Kinetics and equilibrium adsorption of methylene blue onto cotton gin trash bioadsorbents

Cotton gin trash (CGT), a residual lignocellulosic biomass generated during the ginning process of cotton fibres, is proposed for valorization and application in environmental remediation. Taking advantage of its availability and composition, rich in hydroxyl, carboxyl, and carbonyl groups, CGT is studied for its suitability for dye removal. Cotton gin trash films are synthesized using a single-step process with formic acid and tested for methylene blue (MB) adsorption. The morphology, chemical structure, surface area, zeta potential and crystallinity of the films are also reported. The hydroxyl groups in CGT increased by the film preparation and further enhanced the zeta potential of CGT towards the negative direction. Overall, the adsorption process is governed by the physisorption characteristic, where a greater potential difference between CGT and cationic MB improved the dye uptake. The adsorption system is described as favourable, fitting better with Langmuir isotherm model. The maximum adsorption capacity of the CGT films is 209 mg/g, which compares favourably against other reported lignocellulosic materials. Overall, the results indicate the CGT has an enormous potential as an adsorbent material for dye separation from wastewaters.