Heterogeneous Fenton-type degradation of methylene blue dye in controlled pH condition catalyzed by copper(II) loaded waste chicken eggshell powder: a sustainable approach of utilization of naturally available biowaste materials

Wastewater generation being a pertinent problem necessitates the development of sustainable and efficient catalysts for treatment of water resources contaminated with dyes. In the present work, powdered eggshell (PES), an abundant biowaste material was used as an inert support material for the removal of copper(II), and thereafter the waste copper(II) loaded powdered eggshell, designated as Cu-PES was used as catalyst for Fenton-type degradation of methylene blue (MB) in water medium under controlled pH conditions. Cu-PES was characterized using scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, UV–visible diffuse reflectance spectroscopy, pH_ZPC and Brunauer–Emmett–Teller surface area analysis. The effects of different operational parameters such as initial concentration of dye, dose of catalyst, H₂O₂ concentration were studied. The decolorization efficiency obtained under controlled pH conditions with the as-prepared catalyst was ⁓97%. The catalytic activation of hydrogen peroxide generated hydroxyl radicals (∙OH), singlet oxygen (¹O₂) and carbonate radicals (CO₃^·−) which promoted the degradation and mineralization of MB. The degradation products were analyzed by MALDI-TOF. The turnover number (TON) and turnover frequency (TOF) were determined as 0.021 moles of MB per mole of copper and 3.55 × 10^–6 moles of MB /mole of Cu/s, respectively. The catalyst was recycled three times with MB degradation efficiency up to 65%.