Adsorption of Azo Dyes by a Novel Bio-Nanocomposite Based on Whey Protein Nanofibrils and Nano-clay: Equilibrium Isotherm and Kinetic Modeling

Excessive discharge of hazardous azo dyes into aquatic ecosystem is a global environmental concern. Here, we develop a green approach to remediate dye pollutions in water by fabricating an easy separable bio-nanocomposite, based on whey protein concentrate, its nanofibrils and montmorillonite nano-clay. Nanofibrils lead to a uniform dispersion of montmorillonite in the whey protein matrix and also reinforce the nanocomposite. The adsorption efficacy was monitored in a batch system, using cationic dyes (Chrysoidine-G, Bismarck brown-R), reactive dyes (reactive black-5, reactive orange-16), acid dyes (acid red-88, acid red-114), and direct dyes (direct violet-51, Congo red). This nanocomposite adsorbed different dye classes, cationic dyes quicker (>82%, after 4 h) and reactive dyes slower. Then, the effect of dye concentration, contact time and adsorbent dose on Chrysoidine-G adsorption was explored. The adsorbent showed a high removal (>93%) for a wide concentration range of Chrysoidine-G. Equilibrium adsorption parameters were reasonably fitted with a linear (Nernst) isotherm model, while kinetic data were fitted with pseudo-second-order and intra-particle diffusion models. To characterize the nanocomposite, we used SEM, FT-IR, XRD and BET techniques. We conclude that this nanocomposite is a green adsorbent with potential use for wastewater treatment and related purposes.HighlightsWe produced a novel bio-nanocomposite using whey nanofibrils and MMTNanofibrils help disperse MMT particles uniformly in the WP matrixThe adsorbent’s performance was compared to the adsorbents in absence of MMT and nanofibrilsThis composite adsorbs cationic, anionic, direct and reactive azo dyes with different kineticsAdsorption isotherms and kinetics are studied in detailAbstract Figure