CD Disertasi

Sintesis Mangan Oksida Untuk Aplikasi Degradasi Zat Warna Methylene Blue =Synthesis Of Manganese Oxide For Degradation Of Methylene Blue Dyes

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Water pollution has a negative impact on quality of life, health, and the environment. One of the major sources of water pollution is synthetic dyes that are not properly treated. The textile industry contributes more than 55% of global dye wastewater. It uses over 80,000 metric tons of reactive dyes annually, and this number continues to rise. One of the hazardous dyes that is difficult to degrade naturally is methylene blue (MB). Therefore, effective solutions are needed to address this large-scale pollution issue, one of which is the use of manganese oxide catalysts. Manganese oxide (MnxOy) is a type of smart material that is currently being extensively developed due to its wide range of applications in energy, smart devices, catalysis, and environmental fields. The synthesis methods used in this research are precipitation, solvothermal, and microwave-solvothermal, chosen for their eco-friendly nature and minimal mass loss. The synthesized manganese oxide materials were characterized using X-ray Diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), N2-Physisorption Gas Sorption Analyzer (BET surface area), Particle Size Analyzer (PSA), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), and Raman Spectroscopy. The effectiveness of catalysis for the degradation of liquid waste was carried out by MB degradation test and the degradation reaction mechanism was estimated by Liquid Chromatography-Mass Spectrometry (LCMS) using a time-of-flight mass analyzer (TOF MS) with Electrospray Ionization (ES+). The results indicate that precipitation, solvothermal, and microwave-solvothermal methods can be used to synthesize smart manganese oxide materials. XRD analysis of MnO2 synthesized via precipitation showed that different types of precursors tend to produce different MnO2 structures. XRD patterns of solvothermal-synthesized MnO2 using ethanol as a solvent showed that heating time and temperature are more influential on the resulting MnO2 phase than pH adjustments using HCl and NaOH. However, pH regulation influences the crystallinity level; acidic conditions tend to produce more crystalline materials. FT-IR spectra of all synthesized MnO2 samples displayed Mn–O and Mn–O–Mn vibration peaks, which are characteristic bands of manganese oxides. Variations in synthesis methods and conditions affected the resulting particle sizes. PSA data showed that several types of synthesized MnO2 formed one, two, or three particle size clusters. Specifically, samples A-2, A-11, A-12, and B-13 exhibited one cluster; A-3, A-8, A-9, A-10, A-13, A-14, B-6, B-10, and B-11 showed two clusters; and A-15, B-2 exhibited three clusters. The smallest average particle size was 154.5 nm (A-11), while the largest was 1389.9 nm (A-15). The N2 adsorption-desorption isotherm profiles of all samples were Type IV, indicating strong interactions between the adsorbents and nitrogen gas (adsorbate), with mesopore sizes (2 nm < mesopores < 50 nm) and H3 hysteresis loop in the P/Po range of 0.7–1.0. The highest specific surface areas were found in samples A-8, A-2, B-11, and B-6, measuring 23.624, 26.260, 26.447, and 27.888 m²/g, respectively.

SEM images revealed hierarchical morphology and size, influenced by the types of precursors used. TEM images showed that samples A-15, A-2, A-3, B-6, and B-12 produced nanosized particles. EDX data showed the surface O/Mn ratios of the catalysts, ranked from highest to lowest as B-2 > B-6 > B-1 > B-10 > A-12 > A-3 > A-2 > A-8 > A-9 > A-15, with approximate values of 5.28, 4.66, 4.17, 3.80, 3.65, 2.51, 2.31, 1.68, 1.46, and 1.32, respectively. XPS data indicated the presence of Mn³⁺ and Mn²⁺, along with adsorbed oxygen (Oads), which are the main contributors to electron transfer in catalytic processes. The average oxidation states (AOS) of Mn from highest to lowest were A-15 > A-8 > A-3 > B-10 > A-2 > A-12 > B-6 > A-9, with respective values of 3.42, 3.36, 3.35, 3.32, 3.29, 3.39, 3.28, and 3.09. In the MB degradation test, the best precipitation-derived catalyst was A-12, synthesized from KMnO4 and oxalic acid, producing α-MnO2 with granular-fiber hierarchical structure, an average particle size of 187.3 nm, an O/Mn ratio of approximately 3.65, and a surface area of 19.90 m²/g. MB degradation performance at pH 1, 3, and 5 was >90%, dropping to ~50% at pH 7, and increasing again to 64% and >80% at pH 9 and 11, respectively. The optimal degradation time was 60 minutes. The best catalyst from the solvothermal method was A-9, synthesized using KMnO4, ethanol, and NaOH, producing Mn2O3 with a rod-cube hierarchical structure, an average particle size of 1119.2 nm, an O/Mn ratio of about 1.46, and a surface area of 5.69 m²/g. MB degradation was >95% at pH 1 and 3, slightly decreasing to 80–90% at pH 5, 7, 9, and 11. The optimal degradation time was 30 minutes. The best overall catalyst, synthesized via the microwave-solvothermal method, was sample B-6, made from KMnO4, methanol, and HCl. It yielded α-MnO2 with a fibrous structure, an average particle size of 531.1 nm, an O/Mn ratio of approximately 4.65, and a surface area of 27.89 m²/g. MB degradation exceeded 98% at pH 1 and 3, slightly decreased to around 70% at pH 5 and 7, and increased again to above 80% at pH 9 and 11. The optimal degradation time was 30 minutes. Catalyst B-6 demonstrated consistently high and stable degradation performance, maintaining >93% efficiency up to the fifth cycle, which was not observed in other catalysts.

Keywords: Manganese oxide, degradation, methylene blue (MB) 

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Ketersediaan

Informasi Detail

Judul Seri

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No. Panggil

1710346337

Penerbit

Pekanbaru : Universitas Riau PASCASARJANA S3 Ilmu Kimia., 2025

Deskripsi Fisik

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Bahasa

Indonesia

ISBN/ISSN

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Klasifikasi

1710346337

Tipe Isi

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Tipe Media

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Tipe Pembawa

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Edisi

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Subjek

DISERTASI S3 ILMU KIMIA

Info Detail Spesifik

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Pernyataan Tanggungjawab

ERA

Versi lain/terkait

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