Orange waste: A valuable carbohydrate source for the development of beads with enhanced adsorption properties for cationic dyes.

Eco-friendly pectin and pectin/cellulose microfibers beads (PB and PB-CF) were synthesized using compounds extracted from orange bagasse, a solid waste from the food industry. PB-CF beads showed remarkable differences regarding several properties as compared to the beads without CF. The adsorption capability of PB and PB-CF was tested towards the removal of methylene blue (MB) from aqueous solution. The effect of various parameters on the MB adsorption was investigated. The kinetics and mechanism of adsorption were explained by the pseudo-second-order kinetics and intra-particle diffusion models. Equilibrium adsorption data are explained by the Langmuir isotherm model, which revealed a maximum adsorption capacity of 1550.3mg/g for PB and 2307.9mg/g for PB-CF5. Thermodynamic analysis suggests that the adsorption of MB on the beads is spontaneous and favorable. Recycling study demonstrated that both PB and PB-CF5 can be implemented in 6 consecutive adsorption/desorption cycles without losing their adsorption capacity. These results enable the use of PB and PB-CF as potentially low-cost adsorbents for wastewater treatments.