Triastuti Sulistyaningsih, - (2024) Green synthesis of gaharu leaf extract-modified magnetite as an adsorbent for methyl orange textile dyes. Waste Management Bulletin.

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Abstract

Magnetite, a widely synthesized compound utilized as an adsorbent in various processes, exhibits reduced adsorption efficiency due to aggregation in aqueous solutions. Addressing this limitation, modification of magnetite is necessary to mitigate agglomeration and enhance adsorption capacity. Herein, we propose the utilization of gaharu leaf extract for magnetite modification, leveraging its abundance as a byproduct of essential oil production and rich secondary metabolite content, which serves as a stabilizing agent in synthesis processes. Magnetite (M) and gaharu leaf extract-modified magnetite (MEDG) were synthesized and evaluated as adsor�bents for methyl orange (MO) textile dyes. Characterization via FTIR, PSA, SEM-EDX, XRD, and VSM revealed distinctive features of MEDG, including vibrational peaks corresponding to organic functional groups derived from the secondary metabolites present in the gaharu leaf extract. These functional groups actively participate in the adsorption process and prevent magnetite aggregation. MEDG exhibited a particle size of 4408.7 nm, compared to 4625 nm for M, with both exhibiting face-centered cubic (fcc) crystal structures. Additionally, MEDG demonstrated a crystallinity percentage of 92.49 % and saturation magnetization of 34.43 emu/g, attributed to the incorporation of gaharu leaf extract. Adsorption studies demonstrated that MEDG and gaharu leaf simplicia (SDG) achieved maximal adsorption of MO at pH 3 for 60 min and pH 4 for 70 min, respectively, with an adsorption efficiency of 95–99 % for a 5 ppm MO solution. The adsorption kinetics followed Ho’s pseudo-second-order model, and the isotherm conformed to Freundlich’s model. Furthermore, M and MEDG exhibited high reusability, with up to 5 cycles of reuse, while SDG demonstrated 3 cycles. However, the adsorption efficiency decreased to 87 % for MEDG and 85.19 % for SDG upon the fifth repetition. In conclusion, modification of magnetite with gaharu leaf extract enhances its adsorption capacity, offering economic advan�tages over pure magnetite due to increased surface area and active sites.

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