A novel synthesis of MIL-53(Al)@SiO2: an integrated photocatalyst adsorbent to remove bisphenol a from wastewater

Abstract

An integrated methodology has been formulated for treating the bisphenol A-containing effluents that include its adsorption using a newly synthesized MIL-53(Al)@SiO₂, followed by the photocatalytic degradation. PL spectroscopy studies proved that the introduction of SiO₂ in the conventional form of MIL-53(Al) resists hole and electron recombination. The novel metal organic framework (MOF) composite was synthesized using coal fly ash and waste aluminium foil through the solvothermal method. The fabricated composite was characterized to ensure the improved physical and chemical properties, as compared to that of raw fly ash, including: (i) a large increase in the surface area from 2 m² g⁻¹ to 667.802 m² g⁻¹, (ii) the enhancement in the pore volume from 0.00518 cc g⁻¹ to 0.466 cc g⁻¹, (iii) the conversion of the pore structure from an ink bottle structure to a slit-type structure, (iv) the change in crystallinity, (v) the addition of –CO and C–H stretching on the surface, and (vi) the change in topology from spherical to a nano-rod structure. The synthesized MIL-53(Al)@SiO₂ shows a monolayer adsorption process influenced by both physical and chemical adsorption. The maximum adsorption capacity was obtained to be 134.68 mg g⁻¹, which is several folds greater than that of raw fly ash. On the other hand, the photocatalysis degrades a maximum of 85.04% of bisphenol A, satisfying the first order reaction kinetics model. With the excellent performance of the synthesized material in removing the respective pollutant, this is proposed as a potential adsorbent-cum-photocatalyst for the treatment of wastewater effluents.