Adsorption of Methylene blue and Methyl orange on nano zero-valent iron (nZVI) coated biochar: column adsorption experiments

Despite its attractiveness and combinatorial effectiveness, the biochar supported nanoscale zero-valent iron particles (nZVI) composite has not been applied in a multi-dye system and fixed bed column experiments.The present work aimed at preparing a corn cob biochar coated with nZVI particles to obtain an efficient low-cost adsorbent and investigate its potential to remove two synthetic dyes Methylene blue (MB) and Methyl orange (MO) from their single and mixture using column experiments.Brunauer-Emmett-Teller surface analyzer, scanning electron microscopy-energy-dispersive X-ray analysis, X-ray diffraction, Zetasizer Nano ZS90 and Fourier-transform infrared spectroscopy have been used to investigated the physico-chemical properties of the prepared adsorbent and explore the dynamics of competition, selectivity and adsorption mechanisms involved in dyes removal from their mixture.The MB antagonistic action vis-à-vis MO removal was high in column binary dye adsorption experiments.Experimental data of MB removal were fitted to non-linear Thomas and Yoon-Nelson models, the former fitting the best with R 2 = 0.9886.The dynamic absorption capacity (q b ) was 15 mg/g, the column removal efficiency 89.64% and the highest adsorption capacity 118.056 mg/g.Dyes' adsorption mechanism involved mainly electrostatic attractions, adsorbent surface sorption and pore diffusion.The complexity of the breakthrough curve of MO and non-attainment of the bed column exhaustion time suggest further detailed research studies.