Recyclable biopolymer encapsulated orange peel biochar embedded iron–organic framework composite for selective uptake of methylene blue†

This study focuses on the novel fabrication of a composite of orange peel biochar (OPB) and Fe-metal organic frameworks (FOFs) embedded with chitosan/pectin biopolymer (OPBCPFOF) for effective methylene blue (MB) removal. The prepared OPBCPFOF composite was characterized using EDAX, FTIR, XRD and SEM techniques. The effect of several variables, including solution pH, initial MB concentration, shaking period, adsorbent dosage, co-existing ions and temperature, was investigated in batch experiments to determine the maximum adsorption capacity. The isotherm experimental data revealed that the Langmuir model was the ideal model for adsorption studies. The results of kinetic studies confirmed that the adsorption process followed the intra-particle diffusion and pseudo-second-order models. Adsorption was determined to be endothermic and feasible based on the results of thermodynamic studies. The superior MB adsorption on the OPBCPFOF composite was primarily driven by strong hydrogen bonding, electrostatic interaction and π–π interaction. The reusable properties of the OPBCPFOF composite were tested up to six cycles. The results present the OPBCPFOF composite as an appropriate adsorbent for the MB removal process.