Removal of Methylene Blue from Water Using Magnetic GTL-Derived Biosolids: Study of Adsorption Isotherms and Kinetic Models

Abstract

Global waste production is significantly rising with the increase in population. Efforts are being made to utilize waste in meaningful ways and increase its economic value. This research makes one such effort by utilizing gas-to-liquid (GTL)-derived biosolids, a significant waste produced from the wastewater treatment process. To understand the surface properties, the biosolid waste (BS) that is activated directly using potassium carbonate, labelled as KBS, has been characterized using scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), and Brunauer–Emmett–Teller (BET). The characterization shows that the surface area of BS increased from 0.010 to 156 m2/g upon activation. The EDS and XPS results show an increase in the metal content after activation (especially iron); additionally, XRD revealed the presence of magnetite and potassium iron oxide upon activation. Furthermore, the magnetic field was recorded to be 0.1 mT using a tesla meter. The magnetic properties present in the activated carbon show potential for pollutant removal. Adsorption studies of methylene blue using KBS show a maximum adsorption capacity of 59.27 mg/g; the adsorption process is rapid and reaches equilibrium after 9 h. Modelling using seven different isotherm and kinetic models reveals the best fit for the Langmuir-Freundlich and Diffusion-chemisorptionmodels, respectively. Additional thermodynamic calculations conclude the adsorption system to be exothermic, spontaneous, and favoring physisorption.

Enhanced Sorption Performance of Natural Zeolites Modified with pH-Fractionated Humic Acids for the Removal of Methylene Blue from Water

“…A similar behavior was found for the sorption of MB onto bentonite [69], peanut-shell-based activated carbon [70], and iron-oxide-modified montmorillonite [71]. In contrast, an exothermic sorption of MB was observed, for example, in the presence of bone char [72], citrate-modified pomelo peel [73], and a magnetic-gas-to-liquid-derived biosolid [74].…”

Application of Synthesized Biomass Bamboo Charcoal–Iron Oxide “BC/Fe” Nanocomposite Adsorbents in the Removal of Cationic Methylene Blue Dye Contaminants from Wastewater by Adsorption

“…This effect indicates that the adsorption reaction is exothermic in nature, and this may be due to an increase in the kinetic energy of dye molecules with the increase in solution temperature, which ultimately reduces the strength of interaction between adsorbate dye molecules and the active sites of adsorbent magnetic "BC/Fe" nanocomposite materials with the temperature rise [8]. Similar temperature effects on MB dye adsorption by nanomagnetic adsorbents were observed by various investigators [8,44].…”

Magnetically Sensitive Carbon-Based Nanocomposites for the Removal of Dyes and Heavy Metals from Wastewater: A Review

“…Many studies have shown that bio-carbon nanocomposites are effective in removing a wide range of dyes, but methylene blue is the most commonly used model dye. [104][105][106]…”