Green Hydrogel-Biochar Composite for Enhanced Adsorption of Uranium

Abstract

Uranium is the backbone of the nuclear fuel used for energy production but is still a hazardous environmental contaminant; thus, its removal and recovery are important for energy security and environmental protection. So far, the development of biocompatible, efficient, economical, and reusable adsorbents for uranium is still a challenge. In this work, a new orange peel biochar-based hydrogel composite was prepared by graft polymerization using guar gum and acrylamide. The composite’s structural, morphological, and thermal characteristics were investigated via Fourier transform infrared (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) methods. The composite’s water absorption properties were investigated in different media. The performance of the prepared composite in adsorbing uranium (VI) ions from aqueous media was systematically investigated under varying conditions including solution’s acidity and temperature, composite dose, contact time, and starting amount of uranium. The adsorption efficiency increased with solution pH from 2 to 5.5 and composite dose from 15 to 50 mg. The adsorption kinetics, isotherms, and thermodynamics parameters were analyzed to get insights into the process’s feasibility and viability. The equilibrium data were better described through a pseudo-second-order mechanism and a Langmuir isotherm model, indicating a homogeneous composite surface with the maximum uranium (VI) adsorption capacity of 263.2 mg/g. The calculated thermodynamic parameters suggested that a spontaneous and endothermic process prevailed. Interference studies showed high selectivity toward uranium (VI) against other competing cations. Desorption and recyclability studies indicated the good recycling performance of the prepared composite. The adsorption mechanism was discussed in view of the kinetics and thermodynamics data. Based on the results, the prepared hydrogel composite can be applied as a promising, cost-effective, eco-friendly, and efficient material for uranium (VI) decontamination.

Catalytic Activity and Reusability of Nickel-Based Catalysts with Different Biochar Supports during Copyrolysis of Biomass and Plastic

“…The subsequent decrease in crystallite size may be caused by pore collapse (Table ), which led to exposure of small-size Ni crystals in biochar pores. The FTIR pattern of reused catalysts (Figure b) shows that the peak strength at 3200–3700 cm –1 (stretching vibration of −OH), 1350–1430 cm –1 (bending vibration of C–H and stretching vibration of C–N), and 1558–1629 cm –1 (stretching vibration of CC and CO) first increased and then decreased in the reused process . The peak intensity was higher in Ni/ZC-S2 and Ni/ZC-S3 groups while decreased in Ni/ZC-S4.…”

“…The FTIR pattern of reused catalysts (Figure 2b) shows that the peak strength at 3200−3700 cm −1 (stretching vibration of −OH), 1350−1430 cm −1 (bending vibration of C−H and stretching vibration of C−N), and 1558−1629 cm −1 (stretching vibration of C�C and C�O) first increased and then decreased in the reused process. 28 The peak intensity was higher in Ni/ZC-S2 and Ni/ ZC-S3 groups while decreased in Ni/ZC-S4. During catalytic pyrolysis, more functional groups were formed on the surface of the catalyst.…”

“…Figure 1b shows that the broad peak at 3200−3700 cm −1 was caused by the stretching vibration of OH-or adsorbed water. 28 The peak of 1558−1629 cm −1 was attributed to stretching vibration of C�C and C�O, and the 1350−1430 cm −1 peak was assigned to C−N stretching vibration and C−H bending vibration. 28 In addition, the Ni−O−H stretching vibration peak appears at 580 cm −1 .…”

“…28 The peak of 1558−1629 cm −1 was attributed to stretching vibration of C�C and C�O, and the 1350−1430 cm −1 peak was assigned to C−N stretching vibration and C−H bending vibration. 28 In addition, the Ni−O−H stretching vibration peak appears at 580 cm −1 . 29 There were abundant Ocontaining functional groups on various carbon supports, which provided active sites for catalytic pyrolysis to promote the reaction process.…”

Hydrogel‐biochar composites for removal of methylene blue: Adsorption performance, characterization, and adsorption isotherm, kinetics, thermodynamics analysis

“…Poor gel strength and weak stability also restrict effective adsorption and regeneration. Biochar composite hydrogel has become a new direction for researching three‐dimensional cross‐linked materials 30–32 . The combination of biochar and hydrogel can effectively compensate for their respective defects and form complementary advantages.…”