 34 , 35 ], waste ash [ 36 ], populous tree leaves [ 37 ], manganese-rich synthetic mica [ 35 ], etc . However, all of these adsorbents were explored in batch adsorption mode, which is well acknowledged to provide insufficient information for scaling up [ 38 , 39 , 40 ].…”

Outstanding Performance of a New Exfoliated Clay Impregnated with Rutile TiO2 Nanoparticles Composite for Dyes Adsorption: Experimental and Theoretical Studies

“…The pH of the point of zero charge (pH PZC ) was determined as follows [9]: 50 mL of 0.1 M KCl was taken in a clean glass Erlenmeyer. The initial pHs (pHi) of these solutions were adjusted at pH values ranging from 2.0 to 10.0.…”

“…The appropriateness of these advanced models to fit MB and MO adsorption data was compared, and the best one was identified according to the determined coefficient R 2 values [13]. These advanced models are described as follows [9,13,31]:…”

“…A multilayer model, as the general form of ASPMs, was also implemented in this study to fit the MB and MO adsorption processes. The following equations (Equations ( 4)-( 9) are used to determine the parameters of the multilayer model [9]:…”