Barium Ferrite Based Magnetic Adsorbents for Methyl Blue Dye Removal from Aqueous Solution

Abstract

Using sophisticated adsorbent materials to clean harmful dye-contaminated water is rapidly gaining popularity. Among different adsorbents, magnetic ferrites-based adsorbents are gaining much attention because of their easy recyclability. BaFe12O19 (BaM) has applications such as adsorbent and catalyst. In this research work, BaM powder, BaM-chitosan composite, and BaM-chitosan-activated charcoal composites were prepared for methyl blue (MB) dye removal application. BaM powder was synthesized through sol-gel combustion, activated charcoal-modified sol-gel combustion and coprecipitation routes. Pure phase BaM was formed after calcination of precursor powder at 1000 ºC in sol-gel (SG-BaM) and activated charcoal modified sol-gel (SG- BaM-C) combustion route, 900 ºC in coprecipitation route (CP-BaM-900), respectively. To increase the magnetic properties of BaM, the coprecipitated precursor was also calcined at 1000 oC (CP-BaM-1000). X-ray diffraction (XRD) was utilised to analyse phases. Fourier transform infrared spectroscopy (FTIR), Brunauer, Emmett, and Teller (BET) surface area analysis, vibrating sample magnetometer (VSM), and field emission scanning electron microscope (FESEM) were also used for the characterization. The surface area of SG-BaM-C powder determined by BET was 5.93 m2 g-1. The SG- BaM-C adsorbent has a saturation magnetization (Ms) of 56.8 emu g-1 and a coercivity (Hc) of 5176 Oe. The effects of pH, adsorbent dose, adsorption period, MB dye concentration, and temperature on MB dye adsorption were studied. It was found that Pseudo-second-order kinetics and the Sips isotherm model govern the adsorption process of MB by SG-BaM-C. The MB adsorption capacity of SG-BaM-C was 150.2 mg g-1 at a solution pH of 6.0 and temperature of 303 K. For CP-BaM-900 powder Ms of 67.7 emu g-1 and Hc of 5106 Oe was observed. CP-BaM- 900 ferrite particles with a surface area of 8.2 m2 g-1 was used for the adsorption and sunlight-induced photodegradation of MB dye. The CP-BaM-900 ferrite's optical band gap was 2.9 eV. The adsorption procedure tracked the pseudo-second-order model and satisfied the Langmuir adsorption isotherm. CP-BaM-900 particles showed the maximum Langmuir saturation adsorption ability of 223.86 mg g-1 at an initial MB solution pH of 5.7 and 303 K temperature. The free energy and enthalpy variations of the adsorption confirmed the spontaneous and exothermic process. For photocatalytic degradation using CP-BaM-900, about 73 % of degradation of MB was found within 3 h of sunlight-induced photocatalytic degradation. Reproduced BaM powder showed little loss in degradation efficiency after five cycles. Glutaraldehyde cross-linked BaM-chitosan composite beads (BaM-CS), were prepared in this work with 1000 oC calcined coprecipitation synthesised BaM powder (CP-BaM-1000). For BaM-CS beads, Ms of 52.2 emu g-1 was observed. The BET surface area of BaM-CS beads was 2.237 m2 g-1. Maximum MB adsorption capacity of BaM-CS adsorbent was observed at pH 6.0. To know the chemo-physical features of the adsorption route, the system's kinetics and isotherm behaviour were studied in detail. It was established that the temperature had a substantial impact on the adsorption process. The adsorption was found to be best characterized by the sips isotherm model and followed pseudo-second-order kinetics. Adsorption of MB through BaM-CS was an endothermic and non-spontaneous process. Maximum MB adsorption capacity of BaM-CS was 123.9 mg g-1 at pH of 6.0 and 323 K. The BaFe12O19-chitosan-activated charcoal composite powder (BaM-CS-AC-P) and beads (BAM-CS-AC-B) were made from CP-BaM-1000 powder. BAM-CS-AC-B composite bead had Ms of 25.83 emu g-1 and Hc of 2606 Oe, whereas BaM-CS-AC-P composite powder showed an Ms of 26.8 emu g−1, which was adequate for efficient magnetic separation of these adsorbents in water suspension. BAM-CS-AC-B composite bead with a BET surface area of 152.9 m2 g-1 and BaM-CS-AC-P composite powder with a surface area of 41.5 m2 g−1 were used for MB adsorption studies. The composite powder showed a maximum Sips adsorption ability of 254.6 mg g−1 at an MB solution pH of 6 and 323 K temperature. BAM-CS-AC-B beads showed a maximum Sips adsorption capacity of 371.6 mg g-1 at similar conditions. For both adsorbents, adsorption was spontaneous and endothermic. Both composites showed good adsorption capacity in five consecutive regeneration cycles.