Green one-spot synthesis of hydrochar supported zero-valent iron for heterogeneous Fenton-like discoloration of dyes at neutral pH

Heterogeneous Fenton-like process is highly effective for treatment of dye wastewater, but it is notably limited by developing cheap, efficient and eco-friendly catalysts. Green one-pot synthesis of hydorchar supported zero-valent iron (HCZVI) was conducted using tea leaves as biomass feedstocks. The properties of HCZVI are characterized by Fourier transform infrared spectra, Raman spectra, X-ray diffraction analysis, scanning electron microscopy and electron probe microanalyzer. Micro and nano ZVI particles are well distributed on hydrochar surface. Fenton-like discoloration of methylene blue (MB) depends on HCZVI dosage, H2O2, pH. MB concentration and temperature. Effective MB discoloration can be obtained under broad pH region. MB removal reaches 97.77% within 60 min under conditions of 0.4 g/L HCZVI, 99.70 mM H2O2, pH 6.4 and 10 mg/L MB. Kinetic analysis of Fenton-like MB discoloration was conducted using the first-order kinetic model, and the calculated activation energy is 74 kJ/mol. MB discoloration dominated by chromophore groups cleavage is attributed to attack of hydroxyl radical generated from HCZVI activation of H2O2. The catalytic system is also effective for discoloration of rhodamine B and add orange 7. HCZVI is a promising catalyst for Fenton-like discoloration of dye wastewater due to facile fabrication, low cost, and environmental friendliness. (C) 2020 Elsevier B.V. All rights reserved.