Adsorptive oxidation of sulfides catalysed by δ-MnO2 decorated porous graphitic carbon composite. (November 2020)

• Record Type: Journal Article
• Authors: Edathil, Anjali Achazhiyath; Kannan, Pravin; Banat, Fawzi
• Is Part Of: Environmental pollution. Volume 266:Part 3(2020)
• Publication Date: 2020-11
• Subjects: δ-MnO2 -- Adsorption -- Sulfide wastewater -- Alginate -- Porous graphitic carbon; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2020.115218
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: Removal of dissolved sulfide contaminants from aqueous model solution using bio-derived porous graphitic carbon (PGC) impregnated with δ-MnO2 was investigated. The composite adsorbent was synthesized using the chemical wet deposition method wherein MnO2 was deposited on carbon walls through an in-situ reaction between permanganate and ethanol. Formation of transition metal oxide of manganese in the form of birnessite nanoparticles on interconnected PGC cell structure was confirmed by transmission electron microscopy, scanning electron microscopy, elemental analysis, and X-Ray diffraction characterization studies. The composite nanomaterial was tested for sulfide removal from aqueous solution at various conditions, including the pH, adsorbent dosage, initial solution concentration, and contact time. Adsorption results demonstrated an excellent adsorption capacity of ca. 90% within 20 min of contact time at 298 K. Equilibrium data collected from batch adsorption experiments fitted well with the Langmuir isotherm model (KL = 190 L/mg; R 2 = 0.99). The maximum adsorption capacity of the composite was estimated as 526.3 mg S 2− /g at highly alkaline conditions compared to ca. 340 mg/g for a δ-MnO2 adsorbent. Adsorptive oxidation of sulfides on composite MnO2 -PGC adsorbent was found to be controlled by the chemisorption process in accordance with the pseudo-second-order reaction model. Characterization of spent adsorbents revealed that sulfide was removed through adsorptive oxidation resulting in the formation of agglomerated particles of metal sulfate complexes and elemental sulfur. Analysis of reaction mechanism revealed that both MnO2 and PGC played a role in the adsorptive oxidation of sulfides to CaSO4 and elemental sulfur. Graphical abstract: Image 1 Highlights: δ-MnO2 /porous graphitic carbon nanocomposite synthesized by in-situ wet deposition. Surface functionalized PGC and precipitated δ-MnO2 catalyzed oxidation of sulfides. Sulfides species converted to metal sulfates and sulfur, and removed by adsorption. Equilibrium best-described by Langmuir model with an uptake capacity of 526.3 mg/g. Kinetic intra-particle diffusion model suggested multiple rate-controlling steps. Abstract : δ-MnO2 /PGC nanocomposite synthesized using a facile in-situ wet deposition technique exhibited superior sulfide uptake capacity.