Magnetic Fe3O4 nanoparticles loaded guava leaves powder impregnated into calcium alginate hydrogel beads (Fe3O4-GLP@CAB) for efficient removal of methylene blue dye from aqueous environment: Synthesis, characterization, and its adsorption performance

In the present work, a novel Fe3O4-GLP@CAB was successfully synthesized via a co-precipitation procedure and applied for the removal of methylene blue (MB) from aqueous environment. The structural and physicochemical characteristics of the as-prepared materials were explored using a variety of characterization methods, including pHPZC, XRD, VSM, FE-SEM/EDX, BJH/BET, and FTIR. The effects of several experimental factors on the uptake of MB using Fe3O4-GLP@CAB were examined through batch experiments. The highest MB dye removal efficiency of Fe3O4-GLP@CAB was obtained to be 95.2 % at pH 10.0. Adsorption equilibrium isotherm data at different temperatures showed an excellent agreement with the Langmuir model. The adsorption uptake of MB onto Fe3O4-GLP@CAB was determined as 136.7 mg/g at 298 K. The kinetic data were well-fitted by the pseudo-first-order model, indicating that physisorption mainly controlled it. Several thermodynamic variables derived from adsorption data, like as ΔGo, ΔSo, ΔHo, and Ea, accounted for a favourable, spontaneous, exothermic, and physisorption process. Without seeing a substantial decline in adsorptive performance, the Fe3O4-GLP@CAB was employed for five regeneration cycles. Because they can be readily separated from wastewater after treatment, the synthesized Fe3O4-GLP@CAB was thus regarded as a highly recyclable and effective adsorbent for MB dye.

Magnetic chitosan/calcium alginate double-network hydrogel beads: Preparation, adsorption of anionic and cationic surfactants, and reuse in the removal of methylene blue

Robust and reusable magnetic chitosan/calcium alginate double-network hydrogel beads (CSMAB) with an environmentally benign biocomposite material synthesis approach were used adsorption of surfactant and removal of methylene blue dye sequentially for the first time. Double network hydrogel structure with sodium alginate and chitosan and acidification of the surface with HCl provided the reusability of the beads at the pollutant removal in water. The CSMAB beads were characterized for structural analysis by FESEM, EDX, BET, VSM, and FTIR techniques. They were used for the adsorption of cationic hexadecylpyridinium chloride (HDPCl) and anionic sodium dodecyl sulfate (SDS) surfactants and reused in the removal of cationic methylene blue dye without any pretreatment. The effect of pH, adsorbent dose, and temperature on surfactant removal efficiency was analyzed and pH was found the statistical significance. The adsorption capacity of CSMAB beads with a surface area of 0.65 m² g^-1 was calculated as 1.9 mg g^-1 for HDPCl, and 1.2 mg g^-1 for SDS, respectively. The SDS and HDPCl adsorption followed the pseudo-second-order kinetic and Freundlich isotherm model. The thermodynamic results showed that the surfactant adsorption process is an exothermic and spontaneous process. SDS-reacted CSMAB beads showed higher efficiency with 61 % in the removal of methylene blue dye.

Facile synthesis of copper ferrocyanide-embedded magnetic hydrogel beads for the enhanced removal of cesium from water

A simple one-step approach for fabricating copper ferrocyanide-embedded magnetic hydrogel beads (CuFC-MHBs) was designed, and the beads were applied to the effective removal of cesium (Cs) and then magnetically separated from water. The polyvinyl alcohol (PVA)-coated CuFC (PVA-CuFC) was first synthesized using PVA as a stabilizer and subsequently embedded in magnetic hydrogel beads made of a cross-linked network between the PVA and magnetic iron oxide nanoparticles that was prepared through the simple dropwise addition of a mixed solution of PVA-CuFC, PVA and iron salt into an ammonium hydroxide solution. The synthesis and chemical immobilization of the PVA-CuFC in the magnetic beads were simple, facile and achieved in one pot, and the process is scalable and convenient for the large-scale treatment of Cs-contaminated water. The resulting CuFC-MHBs showed effective Cs removal performance with a high K_d value of 66,780 mL/g and excellent structural stability without the release of CuFC for at least 1 month and could be effectively separated from water by an external magnet. Moreover, the CuFC-MHBs selectively adsorbed Cs with high K_d values in the presence of various competing ions, such as in simulated groundwater (24,500 mL/g) and seawater (8290 mL/g), and maintained their Cs absorption ability in a wide pH range from 3 to 11. The convenient fabrication method and effective removal of Cs from various aqueous media demonstrated that the CuFC-MHBs have great potential for practical application in the decontamination of Cs-contaminated water sources caused by nuclear accidents and radioactive liquid waste in various nuclear industry fields.