Pyrolysis Biochar from Cellulosic Municipal Solid Waste as Adsorbent for Azo Dye Removal: Equilibrium Isotherms and Kinetics Analysis

Abstract

Municipal solid waste (MSW) can have a negative impact on the environment and / or human health, if not properly managed. Though landfill is the most common method used to manage MSW, treating MSW using waste-to-energy (WtE) technologies is an option that is receiving increasing interest. Pyrolysis is a WtE technology that is capable of converting waste into products such as bio-gas, bio-oil and bio-char. Bio-char, which varies in composition based on the raw material pyrolysed, has the potential to be used as a fuel and as an applied material for catalysis or adsorption. In this work the removal of azo dye was investigated using bio-char from pyrolysis of a cellulosic municipal solid waste. The bio-char was characterised using Scanning Electron Microscopy and Surface Area Analysis. The influence of pH on the dye removal was investigated over the range 4-7. The experimental data was analysed using four non-linear kinetic models (Pseudo first-order, pseudo second-order, Weber intra-particle diffusion and Elovich equation) and four non-linear isotherm models (Langmuir, Freundlich, Temkin and Sips), and ranked based on the statistical analysis tools in origin software. The dye removal kinetics most closely followed pseudo-first order kinetics whilst the adsorption isotherms were most closely fitted by the Temkin model over the pH range studied.