Scalable Synthesis of Collagenic-Waste and NaturalRubber-Based Biocomposite for Removal of Hg(II) and Dyes: Approachfor Cost-Friendly Waste Management

摘要

For initiating a prosperous cost-friendly waste management of small-scale industries, cow buffing dust (CBD), one of the abundantly available semisynthetic collagenic solid wastes, has been used as a nonsulfur cross-linker of natural rubber (NR) for fabricating an NRCBD–biocomposite superadsorbent. The as-prepared reusable biocomposite bearing variegated collagenic and noncollagenic N-donors, along with the O-donors, has been reported for ligand-selective preferential superadsorption from waste water. Thus, a CBD and NR-based scalable biocomposite bearing optimum cross-linking, excellent physicochemical properties, and reusability has been developed via systematic optimization of the torque and reaction time for cost-friendly adsorptive exclusion of dyes, such as 2,8-dimethyl-3,7-diamino-phenazine (i.e., safranine, SF) and (7-amino-8-phenoxazin-3-ylidene)-diethylazanium dichlorozinc dichloride (i.e., brilliant cresyl blue), BCB, and Hg(II). The CBD-aided curing of NR has been achieved through the formation of a cross-linked chromane-ring originated via reaction between the methylol-phenol ring of phenol-formaldehyde resin and isoprene unitof NR. The partial disappearance of unsaturation in cured-NRCBD, relativevariation of crystallinity, surface properties, elevated thermal stabilities,and ligand-selective superadsorption have been studied by advancedmicrostructural analyses of unadsorbed and/or adsorbed NRCBD usingFourier transform infrared (FTIR), ¹³C nuclear magneticresonance, ultraviolet–visible, and O 1s-/N 1s-/C 1s-/Hg 4f7/2,5/2-X-ray photoelectron spectroscopies, thermogravimetricanalysis, differential scanning calorimetry, X-ray diffraction, fieldemission scanning electron microscopy, energy-dispersive spectroscopy,and pHPZC. Response surface methodology-based optimizationhas been employed to attain the optimum potential of NRCBD, consideringthe interactive effects between pHi, temperature, and concentrationof the dye. H-aggregate and time-dependent hypochromic effect hasbeen observed during individual adsorption of dyes. Moreover, theprevalence of chemisorption via ionic interaction between NRCBD andSF, BCB, and Hg(II) has been realized by FTIR, fitting of kineticsdata to the pseudosecond-order model, and measurement of activationenergies. The Brunauer–Emmett–Teller and Langmuir isothermsfit the best to BCB and SF/Hg(II), respectively. Thermodynamicallyspontaneous chemisorption have shown the maximum adsorption capacitiesof 303.61, 46.14, and 166.46 mg g^–1 for SF, BCB,and Hg(II), respectively, at low initial concentration of Hg(II)/dyes= 40 ppm, 303 K, and adsorbent dose = 0.01 g.