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 Fe3O4/Ni-Al layered double hydroxide (LDH) and GG-LDH-Fe3O4 (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.

Green cross-linked bionanocomposite of magnetic layered double hydroxide/guar gum polymer as an efficient adsorbent of Cr(VI) from aqueous solution.

A novel bio-adsorbent based on guar gum (GG) was synthesized through the cross-linked polymerization of N,N'-methylene bis-acrylamide (MBA) onto Fe3O4@ nickel aluminum layered double hydroxide (Ni/Al LDH) @ GG bionanocomposite (BNC) using an in situ growth method. The structural, thermal, and morphological properties of the MLG BNC were studied by different techniques. According to field emission scanning electron microscopy, and transmission electron microscopy, there is a uniform distribution of nanoparticles with a particle size of 40-50 nm in the nanocomposite. MLG BNC was used as Cr (VI) adsorbent, and the effect of pH, concentration, and contact time on adsorption capacity was determined. It was observed that the maximum Cr(VI) adsorption by MLG was 101 mg g-1 (pH 6, 30 min). The adsorption isotherm was represented the single-layer, and homogeneous adsorption and the high value of R2 illustrates a good agreement with Langmuir. The adsorption kinetic was the second-order pseudo-model.

Ultra-fast and highly efficient removal of cadmium ions by magnetic layered double hydroxide/guargum bionanocomposites.

Finding effective methodologies for the removal of heavy metals from contaminated water are really significant. Facile and "green" techniques for adsorbents fabrication are in high demand to satisfy a wide range of practical applications. This report presents of an efficient method for preparing Fe3O4@ layered double hydroxide@ guargum bionanocomposites (GLF-BNCs). First of all, the LDH coated Fe3O4 nanoparticles were simply synthesized, using ultrasonic irradiation. The citrate coated Fe3O4 nanoparticles which were under negative charging and LDH nanocrystals which were charged positively make electrostatic interaction which formed a stable self-assembly component, and then guargum as a biopolymer were linked onto Fe3O4@LDH via an in situ growth method. Furthermore, the GLF-BNCs had the ability to remove cadmium ions (Cd2+) from the aqueous solutions. Adsorption studies indicate that the Langmuir isotherm model and the kinetic model in pseudo-second order were appropriate for Cd(II) removal. The maximum Cd(II) adsorption capacity of the GLF8% was 258 mg g-1. The Cd(II) was adsorbed from aqueous solutions very quickly with the contact time of 5 min by the GLF 8%, suggesting that GLF-BNCs may be a promising adsorbent for removing Cd(II) from wastewater. The effect of Fe3O4@LDH contents (2, 4 and 8 wt.%) on the thermal, physicomechanical, and morphological properties of guargum were investigated by Fourier transform infrared spectroscopy, X-ray diffraction (XRD), thermal gravimetric analysis (TGA), field emission scanning electron microscopy, transmission electron microscopy (TEM), Energy-dispersive X-ray spectroscopy and Brunauer-Emmett-Teller (BET) specific surface area techniques. The TEM results indicated that the LDH platelets are distributed within the polymer matrix.