Cross-linked bionanocomposites of hydrolyzed guar gum/magnetic layered double hydroxide as an effective sorbent for methylene blue removal.

Guar gum (GG), a type of functional biomass, is one of the low-cost sources of galactomannan. To enhance its adsorption capacity, guar gum was chemically modified by Fe ₃ O ₄ /Ni-Al layered double hydroxide (LDH) and GG-LDH-Fe ₃ O ₄ (GLF) bionanocomposites were prepared. Then, cross-linked bionanocomposites (BNC-CLs) were synthesized using N, N'-methylene bis-acrylamide and applied to adsorb methylene blue (MB) from aqueous solutions. BNCs of GG with 4%, 6%, and 8% of magnetic LDH were prepared. These BNCs were identified by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), thermal gravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) spectroscopy, and Bruner-Emmett-Teller (BET) specific surface area techniques. The TGA results revealed that thermal properties of BNC-CLs improved by about 35 % and 47 % in comparison with pure polymer and GLF, respectively. Then, cross-linked and non-cross-linked BNCs were used to remove MB contaminants and the results revealed that cross-linked BNCs were able to remove 84 % of the MB. Adsorption studies were performed on the cross-linked BNC 8% and the effects of various characteristics such as pH, adsorbent dosage, contact time, and initial dye concentration were studied. The adsorption procedure was thoroughly contingent upon the pH value, with the optimal pH of 9 and equilibrium time of 120 min. Studying the isothermal models showed that the data were more consistent with the Langmuir linear isotherm.
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