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 the 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. To characterize the nanocomposite, we used SEM, FT-IR, XRD, and BET techniques. 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 initial dye concentration, pH, contact time, adsorbent dose, and temperature on Chrysoidine-G adsorption was explored. The adsorbent showed a high removal (>93%) for a wide concentration range of Chrysoidine-G, also acidic pH and higher temperature are more favorable for the process. Equilibrium adsorption parameters were reasonably fitted with a linear (Nernst) isotherm model. The results indicated the existence of an unlimited number of absorption sites, i.e. no saturation was achieved under our experimental conditions (qmax(Exp)= 731 mg/g). Kinetic data were fitted with pseudo-second-order and intra-particle diffusion models. We conclude that this nanocomposite is a green adsorbent with potential use for wastewater treatment and related purposes. HighlightsO_LIWe produced an easy-separable bio-nanocomposite using whey nanofibrils and MMT, with high adsorption capacity C_LIO_LINanofibrils help disperse MMT particles uniformly in the WP matrix C_LIO_LIThe adsorbents performance was compared to the adsorbents in absence of MMT and nanofibrils C_LIO_LIThis composite adsorbs cationic, anionic, direct and reactive azo dyes with different kinetics C_LIO_LIAdsorption isotherms and kinetics are studied in detail C_LI O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=82 SRC="FIGDIR/small/394205v3_ufig1.gif" ALT="Figure 1"> View larger version (43K): org.highwire.dtl.DTLVardef@13aa68eorg.highwire.dtl.DTLVardef@18cc8c0org.highwire.dtl.DTLVardef@1cff49eorg.highwire.dtl.DTLVardef@1c4de1c_HPS_FORMAT_FIGEXP M_FIG C_FIG