Production of activated carbons from waste tyres and bamboo scaffolding for the removal of pollutants from effluents

Abstract

The aim of this study is to prepare a range of activated carbons with specific textural properties from two solid waste materials, namely, waste tyres and waste bamboo construction scaffolding. A range of experimental parameters have been varied and studied to see how each parameter influences the textural properties of the activated carbons. The waste tyre and bamboo were first converted into chars by thermal treatment. Theromgravimetric analyses have been performed and analysed using multi-stage kinetic decomposition models. For the pyrolysis of waste tyre a five-step model gave the best correlation to experimental data and a six-step model gave the best correlation for bamboo pyrolysis. Compensation effect was observed in the pyrolysis of both materials. Tyre carbons (with or without acid treatment) were produced via carbon dioxide activation with BET surface areas in the range 59 to 1118 m2/g. Bamboo-derived carbons by thermal activation in the presence of hydrochloric, nitric and sulphuric acids have lower BET surface area from 183 to 554 m2/g. Other characteristion tests include micropore and mesopore surface areas and volumes, pH, and elemental compositions, particularly heteroatoms such as nitrogen and sulphur. They were correlated to the adsorption capacity which were in the range 0.399 to 0.914 mmol/g (tyre) and to 0.022 to 0.088 mmol/g (bamboo) for acid dyes. For basic dye like Methylene Blue, capacities were in the range 1.034 to 1.428 mmol/g (tyre) and 0.351 to 0.649 mmol/g (bamboo). Based on the surface coverage analysis, novel molecular orientation modelling of adsorbed dyes has been proposed and correlated with surface area and surface charge. For acid dyes, molecules were likely to be adsorbed over mesopore areas. For basic dye micropore area was critical. While modelling the dye adsorption equilibrium data, the Redlich-Peterson isotherm is preferred