Novel Composite Adsorbent Consisting of Dissolved Cellulose Fiber/Microfibrillated Cellulose for Dye Removal from Aqueous Solution

A novel composite absorbent was developed based on dissolved cellulose fibers (as matrix) reinforced with microfibrillated cellulose (MFC). Both cellulose fibers and microfibrillated cellulose were functionally modified using an organic solvent-free approach to introduce carboxyl groups onto cellulose and the surface of MFC. To further enhance the adsorption capacity, nanosized CaCO3 was added as a pore forming agent during the formation of dissolved cellulose/MFC (CMFC) composites and removed in acidic conditions afterward. The structure and morphology of as-synthesized adsorbents were identified using a scanning electron microscope, Fourier transform infrared spectroscope, thermogravimetric analyzer, and Brunauer–Emmet–Teller instrument. An orthogonal experimental design and software SPSS were utilized to reveal the impact of influencing factors (pH, temperature, and the concentration of pore forming agent) on dye removal. The results were imitated by kinetic models and adsorption isotherms, which revealed that the carbonylated CMFCs had a maximum adsorption capacity of Methylene Blue of 303 mg g–1. The results of pseudo-second-order kinetic and the Langmuir isotherm modeling indicated that the adsorption was monolayer and governed by chemisorption.